Evaluation of dietary and environmental risk factors for hyperthyroidism in cats.

OBJECTIVE: To identify dietary and environmental risk factors for hyperthyroidism in cats. DESIGN: Case-control study. ANIMALS: 100 cats with hyperthyroidism and 163 control cats. PROCEDURE: Medical records were examined, and owners completed a mailed questionnaire. Data collected included information regarding demographic variables, environmental exposures, and diet, including preferred flavors of canned cat food. RESULTS: Case cats were significantly less likely to have been born recently than control cats. Housing; exposure to fertilizers, herbicides, or plant pesticides; regular use of flea products; and presence of a smoker in the home were not significantly associated with an increased risk of disease, but cats that preferred fish or liver and giblets flavors of canned cat food had an increased risk. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cats that prefer to eat certain flavors of canned cat food may have a significantly increased risk of hyperthyroidism.

Respiratory diseases of rabbits.

Respiratory diseases are second only to gastroenteric diseases in importance in rabbits. Pasteurellosis is the primary respiratory disease affecting domestic rabbits, but other bacteria (e.g., Bordetella broniseptica and Staphylococcus spp) are significant opportunistic pathogens. The primary manifestations are upper respiratory disease (e.g., rhinitis, sinusitis, conjunctivitis, and dacryocystitis). Various antimicrobials are effective for treatment.

Natural transmission of bovine leukemia virus in dairy and beef cattle.

Many potential routes of bovine leukemia virus (BLV) transmission are reviewed in this article. Vertical transmission, in utero, or through colostrum and milk, accounts for a relatively small proportion of infections. Iatrogenic horizontal transmission, through procedures permitting the transfer of blood between cattle, has been shown to be a major route of transmission in most settings. Contact transmission stems from a mixture of natural sources of blood, exudates, and tissues that enter the body through mucosal surfaces or broken skin. Careful analysis of management procedures and environmental conditions present in individual dairy and beef herds affords the greatest opportunity to develop effective BLV prevention programs.

Food animal and poultry retroviruses and human health.

In summary, studies reported to date have largely failed to demonstrate human infection with animal and poultry retroviruses or an association between human diseases and these viruses. A number of studies, most of them serologic, have attempted to demonstrate human infection with these viruses. The lack of antibodies in apparently exposed groups of persons suggests an absence of infection. However, another possible explanation is that humans may be immunologically unresponsive to infection with these viruses. Although attempts to infect normal human cells in vitro with many of these viruses have not been reported, BLV and BIV appear to grow poorly or not at all. On the other hand, ALSV subgroup D infect and transform human cells in vitro. However, the production of infectious virus in vitro has been low or nonexistent. This may explain the absence of antibodies in human populations. Furthermore, many of the methods used to detect infection, either directly or indirectly, have either low sensitivity or problems with specificity. Several epidemiologic studies have tried to show a relationship between human and animal leukemia or lymphoma. In many of these studies the actual exposure to retroviruses is unknown and exposure to animals may merely represent exposure to other risk factors that are more important but were either not considered or are undefined; alternatively, a common exposure may be responsible for malignancy in humans and animals with no interspecies relationship. Based on the reported studies, these viruses appear unlikely to be responsible for any significant occurrence of human disease, particularly lymphoid malignancies. Although a definitive statement of no risk to human health is probably unwarranted, the evidence to date indicates that the risk is low and perhaps nonexistent. Thus, no specific public health recommendations regarding retrovirus-infected animals or poultry are warranted at this time.

Detection of Antibodies to Pasteurella multocida by capture enzyme immunoassay using a monoclonal antibody against P37 antigen.

As infection with Pasteurella multocida is common in rabbits, an enzyme immunoassay (EIA) was developed for its detection. A murine immunoglobulin G monoclonal antibody was used to capture a 37-kDa polypeptide of P. multocida serotype A:12 in an EIA to detect antibodies to P. multocida. The 37-kDa antigen was selected since it was previously shown to be a major immunogen during P. multocida infection in rabbits. The sensitivity of the P37 EIA, determined with sera from 56 rabbits infected with P. multocida, was 98%. Specificity, evaluated with sera from 62 rabbits from colonies free of P. multocida, was 92%. Titration curves of sera from rabbits immunized with P. multocida serotype A:3 or A:12 coincided, indicating that the P37 EIA was equally efficient in detecting antibodies to the two major serotypes of the organism. Comparison of the P37 EIA with the current serodiagnostic test, a bacterial lysate EIA, revealed relatively good correlation (r = 0.68). However, specificity was greatly improved, as 34% of uninfected rabbits were falsely positive by the lysate EIA whereas only 3% of uninfected rabbits were falsely positive by the P37 EIA. The coefficient of variation for same-day tests was 10%, and that for interday tests was 15%, indicating good reproducibility. The greater sensitivity and specificity of the P37 EIA should significantly enhance diagnostic capability to identify rabbits infected with P. multocida.

