PESTIVIRUSES

PETER H. RUSSELL, BVSc, PhD, FRCPath, MRCVS

Department of Pathology and Infectious Diseases, The Royal Veterinary College,

Royal College Street,

London NW1 OTU.

E-mail Web site

LEARNING OBJECTIVESStudents 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 2000. 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 1963. 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

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

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.