Epidemiology of natural transmission of bovine leukemia virus infection / by Mark Cy Thurmond.

Abstract

A 27-month study examined 473 dairy cattle for associations between bovine leukemia virus (BLV) infection and host and environmental factors. Cattle sera were tested at monthly intervals for BLV antibodies by agar-gel immunodiffusion using the glycoprotein-51 antigen. A model of BLV colostral antibody decay in 130 calves predicted infection in calves less than six months of age and estimated antibody half-life to be 27.1 ±1.2 days. Colostral antibody decay did not differ between BLV-infected and noninfected calves for slope (p = 0.45) or intercept (p = 0.43). By 95 days of age, 50% of the calves had no detectable BLV colostral antibodies. Of 125 calves born to BLV-infected cows and followed for at least four months, eight (6.4%) had precolostral BLV antibodies, as determined by radioimmunoassay using the glycoprotein-51 antigen-In utero infection with BLV was not associated with dam age (p = 0.86), dam parity (p = 0.83), breed (p = 0.66), sex (p = 0.11), or stage of gestation in which the dam was infected (p=0.50). Calves infected in utero did not pose an increased risk of infection to calves penned next to them (p = 0.61). Prevalence rates of infection were 9%, 16%, and 63% at 6, 16, and 27 months of age, respectively. Age-specific rates of infection were not associated with dam age (p = 0.79), dam parity (p=0.75), dam BLV-status (p = 0.46), breed (p = 0.86), or BLV-status of colostrum consumed (p=0.50). An algorithm was described which allocated probabilities of infection to locations occupied by an animal prior to detection of infection. Small calf pastures were associated with less infection than was the calf barn (p< 0.05). No less infection was associated with individual outdoor calf pens compared to contiguous indoor pens (p>0.05). Risk of infection associated with the dry herd was five times that for heifer pastures (p< 0.0001) and accounted 24 infections per 100 heifers per 100 days at risk. Vaccination for infectious diseases was not associated with increased BLV infection (p=0.33). Infection rates were not associated with month of birth (p = 0.24) or with season of potential arthropod vectors (p = 0.20). Heifer infection was likely to occur in late v/inter or spring (p =. 01). Interacting Computing (MUSIC) version 4.1, 197 8.

Incidence of clinical mastitis in a random sample of dairy herds in the southern Netherlands

“…An appropriate interpretation of the bmscc is often difficult because of the multifactorial nature of variations in the quantity. The main reasons are that the bmscc is a function of the percentage of quarters infected, of the severity and duration of the infection (Thurmond 1987) and of management factors (Reneau 1986). Schukken and others (1989a) reported a rate of incidence of clinical mastitis of 17·9 cases per 100 cows per year in 1985 to 1986 in 125 herds with a low bmscc (<150,000 cells/ml) in the central part of the Netherlands.…”

In Defense of an Error: Intellectual Corruption in Contemporary Science

“…While the books on Dr. Blank's list were of no value what so ever in documenting his printed allegation, university officials were loath to deal with that basic fact, consistent in their failure to do so and all but lined up to sacrifice the functional quality of their organization for the sake of maintaining its immediate, hollow image [25].…”

Estudio serológico de Leucosis Enzoótica Bovina en un predio de la provincia de Valdivia y su relación a parámetros productivos y reproductivos

“…En cuanto a la transmisi6n del agente, se mencionan diversos modos como: transmi-si6n vertical, iatroginica, venkrea, contact0 fisico estrecho y por artr6podos (3, 7, 12, 16, 17,18,20,21).…”

“…Se describen ademis otros mktodos de diagn6stic0, entre 10s que se pueden nombrar a1 Radio Inmuno Ensayo (RIA), el Enzimoinmuno Ensayo (ELISA) y la Inhibici6n de la Formacibn de Sincicios (8, 10,18,22).…”