Aujeszky's Disease - Pseudorabies
updated September 25, 2015
Aujeszky’s disease (AD) is caused by suid herpesvirus 1, belonging to the genus Varicellovirus in the subfamily Alphaherpesvirinae, family Herpesviridae, order Herpesvirales.
Cats are infected with ADV mainly through the ingestion of raw pork, particularly of lungs or other offal. Transmission can also be indirect, without contacts, following viral excretion by pigs. In connection with an AD outbreak in sheep, cat cases have been also observed (Henderson et al., 1995).
The disease was eliminated from the domestic pig populations of several European countries; presently, there is no appreciable risk of ADV transmission to cats. However, in wild boar populations, ADV infection may be prevalent in Western European countries, and AD is still sporadically observed in hunting dogs.
The virus enters via the oral route and replicates in tonsillar and pharyngeal tissues. It then spreads through the central nervous system via the cranial nerves and is excreted with oral and nasal secretions. However, this excretion has no epidemiological consequences, since the virus is not transmitted by cats. Histology shows a non-purulent encephalitis (Fig. 1).
This disease was encountered only sporadically, mainly in urban areas where cats were fed pig offal. As in dogs, the incubation period is short, no longer than 2 to 4 days. The infection causes an acute encephalitis, with excitation and hypersalivation as the initial clinical signs. The cat presents with anorexia, sometimes with intense pruritus, which leads to lesions due to scratching and self-mutilation. More copious salivation ensues, the nervous signs become more pronounced, lack of coordination ensues and finally results in paralysis. When this clinical picture is observed, it may be mistaken for rabies. However, cats that develop AD are rarely aggressive, and disease progression is more rapid than in rabies. The outcome is invariably fatal, within 12 to 48 hours after onset of the clinical signs (Maes et al., 1987).
Immunoperoxydase staining can be done on brain sections; the nuclei of infected cells would show a brownish precipitate (Fig. 2).
A PCR for the detection of ADV in pigs can be used on brain and lung tissue homogenates from cats. However, when encephalitis is seen in cats, and pseudorabies is suspected, the differential diagnosis with rabies must always be performed.
AD disease management
There is no treatment for this deadly disease.
The attenuated ADV vaccines used to protect pigs are still virulent for carnivores, including cats. Only inactivated or subunit vaccines are safe, but they have not demonstrated any efficacy against AD in cats. Infection of cats (and dogs) can be prevented by cooking pig meat or pork offal, by feeding commercial pet food, and avoiding contact with infected pigs (Thiry, 2006).
Henderson JP, Graham DA, Stewart D. An outbreak of Aujeszky's disease in sheep in Northern Ireland. Vet Rec. 1995; 136: 555-557.
Maes L., Pensaert M. Pseudorabies virus (Aujeszky’s disease). In: Virus infections of carnivores (M.J. Appel, editor), Elsevier Science Publishers, Amsterdam, 1987, 241-246.
Thiry E., Aujeszky’s disease. In: Clinical virology of the dog and cat, Editions du Point Vétérinaire, Wolters-Kluwer, Reuil-Malmaison, France, 2006, 125-126.