Expression and distribution of sialic acid influenza virus receptors in wild birds.

Avian influenza (AI) viruses have been detected in more than 105 wild bird species from 12 different orders but species-related differences in susceptibility to AI viruses exist. Expression of α2,3-linked (avian-type) and α2,6-linked (human-type) sialic acid (SA) influenza virus receptors in tissues is considered one of the determinants of the host range and tissue tropism of influenza viruses. We investigated the expression of these SA receptors in 37 wild bird species from 11 different orders by lectin histochemistry. Two isoforms of Maackia amurensis (MAA) lectin, MAA1 and MAA2, were used to detect α2,3-linked SA, and Sambucus nigra lectin was used to detect α2,6-linked SA. All species evaluated expressed α2,3-linked and α2,6-linked SA receptors in endothelial cells and renal tubular epithelial cells. Both α2,3-linked and α-2,6-linked SA receptors were expressed in respiratory and intestinal tract tissues of aquatic and terrestrial wild bird species from different taxa, but differences in SA expression and in the predominant isoform of MAA lectin bound were observed. With a few possible exceptions, these observed differences were not generally predictive of reported species susceptibility to AI viruses based on published experimental and field data.

Genomic sequencing of Highlands J virus: a comparison to western and eastern equine encephalitis viruses.

Highlands J virus (HJV) is a member of the genus Alphavirus, family Togaviridae. HJV is the sole representative of the western equine encephalitis (WEE) serocomplex found in the eastern United States, and circulates in nature in an apparently identical transmission cycle as eastern equine encephalitis virus (EEEV). North American representatives of the WEE serocomplex [HJV, WEE virus (WEEV), and Fort Morgan virus (FMV)] are believed to be derived from a recombination event involving EEEV and a Sindbis (SIN)-like virus, such that the nonstructural polyprotein, the capsid, and the terminal end of the 3' UTR are derived from EEEV, while the surface glycoproteins (E1 and E2) and small peptides (E3 and 6K) encoded in the subgenomic RNA are derived from the SIN-like virus. In this report, the complete nucleotide sequence of HJV is described, along with a comparative analysis of the HJV nonstructural polyprotein to WEEV and EEEV.

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.

Contact transmission of vesicular stomatitis virus New Jersey in pigs.

OBJECTIVE: To determine how viral shedding and development or lack of clinical disease relate to contact transmission of vesicular stomatitis virus New Jersey (VSV-NJ) in pigs and determine whether pigs infected by contact could infect other pigs by contact. ANIMALS: 63 pigs. PROCEDURE: Serologically naive pigs were housed in direct contact with pigs that were experimentally inoculated with VSV-NJ via ID inoculation of the apex of the snout, application to a scarified area of the oral mucosa, application to intact oral mucosa, or ID inoculation of the ear. In a second experiment, pigs infected with VSV-NJ by contact were moved and housed with additional naive pigs. Pigs were monitored and sampled daily for clinical disease and virus isolation and were serologically tested before and after infection or contact. RESULTS: Contact transmission developed only when vesicular lesions were evident. Transmission developed rapidly; contact pigs shed virus as early as 1 day after contact. In pens in which contact transmission was detected, 2 of 3 or 3 of 3 contact pigs were infected. CONCLUSIONS AND CLINICAL RELEVANCE: Transmission was lesion-dependent; however, vesicular lesions often were subtle with few or no clinical signs of infection. Contact transmission was efficient, with resulting infections ranging from subclinical (detected only by seroconversion) to clinical (development of vesicular lesions). Long-term maintenance of VSV-NJ via contact transmission alone appears unlikely. Pigs represent an efficient large-animal system for further study of VSV-NJ pathogenesis and transmission.

Experimental vesicular stomatitis in swine: effects of route of inoculation and steroid treatment.

An enzootic focus of vesicular stomatitis virus New Jersey serotype (VSV-NJ) exists on Ossabaw Island, Georgia. Many questions regarding the epizootiology of this virus at this focus still exist, but evidence suggests that the vector for this virus is a phlebotomine sand fly (Lutzomyia shannoni), with feral swine serving as a potential source of virus for the sand fly and for other swine via contact transmission. We conducted 2 experimental trials in domestic swine using VSV-NJ isolated from a sand fly from Ossabaw Island to determine if route of inoculation or immunosuppression via steroid administration affected the development of disease, viremia, viral shedding, or the neutralizing antibody response. In a third trial, we studied the potential for contact transmission among swine using this isolate. Virus isolations were made from nasal cavity or palatine tonsil of the soft palate, and VSV-NJ neutralizing antibodies developed when pigs were inoculated intradermally in the apex of the snout, ear, or coronary band, intravenously, intranasally, or via scarification of the apex of the snout or coronary band. Vesicles developed only in pigs inoculated in the apex of the snout or coronary band, and these vesicles were at the site of inoculation. Steroid treatment did not potentiate the development of secondary vesicles and did not prolong the period of virus shedding from VSV-NJ-infected swine. Contact transmission, as determined by shedding of virus from the tonsil of the soft palate and the development of VSV-NJ neutralizing antibodies, occurred in pigs in contact with animals inoculated in the apex of the snout but not in contact animals exposed to pigs inoculated intradermally in the coronary band or intranasally. These trials show that contact transmission can occur and VSV-NJ can be shed without the development of clinical disease (i.e., vesicle formation). Viremia was never detected in any of the experimental pigs, suggesting that swine may not be a good amplifying host for VSV-NJ.

Incompetence of domestic pigs as amplifying hosts of vesicular stomatitis virus for Lutzomyia shannoni (Diptera: Psychodidae).

