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Light-baited suction traps are one of the most widely used tools for vector surveillance.Their popularity stems from ease of use even in remote locations, range and abundance of species caught, and low cost. The availability of smaller, portable models, like the CDC miniature light trap, have further increased their ubiquity in entomological field studies. However, when researchers have looked, light trap collections are usually biased in ways that may affect data interpretation for epidemiological studies. If used alone, light traps may fail to collect important or infected vectors, and light traps are inefficient or ineffective when competing ambient light is present. In this article, we discuss these biases and limitations in terms of their effect on collection efficiency, population data, and pathogen detection. While light trap data certainly have a purpose, an over-reliance on light trapping risks drawing false conclusions about vector populations and vector-borne disease epidemiology. These concerns are especially troubling when light trap data are used to inform policy decisions meant to protect human and animal health. Particularly when a lspecies' response to light is unknown or poorly characterized, light traps should be used in conjunction with supplemental sampling methods. Researchers conducting vector surveillance field studies should carefully consider their study design and objectives when deciding on a trapping method or methods, and specifically endeavor to understand the limitations of their data. Only then can researchers take advantage of the best attributes of light traps while avoiding their dark side.
House dust mites (HDMs) play positive role in causing various kinds of allergenic manifestations such as allergic rhinitis (AR), asthma, dermatitis, and urticaria. HDMs are prevalent in temperate regions but various studies have shown the prevalence of HDMs in tropical and subtropical countries.The present study was conducted from March 2015 to February 2016. During the study period, a total of 500 dust samples were collected from 125 homes of 125 patients suffering from AR and asthma. From these 500 dust samples, 466 samples were found to be positive for mites. The year was divided into three climatic classes, i.e., CCL I (March, April, May, June), CCL II (July, August, September, October), and CCL III (November, December, January, February) A total of 7,710 mites were collected, from which 2,902 (37.63%) mites were found in samples collected during summer season, i.e., CCL-I, 3,728 (48.35%) mites were found in samples collected during rainy season, i.e., CCL-II and only 1,080 (14.01%) mites were found in samples collected during winter season, i.e., CCL-III.Total 7,710 mite specimens were isolated with 7,404, i.e., 96.03% were only from the hypoorder Astigmata, 240, i.e., 3.11% from suborder Prostigmata, 46, i.e., 0.60% from order Mesostigmata, and 20, i.e., 0.26% from suborder Oribatida. The present study indicates that Dermatophagoides pteronyssinus (Trouessart 1897) (Astigmata) was most abundant and frequently found allergenic mite species followed by D. farinae (Hughes 1961), D. microceras (Griffiths and Cunnington 1971), Acarus siro (Linnaeus 1758), Tyrophagus putrescentiae (Schrank 1781), Lepidoglyphus destructor (Schrank 1781), Euroglyphus maynei (Cooreman 1950), Cheyletus, Mesostigmatic, and Oribatida mites.
Fui Xian Koh, Kai Ling Kho, Masoumeh Ghane Kisomi, Li Ping Wong, Awang Bulgiba, Poai Ean Tan, Yvonne Ai Lian Lim, Quaza Nizamuddin Hassan Nizam, Chandrawathani Panchadcharam, Sun Tee Tay
Little information is available on human anaplasmosis and ehrlichiosis in Southeast Asia despite increasing reports of the detection of Anaplasma spp. and Ehrlichia spp. in the ticks. We report herein the serological findings against the tick-borne pathogens in a group of animal farm workers (n = 87) and indigenous people (n = 102) in Peninsular Malaysia. IgG antibodies against Ehrlichia chaffeensis were detected from 29.9% and 34.3% of farm workers and indigenous people, respectively, using commercial indirect immunofluorescence assays. Comparatively, only 6.9% of the indigenous people but none of the animal farm workers were seropositive to Anaplasma phagocytophilum. A polymerase chain reaction (PCR) assay targeting the 16S rRNA gene of Anaplasmataceae was used to identify Anaplastamataceae in ticks collected from various locations adjacent to the areas where the serological survey was conducted. In this study, a total of 61.5% of ticks infesting farm animals, 37.5% of ticks infesting peri-domestic animals in rural villages, 27.3% of ticks collected from wildlife animals, and 29.1% of questing ticks collected from forest vegetation were positive for Anaplasmataceae DNA. Sequence analyses of 16S rRNA gene region (238 bp) provide the identification for Anaplasma marginale, Anaplasma bovis, Anaplasma platys, A. phagocytophilum, and Anaplasma spp. closely related to Candidatus Cryptoplasma californiense in ticks. E. chaffeensis DNA was not detected from any ticks, instead, Ehrlichia sp. strain EBm52, Ehrlichia mineirensis and Candidatus Ehrlichia shimanensis are the only Ehrlichia sp. identified from cattle ticks in this study. Further investigation is required to ascertain the occurrence of zoonotic transmission of Ehrlichia and Anaplasma infections in Peninsular Malaysia.
Sarconesia chlorogaster (Wiedemann) (Diptera: Calliphoridae) is an endemic blow fly species of forensic importance in South America, and whose duration of pupal development is about 70% of the total immature development time. Therefore, morphological changes during this stage, if refined, may provide greater accuracy and reliability in the calculation of minimum postmortem interval. Considering the importance of this species, the main objective of this work was to identify and describe temporal intrapuparial morphological changes of S. chlorogaster. The development of S. chlorogaster reared on an artificial diet and at two constant temperatures (20 and 25°C) was monitored. Every 8 h until the end of the pupal stage, 10 pupae were killed, fixed, and had their external morphology described and photographed. Of the 29 morphological characteristics described, 13 are potentially informative for estimating the age of S. chlorogaster. In general, body shape (presence or absence of tagmatization), general coloration, visible presence of the mouth hook (portion of the mandible), thoracic appendages, change in eye color, and bristle formation are the most useful characteristics for determining specific age. The results presented here make it possible to estimate the postmortem interval of a corpse using intrapuparial morphological characters, expanding one's ability to estimate postmortem interval.
