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Research in the field of veterinary entomology is dominated by studies concerning arthropods that affect animal health. In 2019, this research primarily addressed the overwhelming industry need to manage detrimental species such as biting flies and ticks and the ongoing problems caused by insecticide/acaricide resistance evolution in these pests. Research also included evidence supporting the need for the conservation of beneficial species, such as biological control organisms. Many studies in a variety of pest systems have demonstrated the potential detrimental effects of insecticide use on nontarget organisms, and those of veterinary importance are no exception. An emphasis also was placed on research regarding alternative management strategies for veterinary pests. The presentation herein provides a descriptive summary of selected research that contributed greatly to the body of knowledge regarding arthropods of veterinary importance. This included several studies that will pave the way towards more effective veterinary pest management in an effort to improve animal health and welfare and, therefore, the sustainability of animal agriculture.
Urban insect pests such as ants, termites, cockroaches, and bed bugs are more than just nuisances; they often negatively impact structures, landscapes, animal health, commercial food production, food safety, and public health (mental, physical, and financial). Due to the tremendous burden these insects can inflict, researchers, manufacturers, and pest management professionals work to create solutions that effectively manage urban and structural pests. One solution that has proven useful in agriculture is the development of an integrated pest management (IPM) plan; i.e., a science-based approach to pest control that utilizes multiple tactics such as preventative tools, chemical control (sprays, fumigation, and baits), biological control, and exclusion. There are many permutations of urban IPM plans, but in general they consist of five components: 1) identifying the pest, 2) monitoring the pest, 3) developing an intervention plan (including prevention and control techniques), 4) implementing the program, and 5) recording and evaluating the results. The objectives of the current publication were to 1) highlight urban entomology research published in 2019 and 2) show how the results from these publications help pest management professionals create and implement IPM plans.
The 2019 Entomological Society of America annual meeting was held in St. Louis, Missouri, just blocks away from the iconic Gateway Arch. Representing a ‘gateway to the West’, this inspired the theme of the Highlights in Medical Entomology to reflect on the accomplishments of the past year as we move into a ‘new frontier' of vector biology research. Papers were selected broadly across arthropods that influence public health, focusing on topics ranging from West Nile virus transmission, ticks and tick-borne disease, to advances in genetics and ‘big data’ studies. This included current perspectives on West Nile virus ecology and epidemiology, which has now been endemic in the United States for 20 yr. Additional topics such as the advantages of citizen science and the importance of scientific communication were also discussed. Together, these papers demonstrate the achievements of the vector community while emphasizing the challenges that we collectively face to reduce the burden of vector-borne disease.
Mite biodiversity and distribution in Malaysia is currently understudied. Most previous works on Malaysian Acari have focused on pest organisms of medical, veterinary, and agricultural concern, with a few recent studies centered on mites in forensic contexts. Previous literatures have targeted collection sites in forest reserves and/or mountains in either Peninsular or Malaysian Borneo, though the state of Sarawak had the least publications related to mite species descriptions despite having the highest number of nature parks of any state in the country. Most publications focused on the three states Selangor, Pahang and Sabah. Most of the mite species reported were from mammals (66.3%), with fewer species from birds (21.7%), arthropods (11.2%), and reptiles (0.8%). We believe that further work on the systematic documentation of mite species throughout Malaysia is necessary as it could generate useful tools, such as the use of mites as biogeographical markers or as forensic indicators. Therefore, this review catalogs mite species that have been documented in or on animal hosts in Malaysia and serves as a foundation for future work.
Chrysomya megacephala (Fabricius, 1794) is a vector of enteric bacteria, protozoa, helminths, and viruses. These Diptera can also be responsible for secondary myiasis in several animal species. Therefore, it is easy to understand the relevance of studies focusing on C. megacephala dissemination control. The employment of essential oils as natural insecticides must be considered as a promising alternative for the replacement of synthetic insecticides. In this context, the essential oil obtained from Chilean boldo leaves should be highlighted. The aim of the present work was to assess the insecticidal activity of Chilean boldo essential oil against C. megacephala blowflies in different life stages (larva, pupa, and adult). The essential oils were extracted from commercial samples of Chilean boldo leaves by hydrodistillation and were mixed to produce a pool that was employed in the study. Gas chromatographic techniques were used to enable the identification and quantification of the pool's components. Larvae, pupae, and adult insects of C. megacephala were exposed (topical application) to different concentrations of this essential oil pool. After that, the larvicidal, pupicidal, and insecticidal actions of the oil were tested. Its toxicity might be associated with compounds such as eucalyptol, linalool, α-pinene, limonene, and ascaridole, either acting alone or by synergic effects. Interestingly, the pupae appeared to be stronger than the larvae and adult insects, needing higher doses of essential oil to be killed. The oil's toxic effects could be useful to control C. megacephala dissemination in all of its development phases.
Forensic entomologists usually estimate the minimum postmortem interval (PMImin) using the time required for the oldest immature insects found on the corpse to grow to its development stage and age at the time of discovery. The sheep blow fly Lucilia sericata (Meigen, 1826) is a carrion fly found nearly worldwide, and important in forensics. We studied the development time of L. sericata from egg to adult at constant temperatures of 16, 19, 22, 25, 28, 31, and 34°C, and found that the times required are 913.2 ± 19.4, 588.8 ± 35.8, 459.8 ± 15.2, 373.2 ± 15.3, 308.0 ± 9.7, 272.5 ± 9.2, and 267.5 ± 10.5 h, respectively. We established three development models to infer the age of the immature insect: isomegalen diagram, isomorphen diagram, and thermal summation model. In addition, a regression analysis was performed on the relationship between body length and total development time from hatching to dispersing. The thermal summation constant during the development of L. sericata is 6023.2 degree hours and development threshold temperature is 9.19°C. The results of this experiment provide a basis for the use of L. sericata in the estimation of PMImin.
Estimation of the time of colonization (TOC) is often based on laboratory studies that document arthropod development. Precise data for forensically important species, such as blow flies (Diptera: Calliphoridae), are essential for accuracy in the estimate of TOC. Calliphorid development is a quantitative trait and thus depends on a host of variables. In calliphorids, studies showed photoperiod can play a role in development. However, there has been little research to date on the effects of photoperiod, and available data indicate the impact is species-specific. In this study, the effects of photoperiod on the development of Chrysomya rufifacies (Macquart), were examined. Chrysomya rufifacies is a fly of great medical and legal importance and is often encountered on vertebrate remains in temperate and tropic regions throughout the world, including North and Central America, Asia, and Australia. Larvae were reared under light regimes of 12, 16, and 24 h of light at 28.5 ± 0.0°C, 86.2 ± 0.3 RH. Minimum development time for each stage did not differ significantly for the applied photoperiods, nor were there significant differences in total minimum postembryonic development time. Photoperiod did not significantly affect larval size or growth rate. The data suggest that light durations investigated in this study do not influence the development of C. rufifacies. This indicates that photoperiod may not be a concern for forensic entomologists in Texas, United States, or other areas with similar conditions when estimating the TOC for this species. Validation efforts are encouraged to verify this conclusion.
