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1.  Detection of Eastern Equine Encephalomyelitis Virus RNA in North American Snakes 
The role of non-avian vertebrates in the ecology of eastern equine encephalomyelitis virus (EEEV) is unresolved, but mounting evidence supports a potential role for snakes in the EEEV transmission cycle, especially as over-wintering hosts. To determine rates of exposure and infection, we examined serum samples from wild snakes at a focus of EEEV in Alabama for viral RNA using quantitative reverse transcription polymerase chain reaction. Two species of vipers, the copperhead (Agkistrodon contortrix) and the cottonmouth (Agkistrodon piscivorus), were found to be positive for EEEV RNA using this assay. Prevalence of EEEV RNA was more frequent in seropositive snakes than seronegative snakes. Positivity for the quantitative reverse transcription polymerase chain reaction in cottonmouths peaked in April and September. Body size and sex ratios were not significantly different between infected and uninfected snakes. These results support the hypothesis that snakes are involved in the ecology of EEEV in North America, possibly as over-wintering hosts for the virus.
PMCID: PMC3516089  PMID: 23033405
2.  Serosurveillance of Eastern Equine Encephalitis Virus in Amphibians and Reptiles from Alabama, USA 
Eastern equine encephalitis virus (EEEV) is among the most medically important arboviruses in North America, and studies suggest a role for amphibians and reptiles in its transmission cycle. Serum samples collected from 351 amphibians and reptiles (27 species) from Alabama, USA, were tested for the presence of antibodies against EEEV. Frogs, turtles, and lizards showed little or no seropositivity, and snakes had high seropositivity rates. Most seropositive species were preferred or abundant hosts of Culex spp. mosquitoes at Tuskegee National Forest, that target ectothermic hosts. The cottonmouth, the most abundant ectotherm sampled, displayed a high prevalence of seropositivity, indicating its possible role as an amplification and/or over-wintering reservoir for EEEV.
PMCID: PMC3284378  PMID: 22403333
3.  Competency of Reptiles and Amphibians for Eastern Equine Encephalitis Virus 
Eastern equine encephalitis virus (EEEV) is endemic throughout most of the eastern United States. Although it is transmitted year round in Florida, transmission elsewhere is seasonal. The mechanism that enables EEEV to overwinter in seasonal foci remains obscure. In previous field studies, early season EEEV activity was detected in mosquito species that feed primarily upon ectothermic hosts, suggesting that reptiles and amphibians might represent overwintering reservoir hosts for EEEV. To determine if this might be possible, two commonly fed upon amphibian and reptile species were evaluated as hosts for the North American subtype I strain of EEEV. Neither amphibian species was a competent host. However, circulating viremias were detected in both reptile species examined. Hibernating infected garter snakes remained viremic after exiting hibernation. These data suggest that snakes may represent an overwintering host for North American EEEV.
PMCID: PMC3163860  PMID: 21896798
4.  Phylogenetic Analysis of Eastern Equine Encephalitis Virus Isolates from Florida 
Florida has the highest degree of endemicity for eastern equine encephalitis virus (EEEV) of any state in the United States and is the only state with year-round transmission of EEEV. To further understand the viral population dynamics in Florida, the genome sequence of six EEEV isolates from central Florida were determined. These data were used to identify the most polymorphic regions of the EEEV genome from viruses isolated in Florida. The sequence of these polymorphic regions was then determined for 18 additional Florida isolates collected in four geographically distinct regions over a 20-year period. Phylogenetic analyses of these data suggested a rough temporal association of the Florida isolates, but no clustering by region or by source of the isolate. Some clustering of northeastern isolates with Florida isolates was seen, providing support for the hypothesis that Florida serves as a reservoir for the periodic introduction of EEEV into the northeastern United States.
PMCID: PMC3083737  PMID: 21540379
5.  A Multi-Year Study of Mosquito Feeding Patterns on Avian Hosts in a Southeastern Focus of Eastern Equine Encephalitis Virus 
Eastern equine encephalitis virus (EEEV) is a mosquito-borne pathogen that cycles in birds but also causes severe disease in humans and horses. We examined patterns of avian host use by vectors of EEEV in Alabama from 2001 to 2009 using blood-meal analysis of field-collected mosquitoes and avian abundance surveys. The northern cardinal (Cardinalis cardinalis) was the only preferred host (fed on significantly more than expected based on abundance) of Culiseta melanura, the enzootic vector of EEEV. Preferred hosts of Culex erraticus, a putative bridge vector of EEEV, were American robin (Turdus migratorius), Carolina chickadee (Poecile carolinensis), barred owl (Strix varia), and northern mockingbird (Mimus polyglottis). Our results provide insight into the relationships between vectors of EEEV and their avian hosts in the Southeast and suggest that the northern cardinal may be important in the ecology of EEEV in this region.