Bat bugs (Cimex adjunctus Barber) (Hemiptera: Cimicidae) collected from big brown bats (Eptesicus fuscus Palisot de Beauvoir) in Colorado, United States were assessed for the presence of Bartonella, Brucella, and Yersinia spp. using molecular techniques. No evidence of Brucella or Yersinia infection was found in the 55 specimens collected; however, 4/55 (7.3%) of the specimens were positive for Bartonella DNA. Multi-locus characterization of Bartonella DNA shows that sequences in bat bugs are phylogenetically related to other Bartonella isolates and sequences from European bats.
Ahmad Ali Hanafi-Bojd, Mehdi Khoobdel, Moussa Soleimani-Ahmadi, Kourosh Azizi, Abbas Aghaei Afshar, Seyed Aghil Jaberhashemi, Sajjad Fekri, Reza Safari
Cutaneous Leishmaniasis (CL) is one of the main neglected vector-borne diseases in the Middle East, including Iran. This study aimed to map the spatial distribution and species composition of sand flies in Hormozgan Province and to predict the best ecological niches for main CL vectors in this area. A database that included all earlier studies on sand flies in Hormozgan Province was established. Sand flies were also collected from some localities across the province. Prediction maps for main vectors were developed using MaxEnt model. A total of 27 sand fly species were reported from the study area. Phlebotomus papatasi Scopoli, Phlebotomus sergenti s.l. Parrot, Phlebotomus alexandri Sinton, Sergentomyia sintoni Pringle, Sergentomyia clydei Sinton, Sergentomyia tiberiadis Adler, and Sergentomyia baghdadis Adler (Diptera: Psychodidae) had the widest distribution range.The probability of their presence as the main vectors of CL was calculated to be 0.0003–0.9410 and 0.0031–0.8880 for P. papatasi and P. sergenti s.l., respectively. The best ecological niches for P. papatasi were found in the central south, southeast, and a narrow area in southwest, whereas central south to northern area had better niches for P. sergenti s.l. The endemic areas are in Bandar-e Jask, where transmission occurs, whereas in Bastak, the cases were imported from endemic foci of Fars province. In conclusion, proven and suspected vectors of CL and VL were recorded in this study. Due to the existence of endemic foci of CL, and favorite ecological niches for its vectors, there is potential risk of emerging CL in new areas.
Juan B. Morales-Malacara, Linda Y. M. Aldana, Enrique Reyes-Novelo, Cenia E. Almazán-Marín, Hugo A. Ruiz-Piña, Alan Cuxim-Koyoc, Álvaro Aguilar-Setién, Helisama Colín-Martínez, Carlos García-Estrada, Margarita Ojeda
A redescription, with a discussion of new features and illustrations, for all life stages is presented for the parasitic mite Periglischrus herrerai Machado-Allison associated with the common vampire bat Desmodus rotundus (Geoffoy), including a description of the heteromorphic female and the first description of its female deutonymph. In addition, the morphological variation of P. herrerai is evaluated by morphometric analysis of the adults, concluding that there is an evident geographic variation throughout the neotropics. This study was possible by using type material of P. herrerai from the Machado-Allison collection, and voucher specimens from other collections, and specimens from an extensive surveying of hematophagous bats in some localities of the Pacific and Atlantic versants, and central Mexico.
Leishmaniasis is a one of the vector-borne diseases and has two clinical forms in Turkey: cutaneous and visceral. The aim of this study was to determine the sand fly fauna in Afyon and Nigde provinces where endemic foci of cutaneous leishmaniasis (CL) in Turkey. In Afyon, 2,259 sand flies were collected in 73 locations in August 2009 and August 2010, using CDC light traps. In total, eight Phlebotomus species were identified; Phlebotomus halepensis (47.41%), Phlebotomus papatasi (31.42%), Phlebotomus neglectus/syriacus (9.38%), Phlebotomus balcanicus (7.48%), Phlebotomus simici (2.12%), Phlebotomus perfiliewi (1.90%), Phlebotomus sergenti (0.08%), Phlebotomus similis (0.13%), and Sergentomyia dentata (0.04%). A total of 418 sand fly specimens were caught by CDC light traps in 40 stations in Nigde in September 2009 and September 2010. In total, seven Phlebotomus species were identified; P. halepensis (74.16%), P. simici (13.87%), P. papatasi (3.82%), P. neglectus/syriacus (2.87%), P. balcanicus (2.63%), P. sergenti (2.39%), and Phlebotomus tobbi (0.23%). Collected sand flies were examined by microscope, and no promastigotes were found in their midguts. We categorized and pooled female specimens (1,031 females, 73 pools of 2–33 individuals). Leishmania species-specific ITS1 real-time PCR assay was performed for detection and identification of parasites. We detected 6 of the 73 pools with Leishmania tropica (Ross, 1903), (Trypanosomatidae). In conclusion, P. halepensis was found to be dominant species in both areas. We are in opinion that our findings support P. halepensis vectorial role for L. tropica in nature and it could be responsible for the transmission of L. tropica in these endemic areas.