Chagas disease is one of the most important vector-borne diseases in Latin America, including Mexico. Recently, autochthonous cases have also been detected in the United States of America. It is suspected that two subspecies of Triatoma rubida (Uhler), T. r. sonoriana (Usinger) and T. r. uhleri (Usinger), considered efficient vectors of Trypanosoma cruzi Chagas in Mexico, could interbreed and potentially generate offspring with superior biological characteristics. In this study, the biological parameters of T. r. sonoriana, T. r. uhleri and their laboratory hybrids were evaluated. Hybrids of the two subspecies surpassed both parental subspecies, T. r. sonoriana and T. r. uhleri, in three (numbers of required blood meals to molt [16–20], feeding [10.5–17 min] and defecation times [˂>1 min post-feeding]) of nine studied biological parameters. Moreover, the hybrids surpassed T. r. uhleri in two additional parameters, development time (298 d) and mortality (39–42%). Both the hybrid and the two parental cohorts had comparable results in the remaining four (onset of feeding, number of obtained females, number of eggs laid, and eclosion rate) of nine studied parameters. Thus, we conclude that hybrid vigor could result in an increased risk of T. cruzi transmission to humans and animals.
Graphical Abstract
Studied parameters lead to estimate an increase on risk of transmission of T. cruzi in the overlapping areas of the two studied subspecies of Triatoma rubida
Despite the fact that necrophagous flies are known to alter bloodstains and create unique artifacts, no research has occurred to date that has examined the characteristics of insect stains on textiles or fabrics. This study represents the first effort to characterize artifacts produced by adult Calliphora vicina Robineau-Desvoidy deposited on a range of shirt fabrics that varied in type, color, orientation, and yarn tension. In general, artifact morphology on any type of fabric was distorted in comparison to those observed on smooth and/or nonporous surfaces in previous studies. Consequently, distinction of artifact type could only be made broadly as digestive artifacts and transfer patterns, in which the latter was predominantly detected as tarsal tracks. None of the artifacts displayed satellite stains typical of human bloodstains found on textiles. Wicking was evident on all fabrics but was most pronounced with dri wick and jersey knit polyester in comparison to cotton knit. Digestive artifacts on any colored fabric, but especially with green and yellow shirt samples, resembled the reported color, size, and morphology of bloodstains generated in laboratory studies on a range of fabrics. Unique digestive artifacts were also detected as small, black, and nearly spherical. These defecatory stains did not appear to wet or wick into any of the fabrics. Digestive artifacts and tarsal tracks differentially interacted with front face stitch loops of clothing fabrics to yield distinct stain patterns. The implications of these observations in reference to bloodstain pattern analysis at crime scenes are discussed.
Forensic entomology is a well-established tool for evaluating the death, or abuse, of a person. Insect evidence provides valuable information as related to time of colonization and movement of remains from one location to another. Blow flies (Diptera: Calliphoridae) are commonly found on human remains throughout most stages of decomposition, and when entomological evidence is collected these taxa tend to be the most numerous. However, very few crime laboratories across the country have collection and rearing protocols for these forensically important insects. A lack of knowledge in collection techniques and limited access to an appropriate food source are the main reasons for absence in adequate collection and rearing protocols. Thus, when crime scene investigators or pathologists collect insects, they are often mishandled (e.g., placed into containers with no air holes, no food, or a food source that is not sustainable for their development). To address this issue, we analyzed easily accessible and cost-efficient alternative food sources for blow flies; specifically, tuna and wet cat food compared to beef liver (control). Survivorship and development were examined for each food source using the blow flies Phormia regina (Meigen) (Diptera: Calliphoridae) and Cochliomyia macellaria (Fabricus) (Diptera: Calliphoridae). These findings provide an overview of possible alternatives that could be used as a sustainable food source in crime laboratories when immediate action from a forensic entomologist cannot be obtained.
After death, a series of primary reactions occur that produce volatile organic compounds (VOCs) that are released into the environment. In this study, we investigated if the succession of flies of forensic importance in the first hours after death is mediated by VOCs in order to better understanding of the ecology of necrophagous insects. In total, 685 adult insects (Diptera and Hymenoptera) were collected by traps baited with chicken remains at different decomposition times (0, 6, 12, 24, 36, or 48 h). Of the total of insects caught, individuals from six families of Diptera can be cataloged of forensic importance. The most abundant dipteran family was Piophilidae with 213 individuals, followed by Calliphoridae with 178 specimens. Of the total flies caught, 90% were females and the rest were males. Most of the caught females were categorized as gravid, which visited more often the decaying tissues compared to nongravid females. The abundance of the flies increased in the remains with a longer time of decomposition. Six VOCs emitted in different relative quantities were identified according to the decomposition time of the remains. An apparent association was observed between the emission of ρ-cresol with Lucilia eximia (Wiedemann), between the emission of phenol, dimethyl disulfide, and dimethyl trisulfide with Chrysomya rufifacies (Macquart), and between the emissions of indole with Cochliomyia macellaria (Fabricius).
Luz Alejandra Castillo-Alanis, Ana Edith González-Hernández, Alejandra Quijano-Mateos, Carlos Salvador Pedraza-Lara, Alexa Villavicencio-Queijeiro, María Elena Bravo-Gómez
One of the problems faced by entomotoxicological studies is the large variability of experimental set-ups and the absence of harmonized protocols to compare the data and results obtained by different research groups. Among the wide range of influencing factors on the development and growth of insects, food substrates are remarkably relevant. This article proposes a standardized growth medium to be employed in future entomotoxicological studies on the scuttle fly Megaselia scalaris (Loew, 1866), (Diptera: Phoridae). This species plays an important role in forensic cases related to the decomposition of human remains found indoors and/or in concealed environments, because of their small size and ability to enter these locations at an earlier time than many other insects. Because of these traits, it can be used for the estimation of the minimum postmortem interval (mPMI). We achieved the formulation of a medium that overcomes two traditional disadvantages of culture media used to raise necrophagous Diptera, the unknown media composition and different growth rates from those reared in tissue. The proposed medium is a known composition formulation, free of xenobiotics, in which M. scalaris shows growth rates and development times similar to those obtained when it is reared in tissue. This new diet might be used in future studies to test the effect of substances of forensic interest (prescription or illicit drugs, poisons, etc.) on the larval development time, helping to adjust the estimation of mPMI based on the presence of such substances. Additionally, the formulation revealed some interesting data about nutritional requirements of this species.
