Sheep as a Potential Source of Bovine TB: Epidemiology, Pathology and Evaluation of Diagnostic Techniques

Abstract

Bovine tuberculosis (TB) infection is infrequently diagnosed in sheep. Most reports are from single individual cases or flock outbreaks. However, in Spain several outbreaks have been reported recently, all of which had epidemiological links with TB-infected cattle herds. A total of 897 sheep suspected of being infected with TB and belonging to 23 flocks cohabiting with TB-infected cattle herds and/or goats were tested between 2009 and 2013 in Galicia (north-western Spain), using pathological, immunological and molecular techniques. Of these, 50.44% were positive by culture, 83.23% by histopathology and 24.92%, 4.86% and 59.42% by single intradermal tuberculin test (SITT), interferon-γ and ELISA, respectively. Results suggest that in circumstances akin to those in our study, sheep may be considered as a potential source of TB. We conclude that under similar conditions, serious consideration should be given to TB testing sheep, as they may represent a potential risk to other susceptible co-habiting species. The SITT and ELISA are recommended as the simplest and most cost-effective initial approaches for the diagnosis of TB in sheep under field conditions. However, when possible, interferon-γ should be applied to increase sensitivity.

Assessment of BCG and inactivated Mycobacterium bovis vaccines in an experimental tuberculosis infection model in sheep

“…Macroscopically, lesions in all infected lambs consisted of the typical granulomatous caseous necrotizing lesions in the lung and associated LNs that are usually found in natural cases of TB [5]. The presence of large necrotic coalescing lesions found in unvaccinated control lambs indicated a fast progression of the infection to active TB, similar to what occurs in goats [21].…”

“…In Europe animal TB involves a multi-host system where domestic (cattle and goats) and wildlife (badger, wild boar and red deer) have a relevant role that varies between regions, depending on climate, habitat and husbandry factors [4]. Recent studies have shown that sheep, traditionally considered a rare host for the MTBC, can be part of the multi-species system which may maintain TB in a region, at least in mixed farms where sheep cohabit with TB-infected cattle and/or goats [5]. Given the abundance and widespread distribution of domestic sheep in Europe and elsewhere, that role may have important implications for global animal TB control, particularly since sheep are not routinely subjected to the periodic diagnostic testing within the National Programmes to eradicate bovine TB in many countries where TB is prevalent in cattle or goats [5].…”

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

“…Bovine tuberculosis is well documented in buffaloes (De Garine‐Wichatitsky et al., ; Michel, de Klerk, Gey van Pittius, Warren, & van Helden, 2007) and goats (Cadmus, Adesokan, Jenkins, & van Soolingen, ; Napp et al., ), whereas ovine TB is considered uncommon and poorly studied (Malone, Wilson, Pollock, & Skuce, ; Muñoz Mendoza et al., ; Muñoz‐Mendoza et al., ). However, a case of bTB in a sheep was previously described in Sicily, the strain was spoligotype SB0841 and had MIRU‐VNTR profile 5,4,5,3,3,10,4,4,4,3,6,5 (Marianelli et al., ).…”

Tuberculosis Detection in Paratuberculosis Vaccinated Calves: New Alternatives against Interference

“…Bovine tuberculosis (bTB) and paratuberculosis (PTB) are widespread infectious diseases that affect many domestic [1,2] and wild [3,4] species. The impact of these diseases derives from losses to the livestock industry, especially dairy cattle [5,6], from hunting and wildlife conservation as well as from their recognized (bTB) or suspected (PTB) zoonotic character.…”