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Over 90% of human flea-borne rickettsioses cases in California are reported from suburban communities of Los Angeles and Orange counties and are presumed to be associated with either Rickettsia typhi or Rickettsia felis infection. Ctenocephalides felis (Bouché) is considered the principal vector for both rickettsiae, and R. felis has largely replaced R. typhi as the presumptive etiologic agent based on the widespread incidence of R. felis in cat flea populations. However, with no evidence to confirm R. felis as the cause of human illness in southern California, coupled with recent findings that showed R. felis to be widespread in cat fleas statewide, we propose that this hypothesis should be reconsidered. Evidence of only limited numbers of R. typhi-infected cat fleas in the environment may indicate a very rare infection and explain why so few cases of flea-borne rickettsioses are reported each year in southern California relative to the population.
Japanese encephalitis virus (JEV) is the most frequent cause of mosquito-borne encephalitis in Asian countries. Several culicine species are potential vectors. The primary JEV vectors feed mainly on cows (a dead-end host for JEV), pigs (an amplifying host), and, occasionally, humans (a dead-end host). It is essential to determine blood-feeding patterns to understand the transmission cycle of the disease. Here we review blood-feeding characteristics of the primary JEV vectors Culex tritaeniorhynchus, Culex vishnui, and Culex gelidus based on experimental works and field surveys conducted in Asian countries. Several studies showed that these JEV vectors have an innate preference for cows; however, the former two species often showed higher rates of blood-feeding on pigs than on cows, probably because pigs are more abundant than cows. On the other hand, the latter species Cx. gelidus fed mostly on cows. Thus, the first two species showed higher plasticity to compromise host availability than the last. By reviewing the available articles and based on our relevant studies, it may be deduced that JEV transmission cannot be reduced by zooprophylaxis. We emphasize the need of keeping cows away from the human residences to dampen the human risk of JEV. These primary JEV vector species exhibit pre-biting resting. The adaptive significance of this behavior remains to be unexplored, but it may have a function to avoid defensive attack of host animals. Application of recent quantitative analysis of gene expression in this phase may enable us to come up with novel vector control strategies.
Michele C. Paula, William F. Antonialli-Junior, Angélica Mendonça, Kamylla B. Michelutti, Aylson D.M.M. Eulalio, Claudia A. L. Cardoso, Thiago de Lima, Claudio˘J. Von Zuben
Necrophagous insects such as blow flies (Diptera: Calliphoridae) are considered crucial in forensic entomology. Identification at species level and determination of larval stage are the basis for estimation of postmortem interval (PMI). Insect evidence can also be used in the determination of crime scenes, since body displacement is common. The aim of this study was to determine the chemotaxonomic profile and intraspecific variability of the forensically important blow fly Chrysomya megacephala (F. 1794). Adults were collected in the municipalities of Dourados-MS (Brazil) and Rio Claro-SP (Brazil), and then transferred to the laboratory for oviposition and development of the immature stages. Chemical analysis of cuticular compounds was performed by gas chromatography. Cuticular chemical profiles varied significantly between the two populations, as well as between developmental stages, supporting the use of these compounds as a complementary tool to help identify the species and its stages, along with geographical variability. This could greatly accelerate forensic investigations, eliminating the need to allow the fly larvae to develop until adult stage in order to confirm the species identity and sample origin.
Determining the control threshold for a pest is common prior to initiating a pest control program; however, previous studies related to the house fly control threshold for a poultry farm are insufficient for determining such a threshold. This study aimed to predict the population changes of house fly population by comparing the intrinsic rate of increase (rm) for different house fly densities in a simulated system. This study first defined the knee points of a known population growth curve as a control threshold by comparing the rm of five densities of house flies in a simulated condition. Later, to understand the interactions between the larval and adult populations, the correlation between larval and adult capacity rate (rc) was studied. The rm values of 300- and 500-fly densities were significantly higher compared with the rm values at densities of 50 and 100 flies. This result indicated their representative indices as candidates for a control threshold. The rc of larval and adult populations were negatively correlated with densities of fewer than 300 flies; this implicated adult populations with fewer than 300 flies as declining while the larval population was growing; therefore, control approaches should focus on the immature stages. The results in the present study suggest a control threshold for house fly populations. Future works should focus on calibrating the threshold indices in field conditions.