A new species of Demodex was detected in the earwax of a dog with otitis externa in Saitama Prefecture, Japan, in July 2010. The opisthosoma length of the mite was slightly shorter than 1/2 of its body length, which was different from the other species in domestic dogs, D. canis and D. injai, but was similar to the form of mites termed “short-bodied species”, including D. cornei. However, the stubby external form was morphologically different from those of “short-bodied species”, excluding a case without a species description reported from Greece. Among known species, the mite was similar to D. equi and D. acutipes.
The Asian Bush Mosquito, Aedes (Finlaya) japonicus japonicus (Theobald) is an important globally invasive mosquito species. In comparison with other major invasive mosquitoes, relatively little is known about Ae. j. japonicus population dynamics in the field. Here, we present results from a 54-biweek long study of Ae. j. japonicus abundance in ovitraps set across the altitudinal gradient of Mt. Konpira, Nagasaki, Japan. Spatially, we found that Ae. j. japonicus fourth instar larvae (Aj4il) were more abundant at the base and top of Mt. Konpira and in ovitraps with more platykurtic water temperature (WT) distributions. In contrast, we found that temporally Aj4il were more abundant when ovitrap WT was more leptokurtic with 2 weeks of lag, and with high relative humidity SD with 2 months of lag. We also found that Aj4il were unlikely present when ovitrap WT was below 12.41°C. Parameter estimates for the Ricker model suggested that Ae. j. japonicus population growth was under density-dependence regulation, with a stable population dynamics whose fluctuations were associated with changes in ovitrap WT kurtosis and demographic stochasticity. Our results suggest that Aj4il abundance is more sensitive to temperature changes in kurtosis than mean values, potentially limiting the predictive ability of Ae. j. japonicus niche models based on the increase of average temperatures with global warming, and suggesting this mosquito species has a relatively coarse-grained response to temperature changes.
Ration of food per capita of larval population is widely thought to limit mosquito production from container habitats, directly reflecting resource limitation. In this study, the importance of density-dependent resource limitation on larval Aedes triseriatus (Say) (Diptera: Culicidae) depended on the degree of microbial conditioning of senescent leaf detritus in surrogate tree holes. Density and ration strongly affected emergence, total female mass, and mean female mass of populations grown on leaves that had conditioned for 3 d, but had less impact when larval populations were grown on leaves that had conditioned for 1 mo. Ration per capita was a stronger predictor (50–94% of the variance) of all growth parameters measured for populations grown on leaves conditioned for 3 d compared with 1 mo (2–66% of variance), with the exception of development time. Larvae grew faster and to a larger body size on leaves conditioned for 3 d at low densities of larvae and a higher ration per capita. However, populations grown on leaves conditioned for 1 mo produced equal or more total mass and individuals of higher average mass than when grown on leaves conditioned for 3 d in treatments with low ration per capita. Well-conditioned detritus, representing the degree of microbial colonization of the organic material, must reflect the typical condition in tree holes with unconditioned leaves atypical. Therefore, results of this study suggest that experiments using well-conditioned leaves better estimate growth responses, including moderated density dependence and less importance of ration per capita, than experiments using unconditioned detritus.
In order to extend the knowledge of the composition of the anopheline community and the seasonal variation related to anthropogenic modifications in the city of Puerto Iguazú, adult females were captured between 2009 and 2012. Samples were collected in three environments with different degrees of anthropogenic modification: urban, periurban, and wild. Alpha diversity was evaluated as the ‘true’ diversity of the species in each environment. Among environments, range-abundance curves were used to compare the composition, abundance, and uniformity of species and cluster analysis was used to analyze the similarities and differences. The temporal distribution was analyzed and the relative abundance of the species captured was correlated with meteorological variables. A total of 4,565 females, belonging to seven species: Anopheles albitarsis s.s. (Lynch-Arribálzaga), Anopheles argyritarsis (Robineau-Desvoidy), Anopheles deaneorum (Rosa-Freitas), Anopheles fluminensis (Root), Anopheles mediopunctatus (Theobald), Anopheles strodei s.l. (Root), and Anopheles triannulatus s.l. (Neiva and Pinto) were captured. The wild environment showed higher abundance, diversity, and greater uniformity reflected on the less sharp area of the range–abundance curve. Species richness was the same in the wild and periurban environments. Higher abundances were observed in summer during the months with higher temperatures. Although the wild environment showed greater Anopheles abundances and diversity, specific richness and species complementarity were similar among the three environments studied. Thus, the periurban environment would turn into a transition zone of great epidemiological importance due to the introduction of people in this environment, which represents a potential risk of malaria transmission in the area.
A growing body of literature on mosquito oviposition behavior supports the hypothesis that females place eggs in habitats that provide best available opportunity for growth, development, and maturation of their offspring. We conducted a field experiment to evaluate Culex oviposition behavior in response to the interspecific competitor Aedes triseriatus (Say) (Diptera: Culicidae) larvae, and resources in the form of quantity of plant detritus, and dissolved nitrogen (TN) and phosphorus (TP) derived from that detritus. We tested a set of specific predictions: 1) As a poorer competitor, Culex will avoid ovipositing in containers with superior interspecific competitors; 2) Culex choose oviposition habitats that contain greater amount of resources for the microbial food of their offspring; 3) Sufficiently high resource abundance can override avoidance of oviposition in containers with interspecific competitors. Culex restuans Theobald (Diptera: Culicidae) was the only species ovipositing, and the oviposition responses changed over time. The effect of resources was more important in driving oviposition decisions at the beginning and end of the experiment. The amount of resources, as manifest by TN and TP concentrations, had differential effects on oviposition. At the beginning females laid more eggs in containers with low detritus, which had the highest TN. After that, females preferred those containers with high detritus, which had low TN and high TP. The effect of competitors was important only during the middle of the experiment. Paradoxically, even as a poorer competitor Cx. restuans preferentially oviposited in containers with late-instar Ae. triseriatus, suggesting that the presence of successful heterospecifics indicates a good quality larval habitat.
