What if sudden deaths of piglets or adult pigs are due to SWINE FEVER disease?
- Part 2 -

Dr. Shongsir Warson Monsang / Dr. Rajkumari Mandakini *

The fully grown pig suckling her piglets :: Pix - TSE

Morbidity and Mortality: The severity of the disease varies with the viral strain. The morbidity and mortality rates are high during acute infections, and the case fatality rate can approach 100%. Morbidity and mortality are lower in subacute disease. Chronic infections are always fatal, but may affect only a few animals in a herd. The age and immune status of the animals also affects the course of disease, with lower mortality rates in adult pigs than younger animals.

Diagnosis

Clinical: Classical swine fever should be suspected in pigs with signs of septicemia and a high fever, particularly if uncooked scraps have been fed, unusual biological products have been used, or new animals have been added to the herd. It can be difficult to differentiate classical swine fever from other diseases without laboratory testing.

Laboratory tests: Classical swine fever can be diagnosed by detecting the virus, its antigens or nucleic acids in whole blood or tissue samples. Viral antigens are detected by direct immunofluorescence (FAT or FATST test) or enzyme–linked immunosorbent assays (ELISAs). The virus can also be isolated in several cell lines including PK–15 cells; it is identified by direct immunofluorescence or immunoperoxidase staining. Reverse transcriptase polymerase chain reaction (RT–PCR) tests are used in some laboratories.

Serology is used for diagnosis and surveillance. Antibodies develop after 2 to 3 weeks, and persist lifelong. For this reason, serology is most useful in herds thought to have been infected 30 or more days previously.

Samples to Collect:

Before collecting or sending any samples from animals with a suspected foreign animal disease, the proper authorities should be contacted. Samples should only be sent under secure conditions and to authorized laboratories to prevent the spread of the disease.

The method of choice for detecting herd infection early is to collect whole blood and tissues from multiple febrile or recently dead animals. Blood (collected into EDTA or heparin), or tissue samples taken at necropsy, should be taken from a few febrile animals for virus isolation, antigen detection or nucleic acid detection. Additionally, whole blood samples may be taken from a larger group of pigs.

Serum samples are particularly useful in herds that have been infected for 30 days or more. They should be taken from convalescent or recovered animals, or sows that have been in contact with suspected cases.

At necropsy, the tonsils should be submitted for virus isolation or antigen detection. Other organs to collect include the maxillary, submandibular and mesenteric lymph nodes, spleen, kidneys, and the distal part of the ileum. Samples for antigen detection and virus isolation should be refrigerated but not frozen; they should be kept cold during shipment to the laboratory.

Prevention and Control: There is no possible treatment for the disease except symptomatic treating for a short while. The affected piglets or pigs should be slaughtered, buried or incinerated to prevent further spread or outbreak.

Sanitary prophylaxis or control is the first and foremost important step in prevention and control of the disease. Effective communication between the State Department, private practitioners and pig farmers should be maintained for effective disease reporting system to work. Strict import policy should be implemented and any import of live pigs, pig semen, fresh and cured pig meat from other areas, districts or even other states should be under proper scanner and quarantined before allowing it to enter the state and admitted into the herd. Feeding of waste food to pigs should be prohibited or if unavoidable waste food should be properly sterilized. A structured serological surveillance should be targeted to breeding sows and boars.

Secondly, Medical prophylaxis consists of effective immunization with modified live virus vaccine which will help in preventing losses, in conjunction with sanitary control.

Response to outbreak

If an outbreak of the disease occurs, strict biosecurity on a farm can reduce the risk of spreading the infection from affected pigs to healthy uninfected ones. Although CSFV can be spread over long distances by animal transportation and other forms of dissemination, farms within a 500 miles radius of an infected farm have a particularly high risk of infection. Confirmed cases and contact animals should be isolated/quarantined and/or slaughtered due to this 'neighbourhood effect'.

The carcasses and bedding materials etc of infected pigs should be buried or incinerated, and the infected premises should be thoroughly cleaned and disinfected. Properly designated area of infected zone should be maintained with control of pig movements, a detailed epidemiological investigation of up-stream (tracing possible sources of infection) and down-stream (possible methods of spread) infection should be implemented with a thorough surveillance of the infected zone and the surrounding areas.

Conclusion

We all know the favorite saying, "Prevention is better than cure" but never realize its value until too late. Had our animals being vaccinated yesterday, our losses of today could have been prevented!! Now who have we to blame? Should we put the blame on the State Department for its failure to implement successful immunization program or should we blame ourselves for our ignorance to vaccinate our animals even when vaccines are available?? The big question remains!!