Management of an outbreak of bovine tuberculosis in a mixed goat and cattle herd

Bovine tuberculosis (bTB) is a chronic contagious disease caused by Mycobacterium bovis (Mb), which have wide host range in mammalian species, man included. In Italy, bTB is subjected to eradication programs in cattle, that could lead many regions to acquire Officially bovine Tuberculosis Free status (OTF), as recently occurred to Piedmont too [Execution of Decision (EU) 2016/168 of the Commission of 5 February 2016]. Among the causes that may contribute to the persistence of bTB in cattle it is recognized the infection of other susceptible species such as goats, whose role in transmission and maintenance of infection in mixed herd is reported in many European Countries, including Italy. bTB in goats often occurs in subclinical forms, but it is associated to severe gross pathological lesions with a relative high risk of Mb environmental spread and negative impact on the eradication programs. Surveillance in goats is not mandatory, except for raw milk producers (Reg. CE n. 853/2004 del Parlamento Europeo) or outbreak occurrence suspect (D.M. n. 592 del 15/12/1995) and this leads to a lack of data on the role of goat in the epidemiology of bTB. This case report describes the diagnostic procedure adopted for the management of an outbreak of bTB in a Piedmont herd, in which both cattle and goats were reared. The diagnostic protocol included intra-vitam tests as gamma interferon tests (Bovigam((R))), Tuberculin Skin Test and indirect Elisa (IDEXX M. bovis Ab Test) and post-mortem exams as gross pathology, histopathology, microbiology and molecular tests (Spoligotyping and VNTR typing of isolated strains). On the basis of the intra-vitam test 13 cattle was declared infected and slaughtered highlighting typical lesions in 10 animals. Gamma interferon testing was extended to goats allowing to identify a positive animal that showed advanced lesions later at slaughter. Spoligotyping and VNTR typing identified the same strain type isolated from cattle (SB0134 VNTR 54534), confirming interspecific transmission. Due to high prevalence of infection, severity of observed lesions and inter-species bTB transmission, stamping out procedure was proposed and approved from Veterinary Services to extinguish the outbreak. Based on epidemiological analysis in this bTB outbreak, infection in small ruminants was fortuitous, even if the goat could have been represented a potential source of infection. The decision to extend intra-vitam tests to goats resulted conclusive for the extinction of the bTB outbreak. Therefore an epidemiological investigation conjugated to an appropriate diagnostic management represent the best ground for all actions targeted to the eradication of bTB outbreaks, especially in an area qualified as OTF.