Abstract
Tuberculosis, particularly Mycobacterium bovis and M. tuberculosis, is an important health issue in zoological collections. Zoos are a particular public health concern because of the close contact between tuberculosis-susceptible animals and humans, specifically animal handlers and visitors.16 Evidence of M. tuberculosis transmission between humans and elephants, confirmed by DNA fingerprinting, has been reported.13 Between 1994 and 2001, M. tuberculosis was isolated from trunk washes of captive elephants from 11 herds in the United States.17 To date, most reported cases of tuberculosis have occurred in captive Asian elephants (Elephas maximus).14 In 1997, the National Tuberculosis Working Group for Zoo and Wildlife Species partnered with the USDA to formulate the “Guidelines for the Control of Tuberculosis in Elephants.”15 This document outlines criteria for the testing, surveillance, and treatment of tuberculosis in elephants. The guidelines recommend annual monitoring of elephants by mycobacterial culture of three direct trunk washes collected over 1 week. Isolation of Mycobacterium avium and non-tuberculous mycobacteria from elephant trunk wash samples is common, but these organisms have not been associated with clinical disease.14,18 This case report details clinical disease with fatal complications of an atypical mycobacterial infection in an African elephant (Loxodonta africana).
In September 2003, an African elephant presented with acute, severe lameness of the left rear limb with subsequent swelling of the stifle. Diagnostic procedures included aspiration cytology of the swelling, radiographs, and thermographic imaging. The exact location of the injury could not be detected, but a lesion to the stifle or coxofemoral articulation was suspected. After 13 months of treatment, including pulse therapy with a variety of nonsteroidal anti-inflammatory drugs (NSAIDs), weekly to biweekly injections of polysulfated glycosaminoglycan, and intensive foot care efforts to treat secondary pedal lesions of both rear limbs, the animal died acutely. Gross necropsy revealed granulomatous osteomyelitis with necrosis/loss of the femoral head and acetabulum and pulmonary granulomas. Both of these lesions contained acid-fast bacteria on cytology. While awaiting confirmatory culture results, quarantine procedures were established for the elephant facility and a program was established to screen all zoo personnel in close contact with the elephant or who participated in the necropsy. All personnel were tested by the Chicago Department of Public Health without documented conversion.
Mycobacterium szulgai was ultimately cultured from both coxofemoral and pulmonary lesions. Mycobacterium szulgai is an uncommon nontuberculous mycobacterium that is usually isolated from pathologic lesions in humans.21 This bacterial species was first identified in 1972.11 The lungs are the main locality for pathologic manifestation in humans and several cases have been in patients with acquired immunodeficiency syndrome.9,20,21 Infection due to M. szulgai most frequently produces thin-walled cavities in lungs resembling tuberculosis.4 Other documented sites of infection include the skin, bone, and tendon sheath (causing a carpal tunnel syndrome).2,9,10,12,19,20 Intraoperative contamination from ice water has led to M. szulgai keratitis after laser-assisted ophthalmic surgeries.6 A case of disseminated disease in a previously healthy young human has been reported.5 No evidence of human-to-human transmission of this organism has been documented and human cases are believed to originate from environmental sources.21 The natural habitat of the organism is unknown, but previous reports suggest an association of the bacteria with water of swimming pools and fish tanks.1,21 The organism has been cultured from a snail and tropical fish.1,3 No standard recommendation for the treatment of M. szulgai infection currently exists. In general, triple antibiotic therapies used in standard mycobacterial treatments are reported with a low rate of relapses and sterilization of sputum cultures within a mean of 3 months.3
Pulmonary lesions in this elephant were chronic; it was not possible to determine when initial infection occurred. Infection could have occurred in captivity or in the wild prior to captivity. Three trunk washes over the past year had been negative for mycobacterial culture. Osteomyelitis in the hip may have developed secondary to hematogenous spread from the lungs with the acute lameness resulting from a pathologic fracture associated with this infection. Alternatively, though considered less likely, a traumatic fracture of the hip could have occurred, with bacterial inoculation and secondary osteomyelitis as a result of increased blood flow to the site. The source of infection for this elephant remains unknown. Prevalence of this organism in the natural habitat or captive environment of the elephants has not been previously documented.
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