Calliphorid species form larval aggregations that are capable of generating heat above ambient temperature. We wanted to determine the relationship between volume, number of larvae, and different combinations of instars on larval mass heat generation. We compared different numbers of Chrysomya megacephala (F.) larvae (40, 100, 250, 600, and 2,000), and different combinations of instars (∼50/50 first and second instars, 100% second instars, ∼50/50 second and third instars, and 100% third instars) at two different ambient temperatures (20 and 30 °C). We compared 13 candidate multiple regression models that were fitted to the data; the models were then scored and ranked with Akaike information criterion and Bayesian information criterion. The results indicate that although instar, age, treatment temperature, elapsed time, and number of larvae in a mass were significant, larval volume was the best predictor of larval mass temperatures. The volume of a larval mass may need to be taken into consideration for determination of a postmortem interval.
Abedin Saghafipour, Hassan Vatandoost, Ali Reza Zahraei-Ramazani, Mohammad Reza Yaghoobi-Ershadi, Yavar Rassi, Mohammad Reza Shirzadi, Amir Ahmad Akhavan
Zoonotic cutaneous leishmaniasis (ZCL) is transmitted to humans by phlebotomine sand fly bites. ZCL is a major health problem in Iran, where basic knowledge gaps about sand fly species diversity persist in some ZCL-endemic areas. This paper describes the richness and spatial distribution of sand fly species, collected with sticky traps, in Qom province, a ZCL-endemic area in central Iran, where sand fly fauna has been poorly studied. Collected species were mapped on urban and rural digital maps based on a scale of 1/50,000. All analyses were undertaken with rural- and urban-level precision, i.e., rural and urban levels were our basic units of analysis. After identifying the sand flies, high-risk foci were determined. For spatial analysis of vector species population, the entomological sampling sites were geo-referenced using GPS. Arc GIS 9.3 software was used to determine the foci with leishmaniasis vector species. Following the analyses, two genera (Phlebotomus and Sergentomyia) and 14 species were identified. Based on the mapping and sand fly dispersion analysis, the rural districts were categorized into three groups—infection reported, without infection, and no report. Based on Geographical Information System analyses, Kahak and Markazi districts were identified as high-risk foci with leishmaniasis vector species. These findings can act as a help guide to direct active control measures to the identified high-risk foci and, eventually, lead to reduction in incidence of the disease.
In order to provide a broad picture on the origin and evolution of holocentric X chromosomes in heteropteran species, we prepared a sex chromosome painting probe by microdissection of the X1 and X2 chromosomes from a kissing bug Mepraia spinolai (Hemiptera: Reduviidae: Triatominae). Fluorescence in situ hybridization on four species of the Triatomini having different amounts of autosomal heterochromatin and sex chromosome systems show that the Xs probe hybridizes on the euchromatin, located both on autosomes and X chromosomes. The heterochromatic Y chromosome and autosomal heterochromatic regions always appear free of hybridization signals. The hybridization results of the Xs probe on Rhodnius prolixus (Rhodniini) is completely different to that observed in Triatomini species. The hybridization signals are small and scattered on all euchromatin, without specific regions including the X chromosome. These results are in accordance with previous data obtained by genomic in situ hybridization and fluorescent banding, suggesting a clear differentiation in the repeat sequence composition of both sex chromosomes between Triatomini and Rhodniini tribes. These results also support that each sex chromosome in Triatomini has evolved independently from different autosomal pairs of a common ancestor, as described in other insect orders.
Lipoptilocnema Townsend is a small genus of Neotropical Sarcophaginae with a distinctive genitalic morphology. This genus is revised based on the examination of the type series and large numbers of specimens of the seven previously known species, plus three new ones herein described, one from Argentina (L. delfinado Mulieri and Mello-Patiu, sp. nov.), and two from Brazil (L. savana Mulieri and Mello-Patiu, sp. nov. and L. tibanae Mulieri and Mello-Patiu, sp. nov.). All species are described or redescribed and illustrated. Distribution maps and a key for male identification are provided. The taxonomic position of this genus is reviewed and the interpretation of phallic structures is discussed. Notes on the natural history of Lipoptilocnema species are provided, and their potential importance as PMI indicators is highlighted, including the first record of Lipoptilocnema reared from a dead human body.
A new species of phlebotomine sand fly, Psathyromyia elizabethdorvalae sp. n. Brilhante, Sábio & Galati from Xapuri, Acre state, Brazil, is described, with illustrations of male and female adults.
The chigger mite genus Blankaartia includes 28 known species, of which 10 are distributed in the Nearctic and Neotropical regions. These species preferentially parasitize birds, but occasionally they can also be found on rodents, bats, and reptiles, showing low host selectivity. In the present study, we report the presence of this genus in Brazil for the first time, including the first report of Blankaartia sinnamaryi (Floch and Fauran) and the description of a new species of Blankaartia collected from birds (Order Passeriformes).
