Experimental induction of chronic borreliosis in adult dogs exposed to Borrelia burgdorferi-infected ticks and treated with dexamethasone.

OBJECTIVE: To develop a method to experimentally induce Borrelia burgdorferi infection in young adult dogs. ANIMALS: 22 healthy Beagles. PROCEDURE: All dogs were verified to be free of borreliosis. Twenty 6-month-old dogs were exposed to Borrelia burgdorferi-infected adult ticks and treated with dexamethasone for 5 consecutive days. Two dogs not exposed to ticks were treated with dexamethasone and served as negative-control dogs. Clinical signs, results of microbial culture and polymerase chain reaction (PCR) testing, immunologic responses, and gross and histologic lesions were evaluated 9 months after tick exposure. RESULTS: Predominant clinical signs were episodic pyrexia and lameness in 12 of 20 dogs. Infection with B burgdorferi was detected in microbial cultures of skin biopsy specimens and various tissues obtained during necropsy in 19 of 20 dogs and in all 20 dogs by use of a PCR assay. All 20 exposed dogs seroconverted and developed chronic nonsuppurative arthritis. Three dogs also developed mild focal meningitis, 1 dog developed mild focal encephalitis, and 18 dogs developed perineuritis or rare neuritis. Control dogs were seronegative, had negative results for microbial culture and PCR testing, and did not develop lesions. CONCLUSIONS AND CLINICAL RELEVANCE: Use of this technique successfully induced borreliosis in young dogs. Dogs with experimentally induced borreliosis may be useful in evaluating vaccines, chemotherapeutic agents, and the pathogenesis of borreliosis-induced arthritis.

Field study of the safety, immunogenicity, and efficacy of an inactivated equine rotavirus vaccine.

OBJECTIVE: To determine safety, immunogenicity, and efficacy of an inactivated equine rotavirus vaccine. DESIGN: Prospective randomized controlled trial. ANIMALS: 316 pregnant Thoroughbred mares during the first year of the study and 311 during the second year. PROCEDURE: During the first year, mares received 3 doses of vaccine or placebo, IM, at 8, 9, and 10 months of gestation. Serum neutralizing antibody titers were measured before vaccination and 1 and 35 days after foaling. Antibody titers were measured in foals 1, 7, 35, 60, 90, and 120 days after birth. During the second year, mares that had been vaccinated the previous year received a single booster dose of vaccine approximately 1 month prior to parturition. Mares that had received the placebo the previous year and mares new to the study received 3 doses of vaccine or placebo. Serum neutralizing antibody titers were measured in samples taken from mares approximately 1 day after foaling and from foals approximately 1 and 60 days after birth. RESULTS: Adverse reactions were not observed. Antibody titers were significantly increased at the time of foaling and 35 days after foaling in vaccinated, compared with control, mares and for 90 days after birth in foals born to vaccinated, compared with foals born to control, mares. Incidence of rotaviral diarrhea was lower in foals born to vaccinated, compared with foals born to control, mares, but the difference was not significant. CLINICAL IMPLICATIONS: Results suggest that the equine rotavirus vaccine is safe and immunogenic and that reasonable efficacy under field conditions can be expected.

Protection of cats from infectious peritonitis by vaccination with a recombinant raccoon poxvirus expressing the nucleocapsid gene of feline infectious peritonitis virus.

Feline Infectious Peritonitis Virus (FIPV) is a coronavirus that induces an often fatal, systemic infection in cats. Various vaccines designed to prevent FIPV infection have been shown to exacerbate the disease, probably due to immune enhancement mediated by virus-specific immunoglobulins against the outer envelope (S) protein. An effective vaccine would be one that induces cell-mediated immunity without disease enhancing antibodies. In this report, we describe the use of a recombinant raccoon poxvirus that expresses the gene encoding the nucleocapsid protein of FIPV (rRCNV-FIPV N) as an effective vaccine against FIPV-induced disease. Cats were parenterally or orally vaccinated twice, three weeks apart. Cats were then orally challenged with Feline Enteric Coronavirus (FECV), which induces a subclinical infection that can cause enhancement of subsequent FIPV infection. Three weeks later, cats were orally challenged with FIPV. The FIPV challenge induced a fatal infection in 4/5 (80%) of the controls. On the other hand, all five cats vaccinated subcutaneously with rRCNV-FIPV N showed no signs of disease after challenge with FIPV. Four of the five subcutaneous vaccinates survived an additional FIPV challenge. Vaccination with rRCNV-FIPV N induced serum IgG antibody responses to FIPV nucleocapsid protein, but few, if any, FIPV neutralizing antibodies. In contrast to the controls, protected vaccinates maintained low FIPV serum neutralizing antibody titers after FIPV challenge. This suggests that the protective immune response involves a mechanism other than humoral immunity consisting of FIPV neutralizing antibodies.

Clinical evaluation of the efficacy of inoculating cattle with a vaccine containing Tritrichomonas foetus.

