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Investigation of chronic and persistent classical swine fever infections under field conditions and their impact on vaccine efficacy
Centro Nacional de Sanidad Agropecuaria (CENSA), OIE Collaborating Centre for Diagnosis and Risk Analysis of the Caribbean Region, La Habana 32700, Cuba.
OIE Reference Laboratory for Classical Swine Fever, IRTA-CReSA, Campus de la Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
OIE Reference Laboratory for Classical Swine Fever, IRTA-CReSA, Campus de la Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
University of Illinois, College of Veterinary Science, Department of Clinical Veterinary Medicine, Urbana, Illinois, 61802, United States.ORCID iD: 0000-0002-5717-5181
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2019 (English)In: BMC Veterinary Research, ISSN 1746-6148, E-ISSN 1746-6148, Vol. 15, no 1, article id 247Article in journal (Refereed) Published
Abstract [en]

Background: Recent studies have hypothesized that circulation of classical swine fever virus (CSFV) variants when the immunity induced by the vaccine is not sterilizing might favour viral persistence. Likewise, in addition to congenital viral persistence, CSFV has also been proven to generate postnatal viral persistence. Under experimental conditions, postnatal persistently infected pigs were unable to elicit a specific immune response to a CSFV live attenuated vaccine via the mechanism known as superinfection exclusion (SIE). Here, we study whether subclinical forms of classical swine fever (CSF) may be present in a conventional farm in an endemic country and evaluate vaccine efficacy under these types of infections in field conditions.

Results: Six litters born from CSF-vaccinated gilts were randomly chosen from a commercial Cuban farm at 33 days of age (weaning). At this time, the piglets were vaccinated with a lapinized live attenuated CSFV C-strain vaccine. Virological and immunological analyses were performed before and after vaccination. The piglets were clinically healthy at weaning; however, 82% were viraemic, and the rectal swabs in most of the remaining 18% were positive. Only five piglets from one litter showed a specific antibody response. The tonsils and rectal swabs of five sows were CSFV positive, and only one of the sows showed an antibody response. After vaccination, 98% of the piglets were unable to clear the virus and to seroconvert, and some of the piglets showed polyarthritis and wasting after 36 days post vaccination. The CSFV E2 glycoprotein sequences recovered from one pig per litter were the same. The amino acid positions 72(R), 20(L) and 195(N) of E2 were identified in silico as positions associated with adaptive advantage.

Conclusions: Circulation of chronic and persistent CSF infections was demonstrated in field conditions under a vaccination programme. Persistent infection was predominant. Here, we provide evidence that, in field conditions, subclinical infections are not detected by clinical diagnosis and, despite being infected with CSFV, the animals are vaccinated, rather than diagnosed and eliminated. These animals are refractory to vaccination, likely due to the SIE phenomenon. Improvement of vaccination strategies and diagnosis of subclinical forms of CSF is imperative for CSF eradication.

Place, publisher, year, edition, pages
BioMed Central, 2019. Vol. 15, no 1, article id 247
Keywords [en]
CSFV, Chronic infection, Persistent infection, Vaccination failures, Viral evolution
National Category
Veterinary Science
Identifiers
URN: urn:nbn:se:umu:diva-161642DOI: 10.1186/s12917-019-1982-xOAI: oai:DiVA.org:umu-161642DiVA, id: diva2:1337886
Available from: 2019-07-18 Created: 2019-07-18 Last updated: 2019-07-19Bibliographically approved

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Pérez, Lester JosueFonseca Rodriguez, OsvaldoGanges, Llilianne
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