Terrestrial Bird Migration and West Nile Virus Circulation, United States.

Host migration and emerging pathogens are strongly associated, especially with regard to zoonotic diseases. West Nile virus (WNV), a mosquitoborne pathogen capable of causing severe, sometimes fatal, neuroinvasive disease in humans, is maintained in highly mobile avian hosts. Using phylogeographic approaches, we investigated the relationship between WNV circulation in the United States and the flight paths of terrestrial birds. We demonstrated southward migration of WNV in the eastern flyway and northward migration in the central flyway, which is consistent with the looped flight paths of many terrestrial birds. We also identified 3 optimal locations for targeted WNV surveillance campaigns in the United States-Illinois, New York, and Texas. These results illustrate the value of multidisciplinary approaches to surveillance of infectious diseases, especially zoonotic diseases.

Effect of Photoperiod On Permethrin Resistance In Aedes aegypti.

Living organisms have been exposed to light-dark cycles that allowed them to adapt to different ecological niches. Circadian cycles affect hormone release, metabolism, and response to xenobiotic compounds. Current studies have shown that insect susceptibility to toxic agents depends on circadian cycles, mainly because the biochemical processes involved in detoxification and responses to oxidative stress are modulated by this process. The goal of this study was to determine the effect of photoperiod on resistance to permethrin in Aedes aegypti . Collections of Ae. aegypti from 4 locations in Yucatan, southern Mexico, were subjected to 2 different photoperiod schemes: dark (0 h light:24 h dark) and natural photoperiod (12 h light:12 h dark). The comparison of both photoperiods was evaluated with respect to permethrin resistance using bottle bioassays and by monitoring the possible mechanism related such as enzymatic activity and by the frequency of 2 knockdown resistance mutations in the voltage-dependent sodium channel gene (V1016I and F1534C). The susceptible strain was used as a reference. The mosquitoes in dark photoperiod showed a reduction in resistance to the pyrethroid. The α-esterases and glutathione S-transferase enzymatic activities showed lower levels in the dark photoperiod, and the frequencies of V1016I knockdown resistance mutation showed significant difference between photoperiod schemes.

Two Novel Bioassays to Assess the Effects of Pyrethroid-Treated Netting on Knockdown-Susceptible Versus Resistant Strains of Aedes aegypti.

We describe 2 new mosquito bioassays for use with insecticide-treated netting or other textiles. The 1st is a cylinder bioassay in which a mosquito is forced to contact treated material regardless of where it lands within the bioassay construct. The 2nd is a repellency/irritancy and biting-inhibition bioassay (RIBB) in which human arms and breath are used as attractants. Mosquitoes have the choice to pass through holes cut in untreated or treated netting to move from a center release chamber into side chambers to reach arms and potentially bite. Trials were conducted with pyrethroid-susceptible (New Orleans), moderately resistant (Hunucmá), and highly resistant (Vergel) strains of Aedes aegypti. Tests with netting treated with different pyrethroids demonstrated the utility of the cylinder bioassay to quantify knockdown and mortality following exposure to treated netting, and of the RIBB to quantify spatial repellency/contact irritancy of the treated netting and biting inhibition after females land on and then pass through holes in the treated netting. Both tested brands of pyrethroid-treated mosquitocidal netting (DuraNet® and NetProtect®) were effective against New Orleans but ineffective against Vergel strains. Mortality in the cylinder bioassay was 100% for New Orleans for all tested brands of treated netting, but only 10-14% for Vergel. Rates of passage through treated netting to reach a human arm in the RIBB were 10-15% for New Orleans versus 24-37% for Vergel. The reduction in biting after passage through treated netting, compared with untreated netting in the same trial replicates, was 12-39% for New Orleans versus ≤9% for Vergel.

Household use of insecticide consumer products in a dengue-endemic area in México.

