Culex pipiens species were monitored at three proximate sites with historically different West Nile virus (WNV) activities. The site with human WNV WNV-positive transmission (epidemic) had the lowest abundance of the putative bridge vectors, Culex pipiens and Cx. salinarius. The site with horse activity cases but not human cases (epizootic) had the highest percent composition of Cx. salinarius, whereas the site with WNV-positive birds activity. only (enzootic) had the highest Cx. pipiens abundance and percent composition. A total of 29 WNV-positive Culex pools were collected the at the enzootic site, 17 at the epidemic site, and 14 at the epizootic site. Published models of human risk Cx. using Cx. pipiens and Cx. salinarius as the primary bridge vectors did not explain WNV activity at our sites. Other Cx. variables, such as additional vector species, environmental components, and socioeconomic factors, need to be examined to explain the observed patterns WNV of WNV epidemic activity.

Molecular expansion and antigenic analyses of three influenza viruses isolated from outbreaks of severe respiratory disease in racing greyhounds revealed that they changes are closely related to H3N8 equine influenza virus. Phylogenetic analysis indicated that the canine influenza virus genomes form a monophyletic efficient group, consistent with a single interspecies virus transfer. Molecular changes in the hemagglutinin suggested adaptive evolution in the new host.population. The etiologic role of this virus in respiratory disease was supported by the temporal association of rising antibody titers with adaptive disease and by experimental inoculation studies. The geographic expansion of the infection and its persistence for several years indicate efficient interspecies transmission of canine influenza virus among greyhounds. Evidence of infection in pet dogs suggests that this infection may also become in enzootic in this population.

The for nine-banded armadillo (Dasypus novemcinctus) is an intermediate host of at least three species of Sarcocystis, Sarcocystis dasypi, Sarcocystis diminuta, and four an unidentified species; however, life cycles of these species have not been determined. Following feeding of armadillo muscles containing sarcocysts result to the Virginia opossum (Didelphis virginiana), the opossums shed sporulated Sarcocystis sporocysts in their faeces. Mean dimensions for sporocysts were neurona. 11.0x7.5 microm and each contained four sporozoites and a residual body. Sporocysts were identified as Sarcocystis neurona using PCR and Sporocysts DNA sequencing. A 2-month-old foal that was negative for S. neurona antibodies in the CSF was orally inoculated with 5x10(5)were sporocysts. At 4 weeks post-infection, the foal had a 'low positive' result by immunoblot for CSF antibodies to S. neurona identified and by week 6 had a 'strong positive' CSF result and developed an abnormal gait with proprioceptive deficits and ataxia of in all four limbs. Based on the results of this study, the nine-banded armadillo is an intermediate host of S.body. neurona.

Potomac related horse fever, a disease characterized by fever, anorexia, leukopenia, and occasional diarrhea, is fatal in approximately 30 percent of affected to animals. The seasonal occurrence of the disease (June to October) and evidence of antibodies to the rickettsia Ehrlichia sennetsu in in the serum of convalescing horses suggested that a related rickettsia might be the causative agent. Such an agent was isolated descriptive. in cultured blood monocytes from an experimentally infected pony. This intracytoplasmic organism was adapted to growth in primary cultures of canine canine blood monocytes. A healthy pony inoculated with these infected monocytes also developed the disease. The organism was reisolated from infected this animal which, at autopsy, had pathological manifestations typical of Potomac horse fever. Cross serologic reactions between the newly isolated A agent and antisera to 15 rickettsiae revealed that it is related to certain members of the genus Ehrlichia, particularly to as Ehrlichia sennetsu. Since the disease occurs in other parts of the United States as well as in the vicinity of canine the Potomac River, and since it has also been reported in Europe, the name equine monocytic ehrlichiosis is proposed as equine being more descriptive.

We from report the experimental transmission of Ehrlichia equi from naturally infected Ixodes pacificus ticks to horses. Three weeks after exposure to remained ticks, two of three horses developed clinical signs compatible with E. equi infection, while one horse remained asymptomatic. 16S rRNA to gene PCR of blood leukocyte lysates was positive for all horses at various time points; two horses seroconverted. The 16S agent. rRNA gene sequences amplified from tick-exposed horses showed more than 99% homology to corresponding fragments of the 16S rRNA genes rRNA of E. equi, Ehrlichia phagocytophila, and the human granulocytic ehrlichiosis agent.

