Two Rhabdoviridae: Dillard's Draw virus, a putative new virus, and Merida virus from Culex tarsalis (Diptera: Culicidae) in New Mexico, USA.

The U.S. Air Force conducts vector and arbovirus surveillance worldwide. We report on two Rhabdoviridae detected at Holloman Air Force Base in Otero County, New Mexico including the nearly complete 11-kb genome of Merida virus, which was not previously known from the USA, and a novel virus tentatively named Dillard's Draw virus. Merida virus was previously only known from Mexico. Dillard's Draw virus represents a novel arbovirus most closely related to an avian pathogen from Australia and shares some genetic similarity to Durham virus from the eastern United States.

Detection of bluetongue virus RNA in field-collected Culicoides spp. (Diptera: Ceratopogonidae) following the discovery of bluetongue virus serotype 1 in white-tailed deer and cattle in Louisiana.

In November 2004, bluetongue virus (family Reoviridae, genus Orbivirus, BTV) serotype 1 (BTV-1) was detected for the first time in the United States from a hunter-killed deer in St. Mary Parish, LA. In 2005, sera surveys were conducted on three cattle farms near the area where the deer was found, and BTV-1-seropositive cattle were found on two of the three farms; in 2006, sera surveys from the cattle on the three farms did not detect any BTV-1-positive animals. The purpose of this study was to survey ceratopogonid populations at the three farms and test field-collected specimens for the presence of BTV and epizootic hemorrhagic disease virus (family Reoviridae, genus Orbivirus, EHDV). Miniature CDC light traps and New Jersey traps were used to capture ceratopogonids on the three farms from January 2006 through November 2007. In total, 3,319 ceratopogonids were captured, including 1,790 specimens of 10 different species of Culicoides. IR-RT-polymerase chain reaction (PCR) was performed to screen for BTV and EHDV in 264 pools representing 2,309 specimens collected at the farms. All positive samples were sequenced for serotype determination. Five pools of 275 (1.8%) were positive for BTV. Pools of four species of Culicoides were found to be positive: Culicoides crepuscularis (Malloch), Culicoides debilipalpis Lutz (two pools), Culicoides haematopotus Malloch, and Gulicoidesfurens (Poey). The amplicons of the positive specimens were sequenced and found to be identical to both BTV-17 and BTV-13. During our study, no BTV-1 transmission was detected in cattle, and no BTV-1 was detected in specimens of ceratopogonids.

Age-grading the biting midge Culicoides sonorensis using near-infrared spectroscopy.

Age-grading of insects is important in the control and monitoring of both insect populations and vector-borne diseases. Microscopy and morphological techniques exist to age-grade most blood-feeding flies, but these techniques are laborious, often destructive to the insects, and slow. Near-infrared spectroscopy (NIRS) can be automated and is a non-destructive technique for age-grading. We applied NIRS techniques to age-grade females of the biting midge, Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae), the vector of bluetongue and other arboviruses in North America. Female flies of five known age cohorts (1, 3, 6, 9 and 12 days post-emergence) from three laboratory colonies were used. The data indicate that NIRS can be used to differentiate age groups of C. sonorensis.

Control of Culicoides sonorensis (Diptera: Ceratopogonidae) blood feeding on sheep with long-lasting repellent pesticides.

Culicoides sonorensis is the primary vector of bluetongue and epizootic hemorrhagic disease viruses in North America. Bluetongue disease is one of the most economically important arthropod-borne diseases of sheep in North America, because it causes significant morbidity and mortality and can lead to local quarantines and international trade restrictions. Long-lasting repellent pesticides could be applied to sheep as they are moved down from mountain pastures to protect them from biting midges until the 1st frost. We tested long-lasting pesticides on sheep as repellents against C. sonorensis. Both Python ear tags with 10% zeta-cypermethrin (9.8 g/tag) synergized with 20% piperonyl butoxide (PBO) and a 12-ml low-volume spray application of ready-to-use sheep insecticide (Y-TEX) with 2.5% permethrin and 2.5% PBO in an oil-based formulation were repellent to C. sonorensis for at least 3-5 wk after a single application.

Temporal distribution of Smittium culisetae in a wild population of Wyeomyia smithii from pitcher plants.

The fungus Smittium culisetae is a trichomycete that develops in the hindguts of larval aquatic Diptera. This is the first report of S. culisetae from the pitcher plant mosquito, Wyeomyia smithii. Larvae of the mosquito were collected from the purple pitcher plant, Sarracenia purpurea, from a bog in Jackson County, North Carolina. The lowest proportions of colonized larvae occurred in December, January and July. The greatest proportions of colonized larvae occurred in October and March. The distribution of colonized larvae among pitchers did not differ significantly from a random distribution.

Oviposition by Aedes aegypti (Diptera: Culicidae) in relation to conspecific larvae infected with internal symbiotes.

Female mosquitoes use abiotic and biotic factors, such as the presence of heavy metals or parasites, to determine the acceptability of oviposition sites. Some biotic factors can originate from mosquito larvae. When mosquito larvae are starved or infected with trematode metacercaria, they render associated water unacceptable to ovipositioning females. Internal symbiotes are common in wild mosquito populations, and I tested whether or not larvae of Aedes aegypti infected with a gregarine (Ascogregarina taiwanensis), a yeast (Candida near pseudoglaebosa), or a trichomycete (Smittium morbosum) rendered their rearing water unacceptable to oviposting mosquitoes. Infections with S. morbosum had no effect on the acceptability of the associated rearing water when compared to rearing water from uninfected larvae. However, the rearing water from larvae infected with A. taiwanensis or C. near pseudoglaebosa was more acceptable to ovipositing females than was distilled water or rearing water from uninfected larvae. Ovipositing female mosquitoes either preferred or were neutral to rearing water from larvae with gut symbiotes.

A survey of zoonotic pathogens carried by Norway rats in Baltimore, Maryland, USA.

Norway rats (Rattus norvegicus) carry several zoonotic pathogens and because rats and humans live in close proximity in urban environments, there exists potential for transmission. To identify zoonotic agents carried by rats in Baltimore, Maryland, USA, we live-trapped 201 rats during 2005-2006 and screened them for a panel of viruses, bacteria, and parasites. Antibodies against Seoul virus (57.7%), hepatitis E virus (HEV, 73.5%), Leptospira interrogans (65.3%), Bartonella elizabethae (34.1%), and Rickettsia typhi (7.0%) were detected in Norway rats. Endoparasites, including Calodium hepatica (87.9%) and Hymenolepis sp. (34.4%), and ectoparasites (13.9%, primarily Laelaps echidninus) also were present. The risk of human exposure to these pathogens is a significant public health concern. Because these pathogens cause non-specific and often self-limiting symptoms in humans, infection in human populations is probably underdiagnosed.

Trichomycete symbiotes of Crozetia seguyi, a primitive black fly.

Crozetia is a genus of black flies endemic to the Crozet Islands in the Indian Ocean. No internal symbiotes were previously known from Crozetia species. We report two species of trichomycete symbiotes Stachylina litoralis and Smittium culicisoides from Crozetia seguyi. Larvae of C. seguyi were examined from three sites. The infection rates for St. litoralis was 10.0-33.3% (n=47) of the larvae and Sm. culicisoides was 46.1-85.7% (n=47). No other symbiotes were discovered.