OBJECTIVES: To evaluate the household use of insecticide consumer products to kill mosquitoes and other insect pests, as well as the expenditures for using these products, in a dengue-endemic area of México. METHODS: A questionnaire was administered to 441 households in Mérida City and other communities in Yucatán to assess household use of insecticide consumer products. RESULTS: A total of 86.6% of surveyed households took action to kill insect pests with consumer products. The most commonly used product types were insecticide aerosol spray cans (73.6%), electric plug-in insecticide emitters (37.4%) and mosquito coils (28.3%). Mosquitoes were targeted by 89.7% of households using insecticide aerosol spray cans and >99% of households using electric plug-in insecticide emitters or mosquito coils. Products were used daily or every 2 days in most of the households for insecticide aerosol spray cans (61.4%), electric plug-in insecticide emitters (76.2%) and mosquito coils (82.1%). For all products used to kill insect pests, the median annual estimated expenditure per household that took action was 408 Mexican pesos ($MXN), which corresponded to approximately 31 $US. These numbers are suggestive of an annual market in excess of 75 million $MXN (>5.7 million $US) for Mérida City alone. CONCLUSION: Mosquitoes threaten human health and are major nuisances in homes in the study area in México. Households were found to have taken vigorous action to kill mosquitoes and other insect pests and spent substantial amounts of money on insecticide consumer products.

Temporal correlations between mosquito-based dengue virus surveillance measures or indoor mosquito abundance and dengue case numbers in Mérida City, México.

Surveillance of dengue virus (DENV) in Aedes (Stegomyia) aegypti (L.) females is of potential interest because human DENV infections are commonly asymptomatic, which decreases the effectiveness of dengue case surveillance to provide early warning of building outbreaks. Our primary aim was to examine if mosquito-based virological measures--monthly percentages of examined Ae. aegypti females infected with DENV or examined homes from which at least one DENV-infected Ae. aegypti female was collected--are correlated with reported dengue cases in the same or subsequent months within study neighborhoods in Méida City, México. The study encompassed approximately 30 neighborhoods in the southern and eastern parts of the city. Mosquitoes were collected monthly over a 15-mo period within study homes (average of 145 homes examined per month); this produced approximately 5,800 Ae. aegypti females subsequently examined for DENV RNA. Although monthly dengue case numbers in the study neighborhoods varied > 100-fold during the study period, we did not find statistically significant positive correlations between monthly data for mosquito-based DENV surveillance measures and reported dengue cases in the same or subsequent months. Monthly average temperature, rainfall, and indoor abundance of Ae. aegypti females were positively correlated (P < or = 0.001) with dengue case numbers in subsequent months with lag times of 3-5, 2, and 1-2 mo, respectively. However, because dengue outbreak risk is strongly influenced by serotype-specific susceptibility of the human population to DENV, the value of weather conditions and entomological indices to predict outbreaks is very limited. Potential ways to improve the sensitivity of mosquito-based DENV surveillance are discussed.

Vacant lots: productive sites for Aedes (Stegomyia) aegypti (Diptera: Culicidae) in Mérida City, México.

We assessed the potential for vacant lots and other nonresidential settings to serve as source environments for Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) in Mérida City, México. Mosquito immatures were collected, during November 2011-June 2013, from residential premises (n = 156 site visits) and nonresidential settings represented by vacant lots (50), parking lots (18), and streets or sidewalks (28). Collections totaled 46,025 mosquito immatures of 13 species. Ae. aegypti was the most commonly encountered species accounting for 81.0% of total immatures, followed by Culex quinquefasciatus Say (12.1%). Site visits to vacant lots (74.0%) were more likely to result in collection of Ae. aegypti immatures than residential premises (35.9%). Tires accounted for 75.5% of Ae. aegypti immatures collected from vacant lots. Our data suggest that vacant lots should be considered for inclusion in mosquito surveillance and control efforts in Mérida City, as they often are located near homes, commonly have abundant vegetation, and frequently harbor accumulations of small and large discarded water-holding containers that we now have demonstrated to serve as development sites for immature mosquitoes. In addition, we present data for associations of immature production with various container characteristics, such as storage capacity, water quality, and physical location in the environment.

Urban Mosquito Fauna in Mérida City, México: Immatures Collected from Containers and Storm-water Drains/Catch Basins.

