Pseudorabies (Aujeszky Disease, Mad Itch)
What is it?
Pseudorabies is a contagious disease primarily appearing in pigs, caused by a herpesvirus called Varicellovirus suidalpha1. The disease can also affect other domesticated mammals like cattle, sheep, goats, cats, dogs, and wild animals. Younger animals die of the disease more frequently than older animals, often within two to three days of infection. Older animals will get sick and usually recover within a week or two, although some occasionally die. Since 2004, the United States has been considered free of the disease in commercial swine operations. The virus is endemic to feral pig populations and transmission to domestic pigs has been recorded. A recent detection of the virus in a commercial operation in the U.S. was ultimately traced back to feral swine introduction.
Transmission
Nose-to-nose is the most common route of transmission between pigs. The virus also can be transmitted through fecal-oral contact and via semen. However, studies point to environmental transmission also being a risk as well. The virus can survive for short periods of time on equipment and even in the air, and could be transmitted via shared water, feed or bedding.
Signs and Symptoms
Age is an important factor in identifying the signs of a pseudorabies-infected animal. Young pigs are highly susceptible, and death rates may reach 100%. Neurological signs are more common in young pigs and respiratory and reproductive signs are more common in older pigs. Weight loss is a common sign in animals of any age and unfortunately, the first sign in younger animals may often be death. Older pigs may exhibit fever, sneezing, loss of appetite, and other respiratory issues. Non-swine species will have similar signs and often have an irritated area on their skin that they continually itch. The itchy patch of skin is the reason pseudorabies may also be known as “mad itch.”
Diagnosis
Clinical signs and history are important in suspected pseudorabies. Diagnosis requires identifying the presence of the virus in an infected animal. Virus detection can be achieved through isolation in cell culture systems or through molecular tests, such as PCR assay to detect viral DNA. Brain, spleen, and lung tissue are the organs of choice for virus detection. Nasal swabs can be used for sampling virus from newly infected animals. Screening tests that look for antibodies against the virus are used. The most common and fastest test is an ELISA test. This test has the ability to screen large volumes of animals and can differentiate between natural infection and vaccinated animals.
Treatment
There is no treatment for pseudorabies. However, vaccination is available and is highly effective at reducing the spread of the virus between animals.
Prevention
In addition to vaccination, all new animals entering a herd should be tested before being allowed into the herd. Keep all pigs from having any contact with feral swine. Approximately 20% of feral swine in the U.S. are seropositive (a positive test result for exposure to a virus in the blood). The U.S. has a surveillance program in place to monitor pseudorabies in wild pigs. This program helps by keeping wild and domestic herds separate to reduce the risk of disease transmission.
Human Risk
Reports of human infection with pseudorabies are extremely rare with isolated reports of cases in China. Practicing proper biosecurity and infection control can further reduce the risk of zoonotic transmission.
Having trouble viewing this email? View it as a Web page.
|
