Molecular identification and infection pathology of Mycobacterium spp. in captive wild animals in Pakistan

Animal tuberculosis is an infectious, chronic, granulomatous, and debilitating disease affecting animals as well as humans. However, in recent decades, there have been many endemic geographic localities where animal tuberculosis has been identified in wildlife reservoirs, limiting the eradication program in cattle. This study aimed to identify animal tuberculosis in captive zoo animals in Pakistan.

In total, 185 morbid zoo animals were brought for postmortem examination at a veterinary postmortem facility. During the macroscopic examination, these animals were thoroughly examined for the presence of suggestive gross lesions of animal tuberculosis (granulomas/tubercles), and the pattern and distribution of these lesions in different organs. The Ziehl-Neelsen (ZN) staining was performed on smears prepared from granulomatous lesions of lung tissue followed by molecular identification of M. bovis and M. tuberculosis DNA using polymerase chain reaction (PCR).

The postmortem examination revealed that 8.1% (15/185) of animals had gross tuberculosis lesions on the lungs and lymph nodes. The ZN staining of tissue smears showed 5.40% positivity while M. bovis and M. tuberculosis DNA was identified in 3.78 % and 1.1% of investigated animals, respectively.

The study showed that animal tuberculosis is prevalent among wildlife in Pakistan and it may pose serious public health concerns to the people visiting these zoos and wildlife parks.