We examined the species composition and temporal occurrence of immature mosquitoes in containers and storm-water drains/catch basins from November 2011 to June 2013 in Mérida City, México. A wide range of urban settings were examined, including residential premises, vacant lots, parking lots, and streets or sidewalks with storm-water drains/catch basins. In total, 111,776 specimens of 15 species were recorded. The most commonly collected species were Aedes (Stegomyia) aegypti (L.) (n = 60,961) and Culex quinquefasciatus Say (45,702), which together accounted for 95.4% of the immatures collected. These species were commonly encountered during both rainy and dry seasons, whereas most other mosquito species were collected primarily during the rainy season. Other species collected were Aedes (Howardina) cozumelensis Diaz Najera, Aedes (Ochlerotatus) taeniorhynchus (Wiedemann), Aedes (Ochlerotatus) trivittatus (Coquillett), Culex coronator Dyar and Knab, Culex interrogator Dyar and Knab, Culex lactator Dyar and Knab, Culex nigripalpus Theobald, Culex salinarius Coquillett, Culex tarsalis Coquillett, Culex thriambus Dyar, Haemagogus equinus Theobald, Limatus durhamii Theobald, and Toxorhynchites rutilus (Coquillett). The greatest number of species was recorded from vacant lots (n = 11), followed by storm-water drains/catch basins (nine) and residential premises (six). Our study demonstrated that the heterogeneous urban environment in Mérida City supports a wide range of mosquito species, many of which are nuisance biters of humans and/or capable of serving as vectors of pathogens affecting humans or domestic animals. We also briefly reviewed the medical importance of the encountered mosquito species.

Productive container types for Aedes aegypti immatures in Mérida, México.

During 2007-2010, we examined which container types in Mérida, México, are most productive for Aedes aegypti (L.) immatures. Surveys for mosquito immatures followed routine surveillance methodology and container type classifications used by Servicios de Salud de Yucatán. Our main findings were that (1) small and larger discarded containers that serve no particular purpose and therefore can be removed from the environment contribute strongly to larval and pupal production in Mérida, and (2) the importance of different container types can vary among sets of residential premises as well as between dry and wet periods. These results may help to guide future implementation in Mérida of control efforts that target the most productive container types for Ae. aegypti immatures. Furthermore, if the Patio Limpio cleanup campaign that currently is ongoing in Mérida proves successful in removing discarded containers as important immature development sites, then we should see dramatic changes in the most productive container types in the future as the mosquito is forced to switch to other container types, which perhaps also will be easier to include in highly targeted mosquito control interventions.

Identification of super-infected Aedes triseriatus mosquitoes collected as eggs from the field and partial characterization of the infecting La Crosse viruses.

BACKGROUND: La Crosse virus (LACV) is a pathogenic arbovirus that is transovarially transmitted by Aedes triseriatus mosquitoes and overwinters in diapausing eggs. However, previous models predicted transovarial transmission (TOT) to be insufficient to maintain LACV in nature. RESULTS: To investigate this issue, we reared mosquitoes from field-collected eggs and assayed adults individually for LACV antigen, viral RNA by RT-PCR, and infectious virus. The mosquitoes had three distinct infection phenotypes: 1) super infected (SI+) mosquitoes contained infectious virus, large accumulations of viral antigen and RNA and comprised 17 of 17,825 (0.09%) of assayed mosquitoes, 2) infected mosquitoes (I+) contained no detectable infectious virus, lesser amounts of viral antigen and RNA, and comprised 3.7% of mosquitoes, and 3) non-infected mosquitoes (I-) contained no detectable viral antigen, RNA, or infectious virus and comprised 96.21% of mosquitoes. SI+ mosquitoes were recovered in consecutive years at one field site, suggesting that lineages of TOT stably-infected and geographically isolated Ae. triseriatus exist in nature. Analyses of LACV genomes showed that SI+ isolates are not monophyletic nor phylogenetically distinct and that synonymous substitution rates exceed replacement rates in all genes and isolates. Analysis of singleton versus shared mutations (Fu and Li's F*) revealed that the SI+ LACV M segment, with a large and significant excess of intermediate-frequency alleles, evolves through disruptive selection that maintains SI+ alleles at higher frequencies than the average mutation rate. A QTN in the LACV NSm gene was detected in SI+ mosquitoes, but not in I+ mosquitoes. Four amino acid changes were detected in the LACV NSm gene from SI+ but not I+ mosquitoes from one site, and may condition vector super infection. In contrast to NSm, the NSs sequences of LACV from SI+ and I+ mosquitoes were identical. CONCLUSIONS: SI+ mosquitoes may represent stabilized infections of Ae. triseriatus mosquitoes, which could maintain LACV in nature. A gene-for-gene interaction involving the viral NSm gene and a vector innate immune response gene may condition stabilized infection.

