Pathology and genetic findings in a rare case of Mycobacterium caprae infection in a sow

Abstract

Bovine tuberculosis, a reemerging zoonosis in diverse ecological scenarios, has been reported in the autochthonous Nebrodi black pig breed population used for meat production in Italy. During a routine abattoir inspection in 2013, 24 of 299 carcasses (8%) of Nebrodi black pigs presented tuberculosis-like lesions at pathologic examination. Mycobacterium bovis was isolated from 23 animals and M. caprae from a 3-year-old sow. The sow showed severe diffuse lesions involving the visceral organs, right coxofemoral joint, and mammary glands. Isolation of M. caprae from mammary glands is uncommon, with only one other case involving a sow reported so far; however, Mycobacteria infection of the mammary glands may be transmitted from lactating sows to piglets, contributing to the spread and maintenance of bovine tuberculosis in swine. Genotyping analysis showed M. caprae spoligotype SB0866 and profile 4,1,5,4,4,11,4,2,4,3,8,7 MIRU-VNTR (mycobacterial interspersed repetitive units-variable number of tandem repeats). The worldwide prevalence of this spoligotype is very low. The finding of severe, diffuse tuberculous lesions strongly suggests that Nebrodi black pigs are susceptible for Mycobacterium spp. and that they might act as a distributor for these microorganisms. Since natural ecosystems with multiple contacts among different livestock species and wild animals are very common in Mediterranean regions, current surveillance and eradication plans for bovine tuberculosis will need to be extended to other potential reservoir species in regions where extensive and traditional breeding systems are operated.

Molecular epidemiology of Mycobacterium tuberculosis complex strains isolated from livestock and wild animals in Italy suggests the need for a different eradication strategy for bovine tuberculosis

“…The highest prevalence observed in pigs could be associated with the observation of severe diffuse lesions in this species (Di Marco et al., ), even in the mammary gland (Amato et al., ), supporting the hypothesis that feral pigs act as a maintenance host of bTB infection and not as a spillover host (Di Marco et al., ). In addition, the detection of M. bovis DNA in swine faecal samples suggests the active excretion of the pathogen through faeces (unpublished data) highlighting the swine role in environmental contamination.…”

“…Generalized lesions involving lymph nodes and organs as well some evidences of tuberculosis affecting the intestinal wall were also detected mainly in pigs. bTB lesions were also found in mammary glands and bones (Amato et al., ). Colliquative necrosis phenomena are rare and almost observed in the mammary glands.…”

Views of veterinarians and meat inspectors concerning the practical application of visual meat inspection on domestic pigs in Finland

“…During 1998-2012 the prevalence of mycobacterium-like lesions in slaughter pigs fluctuated between < 0.1 and 0.85% (Tirkkonen 2017) and Finland is officially free of Mycobacterium bovis (Commission Decision 2003/467/ EC). Recently, Mycobacterium caprae has emerged in various European countries (Cvetnic et al 2006;Rodríguez et al 2011;Amato et al 2017) and should also be considered. As passive surveillance, Evira recommended that in cases of pronounced or generalized mycobacterium-like lesions, samples should be sent for further identification of the causative agent (Evira 2015).…”

Comparing the Metabolic Capabilities of Bacteria in the Mycobacterium tuberculosis Complex

“…Recent findings indicate that genes associated with metabolism in M. tuberculosis are under strong selective pressure in an experimental mouse model of infection [28]. This likely reflects the unique challenges associated with the facultative intracellular lifestyle of MTBC pathogens [29,30,31,32,33,34,35,36,37]. To replicate in macrophages, M. tuberculosis employs a specialized metabolism to counter nutrient limitations and the intrinsic immune pressures of macrophages [37].…”