The effect of combined rotavirus and Escherichia coli infections in rabbits.

In rabbits, experimentally induced rotavirus infection results in soft feces only; thus it is unlikely that it is the sole cause of the severe, often fatal diarrhea of weanling rabbits with which it is associated. To determine whether rotavirus acts synergistically with another pathogen, New Zealand White rabbits (10 to 38 weeks old) were inoculated with rotavirus (L:ALA:84) and/or Escherichia coli 015:H-(RDEC-1) via orogastric tube. A single dose of high-titer (10(6) fluorescent focus-forming units) rotavirus was used, whereas E. coli was administered in various doses (10(2) to 10(9) CFU) to determine the titer of E. coli that induced only mild diarrhea but, when combined with rotavirus, resulted in diarrheal disease. Doses of E. coli > 10(6) CFU resulted in infection in almost all rabbits 10 to 16 weeks old, as detected by fecal shedding, regardless of whether rotavirus was inoculated simultaneously. However, inoculation of > 10(6) CFU of E. coli, in conjunction with rotavirus, resulted in increased morbidity and mortality due to diarrheal disease compared with E. coli alone. Inoculation of rabbits 28 to 38 weeks old with similar doses of rotavirus and E. coli caused infection but failed to induce diarrhea, indicating that older rabbits were more resistant to the pathogenic effects of these two agents. A synergistic effect between rotavirus and E. coli occurred, causing more severe diarrheal disease in weanling rabbits than that resulting from either pathogen alone.

Descriptive features of Dientamoeba fragilis infections.

A total of 237 cases of Dientamoeba fragilis were identified by a state public health laboratory in 1985 and 1986. Dientamoeba fragilis was the only parasite found in about two-thirds of the cases. Compared to Giardia cases diagnosed in a similar time period, D. fragilis occurred more frequently in females and in children 5-9 years old; it was also more likely to be detected in spring and summer months. Giardia occurred more frequently in children 0-4 years old. Seventy-nine per cent of 70 interviewed D. fragilis cases reported symptoms associated with infection; nearly 80% had diarrhoea or loose stools. Interviewed cases reported more household and non-household exposure to children 5-9 years old than children of other ages. The difference in age and sex distribution of D. fragilis and Giardia cases may be related to the life cycle and mode of transmission of the two protozoans.

Cerebral larva migrans caused by Baylisascaris sp in pet rabbits.

Cerebral larva migrans was diagnosed histologically in 4 pet rabbits that developed progressive neurologic disease. Larvae of Baylisascaris sp were isolated from brain tissues in 2 rabbits. The clinical syndrome of progressive torticollis and ataxia manifested by these rabbits is commonly associated with otitis and labyrinthitis attributable to bacterial infection; however, the middle ears were normal on radiographic and postmortem examinations. The severe encephalopathy that developed in these rabbits was indicative that just a few Baylisascaris larvae may cause extensive brain injury. During the summer, all of the affected rabbits were maintained outdoors in suburban areas, where raccoons, the final host of B procyonis, are commonly observed. Raccoon feces containing B procyonis eggs constitute a health risk for rabbits, as well as for human beings.

Prevalence of coronavirus antibodies in rabbits.

Antibodies to coronavirus were detected by an indirect fluorescent antibody test in rabbit sera from six rabbitries. The prevalence ranged from 3 to 40% in different rabbitries and most seropositive rabbits were more than 4 months old. A rabbitry with high prevalence of antibodies and high incidence of diarrhea could serve as a source of virus and aid in studying the natural history of coronavirus infection in rabbits.

Use of survival analysis to compare cull rates between bovine leukemia virus seropositive and seronegative dairy cows.

Bovine leukemia virus (BLV) infection and culling of cows in a commercial dairy herd were evaluated to determine whether a relation existed between the 2 factors. Cattle from the study population, a Holstein dairy herd consisting of approximately 400 milking cows, were tested for antibodies to BLV, using the agar gel immunodiffusion test, semiannually for 2 years, annually for 2 years, and when cattle were culled. Complete records of BLV test results were available for 849 (79%) of the 1,078 cattle that had at least 1 test during the study period. Using the Cox hazard model, the cull hazard rates (culls/cow-months) were greater for BLV seropositive cows than for seronegative cows > 36 months old. Hence, among older dairy cows, BLV-infected cows were culled prematurely, compared with uninfected cows.

