PESTIVIRUSES PETER H. RUSSELL, BVSc, PhD, FRCPath, MRCVS Department of Pathology and Infectious Diseases, The Royal Veterinary College, Royal College Street, London NW1 OTU. Web siteWeb site

LEARNING OBJECTIVES Students should be able to: identify how swine fever virus, bovine virus diarrhoea, and border disease of sheep are related but yet distinct with regard to antigens and pathogenicity. explain the pathogenesis of acute, chronic and mucosal disease and how immune tolerant viraemic animals affect epidemiology. describe the importance of bovine pestiviruses as reproductive pathogens. describe in outline how swine fever virus was eradicated and how bovine virus diarrhoea virus is controlled in the UK.

CLASSICAL SWINE FEVER VIRUS Epidemiology: CSFV had a worldwide distribution but has now been eradicated from ill Australia, NZ., USA and some European countries eg Denmark. It can survive in formites and pig meat eg sausage.

CLASSICAL SWINE FEVER VIRUS Control: Eradicated in UK in 1971 but a Chinese- like virus (as defined by phylogenetics) entered UK in It almost certainly entered via illegally imported pigs from EU. Previous control programme started in 1963 with crystal violet inactivated vaccine in 1960 followed by slaughter policy in In 1967, reported cases down to single figures.

BORDER DISEASE VIRUS Pathogenesis:

BORDER DISEASE VIRUS Epidemiology:

BORDER DISEASE VIRUS Diagnosis: Detection of antibody by ELISA or virus by virus isolation in cell culture or by antigen detection in ELISA are the common methods for BVD diagnosis. This is usually subsequent to clinical diagnosis of abortion and the birth of 'hairy shaker' Iambs.

BOVINE VIRUS DIARRHOEA VIRUS and MUCOSAL DISEASE

The Virus

BVDV non-cytopathogenic cytopathogenic

BVDV Disease

Severe Haemorrhagic Disease due to BVDV

Transmission of BVDV

Transplacental infection

Persistently infected (PI) animals BVDV PI animals have certain characteristics:

Persistently infected (PI) animals BVDV PI animals have certain characteristics: (cont.)

Persistently infected (PI) animals (cont.)

Mucosal Disease

(cont.)

The cause of mucosal disease BVDVnc infection

The cause of mucosal disease Superinfection with BVDV c Homologous' to persisting virus

Diagnosis

Control

SUMMARY * Transplacental infections initiate events which have important pathological consequences for all three viruses. * SFV is notifiable, but has been eradicated, and the most recent suspect cases have been due to BVD infecting pigs. * Border Disease can cause serious losses in lambs in anyone year due to CNS damage and poor doers with hairy coats. It is advisable to eliminate carriers by getting rid of the entire crop of lambs that year. * BVD is a primary enteric pathogen but also a major source of loss through reproductive abnormalities. The nc isolates are important in establishing persistently infected calves that are susceptible to secondary infection with the cytopathic isolates to initiate mucosal disease. Vaccination of cows before their first insemination is recommended.