Simulium (Gomphostilbia) maleewongae sp. nov. is described based on the adult males and females, their pupal exuviae, and larvae from Thailand. This new species is placed in the Simulium gombakense species-group of Simulium (Gomphostilbia). It is characterized by the female cibarium with a cup-like appendage, male ventral plate deeply depressed ventromedially, pupal gill composed of an inflated structure and eight slender filaments, cone-shaped pupal terminal hooks, and cocoon with an anterodorsal projection. Taxonomic notes are given to separate this new species from 10 other species of the same species-group known from China, India, Malaysia, Thailand, Nepal, and Vietnam. Keys to identify all 11 species of the S. gombakense species-group are provided for females, males, pupae, and larvae.
Caves are unique habitats that are inhabited by a diverse and singular biota. Among these inhabitants are sand flies, which are of great epidemiological interest in the Neotropical region because they are vectors of Leishmania. The period of activity of these insects is usually crepuscular and nocturnal, but there are reports of diurnal activity of sand flies in caves. Thus, the aim of this study was to evaluate the periodicity of daily activity of sand flies in cave environments in the municipality of Pains, Minas Gerais. Sand flies were collected with light traps, which were operated for 5 consecutive days in the rainy season and in the dry season. Samples were collected every 12 h and separated between photophase and scotophase periods. In total, 1,777 sand flies of 23 species were collected. The most abundant species was Lutzomyia renei (Martins, Falcão, and Silva) (44%), followed by Lutzomyia longipalpis (Lutz and Neiva) (15%), Evandromyia edwardsi (Mangabeira) (11%), and Micropygomyia quinquefer (Costa Lima) (6%). The richness and abundance of total sand flies and the abundance of male and female sand flies in the aphotic zone of the caves did not differ between the photophase and scotophase, but differed between photoperiods at the entrance and at sites surrounding the caves. From our study of the daily activity of these insects in this ecotope, it will be possible to know which period of the day is of greatest risk of exposure of vertebrates who visit or live in these environments, including the human population.
In temperate regions, the seasonal dynamics of Aedes aegypti (L.) (Diptera: Culicidae) is mainly influenced by temperature. It is assumed that, during the winter season, the population remains as eggs and that the development and population growth of surviving eggs begin during the following spring. The aim of the current study was to assess egg hatching of Ae. aegypti during the winter in Buenos Aires city (Argentina), and analyze the survival of immature stages. The experiments consisted of immersing eggs and studying the development of immature stages of cohorts from June and September under natural temperature conditions. The proportion of hatched eggs was compared between weeks of immersion and related to environmental variables. Survival was compared among cohorts and the development rate was related to the mean temperature during development. The results showed that, with few exceptions, egg hatching was over 45% during the winter period. The proportion of hatched eggs was positively associated with immersion temperature, pre-immersion temperature and photoperiod. The immature stages completed the development during the cold season, with a trend toward increased survival of late-hatching cohorts. Survival was 30% at 13.2 °C and above 90% at 20 °C, whereas the development time at low temperatures was 49.4 d at 13.2 °C and 17.7 d at 20 °C. The high hatching and survival compared with other studies suggest that the local population might be adapting to winter conditions. The anticipated emergence of adults would be adaptive if they are able to reproduce successfully in the early spring.
Recording the nycthemeral rhythm of sand flies allows the evaluation of the daily activity in different ecotypes, the period of greatest activity, and their degree of anthropophily. We investigated the fauna and the rhythm of sand fly activity in an ecotourism region in Mato Grosso do Sul (MS) state, Brazil. Sand flies were captured monthly, using a Shannon trap for 24 h periods between July 2012 and June 2014. We collected 1,815 sand flies, in which Lutzomyia whitmani (=Nyssomyia whitmani, sensu Galati) and Lutzomyia longipalpis were the most abundant species during the dry season, with activity from 5 p.m.–7 a.m. and 6 p.m.–5 a.m., respectively. Both species require particular attention as vectors of Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum in several regions of Brazil, including MS. However, Lutzomyia dispar was more anthropophilic, and was most active between January and March, from 5 p.m. to 5 a.m. Lutzomyia misionensis (=Pintomyia misionensis, sensu Galati) was present throughout both years, active from 4 p.m. to 5 a.m. Other species were active from 5 p.m. to 6 a.m. Due to intense tourism in the months that coincide with a high number of vectors for leishmaniases in Piraputanga, it is essential to determine vector-monitoring strategies in the area by investigating sand fly rhythm while not neglecting other periods of the year when the insects are present.