Toxin production by Pasteurella multocida isolated from rabbits with atrophic rhinitis.

Naturally acquired turbinate atrophy in rabbits was associated with Pasteurella multocida infection. Several in vitro and in vivo studies were conducted to document toxin production from P multocida isolates and to determine the relation of toxin to atrophic rhinitis in rabbits. Ten isolates of P multocida serotype A:12 were obtained from adult New Zealand White rabbits with noninduced atrophic rhinitis. Specific-pathogen-free rabbits inoculated intranasally with isolates of P multocida developed rhinitis and turbinate atrophy. However, inoculation with filtrates of the same bacteria failed to induce turbinate atrophy. Cytotoxicity was observed in assays, using bovine embryonic turbinate cell cultures with extracts of P multocida, but not in agar overlay cytotoxicity assays, using bovine embryonic turbinate, bovine embryonic lung, or Vero cell cultures, or in a sandwich ELISA, using monoclonal antibodies to purified P multocida toxin. Thus, turbinate atrophy was experimentally reproduced in rabbits with isolates of P multocida, but toxin was only detected in vitro by cell culture assay of P multocida extracts.

The role of exposure to animals in the etiology of Campylobacter jejuni/coli enteritis.

To determine the role of animals as possible sources for human infection with Campylobacter jejuni/coli, 218 human cases of Campylobacter enteritis diagnosed among members of Group Health Cooperative of Puget Sound, King County, Washington, from April 1982 through September 1983 were compared with 526 controls, randomly selected from Group Health Cooperative members. All subjects were questioned regarding animal exposures one week prior to illness (cases) or interview (controls). There was no increase in risk for C. jejuni/coli enteritis associated with contact with various animals. However, exposure to diarrheic animals was associated with a fourfold increase in the risk of C. jejuni/coli enteritis (odds ratio = 4.3, 95% confidence interval (CI) 1.9-9.7). Adjustment for potential confounding factors by logistic regression analysis yielded an odds ratio of 3.3 (95% CI 1.2-7.5) associated with such exposure. An estimated 6.3% of cases of C. jejuni/coli enteritis was attributed to exposure to diarrheic animals.

Effects of bovine leukemia virus infection on production and reproduction in dairy cattle.

The purpose of this study was to determine the effects of bovine leukemia virus (BLV) infection on production, reproduction and longevity in dairy cattle. The study population was a commercial Holstein dairy herd of approximately 400 milking cows. Cattle were tested for antibodies to BLV at least annually for three years and when culled. Four groups of culled cows were compared: seronegative cows (n = 79), seropositive cows without lymphocytosis (n = 176), seropositive cows with lymphocytosis (> or = 9,000 lymphocytes/microliter) (n = 74), and seropositive cows with lymphosarcoma (n = 29). Seropositive groups of cows were bred more times and had longer calving intervals than seronegative cows. The seropositive groups had greater 305-day ME (mature equivalent) FCM (3.5% fat-corrected milk) per lactation and were older when culled than seronegative cows. However, the percent fat per lactation was greater in seronegative cows. In the last complete lactation, differences in 305-day ME FCM, days open and cull age between groups were reduced and none were significant (p > 0.05). In the cull lactation, only cows with lymphocytosis had reduced milk production relative to seronegative cows, although this difference was not significant. After adjustment for initial production and reproductive values, only seropositive nonlymphocytotic cows were culled at a significantly older age than seronegative cattle. Lymphocytotic cows were culled four months younger on average than nonlymphocytotic seropositive cows. Hence, BLV infected cows had greater milk production on average than uninfected cows. Adverse effects of BLV infection were primarily limited to lymphocytotic cows which were culled earlier and had reduced milk production in the cull lactation.

Factors associated with intestinal amyloidosis in pigtailed macaques (Macaca nemestrina).

Factors associated with intestinal amyloidosis in pigtailed macaques (Macaca nemestrina) were studied in 74 cases at the Washington Regional Primate Research Center. The medical records of monkeys during the 5-year period from 1983 to 1988 were analyzed to determine the age at death, age at first episode of diarrhea, number of episodes of diarrhea, episode and cumulative duration of diarrhea, and etiologies of diarrhea. Univariate analysis, using one control for each case, indicated that only episode duration was related to intestinal amyloidosis. Affected monkeys had significantly longer mean episode durations of diarrhea. None of the etiologies examined--bacteria, protozoa, fungi, and simian retrovirus--were significant risk factors for amyloid deposition in the intestinal tract.