The species composition, distribution, and bionomics of sand flies was investigated from January to December 2017 in four tehsils (20 villages) of district Bajaur (formally Bajaur agency), Khyber Pakhtunkhwa, Pakistan. In total, 4,173 adult specimens comprising of seven species of Phlebotomus (Diptera: Psychodidae) and three species of Sergentomyia (Diptera: Psychodidae) were collected by oral aspirator, insecticide spray, and sticky traps from June to October. Highest numbers of flies were collected indoors in July and August when relative humidity and temperature were highest. Phlebotomus sergenti Parrot (Diptera: Psychodidae) was the most abundant species from all the collection sites, making approximately 70% of the total capture. Combined dwellings and chicken cages harbored the highest number of adult and immature flies (unrotated external genitalia). Abundance of P. sergenti had a significant (P ≤ 0.05) positive correlation with monthly average temperature, relative humidity, and average rainfall in indoor collections. On the other hand, P. papatasi Scopoli displayed similar correlation in the indoor and nighttime collections. Both the species were apparently abundant in the elevation range ≤ 419 m above sea level and on rangelands. Phlebotomus papatasi, however, also occurred on agricultural lands. The number of cutaneous leishmaniasis (CL) cases did not significantly correlate with the abundance of sand fly vectors across the villages surveyed. The results reported herein can serve as a baseline for an all-extensive future work in Bajaur. Our investigations will benefit the public health experts and medical entomologists for improved control and surveillance vectors of leishmaniasis.
Repeated exposure to insecticides, particularly pyrethroids and organophosphates, has resulted in the development of insecticide resistance in the mosquito Culex pipiens, a primary disease vector. Glutathione S-transferase (GST) is involved in the phase II detoxification of numerous xenobiotics, including insecticides. In this study, a GST gene (CPIJ002678) was amplified, sequenced, and used in comprehensive molecular analyses ending up in development of a rapid assay to distinguish more tolerant individuals from susceptible Culex pipiens using the Restriction Fragment Length Polymorphism (RFLP) technique. Field collected Culex pipiens strains from untreated areas, organophosphates-treated areas and a lab strain reared for many generations, all were used in CDC bottle bioassays to evaluate the susceptibility status of the studied individuals to malathion insecticide. Interestingly, both field sites collected groups showed high levels of resistance at the malathion diagnostic time. Gene amplification, and bidirectional direct sequencing results were analyzed. Compared with the reference genome sequence, the pairwise alignment of the amplified sequences showed 96.6% similarity to the reference sequence in the GenBank database. The confirmed gene sequences were assembled and aligned using various bioinformatic softwares. The assembled contigs were used in NEBcutter V2.0 for constructing restriction maps and checked for the availability of differences (if present) between susceptible and more tolerant strains. Specific molecular RFLP markers were successfully recognized to differentiate the more tolerant from the susceptible Culex pipiens phenotypes.
The ultrastructure of the mouthparts of Haematobia irritans (L.) was investigated by scanning electron microscopy. The morphological characteristics of the maxillary palps, labium (prementum and postmentum), labrum, hypopharynx, haustellum, and labellar lobes are described, as well as of the sensilla evidenced on all the surface of the mouthparts, and the set of different positions assumed by the mouth apparatus of this fly. Based on their morphology, 12 well-differentiated sensilla were identified, among three types of cuticular sensilla: trichoidea, coeloconica, and campaniformia. A slight sexual dimorphism in the sensilla patterns found in the mouthparts of H. irritans was evidenced. These observations are discussed with reference to the current literature on the functional morphology of sense organs of Insecta. These results could facilitate the recognition of the chemosensory sensilla by electrophysiological techniques, and foment future taxonomic and phylogenetic studies to better elucidate the evolution of Diptera, Muscomorpha.
Larvae of container-breeding mosquitoes develop in a wide range of container habitats found in residential neighborhoods. Different mosquito species may exhibit preference for different container types and sizes. Due to phenological differences, species composition in container habitats may change over time. We first conducted weekly neighborhood container surveys to determine the types of container habitats found in residential neighborhoods, and to determine mosquito species composition over time within these habitats. We then conducted an oviposition choice field assay to determine whether female mosquitoes of different species preferentially oviposit in different container types commonly found in neighborhoods. Halfway through the experiment, the largest container was removed at half the sites to test the hypothesis that incomplete source reduction alters oviposition preference among the remaining containers. In the neighborhood surveys, large containers had the greatest mosquito densities and the highest species richness. Aedes albopictus (Skuse), the most commonly collected mosquito, was found in all container types. The oviposition experiment indicated that Culex spp. females preferentially oviposit in large containers. When the largest container was removed, the total number of egg rafts decreased. Aedes spp. females preferred to oviposit in large- and medium-sized containers, but the total number of eggs laid did not change when the large container was removed. These results confirm that understanding habitat preferences of container-breeding mosquitoes is important to control efforts targeting vector species and that incomplete removal of container habitats may have unpredictable consequences for the distribution of juveniles among remaining habitats.
Sarcophagidae (Diptera) are of great interest from a veterinary, medical, and forensic viewpoint, and are potential bioindicators for environmental impact assessments. In this study, we evaluated changes in abundance, species richness, and diversity of flesh flies in different habitat types in the Humid Chaco ecoregion of South America: 1) anthropized habitats: urban, cattle farm, and alfalfa crop, and 2) natural habitats: savanna and forest.We hypothesized that sarcophagid fly community parameters are affected by the anthropization and that spatial turnover will contribute more to the overall beta diversity than nestedness between habitats. In each habitat, samplings were conducted monthly from March 2015 to February 2016 in 25 sites, 5 per habitat, totaling 300 independent samples at the end of the study. We collected 5,790 Sarcophagidae (55 species). Community parameters of Sarcophagidae were evaluated and compared. The ecological effects of anthropization and habitat type were observed in the present study. As expected, our results showed the highest abundance, species richness, and diversity in the savanna and forest habitats (natural), whereas the lowest values were registered in the urban and alfalfa crop habitats, supporting the hypotheses of anthropization as the main driver of diversity loss. In addition, sarcophagid assemblages differed between all habitats and the overall dissimilarity was structured by spatial turnover. The main conclusion of this research is that flesh fly community structure is greatly affected by anthropization and habitat type, and this would be related to canopy cover and microclimate conditions of each environment.
