Serological detection of multiple retroviral infections in cattle: bovine leukemia virus, bovine syncytial virus and bovine visna virus.

Individual experimental animals used in our studies on bovine leukemia virus (BLV) are routinely screened for the presence of antibodies to the three bovine lymphotropic retroviruses. We utilized these screening methods to examine frozen sera from eight herds for antibodies to BLV, bovine visna virus (BVV) and bovine syncytial virus (BSV). Serum samples from 235 animals in four dairy and four beef herds were analyzed. Detection methods used included indirect fluorescent antibody tests of virus-infected cell cultures (BLV, BSV, BVV) and agar gel immunodiffusion (BLV). Sera from the BLV-infected animals in the dairy herds showed the highest single (50%, 49/97) and multiple (30%, 29/97) infections compared with 5% (7/138) and less than 1% (1/138), respectively in the beef herds. Single BVV infections were not detected in the dairy herds, but 11% (11/97) of the sera contained antibodies to BVV plus BLV or BSV. Five sera from beef cattle had antibodies only to BVV and four were obtained from one herd. Only one beef serum of the 138 tested demonstrated multiple antibodies (BLV, BVV).

Characterization of infertility and bovine leukemia virus infection in beef bulls on southwestern Louisiana coastal range.

One hundred and twenty-six beef bulls on southwestern Louisiana coastal range were evaluated for breeding soundness. Samples were taken to determine the incidence of bovine leukemia virus (BLV) infection, and the prepuce was cultured for potential pathogens. A high incidence (47.6%) of questionable and unsatisfactory potential breeders resulted mainly from 37.0% of the bulls exhibiting high numbers of abnormal sperm cells in the semen. Only bulls in the 4-to 5-yr age group exhibited the expected incidence of normal spermiograms. Genital campylobacteriosis was not diagnosed but there was genital trichomoniasis in three of the seven herds. Hemophilus somnus , mycoplasma and ureaplasma were isolated from the prepuce of 13.3, 48.8 and 36.7% of the bulls, respectively. Isolation of these organisms from the prepuce did not appear to be associated with abnormal spermiograms. Of the bulls studied, 34.4% had positive AGID reactions for BLV. Bulls seropositive to BLV had an increased incidence of leukocyte counts that were above the normal range. There was no apparent relationship between BLV infection and abnormal spermiograms.

Toxic Bermuda grass tremor in the goat: an electroencephalographic study.

Tremorgenic Bermuda grass hay harvested during the 1971 Louisiana outbreak of toxicosis and kept in cold storage until 1979 was fed to a female Nubian cross goat. Cortical EEG from chronically implanted screw electrodes was recorded daily during hay consumption. Typical clinical signs of toxicosis were manifested as ataxia on day 8 and tremor on day 11. Motor activity returned to normal 2 days after reinstitution of nontoxic Bermuda grass hay. Changes in EEG amplitudes, frequency content, or wave-forms were not seen during the development or after the appearance of toxicosis. The administration of diazepam at the height of toxicosis suppressed the tremor for several hours.

Effects of a Cassia occidentalis extract in the domestic chicken (Gallus domesticus).

The effects of an orally administered Cassia occidentalis extract were studied in chickens. A 25 mM sodium bicarbonate solution effectively extracted the toxic principle. Toxic activity was reduced, but not eliminated, when the heated extract (90 C, 40 minutes) was administered. The toxic principle was in the pellet after centrifuging the extract at 38,000 X g. Daily administration of the extract produced weight loss and muscular weakness. Microscopic examination revealed skeletal and cardiac muscle degeneration and hepatocyte vacuolation. Electron microscopic examination revealed mitochondrial disruption. Respiratory studies on liver mitochondria isolated from treated chickens demonstrated lower phosphorylation ratios, lower respiratory control ratios, and lower rates of oxygen use.

An immunodiffusion test for detection of bovine viral diarrhea virus antibodies in bovine serum.

An immunodiffusion test (IDT) was developed for detecting bovine viral diarrhea virus antibodies in bovine serum. The antigen utilized in the IDT was prepared from bovine viral diarrhea virus-infected monolayer cultures. Results of the IDT were obtained within 48 hours and correlated with the virus-neutralization test.

Microimmunodiffusion test for detection of antibodies to infectious bovine rhinotracheitis virus in bovine serum.

A microimmunodiffusion test (MIDT) specific for detection of antibodies to infectious bovine rhinotracheitis (IBR) in bovine serum has been developed. The antigen used in the MIDT was prepared from IBR virus-infected Madin-Darby bovine kidney cells grown in tissue culture. The antigen was stable, and relatively high yields were obtained readily. Results of the MIDT were obtained within 48 hours and agreed with those of the serum-neutralization test.

Transmission of bovine leukemia virus by Tabanus fuscicostatus.

Bovine leukemia virus (BLV) was transmitted by horse flies, Tabanus fuscicostatus, from a cow with a lymphocyte count of 31,500/mm3 to goats and dairy calves. As few as 10 and 20 flies transmitted BLV to goats and calves respectively, but the minimal number of flies required to transmit the infection was not established. Groups of 150 and 100 T fuscicostatus transmitted BLV to beef calves from a cow with a lymphocyte count of 14,600/mm3. These results support a role for horse flies in the horizontal transmission of BLV.

Serological study of the incidence and prevalence of antibodies to bovine leukemia virus in aged sera.

Ninety-seven sera collected from 21 animals that had been repeatedly sampled more than 17 years before and stored at -18 degrees C were tested for bovine leukemia virus antibodies using the agar gel immunodiffusion test. The prevalences for the different ages matched current prevalences in the same herd. The consistency of these results over a prolonged period suggests the validity of long-term retrospective seroepidemiological studies of this disease. Because the original titers could not be determined and some indications of a possible loss of activity, the results must be interpreted with a measure of caution.