Abstract
A 33-year-old captive female greater one-horned rhinoceros (Rhinoceros unicornis) and a 47-year-old captive female trunk-wash negative African elephant (Loxodonta africana) showed chronic-intermittent weight loss and weakness (both), a chronic sole ulcer of the left hind limb and a chronic abscess on the left shoulder (rhino), and sudden falls with final recumbency (elephant). Both animals were euthanized and necropsy revealed a multifocal chronic granulomatous pneumonia and lymphadenitis of lung-associated lymph nodes. Opportunistic ante- and postmortem laboratory tests were performed (Tables 1 and 2). Acid-fast bacteria were microscopically detected in lung granulomas and culture of the granulomas for mycobacteria was positive in both animals. However, specific real-time PCR and culture for Mycobacterium tuberculosis-complex (MTB) bacteria tested negative. Sequencing of the cultured nontuberculous mycobacteria (NTM) resulted in highest homology to Mycobacterium nebraskense for rhino samples and Mycobacterium avium ssp. hominissuis for elephant samples. Two independent microbiological laboratories reported similar results for the elephant tissue samples. Based on these findings a diagnosis of pulmonary infection with NTM was made for both animals.
Granulomatous pulmonary disease caused by NTM is rarely reported in elephants1,2 and has not been reported in rhinos. However, NTM continue to emerge as a major cause of opportunistic infection and the differentiation from MTB-complex infection is challenging. Opportunistic indirect antemortem screening TB-tests were all negative or non-reactive with the exception of one immunoassay on elephant serum (TB-ST+2 Tuberculosis Rapid Test, Lionex GmbH, D-38126 Braunschweig). Dual path platform technology (DPP® VetTB Assay, Chembio Diagnostic Systems Inc., Medford, New York 11763, USA) tests remained non-reactive over time including samples from the day of euthanasia. The present results highlight the importance of choosing appropriate diagnostic tools for the ante- and postmortem detection and differentiation of MTB complex and NTM infection in zoo animals.
Table 1. Antemortem TB testing of an African elephant and a greater one-horned rhinoceros with a pulmonary infection caused by nontuberculous mycobacteria (NTM)
|
Animal
|
Days before euthanasia
|
Test
|
Result
|
|
Elephant
|
0
|
DPP®a
|
non-reactive
|
|
Elephant
|
303
|
3-day trunk wash MTB PCR and culture
|
negative
|
|
Elephant
|
800
|
DPP®a
|
non-reactive
|
|
Elephant
|
800
|
TB-ST+2b
|
reactive
|
|
Elephant
|
943
|
DPP®a
|
non-reactive
|
|
Elephant
|
1744
|
DPP®a
|
non-reactive
|
|
Rhino
|
0
|
DPP®a
|
non-reactive
|
|
Rhino
|
185
|
DPP®a
|
non-reactive
|
a. DPP® VetTB Assay for Elephants (Chembio Diagnostic Systems Inc.).
b. TB-ST+2 Tuberculosis Rapid Test (Lionex GmbH).
Table 2. Postmortem TB testing of granulomatous tissue samples from the lung of an African elephant and a greater one-horned rhinoceros with a pulmonary infection caused by nontuberculous mycobacteria (NTM)
|
Animal
|
Test
|
Result
|
|
Elephant
|
Ziehl-Neelsen stain, histology
|
negative
|
|
Elephant
|
Ziehl-Neelsen stain, bacteriology
Auramin stain, bacteriology
|
positive (Lab 1)
positive (Lab 2)
|
|
Elephant
|
Real-time PCR MTB-complex
|
negative (Lab 1)
negative (Lab 2)
|
|
Elephant
|
Culture MTB-complex
|
negative
|
|
Elephant
|
Culture NTM
|
positive (Lab 1)
positive (Lab 2)
|
|
Elephant
|
Sequencing hsp65 gene of cultured NTM Identification
|
Mycobacterium avium ssp. hominissuis (Lab 1)
Mycobacterium avium (Lab 2)
|
|
Rhino
|
Ziehl-Neelsen, histology
|
negative
|
|
Rhino
|
Auramin, bacteriology
|
positive
|
|
Rhino
|
Real-time PCR MTB-complex
|
negative
|
|
Rhino
|
Culture MTB-complex
|
negative
|
|
Rhino
|
Culture NTM
|
positive
|
|
Rhino
|
Sequencing 16S rDNA gene of cultured NTM
|
Mycobacterium nebraskense
|
Literature Cited
1. Lacasse C, Terio K, Kinsel MJ, Farina LL, Travis DA, Greenwald R, Lyashchenko KP, Miller M, Gamble KC. Two cases of atypical mycobacteriosis caused by Mycobacterium szulgai associated with mortality in captive African elephants (Loxodonta africana). J Zoo Wildl Med. 2007:38(1):101–107.
2. Yong H., Choi GE, Byung SL, Lee BS, Whang J, Shin SJ. Disseminated infection due to Mycobacterium avium subsp. avium in an Asian elephant (Elephas maximus). J Zoo Wildl Med. 2011:42(2):743–746.