Environmental factors affect host-seeking behavior in ticks. In this study, 80 nymphal Amblyomma maculatum Koch were released in an observation arena containing four different heights of broomsedge stems (Andropogon virginicus L.) anchored in sand. Observations were made over three days as to proportion of ticks questing, questing height, and stem height distribution This scenario was replicated three times with different cohorts of ticks (n = 80 per replicate) for each of three treatment combinations of temperature and humidity: High temperature/high humidity (HTHH), high temperature/low humidity (HTLH), and low temperature/high humidity (LTHH). A fourth treatment utilizing the same size cohort and number of replicates included Wind (HTHHW+/–) by alternating days of wind and no-wind conditions over four days. Mean questing height for ticks under HTHH, HTLH, and LTHH conditions ranged from 4.45 to 6.03 cm with ticks questing significantly higher in HTHH. A significantly lower proportion ticks quested in HTLH (8.64%) than HTHH (14.06%) and LTHH (15.33%). In HTHH and LTHH, a significantly higher proportion of ticks were observed questing on 5-cm stems. Wind significantly reduced average questing height, and when absent, ticks on 20- and 30-cm stems quested significantly higher. These data indicate that A. macuatum nymphs randomly select stems to quest upon and climb upward until environmental conditions are prohibitive/ideal. Conditions with reduced vapor pressure deficit (VPD) led to higher questing frequency and height. Relatively low questing heights observed correspond with size of preferred hosts and may explain infrequency of collection by dragcloth in the field.
The spread of the Asian tiger mosquito, Aedes albopictus Skuse, throughout the United States has implications for the transmission potential of vector-borne diseases. We used a 30-yr data set of occurrence records in Illinois and developed a hierarchical Bayesian model to shed light on the patterns and processes involved in the introduction and expansion along the northern edge of the geographic range of this species. We also collected specimens from 10 locations and sequenced a segment of their mitochondrial COI genes to assess possible introduction sources and geographic patterns in genetic variation present within contemporary populations. We documented an increase in the number of observations throughout the southern and central parts of Illinois over the study period. The process through which this spread occurred is likely only partially due to local dispersal. The probability of successfully overwintering was likewise low, but both these parameters increased over the study period. This suggests that the presence of Ae. albopictus has been largely due to repeated introductions, but that in recent years populations may have become established and are leading to an increase in locally driven dispersal. There was considerable genetic diversity among populations in Illinois, with 13 distinct haplotypes present in 10 sampling locations, several of which matched haplotypes previously found to be present in locations such as Texas or Japan. Further research is needed to understand how the combination of continued propagule pressure and establishment of populations are driving the increase and expansion of this invasive mosquito along its northern distribution limit.
Mosquito control agencies monitor mosquito diversity and abundance through a variety of trap types. Although various long-term ecological data sets exist, little work has been done to address the sampling effort required to capture mosquito community diversity by trap type and few spatiotemporal distributions of vector species have been described. Here, we describe the seasonal distributions of vector species of importance, assess trapping effort needed to capture the diversity of the mosquito community, and use a partial redundancy analysis to identify trap bias from four commonly deployed adult mosquito traps in Volusia County, Florida. Collections were made with American Biophysics Corporation (ABC) light traps, Biogents Sentinel (BGS) traps, chicken coop exit traps, and gravid traps. We collected a total of 238,301 adult female mosquitoes belonging to 11 genera and 36 species, 12 of which we deemed to be vector species of epidemiological importance. We found that ABC traps not only yielded the greatest abundance and diversity but also captured several nonvector species. BGS and gravid traps yielded the highest proportions of vector species; exit traps recorded the lowest abundances and species richness. Wintertime abundances of several species demonstrated a need for year-round surveillance in the study area; partial redundancy analysis revealed that trap type explained a significant proportion of the variance in our data set, with certain vector species associated with specific trap types. Increased awareness regarding the amount of trapping effort needed to detect vector species diversity will help to optimize efforts in the field, leading to more effective resource allocation.
Graphical Abstract
Proportion of vector species of epidemiological importance from four commonly deployed adult mosquito traps in Volusia County, Florida, from 1 January 2015 to 31 December 2018.
Cutaneous (CL) and visceral (VL) forms of leishmaniasis, transmitted by sand flies, are seen in all countries located in Mediterranean Basin including Turkey. In this study, we aimed to conduct an entomological survey for the detection of sand fly fauna and vector species in Mersin province, one of the important endemic areas for CL in Turkey. In total, 912 sand fly specimens were collected in 2010 and 2011 using CDC light traps. Nine Phlebotomus (Diptera: Psychodidae) and three Sergentomyia (Diptera: Psychodidae) species were detected. Of the collected Phlebotomus sand flies, P. sergenti Parrot, 1917 (30.1%) was the most dominant followed by P. alexandri Sinton, 1928 (18.2%), P. neglectus/syriacus Tonnoir Adler (12.0%), P. tobbi Adler & Theodor, 1930 (11.7%), and P. papatasi Scopoli, 1786 (10.2%), while S. minuta Rondani, 1843 (11.3%) was the dominant species among Sergentomyia. During the field work in 2011, female specimens (n = 81) were screened for the presence of Leishmania promastigotes by midgut dissection, and all were found negative. The rest of the collected female specimens (n = 334) were pooled according to species (P. alexandri, P. neglectus/syriacus, P. papatasi, P. sergenti, P. simici, and P. tobbi) and location (Mut, Silifke, and Anamur). In total, 29 pools were generated and real-time ITS1 PCR assay was performed to detect and identify natural Leishmania Ross, 1903 (Kinetoplastida: Trypanosomatida) infection. Two pools, both from Mut town, containing P. sergenti specimens were found positive and Leishmania tropica Ross, 1903 was identified as an infectious agent for both pools. In conclusion, the sand fly fauna was determined in an endemic area for CL. The detection of L. tropica DNA in P. sergenti specimens showed the possible vectorial role of this species in Mersin province.