Local knowledge of when humans are at elevated risk for exposure to tick vectors of human disease agents is required both for the effective use of personal protection measures to avoid tick bites and for implementation of control measures to suppress host-seeking ticks. Here, we used previously published data on the seasonal density of host-seeking Ixodes pacificus Cooley and Kohls nymphs, the primary vectors of Lyme disease spirochetes in the far western USA, collected across a broad habitat and climate gradient in northwestern California to identify predictors of periods of time within the year when questing nymphal density is elevated. Models based on calendar week alone performed similarly to models based on calendar week and woodland type, or meteorological variables. The most suitable model for a given application will depend on user objectives, timescale of interest, and the geographic extent of predictions. Our models sought not only to identify when seasonal host-seeking activity commences, but also when it diminishes to low levels. Overall, we report a roughly 5–7 month period in Mendocino County during which host-seeking nymphal densities exceed a low threshold value.
Previous published evidence for the occurrence of an exotic armadillo tick, Amblyomma auricularium (Conil), in Florida is scant, but we found it is fully established and integrated into the state's tick fauna. We collected 11,192 specimens of this tick from naturalized nine-banded armadillos, Dasypus novemcinctus L., and 14 other species of wild native mammals and birds in Florida, while sampling statewide during 2004 through 2007. In all, we document its specific presence only in 14 contiguous South Florida counties. Moreover, we report the first collections of A. auricularium from the Virginia opossum (Didelphis virginiana Kerr), common raccoon [Procyon lotor (L.)], cotton deermouse [Peromyscus gossypinus (Le Conte)], gray fox [Urocyon cinereoargenteus (Schreber)], eastern spotted skunk [Spilogale putorius (L.)], and white-tailed deer [Odocoileus virginianus (Zimmerman)]. For the first time on birds, we report the collection of this tick from the broad-winged hawk [Buteo platypterus (Vieillot)], northern cardinal [Cardinalis cardinalis (L.)], Carolina wren [Thryothorus ludovicianus (Latham)], gray catbird [Dumetella carolinensis (L.)], and yellow-rumped warbler [Setophaga coronata (L.)]. In addition, we report unattached A. auricularium collected from humans for the first time, and additional new collections from domestic dogs, Canis lupus familiaris L.
Vector Control, Pest Management, Resistance, Repellents
Critical to successful application of the sterile insect technique against Aedes albopictus (Skuse) is the development of an efficient and standardized rearing protocol to be employed in the mass production system. In this study, several life history traits of Ae. albopictus were analyzed to identify upper and lower thresholds of larval density and diet concentration. Survival to pupation, time to pupation, and sex ratio were evaluated under a range of larval densities (0.5–5 larvae/ml) and food levels (0.05–1.6 mg/larva/d) using two larval diets (one locally developed; one developed by the FAO/IAEA). The larvae reared at 28 °C, at a density of 2 larvae/ml and receiving a food dose equal to 0.6 mg/larva/d of a diet consisting of 50% tuna meal, 50% bovine liver powder (the FAO/ IAEA diet), and, as an additive, 0.2 g of Vitamin Mix per 100 ml of diet solution, developed in 5 d and had 90% survival to the pupal stage. With this rearing regime male pupae production 24 h after the onset of pupation was the highest; these pupae were ∼94% male.
One essential oil (clove oil), one skin repellent (icaridin), and one insecticide (transfluthrin) were tested for spatial repellent effects against non-blood-fed female Aedes aegypti (L.) mosquitoes. The compounds were tested in acetone dilution series using a Y-olfactometer, a double cage system, and a double room system. All compounds exhibited spatial repellent effects at certain concentrations. Clove oil required relative high dosages to cause high effects (Y-olfactometer 6 mg, double cage 60 mg, and double room 1,200 mg). The dosages to achieve comparable results with icaridin were lower (Y-olfactometer and double cage 1 mg, and double room 150 mg). For transfluthrin, the equivalent dosages were lower again (Y-olfactometer 0.003 mg, double cage 0.03 mg, and double room 0.1 mg). Furthermore, these results reveal a correlation between the size of the test system and the effective dosage. Averaged for the three compounds, the quantity for the double room was 21-fold higher than for the double cage, which required again a 9-fold higher dosage than the Y-olfactometer. An establishment of a screening cascade is discussed starting with the Y-olfactometer (high throughput rate), followed by the double cage system and ending with the double room system as the most nearest to practical conditions. Furthermore, the testing of existing repellent products to validate the double room test, the role of sublethal dosages concerning insecticides including possible upcoming of resistance after exposure, the delayed action and impact on blood feeding and oviposition are exemplified.
