Tuberculosis in Elephants – Wild and Captive

Elephant in Wild

Tuberculosis (TB) is a complex disease with many unknowns. Unlike human tuberculosis, which has been studied for over centuries, elephant tuberculosis has been investigated a few decades ago. Tuberculosis is more common in Asiatic Elephants (Elephas Maximus) than in African Elephants (Loxodonta africana).

TB in wild and captive elephants is caused by Mycobacterium tuberculosis, an acid-fast bacteria. M. tuberculosis possesses a zoonotic threat to the elephant keeper and the personnel involved. Habitat encroachment and competition for resources bring wild elephants into closer contact with humans, providing opportunities for zoonoses and reverse zoonoses resulting in Tuberculosis.

Mycobacterium tuberculosis is the predominant infection-causing agent in elephants although cases
caused by M. bovis have occurred. Mycobacterium szulgai, an uncommon non-tuberculous
Mycobacterium species was associated with a fatal disease in two African elephants and
Mycobacterium elephantis, a rapidly growing Mycobacterium, was isolated from a lung abscess of an
elephant that died of chronic respiratory disease.

A. Instestine Multiple – white-to-tan discrete nodules (granulomas) are protruding from the serosal surface, and less well-defined areas of pale discoloration are visible within the intestinal wall.
B. Lung – multifocal to coalescing pale tan-to-white firm nodules (granulomas) effacing much of the lung parenchyma.

Diagnosis

Application of diagnostics is crucial in Captive Elephants, as they are in close proximity to Humans and zoo personnel. Some of the diagnostics tools which are used for the diagnosis are as follows –

History of TB in the Zoo

Isolation and Identification of the etiological agent

  1. Trunk Wash (TW) Procedure –

The trunk wash procedure is an active manipulation of the elephant trunk, which can be
performed in free and protected contact systems in non-immobilized elephants after they
are conditioned for this procedure. The principle is that a sterile 0,9% saline solution (approx.
100 ml) is injected into each nostril of the trunk. The trunk has to be lifted actively by the
elephant or passively by the keeper so that the solution is running up to the base of the
trunk. The mixture of the solution and trunk mucus is collected in sterile plastic bags by
the active blowing of the elephant through its trunk. The sample is further cultured and stained for identification of mycobacterium, hence Tuberculosis.

2. Bronchoalveolar lavage (BAL) – The BAL can be performed under standing sedation. Two methods for approaching the
deeper bronchi are being practiced currently.
a. The BAL can be performed through the trunk. In addition to the sedation, a local block
anesthesia in the trunk base is required in order to get relaxation of the cartilage “valves”
present in the trunk base. This procedure requires a 5 m flexible endoscope.
b. Another approach for the BAL is through the mouth. A mouth gag is required to protect
the arm of the veterinarian who carries out the procedure. A 3.5 m long flexible
endoscope can be advanced deep into the trachea, guided by the fingertips of the
operator.

An additional sample increases the chance to detect mycobacteria originating from swallowed sputum and can also be used for culture and PCR.

“Monitoring the mohuts and their family hygiene with periodical health check up is mandatory”.

Dr. Ilayraja Selvaraj, Wildlife Veterinarian, Wildlife SOS

Immunological Tests

A positive immunological test confirms a prior contact of the animal’s immune system with
mycobacterial antigens. This may indicate either a TB-positive animal with active infection, prior
contact with TB, which leads to sterile immunity (no TB infection present), or a false-positive reaction
due to contact with closely related non-pathogenic mycobacteria.
A negative result does not exclude infection and can implicate either: a truly negative animal, a TB positive animal in which an immune response has not (yet) developed (closed TB, latency), or a TB positive animal with advanced stage(immunological non-responsiveness) (late stage clinical
TB).

  1. Comparative skin test – this “classical” test uses PPD-derived M.bovis-tuberculin and PPD-derived M.avium-tuberculin. Due to the special skin properties of elephants, the use of the comparative skin test in this species has no diagnostic value. There is some evidence, that repetitive skin tests
    can boost the immune response in TB-positive animals. To measure this booster effect a
    heparin blood sample must be taken 2-3 weeks after tuberculization (cells to be used for the
    IFN- γ, plasma for antibodies).
  2. Interferon-gamma (IFN- γ) Test – Stimulation of leucocytes with positive and negative controls, PPD-B, PPD-A, and MTB-Complex specific recombinant antigens, the in vitro production of IFN-γ is measured using an elephant IFN-γ-specific ELISA.

Post-mortem Findings – Necropsy of the dead elephant should be done, for any tubercle finding which may indicate tuberculosis.

a. Lung -Asian elephant tuberculosis. Multifocal to coalescing yellow-grey nodules, surrounded
by connective tissue and central caseous necrosis were observed during necropsy.
(b) Histopathological
examination revealed organized granulomatous inflammation with caseous necrosis, consistent with
chronic TB-lesion, hematoxylin and eosin (HE).
(c) Inflammation is characterized by numerous epithelioid
macrophages (arrow) and several multinucleated Langhans giant cells (arrowhead), HE.
(d) Alveolar
macrophage with intracellular acid-fast rods, Ziehl-Nielsen

In the unfortunate event that tuberculosis has been confirmed either during necropsy or from culture
or PCR of samples taken from a living elephant, the official authorities should be informed.

The threat of extinction is more real than many realize. And the damage done to elephants directly leads to destruction of the ecosystem.

THE GEEK VETERINARIAN

Published by TheGeekVeterinarian

Veterinarian by Profession, Blogger by Passion

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