Pathogenesis of Vesicular Stomatitis New Jersey Virus Infection in Deer Mice ( Peromyscus maniculatus) Transmitted by Black Flies ( Simulium vittatum).

The natural transmission of vesicular stomatitis New Jersey virus (VSNJV), an arthropod-borne virus, is not completely understood. Rodents may have a role as reservoir or amplifying hosts. In this study, juvenile and nestling deer mice ( Peromyscus maniculatus) were exposed to VSNJV-infected black fly ( Simulium vittatum) bites followed by a second exposure to naive black flies on the nestling mice. Severe neurological signs were observed in some juvenile mice by 6 to 8 days postinoculation (DPI); viremia was not detected in 25 juvenile deer mice following exposure to VSNJV-infected fly bites. Both juvenile and nestling mice had lesions and viral antigen in the central nervous system (CNS); in juveniles, their distribution suggested that the sensory pathway was the most likely route to the CNS. In contrast, a hematogenous route was probably involved in nestling mice, since all of these mice developed viremia and had widespread antigen distribution in the CNS and other tissues on 2 DPI. VSNJV was recovered from naive flies that fed on viremic nestling mice. This is the first report of viremia in a potential natural host following infection with VSNJV via insect bite and conversely of an insect becoming infected with VSNJV by feeding on a viremic host. These results, along with histopathology and immunohistochemistry, show that nestling mice have widespread dissemination of VSNJV following VSNJV-infected black fly bite and are a potential reservoir or amplifying host for VSNJV.

Host and Potential Vector Susceptibility to an Emerging Orbivirus in the United States: Epizootic Hemorrhagic Disease Virus Serotype 6.

Epizootic hemorrhagic disease viruses (EHDVs) are orbiviruses transmitted by Culicoides biting midges to domestic and wild ruminants. EHDV-1 and EHDV-2 are endemic in the United States, where epizootic hemorrhagic disease is the most significant viral disease of white-tailed deer (WTD;Odocoileus virginianus) and reports of epizootic hemorrhagic disease in cattle are increasing. In 2006, a reassortant EHDV-6 was isolated from dead WTD in Indiana and has been detected each subsequent year over a wide geographic region. Since EHDV-6 is not a historically endemic serotype in the United States, it is important to understand infection outcome in potential hosts. Specifically, we aimed to evaluate the pathogenicity of the virus in 2 primary US ruminant hosts (WTD and cattle) and the susceptibility of a confirmed US vector (Culicoides sonorensis). Five WTD and 4 cattle were inoculated with >10(6)TCID50EHDV-6 by intradermal and subcutaneous injection. All 5 WTD exhibited moderate to severe disease, and 3 died. Viremia was first detected 3 to 5 days postinfection (dpi) with surviving animals seroconverting by 10 dpi. Two of 4 inoculated cattle had detectable viremia, 5 to 10 dpi and 7 to 24 dpi, respectively. No clinical, hematologic, or pathologic abnormalities were observed. Antibodies were detected by 10 dpi in 3 of 4 cows.C. sonorensis were fed on WTD blood spiked with EHDV-6 and held for 4 to 14 days postfeeding at 25°C. From 4 to 14 days postfeeding, 19 of 171 midges were virus isolation positive and 6 of 171 had ≥10(2.7)TCID50EHDV-6. Although outcomes varied, these studies demonstrate the susceptibility of ruminant and vector hosts in the United States for this recently emerged EHDV serotype.

Evolutionary dynamics of West Nile virus in Georgia, 2001-2011.

From 1999-2001, West Nile virus (WNV) spread throughout the eastern United States (US) and was first detected in Georgia in 2001. To date, the virus has been detected in over 2,500 dead wild bird and mosquito samples from across Georgia. We sequenced the premembrane (preM) and envelope gene (E) (2004 bp) from 111 isolates collected from 2001 to 2011. To assess viral gene flow from other geographic regions in the US, we combined our data with WNV sequences available at the National Center for Biotechnology Information (NCBI) and performed phylogenetic analysis. We found evidence that WNV isolates detected in Chatham County Georgia most likely originated from the Northeastern United States. These results highlight the growing importance of adequate genetic surveillance for monitoring and controlling viruses of public health concern.