Aedes aegypti L. (Diptera: Culicidae) is a mosquito species that has adapted to urban environments and is the main vector of dengue viruses. Because of the increasing incidence of dengue, a more environmentally acceptable insecticide needs to be found. Natural products have been and continue to be an important source of leading compounds that can be modified in order to develop new drugs. The lignan family of natural products includes compounds with a diverse spectrum of biological activity. Podophyllotoxin and its related lignans represent an exciting class of natural products that can be targeted at different types of biological activity and are therefore worth exploring further. This study had the aim of evaluating the larvicidal activity of an ethanolic extract from the rhizomes and roots of Podophyllum hexandrum (PM-3) and its isolated lignans, podophyllotoxone (1) and desoxypodophyllotoxin (2), on the larvae of the mosquito vector Ae. aegypti. The PM-3 extract and the compounds (1) and (2) were dissolved in a mixture of acetone and dimethylsulfoxide at final concentrations of 1, 10, 30, 50, 100, and 200 μg/ml. After dilution, the solutions were applied (μg/ml) to the larvae-rearing medium. Overall, the ethanolic extract from the rhizomes and roots of P. hexandrum and the compounds (1) and (2) showed larvicidal activity against the larvae of Ae. aegypti. According to the results from this study, it can be concluded that podophyllotoxone (1) and desoxypodophyllotoxin (2) exhibited significant toxicity toward Ae. aegypti larvae.
Studies were undertaken to determine the ovicidal efficacy of 5,5′-dimethyl-2,2′ -bipyridyl (abametapir) against eggs of both human head and body lice. Head lice eggs of different ages (0–2, 3–5, and 6–8-d-old eggs) were exposed to varying concentrations of abametapir in isopropanol and concentration-dependent response relationships established based on egg hatch. One hundred percent of all abametapir-treated eggs failed to hatch at the 0.74 and 0.55% concentrations, whereas 100% of 6–8-d-old head louse eggs failed to hatch only at the 0.74% concentration. The LC50 value for abametapir varied, depending on the age of the head lice eggs, from ∼0.10% recorded for 0–2-d-old eggs and increasing to ∼0.15% for 6–8-d-old eggs. Abametapir was also evaluated once formulated into a lotion referred to as Xeglyze (0.74% abametapir) and serial dilutions made. Ovicidal efficacies were determined against head lice eggs 0–8-d-old. Results indicated 100% ovicidal activity at the 0.74, 0.55, 0.37, and 0.18% concentrations. Additional studies undertaken using body lice eggs also demonstrated that abametapir was 100% ovicidal against eggs of all ages when evaluated at a concentration of 0.37 and 0.55%. Given that ovicidal activity is a critical component of any effective treatment regime for louse control, the data presented in this study clearly demonstrate the ability of abametapir to inhibit hatching of both head and body louse eggs as assessed in vitro.
The horn fly, Haematobia irritans (L.) (Diptera: Muscidae), is one of the most important pests of the beef cattle industry. Horn fly adults are blood feeders that remain in constant contact with cattle, providing management opportunities via insecticide-impregnated ear tags. Controlling horn flies in the United States is time consuming and costly, but failure to implement management can lead to weight loss and decreased weight gain of calves and yearlings. In the past decade, new chemical combinations have been impregnated into ear tags for pest management. The objectives of this project were to 1) evaluate the efficacy of ear tags against horn fly populations and 2) determine if reduced fly density results in economic return. During 2013, data were compiled by insecticide class; treated cows averaged fly reductions of 198 (s = 38.91; n = 3) for macrocyclic lactone treatments, 175 (s = 62.74; n = 4) for pyrethroid treatments, and 174 (s = 35.28; n = 8) for organophosphate treatments compared with untreated animals (214; s = 50.38; n = 9). During 2014, mean fly reductions were 187 (s = 14.15; n = 4) for macrocyclic lactone, 147 (s = 61.41; n = 13) for pyrethroid, and 143 (s = 77.16; n = 8) for organophosphate treatments relative to the untreated (200; s = 99.83; n = 14). A novel technology, the VetGun application system, tested in 2014, resulted in fly reductions (121 ±, n = 4), but means were not statistically significant from the control (200; s = 99.83; n = 14). Treatment of cattle with ear tags significantly reduced horn fly numbers compared with untreated cattle.
