Showing papers in "Journal of Medical Entomology in 2013"
TL;DR: Arthropod development can be used to determine the time of colonization of human remains to infer a minimum postmortem interval and it is necessary to understand black soldier fly development on different food resources to properly estimate their age when recovered from human remains.
Abstract: Arthropod development can be used to determine the time of colonization of human remains to infer a minimum postmortem interval. The black soldier fly, Hermetia illucens L. (Diptera. Stratiomyidae) is native to North America and is unique in that its larvae can consume a wide range of decomposing organic material, including carrion. Larvae development was observed on six resources: control poultry feed, liver, manure, kitchen waste, fruits and vegetables, and fish rendering. Larvae fed manure were shorter, weighed less, and took longer to develop. Kitchen waste produced longer and heavier larvae, whereas larvae fed fish had almost 100% mortality. Black soldier flies can colonize human remains, which in many instances can coincide with food and organic wastes. Therefore, it is necessary to understand black soldier fly development on different food resources other than carrion tissue to properly estimate their age when recovered from human remains.
204 citations
TL;DR: It is demonstrated that phenotypic plasticity varies across populations of black soldier flies and should be taken into account when selecting and establishing a population as a waste management agent in a given region of the world.
Abstract: Black soldier flies, Hermetia illucens L., are distributed throughout the temperate and tropic regions of the world and are known an established method for sustainably managing animal wastes. Colonies used to conduct research on the black soldier fly within the past 20 yr have predominately been established from eggs or larvae received from a colony originated from Bacon County, GA. Consequently, little is known about the phenotypic plasticity (i.e., development and waste conversion) across strains from different regions. This study compared the development of three strains of the black soldier fly (Texas; Guangzhou, China; and Wuhan, China) and their ability to reduce dry matter and associated nutrients in swine, dairy, and chicken manure. The Wuhan strain appeared to be more fit. Larvae from Wuhan needed 17.7–29.9% less time to reach the prepupal stage than those from Guangzhou or Texas, respectively. Larvae from Wuhan weighed 14.4–37.0% more than those from Guanghzhou or Texas, respectively. Larvae from the Wuhan strain reduced dry matter 46.0% (swine), 40.1% (dairy), and 48.4% (chicken) more than the Guangzhou strain and 6.9, 7.2, and 7.9% more than the Texas strain. This study demonstrates that phenotypic plasticity (e.g., development and waste conversion) varies across populations of black soldier flies and should be taken into account when selecting and establishing a population as a waste management agent in a given region of the world.
160 citations
TL;DR: It is estimated that the minimum egg sterility value of 81% should be maintained to obtain suppression of the local population of Aedes albopictus in Emilia-Romagna region, northern Italy.
Abstract: The pilot field studies here presented are part of a long-term research program aimed to develop a cost-effective sterile insect technique (SIT) methodology to suppress Aedes albopictus (Skuse) populations. Aedes albopictus is a mosquito species mainly developing in man-made containers and with an island-like urban and suburban distribution. These two features make the application of the sterile insect technique a possible control strategy. Five trials have been performed in three small towns from 2005 to 2009 (Emilia-Romagna region, northern Italy). Reared male pupae, sexed by a sieving technique allowing the recovery of ≈26–29% of males, were exposed to gamma rays and immediately released in the field. Adult population density was estimated based on a weekly monitoring of egg density in the ovitraps, whereas induced sterility was estimated by measuring the hatching percentage of weekly collected eggs in SIT and control areas. Results showed that sterile males released at the rate of 896–1,590 males/ha/wk induced a significant sterility level in the local population. In addition, when the sterility level achieved values in the range of 70–80%, a similar reduction also was found for the egg density in the ovitraps. We could estimate that the minimum egg sterility value of 81% should be maintained to obtain suppression of the local population. Immigration of mated females was not a main issue in the small villages where trials have been run.
159 citations
TL;DR: There is a negative impact of large diurnal temperature range on mosquito biology and this is consistent with the hypothesis that, in at least some locations, large temperature fluctuations contribute to seasonal reduction in dengue virus transmission.
Abstract: Seasonal variation in dengue virus transmission in northwestern Thailand is inversely related to the magnitude of diurnal temperature fluctuations, although mean temperature does not vary significantly across seasons. We tested the hypothesis that diurnal temperature fluctuations negatively influence epidemiologically important life-history traits of the primary dengue vector, Aedes aegypti (L.), compared with a constant 26°C temperature. A large diurnal temperature range (DTR) (≈18°C daily swing) extended immature development time (>1 d), lowered larval survival (≈6%), and reduced adult female reproductive output by 25% 14 d after blood feeding, relative to the constant 26°C temperature. A small DTR (≈8°C daily swing) led to a negligible or slightly positive effect on the life history traits tested. Our results indicate that there is a negative impact of large DTR on mosquito biology and are consistent with the hypothesis that, in at least some locations, large temperature fluctuations contribute to seasonal reduction in dengue virus transmission.
134 citations
TL;DR: Substantial variability in necrophagous communities and assembly on carrion over decomposition and among seasons is demonstrated, recognizing this variation has important consequences for forensic entomology and future efforts to provide error rates for estimates of the postmortem interval using arthropod succession data as evidence during criminal investigations.
