One hundred and fifty lactating Holstein cows from 2 genetic lines selected for high and average milk production were used in the study. Sera from 6 annual herd tests were analyzed by agar-gel immunodiffusion test for antibodies to bovine leukemia virus. Odds of being seropositive were analyzed by use of stepwise and backward logistic regression procedures. Analysis within birth year revealed that estimated ln odds increased by 0.19/year of age among cows of the high genetic line and by 0.43 among cows of the average genetic line. This was accompanied by a more important cohort effect among high producers than among average producers.

Two commercially available infectious bovine keratoconjunctivitis (IBK) vaccines were evaluated for their effectiveness in protecting cattle from disease caused by experimental challenge exposure and natural transmission of Moraxella bovis infections. The study was conducted as 2 experiments, using a total of 81 cattle that were culture-negative for M bovis prior to vaccination. In each experiment, young adult cattle were randomly allotted to 4 groups. Each calf in groups 1 and 2 was vaccinated according to the vaccine manufacturer's directions. Groups 3 and 4 were unvaccinated controls. Three weeks after the last vaccination, each calf in groups 1 and 3 was experimentally challenge exposed by dropping a suspension of viable cells of a virulent strain of M bovis directly onto the corneal surface of each eye. Calves in all 4 groups were then commingled in open pastures so that calves in groups 2 and 4 could be naturally exposed to the calves with experimentally induced infections. Each calf was examined for signs of ocular disease on a regular basis by 2 experienced clinicians who scored each eye for severity of disease on the basis of a prearranged scale. Neither clinician was aware of the vaccination or exposure status of the calf nor to which experimental group they belonged. Lacrimal secretions were collected regularly to determine the number of eyes in which the virulent organism became established. Moraxella bovis with bacterial cultural characteristics similar to those of the virulent strain placed in the eyes of groups 1 and 3 was cultured from > 83% of the eyes of calves in all groups. The incidence of clinical IBK was > 50% in each group. There was no significant difference in the ability of vaccinated calves to resist experimental or natural challenge infection. Compared with that in nonvaccinated controls, no decreased incidence or severity of clinical IBK was noticed in vaccinated calves. Though the challenge strain used was not homologous to those used to prepare the vaccine, it was no different than those that may be expected to cause disease under field conditions.

A successful attempt was made to mechanically transmit bovine leukosis virus (BLV) from a BLV-infected cow with a normal lymphocyte count to sheep by inoculation with horse fly (Tabanus abactor) mouthparts. After interrupted natural feeding, horse flies were anesthetized with CO2. Mouthparts were severed and pooled into a tissue grinder containing medium. Five inocula containing the mouthparts of 10 flies each, and 5 inocula containing the mouthparts of 20 flies each, were prepared and inoculated SC in the right axilla of 10 BLV antibody-negative sheep. Five additional sheep served as controls. Serum samples were collected at 2-week intervals and tested by agar gel immunodiffusion for BLV antibodies. One sheep injected with 20 mouthparts developed antibodies to BLV at 10 weeks after inoculation. Six months after inoculation with fly mouthparts, 1 BLV antibody-negative sheep was randomly selected from each treatment group and injected, in the left axilla, with 3 ml of blood from the donor cow to confirm susceptibility of the sheep. All 3 sheep developed antibodies to BLV within 4 weeks.

Transstadial and transovarial transmission of Anaplasma marginale by Dermacentor variabilis were attempted with ticks exposed to the organism once by feeding as larvae or nymphs, and twice by feeding as larvae and nymphs. Typical colonies of A marginale were in gut tissues of adults that were infected as larvae, larvae and nymphs, and as nymphs; repeated exposure of ticks did not appear to result in an increase in the number of colonies in the gut of subsequently molted adults nor did it affect severity of the clinical disease that developed in cattle they fed on. In contrast, colonies of A marginale were not found in the midgut epithelium of unfed nymphs exposed as larvae, even though companion nymphs transmitted the parasite, causing severe clinical anaplasmosis in susceptible calves. The organism was not transmitted transovarially by F1 larvae or nymphs from the groups exposed as parent larvae, nymphs, larvae and nymphs, and as adults. Some of the calves fed on by F1 progeny had a few erythrocytic marginale bodies that looked suspiciously like A marginale, as well as postchallenge exposure prepatent periods that were longer than other calves in the transovarial transmission study. Sera from these calves were tested for antibody to A marginale, using a highly sensitive immunoblot technique. Antibodies were not detected in any of the sera.

Six Rocky Mountain bighorn sheep were raised in captivity from birth (n = 5) or taken from the wild as a lamb (n = 1). After the bighorn sheep were in captivity for over a year, 6 clinically normal domestic sheep were placed on the 2 ha of pasture on which the bighorn sheep were kept. Nasal swab specimens were obtained from all sheep at the time the domestic sheep were introduced. Pasteurella haemolytica was isolated from swab specimens obtained from 4 of 6 domestic sheep, but not from specimens obtained from the bighorn sheep. All 6 bighorn sheep died of acute hemorrhagic pneumonia after exposure to domestic sheep. Death in the bighorn sheep occurred on days 4, 27, 27, 29, 36, or 71 after initial exposure to domestic sheep. Pasteurella haemolytica was isolated from respiratory tract tissue specimens of all bighorn sheep at the time of death. None of the domestic sheep were clinically ill during the study. At the end of the study, 3 of 6 domestic sheep were euthanatized, and at necropsy, P haemolytica was isolated from 2 of them. The most common serotypes in bighorn and domestic sheep were P haemolytica T-3 and A-2. Other serotypes isolated included P haemolytica A-1, A-9, and A-11 in bighorn sheep and A-1 in domestic sheep. On the basis of results of this study and of other reports, domestic sheep and bighorn sheep should not be managed in proximity to each other because of the potential fatal consequences in bighorn sheep.

