Abstract
BackgroundTo obtain robust epidemiological information regarding tuberculosis (TB) in wildlife species, appropriate diagnostic methods need to be used. Wild boar (Sus scrofa) recently emerged as a major maintenance host for TB in some European countries. Nevertheless, no data is available to evaluate TB post-mortem diagnostic methods in hunter-harvested wild boar.Methodology/Principal FindingsSix different diagnostic methods for TB were evaluated in parallel in 167 hunter-harvested wild boar. Compared to bacteriological culture, estimates of sensitivity of histopathology was 77.8%, gross pathology 72.2%, PCR for the MPB70 gene 66.7%, detection of acid-fast bacilli (AFB) in tissue contact smears 55.6% and in histopathology slides 16.7% (estimated specificity was 96.7%, 100%, 100%, 94.4% and 100%, respectively). Combining gross pathology with stained smears in parallel increased estimated sensitivity to 94.4% (94.4% specificity). Four probable bacteriological culture false-negative animals were identified by Discriminant Function Analysis. Recalculating the parameters considering these animals as infected generated estimated values for sensitivity of bacteriology and histopathology of 81.8%, gross pathology 72.7%, PCR for the MPB70 gene 63.6%, detection of AFB in tissue contact smears 54.5% and in histopathology slides 13.6% (estimated specificity was 100% for gross pathology, PCR, bacteriology and detection of AFB in histopathology slides, 96.7% for histopathology and 94.4% for stained smears).Conclusions/SignificanceThese results show that surveys for TB in wild boar based exclusively on gross pathology considerably underestimate prevalence, while combination of tests in parallel much improves sensitivity and negative predictive values. This finding should thus be considered when planning future surveys and game meat inspection schemes. Although bacteriological culture is the reference test for TB diagnosis, it can generate false-negative results and this should be considered when interpreting data.
Highlights
Mycobacterium bovis (M. bovis) has the widest host range of any member of the Mycobacterium tuberculosis complex (MTC), infecting many species of wild and domestic mammals and man [1,2], and causes tuberculosis (TB).TB occurs in domestic animals worldwide, several countries successfully eradicated TB in cattle through test and slaughter programs and abattoir surveillance
Conclusions/Significance: These results show that surveys for TB in wild boar based exclusively on gross pathology considerably underestimate prevalence, while combination of tests in parallel much improves sensitivity and negative predictive values
Bacteriological culture from the 167 wild boar resulted in the isolation of M. bovis from 18 animals (P = 10.8%, CIP95% 6.9– 16.4%), Mycobacterium avium complex (MAC) from 8 and other mycobacteria not belonging to MTC or MAC from 15 animals (Table S1)
Summary
Mycobacterium bovis (M. bovis) has the widest host range of any member of the Mycobacterium tuberculosis complex (MTC), infecting many species of wild and domestic mammals and man [1,2], and causes tuberculosis (TB).TB occurs in domestic animals worldwide, several countries successfully eradicated TB in cattle through test and slaughter programs and abattoir surveillance. In some other countries (e.g. United Kingdom, USA, New Zealand) the disease is re-emerging. These later countries have in common the existence of wildlife reservoir species [1]. Several wildlife species have been reported as maintenance hosts for M. bovis, including ungulates, carnivores and marsupials. There is evidence that the wild boar is a maintenance host for M. bovis in the Iberian Peninsula [4], where wildlife TB is re-emerging [5,6]. To obtain robust epidemiological information regarding tuberculosis (TB) in wildlife species, appropriate diagnostic methods need to be used. Wild boar (Sus scrofa) recently emerged as a major maintenance host for TB in some European countries. No data is available to evaluate TB post-mortem diagnostic methods in hunter-harvested wild boar
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