A long term epidemiological study of bovine viral diarrhoea infections in a large herd of dairy cattle

Abstract

Epidemiological aspects of bovine viral diarrhoea virus (BVDV) infections were studied longitudinally in a large dairy herd for three years. At the start of the study, practically all the cows more than four years old had BVDV antibody titres, whereas the younger stock were almost all seronegative. The spread of the virus was monitored in a part of the population that contained only transiently viraemic cattle and in another part that contained persistently viraemic calves. Among the lactating cows the virus circulated for two-and-a-half years, although they had no direct contact with persistently viraemic cattle during this period. The highest transmission rate occurred when a large number of susceptible heifers was added to the population of cows that contained transiently viraemic cattle. The circulation of BVDV among the lactating cows ceased while 27 seronegative cows were still present. Both findings are in accordance with predictions from simple epidemic models. The susceptibility of the cows that remained seronegative was confirmed experimentally. In contrast with the limited circulation of BVDV caused by transiently viraemic cattle, virtually all susceptible cattle that came into contact with a persistently viraemic calf became seropositive within three months. Transplacental BVDV infections were not detected in the calves born to cows that had antibodies against the virus due to an infection that had occurred at least four years earlier. Transplacental transmission of BVDV did not occur in most of the pregnant cows that were infected before approximately the 60th day of gestation, but when cows became infected later in gestation the virus virtually always invaded the fetus.(ABSTRACT TRUNCATED AT 250 WORDS)

Test Strategies in Bovine Viral Diarrhea Virus Control and Eradication Campaigns in Europe

“…28 In such instances, the incidence of infection within the herd tends to be low and of short duration. 17,20,36,37 Continuous seroconversion in the absence of PI animals also has been described, 30,33 but here, the literature displays a lack of consensus, as other studies suggest that acutely infected animals are unlikely to maintain the infection for longer periods. 36,37 In any case, before the first PI animal (if any) is born, the incidence of infection will be low.…”

The prevalence of bovine viral diarrhoea antibodies in selected South African dairy herds, and control of the disease

“…Reproductive syndromes and economic losses within a herd due to BVDV have been well described 1,14,24,27 . Intra-uterine infection with both the non-cytopathic and cytopathic biotypes can lead to problems such as lowered conception rates, early embryonic losses, repeat breeders, abortions, mummification and various congenital malformations.…”

A computer simulation of the transmission dynamics and the effects of duration of immunity and survival of persistently infected animals on the spread of bovine viral diarrhoea virus in dairy cattle

“…Serological surveys of prevalence of antibodies specific for BVDV have revealed levels of seropositivity of 53-72 % [1,[12][13][14][15][16][17]. While these figures are within a similar range to that generated by the model described herein, most of the reported surveys will have included animals from herds that were BVDV-free or herds in which infection had not become endemically stable.…”