The helminth parasites of Irish badgers: An untold story

Abstract

The European badger (Meles meles) is a member of the Mustelid Family and Ireland?s largest terrestrial carnivore. Since the identification of badgers as wildlife reservoirs of bovine tuberculosis (bTB), extensive research has been conducted in the field of badger ecology in the ROI and badgers have become the focus of a reactive culling strategy. As badgers are a protected species in the ROI, culling has only been used as an interim control in the absence of a viable, effective vaccine. Research has now shown, in both controlled and field studies, that a low dose of liquid encapsulated Bacillus Calmette-Gu?rin (BCG) vaccine is effective at promoting a powerful immune response by triggering the T-helper 1 (Th1) arm of the adaptive immune system. A strong immune response is thereby essential for both the host?s ability to control pathogenesis of bTB and the efficacy of the BCG. One factor that has been identified as disrupting the immune response to tuberculosis infection is an underlying helminth infection. Helminths are a diverse group of large, multicellular parasitic worms. Some species have been found to live for many years - even decades - within a living host. To enable them to survive, many use highly effective mechanisms of immune subversion. This not only allows helminths to evade expulsion by the immune system but has also been shown to result in ?spill over suppression? of routine vaccinations and reduced control of mycobacterial infections. To date, only 5 studies across the badgers? Eurasian range have described the helminth community of badgers, none of which occur in the ROI. To fill this knowledge gap, a total of 289 badgers were collected from western and eastern counties and examined for the presence of helminth parasites. Infection was diagnosed using a combination of gross organ dissection and faecal egg/larval counts. Access to data from both methods of detection is rare and this offered the unique opportunity to evaluate the efficacy of coprological analysis in comparison to adult worm burden. My results show that for hookworm (Uncinaria criniformis), an individual was more likely to be diagnosed incorrectly than correctly for a helminth infection. In contrast, for lungworm (Aelurostrongylus falciformis), neither adult worm burden nor faecal larval counts were sensitive for diagnosing infection. However, when infection was present, coprological analysis was an effective indicator of intensity of infection. iv The helminth community consisted of 8 nematodes and included 4 identified to species, 1 identified to genus and 3 unknown - Aelurostrongylus falciformis; Crenosoma melesi.; Eucoleus aerophilus; Uncinaria criniformis; ?Species A?; Strongyloides spp. and two unidentifiable but morphologically distinct nematodes (nematode 1 and 2). U. criniformis infection was found to be endemic throughout the badger population and A. falciformis and Strongyloides spp. were common. Interestingly, all helminths described here belong to the Nematoda group and the majority of the known species exhibit direct life cycles. It is hoped the results from this study will serve as a baseline of badger health surveillance, as well as illuminating the helminth community, in the Irish badger, as an important comparator for other countries across the badgers? range. Additionally, as the ROI is now moving towards a vaccination-led strategy for the control of bTB, it is imperative that work is continued to investigate the effect of underlying helminth infection on both bTB pathology and vaccination efficacy, in light of the helminth endemicity reported here and the well documented immunological effects of helminth infection.