Triatoma sordida Stål (Hemiptera: Reduviidae), a secondary vector of Trypanosoma cruzi Chagas (Kinetoplastida: Trypanosomatidae), occasionally colonizes human sleeping quarters in Paraguay, Bolivia, and Brazil, whereas only sylvatic and peridomestic populations are found in Argentina. We carried out a cross-sectional survey of house infestation in a well-defined rural area of northeastern Argentina to identify the key habitats of T. sordida; describe its spatial distribution in an apparently undisturbed setting under no recent insecticide treatment and use metapopulation theory to investigate these spatially structured populations. Timed-manual searches in 2,177 georeferenced sites from 368 houses yielded T. sordida in 78 sites (house infestation prevalence, 19.9%). Most triatomines occurred in chicken nests, chicken coops, and trees where chickens roosted (prime habitats). Goat or sheep corrals and pig corrals had a lower fraction of occupied sites (occupancies) and abundance. Both occupancy and catch increased with increasing refuge availability according to multimodel inference with model averaging.The majority of suitable habitats were unoccupied despite their proximity to occupied sites.The site-specific occurrence of T. sordida and Triatoma infestans Klug (Hemiptera: Reduviidae) was positively and homogeneously associated over ecotopes, showing no evidence of interspecific interference. An incidence function metapopulation model (including intersite distances and vector carrying capacity) predicted a fivefold greater occupancy relative to the observed pattern, suggesting the latter represented a transient state. T. sordida failed to colonize human sleeping quarters, thrived in peridomestic habitats occupied by chickens, and had a limited occupancy likely related to a poor colonizing ability and the relative instability of its prime habitats
Mohammad Shafiul Alam, Hasan Mohammad Al-Amin, Rubayet Elahi, Sumit Chakma, Mohammad Abdullah Heel Kafi, Wasif A. Khan, Rashidul Haque, David A. Sack, David J. Sullivan, Douglas E. Norris
Malaria is a major health burden in the border-belt areas of Bangladesh.There are recent data from adult mosquito collections that a number of vectors are involved in the transmission cycle. However, little information regarding the larval habitats of Anopheles mosquitoes are available in Bangladesh. To start filling this gap, a cross-sectional larval survey was conducted in Bandarban, Bangladesh from October 2011 to September 2012. Descriptive analysis, Poisson regression, spearman correlations and zero-inflated Poisson regression were used to calculate the degree of association between the abundance of larval Anopheles species and environmental factors. From the 300 larval habitats sampled, 5,568 Anopheles larvae were collected and of these, 2,263 (40.6%) were identified to species. Collections represented 16 Anopheles species with Anopheles vagus (26.4%, n = 598) as the dominant species. A total of 16 Anopheles larval habitat types were identified. Larval abundance was significantly different (P < 0.05) among habitats with pond (40%, n = 914) and rice field (34%, n = 779) implicated to be the most utilized. Larval abundance varied significantly (P < 0.05) with habitat characteristics. Most of the larvae were collected from sites with a range of pH from 7.0 to 8.0. Data obtained from this study revealed both natural and human-created larval habitats were favorable for anopheline larval survival and development. Such information elucidates plausible drivers of high anopheline diversity, high vector abundance, changes in relative species abundance from historic data, and sustained transmission of malaria in endemic areas of Bangladesh.
Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae) is a key bluetongue virus vector in the United States. Immatures occur in mud near the edges of wastewater ponds and are understudied targets for control efforts. Eggs of C. sonorensis were collected in the morning from a dairy wastewater pond bank by taking 5-ml surface mud samples along four transects on each of six dates. Surface mud samples parallel to waterline (10-cm long, 1-cm wide, and 0.5-cm deep) were removed at 5-cm increments ranging from 15 cm below waterline up to 25 cm above waterline. Eggs were removed using MgSO4 flotation, held on moist filter paper, and scored for hatching over 3 d. Eggs hatching on days 2 and 3 were assumed to have been laid on the test night. Water levels were stable within a night according to time-lapse camera photos. Most samples from below the waterline had no eggs and were not analyzed statistically. Mean (±SE) sample moisture (25.8 ± 2.1 at 5 cm above waterline and 19.8 ± 2.6% at 25 cm above waterline) did not vary significantly by position above waterline. The highest density of viable eggs (21 eggs/5 ml), proportion of mud samples positive for viable eggs (75%), and proportion of eggs hatching (80%) were found 5 cm above waterline. Oviposition in the few hours after sunset is adaptive, allowing eggs to age, develop the serosal cuticle, and resist later desiccation. As a potential control method, reducing water levels after midnight would encourage young egg desiccation.
