Mycobacterial Infections in Reptiles

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Mycobacterial Infections in Crocodilians

There are 23 different species of crocodilians, and Mycobacterium spp, or Mycobacterium-like lesions, have been described in at least 26% (6/23) of these animals.1, 2, 3, 4, 5 This should not, however, be surprising because these animals live in an aquatic medium that is quite capable of harboring Mycobacterium spp. It is likely that other species of crocodilians have likewise been exposed but not reported.2 Crocodilians that do develop mycobacteriosis tend to develop lesions in the

Mycobacterial Infections in Lizards

There have been at least five reports of naturally occurring mycobacteriosis cases in lizards: a water monitor (Varanus semirenex), Egyptian spiny tailed lizards (Uromastyx aegypticus), a frilled lizard (Chlamydosaurus kingi), and two bearded dragons (Pogona vitticeps) (see Table 1).10, 11, 12, 13, 14

The case of mycobacteriosis in a (presumed) wild caught water monitor was described in Australia.10 The animal did not adapt to captivity and was euthanized because of its poor condition. On

Mycobacterial Infections in Snakes

Mycobacteriosis in snakes is a rare finding, with five reports documented since the late 1920s (see Table 1).16, 17, 18, 19, 20 It is likely that mycobacteriosis is more common, but goes undiagnosed because complete necropsies are not performed.

There have been three reports of mycobacteriosis in boa constrictors (Boa constrictor), and the distribution of clinical disease was similar in all three cases even though the isolates were different in the two in which they were confirmed. In the first

Mycobacterial Infections in Chelonians

Reports of mycobacteriosis in reptiles appear to be most common in chelonians (see Table 1).12, 21, 22, 23, 24 This should not, however, come as a surprise because many of these cases are associated with an aquatic environment, where Mycobacterium spp are known to be ubiquitous. Having said that, there is at least one case report in a terrestrial species.23 Therefore, veterinarians working with these animals should not exclude mycobacteriosis as a rule-out in tortoises that are presented with

Reptiles as Models of Mycobacterial Infection

For a period of time there was a strong interest in evaluating the potential role of reptiles in the epidemiology of Mycobacterium spp important to humans. It was thought that the reptiles could serve as animal models to evaluate diagnostic tests and potential therapies for humans. While these studies were being done, they also provided some insight into the role of reptiles in the epidemiology of these pathogens.

The role of snakes in the epidemiology of M leprae was evaluated.31 Juvenile

Diagnosing Mycobacterial Infections in Reptiles

Histopathology is routinely used to diagnose mycobacteriosis in reptiles. Reptiles with mycobacteriosis tend to develop granulomatous lesions that are evident on hematoxylin–eosin stains. In many cases, these lesions are characterized by multinucleated giant cells.5 Acid-fast stains, such as the Ziehl-Neelsen method and Fite's method, are commonly used to evaluate these granulomatous lesions further and look specifically for acid-fast bacteria such as mycobacteria. Unfortunately, the

Prevalence of Mycobacterial Infections in Reptiles

Many of the case reports described in this review article suggest that mycobacteriosis is relatively uncommon in reptiles. However, as mentioned previously, it is possible that many cases go undiagnosed because of a lack of follow-through on cases by clinicians or pathologists. This may occur because of the financial constraints of an owner (eg, no necropsy performed) or limited experience and thus limited diagnostic capacity of the clinician or pathologist. To understand better the

Zoonotic Potential

It is worth mentioning that the majority of Mycobacterium spp isolated from reptiles are classified as atypical forms (eg, M chelonae). Many of these bacteria belong to the Runyon Group IV and are characterized as being resistant to antibiotics. These forms are not typically found in humans, but there are certainly case reports of disease in humans with these mycobacteria.37 Therefore, it is important that veterinarians educate their staff and clients regarding the potential zoonotic threat of

Summary

Mycobacteriosis is an important disease worldwide. Although commonly associated with higher vertebrates, including humans, this disease has been reported in only a handful of reptile cases. The limited number of reports in reptiles may be associated with a low true prevalence of disease; however, it is also possible that cases go undiagnosed because of limited follow-through by veterinary clinicians and pathologists. When present, this disease appears to present as a chronic debilitating

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  • Cited by (27)

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      In reptiles, infection is usually the result of improper handling (stress, inadequate temperature and humidity, and inadequate nutrition) [7,8,22]. Despite being an uncommon disease, it is reported to be more common in chelonians than in other reptiles [11]. Mycobacterial infections may present with a variety of clinical signs and lesions depending on the species, and the organs and systems affected [23–26].

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