Control of bovine leukemia virus infection in dairy herds by agar gel immunodiffusion test and segregation of reactors.

Canadian cattle intended for export, in future, may have to originate from herds which are serologically negative for bovine leukemia virus, in addition to being negative individually by the agar gel immunodiffusion test as currently required. In this study, agar gel immunodiffusion testing of herds and segregation of reactors were examined. The results demonstrated that bovine leukemia virus infection could be controlled when three groups: 1) bovine leukemia virus-positive, 2) bovine leukemia virus-negative and 3) replacement cattle were maintained at separate locations.

Comparison of competitive and indirect enzyme-linked immunosorbent assays for detection of bluetongue virus antibodies in serum and whole blood.

An indirect (I) enzyme-linked immunosorbent assay (ELISA) and a competitive (C) ELISA, using a group-specific monoclonal antibody against bluetongue virus (BTV), are described for the detection of antibodies to BTV in cattle and sheep sera. The performance of these assays in detecting anti-BTV antibody in sequential serum samples and eluates from whole blood (WB) dried on filter paper from three calves and four sheep experimentally infected with type 10 BTV was evaluated. The C-ELISA was superior to the I-ELISA in the detection of anti-BTV antibody in the sera and WB samples from both cattle and sheep early after infection with BTV. BTV antibodies were demonstrable by C-ELISA in all the bovine and ovine sera and WB eluates by 9 days postinfection; whereas the I-ELISA results for sheep sera and WB eluates were similar, anti-BTV antibody was not detected in bovine serum and WB eluates until 26 and 14 days postinfection, respectively. While both ELISAs proved reliable, under the present test conditions involving detection of early postinfection reactions of experimentally infected animals, the C-ELISA was always as sensitive or more sensitive than the standard agar gel immunodiffusion test, the modified complement fixation test, and the plaque neutralization tests in the detection of anti-BTV antibodies. Unlike observations with the immunodiffusion test, no reaction was seen between BTV antigen and bovine epizootic hemorrhagic disease virus antiserum in either ELISA. The results suggest that either ELISA may be suitable for routine diagnostic testing and may have the potential to replace other tests for detection of anti-BTV group-specific antibodies and that the C-ELISA may have the most potential.

Eradication of bovine leukemia virus infection in commercial dairy herds using the agar gel immunodiffusion test.

Demands for bovine leukemia virus test negative breeding cattle and for semen from bovine leukemia virus test negative bulls by several countries have encouraged the eradication of bovine leukemia virus infection from selected herds in Canada. This project was undertaken to evaluate the suitability of the agar gel immunodiffusion test, standardized to detect anti-bovine leukemia virus glycoprotein antibodies, for eradication of bovine leukemia virus from commercial dairy herds. Of nine participating herds, the prevalence rate of bovine leukemia virus infection was low (less than 10%) in three, medium (11-30%) in four and high (greater than 30%) in two. The herds were tested by the agar gel immunodiffusion test, reactors were removed and the herds were then retested at regular intervals. The results indicate that it is possible to eliminate bovine leukemia virus infection from the herds after two to three cycles of agar gel immunodiffusion tests and prompt removal of the reactors.

Dermal squamous cell carcinoma in broiler chickens in Saskatchewan.

A low but widespread incidence of a dermal squamous cell carcinoma is reported in broiler chickens in Saskatchewan. The tumor appears as an irregular ulcer in the skin and is widely distributed over the body of affected birds.

Herpesvirus infection and cervical anaplasia: a seroepidemiological study.

In a cohort of 23,146 pregnant females followed for 37-56 months subsequent to collection of prenatal sera, 57 cases of carcinoma of the cervix were encountered. Three controls were selected for each case from the residual cohort matched to cases for age, residence, number of prior cytology smears taken, and the data of entry to the study. The antibody activity to herpesvirus type 1 and type 2 was examined by the indirect hemagglutination test. The proportion of cases positive for HSV-2 infection was greater than that of the controls; however, the difference was not significant at the 5% level. The relative risk value for the association between HSV-2 infection and carcinoma of the cervix was found to be 2.33. The geometric mean titers of IHAT revealed that the cases of cervical cancer had a higher titer than the controls with respect to HSV-1 as well as HSV-2 antibodies. A sufficiently longer follow-up, yielding a larger sample size, is desired to assess the specific role of HSV-2 infection in development of cervical anaplasia.

Asbestos, smoking, and laryngeal carcinoma.

This study was designed to examine the relationship between exposure to asbestos and laryngeal cancer. A retrospective study of 43 pairs of patients with laryngeal cancer and their matched controls examined a number of variables, including smoking, exposure to asbestos, and other occupational factors. Patients with laryngeal cancer and the controls were matched for age, sex, and place of residence. The data indicate a substantial association between asbestos exposure and laryngeal cancer. Cigarette smoking was also associated with the disease, although the strength of association was not as high as that for asbestos. Exposure to uranium, chromium, nickel, cobalt, arsenic, x-rays, and alcohol did not appear related to later development of carcinoma of the larynx. We conclude that exposure to asbestos and cigarette smoking are potent factors in the development of this disease.