VECTOR CONTROL, PEST MANAGEMENT, RESISTANCE, REPELLENTS
Mosquitoes exposed to sublethal doses of insecticides may be selected for resistance to insecticide active ingredients (AIs). Mosquitoes are exposed to AIs through agricultural, public/private mosquito control programs, homeowners, and other sources. Hence, mosquito control programs should routinely measure the resistance/susceptibility status of mosquito populations of public health concern.The objectives here were to determine resistance status for six AIs used in adult mosquito control in the United States to assess how resistance/susceptibility differs between AI, mosquito species (states where > 1 species collected), and between years (some populations sampled for 2 yr). Field-collected eggs from 21 mosquito populations of six different species or hybrid species (Aedes albopictus Skuse [Diptera: Culicidae], Aedes aegypti L. [Diptera: Culicidae], Culex nigripalpus Theobald, Culex pipiens L. [Diptera: Culicidae], Culex quinquefasciatus Say [Diptera: Culicidae], Cx. pipiens/quinquefasciatus) were obtained. Centers for Disease Control and Prevention bottle bioassays were used to assess the resistance/susceptibility status for six AIs (bifenthrin, deltamethrin, etofenprox, malathion, permethrin, and phenothrin). World Health Organization guidelines were used to classify mosquitoes as susceptible (98–100% mortality at diagnostic time [DT]), possibly resistant (80–97% mortality at DT), or resistant (<80% mortality at DT). Significant differences were observed in mosquito susceptibility/resistance between species and AIs. In states where both Aedes and Culex were collected, the odds of exhibiting resistance in Culex were 68–69 times higher than Aedes (Texas odds ratio: 69.30; 95% confidence interval: 5.86, 819.44; P = 0.001; North Carolina odds ratio: 67.99; 95% confidence interval: 15.21, 303.94; P < 0.0001). Some level of resistance was detected against all tested AIs in several mosquito populations and some varied between 2015 and 2016.
California pastured cattle were treated with 250 ml of a 15% mixture of fatty acids (C8–C9–C10) or 125 ml of 2% geraniol in a mineral oil carrier to assess impacts on horn flies, Haematobia irritans (L.) (Diptera: Muscidae) over two summers. Horn flies were netted from cattle every 3–4 d for 2 wk before treatment, 2 wk during treatment (four treatments, with flies collected before each treatment), and 2 wk after treatments ceased. Blood meal weights were estimated by hemoglobin assay of excised abdomens. Other females were dissected to determine the number of active ovarioles and the stage of primary follicle development. Depending on year and herd, pretreatment males contained an average of 0.6–1.0 mg of blood, while females contained 1.7–2.7 mg. Pretreatment egg development (least developed oocytes were stage 1 and fully developed eggs were stage 5) averaged 3.7–4.3, and number of active ovarioles averaged 18.1 to 19.6/female. During treatment periods, significant reductions in blood weight were noted for females, but usually not for males, and females also often exhibited reduced mean oocyte stage and number of active ovarioles. Peaks in proportions of young nulliparous females (oocyte stages 1 or 2) were seen during some repellent application periods. This suggested older females had been killed or driven off from the local population by the treatments, and flies on cattle included more young flies that likely were recent arrivals. The repellent-oil mixture thus impacted blood feeding, reproductive fitness, and probably age structure in the field.
Pablo A. Kuri-Morales, Fabián Correa-Morales, Cassandra González-Acosta, Miguel Moreno-Garcia, Eduardo Dávalos-Becerril, José Ismael Benitez-Alva, Jorge Peralta-Rodriguez, Victor Salazar-Bueyes, Jesús F. González-Roldán
In Mexico, Aedes aegypti (L.) (Diptera: Culicidae) is the primary vector of Dengue, Zika, and Chikungunya viruses. Control programs include community participation using personal protection such as household aerosol insecticides. In both, urban or rural areas, the use of aerosol insecticides is a common practice to avoiding mosquito biting. Thus, information on the efficacy of commercial products must be available. This study reports the efficacy of 13 household aerosol insecticides against Ae. aegypti from an endemic dengue area in Mexico.To test each insecticide, six netting cages, containing 10 non-blood fed female mosquitoes each one, were placed in different locations inside a bedroom. Readings at 30 min and 24 h after exposure were recorded. No products showed 100% mortality after 30 min of exposure. Only three products killed the 100% of the individuals 24 h after exposure. Results showed a high mortality variance among insecticides. Location in the room also impacts the insecticide efficacy. Mosquitoes located inside cabinets or with behind an obstacle (preventing an accurate insecticide exposure) showed lower mortalities. Products and spraying methods could and should be improved.
Bacillus sphaericus Neide, recently renamed as Lysinibacillus sphaericus Meyer and Neide, is a spore-forming bacterium that possesses various levels of larvicidal activity, depending on the strains, against some mosquito species. Products based on most active strains such as 2362, 2297, 1593, C3-41 that bear binary toxins, as well as mosquitocidal toxins at various levels, have been developed to combat mosquito larvae worldwide. Resistance in wild Culex mosquito populations has been reported since 1994 from France, Brazil, India, China, Thailand, and Tunisia. Laboratory studies to evaluate resistance development risk have been conducted by many groups of scientists worldwide. Products based on L. sphaericus strain 2362 were registered in the United States in 1990s, and their use for mosquito control has been increased considerably since invasion of West Nile virus. This report documents the first occurrence of high-level resistance to L. sphaericus in a natural population of Culex pipiens L. in Chico, CA, where resistance ratio was 537.0 at LC50 and 9,048.5 at LC90 when compared with susceptible laboratory colony of the same species. Susceptibility profile to other groups of pesticides with different modes of action was also determined. Various levels of resistance or tolerance were noticed to abamectin, pyriproxyfen, permethrin, and indoxacarb. Resistance management and susceptibility monitoring strategies are discussed and recommended.