Experiments concerned with the immunogenicity, pathogenicity, and transmissibility of a recombinant vaccinia:Sindbis virus were conducted. The WR strain of the recombinant vaccinia:Sindbis virus was found to be infective for calves and mildly pathogenic, resulting in local tissue reaction. It was not transmissible to other calves. Also, it was found to be immunogenic when inoculated intradermally into calves, and antibody was produced against the parent vector virus (vaccinia) and the Sindbis antigen. Recombinant virus given IV to calves induced no detectable clinical signs, nor did the calves develop neutralizing antibodies. Furthermore, second-passage lesion material containing up to 10(7) tissue culture infective doses of the recombinant virus failed to induce development of lesions or illness in intradermally inoculated calves, and virus could not be recovered from the inoculation sites. In this series of experiments, this vaccinia recombinant given intradermally was immunogenic, mildly pathogenic at the local injection site only, and was not transmissible to contact animals, thus demonstrating the potential efficacy and safety of the WR strain of vaccinia virus when used as a live vector system in cattle.

Sarcoptes scabiei var. suis, ivermectin, single treatment of infected sows before farrowing eliminated scabies from sows and prevented its transmission to their offspring, offspring remained uninfected throughout study regardless of whether they were treated with ivermectin at weaning, infection (epizootic) in growing pigs could be controlled by single treatment of all in-contact pigs but routine treatment of all pigs at weaning does not seem justified

Leishmania donovani, amastigotes from dog marrow macrophages, ultrastructure

rcine reproductive and respiratory syndrome, caused by the porcine reproductive and respiratory syndrome virus (PRRSV), is an economically important disease in the swine industry. Previous studies demonstrated the presence of the virus in pig meat and its transmissibility by oral consumption. This study further analyzed the infectivity of PRRSV in commercial pig meat. Fresh bottom meat pieces (n = 1500) randomly selected over a period of 2 y from a pork ham boning plant located in Quebec, Canada, were tested by reverse transcriptase polymerase chain reaction (RT-PCR). Each trimmed meat was stored in the plant freezer, subsampled weekly for up to 15 wk, and tested with quantitative RT-PCR to determine the viral load. Meat infectivity was evaluated using specific pathogen-free piglets, each fed with approximately 500 g of meat at the end of the storage time. Genotype-specific RT-PCR confirmed the presence of PRRSV mainly during cold weather in 0.73% of the fresh meat pieces. Wild and vaccine strains of genotype 2 were detected. Porcine reproductive and respiratory syndrome virus nucleic acid was stable in meat stored at around -20°C during the 15 wk. Serological and molecular analysis showed the transmission of infection by a majority of PRRSV positive meat pieces (5/9) fed orally to naïve recipients. The results confirmed a low prevalence of PRRSV in market's pig meat, and virus transmissibility by oral consumption to naïve recipients even after several weeks of storage in a commercial freezer. It occurred mainly with meat harboring the highest PRRSV RNA copies, in the range of 109 copies per 500 g of meat, with both wild type and vaccine-related strains.

OBJECTIVE To investigate the presence of parapoxvirus (PPV) in cattle without clinical signs of infection and in farm environments of PPV-infected cattle. ANIMALS 28 calves without clinical signs of PPV infection on 2 farms and 11 clinically affected calves on 6 farms. PROCEDURES 164 oral swab samples were collected at regular intervals from 28 calves without clinical signs of PPV infection, and 11 swab samples were collected from 11 clinically affected calves. Viral DNA load was quantified by use of a PPV-specific quantitative real-time PCR (qRT-PCR) assay. RESULTS Of 28 calves without clinical signs of PPV infection, 12 had positive results for PPV DNA by use of the qRT-PCR assay. Viral DNA was detected continuously over a period of 2 to 5 months from 9 of these 12 calves, particularly from calves with dermatomycosis or respiratory tract disease. The PPV DNA loads in 32 oral swab samples from these 12 calves were significantly lower (median, 3.2 copies/mg) than those in samples collected from the 11 clinically affected calves (median, 3.2 × 10(4) copies/mg). Moreover, PPV DNA was detected in the residual feed and drinking water on both farms that housed the calves without clinical signs of PPV infection. CONCLUSIONS AND CLINICAL RELEVANCE PPV in cattle without clinical signs of infection and in the environments of these cattle may represent sources of PPV transmission to susceptible cattle. IMPACT FOR HUMAN MEDICINE Humans should wear gloves to prevent zoonotic disease transmission when handling cattle with or without clinical signs of PPV infection.