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United States Department of Agriculture
Animal and Plant Health Inspection Service

Classical Swine Fever

Last Modified: Oct 17, 2018
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What is Classical Swine Fever

Classical swine fever (CSF) is a highly contagious and economically significant viral disease of pigs. The severity of the illness varies with the strain of the virus, the age of the pig, and the immune status of the herd. Acute infections, which are caused by highly virulent isolates and have a high mortality rate in naive herds, are more likely to be diagnosed rapidly. However, infections with less virulent isolates can be more difficult to recognize, particularly in older pigs. The range of clinical signs and its clinical similarity to other diseases can make classical swine fever challenging to diagnose. Although classical swine fever was once widespread, many countries have eradicated this disease from domesticated swine. CSF was eradicated from the U.S in 1978.

Pigs are infected by the oral or nasal routes but can also enter via other mucus membranes as well as skin abrasions. CSF can be transmitted to healthy pigs coming into contact with contaminated vehicles, pens, feed, or clothing. Feeding swine untreated food wastes containing infected pork scraps can cause infection, making raw garbage feeding a major risk for CSF incursion into swine herds. 

Signs of CSF vary with the strain of classical swine fever virus and the age and susceptibility of the pigs. High fever, huddling, constipation followed by diarrhea and reddened eyes are often seen. The skin may show hemorrhages with discoloration of the ears, abdomen or inner thighs. Young pigs may have incoordination, or weakness. The disease can adversely affect reproduction with sows aborting or delivering stillborn or malformed piglets. Milder forms of virus or infection in partially immune pigs may exhibit mild or no symptoms and yet still harbor and spread the virus.

Prevention is the best practice since there is no treatment for classical swine fever other than supportive care. Pigs that recover may shed virus for varying periods of time, serving as an infection risk to unaffected contact pigs. CSF Vaccines are available, require USDA approval for use, and can be used to assist in outbreak response efforts.

The following links are to detailed descriptions of the surveillance program, targeted sampling populations and disease information

Classical swine fever should be reported immediately upon diagnosis or suspicion of the disease. '

Federal: Area Veterinarians in Charge (AVICS): VS District Offices Points of Contact

State: State Animal Health Officials

Classical swine fever should be reported immediately upon diagnosis or suspicion of the disease.

Federal: Area Veterinarians in Charge (AVICS): VS District Offices Points of Contact

The Classical Swine Fever (CSF) Surveillance Program is designed to enhance surveillance for the rapid detection of CSF virus introduced into U.S. swine by testing targeted swine populations in high risk states. The program is implemented by APHIS in cooperation with the National Animal Health Laboratory Network (NAHLN). The swine populations targeted for surveillance include:

  • Swine highly suspicious for CSF
  • Sick pigs submitted to a veterinary diagnostic laboratory
  • Pigs condemned at slaughter by the Food Safety and Inspection Service (FSIS), and
  • Feral swine collected by Wildlife Services (WS) 

CSF Surveillance Plan - comprehensive surveillance plan document for CSF; this is also Appendix B of the procedure manual listed below (version 2.0, updated 4/07)

CSF Surveillance Procedure Manual (updated 4/07) - provides in-depth information about the CSF Surveillance Program. Appendices include:

CSF Data Submission Forms (for program participants):

 CSF Web-Data Entry User Guides(for program participants):


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