The essential oils of kaffir lime (Citrus hystrix DC.) at four different concentrations (0.5, 1.0, 2.5, and 5.0% v/v) were studied for their repellency, excitation, and knockdown properties against laboratory strains of Aedes aegypti (L.) and Anopheles minimus Theobald using an excito-repellency test system. Both contact and noncontact escape responses to leaf- and peel-derived kaffir lime oils were observed. Comparing unadjusted escape responses for An. minimus, leaf oil had strong combined irritant and repellent activity responses at 1–5% concentrations (90.0–96.4% escape) and the strongest spatial repellent activity at 1% and 2% (85.9% and 87.2% escape, respectively). The peel oil exhibited good excitation with repellency at concentrations of 2.5% (89.8% escape) and 5% (96.28% escape), while concentrations 1–5% showed more moderate repellent activity against An. minimus. For Ae. aegypti, 2.5% leaf oil produced the greatest response for both contact (56.1% escape) and noncontact (63.3% escape) trials, while 2.5% produced the strongest response among all concentrations of peel oil, with 46.5% escape. However, after adjusting the contact trial escape (a measure of combined excitation and repellency), the estimated escape due to contact alone was a much weaker response than spatial repellency for both species. Knockdown responses above 50% were only observed in Ae. aegypti exposed to 5% leaf oil. Kaffir lime oils were more active against An. minimus than Ae. aegypti mosquitoes. There were statistically significant differences between leaf (more active) and peel oils at each concentration against An. minimus in contact and noncontact trials, except at the highest (5%) concentration.
Pablo L. Santo-Orihuela, Claudia V. Vassena, Guillermo Carvajal, Eva Clark, Silvio Menacho, Ricardo Bozo, Robert H. Gilman, Caryn Bern, Paula L. Marcet
A wide range of insecticide resistance profiles has been reported across Bolivian domestic and sylvatic populations of Triatoma infestans (Klug, 1834) (Hemiptera, Reduviidae), including some with levels proven to be a threat for vector control. In this work, the insecticide profile of domestic T. infestans was studied with standardized toxicological bioassays, in an area that has not undergone consistent vector control. F1 first-instar nymphs hatched in laboratory from bugs captured in three communities from the Santa Cruz Department were evaluated with different insecticides. Moreover, the enzymatic activity of esterases and cytochrome P450 monooxygenases was measured in individual insects to evaluate the possible mechanism of metabolic resistance to pyrethroids. In addition, the DNA sequence of sodium channel gene (kdr) was screened for two point mutations associated with pyrethroid resistance previously reported in T. infestans.
All populations showed reduced susceptibility to deltamethrin and a-cypermethrin, albeit the RR50 values varied significantly among them. Increased P450 monooxygenases and permethrate esterases suggest the contribution, as detoxifying mechanisms, to the observed resistance to deltamethrin in all studied populations. No individuals presented either mutation associated to resistance in the kdr gene. The level of susceptibility to a-cypermethrin, the insecticide used by the local vector control program, falls within an acceptable range to continue its use in these populations. However, the observed RR50 values evidence the possibility of selection for resistance to pyrethroids, especially to deltamethrin. Consequently, the use of pyrethroid insecticides should be closely monitored in these communities, which should be kept under entomological surveillance and sustained interventions.
Leishmania spp. are distributed throughout the world, and different species are associated with varying degrees of disease severity. In Brazil, Leishmania transmission involves several species of phlebotomine sand flies that are closely associated with different parasites and reservoirs, and thereby giving rise to different transmission cycles. Infection occurs during the bloodmeals of sand flies obtained from a variety of wild and domestic animals, and sometimes from humans. The present study focused on detection of Leishmania DNA in phlebotomine sand flies from a cave in the state of Minas Gerais. Detection of Leishmania in female sand flies was performed with ITS1 PCR-RFLP (internal transcribed spacer 1) using HaeIII enzyme and genetic sequencing for SSUrRNA target. The survey of Leishmania DNA was carried out on 232 pools and the parasite DNA was detected in four: one pool of Lutzomyia cavernicola (Costa Lima, 1932), infected with Le. infantum (ITS1 PCR-RFLP), two pools of Evandromyia sallesi (Galvão & Coutinho, 1939), both infected with Leishmania braziliensis complex (SSUrRNA genetic sequencing analysis), and one pool of Sciopemyia sordellii (Shannon & Del Ponte, 1927), infected with subgenus Leishmania (SSUrRNA genetic sequencing analysis). The present study identified the species for Leishmania DNA detected in four pools of sand flies, all of which were captured inside the cave. These results represent the first molecular detection of Lu. cavernicola with Le. infantum DNA, Sc. sordellii with subgenus Leishmania DNA, and Ev. sallesi with Leishmania braziliensis complex DNA. The infection rate in females captured for this study was 0.17%.