Host-feeding preference of the mosquito, Culex quinquefasciatus, in Yucatan State, Mexico.

Studies were conducted to determine the host-feeding preference of Culex quinquefasciatus Say (Diptera: Culicidae) in relation to the availability of human and domestic animals in the city of Merida, Yucatan State, Mexico. Mosquitoes were collected in the backyards of houses using resting wooden boxes. Collections were made five times per week from January to December 2005. DNA was extracted from engorged females and tested by PCR using universal avian- and mammalian-specific primers. DNA extracted from avian-derived blood was further analyzed by PCR using primers that differentiate among the birds of three avian orders: Passeriformes, Columbiformes and Galliformes. PCR products obtained from mammalian-derived blood were subjected to restriction enzyme digestion to differentiate between human-, dog-, cat-, pig-, and horse-derived blood meals. Overall, 82% of engorged mosquitoes had fed on birds, and 18% had fed on mammals. The most frequent vertebrate hosts were Galliformes (47.1%), Passeriformes (23.8%), Columbiformes (11.2%) birds, and dogs (8.8%). The overall human blood index was 6.7%. The overall forage ratio for humans was 0.1, indicating that humans were not a preferred host for Cx. quinquefasciatus in Merida.

Patterns of variation in the inhibitor of apoptosis 1 gene of Aedes triseriatus, a transovarial vector of La Crosse virus.

Aedes triseriatus mosquitoes transovarially transmit (TOT) La Crosse virus (LACV) to their offspring with minimal damage to infected ovaries. Ae. triseriatus inhibitor of apoptosis 1 (AtIAP1) is a candidate gene conditioning the ability to vertically transmit LACV. AtIAP1 was amplified and sequenced in adult mosquitoes reared from field-collected eggs. Sequence analysis showed that AtIAP1 has much higher levels of genetic diversity than genes found in other mosquitoes. Despite this large amount of diversity, strong purifying selection of polymorphisms located in the Baculovirus inhibitor of apoptosis repeat (BIR) domains and, to a lesser extent, in the 5' untranslated region seems to indicate that these portions of AtIAP1 are the most important. These results indicate that the 5'UTR plays an important role in transcription and translation and that the BIR domains are important functional domains in the protein. Single nucleotide polymorphisms (SNPs) were compared between LACV-positive and -negative mosquitoes to test for associations between segregating sites and the ability to be transovarially infected with LACV. Initial results indicated that five SNPs were associated with TOT of LACV; however, these results were not replicable with larger sample sizes.

Temporal and geographic evidence for evolution of Sin Nombre virus using molecular analyses of viral RNA from Colorado, New Mexico and Montana.

BACKGROUND: All viruses in the family Bunyaviridae possess a tripartite genome, consisting of a small, a medium, and a large RNA segment. Bunyaviruses therefore possess considerable evolutionary potential, attributable to both intramolecular changes and to genome segment reassortment. Hantaviruses (family Bunyaviridae, genus Hantavirus) are known to cause human hemorrhagic fever with renal syndrome or hantavirus pulmonary syndrome. The primary reservoir host of Sin Nombre virus is the deer mouse (Peromyscus maniculatus), which is widely distributed in North America. We investigated the prevalence of intramolecular changes and of genomic reassortment among Sin Nombre viruses detected in deer mice in three western states. METHODS: Portions of the Sin Nombre virus small (S) and medium (M) RNA segments were amplified by RT-PCR from kidney, lung, liver and spleen of seropositive peromyscine rodents, principally deer mice, collected in Colorado, New Mexico and Montana from 1995 to 2007. Both a 142 nucleotide (nt) amplicon of the M segment, encoding a portion of the G2 transmembrane glycoprotein, and a 751 nt amplicon of the S segment, encoding part of the nucleocapsid protein, were cloned and sequenced from 19 deer mice and from one brush mouse (P. boylii), S RNA but not M RNA from one deer mouse, and M RNA but not S RNA from another deer mouse. RESULTS: Two of 20 viruses were found to be reassortants. Within virus sequences from different rodents, the average rate of synonymous substitutions among all pair-wise comparisons (pis) was 0.378 in the M segment and 0.312 in the S segment sequences. The replacement substitution rate (pia) was 7.0 x 10-4 in the M segment and 17.3 x 10-4 in the S segment sequences. The low pia relative to pis suggests strong purifying selection and this was confirmed by a Fu and Li analysis. The absolute rate of molecular evolution of the M segment was 6.76 x 10-3 substitutions/site/year. The absolute age of the M segment tree was estimated to be 37 years. In the S segment the rate of molecular evolution was 1.93 x 10-3 substitutions/site/year and the absolute age of the tree was 106 years. Assuming that mice were infected with a single Sin Nombre virus genotype, phylogenetic analyses revealed that 10% (2/20) of viruses were reassortants, similar to the 14% (6/43) found in a previous report. CONCLUSION: Age estimates from both segments suggest that Sin Nombre virus has evolved within the past 37-106 years. The rates of evolutionary changes reported here suggest that Sin Nombre virus M and S segment reassortment occurs frequently in nature.