Abstract: Necrophagous invertebrates have been documented to be a predominant driver of vertebrate carrion decomposition; however, very little is understood about the assembly of these communities both within and among seasons. The objective of this study was to evaluate the seasonal differences in insect taxa composition, richness, and diversity on carrion over decomposition with the intention that such data will be useful for refining error estimates in forensic entomology. Sus scrofa (L.) carcasses (n = 3-6, depending on season) were placed in a forested habitat near Xenia, OH, during spring, summer, autumn, and winter. Taxon richness varied substantially among seasons but was generally lower (1-2 taxa) during early decomposition and increased (3-8 taxa) through intermediate stages of decomposition. Autumn and winter showed the highest richness during late decomposition. Overall, taxon richness was higher during active decay for all seasons. While invertebrate community composition was generally consistent among seasons, the relative abundance of five taxa significantly differed across seasons, demonstrating different source communities for colonization depending on the time of year. There were significantly distinct necrophagous insect communities for each stage of decomposition, and between summer and autumn and summer and winter, but the communities were similar between autumn and winter. Calliphoridae represented significant indicator taxa for summer and autumn but replaced by Coleoptera during winter. Here we demonstrated substantial variability in necrophagous communities and assembly on carrion over decomposition and among seasons. Recognizing this variation has important consequences for forensic entomology and future efforts to provide error rates for estimates of the postmortem interval using arthropod succession data as evidence during criminal investigations.
125 citations
TL;DR: It was found that multiple feeding and host-seeking behavior were negatively correlated with body size, i.e., small mosquitoes tended to have more contact with hosts, and multiple feeding increased fecundity.
Abstract: The body size of mosquitoes can influence a number of bionomic factors, such as their blood-feeding ability, host attack rate, and fecundity. All of these traits are important determinants of their potential to transmit diseases. Among abiotic and biotic factors, high temperature and low nutrition in the developing stages of mosquitoes generally result in small adults. We studied the relationship between body size and multiple feeding in a gonotrophic cycle and some fecundity attributes by using three strains of two competent vector species, Aedes aegypti (L.) and Aedes albopictus (Skuse). We raised small and large mosquitoes under low and high food conditions in the laboratory to measure parameters of fecundity and blood-feeding behavior. Fecundity was positively correlated with body size in both species, whereas the number of bloodmeals, the frequency of host-seeking behavior, and egg retention were negatively correlated with body size in the Ae. albopictus Nagasaki strain. We found that multiple feeding and host-seeking behavior were negatively correlated with body size, i.e., small mosquitoes tended to have more contact with hosts. We found that two mechanisms that inhibit engorged mosquitoes from seeking out hosts, distension-induced and oocyte-induced inhibition, were not strong enough to limit host-seeking behavior, and multiple feeding increased fecundity. Size-dependent multiple feeding and host-seeking behavior affect contact frequency with hosts and should be considered when predicting how changes in mosquito body size affect disease transmission.
123 citations
TL;DR: A first step toward assessing the future threat this mosquito poses to human health in the continental United States is to design and conduct studies across strategic climatic and socioeconomic gradients in the United States to determine the permissiveness of the coupled natural and human environment for Ae.
Abstract: After more than a half century without recognized local dengue outbreaks in the continental United States, there were recent outbreaks of autochthonous dengue in the southern parts of Texas (2004–2005) and Florida (2009–2011). This dengue reemergence has provoked interest in the extent of the future threat posed by the yellow fever mosquito, Aedes (Stegomyia) aegypti (L.), the primary vector of dengue and yellow fever viruses in urban settings, to human health in the continental United States. Ae. aegypti is an intriguing example of a vector species that not only occurs in the southernmost portions of the eastern United States today but also is incriminated as the likely primary vector in historical outbreaks of yellow fever as far north as New York, Philadelphia, and Boston, from the 1690s to the 1820s. For vector species with geographic ranges limited, in part, by low temperature and cool range margins occurring in the southern part of the continental United States, as is currently the case for...
115 citations
TL;DR: Bacteria diversity classified across all life stages spanned six bacterial phyla with >80% bootstrap support and Bacteroidetes and Proteobacteria were the most dominant phyla associated with the black soldier fly accounting for two-thirds of the fauna identified.
Abstract: Sustainable methods for managing waste associated with people and animals have been proposed in the past. Black soldier sy, Hermetia illucens (L.), larvae represent one of the more promising methods. Larvae reduce dry matter, bacteria, offensive odor, and house sy populations. Prepupae can be used as feedstuff for livestock. However, it is not known if such a method results in the proliferation of potential pathogens. Although some bacterial species have been cultured and identiÞed from black soldier sy, a true appreciation of sy associated bacterial diversity is not known. Such information is needed to understand pathogen colonization on decomposing animal and plant waste in the presence of black soldier sy larvae as well as develop research strategies for maximizing the use of this sy to reduce waste without risking environmental harm. Using 454 sequencing, we surveyed bacterial diversity associated with successive life stages of the black soldier sy reared on plant material. Bacteria diversity classiÞed (99.8%) across all life stages spanned six bacterial phyla with 80% bootstrap support. Bacteroidetes and Proteobacteria were the most dominant phyla associated with the black soldier sy accounting for two-thirds of the fauna identiÞed. Many of these bacteria would go undetected because of their inability to be cultured.
96 citations
TL;DR: Temephos and deltamethrin resistance in larvae were associated with high esterase activity, but not to cytochrome P450 monooxygenase or GST activities, and alternative insecticides should be considered.
