The majority of elephants, including the 12 cases diagnosed at post-mortem, did not show clinical signs suggestive of TB.
Of the 34 cases, 19 have died or were euthanized. In some cases, TB was an incidental finding at necropsy and was not considered the cause of death. The zoonotic potential for the spread of TB between elephants and humans has been documented in one case. Other reports have demonstrated epizootic spread of the same strain of M. Because MDR-TB has increased in human populations and in view of the fact that some elephants are being inadequately treated typically with single-drug therapy , MDR-TB is expected to be found in captive range country elephants.
TB-infected elephants are a potential reservoir that could infect humans and wildlife, perhaps even with more virulent and novel forms of TB.
Zoonoses | Overview, Quick Facts and Resources
Elephants in the United States are not exceptional in their susceptibility to TB. In a recent study in southern India involving captive elephants in four states, 59 of the elephants had TB. The largest percent of TB affected elephants were in temples, where 16 of the 63 animals were found infected.
Of privately owned elephants, 24 had TB. Of the owned by forest departments of various state governments, 19 had TB.
Though an attempt to treat such animals was under study, experts warned that, in view of the fact that the disease is zoonotic in nature — transmitted from man to animal and vice versa — such treatment, replacing the traditionally prescribed culling of the infected animals, deserves cautious consideration. As in humans, TB in elephants — which get infected aerogenically — can be a chronic, debilitating disease.
Signs may include weakness, weight loss, exercise intolerance and coughing. Elephants may not show signs until the disease is quite advanced.
Even in the absence of clinical signs, infected elephants can shed TB bacteria and infect others. The current method used to diagnose TB in elephants is to culture samples obtained by a trunk wash procedure, similar to obtaining a sputum sample in humans. Sterile saline is placed in the trunk, the trunk is elevated, and the elephant is instructed to forcibly exhale into a collection device.
Barring cross-contamination or laboratory error, a positive culture is an accurate indication of TB disease, but false-negatives do occur. The trunk-wash sample may be from the end of the trunk instead of from deeper in the respiratory tract as intended. Because elephants use their trunks for many purposes including eating and dust bathing, contamination of the sample is common, leading sometimes to delayed or indecisive results.
Zoonoses - Animal diseases that may also affect humans
In a TB outbreak in Sweden, five elephants were affected. Of trunk wash samples collected, only seven were positive from the five elephants that were confirmed on postmortem to be infected.
The skin test a common screening test in humans has been evaluated and is not accurate in elephants. This test has reportedly been shown to be positive months to years in advance of a positive culture. A number of elephants in the United States have been treated, few of them twice.
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Pet husbandry and infection control practices related to zoonotic disease risks in Ontario, Canada
Goni, M. Public health significance of companion animals in emergence and re-emergence of bacterial zoonoses. Journal of Advanced Veterinary and Animal Research , 5 2 , Vol 5 No 2 Authors who publish with this journal agree to the following terms: Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.