Epidemiology and eradication of bovine viral diarrhoea virus infections : studies on transmission and prenatal diagnosis of persistent infection

Sammanfattning

This thesis describes the principles for eradication of bovine viral diarrhoea (BVDV) from cattle populations without the use of vaccines, as they have been applied in the Scandinavian countries since 1993-94. It also presents five studies concerning transmission of BVDV and prenatal diagnosis of persistent BVDV infection. The studies relate to large-scale eradication by addressing issues of importance for elimination of virus in infected herds, for management of recently infected herds and for prevention of BVDV transmission through livestock trade. Transmission of primary type I BVDV infections in the absence of persistently infected (PI) animals was studied. Calves undergoing acute infection with BVDV were brought in contact with healthy, non-immune calves. Also, calves inoculated with BVDV were housed with non-immune calves, while they all underwent a concurrent infection with bovine coronavirus. In both studies, none of the in-contact calves seroconverted. This suggests that primary infections are of low infectivity and that virus circulation will cease after PI animals have been removed. The ability to identify dams pregnant with PI foetuses (PI carriers) before parturition was investigated. Using an indirect antibody ELISA on samples taken in late gestation, it was possible to discriminate PI carriers from other antibody positive pregnant cows in herds with ongoing infection. It was also possible to detect viral antigen in foetal fluids from PI carriers by an RT-PCR assay and by virus isolation (VI). RT-PCR was superior to VI in this respect. Serology can be used to prevent PI carriers from being traded, and both methods can be used to delimit outbreaks of BVDV in infected herds. The infectivity associated with foetal fluids and uterine lochia was tested by exposing non-immune calves to such samples. It was shown that foetal fluids can be infectious, but to a low extent. Uterine lochias are not likely to be infectious. Also, the infectivity associated with dams delivering PI calves, and their calving environment, was studied by putting susceptible calves in repeated contact with such dams after removal of the PI offspring. It was shown that rapid removal of newborn PI calves does not prevent further spread of BVDV infection to susceptible animals.

Nyckelord

cattle; pestivirus; BVDV; experimental study; test validation; foetal fluid; indirect transmission; control; risk factor

Publicerad i

Acta Universitatis Agriculturae Sueciae. Veterinaria
2002, nummer: 132
Utgivare: Swedish University of Agricultural Sciences

SLU författare

• Lindberg, Ann

  • Institutionen för idisslarmedicin och epidemiologi, Sveriges lantbruksuniversitet
    

UKÄ forskningsämne

Klinisk vetenskap

Publikationens identifierare

• ISBN: 91-576-6384-X

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/107638