Came across a case of few mortality in a herd of pigs. Post mortem lesions were not typical of CSF. The herd has persistent arthritis problems, Tested the tissue samples for CSFAg by ELISA and got positive result with only a moderate increase in the titre. The animals were vaccinated 6 months back with live vaccine. Is it possible that the vaccination leaves virus in spleen and kidneys which may interfere with Ag detection diagnosis?
Immunisation and epidemiological monitoring are two very complicated issues regarding pestiviruses.
The use of live vaccine, which remains the best protection, does not help to understand what is happening.
The question that arises here is what vaccine strain was used: C30, A49 ... in both cases there can be a temporary viral proliferation in lymphoid organs such as the spleen or the Payer plates. In some cases, this infection can persist for a long time and can cause mortality that can occur when the animal encounters a wild strain.
The problem lies in the difficulty to differentiate the vaccine or pathogen strains by standard ELISA or PCR.
However it is the only thing to do, because if the vaccine is at fault it is primarily because a wild strain is present in the barn so hidden: whether porcine, bovine or ovine .
Virus isolation can be done with fresh serum, and analysis of the viral strain can be conducted by studying genome but also by ELISA differentiation comparing the bovine strains, the strains sheep, and swine strains; Vaccine strains or not.
Dear colleague
Here in Cuba is used as a vaccine against classical swine fever Chinese strain, it is considered that this strain is replicated only in tonsils and for no more than 30 days, the question is What vaccine strain did you use to immunize?
No vaccine eliminates the virus, only the severe forms of the disease are controlled; however, the low virulence strains may be refractory to the vaccine and cause chronic or inapparent forms of the disease, in which case the lesions are totally non-specific.
When low-virulence strains are circulating, it may be the case that sows bear piglets that never recognize the virus as an antigen, so they do not develop an immune response, these pigs usually develop the disease after weaning or die from secondary infections.
Therefore if the forms it has are chronic or inapparent it is better to use immunohistochemical techniques, which do differentiate the vaccine virus from the field virus.
For arthritis problems I suggest you to investigate mycoplasmas, streptococci or porcine erysipelas
I hope you find the information useful
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