Kacey C. Ernst, Kathleen R. Walker, Pablo Reyes-Castro, Teresa K. Joy, A. Lucia Castro-Luque, Rolando E. Diaz-Caravantes, Mercedes Gameros, Steven Haenchen, Mary H. Hayden, Andrew Monaghan, Eileen Jeffrey-Guttierez, Yves Carrière, Michael R. Riehle
Dengue virus, primarily transmitted by the Aedes aegypti (L.) mosquito, has rapidly expanded in geographic extent over the past several decades. In some areas, however, dengue fever has not emerged despite established Ae. aegypti populations. The reasons for this are unclear and have sometimes been attributed to socioeconomic differences. In 2013 we compared Ae. aegypti adult density and population age structure between two cities in Sonora, Mexico: Hermosillo, which has regular seasonal dengue virus transmission, and Nogales, which has minimal transmission. Larval and pupal abundance was greater in Nogales, and adult density was only higher in Hermosillo during September. Population age structure, however, was consistently older in Hermosillo. This difference in longevity may have been one factor that limited dengue virus transmission in Nogales in 2013, as a smaller proportion of Ae. aegypti females survived past the extrinsic incubation period.
Blood and tick samples were collected from 333 apparently healthy sheep and 257 goats as well as 10 sheep exhibiting clinical signs of babesiosis in Adana, Gaziantep, and Adiyaman Provinces in southern Turkey. Fully engorged female ticks were selected and maintained in an incubator until they oviposited. The tick carcasses and their egg masses were examined. Piroplasms compatible with Babesia spp. and Theileria spp. were observed in both symptomatic and asymptomatic small ruminants. Genomic DNA isolates from blood of ovine, tick samples, and egg masses were screened for piroplasms by utilizing 18S rRNA polymerase chain reaction and reverse line blotting (RLB) assays. Parasitemia ranged from 0.01% to 5.6% of erythrocytes in clinical cases. RLB showed positivity in 239 (40.5%) of the sampled apparently healthy sheep and goats and revealed the presence of three Theileria and one Babesia species. Theileria ovis was the most prevalent (35.4%), followed by Babesia ovis (5.4%), Theileria annulata (3.9%), and Theileria sp. MK (0.3%). Thirty-two small ruminants infected with T. ovis were also infected with B. ovis. One animal infected with T. ovis was also infected with Theileria sp. MK. Ticks were identified as Rhipicephalus bursa, Rhipicephalus turanicus, Hyalomma excavatum, Haemaphysalis parva, and Hyalomma anatolicum. Egg masses of two female R. bursa carcasses were infected with B. ovis. This is the first report of theileriosis caused by T. annulata in sheep and goats in Turkey.
Adult mosquito surveillance and field trials evaluated selected commercially available ultraviolet black-light (BL) and light-emitting diode (LED) traps at three sites where vivax malaria is endemic from May to October 2015 in northwestern Republic of Korea. Collections totaled 283,929 adult mosquitoes (280,355 [98.74%] females and 3,574 [1.26%] males) comprising 17 species (including six members of the Anopheles Hyrcanus Group) belonging to six genera. The four most predominant female species collected were Aedes vexans nipponii (Theobald) (83.84%), followed by Anopheles Hyrcanus Group (13.66%), Culex pipiens Group (1.67%), and Culex tritaeniorhynchus Giles (0.54%). Overall, LED traps (188,125) collected significantly more female mosquitoes compared with BL traps (92,230; P = 0.0001, P < 0.05). Results from these field evaluations significantly enhance vector and disease surveillance efforts, especially for the primary vectors of malaria (Anopheles Hyrcanus Group) and Japanese encephalitis (Cx. tritaeniorhynchus).
In Brazil, American cutaneous leishmaniasis (ACL) ecology involves a diversity of Leishmania species transmitted by different sand fly species. Workers involved in agricultural activities are those mainly affected by ACL in some regions from Tocantins State (TO), Brazil, where the disease can be established in new settlements. The objective of this study was to examine the seasonal and hourly frequency of sand fly species, focusing on the potential vectors of ACL, in a settlement in Guaraí (TO), an ACL transmission area. Sand flies were captured in forested area close to Pedra Branca Agricultural Project settlement, from March 2006 until December 2007, using Shannon trap. Monthly captures were made from 06:00 p.m. to 10:00 p.m., and 24-h captures were done twice per semester, from 06:00 a.m. to 06:00 a.m. A total of 10,089 specimens from 30 species were identified. Psychodopygus complexus Mangabeira, Psychodopygus llanosmartinsi Fraiha & Ward, and Nyssomyia antunesi Coutinho were the most abundant species. Nyssomyia antunesi was more frequent during the dry period, whereas Ps. complexus and Ps. llanosmartinsi had high frequencies during the rainy season. Precipitation was positively correlated with Ps. complexus and Ps. llanosmartinsi abundance, and negatively correlated with Ny. antunesi. During 24-h captures, the majority of specimens were captured during the night followed by a decrease at dawn. The behavior and previous finding of natural infection by Leishmania (Viannia) braziliensis of Ps. complexus led us to the conclusion that this species can be a potential vector of L. (V.) braziliensis during the rainy season in Guaraí.