ProactiveVector control strategies and improved monitoring and evaluation practices for dengue prevention.

Despite tremendous efforts by public health organizations in dengue-endemic countries, it has proven difficult to achieve effective and sustainable control of the primary dengue virus vector Aedes aegypti (L.) and to effectively disrupt dengue outbreaks. This problem has multiple root causes, including uncontrolled urbanization, increased global spread of dengue viruses, and vector and dengue control programs not being provided adequate resources. In this forum article, we give an overview of the basic elements of a vector and dengue control program and describe a continuous improvement cyclical model to systematically and incrementally improve control program performance by regular efforts to identify ineffective methods and inferior technology, and then replacing them with better performing alternatives. The first step includes assessments of the overall resource allocation among vector/dengue control program activities, the efficacy of currently used vector control methods, and the appropriateness of technology used to support the program. We expect this will reveal that 1) some currently used vector control methods are not effective, 2) resource allocations often are skewed toward reactive vector control measures, and 3) proactive approaches commonly are underfunded and therefore poorly executed. Next steps are to conceptualize desired changes to vector control methods or technologies used and then to operationally determine in pilot studies whether these changes are likely to improve control program performance. This should be followed by a shift in resource allocation to replace ineffective methods and inferior technology with more effective and operationally tested alternatives. The cyclical and self-improving nature of the continuous improvement model will produce locally appropriate management strategies that continually are adapted to counter changes in vector population or dengue virus transmission dynamics. We discuss promising proactive vector control approaches and the continued need for the vector and dengue control community to incorporate emerging technologies and to partner with academia, business and the community-at-large to identify new solutions that reduce dengue.

Aedes triseriatus females transovarially infected with La Crosse virus mate more efficiently than uninfected mosquitoes.

The mating efficiencies (the percentage of females inseminated by males) of field-collected and laboratory-colonized Aedes triseriatus (Say) (Diptera: Culicidae) female mosquitoes transovarially infected or uninfected with La Crosse virus (LACV) were compared. The females were placed in cages with age-matched males, and the insemination rates (number of inseminated females of the total number of females examined) were determined daily by detection of sperm in the spermathecae. LACV-infected mosquitoes typically mated earlier than uninfected mosquitoes, i.e., insemination occurred earlier after the mixing of males and females. LACV load was not correlated with increased insemination.

Use of Google Earth to strengthen public health capacity and facilitate management of vector-borne diseases in resource-poor environments.