Novel treatments for cutaneous leishmaniasis (CL) are needed, due to current lack of effective universal treatments, increasing resistance among the parasite, and toxic effects or impracticality of the current therapeutics. Models of direct infection with high number of Leishmania parasites in the current research of CL involving the BALB/c mouse or Golden Syrian Hamster are considered not suitable for the assessment of antileishmanial drug efficacy because of the lack of disease similarities with humans. The saliva of the sand fly vector is known to affect the host response to infection by the Leishmania parasite. Here, we build upon a previous BALB/c model infected with luciferase-expressing Leishmania major parasites. In the present study, we infect the ear dermis instead of the foot pad or base of the tail, and compare multiple methods of infection, using parasites alone or mixed with either bites from uninfected sand flies (Phlebotomus duboscqi Diptera Psychodidae:Neveu-Lemaire) or salivary gland sonicate from sand flies. Our data show a dose–response of bioluminescent signal (which represents the parasite load at the infection site), dermal lesion development, and Leishmania Donovan Units in liver and spleen. This in vivo L. major ear infection model, once optimized, can be used for assessing the efficacy of drug compounds that have been determined as very effective in the other, high inoculum CL models.
House flies (Musca domestica L. [Diptera: Muscidae]) can act as a mechanical vector for food-borne pathogens including Shiga toxin-producing Escherichia coli (Migula; Enterobacteriales: Enterobacteriaceae) (STEC) in and around cattle feedlots.The present study assessed the prevalence of STEC in house flies from a restaurant area of a town in northeastern Kansas.Two hundred twenty-four house flies were collected over 10 wk, surface sterilized, individually homogenized, and cultured by a multifaceted approach of direct plating on selective media and an enrichment broth, followed by the immunomagnetic separation. Bacterial isolates were screened for eight serogroups of E. coli: O103, O104, O26, O111, O45, O145, O121, and O157 using multiplex polymerase chain reaction (PCR). Furthermore, O-serogroup-positive isolates were tested for virulence genes stx1, stx2, eae, and ehxA by PCR.The majority (91.5%) of flies carried enteric bacteria, and the mean value of enteric concentration on the modified Possé agar was 6.7 ± 1.1 × 106 colony forming units per fly. Thirty-nine of the 224 flies (17.4%) were positive for one or more E. coli serogroup of interest; with the majority O103 (10.7%), followed by O26 (3.1%), O121 (1.3%), O45 (1.3%), and O104 (0.9%). However, none of the serogroup-positive isolates carried any of the virulence genes tested. Results of our study show that house flies in the urban environment do not carry STEC. Nevertheless, detection of E. coli O-serogroups with the potential to acquire virulence traits indicates that house flies in an urban environment represent a public health risk.
This study investigated possible transstadial transmission of Ehrlichia canis by Rhipicephalus sanguineus sensu lato collected from shelter dogs and the shelter grounds in Diyarbakır Province of south-eastern Turkey. Totally 225 engorged nymphs were collected from eight infected dogs with E. canis and incubated at 28°C for moulting. Unfed ticks from the shelter grounds comprising 1,800 larvae, 3,100 nymphs, and 85 adults were sorted according to sampling origin, life stage, and sex into 116 pools and screened by 16S rRNA PCR. Nine out of 26 pools of unfed adult ticks were positive for E. canis, with overall infection rate maximum likelihood estimation (MLE) of 4.83 (CI 2.39–8.87). E. canis was detected in three of 12 male pools (MLE 3.22, CI 0.86–8.83) and six of 14 female pools (MLE 6.16, CI 2.59–12.90). No adult pools collected from the shelter grounds were positive. Among 62 unfed nymph pools collected from the shelter, six were infected with E. canis (MLE 0.20, CI 0.08–0.42). No E. canis DNA was detected in any of the larva pools. Our results revealed molecular evidence for transstadial transmission of E. canis by R. sanguineus s.l. both from larva to nymph and from nymph to adult. We found no evidence of transovarial transmission.
Raquel Silva Fonteles, Adalberto Alves Pereira Filho, Jorge Luiz Pinto Moraes, Silma Regina Ferreira Pereira, Bruno Leite Rodrigues, José Manuel Macário Rebêlo
To elucidate portions of the transmission cycles of American tegumentary leishmaniasis (TL) and visceral leishmaniasis (VL) occurring in the region surrounding the Lençóis Maranhenses National Park, an important tourist center in Brazil, the present study objectives were to determine the rate of natural infection by Leishmania spp. and the blood meal in caught sand flies species in the region. Sand flies were captured over 36 mo in 62 locations of the municipality of Barreirinhas, Maranhão with notifications of disease incidence. Species identification of parasites was performed with internal transcribed spacer 1 (ITS1) PCR-RFLP using HaeIII enzyme. Blood meal identification was performed with cytochrome b (cytb) gene PCR-RFLP using HaeIII and MboI enzyme. The species Lutzomyia longipalpis (Lutz and Neiva 1912) presented a positivity rate of 3.7% for Leishmania infantum. Species not considered vectors of this parasite such as Lu. lenti (Mangabeira 1938) and Lu. whitmani (Antunes & Coutinho 1939) showed infection rates of 0.6% and 0.9%, respectively. Among the vectors of Leishmania spp. was Lu. whitmani with detection rate of 0.3% for Le. braziliensis and Lu. flaviscutellata (Mangabeira 1942) with a detection rate of 8% for Le. amazonensis. After restriction of amplification product encoding a 359bp sequence of the cytb recognized in as follows: pigs (37.9%); dogs (27.4%); chickens (20.9%); horses (9%), rodents (3.3%), and humans (1.4%).The presence of Leishmania DNA in sand flies fed with human blood and domestic animals in villages with transmission of VL and TL suggests that transmission could be occurring in the locations of the infected patients.
