Pseudorabies

Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that has been endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever (hog cholera) has been eradicated. Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species. Aujeszky's disease, usually called pseudorabies in the United States, is a viral disease in swine that has been endemic in most parts of the world. It is caused by Suid herpesvirus 1 (SuHV1). Aujeszky's disease is considered to be the most economically important viral disease of swine in areas where classical swine fever (hog cholera) has been eradicated. Other mammals, such as cattle, sheep, goats, cats, dogs, and raccoons, are also susceptible. The disease is usually fatal in these animal species. The term 'pseudorabies' is found inappropriate by many people, as SuHV1 is a herpesvirus and has a DNA based genome (rabies virus has an RNA based genome). Research on SuHV1 in pigs has pioneered animal disease control with genetically modified vaccines. SuHV1 is now used in model studies of basic processes during lytic herpesvirus infection, and for unravelling molecular mechanisms of herpesvirus neurotropism. In 1902, a Hungarian veterinarian, Aladár Aujeszky, demonstrated a new infectious agent in a dog, ox, and cat, and showed it caused the same disease in swine and rabbits. In the following decades the infection was found in several European countries, especially in cattle, where local intense pruritus (itching) is a characteristic symptom. And in the United States a well known disease in cattle called 'mad itch' was concluded to be in fact Aujeszky's disease. The virus is shed in the saliva and nasal secretions of swine infected by the respiratory route. Aerosolization of the virus and transmission by fomites also may occur. The virus may potentially survive for seven hours in humid air, and it may survive on well water for up to seven hours, in green grass, soil, and feces for up to two days, in contaminated feed for up to three days, and in straw bedding for up to four days. Diagnosis is made mainly by virus isolation in tissue cultures, or through ELISA or PCR tests. Vaccines are available for swine (ATCvet codes: QI09AA01 (WHO) inactivated, QI09AD01 (WHO) live, plus various combinations). The infection has been eradicated in a number of European countries. In the United States, the domestic swine population in 2004 was declared free of Aujeszky's disease, though the infection still remains in feral pig populations. Respiratory infection is usually asymptomatic in pigs more than 2 months old, but it can cause abortion, high mortality in piglets, and coughing, sneezing, fever, constipation, depression, seizures, ataxia, circling, and excess salivation in piglets and mature pigs. Mortality in piglets less than one month of age is close to 100%, but it is less than 10% in pigs between one and six months of age. Pregnant swine can reabsorb their litters or deliver mummified, stillborn, or weakened piglets. In cattle (see next section), symptoms include intense itching followed by neurological signs and death. In dogs, symptoms include intense itching, jaw and pharyngeal paralysis, howling, and death Any infected secondary host generally only lives two to three days. Genital infection appears to have been common in a great part of the 20th century in many European countries in swine herds, where boars from boar centres were used for natural service of sows or gilts. This disease manifestation has always been asymptomatic in affected pigs, and presence of the infection on a farm was detected only because of cases in cattle showing pruritus on the hindquarters (vaginal infection, see below). In susceptible animals other than swine, infection is usually fatal, and the affected animals most often show intense pruritus in a skin area.Pruritus in Aujeszky's disease is considered a phantom sensation as virus has never been found at the site of pruritus.