Ixodids suck blood from host animals and transmit pathogens that cause important medical and veterinary diseases. As synthetic conventional acaricide resistance becomes increasingly common, alternative tactics are likely to enhance control efforts. Laboratory bioassays assessed the lethality of CimeXa, a commercial silica gel desiccant dust, and EcoVia, a commercial product containing silica gel + thyme oil, against lone star tick, Amblyomma americanum (L.), larvae and nymphs. Both life stages were completely killed by CimeXa by 24 h, and EcoVia achieved total larval mortality within 1 h when they were initially immersed in the dusts and when they crawled across treated substrate. Larvae were killed faster than nymphs. Temporary immersion of A. americanum larvae and nymphs in aqueous suspensions of the dusts were less effective than exposure to the dusts applied dry. Larval and nymphal mortality associated with crawling on dried aqueous suspensions of the products was also not as strong as when the immature life stages crawled across substrate treated with dry dusts, and EcoVia was not more efficient than CimeXa. CimeXa and EcoVia can likely be used to protect cattle in a prophylactic context because silica gel does not degrade, and EcoVia might be effective at eliminating ticks that are feeding on cattle as well. We suggest that the two dust products be assessed for efficacy against other ixodid species, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), which transmits the causal agents of babesiosis to cattle.
Insecticide-impregnated traps and visual targets are used for tsetse (Diptera, Glossinidae) population control. Such devices are made with textiles and deltamethrin is frequently the insecticide of choice. However, persistence of an insecticide on textiles is affected by exposure to weather. Here we examine the effect of weathering on the capacity of four textiles with increasing proportions of polyester (0, 35, 65, and 100%) with cotton and viscose to retain deltamethrin. Textiles tested were those used to make visual targets in a pan-African program to maximize target efficiency for controlling tsetse vectors of African trypanosomiasis. Following impregnation in an aqueous suspension of deltamethrin at 1,000 mg/m2, textiles were weathered for 18 mo at Lambwe Valley, Kenya and sampled every 3 mo to make knockdown tests on the tsetse fly Glossina pallidipes Austen. Deltamethrin content of the textiles was established using gas chromatography mass-spectrometry at impregnation and after 9 mo of weathering. Textiles with higher proportions of polyester retained deltamethrin better: respectively, 100% polyester and 65:35 polyester/ viscose textiles retained deltamethrin at 17 and 11 mg/m2 9-mo post-treatment that caused 100% knockdown in G. pallidipes after 1 h, and killed 67 and 47% of flies, respectively, after 24 h. Eighteen-month weathered 100% polyester treated textile still knocked down all tsetse exposed to it within 2 h. The LD50 for deltamethrin on filter paper for G. pallidipes was estimated at 28.8 mg/m2, indicating that deltamethrin is more available on polyester to kill tsetse.
Tick-borne diseases are a growing threat to public health in the United States, especially among outdoor workers who experience high occupational exposure to ticks. Long-lasting permethrin-impregnated clothing has demonstrated high initial protection against bites from blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), in laboratory settings, and sustained protection against bites from the lone star tick, Amblyomma americanum (L.) (Acari: Ixodidae), in field tests. However, long-lasting permethrin impregnation of clothing has not been field tested among outdoor workers who are frequently exposed to blacklegged ticks. We conducted a 2-yr randomized, placebo-controlled, double-blinded trial among 82 outdoor workers in Rhode Island and southern Massachusetts. Participants in the treatment arm wore factory-impregnated permethrin clothing, and the control group wore sham-treated clothing. Outdoor working hours, tick encounters, and bites were recorded weekly to assess protective effectiveness of long-lasting permethrin-impregnated garments. Factory-impregnated clothing significantly reduced tick bites by 65% in the first study year and by 50% in the second year for a 2-yr protective effect of 58%. No significant difference in other tick bite prevention method utilization occurred between treatment and control groups, and no treatment-related adverse outcomes were reported. Factory permethrin impregnation of clothing is safe and effective for the prevention of tick bites among outdoor workers whose primary exposure is to blacklegged ticks in the northeastern United States.
Aedes aegypti (L.) is an important vector of viruses causing dengue, Zika, chikungunya, and yellow fever and as such presents a serious threat to public health in tropical regions. Control programs involving ‘rear and release’ of modified male Ae. aegypti are underway and require effective trapping methods for surveillance of both the released insects and the impacted wild mosquito population. The BG-Sentinel trap (BGS) is widely used in Ae. aegypti surveillance but its level of efficiency, that is, what proportion of the mosquitoes encountering the trap are captured, is unknown. This is especially true for male mosquitoes, the behavior of which is incompletely understood. We tested the efficiency of two versions of the BGS for capturing male Ae. aegypti under semifield conditions with and without CO2 and a human skin odor mimic lure and with these baits combined. A navy-blue BGS trap emitting CO2 and a human skin odor mimic captured 18% of the released male Ae. aegypti, with a capture efficiency of 9 % (of the total encounters with the trap). Male Ae. aegypti had multiple encounters with the BGS that did not result in capture; they crossed over the trap entrance without being captured or landed on the sides of the trap. Swarming behavior around the BGS was also recorded, even when only a visual cue was present. Understanding male Ae. aegypti behaviors during an encounter with the BGS can inform improvement of trap design and therefore capture efficiency for surveillance in control programs.
Resistance to insecticides used to control mosquito vectors threatens the ability of mosquito-control organizations to protect public health. Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) are invasive species widely distributed throughout Florida and have been implicated in recent epidemics of Zika, dengue, and chikungunya viruses. Knowledge of the susceptibility status of these mosquito species to pyrethroid and organophosphate active ingredients (AIs) is needed to inform product selection and treatment decisions. The susceptibility of 37 Ae. aegypti and 42 Ae. albopictus populations from Florida was assessed in response to six pyrethroid and three organophosphate AIs using the CDC bottle bioassay method. Of all bioassays completed with a pyrethroid AI, 95% for Ae. aegypti and 30% for Ae. albopictus resulted in a resistant outcome. For organophosphate AIs, ∼31% of assays conducted for both species were classified as resistant. The highest frequency of susceptibility for both species was observed in response to the organophosphate AI, naled. Lambda-cyhalothrin was the only pyrethroid to result in a susceptible status for Ae. aegypti and also had the highest frequency of susceptibility for Ae. albopictus. Resistance was detected to every AI tested for both Ae. aegypti and Ae. albopictus, but there was a pronounced trend of pyrethroid resistance in Florida populations of Ae. aegypti. The results of this work provide evidence for the need to decrease reliance on pyrethroids and to implement different methods of control of Ae. aegypti in Florida.
