Tuberculosis Caused by Mycobacterium tuberculosis Complex in a Captive Tapir (Tapirus terrestris)

Abstract

Background: Tuberculosis is an infectious disease caused by the Mycobacterium tuberculosis complex has already been identified in a great number of wild species. Captive animals may have a potential source for zoonoses, because is related to factors such as cohabitation, direct contact with the public, presence of biological vectors, nutritional deficiencies, absence of sanitary barriers, precautionary hygienic measures and sanitary vigilance. In Brazil, there is little information on tuberculosis in captivity animals, and little attention is given to the risks of disease transmission from humans. The aim of this study was to report the first diagnosed case of tuberculosis Tapirus terrestris in Brazilian Amazon region.

Case: One Tapirus terrestris was kept by local zoobotanic foundation in city of Marabá, Southeast of Pará state, Brazilian Amazon, and became ill. Physical examination revealed cough, sneezing, nasal outflow, dyspnea, hyperthermia and lethargy, leading to death. Necropsy demonstrated severe pulmonary alterations: thickening of the inter-alveolar septa, alveolar emphysema, and miliary nodules with dimensions up to 5 mm, which were yellowish-white, caseous, and sometimes calcified. Additionally, large areas of caseous compaction of the parenchyma, characteristic of caseous tuberculosis. Histopathological analysis revealed a process characteristic of mycobacterial infection, with alveoli filled with caseous exudate and thickened septa and fibrocytes, in addition to recently formed tubercles, some with caseous necrosis, calcifications and Langhans cells. In the Ziehl-Neelsen staining, alcohol-acid resistant bacilli were observed in the mesenteric lymph nodes. No mycobacterial growth was observed in Lowenstein-Jensen culture medium. A nested PCR followed by a sequencing assay targeting the hsp65 gene and M. tuberculosis complex member was detected. Water and M. tuberculosis H37Rv were used as negative and positive controls, respectively.

Discussion: This article reports the first case of tuberculosis in T. terrestris in Amazonia. The case of infection was caused by a complex of Mycobacterium tuberculosis, as well as reports of other studies described in wild animals. This record presented clinical and pathological similarity with the cases of a tapir and coati at the zoo of Curitiba, and non-human primates in bioteries in Belém. The disease was reported, also, in a T. indicus female in Bangkok, Thailand. In another study with two tapirs there was positivity of tuberculin test result in a Swedish zoo. In necropsy findings of tuberculosis in a Malayan tapir showed multiple white, caseous nodules spread throughout the lungs. Studies have shown that lesions can be in various organs, among them the mediastinal and mesenteric lymph nodes, liver, spleen, kidneys, ovaries, serosa, diaphragm, intestines and uterus. For exemple in a case of disseminated tuberculosis caused by M. tuberculosis in a Malayan tapir were described multiple granulomes, some coalescent, characterized by necrotic caseous centers, with some Langhans giant cells and a discrete fibrotic zone. In the present work, the results of the anatomopathological and molecular assays confirmed the clinical suspicion of respiratory infection and established the conclusive diagnosis of pulmonary tuberculosis caused by M. tuberculosis complex member. It is worth noting that tuberculosis is an important zoonotic disease affecting survival of the species, posing an extinction threat and also a public health concern.