Hog Cholera (Classical Swine Fever)

1. Hog Cholera(Classical Swine Fever) Sandra Axiak and Carolin Winter

2. Definition of hog cholera: • highly contagious viral disease of swine • can cause acute, chronic, or congenital disease • considered a foreign animal disease

3. Foreign animal disease (FAD): • Definition: • a transmissible disease of livestock or poultry • absent from the US and its territories • has the potential for significant health or economic losses • Examples of important FADs: • foot and mouth disease • highly pathogenic avian influenza • hog cholera

4. Foreign animal disease: • Control of FADs usually means eradication. • The U.S. spent $79 million during the final stages of hog cholera eradication (1971-1977) • Hog cholera was officially eradicated from the U.S. in 1978

5. Etiology: • Family Flaviviridae • Genus Pestivirus • Only one serotype of the virus • Closely related to BVDV

6. Epidemiology of HCV: • Hosts: • pigs and wild boar • Incubation period: • usually 3-4 days, but can range from 2-14 days • Distribution: • occurs in much of Asia, Central and South America, and parts of Europe and Africa • disease has been eradicated from about 16 countries, including Australia, Canada, and the United States (1978 - after a 16 year long effort)

7. Epidemiology of HCV: • Transmission: • Blood, tissues, semen, secretions, and excretions of infected animals contain HCV • transmission usually occurs via oral route • can also occur via the conjunctiva, mucous membranes, skin abrasions, insemination, common needles, and contaminated instruments

8. Epidemiolgy of HCV: • Transmission: • Feeding raw or insufficiently cooked waste food containing infected pork scraps can be a potent source of HCV • Mechanical vectors can spread HCV • farm visitors - on their person or their clothes • vehicles • insects and birds

9. Epidemiology of HCV: • Transmission: • Transplacental infection with a lowly virulent strain of HCV can result in persistently infected piglets • These piglets will persistently shed the virus for months before succumbing to the disease

10. Forms of the disease: • Acute form • Chronic form • Congenital form

11. Clinical signs of acute infection: • Fever of 106 to 108 degrees Fahrenheit • may see huddling of pigs in warmest area of pen • Lethargy and anorexia • Intermittent vomiting of yellow fluid containing bile • Transient constipation followed by diarrhea • Conjunctivitis with encrustation around the eye • Coughing and dyspnea

12. Clinical signs of acute infection: • Terminal stages of infections: • Hemorrhagic lesions of the skin, especially on the abdomen and inner aspects of the thighs • Cyanosis of the skin, especially the extremities • ears, limbs, tail, snout • Ataxia and paresis due to posterior weakness • Convulsions may occur shortly before death • Death usually occurs within 5 to 15 days of onset • Mortality can approach 100% in young pigs

13. Cyanosis of the skin (extremities)

14. Gross lesions of acute infection: • Swollen, edematous, and hemorrhagic lymph nodes • esp. submandibular and pharyngeal lymph nodes • Splenic infarcts • All serous and mucosal surfaces may have petechial or ecchymotic hemorrhages • Peritonitis, pleuritis, and pericarditis • straw-colored fluid

15. Gross lesions of acute infection: • Petechial and ecchymotic hemorrhages on: • skin • surface of the kidneys • surface of the small and large intestine • larynx • heart • epiglottis • fascia lata of the back muscles

16. Petechial hemorrhages - skin:

17. Petechial hemorrhages - kidney surface

18. Petechial hemorrhages - abdominal viscera

19. Petechial hemorrhages - larynx

20. Other lesions of acute infection: • Leukopenia and thrombocytopenia • Encephalomyelitis with microgliosis and perivascular cuffing is found in brains from about 75% of pigs acutely infected with HCV

21. Clinical signs of chronic infection: • Prolonged and intermittent periods of: • anorexia • fever • dullness • alternating diarrhea and constipation for up to a month • alopecia

22. Clinical signs of chronic infection: • May have a disproportionately large head relative to their small trunk • Apparent recovery with eventual relapse • All chronically infected pigs will die due to complications arising from HCV infection

23. Gross lesions of chronic infection: • Lesions can be similar to those found in the acute form of infection, but are generally less severe. • Button ulcers in the cecum and large intestine due to secondary bacterial infection are common • Generalized depletion of lymphoid tissue • Hemorrhagic lesions may not be present in chronically infected pigs

24. Button ulcers:

25. Clinical signs of congenital infections: • Highly virulent strain: • abortion • birth of diseased pigs that die shortly after birth • Less virulent strain: • mummification • stillbirth • birth of weak, “shaker” pigs (congenital tremor)

26. Clinical signs of congenital infections: • If infected with a lowly virulent strain during fetus’s 1st trimester of life, piglets may: • not produce neutralizing antibody to the virus • experience life-long viremia and persistently shed the virus • have few clinical signs for the first few months of life, then develop anorexia, depression, diarrhea conjunctivitis, dermatitis, runting, and ataxia • ultimately end up recumbent and die

27. Gross lesions of congenital infections: • Cerebellar hypoplasia • Microencephaly • Pulmonary hypoplasia • Central dysmyelinogenesis • Thymus atrophy • Deformities of the head and limbs • Petechial hemorrhages of the skin and internal organs towards the end of the disease process