For the indoor and outdoor pest controls, various types of insecticide formulations are available including aerosols, sprays, electric vaporizers, mosquito coils, and traps. In the present study, the insecticidal activity of aerosols, the most commonly used formulation of household insecticides for mosquito control, against Aedes albopictus (Skuse) was assessed using seven commercial products and some attributes which can affect the efficacy of aerosol were investigated as well. The products had difference in their chemical composition of active ingredients, propellant/liquid phase ratios, solvent types, and nozzle orifice sizes, and these characteristics seem to affect the overall insecticidal activity. In general, solvent type dominantly determined the insecticidal activity, where four products in oil-based solvent system showed greater mortality (97.5% in average) than water-based aerosols (38.3% in average) against the mosquitoes located at the far side of the test chamber. The contribution of solvent type and nozzle orifice size were further examined with the sample aerosols, and the orifice size were determined more influential to the spray distance. Regardless of solvent types, the sample products attached to a bigger actuator (0.96 mm in diameter) showed greater knock-down activity (>98%) than the smaller ones (0.48 mm, 62.5% in average) to the back panel in the chamber. On the other hand, solvent system significantly affected the residual activity, as the oil-based and water-based aerosols showed 2.3- and 4.8-fold decrease in KT50 values, respectively, between 1 and 10 min after the spray.
In recent decades, the occurrence and distribution of arboviral diseases transmitted by Aedes aegypti mosquitoes has increased. In a new control strategy, populations of mosquitoes infected with Wolbachia are being released to replace existing populations and suppress arboviral disease transmission. The success of this strategy can be affected by high temperature exposure, but the impact of low temperatures on Wolbachia-infected Ae. aegypti is unclear, even though low temperatures restrict the abundance and distribution of this species. In this study, we considered low temperature cycles relevant to the spring season that are close to the distribution limits of Ae. aegypti, and tested the effects of these temperature cycles on Ae. aegypti, Wolbachia strains wMel and wAlbB, and Wolbachia phage WO. Low temperatures influenced Ae. aegypti life-history traits, including pupation, adult eclosion, and fertility. The Wolbachia-infected mosquitoes, especially wAlbB, performed better than uninfected mosquitoes. Temperature shift experiments revealed that low temperature effects on life history and Wolbachia density depended on the life stage of exposure. Wolbachia density was suppressed at low temperatures but densities recovered with adult age. In wMel Wolbachia there were no low temperature effects specific to Wolbachia phage WO. The findings suggest that Wolbachia-infected Ae. aegypti are not adversely affected by low temperatures, indicating that the Wolbachia replacement strategy is suitable for areas experiencing cool temperatures seasonally.
With increasing development of resistance to conventional synthetic acaricides in economically and medically important ixodid species, interest in finding alternative control tactics has intensified. Laboratory bioassays were conducted, using the lone star tick, Amblyomma americanum (L.), as a model species, to assess the efficacy of a diatomaceous earth-based product, Deadzone, in comparison with a silica gel-based product, CimeXa. CimeXa is already known to be highly lethal against A. americanum larvae and nymphs. The two dust treatments were 100% effective against larvae and nymphs within 24 h after contact occurred by immersion in dry dusts and after crawling across a surface treated with the dry dusts. Contact by crawling on a dried aqueous film of the dusts, even at a concentration of 10%, was not as effective as exposure to the dusts in dry powder form. As has been demonstrated with CimeXa, it is likely that Deadzone will be capable of providing prophylactic protection of cattle from economically important one-host ixodids, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), which vectors the causal agents of babesiosis. Diatomaceous earth can be stored indefinitely, will remain efficacious for as long as sufficient quantities remain on the substrate, it is a natural (organic) substance, and it might be amenable for limited use in environmentally protected habitats.
Rickettsia parkeri, a tick-borne pathogen distributed throughout several countries of the Americas, causes a mild to moderately severe, eschar-associated spotted fever rickettsiosis. Although most U.S. cases of R. parkeri rickettsiosis are reported from southeastern states, some have been reported recently from remote regions of southern Arizona. These cases are linked to R. parkeri-infected ticks of the Amblyomma maculatum (Acari: Ixodidae) group found in several isolated mountain ranges of southern Arizona and New Mexico, referred to as ‘sky islands'. Archival records also document ticks of the A. maculatum group collected from domestic and wild animals in West Texas. We surveyed sites in two sky island chains of Jeff Davis and Brewster counties to document the off-host occurrence of these ticks and identify the presence of R. parkeri in the Trans-Pecos region of Texas. During August 2019, 43 adult A. maculatum group ticks were flagged from vegetation or removed from a road-killed, female mule deer. Of 39 samples evaluated by PCR, eight contained a partial sca0 sequence with complete identity to R. parkeri and two with complete identity to ‘Candidatus Rickettsia andeanae’, a species of undetermined pathogenicity. Four isolates of R. parkeri were obtained using cell culture. Persons at risk for R. parkeri rickettsiosis include those who work or recreate in these mountains, such as hikers, backpackers, research scientists, foresters, and border enforcement personnel. Additional investigations are needed to define the distribution of these medically important arthropods in other parts of the southwestern United States and northern Mexico.
Aedes albopictus (Skuse), an invasive disease vector, poses a nuisance and public health threat to communities in the Northeastern United States. Climate change and ongoing adaptation are leading to range expansion of this mosquito into upstate New York and other northeastern states. Organized mosquito control can suppress populations, but it is time consuming, costly, and difficult as Ae. albopictus oviposits in small, artificial, water-holding containers. Unmanned aerial vehicles (UAVs), with centimeter-resolution imaging capabilities, can aid surveillance efforts. In this work, we show that a convolutional neural network trained on images from a UAV is able to detect Ae. albopictus habitat in suburban communities, and the number of containers successfully imaged by UAV predicted the number of containers positive for mosquito larvae per home. The neural network was able to identify some, but not all, potential habitat, with up to 67% precision and 40% recall, and can classify whole properties as positive or negative for larvae 80% of the time. This combined approach of UAV imaging and neutral network analysis has the potential to dramatically increase capacity for surveillance, increasing the reach and reducing the time necessary for conventional on-the-ground surveillance methods.
Tick-borne disease surveillance in North America has long focused on Lyme disease, though there is currently a significant shift towards comprehensive pathogen surveillance in ticks. Central California has often been overlooked in regular tick-borne pathogen surveillance despite the presence of numerous medically important tick species. The bacterial genus Rickettsia contains tick-borne species that are known pathogens, such as those in the spotted fever group; nonpathogenic endosymbionts; and many species with unknown pathogenic potential. Five common tick species (Ixodes pacificus Cooley and Kohls [Acari: Ixodidae], Dermacentor occidentalis Marx [Acari: Ixodidae], D. variabilis Say, Rhipicephalus sanguineus Latreille [Acari: Ixodidae], and Ornithodoros parkeri Cooley [Acari: Argasidae]) of California were collected by both traditional and modern techniques, and subsequently screened for Rickettsia spp. Many individuals from all five tick species were PCR positive for Rickettsia spp., and a combination of species-specific primers, a restriction fragment length polymorphism assay, and DNA sequencing was used to further characterize the species composition in these ticks. Probable Rickettsia philipii (Rickettsia 364D) was detected in one (1.56%) D. occidentalis collected in Fresno County; R. rhipicephali was detected in 23.4% of D. occidentalis from Fresno Co.; R. bellii was detected in 88.2% of D. variabilis, 7.8% of D. occidentalis, and in one R. rhipicephalus (1.1%) from Fresno Co.; R. monacensis str. Humboldt was detected in three (100%) of I. pacificus collected in both Fresno and Madera Co.; and an uncharacterized Rickettsia was detected in (26.4%) of O. parkeri collected in both Fresno and Madera Co. The findings in this study highlight the need for ongoing surveillance in this region of California.
