A new study of tuberculosis (TB) prevalence in captive elephants (presumably Elephas maximus) in India, reported in the Times of India, shows that approximately 15% of southern India's captive elephants test positive for TB. This is a big problem for the health and well-being elephants. The study makes me wonder (1) what TB prevalence in free-ranging elephants is, and (2) how frequently TB is transmitted from elephant to humans, and (3) what the infectious organism is (M. tuberculosis vs. M. bovis), (4) where do the infections of captive elephants come from: cattle, humans, other elephants?
The PROMED-mail moderator wrote the following on the topic of TB epidemiology in elephants. Elephants are known to be susceptible to infection by both Mycobacterium tuberculosis and M. bovis. The above article does not specify the bacteria identified in the Indian elephants. A short review on tuberculosis in elephants, by Susan Mikota, was published by ProMED-mail in July 2007 (see ProMED archive 20070702.2111). It included, among other things, the following: "While most cases in the U.S. have been due to M. tuberculosis, we may find more cases of M. bovis in Asia, where elephants often share grazing land with domestic livestock." The review, to which subscribers are referred, also covered data on the sampling and laboratory techniques applicable in elephants.
A very sad story appeared on PROMED-mail recently about a die-off of elephants around Nakabolelwa, Namibia. While still not completely investigated, the most likely cause seems to be anthrax. Bad news for elephant conservation. If anthrax infection turns out truly to be the cause of mortality, then it raises all sorts of problems. Chief among these is the possibility that people will eat meat from the carcasses, leading to almost certain infection and death if anthrax is indeed the culprit. But even if people don't eat meat from the carcasses, scavengers might and could then spread the anthrax spores around the landscape. Bad news for anthrax control. Anthrax spores in the ground remain infectious for a potentially very long time -- potentially decades. One can just imagine what a control nightmare having a checkerboard of cryptic anthrax hotspots across a landscape is.
Burning the elephant carcasses, which might be done for other types of animal infections, is impractical because it would take so much fuel in this xeric region with few woodlands and chronic shortages of cooking fuel. The PROMED moderator writes:
Dealing with elephant carcasses is difficult, as one would imagine. The prescribed technique is to pile the carcass with thorn brush to discourage scavengers while the carcass decomposes. The drop in pH will kill the vegetative cells quickly in the unopened carcass. Burning takes a significant volume of wood, and it is hard to get proper ventilation of the underside of the carcass.
Wayne Getz and his collaborators have a relatively new project to study the ecology of episodic anthrax transmission around Etosha Park, Namibia. I await the results from this project eagerly since, as far as I can tell, just about everything that comes out of his lab is great, and if not great, at least interesting.