Update of the Aujeszky's disease situation in Argentina

There are approximately 3 million pigs in Argentina. The production system is mainly extensive (40%) and semi-extensive (40%), being intensive in only 20% of the farms. Aujeszky's Disease (AD) has been described in South America since 1912, however Argentina remained apparently free until 1979. Since then, a number of outbreaks have been described and confirmed by virus isolation. In 1996, the National Animal Health Service (SENASA) established an AD control programme based on serological detection of infected animals by using an ELISA. This programme is compulsory in breeding farms, since the animals to be commercialised must be certified free of AD. Seropositive animals are segregated or sent to the slaughterhouse. In addition, a voluntary vaccination programme is carried out using an inactivated deleted vaccine (gE). The Virology laboratory of the Faculty of Veterinary Sciences, National University of La Plata is a reference laboratory to SENASA for this disease. Since 1987, the laboratory has been engaged in diagnosis and research on AD. Epidemiological studies, viral isolation and characterisation of AD virus isolates have been performed. From 1988 to 1990 a national serological screening was performed to detect AD antibodies. A total of 5955 sera belonging to 265 farms were tested by ELISA; 624 of these sera (10.5%) taken from 68 farms (25.7%) were seropositive. Similar percentages were found in recent serological studies (data provided by SENASA from a 1998 survey). Several AD viral strains were isolated and characterised from different outbreaks. All Argentine isolates showed similar biological and physicochemical behaviour. The genome of the isolates was analysed using restriction enzymes. Two genome types of the AD virus were found: types I and II as classified by the BamHI cleavage pattern. Major outbreaks have been caused by type I viruses while only one type II virus outbreak has occurred so far in an imported herd. AD is an enzootic disease in Argentina. Genome type I is the major causative agent of infection. A control programme for the disease was established 3 years ago and voluntary vaccination was started in 1998