Abstract: Dengue (family Flaviridae, genus Flavivirus, DENV) and dengue hemorrhagic fever (DHF) are presently important public health problems in Costa Rica. The primary strategy for disease control is based on reducing population densities of the main mosquito vector Aedes aegypti (L.) (Diptera: Culicidae). This is heavily dependent on use of chemical insecticides, thus the development of resistance is a frequent threat to control program effectiveness. The objective of this study was to determine the levels of insecticide resistance and the metabolic resistance mechanisms involved in two Ae. aegypti strains collected from two provinces (Puntarenas and Limon) in Costa Rica. Bioassays with larvae were performed according to World Health Organization guidelines and resistance in adults was measured through standard bottle assays. The activities of beta-esterases, cytochrome P450 monooxygenases, and glutathione S-transferases (GST), were assayed through synergists and biochemical tests, wherein the threshold criteria for each enzyme was established using the susceptible Rockefeller strain. The results showed higher resistance levels to the organophosphate (OP) temephos and the pyrethroid deltamethrin in larvae. The efficacy of commercial formulations of temephos in controlling Ae. aegypti populations was 100% mortality up to 11 and 12 d posttreatment with daily water replacements in test containers. Temephos and deltamethrin resistance in larvae were associated with high esterase activity, but not to cytochrome P450 monooxygenase or GST activities. Adult mosquitoes were resistant to deltamethrin, and susceptible to bendiocarb, chlorpyrifos, and cypermethrin. Because temephos and deltamethrin resistance are emerging at the studied sites, alternative insecticides should be considered. The insecticides chlorpyrifos and cypermethrin could be good candidates to use as alternatives for Ae. aegypti control.
96 citations
TL;DR: Results demonstrated that reducing the radiation dose from 60 to 30 Gy increases males' competitiveness, and showed that radiation induces precociousness in adult male emergence.
Abstract: Mating competitiveness trials have been conducted in large net-screened enclosures (8 by 5 by 2.8 m) built in a natural shaded environment, in the summers of 2006, 2007, 2008, and 2009 in northern Italy. Aedes albopictus (Skuse) males were radio-sterilized by applying gamma radiations at doses in the range 30-60 Gy. Gamma radiation was administered to aged pupae at the rate of 2.3 Gy/min. Reared radiated males (originally collected in Rimini, Forli, Bologna, Matera, Pinerolo) and hybrid radiated males were tested against wild fertile males (originated from eggs collected in Rimini and Cesena) and reared fertile males, in multiple comparisons for mating competitiveness with reared or wild females. The ratio was kept constant at 100-100_100 (fertile males-radiated males_virgin females). Mating competitiveness was estimated through the calculation of the hatching rate of the eggs laid in oviposition traps positioned inside enclosures. No clear effect of the strains tested (reared, wild, or hybrid) was found. Results demonstrated that reducing the radiation dose from 60 to 30 Gy increases males' competitiveness. Laboratory investigations conducted after controversial results in the 2006 preliminary trials, showed that radiation induces precociousness in adult male emergence.
95 citations
TL;DR: Six essential oils showed significant synergistic effects with carbaryl at 10–50 mg/liter, but paradoxically all of them decreased the toxicity of permethrin against Ae.
Abstract: Phytochemicals have been considered as alternatives for conventional pesticides because of their low mammalian toxicity and environmental safety. They usually display less potent insecticidal effects than synthetic compounds, but may express as yet unknown modes of action. In the current study, we evaluated 14 plant essential oils for their toxicities and synergistic effects with carbaryl and permethrin against fourth instars of Aedes aegypti (L.) as well as 5-7-d-old adults. Six essential oils showed significant synergistic effects with carbaryl at 10-50 mg/liter, but paradoxically all of them decreased the toxicity of permethrin against Ae. aegypti larvae. None showed toxicity or synergistic effects on Ae. aegypti adults, at doses up to 2,000 ng/ insect. The six essential oils displaying synergistic effects in Ae. aegypti larvae inhibited the in vitro activities of cytochrome P450 monooxygenases and carboxylesterases in the low milligram per liter range. The data indicated that cytochrome P450 monooxygenases and carboxylesterase were probably targets for these natural synergists. Thus, the mechanism of synergism was most likely inhibition of metabolism and not interacting target site effects.
TL;DR: Both vertically and horizontally infected Culex females may persist through winter and possibly transmit WNV after diapause termination in late winter or early spring in the Sacramento Valley of California.
