Paul T. Oesterle

North American Birds as Potential Amplifying Hosts of Japanese Encephalitis Virus

Japanese encephalitis virus (JEV) is an emerging arbovirus, and inter-continental spread is an impending threat. The virus is maintained in a transmission cycle between mosquito vectors and vertebrate hosts, including birds. We detected variation in interspecies responses among North American birds to infection with strains of two different JEV genotypes (I and III). Several native North American passerine species and ring-billed gulls had the highest average peak viremia titers after inoculation with a Vietnamese (genotype I) JEV strain. Oral JEV shedding was minimal and cloacal shedding was rarely detected. The majority of birds, both viremic (72 of 74; 97.3%) and non-viremic (31 of 37; 83.8%), seroconverted by 14 days post-inoculation and West Nile virus-immune individuals had cross-protection against JEV viremia. Reservoir competence and serologic data for a variety of avian taxa are important for development of JEV surveillance and control strategies and will aid in understanding transmission ecology in the event of JEV expansion to North America.

Experimental infection of cliff swallows (Petrochelidon pyrrhonota) with varying doses of West Nile virus

Cliff swallows (Petrochelidon pyrrhonota) were inoculated with differing doses of West Nile virus (WNV) to evaluate their potential role as reservoir hosts in nature. Swallows often nest in large colonies in habitats and months associated with high mosquito abundance and early WNV transmission in North America. Additionally, cliff swallow diet consists of insects, including mosquitoes, leading to an additional potential route of WNV infection. The average peak viremia titer among infected cliff swallows was 10(6.3) plaque-forming units (PFU)/mL serum and the reservoir competence index was 0.34. There was no correlation between dose and probability of becoming infected or viremia peak and duration. Oral shedding was detected from 2 to 14 days post-inoculation with an average peak titer of 10(4.4) PFU/swab. These results suggest that cliff swallows are competent reservoir hosts of WNV and therefore, they may play a role in early seasonal amplification and maintenance of WNV.

Cliff Swallows, Swallow Bugs, and West Nile Virus: An Unlikely Transmission Mechanism

The cliff swallow (Petrochelidon pyrrhonota) could play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. Cliff swallows nest within colonies and their nests are occupied year-round by swallow bugs (Oeciacus vicarius), hematophagus ectoparasites that feed primarily on cliff swallows. These parasites are likely exposed to WNV while feeding on infectious blood of nesting cliff swallow adults and nestlings and thus, if competent vectors, could contribute to seasonal elevations in WNV transmission. In addition, swallow bugs remain within nests year-round and therefore could provide a potential overwintering mechanism for WNV if persistently infected. To test the hypotheses that swallow bugs are competent vectors and become persistently infected with WNV, we experimentally inoculated cliff swallow nestlings, allowed swallow bugs to feed on these birds during the acute phase of infection, and then exposed naive cliff swallow nestlings to the same swallow bugs. In addition, a subset of swallow bugs that fed on infectious swallow nestlings was maintained through a simulated overwintering period. Although swallow bugs ingested infectious blood (up to 10(6.8) plaque-forming units of WNV/mL serum) and subsequently blood-fed on naive swallows, no WNV transmission was detected, and all bugs tested WNV negative after the simulated overwintering period. Although many ecologic scenarios exist beyond the present study, our results suggest that swallow bugs may be unlikely to serve as competent biological vectors for WNV during active transmission periods or to reinitiate seasonal transmission.

Experimental infection of European starlings (Sturnus vulgaris) and house sparrows (Passer domesticus) with pandemic 2009 H1N1 and swine H1N1 and H3N2 triple reassortant influenza viruses.

European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus) are common peridomestic passerine birds that are often associated with domestic animal production facilities. This association provides a potential means for pathogen transmission between facilities. We inoculated European Starlings and House Sparrows with three nonavian influenza virus strains: two swine isolates (H1N1 and H3N2) and one human isolate representing the H1N1 pandemic strain that originated from swine. No viral shedding was observed in House Sparrows, and shedding was minimal and transient in two of 12 (17%) European Starlings. One of these two infected Starlings seroconverted 14 days after inoculation. These results suggest that these two passerine species are minimally susceptible to current influenza viruses in domestic pigs and therefore pose a negligible risk for transmission between or within swine production facilities.

Experimental Exposure of Swallow Bugs (Hemiptera: Cimicidae) to West Nile Virus

ABSTRACT The cliff swallow (Petrochelidon pyrrhonota, Vieillot) could potentially play an important role in the transmission of West Nile virus (WNV) because of its breeding ecology, reservoir competence status, and potentially high natural exposure rates. These birds nest in colonies and their nests are occupied year round by swallow bugs (Oeciacus vicarius, Hovarth), hematophagus ectoparasites that feed primarily on cliff swallows. Swallow bugs are most likely exposed to WNV while feeding on infectious blood of cliff swallows and, thus, if competent vectors, could contribute to initiation and maintenance of seasonal WNV transmission. In addition, swallow bugs remain within nests year round and, therefore, if persistently infected and competent vectors, they could provide an overwintering mechanism for WNV. We tested the hypothesis that swallow bugs become infected with WNV through direct abdominal inoculation or ingestion of infectious blood meals. We observed that swallow bugs did not maintain or amplify WNV, and infectious virus titers within bugs declined over 15 d postexposure. These results suggest that swallow bugs may not be competent vectors of WNV, and therefore are unlikely to play a significant role in transmission.

Husbandry of wild-caught greater sage-grouse

Abstract This study reports the first successful husbandry and breeding in captivity of wild-caught greater sage-grouse (Centrocercus urophasianus). In October 2003, 21 hatch-year greater sage-grouse were trapped in northwestern Nevada and transported to Fort Collins, Colorado. We held grouse in pens at the United States Department of Agricultures National Wildlife Research Center for 8 months. We offered a varied diet, including native food items such as sagebrush (Artemisia tridentata and A. tripartita) and yarrow (Achillea millefolium). We housed grouse in a large flight pen and allowed to them free range as one flock. Mortality rate was 16.7%. Several of the grouse exhibited breeding behavior, and 13eggs were laid. We describe the techniques used to house and feed wild-caught sage-grouse. This study has conservation implications for captive breeding of this species of concern.

Red Fox as Sentinel for Blastomyces dermatitidis, Ontario, Canada.

Blastomyces dermatitidis, a fungus that can cause fatal infection in humans and other mammals, is not readily recoverable from soil, its environmental reservoir. Because of the red fox’s widespread distribution, susceptibility to B. dermatitidis, close association with soil, and well-defined home ranges, this animal has potential utility as a sentinel for this fungus.