Eastern equine encephalitis virus (EEEV), an Alphavirus from family Togaviridae, is a highly pathogenic arbovirus affecting the eastern United States, especially Florida. Effects of the Southern Oscillation Index (SOI), precipitation, and cooling degree days on EEEV horse case data in Florida from 2004 to 2018 were modeled using distributed lag nonlinear models (DLNMs). The analysis was conducted at statewide and regional scales. DLNMs were used to model potential delayed effects of the covariates on monthly counts of horse cases. Both models confirmed a seasonal trend in EEEV transmission and found that precipitation, cooling degree days, and the SOI were all predictors of monthly numbers of horse cases. EEEV activity in horses was associated with higher amounts of rainfall during the month of transmission at the statewide scale, as well as the prior 3 mo at the regional scale, fewer cooling degree days during the month of transmission and the preceding 3 mo and high SOI values during the month and the previous 2 mo, and SOI values in the prior 2 to 8 mo. Horse cases were lower during El Niño winters but higher during the following summer, while La Niña winters were associated with higher numbers of cases and fewer during the following summer. At the regional scale, extremely low levels of precipitation were associated with a suppression of EEEV cases for 3 mo. Given the periodicity and potential predictability of El Niño Southern Oscillation (ENSO) cycles, precipitation, and temperature, these results may provide a method for predicting EEEV risk potential in Florida.
West Nile virus (family Flaviviridae, genus Flavivirus) first caused human and veterinary disease, and was isolated from Culex pipiens pipiens L. and Aedes vexans (Meigen) (Diptera: Culicidae) in the United States in 1999. We report that a Connecticut strain of Ae. vexans was competent to transmit West Nile virus both horizontally to suckling mice and vertically to its progeny in the laboratory. Horizontal transmission was first observed on day 6 post-exposure (pe). Daily horizontal transmission rates generally increased with the day post-virus exposure with highest rates of 67–100% recorded on days 28–30 pe. One female vertically transmitted West Nile virus on day 21 pe, but only after it had taken its third bloodmeal. Horizontal and vertical transmission may contribute to West Nile virus infection rates in Ae. vexans in summer, and vertical transmission provides a means of survival of West Nile virus during winter.
Studies related to ants found in hospital environments have aroused interest in their role as mechanical vectors of pathogenic microorganisms. The objective of the current research was to determine the species composition and bacterial contamination of ant species found in a public hospital in the eastern Amazonian region. Ants were captured using bait containing honey and sterilized sardines in 15 locations within the Macapá Emergency Hospital, Amapá. Ants were identified morphologically using specific keys. Bacteria were first inoculed in a Brain Heart Infusion broth and then plated on 5% Agar with blood or MacConkey media. Bacterial species were identified through biochemical procedures. In total, 9,687 ants were collected, with 69.8% from the dry season and 30.2% from the rainy season. Nine species of ants were identified belonging to three subfamilies: the Monomorium pharaonis (Linnaeus 1758) being the most common, comprising 39.2% of the total specimens. Only one ant species was found in each bait, facilitating microbiological analyses. In total, 92 bacteria isolates were identified comprising 12 species. Pseudomonas aeruginosa Schroeter 1872 (Pseudomonadales: Pseudomonadaceae) was pathogenic bacteria, most frequently isolated, comprising 10.9% of the positive samples. The most contaminated ant in the study was M. pharaonis with 38.3%. It was the dominant ant species in this hospital environment. Its wide prevalence, forage day and night of this vector in hospital facilitated bacterial contamination. The presence of bacteria on ants may be associated with the dissemination of pathogens which cause hospital infections, making pest control a necessity in these institutions.
The mosquito Culiseta melanura (Coquillett) is the primary enzootic vector of eastern equine encephalitis virus (EEEV), a zoonotic Alphavirus endemic to eastern North America. In its northern range, Cs. melanura is considered a strict avian biter, transmitting EEEV among susceptible birds in a cycle of enzootic amplification. In its southern range, however, Cs. melanura is more general in host use, feeding heavily upon birds but also reptiles and mammals. The goal of this study was to better understand how host use of Cs. melanura changes throughout the year in Florida, where year-round EEEV transmission is observed. Mosquitoes were sampled in 2018 from nine sites across three central Florida counties. In total, 213 Cs. melanura bloodmeals were identified by PCR consisting of 39 species of birds, reptiles, and mammals. Avian bloodmeals were prominent throughout the year (range = 30–85%), and songbirds were a large portion of identified bloodmeals (37.1%). Reptiles surpassed birds only in spring (April–June), and brown anole (Anolis sagrei Duméril and Bibron, 1837 [Reptilia: Dactyloidae]) was the most commonly detected single host species (22.1% overall). Mammalian bloodmeals were mainly observed in summer, with humans being the most fed on mammal (12.7% overall). This study reveals that in southern foci of EEEV transmission, Cs. melanura host use varies throughout the year with reptiles providing the majority of blood meals in spring (51.3%), and birds are fed on more than other host groups during all other seasons (50.6–70.1%). In addition, feeding on mammals increases during summer months, which may implicate Cs. melanura in epizootic transmission in Florida.
The invasive Asian longhorned tick, Haemaphysalis longicornis Neumann, was first detected in the United States in 2017. It has since been found in 12 states, and there is concern that the tick's parthenogenetic ability and wide variety of host species may allow for broader dissemination. Of the tick-borne diseases endemic to the United States, Rocky Mountain spotted fever (RMSF), a rapidly progressive and potentially fatal disease caused by Rickettsia rickettsii, is the most severe. There is considerable geographical overlap between spotted fever rickettsioses cases, which include RMSF, and the currently known distribution of H. longicornis, providing the potential for this tick to encounter this pathogen. We have evaluated the ability of H. longicornis to acquire and transmit R. rickettsii under laboratory conditions. Haemaphysalis longicornis as larvae and nymphs acquired the pathogen while feeding on infected guinea pigs. The infection persisted through every life stage, all of which were able to transmit R. rickettsii to naïve hosts. The pathogen was also transmitted at a low frequency between generations of H. longicornis through the ova. While H. longicornis was demonstrated to be a competent vector for R. rickettsii under laboratory conditions, the probability of its involvement in the maintenance and transmission of this pathogen in nature, as well as its potential impact on human health, requires further study.