Abstract: At temperate latitudes, Culex (Diptera: Culicidae) mosquitoes typically overwinter as adult females in reproductive arrest and also may serve as reservoir hosts for arboviruses when cold temperatures arrest viral replication. To evaluate their role in the persistence of West Nile virus (WNV) in the Sacramento Valley of California, the induction and termination of diapause were investigated for members of the Culex pipiens (L.) complex, Culex tarsalis Coquillett, and Culex stigmatosoma Dyar under field, seminatural, and experimental conditions. All Culex spp. remained vagile throughout winter, enabling the collection of 3,174 females and 1,706 males from diverse habitats during the winters of 2010–2012. Overwintering strategies included both quiescence and diapause. In addition, Cx. pipiens form molestus Forskal females remained reproductively active in both underground and aboveground habitats. Some blood-fed, gravid, and parous Cx. tarsalis and Cx. pipiens complex females were collected throughout the winter period. Under both field and experimental conditions, Cx. tarsalis and Cx. stigmatosoma females exposed to autumnal conditions arrested primary follicular maturation at previtellogenic stage I, with primary to secondary follicular ratios <1.5 (indicative of a hormonally induced diapause). In contrast, most Cx. pipiens complex females did not enter reproductive diapause and ovarian follicles matured to ≥stage I–II (host-seeking arrest) or were found in various stages of degeneration. Diapause was initiated in the majority of Cx. tarsalis and Cx. stigmatosoma females by mid-late October and was terminated after the winter solstice, but host-seeking seemed limited by temperature. An accrual of 97.52 ± 30.7 and 162.85 ± 79.3 degree-days after the winter solstice was estimated to be necessary for diapause termination in Cx. tarsalis under field and seminatural conditions, respectively. An increase in the proportion of blood-fed Culex females in resting collections occurred concurrently with diapause termination in field populations based on ovarian morphometrics. WNV RNA was detected in one pool of 18 males and in a single blood-fed female Cx. tarsalis collected during winter. Therefore, both vertically and horizontally infected Culex females may persist through winter and possibly transmit WNV after diapause termination in late winter or early spring in the Sacramento Valley of California.
TL;DR: The IAEA 2 diet is found to be the preferred choice for mass rearing of Aedes albopictus, particularly if a sugar meal can be given to adult males before release, to ensure their teneral reserves are sufficient for survival, dispersal, and mating in the field.
Abstract: A fundamental step in establishing a mass production system is the development of a larval diet that promotes high adult performance at a reasonable cost. To identify a suitable larval diet for Aedes albopictus (Skuse), three diets were compared: a standard laboratory diet used at the Centro Agricoltura Ambiente, Italy (CAA) and two diets developed specifically for mosquito mass rearing at the FAO/IAEA Laboratory, Austria. The two IAEA diets, without affecting survival to the pupal stage, resulted in a shorter time to pupation and to emergence when compared with the CAA diet. At 24 h from pupation onset, 50 and 90% of the male pupae produced on the CAA and IAEA diets, respectively, had formed and could be collected. The diet received during the larval stage affected the longevity of adult males with access to water only, with best results observed when using the CAA larval diet. However, similar longevity among diet treatments was observed when males were supplied with sucrose solution. No differences were observed in the effects of larval diet on adult male size or female fecundity and fertility. Considering these results, along with the relative costs of the three diets, the IAEA 2 diet is found to be the preferred choice for mass rearing of Aedes albopictus, particularly if a sugar meal can be given to adult males before release, to ensure their teneral reserves are sufficient for survival, dispersal, and mating in the field.
TL;DR: The high rate of T. cruzi infection among triatomine specimens that were collected from inside houses, outside houses, and dog kennels suggests a current risk for Chagas disease vector-borne transmission for humans and domestic animals in residential settings in Texas because of overlap with the sylvatic cycle.
Abstract: The host-vector-parasite interactions in Chagas disease peridomestic transmission cycles in the United States are not yet well understood. Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) infection prevalence and bloodmeal sources were determined for adult and immature triatomine (Hemiptera: Reduviidae) specimens collected from residential settings in central Texas. Sequenced cytochrome b DNA segments obtained from triatomine digestive tract identified nine vertebrate hosts and one invertebrate host in four triatomine species (Triatoma gerstaeckeri, Triatoma indictiva, Triatoma protracta, and Triatoma sanguisuga). The broad range of wild and domestic host species detected in triatomine specimens collected from residential sites indicates high host diversity and potential movement between the sylvatic and peridomestic settings. Domestic dogs appear to be key in the maintenance of the peridomestic transmission cycle as both a blood host for the triatomine vectors and a potential reservoir for the parasite. The high rate of T. cruzi infection among triatomine specimens that were collected from inside houses, outside houses, and dog kennels (69, 81, and 82%, respectively) suggests a current risk for Chagas disease vector-borne transmission for humans and domestic animals in residential settings in Texas because of overlap with the sylvatic cycle.
TL;DR: In conclusion, the haplotypes found in free-ranging foxes are genetically closely related to pathogens of great veterinary importance, namely E. ruminantium and H. americanum, and it is highly desirable to know if these novel organisms have any important role as agents of diseases in domestic animals and wildlife in Brazil.
Abstract: This study evaluated infection by vector-borne agents in 58 crab-eating fox (Cerdocyon thous L.) that were road-killed in an Atlantic rainforest reserve in the state of Espirito Santo, southeastern Brazil. Spleen, lung, or blood samples collected from the foxes were tested in the laboratory by a battery of polymerase chain reaction (PCR) assays targeting bacteria of the genera Rickettsia, Borrelia, Coxiella, Anaplasma, and Ehrlichia; and protozoa of the genera Babesia, Hepatozoon, and Leishmania. Of the targeted organisms, evidence of infection in the foxes was detected for Ehrlichia and Hepatozoon organisms only. Overall, six (10.3%) foxes were infected by an ehrlichial agent closely related to an ehrlichial agent recently detected in free-ranging Jaguars [(Panthera onca (L.)] in central-western Brazil, and to Ehrlichia ruminantium. For Hepatozoon, 28 (48.3%) foxes were infected by an agent closely related to Hepatozoon sp. Curupira 2 and H. americanum; and one (1.7%) fox was infected by an organism closely related to reptile-associated Hepatozoon agents. Finally, 11 (19.0%) foxes were found infested by Amblyomma cajennense (F.) nymphs, which were all PCR negative for the range of vector-borne agents cited above. Because the haplotypes found in free-ranging foxes are genetically closely related to pathogens of great veterinary importance, namely E. ruminantium and H. americanum, it is highly desirable to know if these novel organisms have any important role as agents of diseases in domestic animals and wildlife in Brazil.