OBJECTIVE: Novel, inexpensive solutions are needed for improved management of vector-borne and other diseases in resource-poor environments. Emerging free software providing access to satellite imagery and simple editing tools (e.g. Google Earth) complement existing geographic information system (GIS) software and provide new opportunities for: (i) strengthening overall public health capacity through development of information for city infrastructures; and (ii) display of public health data directly on an image of the physical environment. METHODS: We used freely accessible satellite imagery and a set of feature-making tools included in the software (allowing for production of polygons, lines and points) to generate information for city infrastructure and to display disease data in a dengue decision support system (DDSS) framework. FINDINGS: Two cities in Mexico (Chetumal and Merida) were used to demonstrate that a basic representation of city infrastructure useful as a spatial backbone in a DDSS can be rapidly developed at minimal cost. Data layers generated included labelled polygons representing city blocks, lines representing streets, and points showing the locations of schools and health clinics. City blocks were colour-coded to show presence of dengue cases. The data layers were successfully imported in a format known as shapefile into a GIS software. CONCLUSION: The combination of Google Earth and free GIS software (e.g. HealthMapper, developed by WHO, and SIGEpi, developed by PAHO) has tremendous potential to strengthen overall public health capacity and facilitate decision support system approaches to prevention and control of vector-borne diseases in resource-poor environments.

Potential for La Crosse virus segment reassortment in nature.

The evolutionary success of La Crosse virus (LACV, family Bunyaviridae) is due to its ability to adapt to changing conditions through intramolecular genetic changes and segment reassortment. Vertical transmission of LACV in mosquitoes increases the potential for segment reassortment. Studies were conducted to determine if segment reassortment was occurring in naturally infected Aedes triseriatus from Wisconsin and Minnesota in 2000, 2004, 2006 and 2007. Mosquito eggs were collected from various sites in Wisconsin and Minnesota. They were reared in the laboratory and adults were tested for LACV antigen by immunofluorescence assay. RNA was isolated from the abdomen of infected mosquitoes and portions of the small (S), medium (M) and large (L) viral genome segments were amplified by RT-PCR and sequenced. Overall, the viral sequences from 40 infected mosquitoes and 5 virus isolates were analyzed. Phylogenetic and linkage disequilibrium analyses revealed that approximately 25% of infected mosquitoes and viruses contained reassorted genome segments, suggesting that LACV segment reassortment is frequent in nature.

Mosquito species richness, composition, and abundance along habitat-climate-elevation gradients in the northern Colorado Front Range.

We exploited elevation gradients (1,500-2,400 m) ranging from plains to montane areas along the Poudre River and Big Thompson River in the northern Colorado Front Range to determine how mosquito species richness, composition, and abundance change along natural habitat-climate-elevation gradients. Mosquito collections in 26 sites in 2006 by using CO2-baited CDC light traps yielded a total of 7,136 identifiable mosquitoes of 27 species. Commonly collected species included Aedes vexans (Meigen) (n = 4,722), Culex tarsalis Coquillett (n = 825), Ochlerotatus increpitus (Dyar) (n = 546), Ochlerotatus trivittatus (Coquillett) (n = 303), Aedes cinereus Meigen (n = 280), Ochlerotatus melanimon (Dyar) (n = 146), Ochlerotatus dorsalis (Meigen) (n = 67), Culiseta inornata (Williston) (n = 52), Ochlerotatus pullatus (Coquillett) (n = 38), Ochlerotatus spencerii idahoensis (Theobald) (n = 37), and Culex pipiens L. (n = 29). Species richness was highest in plains habitats at elevations below 1,600 m. Numerous species were found exclusively or predominantly at low elevations below 1,700 m [Anopheles earlei Vargas, Anophelesfreeborni Aitken, Coquilletidia perturbans (Walker), Culex erythrothorax (Dyar), Cx. pipiens, Culex territans Walker, Oc. dorsalis, Ochlerotatus hendersoni (Cockerell), Oc. melanimon, and Oc. trivittatus], whereas others occurred predominantly at high elevations above 2,300 m [Ae. cinereus, Culiseta incidens (Thomson), Culiseta morsitans (Theoblad), Ochlerotatus cataphylla (Dyar), Ochlerotatus intrudens (Dyar), Oc. pullatus, and Ochlerotatus punctor (Kirby)]. Ae. vexans and Cx. tarsalis were abundant in the plains (< 1,600 m; mean June-August temperature > 19.5 degrees C), occurred at low abundances in foothills and low montane areas (1,610-1,730 m; 18.0-19.5 degrees C), and they were collected only sporadically in montane areas above 1,750 m (mean June-August temperature < 17.5 degrees C). These findings suggest that future climate warming may lead to shifts in distribution patterns of West Nile virus vectors (e.g., Cx. tarsalis) toward higher elevations in Colorado.