Seven domestic pigs, Sus scrofa L., were infected by intradermal inoculation at 3 different sites with the New Jersey serotype of vesicular stomatitis (VSNJ) virus. Laboratory-reared Lutzomyia shannoni Dyar sand flies, a suspected biological vector of VSNJ virus, were allowed to feed on pigs at the lower abdomen or at sites of their own selection on days 1-7 and on day 10 postinfection. Blood samples were taken from infected swine concomitant with most feeding trials and tested for the presence of virus. Sand flies were held for up to 5 d following ingestion of blood and tested for VSNJ virus infection. Virus was not recovered from the blood of infected pigs or from any of the flies that fed on these pigs. The findings suggest that domestic pigs do not fulfill the traditional concept of amplifying hosts of VSNJ virus.

Experimental infection of Borrelia burgdorferi in white-tailed deer.

Four white-tailed deer (Odocoileus virginianus) were experimentally inoculated with Borrelia burgdorferi to determine serologic response by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. Deer had antibodies by ELISA by 2 to 3 wk post-inoculation (PI) and remained positive for 10 wk. Deer demonstrated immunoblotting reactivity between 10 and 14 days PI and consistently showed antibody response to nine B. burgdorferi antigens. Attempts were made to recover the spirochete from blood and tissues; B. burgdorferi was isolated from an ear punch biopsy from one of the inoculated deer.

Feral swine as a potential amplifying host for vesicular stomatitis virus New Jersey serotype on Ossabaw Island, Georgia.

Sentinel feral swine (Sus scrofa) on Ossabaw Island, Georgia (USA), were serologically monitored for antibodies to vesicular stomatitis New Jersey serotype (VSNJ) virus from 17 April to 27 August 1990. Seroconversions to VSNJ virus were detected in 24% of swine island-wide. Differences in the incidence of seroconversion were detected between swine sampled in the Pleistocene and Holocene formations of the island suggesting that the presence of virus is forest type dependent. Based on the consistency in onset and spatial distribution of seroconversions with data from 1981 to 1985, this is a very stable host-parasite system. Sequential virus isolation attempts from nasal swabs, tonsil swabs, and blood were made on a subsample of 54 sentinel swine from 9 May to 4 July 1990. The VSNJ virus was isolated from five swine from 16 May to 20 June. Vesicular lesions were detected on only two of these animals. Although infections in these feral swine were short-lived (< 7 days) and were followed by a strong neutralizing antibody response, VSNJ virus was detected in a single group of swine for a period exceeding 1 month. From these data, it appears that feral swine could provide a source of virus to feeding arthropods for extended periods of time. The failure to detect a viremia in these animals, however, indicates that a source other than blood may be required for transmission to occur.

Antibodies to vesicular stomatitis New Jersey type virus in white-tailed deer on Ossabaw Island, Georgia, 1985 to 1989.

From 1985 to 1989, 491 serum samples were collected from white-tailed deer (Odocoileus virginianus) on Ossabaw Island, Georgia (USA) and were tested for neutralizing antibodies to New Jersey and Indiana type vesicular stomatitis viruses. Prevalence of antibodies to vesicular stomatitis New Jersey (VSNJ) virus in deer for the 5-yr period was 43%. Prevalence of antibodies differed by year (P less than 0.0001), and was dependent on age class (P less than 0.0001) and location on the island (P less than 0.0001). Of 173 deer sampled from other locations in the southeastern United States, only two had VSNJ antibody titers normally considered positive (greater than or equal to 1: 32). The positive deer were from Union County, Arkansas (USA) and Wakulla County, Florida (USA). No evidence of exposure to vesicular stomatitis Indiana Virus was observed.

Antibodies to vesicular stomatitis New Jersey type virus in wild and domestic sentinel swine.

Wild sentinel swine on Ossabaw Island, Chatham County, Georgia, were serially bled and tested for vesicular stomatitis New Jersey type virus neutralizing antibody to determine the intensity, distribution, and progression of annual viral activity. From March through September, 1984 and 1985, 112 and 226 juvenile (less than 8 months) swine, respectively, were sampled. Seroconversions initially were detected on May 7, 1984 and May 18, 1985. Incidence of seroconversion in wild swine reached 32% during 1984 and 26% during 1985. Viral activity as determined by seroconversion results occurred earliest and was greatest on the southern half of Ossabaw Island. Domestic swine were housed in four pens under controlled conditions to document arthropod transmission of vesicular stomatitis virus. Twelve swine, three in each pen, were serially bled from April through September of both years. Seroconversion occurred during May 16-23, 1984 and May 15-22, 1985. Results varied among pen locations but were consistent between years. Clinical disease was not seen in any wild or domestic swine during either year.

Enzootic vesicular stomatitis New Jersey type in an insular feral swine population.

Free-ranging feral swine from Ossabaw Island, Chatham County, Georgia, were serially bled and tested for vesicular stomatitis New Jersey type serum neutralizing antibody to determine the intensity and progression of annual vesicular stomatitis activity. From November 21, 1981 to October 11, 1982, and from March 15, 1983 to October 14, 1983, 307 and 340 swine were sampled, respectively. Seroconversions were initially detected during the first week of June and continued into September in both 1982 and 1983. Serologic results indicate a seroconversion incidence during 1982 and 1983 of approximately 12% and 60%, respectively. Similar patterns in timing and affected geographic area were observed during both years, with the earliest viral activity and highest incidence restricted to the southern portion of the island. Clinical vesicular stomatitis was not seen during 1982. However, during 1983, vesicular stomatitis New Jersey type virus was isolated from vesicular lesions on two swine.