TL;DR: Twenty-nine species of mammals and three species of birds were identified as hosts for different life stages of these ticks and range expansion of D. variabilis has resulted in a zone of sympatry at least 200 km wide.
Abstract: Distributional ranges of the ticks Dermacentor andersoni Stiles and Dermacentor variabilis (Say) in the Canadian Prairies were determined by passive surveillance and active collection. These findings were compared with historical records of both species, particularly in the province of Saskatchewan, where the northern distributional limits of both tick species occur. Before the 1960s, D. variabilis and D. andersoni were allopatric in Saskatchewan; however, since then, the distribution of D. variabilis has expanded westward and northward. Although the range of D. andersoni has remained relatively stable, range expansion of D. variabilis has resulted in a zone of sympatry at least 200 km wide. Twenty-nine species of mammals and three species of birds were identified as hosts for different life stages of these ticks.
TL;DR: Results demonstrate that Florida Ae.
Abstract: Following the 2009 and 2010 dengue-1 (DENV-1) outbreaks in Key West, FL, we used Florida Aedes aegypti (L.) mosquitoes and DENV-1 isolated from Key West in 2010 to test the hypothesis that if the 2009 and 2010 DENV-1 genome sequences are similar, then vertical transmission of DENV-1 from infected Ae. aegypti female mosquitoes to their eggs could have served as an interepidemic reservoir between outbreaks. We also investigated the ability of Florida Aedes albopictus (Skuse) mosquitoes to vertically transmit DENV-1. In addition, we determined the rates of infection and dissemination of these Florida mosquito species for DENV-1 and the effect of DENV-1 infection on oviposition success and number of mosquito eggs laid by females. Vertical transmission of DENV-1 was documented, with rates of 11.11% (2 out of 18) for Ae. albopictus and 8.33% (3 out of 36) for Ae. aegypti. Approximately 93% (111 out of 119) of Ae. aegypti that fed on DENV-1 in blood became infected, and 80% (89 out of 111) of infections were disseminated. Similarly, 93% of Ae. albopictus became infected (53 out of 57), and 85% (45 out of 53) of infections were disseminated. No significant differences were detected in numbers of eggs laid by either species after imbibing DENV-1 in blood, suggesting little cost of infection on number of eggs laid. Our results demonstrate that Florida Ae. aegypti and Ae. albopictus mosquitoes are competent vectors for DENV-1, whose maintenance between the 2009 and 2010 Key West outbreaks may have been facilitated by vertical transmission.
TL;DR: Passive traps made from inexpensive, commonly available materials may be suitable for collection of mosquitoes and potentially other hematophagous dipterans for pathogen surveillance.
Abstract: Mosquitoes often are collected as part of an arbovirus surveillance program. However, trapping and processing of mosquitoes for arbovirus detection is often costly and difficult in remote areas. Most traps, such as the gold standard Center for Disease control light trap, require batteries that must be charged and changed overnight. To overcome this issue we have developed several passive traps for collection of mosquitoes that have no power requirements. The passive traps capture mosquitoes as they follow a CO2 plume up a polyvinyl chloride pipe leading to a clear chamber consisting of a plastic crate. We believe the translucent, clear windows created by the crate inhibits escape. Once inside the crate mosquitoes readily feed on honey-treated Flinders Technology Associates cards that then can be processed by polymerase chain reaction for viral ribonucleic acid. Of the two designs tested, the box or crate-based passive trap (passive box trap, PBT) generally caught more mosquitoes than the cylinder trap. In Latin square field trials in Cairns and Florida, PBTs collected mosquitoes at rates of 50 to 200% of Center for Disease Control model 512 light traps. Mosquito collections by PBTs can be increased by splitting the CO2 gas line so it services two traps, or by placing an octenol lure to the outside of the box. Very large collections can lead to crowding at honey-treated cards, reducing feeding rates. Addition of fipronil to the honey killed mosquitoes and did not impact feeding rates nor the ability to detect Kunjin viral ribonucleic acid by polymerase chain reaction; this could be used to minimize crowding affects on feeding caused by large collections. The passive traps we developed are made from inexpensive, commonly available materials. Passive traps may thus be suitable for collection of mosquitoes and potentially other hematophagous dipterans for pathogen surveillance.
TL;DR: The size of adult Ae.
Abstract: The size of Aedes aegypti (L.) mosquito populations and adult survival rates have proven difficult to estimate because of a lack of consistent quantitative measures to equate sampling methods, such as adult trapping, to actual population size. However, such estimates are critical for devising control methods and for modeling the transmission of dengue and other infectious agents carried by this species. Here we take advantage of recent releases of Wolbachia-infected Ae. aegypti coupled with the results of ongoing monitoring to estimate the size of adult Ae. aegypti populations around Cairns in far north Queensland, Australia. Based on the association between released adults infected with Wolbachia and data from Biogents Sentinel traps, we show that data from two locations are consistent with population estimates of approximately 5-10 females per house and daily survival rates of 0.7-0.9 for the released Wolbachia-infected females. Moreover, we estimate that networks of Biogents Sentinel traps at a density of one per 15 houses capture around 5-10% of the adult population per week, and provide a rapid estimate of the absolute population size of Ae. aegypti. These data are discussed with respect to release rates and monitoring in future Wolbachia releases and also the levels of suppression required to reduce dengue transmission.
