Aujeszky's disease : factors important for epizootiology and control

Abstract

In Europe it is widespread and only a few countries are free from the disease. AD virus (ADV) is fairly resistant to heat and very stable at normal temperatures and in the cold. Its pH stability ranges from 5.0 to 12.0. The most efficient disinfectants are chemicals that liberate chlorine, and formaldehyde. NaOH is less effective. Lime is recommended for disinfection of slurry. Because of its pH and temperature stability, ADV is very resistant to natural environmental conditions. Pigs are the primary host of the virus, although a large number of other species can be infected naturally and experimentally. Infection chiefly takes place by nasal and/or oral routes. The virus can further be transmitted to the fetus, and by mating or by artificial insemination. The virus is not very contagious. Primary virus multiplication occurs in the naso-pharyngeal region and the respiratory tract. ADV enters the CNS by the neural pathway. The virus is disseminated within the body by lymphocytes and macrophages. The virus is mainly excreted by nasal and oral excretions, but it is also present in the ejaculate, vaginal secretion and milk. ADV infection evokes antibody production and cell-mediated immunity. The ADV genome persists in infected pigs in a latent state for life. It can be reactivated by stress, and virus excretion then occurs. Vaccination of pigs is successful in controlling clinical outbreaks. Inactivated and live vaccines are used, though the latter carry more risks. Vaccinated pigs are protected only against small quantities of the virus. With larger quantities, virus multiplication takes place and latent ADV infection is established. Vaccination of other animal species has given very contradictory results. AD is endemic in areas having a dense pig population and intensive, specialized farming management, which involves much movement of animals. Therefore the distribution of AD can differ within a country. From the epidemiological point of view, infected pigs are the main source of the spread of AD over large distances. ADV-infected breeding and artificial insemination centres are additional sources. For virus spread over short distances various sorts of vectors are involved. Air transmission is still controversial.

Evidence of Aujeszky’s disease in wild boar in Serbia

“…There is evidence that the viruses from modified live vaccine (MLV) can be shed from the oronasal cavity [ 40 ], but Terpstra and Pol [ 41 ] showed that vaccination with MLV vaccines was not likely to interfere with the laboratory diagnosis of ADV field strains. However, since the attenuated virus replicates in the body and can be excreted, transmission to other animals, reverse mutations and genetic recombination with field strains cannot be excluded [ 42 ]. The most commonly used AD vaccine in Serbia for domestic pig vaccination is made using the attenuated Bartha strain, which minimizes field virus excretion comparing to inactivated vaccines [ 43 ].…”

14_Artificial Insemination and Its Role in Transmission of Swine Viruses

“…Very high viral concentrations have been reported in semen ranging from 10 8 to 10 9 TCID 50 per ml (Medveczky & Szabo, 1981) to 10 3.7 to 10 4.9 TCID 50 per ml (Vannier & Gueguen, 1979). Transient viral excretion for up to 12 days usually occurs during the acute phase of the disease (Ressang, 1973) but viral excretion has been observed for long periods of time after natural infection (Wittmann, 1985). After experimental PRV infection by the intratesticular route, testicular degeneration and transient elevation in sperm abnormalities have been reported (Hall, Jr. et al, 1984a;Larsen et al, 1980).…”

Quantitative risk assessment of the risks associated with the importation of pigs to abattoirs

“…Winds are usually stronger and the atmospheric turbulence is greater during the day than at night; thus, the concentration of infectious virus carried downwind is higher at night (26). E 5 For intranasal infection, piglets require 10 1 -10 3 TCID 50 , young pigs approximately 10 4 TCID 50 and adult pigs 10 4 -10 5 TCID 50 (44,45). E 6 For intranasal infection, cattle require at least 10 5 TCID 50 (44).…”

“…E 5 For intranasal infection, piglets require 10 1 -10 3 TCID 50 , young pigs approximately 10 4 TCID 50 and adult pigs 10 4 -10 5 TCID 50 (44,45). E 6 For intranasal infection, cattle require at least 10 5 TCID 50 (44). E 7 Drying of PRV on glass at both 1°C and 22°C at 40-50% relative humidity resulted in a loss of 4 log 10 of virus, i.e.…”