First report of clinical disease associated with canine distemper virus infection in a wild black bear (Ursus americana).

An approximately 1-yr-old black bear was discovered on the porch of a rural residence in southwestern Pennsylvania on October 26, 2011, where it remained during the day in spite of efforts to frighten it away. The bear exhibited periods of somnolence and sporadic tremors and seizures. It was euthanized by gunshot that evening. Immediately after euthanasia it was observed to have footpads that exuded fluid when compressed. It was submitted for necropsy the next day where roughened footpads were noted. Histologic examination of the brain demonstrated nonsuppurative encephalitis with eosinophilic intranuclear and intracytoplasmic inclusion bodies in neurons. The footpads were thickened and hyperkeratotic. Canine distemper virus (CDV) was detected by immunohistochemistry (IHC) in the brain and footpads, and by reverse transcription polymerase chain reaction (RT-PCR) from the brain tissue. Phylogenetic analysis indicated that the CDV cDNA from the bear had 98.2% nucleotide identity to the Rockborn-Candur vaccine and a canine isolate from 2004 in Missouri, USA, and 97.3% nucleotide identity to a raccoon CDV isolated in 2011 from Tennessee, USA. This represents a first report of CDV as a cause of encephalitis or footpad hyperkeratosis in a wild black bear.

Lesion development and replication kinetics during early infection in cattle inoculated with Vesicular stomatitis New Jersey virus via scarification and black fly (Simulium vittatum) bite.

Vesicular stomatitis viruses are the causative agents of vesicular stomatitis, an economically important contagious disease of livestock that occurs in North, Central, and South America. Little is known regarding the early stages of infection in natural hosts. Twelve adult Holstein steers were inoculated with Vesicular stomatitis New Jersey virus (VSNJV) on the coronary bands (CB) of the feet via scarification (SC) or by VSNJV-infected black fly (Simulium vittatum) bite (FB). Three additional animals were inoculated on the neck skin using FB. Clinical disease and lesion development were assessed daily, and animals were euthanatized from 12 hours post inoculation (HPI) through 120 HPI. The animals inoculated in the neck failed to develop any clinical signs or gross lesions, and VSNJV was detected neither by in situ hybridization (ISH) nor by immunohistochemistry (IHC). Lesions on the CB were more severe in the animals infected by FB than by SC. In both groups, peak VSNJV replication occurred between 24 and 48 HPI in keratinocytes of the CB, as evidenced by ISH and IHC. There was evidence of viral replication limited to the first 24 HPI in the local draining lymph nodes, as seen through ISH. Successful infection via FB required logarithmically less virus than with the SC technique, suggesting that components in black fly saliva may facilitate VSNJV transmission and infection in cattle. The lack of lesion development in the neck with the same method of inoculation used in the CB suggests that specific characteristics of the CB epithelium may facilitate VSNJV infection.

Domestic cattle as a non-conventional amplifying host of vesicular stomatitis New Jersey virus.

The role of vertebrates as amplifying and maintenance hosts for vesicular stomatitis New Jersey virus (VSNJV) remains unclear. Livestock have been considered dead-end hosts because detectable viraemia is absent in VSNJV-infected animals. This study demonstrated two situations in which cattle can represent a source of VSNJV to Simulium vittatum Zetterstedt (Diptera: Simuliidae) by serving: (a) as a substrate for horizontal transmission among co-feeding black flies, and (b) as a source of infection to uninfected black flies feeding on sites where VSNJV-infected black flies have previously fed. Observed co-feeding transmission rates ranged from 0% to 67%. Uninfected flies physically separated from infected flies by a distance of up to 11 cm were able to acquire virus during feeding although the rate of transmission decreased as the distance between infected and uninfected flies increased. Acquisition of VSNJV by uninfected flies feeding on initial inoculation sites at 24 h, 48 h and 72 h post-infection, in both the presence and absence of vesicular lesions, was detected.

Canine distemper epizootic in Everglades mink.