TL;DR: Integrated mosquito management programs should incorporate the elimination of disused containers to reduce its infestation and adult production, especially in low SES neighborhoods where they occur most frequently.
Abstract: Mosquito populations are largely regulated by processes occurring at the larval stage. We sampled mosquito larval microhabitats (mostly water-holding containers) in six neighborhoods in the Washington, DC, area that varied in socioeconomic status (SES) and housing structure (row houses vs. stand-alone houses) to test associations among these neighborhood characteristics, microhabitat abundance and parameters, and mosquito occurrence and densities. Thirty-four percent (33.9%) of sampled microhabitats contained mosquito larvae, and 93.1% of larvae were Aedes albopictus Skuse or Culex pipiens L. Five specific container types (drains, corrugated flexible drainpipes, planters, garbage cans, and buckets) accounted for the majority of water-holding (56.0%) and mosquito-positive (50.6%) microhabitats sampled. We found no associations between SES or housing structure with total microhabitat abundance per yard, mosquito occurrence or mosquito densities per microhabitat. In contrast, container purpose varied with SES, with low SES neighborhoods having greater numbers of disused containers and lower numbers of functional containers than low and medium SES neighborhoods. Ae. albopictus were 83% more abundant in disused containers, whereas Cx. pipiens were more abundant in structural and functional containers, possibly owing to species-specific oviposition and development related to water quality. Ae. albopictus densities increased over the summer, whereas Cx. pipiens densities remained constant. Ae. albopictus is usually the dominant pest in urban areas in the eastern United States; therefore, integrated mosquito management programs should incorporate the elimination of disused containers to reduce its infestation and adult production, especially in low SES neighborhoods where they occur most frequently.
TL;DR: In this article, the authors detect WNV RNA from larvae hatched from eggs deposited by infected females during late summer and fall may provide evidence for the vertical passage of WNV to overwintering cohorts.
Abstract: Culex (Diptera: Culicidae) mosquitoes, the primary summer vectors of West Nile virus (family Flaviviridae, genus Flavivirus, WNV), also may serve as overwintering reservoir hosts. Detection of WN viral RNA from larvae hatched from eggs deposited by infected females during late summer and fall may provide evidence for the vertical passage of WNV to overwintering cohorts. To determine whether vertical transmission to the overwintering generation occurs in populations of Culex mosquitoes throughout California, larvae from naturally infected females were tested by family for WN viral RNA by real-time quantitative reverse transcription-polymerase chain reaction during August through October 2011. Viral RNA was detected in 34 of 934 Culex tarsalis Coquillett and Cx. pipiens complex females that laid viable egg rafts. From these egg rafts, first-instar larvae from nine families tested positive, yielding an overall field vertical transmission rate of 26% (n = 34). To determine whether the WNV may be lost transtadially during development to the adult stage, first-instar larvae and adult progeny from experimentally infected Cx. pipiens complex females were assessed for the presence and quantity of WN viral RNA. Most (approximately 75%) WNV infections were lost from positive families during larval development to the adult stage. In field and laboratory studies, only infected mothers with mean cycle threshold scores < or = 20 vertically transmitted WNV to larval progeny, adult progeny, or both. In summary, vertical transmission of WNV was detected repeatedly in naturally infected Culex mosquitoes collected throughout California during late summer and fall, with females having high titered infections capable of passing WNV onto their progeny destined for overwintering.
TL;DR: The results suggest that male size is an important trait in determining male mating competitiveness in the field and insemination success in the laboratory, and the implications in terms of sexual selection in An.
Abstract: Before the release of genetically-modified or sterile male mosquitoes in an attempt to control local populations of malaria vectors, it is crucial to determine male traits involved in mating success. The effects of male size and age as determinants of male mating success in Anopheles gambiae s.s. were measured in the field and under laboratory conditions in Burkina Faso. First, the body sizes (estimated by wing length) of mating, swarming, and indoor-resting male mosquitoes were compared over a 3-yr period (2006–2009) from July to October in Soumousso and Vallee du Kou, two villages in western Burkina Faso. Second, the age structure of swarming and resting male mosquitoes were characterized based on the number of spermatocysts and the proportion of sperm in the reservoir of wild-caught male testis. Third, male age effects on the insemination rate of female An. gambiae were investigated in the laboratory. The mean size of males collected in copula was significantly larger than the mean for swarming males and indoor-resting males. The optimum male age for successful insemination of females was 4–8 d. These results suggest that male size is an important trait in determining male mating competitiveness in the field. Although age was not found to be a significant factor in mating competitiveness, it was significantly correlated with swarming behaviors in the field and insemination success in the laboratory. The implications of these results in terms of sexual selection in An. gambiae and vector control programs are further discussed.
TL;DR: The development of New and Old World Leishmania infantum in its natural vectors Lu.