Gonotrophic cycle estimate for Culex quinquefasciatus in Mérida, Yucatán, México.

West Nile virus (WNV) has been present in the Yucatán State, México, since 2002. Culex quinquefasciatus, one of the main vectors of WNV transmission in the United States, is also common in Mexico and may be a key vector of WNV transmission t o humans in t he Yucatán. The aim of this study was to determine the length of the gonotrophic cycle and the survival rates of Cx. quinquefasciatus from Mérida, Yucatán, during the rainy versus the dry season. Mosquitoes were collected during 25-day periods in October (rainy season) and in April (dry season), and captured females were classified by abdominal appearance (freshly fed, late-stage fed, half gravid, and subgravid). To determine the age structure as nulliparous and parous females and to calculate the gonotrophic cycle through a time series and the mosquito survival, we used Davidson formulae. Also, vitellogenesis analysis to monitor egg maturity was conducted during both seasons. Cross-correlation data suggested a similar length of the gonotrophic cycle (4 days) in both seasons. Oogenic development required a minimum of 72 h in each season. However, survival of the mosquito population collected in the rainy season was significantly higher (0.91) with a mean temperature of 28 +/- 1.57 degrees C than was survival in the dry season (0.78) with a mean temperature of 29 +/- 1.10 degrees C. Survival, although higher during the rainy season, did not influence the length of the gonotrophic cycle of Cx. quinquefasciatus in Yucatán.

Bunyavirus Taxonomy: Limitations and Misconceptions Associated with the Current ICTV Criteria Used for Species Demarcation.

The International Committee on Taxonomy of Viruses (ICTV) has implemented numerous changes to the taxonomic classification of bunyaviruses over the years. Whereas most changes have been justified and necessary because of the need to accommodate newly discovered and unclassified viruses, other changes are a cause of concern, especially the decision to demote scores of formerly recognized species to essentially strains of newly designated species. This practice was first described in the seventh taxonomy report of the ICTV and has continued in all subsequent reports. In some instances, viruses that share less than 75% nucleotide sequence identity across their genomes, produce vastly different clinical presentations, possess distinct vector and host associations, have different biosafety recommendations, and occur in nonoverlapping geographic regions are classified as strains of the same species. Complicating the matter is the fact that virus strains have been completely eliminated from ICTV reports; thus, critically important information on virus identities and their associated biological and epidemiological features cannot be readily related to the ICTV classification. Here, we summarize the current status of bunyavirus taxonomy and discuss the adverse consequences associated with the reclassification and resulting omission of numerous viruses of public health importance from ICTV reports. As members of the American Committee on Arthropod-borne Viruses, we encourage the ICTV Bunyavirus Study Group to reconsider their stance on bunyavirus taxonomy, to revise the criteria currently used for species demarcation, and to list additional strains of public and veterinary importance.

The Use of Insecticide-Treated Curtains for Control of Aedes aegypti and Dengue Virus Transmission in "Fraccionamiento" Style Houses in México.

Dengue, chikungunya, yellow fever, and Zika viruses transmitted by Aedes aegypti mosquitoes are major public health threats in the tropical and subtropical world. In México, construction of large tracts of "fraccionamientos" high density housing to accommodate population growth and urbanization has provided fertile ground for Ae. aegypti-transmitted viruses. We investigated the utility of pyrethroid-treated window curtains to reduce both the abundance of Ae. aegypti and to prevent dengue virus (DENV) transmission in fraccionamiento housing. Windows and doors of fraccionamiento homes in urban/suburban areas, where Ae. aegypti pyrethroid resistance associated with the Ile1016 knock down resistance (kdr) mutation in the voltage gated sodium channel gene was high, and in rural areas, where kdr resistance was low, were fitted with either insecticide-treated curtains (ITCs) or non-treated curtains (NTCs). The homes were monitored for mosquito abundance and DENV infection. ITCs reduced the indoor abundance of Ae. aegypti and the number of DENV-infected mosquitoes in homes in rural but not in urban/suburban study sites. The presence of non-treated screens also was associated with reduced numbers of mosquitoes in homes. "Super-infested" homes, yielding more than 50 mosquitoes, including DENV-infected mosquitoes, provide a significant public health risk to occupants, visitors, and people in neighboring homes.