Four free-ranging mink, Neovison vison, collected between June and September 2004 in the Fakahatchee Strand Preserve State Park (FSPSP, Florida, USA), were examined for canine distemper virus (CDV) infection. Microscopic lesions and viral inclusions consistent with CDV infection were observed in three mink. Virus isolation and reverse transcription-polymerase chain reaction performed on all mink were positive for CDV. Anecdotal records of mink observations in FSPSP suggest a postepizootic decline in the mink population followed by an apparent recovery. We recommend further research to assess the status of the Everglades mink and the impact of CDV on this and other American mink populations in Florida.

Experimental transmission of vesicular stomatitis New Jersey virus from Simulium vittatum to cattle: clinical outcome is influenced by site of insect feeding.

Vesicular stomatitis New Jersey virus (VSNJV) is an insect-transmitted Rhabdovirus causing vesicular disease in domestic livestock including cattle, horses, and pigs. Natural transmission during epidemics remains poorly understood, particularly in cattle, one of the most affected species during outbreaks. This study reports the first successful transmission of VSNJV to cattle by insect bite resulting in clinical disease. When infected black flies (Simulium vittatum Zetterstedt) fed at sites where VS lesions are usually observed (mouth, nostrils, and foot coronary band), infection occurred, characterized by local viral replication, vesicular lesions, and high neutralizing antibody titers (> 1: 256). Viral RNA was detected up to 9 d postinfection in tissues collected during necropsy from lesion sites and lymph nodes draining those sites. Interestingly, when flies were allowed to feed on flank or neck skin, viral replication was poor, lesions were not observed, and low levels of neutralizing antibodies (range, 1:8-1:32) developed. Viremia was never observed in any of the animals and infectious virus was not recovered from tissues on necropsies performed between 8 and 27 d postinfection. Demonstration that VSNJV transmission to cattle by infected black flies can result in clinical disease contributes to a better understanding of the epidemiology and potential prevention and control methods for this important disease.

Experimental vesicular stomatitis virus infection in horses: effect of route of inoculation and virus serotype.

Horses were inoculated with Vesicular stomatitis New Jersey and Indiana viruses by routes simulating contact and vector transmission. Clinical signs, lesions, antibody development, viral shedding and persistence, and viremia were monitored. Horses were infected with both viruses by all routes as confirmed by seroconversion. Salivation, primary lesions at inoculation sites, and secondary oral lesions were the most common clinical findings. Viral shedding was most often from the oral cavity, followed by the nasal cavity; titers were highest from oral cavity samples. Virus was rarely isolated from the conjunctival sac and never from feces or blood. Development of neutralizing antibody coincided with cessation of lesion development and detection of virus by isolation. Circulating virus-specific IgM, IgG, IgA, and neutralizing antibodies developed in most animals postinoculation (PI) days 6 to 12, depending on the route of inoculation. At postmortem (PI days 12 to 15), lesions were healing, were not vesicular, and did not contain detectable virus by isolation, reverse transcriptase polymerase chain reaction, or immunohistochemistry. Numerous infiltrating lymphocytes and plasma cells suggested that lesion resolution was partially due to local immunity. Detection of viral RNA from tonsil and lymph nodes of head at necropsy suggests that these tissues play a role in the pathogenesis of the disease; molecular techniques targeting these tissues may be useful for confirming infection in resolving stages of disease. The routes of inoculation used in this study reflect the diversity of transmission routes that may occur during outbreaks and can be used to further study contact and vector transmission, vaccine development, and clarify pathogenesis of the disease in horses.

Occurrence of Anopheles hermsi (Diptera: Culicidae) in Arizona and Colorado.

Historically, malaria was a significant cause of morbidity and mortality throughout the western United States, and Anopheles freeborni Aitken was thought to be the vector west of the Continental Divide. In 1989, Anopheles hermsi Barr & Guptavanij was described and subsequently found to be an effective laboratory vector of Plasmodium. The adults of these two species are morphologically indistinguishable, and therefore polymerase chain reaction was used to analyze the DNA from 48 mosquitoes collected in Arizona and Colorado (identified morphologically as An. freeborni). All specimens were identified as An. hermsi. This was the first report of An. hermsi in Arizona and Colorado and indicated that this Anopheles species historically may have been a malaria vector in these two western states.

Transmission of vesicular stomatitis virus from infected to noninfected black flies co-feeding on nonviremic deer mice.