Ectoparasites at primate research centers may be difficult to control, e.g. without exposing non-human primates (NHPs) to toxicants, but their impact on NHP health is poorly understood. In 2010, there was an epizootic of tularemia at the California National Primate Research Center (CNPRC) in Yolo County, California that resulted in 20 confirmed and suspect clinical cases in outdoors housed rhesus macaques (Macaca mulatta [Zimmermann]) and a 53% seroprevalence in the southern section of the colony. We studied ectoparasite burdens at the CNPRC in order to understand possible conditions at the time of the epizootic and provide data for the management of ectoparasites for the future. In 2015, we recorded 52 California ground squirrel (Otospermophilus beecheyi [Richardson]) burrow systems in the southern colony and collected 560 fleas. The largest number of fleas (n = 184) was collected in October and the most common species were Hoplopsyllus anomalus (Baker) (n = 331), Oropsylla montana (Baker) (n = 158), Echidnophaga gallinacea (Westwood) (n = 60), and Ctenocephalides felis (Bouché) (n = 11), all of which are opportunistically anthropophilic. Free, non-host-associated fleas included 12 H. anomalus, 9 C. felis, 6 O. Montana, and 1 E. gallinacea. We collected 1 H. anomalus from a rhesus macaque. Our results suggest a high potential for the rapid spread of zoonotic infectious diseases via flea transmission in primate facilities with ground squirrels and that flea control measures should be given a high priority.
Canine tick-borne pathogens are the source of emerging diseases and have important zoonotic relevance. Dogs play a major role in the transmission of several zoonotic tick-borne pathogens, as reservoirs and/or sentinels. To simultaneously detect Anaplasma and Ehrlichia species, a reverse line blot assay was conducted on 219 blood samples collected from autochthonous asymptomatic shelter dogs. One hundred and three (47.0%, CI 40.3–53.9) dogs were positive for one or both rickettsial pathogens. Seventy-one (32.4%, CI 26.3–39.0) dogs were infected with Anaplasma platys and 23 (10.5%, CI 6.8–15.3) with Ehrlichia canis. Concurrent infection with A. platys and E. canis was detected in nine (4.1%, CI 1.9–7.6) dogs. Partial sequences of the 16S ribosomal RNA gene shared 100% identity with the corresponding published sequences for A. platys and E. canis. Infection with Anaplasma phagocytophilum was not detected in the examined dogs. In total, 1018 (range 1–70, mean intensity 13.1, mean abundance 4.6) Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) sensu lato ticks (45.7% nymphs, 54.3% adults) were collected from the dogs.There was no significant association between Anaplasma/Ehrlichia infection and dog sex or age, but a significant correlation was found between rickettsia infection and presence of R. sanguineus. Improved tick control strategies to reduce the risk of these pathogens spreading among dogs and humans are needed in the region.
Adult stages of Amblyomma parvitarsum Neumann parasitize wild and domestic camelids of the genera Lama and Vicugna in highlands of Andean Plateau and Patagonia. Within the Peruvian Andes, few reports have documented this tick-host association, and although reported in Chile and Argentina, Rickettsia-infected A. parvitarsum remains undocumented for this country. Here we report a new collection of A. parvitarsum from Peru, the finding of the first gynandromorph for the species and high prevalence of Rickettsia in adult stages.
Yeray Brito-Casillas, Mercedes Díaz-Sarmiento, Moisés García-Arencibia, Cristina Carranza, Antonio Castrillo, Leandro Fernández-Pérez, Manuel Zumbado-Peña, Jorge F. González, Ana M. Wägner
A zoonotic, opportunistic out-break of tropical rat mite Ornithonyssus bacoti [Acari: Macronyssidae; Ornithonyssus bacoti (Hirst)] in an animal facility, is described. Immunocompetent mice [Mus musculus (Linnaeus)] and rat [Rattus norvegicus (Berkenhout)] strains in a conventional health status facility suffered from scratching and allopecia and staff members suffered from pruritic, erythemato-papular lesions, presumed to be allergic in origin. O. bacoti was identified and treatment with a 0.1% ivermectin solution led to its complete erradication. Safety assessment revealed no signs of acute toxicity in any animal strain. Following this inexpensive strategy, 7 wk after the initial dose, samples were negative for the presence of acari. At the time of this report, 26 months after diagnosis, O. bacoti remains undetected.
Mosquito control programs in the United States are still searching for best management practices to control the Asian tiger mosquito, Aedes albopictus (Skuse; Diptera: Culicidae). Most intervention methods for this species are either labor intensive (e.g., source reduction) or short-term (e.g., ultra-low-volume adulticiding). We investigated the effectiveness of barrier spray pesticide applications within urban and suburban residential yards in New Jersey as a control strategy using a before-after-control-impact (BACI) approach. Applications of Demand CSR pyrethroid (9.7% AI lambda-cyhalothrin) only or combined Demand CSR and Archer IGR insect growth regulator (1.3% AI pyriproxyfen) applications resulted in significant and similar decreases in adult mosquito abundance posttreatment ranging from 78 to 74% respectively, compared with the untreated control. Both insecticides exceeded the 70% reduction threshold considered as effective for Ae. albopictus control for 2 to 4 wk. However, applications of Archer IGR alone did not reduce adult mosquito abundance.The field study results were supported by laboratory no-choice bioassays using treated leaf foliage. Our study is the first data driven evidence of the residual efficacy of barrier pesticide applications in New Jersey with lambda-cyhalothrin that provided significant reductions in adult Ae. albopictus populations for an extended duration.
