A
highly contagious viral disease of
swine, hog cholera is also known as
classical swine fever virus.
Pigs and
wild boar are the only natural
reservoir of this disease.
Virus Family
Flaviviridae, genus
Pestivirus.
Signs:
Signs vary with the severity of the infection. There are three forms of the disease:
Acute:
Highly virulent. Fevers may rise to 107 °F. Convulsions. Lack of appetite. Affected pigs will pile or huddle up together. Signs of hog cholera may not be apparent for several days following infection. Death usually occurs within 5 to 14 days following the onset of illness.
Chronic
Symptoms are similar, but less severe than in the acute form. Discoloration of the abdominal skin. Red splotches around the ears and extremities. Pigs with chronic hog cholera can live for more than 100 days after the onset of infection.
Mild
Short periods of illness are often followed by periods of recovery. Eventually, a terminal relapse occurs. May cause small litter size, stillbirths, and other reproductive failures. High mortality during weaning may also indicate the presence of this mild strain of hog cholera.
Transmission
Infection routes: ingestion, contact with the conjunctiva, the mucous membranes, skin abrasions, insemination, percutaneous blood transfer.
The most common method of transmission is direct contact between healthy swine and those who carry the disease. Can also be transmitted through contact with blood, any body tissues, body secretions or excrement from infected animals. Birds, flies, and humans can physically carry the virus among swine. Swine owners can inadvertently cause infection through feeding their herds untreated food wastes containing infected pork scraps. Congenitally infected piglets are persistently viraemic and may shed the virus for months.
Treatment:
No treatment is possible. Affected pigs must be slaughtered and the carcasses buried or incinerated.
Vaccination with modified live virus strains is effective in preventing losses in countries where classical swine fever is enzootic, but is unlikely, on its own, to eliminate infection entirely. In countries which are free of disease, or where eradication is in progress, vaccination is normally prohibited.
Prevention:
To ensure pigs are free of disease, swine from countries affected by hog cholera can enter the United States only after a 90-day quarantine at a high-security import center in Key West, FL.
Swine owners who suspect their pigs may have hog cholera should immediately contact their local veterinarian or Federal or State animal health official. Taking the following steps can help swine owners prevent this disease from becoming established in the United States:
Check animals at least twice a week for unusual signs or behaviors.
Make sure food waste is properly heated to destroy pathogens.
Isolate newly purchased hogs for at least 21 days.
Isolate sick pigs until the cause of illness is determined.
Fence property to prevent wild pigs from coming in contact with domestic herds.
Practice standard biosecurity measures, such as cleaning and disinfecting clothing, equipment, and vehicles entering and leaving the farm.
Response to outbreaks:
Slaughter of all pigs on affected farms
Disposal of carcasses, bedding, etc.
Thorough disinfection
Designation of infected zone, with control of pig movements
Detailed epidemiological investigation, with tracing of possible sources (up-stream) and possible spread (down-stream) of infection
Surveillance of infected zone, and surrounding area
Hog cholera was eradicated from the United States in 1978, after a 16-year effort by the industry and State and Federal governments. Today, only 16 other countries are free of hog cholera.
Recent outbreaks in Haiti, the Netherlands, and Belgium have animal health officials at the U.S. Department of Agriculture (USDA) concerned that hog cholera could spread to U.S. swine herds. While hog cholera does not cause foodborne illness in people, economic losses to pork producers would be severe if the disease were to become established again in this country.