Abstract: The spread of leishmaniasis to areas where it was previously considered nonendemic has been recently found in the New and Old Worlds, and climate changes are suspected as a crucial factor responsible for this spread. Ambient temperature is known to significantly affect the metabolism of sand flies and their developmental times, but little is known about the effect of temperature on the Leishmania life cycle in vectors. This study assesses the effect of temperature on the development of two closely related New World Viannia species, Leishmania braziliensis and Leishmania peruviana, in the permissive vector Lutzomyia longipalpis, and on the development of New and Old World Leishmania infantum in its natural vectors Lu. longipalpis and Phlebotomus perniciosus, respectively. The mountain species L. peruviana developed well in sand fly females kept at 20°C, whereas at 26°C, most infections were lost during the defecation of bloodmeal remains; this suggests an adaptation to the slower metabolism of san...
TL;DR: Results reveal postburial interval estimates for forensic investigations in mid-Michigan during the summer, depending on climatic and soil conditions.
Abstract: This study examined pig carcasses buried at two different depths, 30 and 60 cm, to determine if insects were able to colonize buried carcasses, when they arrive at each depth, and what fauna were present over seven sampling dates to establish an insect succession database on buried carrion in East Lansing, MI. Thirty-eight pigs were buried, 18 at 30 cm and 20 at 60 cm. Four control carcasses were placed on the soil surface. Three replicates at each depth were exhumed after 3, 7, 14, 21, 30, and 60 d, respectively. One pig also was exhumed from 60 cm after 90 d and another after 120 d. Sarcophaga bullata (Parker) (Diptera: Sarcophagidae) and Hydrotaea sp. (Diptera: Muscidae) were found colonizing buried carrion 5 d after burial at 30 cm. Insect succession at 30 cm proceeded with flesh and muscid flies being the first to colonize, followed by blow flies. Insects were able to colonize carcasses at 60 cm and Hydrotaea sp. and Megaselia scalaris (Loew) (Diptera: Phoridae) were collected 7 d after burial. Insect succession at 60 cm did not proceed similarly, instead muscid and coffin flies were the only larvae collected. Overall these results reveal postburial interval estimates for forensic investigations in mid-Michigan during the summer, depending on climatic and soil conditions.
TL;DR: Eleven species were evaluated from Florida to determine which of these species should be targeted for control should Rift Valley fever virus (RVFV) be detected in North America and how environmental factors affect transmission.
Abstract: We evaluated Aedes atlanticus Dyar and Knab, Aedes infirmatus Dyar and Knab, Aedes vexans (Meigen), Anopheles crucians Wiedemann, Coquillettidia perturbans (Walker), Culex nigripalpus Theobald, Mansonia dyari Belkin, Heinemann, and Page, and Psorophora ferox (Von Humboldt) from Florida to determine which of these species should be targeted for control should Rift Valley fever virus (RVFV) be detected in North America. Female mosquitoes that had fed on adult hamsters inoculated with RVFV were incubated for 7-21 d at 26 degrees C, then allowed to refeed on susceptible hamsters, and tested to determine infection, dissemination, and transmission rates. We also inoculated mosquitoes intrathoracically, held them for 7 d, and then allowed them to feed on a susceptible hamster to check for a salivary gland barrier. When exposed to hamsters with viremias > or = 10(7.6) plaque-forming units per milliliter of blood, at least some individuals in each of the species tested became infected; however, Cx. nigripalpus, An. crucians, and Ae. infirmatus were essentially incompetent vectors in the laboratory because of either a midgut escape or salivary gland barrier. Each of the other species should be considered as potential vectors and would need to be controlled if RVFV were introduced into an area where they were found. Additional studies need to be conducted with other geographic populations of these species and to determine how environmental factors affect transmission.
TL;DR: This study revealed that R. chalepensis essential oil and its major compounds were active biting deterrents against Ae.
Abstract: The essential oil from aerial parts of Ruta chalepensis L. (Sapindales: Rutaceae) was obtained by hydrodistillation, and its chemical profile was identified using gas chromatography and gas chromatography-mass spectrometry. Compounds, 2-undecanone (43.2%), 2-nonanone (27.9%), and 2-nonyl acetate (10.6%) were the major constituents of the oil. Biting deterrent activity of R. chalepensis essential oil at 10 and 50 microg/cm2, 2-undecanone at 8.5 microg/cm2, 2-nonanone at 9 microg/cm2, and 2-nonyl acetate at 9.3 microg/cm2 was similar to DEET (N, N-diethyl-meta-toluamide) at 4.8 microg/cm2, against Aedes aegypti L. Biting deterrent activity of R. chalepensis oil at 50 microg/cm2 against Anopheles quadrimaculatus Say was statistically similar to DEET at 4.8 microg/cm2, whereas the activity was lower in the other compounds tested. In cloth patch assay, R. chalepensis essential oil was effective at 187 microg/cm2, whereas 2-undecanone was effective at 108.9 microg/cm2 against Ae. aegypti. In larval bioassays, 2-undecanone showed similar toxicity whereas toxicity of R. chalepensis essential oil and 2-nonanone was higher at 24-h posttreatment at the LD50 in An. quadrimaculatus than Ae. aegypti. This study revealed that R. chalepensis essential oil and its major compounds were active biting deterrents against Ae. aegypti at higher application rates whereas only the essential oil showed activity similar to DEET against An. quadrimaculatus. 2-undecanone was the most active compound in in vivo repellency bioassay against Ae. aegypti. Chemical composition of R. chalepensis essential oil varies because of plant production and harvest practices, and the activity level of the essential oil may depend on the source of the sample.
