What do we know about Classical swine fever's return to Japan?

For the first time in 26 years, Classical swine fever or 'hog cholera' has been identified on a farm in Gifu city, Japan
calendar icon 13 September 2018
clock icon 3 minute read

Often indistinguishable from African swine fever until pathology tests are complete, Classical swine fever (CSF) can affect any age group in a herd and mortality rates are high making it one of the most economically-damaging pandemic viral diseases of pigs in the world. CSF affects wild boar and domestic pigs but is not a risk to humans.

The most recent case has emerged in a pig herd in Japan where initial tests for CSF produced negative results, however, after a second round of tests were completed, a positive result indicated that the herd was indeed infected with the highly virulent disease.

According to reports from Channel News Asia, 80 pigs had died before the disease was identified and 610 pigs were subsequently slaughtered to prevent the disease from spreading. A strict disinfection procedure took place within 24 hours of culling the herd.

The last case of CSF in Japan was eradicated in 1992 therefore a government team of specialists are investigating the possible infection routes. All pork exports from Japan have been suspended until further notice.

How does CSF present in pigs?

Initial signs may only present in a small group within the herd:

  • fatigue;
  • depression;
  • reluctance to move;
  • inappetence;
  • may appear constipated;
  • shivering or shaking;
  • young piglets may shiver and huddle together;
  • sudden death.

As more pigs begin to show signs of pathology and the disease progresses, more obvious signs of illness present:

  • yellow/grey diarrhoea or scours;
  • conjunctivitis of the eyes which begins as a thin discharge and progressing to a thick, adhesive discharge;
  • swollen, red eyes;
  • high fever;
  • weight loss;
  • muscle weakness and lameness;
  • partial paralysis;
  • vomiting;
  • purple colouration of skin beginning at ears and tail, followed by the snout, lower legs, belly and back;
  • abortion, embryo loss, mummification of piglets;
  • convulsions;
  • high mortality rate.

Classical swine fever is a notifiable disease. In all suspected CSF cases, laboratory tests should be done to confirm the diagnosis. Investigations are usually carried out by the authorities.

It is best to send whole dead pigs to the diagnostic laboratory so the pathologists can sample what they want. If only samples can be sent, the tonsils are best.

If you are worried about any abnormal health issues in your pig herd, try our Disease Problem Solver to check if your clinical signs match some of the hundreds of diseases we document on The Pig Site

Emily Houghton

Editor, The Pig Site

Emily Houghton is a Zoology graduate from Cardiff University and was the editor of The Pig Site from October 2017 to May 2020. Emily has worked in livestock husbandry, and has written, conducted and assisted with research projects regarding the synthesis of welfare and productivity of free-range food species.

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