Testing Eurasian wild boar piglets for serum antibodies against Mycobacterium bovis

Abstract

Animal tuberculosis (TB) caused by infection with Mycobacterium bovis and closely related members of the M. tuberculosis complex (MTC), is often reported in the Eurasian wild boar (Sus scrofa). Tests detecting antibodies against MTC antigens are valuable tools for TB monitoring and control in suids. However, only limited knowledge exists on serology test performance in 2-6 month-old piglets. In this age-class, recent infections might cause lower antibody levels and lower test sensitivity. We examined 126 wild boar piglets from a TB-endemic site using 6 antibody detection tests in order to assess test performance. Bacterial culture (n=53) yielded a M. bovis infection prevalence of 33.9%, while serum antibody prevalence estimated by different tests ranged from 19% to 38%, reaching sensitivities between 15.4% and 46.2% for plate ELISAs and between 61.5% and 69.2% for rapid immunochromatographic tests based on dual path platform (DPP) technology. The Cohen kappa coefficient of agreement between DPP WTB (Wildlife TB) assay and culture results was moderate (0.45) and all other serological tests used had poor to fair agreements. This survey revealed the ability of several tests for detecting serum antibodies against the MTC antigens in 2-6 month-old naturally infected wild boar piglets. The best performance was demonstrated for DPP tests. The results confirmed our initial hypothesis of a lower sensitivity of serology for detecting M. bovis-infected piglets, as compared to older wild boar. Certain tests, notably the rapid animal-side tests, can contribute to TB control strategies by enabling the setup of test and cull schemes or improving pre-movement testing. However, sub-optimal test performance in piglets as compared to that in older wild boar should be taken into account.

Tuberculosis-Associated Death among Adult Wild Boars, Spain, 2009–2014

“…In Spain, the Eurasian wild boar is regarded as the key wildlife MTC maintenance host; its infection prevalence rates are >50% in Mediterranean areas that have dense wild boar populations ( 6 ). Up to one third of wild boar piglets might become infected during their first 6 months of life ( 7 ). In half of MTC-infected wild boars, generalized lesions develop that affect the lungs, particularly in juveniles (12–24 months of age).…”

A lateral flow assay for the rapid diagnosis of Mycobacterium bovis infection in wild boar

“…Negative samples of this group of juvenile animals should be assayed. Furthermore, the difference of sensitivity found among animals of different ages when INgezim tests were used could be explained due to the fact that in adult wild boar, antibody production is closely related to infection status/lesion severity, whereas lesions can appear in juvenile wild boar exposed to a great burden of M. bovis , but, due to their younger age, the production of MPB83/70 specific antibodies has not reached a detectable level yet; as already shown by Che' Amat et al, .…”

“…LFAs have been described to analyse elephant, cervid and non‐human primate sera, with sensitivities ranging from 79% in elk to 100% in elephants (Lyashchenko, Gortazar, Miller, & Waters, ; Lyashchenko et al, ). This LFA has also been tested in wild boar serum, providing high specificity and sensitivity (Che' Amat et al, ), but with the limitation that it only detects IgGs (Boadella et al, ).…”

Seroprevalence ofMycobacterium bovisinfection in warthogs (Phacochoerus africanus) in bovine tuberculosis-endemic regions of South Africa

“…Nevertheless, this observation has been reported in wild boar and may reflect the time dependence of this chronic disease (Santos et al., ). However, other studies in wild boar have shown the opposite outcome with juveniles or sub‐adults being at higher risk or no difference in infection rates between age groups (Boadella et al., ; Che’ Amat et al., ). More research is needed in our specific case.…”

“…Serological assays have been shown to be an accurate tool for assessing bTB prevalence in European wild boar (Aurtenetxe et al., ; Boadella et al., ; Che’ Amat et al., ). Our results demonstrate that the indirect PPD ELISA is a useful tool to estimate prevalence and evaluate epidemiologic risk factors for M. bovis infection in warthogs in Africa.…”