28. Differential diagnosis: • African Swine Fever • distinguished from hog cholera only via laboratory examination • Erysipelas • Salmonellosis • Colisepticemia • Thrombocytopenic purpura • Acute pasteurellosis • Infection with BVDV

29. Diagnosis of hog cholera: • Specimens that should be collected and sent to the lab for virus isolation and antigen detection include: • tonsils (best) • submandibular and mesenteric lymph nodes • spleen, kidney, brain, and distal ileum • For living cases, collect: • tonsil biopsies and blood in EDTA • DO NOT freeze samples - interferes with some of the tests

30. Laboratory diagnosis: • Direct IFA on cryostat sections of organs or impression smears of biopsy material • ELISA - blood antibody test • RT-PCR • Virus isolation in cell culture • detect virus by immunoperoxidase or immunofluorescence using labeled hog cholera antibody

31. Typical response to an outbreak: • Slaughter all the pigs on affected farms • Dispose of carcasses, bedding, manure, etc. • Disinfect the premises thoroughly • Designate a zone of infection and control the movement of pigs within that zone while maintaining careful surveillance of that zone and the surrounding area • Detailed epidemiological investigation to determine the source of the infection and its possible spread

32. Why prevent hog cholera? • high death rates and severe illness cause significant production losses • loss of productivity leads to an increase in the cost of food products obtained from swine • lose economically important export markets until eradication is again achieved • 1997: total value of exported U.S. pork products exceeded $1 billion • Re-eradication can be very costly • 1997 outbreak in the Netherlands cost $2 billion

33. Prevention and control: • Affected pigs must be culled and the carcasses must be buried or burned • Vaccination is used to reduce the number of outbreaks in countries where hog cholera is enzootic • Vaccination is generally prohibited in countries which are free of disease or where eradication is in progress and nearing success

34. Vaccination: • Modified live vaccines: • Lapinized Chinese strain • Japanese guinea pigs cell culture-adapted strain • French Thiverval strain • All three are innocuous for pregnant sows and piglets over 2 weeks of age • All three are considered equally effective

35. Prevention and control: • Other prophylactic measures include: • quarantining incoming pigs before introducing them to the herd • U.S. quaratines swine imported from affected countries for 90 days at a facility in Key West, FL • keeping a good pig identification and recording system • strict adherence to waste food cooking laws • structured serological surveillance of breeding sows and boars to detect subclinical infections • maintaining a strict import policy for live pigs, as well as fresh and cured pork

36. Inactivating the virus: • Temperature: • partially resistant to temperatures up to 130 degrees Fahrenheit • pH: • inactivated by a pH less than 3 or greater than 11 • Chemicals • Susceptible to ether and chloroform

37. Inactivating the virus: • Disinfectants: • 2% NaOH • 1% formalin • sodium carbonate

38. Survival of the virus: • HCV can survive some forms of meat processing: • curing • smoking • It survives well in cold temperatures • survives for months in refrigerated meat • survives for years in frozen meat

39. Recent outbreaks: • Haiti and the Dominican Republic eradicated hog cholera in the early 1980’s • Both, however, experienced outbreaks of the disease in 1997, causing pork producers to experience substantial economic losses • Belgium and the Netherlands also experienced outbreaks of hog cholera in 1997

40. Recent outbreaks: • Hog cholera was eradicated from Great Britain in 1966 • Since then there have been a few sporadic cases in 1971 and 1986 • The disease returned to Great Britain in 2000, when a total of 16 cases were confirmed in East Anglia • A total of 74,793 pigs, including those on in-contact farms, were slaughtered

41. Hog cholera in Luxembourg:

42. Hog cholera in Luxembourg: • October 2001: • wild boar was found dead in Berbourg Forest in eastern Luxembourg • boar tested positive for hog cholera • November 2001: • four additional wild boars were found dead in the Berbourg area • all four tested positive for hog cholera

43. Hog cholera in Luxembourg: • January 2002: • an additional wild boar, which was found dead in Herborn (near Berbourg), tested positive for hog cholera • February 2002: • 2 cases of hog cholera were diagnosed on a pig farm near Berbourg (breeding pigs) • All 147 pigs on the farm were destroyed • All pigs (178) within 1 km of the affected farm were also destroyed to prevent possible spread of the disease

44. Hog cholera in Luxembourg: • March 2002: • Piglets that originated from the affected farm were traced to two farms, one in northern Luxembourg, one in southern Luxembourg • These piglets, all other pigs on the two farms, and all pigs within 1 km of these two farms were destroyed for a total of 6,259 pigs • Shows that drastic action is being to prevent a full-blown outbreak of hog cholera in Luxembourg in order to prevent the immense economic and production losses that could result form such an outbreak

45. Sources: • The Gray Book - Classical Swine Fever • http://www.oie.int/eng/en_index.htm • http://aphis.usda.gov/oa/pubs/fscsf.html • http://www.oie.int.eng/maladies/fiches/A_A130.htm • http://www.defra.gov.uk/animalh/diseases/notifiable/disease/classicalsf.htm • http://www.defra.gov.uk/animalh/diseases/notifiable/statistics/classicalsf.htm

46. Thank you! Any Questions?