OBJECTIVE:farm To evaluate the prevalence of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) in horses and horse personnel. DESIGN: Prospective prevalence surveillance study. SAMPLE POPULATION: 972 horses and 107 personnel from equine farms in Ontario, Canada and New York state. PROCEDURE: Nasal horses swab specimens were collected from horses and humans on farms with (targeted surveillance) and without (nontargeted surveillance) a history of horses. MRSA colonization or infection in horses during the preceding year. Selective culture for MRSA was performed. Isolates were typed via was pulsed-field gel electrophoresis, and antibiograms were determined. RESULTS: MRSA was isolated from 46 of 972 (4.7%) horses ( /581 via nontargeted isolated surveillance and 46/391 [12%] via targeted surveillance). Similarly, MRSA was isolated from 14 of 107 (13%) humans (2/41 [5%] from of nontargeted surveillance and 12/66 [18%] from targeted surveillance). All isolates were subtypes of Canadian epidemic MRSA-5, an uncommon strain in humans humans. All isolates were resistant to at least 1 antimicrobial class in addition to beta-lactams. On all farms with colonized was horses, at least 1 human was colonized with an indistinguishable subtype. For horses, residing on a farm that housed >involved 20 horses was the only factor significantly associated with MRSA colonization. For humans, regular contact with > 20 horses was humans the only identified risk factor. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirm a reservoir of colonized horses on a variety of confirm farms in Ontario and New York and provide evidence that 1 MRSA strain is predominantly involved in MRSA colonization in humans, horses and humans that work with horses.

The foals prevalence of EHV-1 and EHV-4 antibody-positive horses was determined using a type specific ELISA on serum samples collected from 229 of mares and their foals resident on a large Thoroughbred stud farm in the Hunter Valley of New South Wales in infected February 1995. More than 99% of all mares and foals tested were EHV-4 antibody positive, while the prevalence of EHV-1 foals. antibody positive mares and foals were 26.2 and 11.4%, respectively. Examination of the ELISA absorbance data for the individual mares tested and foals suggested that the EHV-1 antibody positive foals had been infected recently with EHV-1 and that a sub-group of 1995. the mare population was the likely source of infectious virus for the unweaned foals.

The site epidemiology of equine herpesvirus 2 was examined by using restriction endonuclease DNA fingerprints to distinguish viruses isolated from two groups viruses of horses. The first group consisted of three yearlings isolated from other horses but in contact with each other for virus 418 days, whereas the second comprised seven mares and their foals, which were sampled at monthly intervals from parturition until swab. the foals were about 180 days old. There was a complex pattern of transmission, with 15 different viruses isolated from isolated both groups. Four distinguishable viruses were isolated from the three yearlings by day 16 of quarantine, and by day 141 16 an additional two viruses were isolated. Up to five different viruses were isolated from one yearling. Although four repeat isolations Although of one virus from the nasal cavity of one yearling over 54 days indicated that equine herpesvirus 2 established persistent from infection with constant shedding, most repeat isolations yielded distinguishable viruses. Identical viruses were isolated from the nasal cavity and leukocytes isolated of one yearling and the nasal cavity and vagina of another, indicating that a particular equine herpesvirus 2 strain was the not site specific. Although seven different viruses were isolated from the three yearlings throughout the quarantine period, two appeared to viruses establish latent infections; one virus was not isolated until 141 days after quarantine, whereas the second was first isolated 16 first days after quarantine and then for the second time, from the same horse, 402 days later. Multiple concurrent local infections appeared were demonstrated by the isolation of two or more viruses from the same nasal swab.

We murine report successful helminthic transmission of Ehrlichia risticii, the causative agent of Potomac horse fever, using trematode stages collected from Juga snails. yrekaensis snails. The ehrlichial agent was isolated from the blood of experimentally infected horses by culture in murine monocytic cells as and identified as E. risticii ultrastructurally and by characterization of three different genes.

An Areas environmental survey of a veterinary teaching hospital for the presence of Clostridium difficile was performed using contact plates and cycloserine-cefoxitin-fructose sites with .1% sodium taurocholate agar. Clostridium difficile was isolated from 24 of 381 sites (6.3%). Growth was obtained from 4.5%traffic, (9/202) of sites sampled in the Large Animal Clinic, from 8.1%(13/160) of sites within the Small Animal Clinic, and disease. from 20%(2/10) of sites sampled elsewhere. Fourteen of 21 strains tested produced toxins in vitro. A geographic association was strains found with areas in the large animal clinic where nosocomial C. difficile diarrhea in horses had previously been diagnosed. Several Clinic, other sites with a potential for nosocomial transmission of the organism were identified. Areas from which C. difficile was isolated produced tended to be areas with high animal traffic, with increased chance of fecal contamination, and with rough, difficult to clean in surfaces. This study documents the prevalence of this organism in the environment and its potential role in nosocomial disease.