TL;DR: An increasing reduction in the microbial diversity during mosquito development from egg to adult was demonstrated and the gram-negative bacterium Elizabethkingia meningoseptica King was identified as the dominant species in the midgut of lab-reared male and female mosquitoes.
Abstract: Following their transmission from the human to the mosquito with the bloodmeal, malaria parasites have to persevere in the mosquito midgut for approximately 1 d. During this period the parasites are highly vulnerable to factors of the mosquito midgut, including bacteria. We here aimed at determining the microbial diversity of gut bacteria of the Asian malaria vector Anopheles stephensi (Liston) during development and under different feeding regimes, including feeds on malaria parasite-infected blood. 16S rRNA and denaturing gradient gel electrophoresis analyses demonstrated an increasing reduction in the microbial diversity during mosquito development from egg to adult and identified the gram-negative bacterium Elizabethkingia meningoseptica King as the dominant species in the midgut of lab-reared male and female mosquitoes. E. meningoseptica is transmitted between generations and its predominance in the mosquito midgut was not altered by diet, when the gut microbiota was compared between sugar-fed and blood-fed female mosquitoes. Furthermore, feeds on blood infected with malaria parasites did not impact the presence of E. meningoseptica in the gut. Extracts from cultured E. meningoseptica were active against gram-positive and negative bacteria and yeast and against the blood and gametocyte transmission stages of the malaria parasite Plasmodium falciparum Welch. The antimicrobial and antiplasmodial activities of E. meningoseptica may account for its dominance in the midgut of the malaria vector.
TL;DR: This work reconstructed phylogenies of the Calliphoridae within the larger context of the other Oestroidea based on 5,189 bp of combined data from one mitochondrial, three nuclear, and three nuclear genes using maximum parsimony, maximum likelihood, and Bayesian methods.
Abstract: Approximately 8% of calyptrate species diversity comes from the Calliphoridae, which includes flies of medical, veterinary, and forensic importance. The status of family Calliphoridae has for years been the central systematic problem of the superfamily Oestroidea, and phylogenetic relationships between the key groups of the Calliphoridae are unresolved and controversial. We reconstructed phylogenies of the Calliphoridae within the larger context of the other Oestroidea based on 5,189 bp of combined data from one mitochondrial (cytochrome oxidase subunit one) and three nuclear (carbamoylphosphate synthetase, elongation factor one alpha, and 28S ribosomal RNA) genes using maximum parsimony, maximum likelihood, and Bayesian methods. Trees obtained from the different phylogenetic methods were almost identical. Calliphoridae is polyphyletic, with the phylogenetic position of Mesembrinellinae still uncertain but clearly outside the lineage that includes other Calliphoridae and some noncalliphorids, and Polleniinae is the sister group of the family Tachinidae. Strong support for a sister group relationship between Rhiniinae and traditional calliphorid subfamilies conflicts with a recent proposal to give Rhiniinae family status. All calliphorid subfamilies (except Calliphorinae) for which we had more than one species were monophyletic. Melanomyinae was nested within Calliphorinae. Toxotarsinae was more closely related to Calliphorinae rather than, as indicated by morphology, to Chrysomyinae. Efforts to resolve the relationships of the Oestroid families were largely inconclusive, although the monophyly of the superfamily was strongly supported.
TL;DR: Data suggest that there may be clear temperature and precipitation thresholds beyond which epidemic levels of WNV transmission occur, and are strongly correlated with increases in yearly WNV infection rates over a 9-yr period (2003–2011).
Abstract: This study looked at the influence of interannual variations in temperature and precipitation on seasonal mosquito abundances, the prevalence of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in the northeastern United States, and the capacity for local mosquito communities to maintain and transmit WNV, defined as vector community competence. Vector and virus surveillance took place within Middlesex County in New Jersey over two transmission seasons (2010 and 2011). Drought conditions during the 2010 season were associated with significant increases in the number of blood-fed Culex spp. mosquitoes collected per week, and significant increases in vector community competence, or the ability of local vector communities to transmit WNV, when compared with the wetter and milder 2011 season. These increases were associated with significantly higher weekly WNV infection rates in Culex spp. (i.e., Culex pipiens L. and Culex restuans L.) during the 2010 drought season. On a larger scale, the...
TL;DR: Statistics suggest that sex and age of deer, temperature, precipitation, and an index of tick dispersion by migratory birds were significantly associated with tick infestation levels, and hunterkilled deer may have limited use as sentinels for emerging areas of tick-borne anaplasmosis.
Abstract: Due to recent establishment of the blacklegged tick, Ixodes scapularis Say, in southeastern Canada, tick-borne zoonoses (Lyme disease, human granulocytotropic anaplasmosis, and babesiosis) are of growing concern forpublic health. Using white-tailed deer (Odocoileus virginianus) culled in southwestern Quebec during 2007–2008, we investigated whether hunter-killed deer could act as sentinels for early establishing tick populations and for tick-borne pathogens. Accounting for environmental characteristics of culling sites, and age and sex of deer, we investigated whether their tick infestation levels could identify locations of known tick populations detected in active surveillance, presumed tick populations detected by passive surveillance, or both. We also used spatial cluster analyses to identify spatial patterns of tick infestation and occurrence of tick-borne zoonoses infection in ticks collected from the deer. Adult ticks were found on 15% of the 583 deer examined. Adult male deer had the grea...