Polypeptides associated with Pasteurella multocida infection in rabbits.

Polypeptides from whole cell preparations of Pasteurella multocida serotypes A:12 and A:3 were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose paper. Antigens were detected by immunoblot analysis, using sera from 3 groups of rabbits. Sera were obtained from rabbits inoculated intranasally with P multocida serotype A:12 or A:3, from rabbits maintained in a rabbitry with enzootic P multocida A:12 infection, and from rabbits maintained in a rabbitry with enzootic P multocida A:3 infection. Immunoblot analyses of pre- and postinoculation sera from experimentally infected rabbits, using serotype A:12 antigen, revealed 3 polypeptides with approximate molecular mass of 28, 30, and 37 kDa that consistently detected antibodies after P multocida-induced infection. Sera from rabbits naturally infected with either serotype, tested against serotype A:12 and A:3 antigens, detected the same polypeptides in both serotypes. Thus, immunologic reactivity to these polypeptides may be useful for serologic detection of P multocida infection.

Comparison of Freund's and Ribi adjuvants for inducing antibodies to the synthetic antigen (TG)-AL in rabbits.

Antibody responses and health parameters were compared in rabbits immunized with a synthetic polypeptide antigen, [L-Tyr,L-Glu,DL-Ala]-poly-L-lysine ((TG)-AL), in Freund's (FA) or Ribi (RA) adjuvants. Rabbits, 12 weeks old, of both sexes, were inoculated with 0.5 ml divided between two intramuscular (i.m.) sites. Eight received FA and antigen (50 micrograms); eight RA and antigen, eight PBS and antigen; four FA and PBS; four RA and PBS, and four PBS. Identical booster inoculations were made 21 days later, except that incomplete FA was substituted for complete FA. Rabbits were monitored until euthanasia and necropsy 7 weeks after the primary inoculation. Sera, obtained weekly, were analyzed for immunoglobulins using an enzyme immunoassay. Only rabbits given antigen with adjuvant produced high titered antibodies. Mean optical density values for immunoglobulin (Ig)M were greater the week after the booster in the group given FA. IgG values were similar for both adjuvant/antigen groups the week after the booster, but thereafter decreased in rabbits given RA. Antisera from rabbits given antigen with FA had greater avidity for the antigen than that from rabbits given antigen with RA, however, the difference was not significant (p greater than 0.05). Rabbits inoculated with FA and antigen had high serum creatinine kinase levels the day after inoculation, showed evidence of discomfort, and extensive granulomatous inflammation at the inoculation sites. Lesions were minimal to mild in rabbits given antigen with RA and PBS with either adjuvant. While RA did not result in adverse side effects, the IgG response to (TG)-AL with RA was transient compared to FA.

Hypervitaminosis A and reproductive disorders in rabbits.

Reproductive abnormalities in New Zealand White rabbits at a large commercial rabbitry were linked to an excess of dietary retinyl acetate. Fetal resorptions, abortions, and stillbirths were common in pregnant does. Examination of aborted and stillborn fetuses disclosed hydrocephalus, microencephaly, and cleft palate. Analysis of the commercially prepared feed disclosed a total vitamin A content of 102,278 IU/kg, of which 97,618 IU was retinyl acetate (recommended total vitamin A concentrations are 6,000 to 12,000 IU/kg). Levels of vitamin A in the plasma of does with reproductive disorders were 517 to 1,667 ng/ml (normal level is 300 ng/ml), and liver levels were 2,070 to 12,854 micrograms/g (normal range is 50 to 300 micrograms/g).

Rectal palpation and transmission of bovine leukemia virus in dairy cattle.

To determine whether rectal palpation, using common obstetrical sleeves, serves as a mode of transmission of bovine leukemia virus in dairy cattle, field studies were conducted at 2 dairies. At a commercial dairy, significant difference was not observed in rate of seroconversion in heifers and cows in which the same sleeve or new sleeves were used for palpations. At a university dairy, where cattle were used to teach dairy husbandry and veterinary procedures, significantly (P less than 0.02) greater rate of seroconversion was observed in heifers and cows palpated with unwashed common sleeves than that observed in heifers and cows palpated with sleeves washed between use. Although rectal transmission of bovine leukemia virus under field conditions was documented, it was related to frequency of palpation and age of cattle.