Studies were conducted to determine if pyriproxyfen, an insect growth regulator (IGR) added to attractive toxic sugar baits (ATSBs) and ingested by adult Aedes albopictus (Skuse), could be fecally disseminated into water to inhibit emergence of mosquitoes (EI). Experimental treatments consisted of four dilutions of pyriproxyfen (0.5, 1, 5, and 10 ppb) in ATSB, with attractive sugar bait (ASB) serving as the negative control. To ensure no tarsal transfer of the IGR, the experimental treatments were dispensed in collagen sausages. Mosquito excrement was collected on card stock at the bottom of the mosquito cages at 1, 4, 6, and 8 h during the study. There were no differences between the EI times at which the fecal cards were collected (F19,88 = 1.8, P = 0.1592). The highest dilution of pyriproxyfen in ATSB (10 ppb) inhibited mosquito emergence in the most amounts (57%), as compared with the EI of other pyriproxyfen dilutions: 0.5 ppb = 42%, 1 ppb = 34%, and 5 ppb = 46% (F19,88 = 1.8, P = 0.1592). This study demonstrates that pyriproxyfen can be fecally disseminated into water and control larvae through adult mosquito ingestion and excretion of pyriproxyfen in ASB.
Borrelia mayonii, a recently recognized species within the Borrelia burgdorferi sensu lato complex, has been detected in host-seeking Ixodes scapularis Say ticks and found to be associated with Lyme disease in the Upper Midwest. This spirochete has, to date, not been documented from the Northeast, but we previously demonstrated that I. scapularis ticks originating from Connecticut are capable of serving as a vector of B. mayonii. In this follow-up study, we compared the vector efficiency for B. mayonii (strain MN14-1420) of I. scapularis ticks originating from Minnesota in the Upper Midwest and Connecticut in the Northeast. CD-1 outbred white mice previously infected with B. mayonii via tick bite were exposed to simultaneous feeding by Minnesota and Connecticut larvae contained within separate feeding capsules. We found no difference in the ability of Minnesota and Connecticut larvae to acquire B. mayonii from infected mice and pass spirochetes to the nymphal stage (overall nymphal infection rates of 11.6 and 13.3%, respectively). Moreover, the efficiency of transmission of B. mayonii by single infected nymphs was similar for the Minnesota and Connecticut ticks (33 and 44%, respectively). We conclude that the examined I. scapularis ticks from the Upper Midwest and Northeast did not differ in their efficiency as vectors for B. mayonii.
The genus Borrelia includes species responsible for severe human diseases such as Lyme disease. Birds are involved in their epidemiology as dispersers of infected ticks (Ixodida: Ixodidae) and as reservoirs or amplifiers of the bacterium. Herein, the presence of Borrelia burgdorferi sensu lato (s.l.) Johnson, Schmid, Hyde, Steigerwalt & Brenner in 336 ticks collected from birds in the north of Spain from 2009 to 2011 was investigated. Nucleic acid extracts from 174 Ixodes frontalis (Panzer), 108 Haemaphysalis punctata Canestrini & Fanzango, 34 Hyalomma marginatum Koch, 17 Ixodes ricinus (L.), and 3 Ixodes spp. were screened for the presence of B. burgdorferi s.l. by PCR. Borrelia turdi was detected in 22 I. frontalis, 2 H. punctata, and 2 I. ricinus. Additionally, 1 I. frontalis and 1 H. punctata were found to be infected with the human pathogen Borrelia valaisiana. Moreover, 3 I. frontalis showed coinfection with both Borrelia species. This study corroborates the presence of B. turdi and B. valaisiana in ticks from birds in the north of Spain. The presence of these bacteria in larval specimens could suggest the role of birds as their reservoirs, or the occurrence of the cofeeding phenomenon. In addition, the detection of B. turdi and B. valaisiana in H. punctata and I. frontalis ticks, respectively, is reported for the first time.
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