PMCID: PMC3083738  PMID: 21540380
6.  Polymerase Chain Reaction Pool Screening Used To Compare Prevalence of Infective Black Flies in Two Onchocerciasis Foci in Northern Sudan 
Onchocerciasis remains an important debilitating disease in many areas of Africa, including Sudan. The status of infection transmission in 2007 was assessed in the vectors of two disease foci in Sudan: Abu Hamed in northern Sudan, which has received at least 10 years of annual treatment and Galabat focus in eastern Sudan, where only minor, largely undocumented treatment activity has occurred. Assessment of more than 30,000 black flies for Onchocerca volvulus infectious stage L3 larvae by using an O-150 polymerase chain reaction protocol showed that black fly infectivity rates were 0.84 (95% confidence interval = 0.0497–1.88) per 10,000 flies for Abu Hamed and 6.9 (95% confidence interval = 1.1–16.4) infective flies per 10,000 for Galabat. These results provide entomologic evidence for suppressed Onchocerca volvulus transmission in the Abu Hamed focus and a moderate transmission rate of the parasite in the Galabat focus.
PMCID: PMC3083743  PMID: 21540385
7.  Vector–Host Interactions in Avian Nests: Do Mosquitoes Prefer Nestlings over Adults? 
The hypothesis that nestlings are a significant driver of arbovirus transmission and amplification is based upon findings that suggest nestlings are highly susceptible to being fed upon by vector mosquitoes and to viral infection and replication. Several previous studies have suggested that nestlings are preferentially fed upon relative to adults in the nest, and other studies have reported a preference for adults over nestlings. We directly tested the feeding preference of nestling and adult birds in a natural setting, introducing mosquitoes into nesting boxes containing eastern bluebirds (Sialia sialis), collecting blood-fed mosquitoes, and matching the source of mosquito blood meals to individual birds using microsatellite markers. Neither nestlings nor adults were fed upon to an extent significantly greater than would be predicted based upon their relative abundance in the nests, although feeding upon mothers decreased as the age of the nestlings increased.
PMCID: PMC2911192  PMID: 20682889
8.  Lack of Active Onchocerca volvulus Transmission in the Northern Chiapas Focus of Mexico 
The northern Chiapas onchocerciasis focus has undergone 11 years of ivermectin mass treatment. No evidence of microfilariae in the cornea and/or anterior chamber of the eye or in skin snips was seen in residents examined in 2006 in two sentinel communities (upper limit of the 95% confidence interval [UL 95% CI] = 0.5% and 0.3%, respectively). In children 10 and under, 0 of 305 were found to harbor antibodies to Ov16, a marker of parasite exposure; 0 of 4,400 Simulium ochraceum s.l. collected in 2005 contained parasite DNA, giving an UL 95% CI for the infective rate of 0.9/2,000, and an UL 95% CI of the seasonal transmission potential of 1.2 L3/person. These data, assumed to be representative of the focus as a whole, suggest that there is no ongoing transmission of Onchocerca volvulus in the northern Chiapas focus. Community-wide treatments with ivermectin were halted in 2008, and a post-treatment surveillance phase was initiated.
PMCID: PMC2912569  PMID: 20595471
9.  Interruption of Transmission of Onchocerca volvulus in the Oaxaca Focus, Mexico 
All endemic communities of the Oaxaca focus of onchocerciasis in southern Mexico have been treated annually or semi-annually with ivermectin since 1994. In-depth epidemiologic assessments were performed in communities during 2007 and 2008. None of the 52,632 Simulium ochraceum s.l. collected in four sentinel communities was found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the infection rate in the vectors of 0.07/2,000. The prevalence of microfilariae (mf) in the cornea and/or anterior chamber of the eye was also zero (0 of 1,039 residents examined; 95%-UL = 0.35%). Similarly, all 1,164 individuals examined by skin biopsy were mf negative (95%-UL = 0.31%), and sera collected from 3,569 children from 25 communities did not harbor Ov16 IgG4-antibodies (95%-UL = 0.09%). These meet the criteria for absence of morbidity and parasite transmission in the Oaxaca focus. As a result mass treatments with ivermectin were halted in 2009.
PMCID: PMC2912570  PMID: 20595472
10.  Rapid Suppression of Onchocerca volvulus Transmission in Two Communities of the Southern Chiapas Focus, Mexico, Achieved by Quarterly Treatments with Mectizan 
The impact of quarterly Mectizan (ivermectin) treatments on transmission, microfiladermia, and ocular lesions was evaluated in two formerly hyperendemic communities (Las Golondrinas and Las Nubes II) located in the main endemic focus for onchocerciasis in Southern Chiapas, Mexico. The data suggest that Onchocerca volvulus transmission has been suppressed after elimination of microfiladermia in these two communities. Increasing the frequency of Mectizan treatment to four times per year appears to have resulted in the rapid suppression of transmission in communities with residual transmission.
PMCID: PMC2570542  PMID: 18689630

Results 1-10 (10)