Vesicular stomatitis is an economically important arboviral disease of livestock. Viremia is absent in infected mammalian hosts, and the mechanism by which insects become infected with the causative agents, vesicular stomatitis viruses, remains unknown. Because infected and noninfected insects potentially feed on the same host in nature, infected and noninfected black flies were allowed to feed on the same host. Viremia was not detected in the host after infection by a black fly bite, but because noninfected black flies acquired the virus while co-feeding on the same host with infected black flies, it is concluded that a viremic host is not necessary for an insect to be infected with the virus. Thus co-feeding is a mechanism of infection for an insect-transmitted virus.

Laboratory vector competence of black flies (Diptera:Simuliidae) for the Indiana serotype of vesicular stomatitis virus.

In previous experiments we have demonstrated that colonized and wild black flies are competent laboratory vectors of different Mexican and Western USA isolates of vesicular stomatitis virus, serotype New Jersey (VSV-NJ). We have recently demonstrated biological VSV-NJ transmission by black flies using animal models. In the study described here, we tested the vector competence of colonized and wild black flies for the vesicular stomatitis virus, serotype Indiana (VSV-IN). A 1998 equine isolate was used. After a 10 day incubation period, saliva from experimentally infected Simulium vittatum and S. notatum was individually collected and tested for the presence of infectious virus. Virus was detected in the saliva of both species following oral infection, indicating that they are competent laboratory vectors of VSV-IN. In addition, the results suggest that the black fly gut may exert evolutionary pressures on the virus.

Bite transmission of vesicular stomatitis virus (New Jersey serotype) to laboratory mice by Simulium vittatum (Diptera: Simuliidae).

Laboratory-reared female black flies (Simulium vittatum Zetterstedt) were infected experimentally with a 1997 vesicular stomatitis virus New Jersey serotype isolate and allowed to feed on susceptible laboratory mice. All mice exposed to black fly bite seroconverted by day 21 after infection, an indication of virus transmission. In addition, viral RNA was detected in the spleen of several mice. These findings are consistent with the hypothesis that black flies are involved in VSV-NJ transmission during epizootics in the western USA and represent the 1st confirmed example of biological transmission of an arbovirus by a member of the Simuliidae using an animal model.

Vector competence of select black fly species for vesicular stomatitis virus (New Jersey serotype).

Black flies collected from southern Arizona were evaluated for their vector competence to the Oaxaca and Camp Verde isolates of vesicular stomatitis virus (New Jersey serotype) (VSV-NJ). The Camp Verde isolate is the index isolate of the 1982-1983 VSV-NJ epizootic that infected humans and livestock in 14 western states. Previous experiments have shown that colonized Simulium vittatum females are competent laboratory vectors of both virus isolates. However, under controlled laboratory conditions, Simulium bivittatum and S. longithallum were found to be incompetent vectors of both virus isolates. After oral infections, the Oaxaca isolate replicated in 35% and 38% of S. bivittatum and S. longithallum, respectively, but did not disseminate to the salivary glands. Thus, virus was not detected in the saliva of either black fly species with either VSV-NJ isolate, indicating the presence of a midgut barrier. Simulium notatum was found to be a competent laboratory vector of both virus isolates. Infectious virions were detected in the saliva of 23% and 26% of S. notatum infected orally with the Oaxaca and Camp Verde VSV-NJ isolates, respectively. This study suggests that the black fly identified as S. bivittatum was probably not involved in virus dissemination during the 1982-1983 epizootic in the western United States. Because the geographic distribution of S. notatum is not known, its involvement in that epizootic remains obscure.

Occurrence of Lutzomyia anthophora (Diptera: Psychodidae) in Arizona.

Males and females of Lutzomyia anthophora Addis were collected by vacuum aspiration from woodrat, Neotoma albigula Hartley, and rock squirrel, Citellus variegatus Bailey, nests along Arivaca Creek in Pima County, Arizona. Additional flies were collected from the same location using CDC miniature light traps supplemented with CO2. These collections extend the recorded geographic distribution of this vector of Leishmania mexicana Biagi westward by approximately 724 km and place Lu. anthophora in a Sonoran desert habitat.