To test the efficacy of a polyvalent Tritrichomonas foetus vaccine, 130 nulliparous heifers were randomly assigned to either receive the test T foetus vaccine or to serve as nonvaccinated controls. The polyvalent test vaccine consisted of a Campylobacter fetus/Leptospira canicola-grippotyphosa-hardjo-icterohaemorrhagiae-pamona bacterine containing 5 x 10(7) killed T foetus/dose. The polyvalent control vaccine consisted of the aforementioned formulation without T foetus. Heifers were administered 2 doses of control or experimental vaccine at 3-week intervals. Heifers were bred to T foetus-infected bulls and their conception and pregnancy rates were determined throughout gestation. In addition, serum samples were analyzed to determine induced concentrations of antitrichomonal antibodies and vaginal secretions were sampled to determine T foetus infection rates in control and vaccinated animals. One week after each of the 15-day breeding periods, 60% (6 of 10) of tested vaccinates and 80% (8 of 10) of tested control animals were T foetus culture-positive. The mean duration of infection of vaccinates was 3.8 weeks (+/- 7.5 days), compared with 5.4 weeks (+/- 7.5 days) of infection for control heifers. All vaccinates developed increased immunofluorescence and serum neutralizing antibody titers following the first immunization, and had additional increases of at least fourfold in response to the second injection. In contrast, no consistent increase in immunofluorescence or serum neutralizing antibodies was observed in control animals. Conception rates were 89.2% for vaccinates and 85.9% for control animals 30 days after breeding and 80 to 90% of these remained pregnant 60 days after breeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Examination of Koch's postulates for Borrelia burgdorferi as the causative agent of limb/joint dysfunction in dogs with borreliosis.

Borrelia burgdorferi has been implicated as the causative agent of borreliosis in dogs, which is characteristically a limb/joint disorder, but can be associated with multiple-organ dysfunction. Attempts to reproduce this disease by inoculating dogs with B burgdorferi have not been successful. In the study of this report, B burgdorferi from Ixodes dammini ticks was used to induce signs of limb/joint dysfunction, fever, anorexia, depression, and systemic infection in dogs. A pure culture of this bacterium from the blood of an infected dog has been used to fulfill Koch's postulates for B burgdorferi as the causative agent of limb/joint dysfunction associated with borreliosis in dogs.

Immunogenicity and efficacy study of a commercial Borrelia burgdorferi bacterin.

The immunogenicity and efficacy of a commercial Borrelia burgdorferi bacterin was evaluated for stimulation of the host immune response and protection against clinical disease associated with experimentally induced borreliosis in dogs. A total of 30 vaccinated and 24 control dogs were used in 3 separate studies. The vaccine was given IM as two 1-ml doses separated by a 3-week interval. Two weeks or 5 months following the last vaccination, the dogs were challenge inoculated with 7 daily doses of a virulent preparation of a B burgdorferi field isolate through intraperitoneal, subcutaneous, and intradermal routes with or without glucocorticoid administration at the same time. The development of B burgdorferi spirochetemia and clinical disease in the dogs after challenge exposure was studied. Serum samples were obtained from the dogs at various times during the study for serum neutralizing antibody determination and protein immunoblot antibody assay against various geographic isolates of B burgdorferi. Challenge exposure induced limb/joint disorder, fever, anorexia, signs of depression, and B burgdorferi spirochetemia in the nonvaccinated control dogs. The vaccine was found to elicit cross-reactive serum neutralizing and protein immunoblot antibody responses in dogs to various isolates of B burgdorferi and to protect the vaccinated dogs against experimentally induced borreliosis.

Comparison of the efficacy of three commercial feline leukemia virus vaccines in a natural challenge exposure.

Forty-seven kittens were exposed for 31 weeks to 12 FeLV-positive carrier cats. The carrier cats were infected with 2 laboratory strains of FeLV and at least 2 strains of street virus. Eleven nonvaccinated control kittens and 12 vaccinated kittens were allotted to 3 groups. After 31 weeks of exposure, the following kittens were persistently blood FeLV positive by ELISA and immunofluorescence antibody (IFA) testing: 7 of the 11 control kittens, 0 of 12 kittens inoculated with vaccine A, 5 of 12 kittens inoculated with vaccine B, and 6 of 12 kittens inoculated with vaccine C. Only the kittens inoculated with vaccine A were significantly (P less than 0.05) different from the control group. After 23 weeks of exposure, culture was done to identify FeLV in the bone marrow of the kittens. Feline leukemia virus was isolated from the bone marrow of 9 of 11 control kittens. Virus was isolated from the bone marrow of 5 of 12 kittens inoculated with vaccine A, 11 of 12 kittens inoculated with vaccine B, and 10 of 12 kittens inoculated with vaccine C. Of the 17 cats that had FeLV isolated only from culture of bone marrow (negative results of blood virus isolation, ELISA, and IFA testing), 13 eliminated the virus from the bone marrow by week 31 of exposure. After 31 weeks of exposure, FeLV was isolated from the bone marrow of 8 of 11 control kittens, 0 of 12 kittens inoculated with vaccine A, 7 of 12 kittens inoculated with vaccine B, and 7 of 12 kittens inoculated with vaccine C.

Antibody response of kittens after vaccination followed by exposure to feline leukemia virus-infected cats.

Protein (western) blot analysis and virus-neutralization assay were used to evaluate the antibody response of specific-pathogen-free kittens to FeLV vaccination and followed by natural exposure. Several kittens had barely detectable reactions to specific FeLV antigens prior to vaccination or exposure. Correlation was not found between protection against persistent viremia and antibody response after vaccination as measured by western blot analysis or virus neutralization assay. A statistically significant (P less than 0.01) difference in the antibody response against p27 antigen after natural exposure to FeLV was observed between persistently viremic kittens and transiently viremic or aviremic kittens. Measurable (P less than 0.05) virus neutralizing antibody titer after FeLV exposure was found only in a small number of kittens that were protected against persistent viremia. Lack of association between humoral response and vaccination-induced protection against persistent FeLV infection suggests an important role for cell-mediated immunity in such protection.