Aedes aegypti L. is considered to have a proclivity for feeding on human blood even when other hosts are available. However, few studies have demonstrated host use by this mosquito in the continental United States, where local transmission of dengue, Zika, and chikungunya viruses has been recently documented. This study investigated the bloodmeal sources of female Ae. aegypti in the subtropical city of Key West and the surrounding county in Florida with the goal of identifying preferred hosts. Blood-engorged Ae. aegypti mosquitoes were collected from BG Sentinel traps used as part of a routine surveillance program in the Florida Keys (Monroe County, Florida). Bloodmeal samples were analyzed using PCR assays, sequencing, and comparison with reference sequences in GenBank. Aedes aegypti females from Key West fed predominantly on humans (79.6%) and did not differ statistically from females collected from the rest of the Florida Keys (69.5%). Culex quinquefasciatus Say (Diptera: Culicidae), considered a host generalist, was collected and analyzed from the same sites for comparative purposes. Females of Cx. quinquefasciatus fed predominantly (70.7%) on birds and nonhuman mammals in the Florida Keys, corroborating the validity of molecular assay breadth and demonstrating that given the same group of available hosts Ae. aegypti selects humans. Our results indicated that Ae. aegypti has a high rate of human-biting in a subtropical area within the United States, supporting its role in recent local transmission of dengue and other viruses.
Nyssomyia whitmani (Antunes & Coutinho) is the sandfly vector of causative agents of American cutaneous leishmaniasis in South and Central America. It is widely spread throughout Brazil, in a close association with domestic animals. Almost nothing is known about male mating aggregations in N. whitmani, let alone the influence of moonlight on this behavior. Thus, the influence of moonlight on male N. whitmani aggregations was investigated by using non-attractant suction traps deployed in chicken cages under full moon and new moon nights. In this 18-night study, 2,160 specimens and seven species were collected. The most frequent species was N. whitmani accounting for 91.48% of the total sample. The abundance of males of N. whitmani was significantly higher in the presence than in the absence of moon. The sex ratio on new moon nights was 1:1 (M:F) and on full moon nights was male-biased (1.7:1). Based on this study, an influence of moonlight on male mating aggregations of N. whitmani was verified. The extent of this influence on increasing sandfly aggregation at hosts, the moonlight influence on the early flight activity of male sandflies and the use of chickens as aggregation sites for males of N. whitmani, are all discussed.
Humans have influenced the epidemiological patterns of American cutaneous leishmaniasis by habitat disturbance, which has led to the emergence of new transmission foci. In these transmission areas, detecting natural infection of sand fly species with Leishmania parasites is of prime importance in epidemiological studies. In this study, we examined the species composition, spatial distribution, seasonality, and natural infection with Leishmania of the sand fly fauna in an emergent leishmaniasis focus located in Colombia. Sand flies were collected from September 2014 to June 2015 using CDC light traps located in indoor, peridomestic, and outdoor habitats within areas with confirmed clinical patients. In total, 13,488 sand flies of 12 species and seven genera were collected. Among these, Pintomyia townsendi (Ortiz) was the most abundant species comprising 76.3% of total flies collected. The sand fly richness and abundance were influenced by habitat and weather conditions. Outdoor areas harbored the greatest diversity of sand flies. Rainfall negatively affected abundance, whereas increased temperature showed a low positive effect. We detected Leishmania amazonensis parasites in Pi. townsendi for the first time.
Dermacentor marginatus Sulkzer is a common tick species found in the Xinjiang Uygur Autonomous Region (XUAR) of China, and is a vector for a variety of pathogens. To determine the potential distribution of this tick species in Xinjiang, a metadata containing 84 D. marginatus presence records combined with four localities from field collection were used for MaxEnt modeling to predict potential distribution of this tick species. Identification of tick samples showed 756 of 988 (76%) were D. marginatus. MaxEnt modeling results indicated that the potential distribution of this tick species was mainly confined to northern XUAR. Highly suitable areas included west side of Altay mountain, west rim of Junggar basin, andYili River valley in the study area. The model showed an AUC value of 0.838 ± 0.063 (SD), based on 10-fold cross-validation. Although tick presence records used for modeling were limited, this is the first regional tick distribution model for D. marginatus in Xinjiang. The model will be helpful in assessing the risk of tick-borne diseases to human and animals in the region.
We added a vector control component to our existing abundance model to simulate intensive vector control in Puerto Rico. Removing 20–30% of gravid females in the model matches observed 60–80% reductions. The model's capacity to reproduce vector control increases its utility for planning and evaluation strategies.
Quantifying arthropod vectors can be a time-consuming process. Here, we describe a technique to count large samples of small arthropods using ImageJ. ImageJ is an open source image processing software, produced by the National Institutes of Health, with a straightforward interface that has proven useful in quantifying small organisms (i.e., cells, pollen, eggs). In 2017, we deployed CDC light traps baited with carbon dioxide among seven sites to capture black flies (Diptera: Simuliidae). Samples of the captured specimens were photographed, and then quantified manually and automatically, using ImageJ. We compared the accuracy of three types of automated counts to manual counts of black flies using an information-theoretic approach. We found that changing the particle size produced counts closest to those obtained by manual counts. Even over a large range of values, from tens to thousands of flies, our automated counts were often identical to and almost always within 5% of the manual counts. When different, automated counts were usually slightly less than manual counts, and thus conservative estimates. This automated technique is simple, repeatable, requires minimal training, and can reduce the time needed to quantify small arthropods such as black flies.
Previous studies suggested the presence of species complex in the so-called Simulium asakoae Takaoka & Davies (Diptera: Simuliidae) in Thailand due to its high morphological variability and genetic divergence. To investigate whether the true S. asakoae is present in Thailand, we performed a detailed morphological identification of S. asakoae and compared its DNA barcodes with the morphospecies S. asakoae from Myanmar and the typical S. asakoae from Malaysia. Phylogenetic analysis revealed the Thai materials analyzed in this study were indeed genetically similar with those from Myanmar and Malaysia, though genetic distances 0–2.27% were observed. We tentatively regard this divergence as intraspecific variation, and the automatic barcode gap discovery analysis further supports them as a single species.
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