Wyeomyia (Wyeomyia) mitchellii (Theobald) (Diptera: Culicidae) was recovered for the first time on Guam, United States of America, in 2017. Larval specimens were collected from water-filled axils of bromeliads during a larval survey carried out in a residential neighborhood of the Chalan Pago/Ordot area. Native to the New World, Wy. mitchellii has likely made its way to the Pacific Islands through the possibly illegal import of ornamental bromeliads. While this mosquito does not represent a significant threat to public health, this finding highlights the vulnerability of the Pacific Islands to the introduction of exotic species, including mosquito species that may increase public health risks.
The Gravid Aedes Trap (GAT) is a passive trap that relies on visual and olfactory cues to lure and capture gravid mosquitoes. The GAT was designed as a dengue vector surveillance tool for use in conditions where power sources are not readily available. Experiments were conducted over a 10-d period in Fiji to determine which species of mosquitoes the GAT would collect, how different infusion types affect the attractiveness of the trap, how long each infusion type took to begin attracting mosquitoes, and how long the infusion was attractive to container breeding Aedes mosquitoes. Infusions were created by adding 10 g of organic material to 2 liters of water. Infusions were made using chicken feed pellets, dried mango leaves (Mangifera indica), and dried lawn grasses (primarily Axonopus spp.). The GAT collected four different vectors Aedes aegypti (Linnaeus) (Diptera: Culicidae), Aedes albopictus (Skuse) (Diptera: Culicidae), Aedes polynesiensis Mark (Diptera: Culicidae), and Culex quinquefasciatus Say (Diptera: Culicidae). As observed in previous studies, using some type of organic infusion improved the attractiveness of the trap. Of the three different infusion components tested, chicken feed was most attractive followed by lawn grasses and mango leaves. All infusions performed better than plain water. Chicken feed was found to be most attractive for Ae. aegypti and Ae. albopictus during the first 6 d after placing the traps and for Cx. quinquifasciatus in days 7–9. The mango and grass infusions took longer to attract mosquitoes but were most attractive during days 7–10 for all species.
Due to the limited understanding of the sylvatic cycle of Chagas disease transmission, an efficient method to attract and capture sylvatic triatomines (Hemiptera: Reduviidae) is essential to monitor human exposure risk. Current collection methods for sylvatic species, though effective, are labor- and time-intensive. This study evaluated whether modified cross-vane panel traps (commonly used in forest entomology) can be used to attract and capture flying life-stages of sylvatic triatomines and whether a commercially available lure is effective in attracting sylvatic triatomines in the field. We evaluated four trap treatments in both the wet and dry seasons in central Panama: a cross-vane panel trap fitted with an ultraviolet (UV) light, a cross-vane panel trap fitted with a commercially available human-volatile lure, a cross-vane panel trap fitted with both a UV light and a human-volatile lure, and a white sheet fitted with a UV light (a standard collection method) as a control. A total of 45 adult Rhodnius pallescens Barber were captured across 10 nights of trapping representing 112 trap-nights. There was a significant overall effect of trap type on collection success; sheet traps collected more triatomines than lure traps, and there were no differences between the sheet trap and the UV trap, nor between the sheet trap and the UV + lure trap.The lure-only trap did not capture any triatomines in this study. These results indicate that cross-vane panel traps with a UV light are as effective as a sheet trap but offer the advantage of requiring less time and effort to maintain and monitor.
The main objective of this study was to assess insecticide contamination in Anopheles breeding habitats in urban residential areas and pyrethroid susceptibility status of mosquitoes found in the habitats. A larval survey was conducted in Akim Oda between July and October 2016. The larvae that were reared to adult were used for susceptibility test against four different pyrethroid insecticides (deltamethrin 0.05%, permethrin 0.75%, cyfluthrin 0.15%, and etofenprox 0.5%). Gas chromatography was used to analyze pesticide residues in water collected from the breeding habitats. High levels of permethrin and deltamethrin plus traces of several organochlorine and organophosphate insecticides were detected in the larval-breeding habitats. None of the four pyrethroid insecticides caused more than 10% mortality. Anopheles coluzzii Coetzee & Wilkerson dominated in the study area with high frequency of kdr mutation (93.5%). We report for the first time in Ghana, high levels of pyrethroid insecticides contamination in Anopheles breeding habitats in urban residential areas where there are no major agricultural activities.The contamination is suspected to be the major cause of pyrethroid resistance in the Anopheles species. Improper disposal of old insecticide-treated net and other domestic insecticides and the use of herbicides are suspected to be the source of insecticide contamination.
Chemical fertilizers are used everywhere, which often pollute the breeding sites of mosquitoes. In this laboratory study, the consequences on Aedes aegypti (L.) (Diptera: Culicidae) and Anopheles gambiae (Giles) (Diptera: Culicidae) of water-containing plant matter (PM) alone, or in association with an NPK type of fertilizer (PM+NPK), were evaluated. To obtain a 20% imaginal emergence of An. gambiae (IEt20), the bioassays carried out with PM have evidenced that its larvae need four times as much food as for Ae. aegypti larvae. The PM+NPK combinations significantly improve the survival rates of both mosquitoes multiplying the percentages of imaginal emergence by 1.7–3 (synergistic effect). The log-probit analysis of the adult emergence also reveals that the environments containing fertilizers accelerates by two to four times the development of the mosquito larvae.
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