Abstract

PERCEDO-ABREU, María Irian et al. Evaluation of population immunity against classical swine fever under endemic disease conditions in Cuba. Rev Salud Anim. [online]. 2022, vol.44, e05.  Epub Oct 01, 2022. ISSN 0253-570X.

Classical swine fever (CSF), or hog cholera, is a highly contagious multisystemic viral disease that is notifiable to the World Organization for Animal Health (WOAH) because of the threat of its transboundary spread. It exclusively affects domestic and wild swine, with heterogeneous clinical and lesional signs, depending on host, virus and environmental factors, which complicate its epidemiological behavior. The prolonged endemism of the disease in Cuba and the systematic application of a live vaccine, modified from the Chinese Strain (produced by LABIOFAM), have led to positive selection processes on the circulating strains, which explain their classification in a new genotype 1.4 and the appearance of moderate to low virulence strains, which have aggravated the clinical suspicion of the cases. In addition, there is the presence of persistently infected pigs (pre- and postnatally), which do not respond to vaccination and constantly shed virus into the environment. In this scenario, the serological profile of pig populations from technified and semi-technified farms, with different productive system (closed and open cycle, and both combined), systematically subjected to vaccination was characterized in one province. Antibody detection against CSFV was carried out by ELISA (Enzyme-Linked Immunoabsorbent Assay) (ELISA CSFV Ab Test IDEXX 99-43220). There was a low level of population immunity in the territory with only 52.4 % of positive animals out of 7502 pigs tested. Pigs for reproductive replacement in genetic farms showed the highest percentage (79.27 %), even with respect to their progenitors. Fattener groups showed a lower frequency of positive animals compared to breeders, and in general, it was higher in technified farms (57.97 %) compared to semi-technified farms (45.1 %). Closed cycle farms showed a lower frequency of positive animals (48.2 %) compared to open and combined cycle farms. Pigs under semi-technified production conditions showed only 42.66 % of positive animals and there were differences depending on the farms of origin. These results may be associated both to the presence of unprotected animals due to vaccine failure at vaccination (33 ±3 days of age) in the presence of high maternal antibody titers, and to a high percentage of pre- or postnatally infected pigs that are immunotolerant and do not respond to the vaccine. These conditions favor CSF endemism in that territory and require the review of the strategies used to control the disease. An analysis of these results 10 years after this research was carried out is highlighted.

Keywords : Classical swine fever; epidemiology; serological profile; immunity; endemism.

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