Mycoplasma agassizii strain variation and distinct host antibody responses explain differences between enzyme-linked immunosorbent assays and Western blot assays

Mycoplasma agassizii in Morafka's desert tortoise (Gopherus morafkai) in Mexico

We conducted health evaluations of 69 wild and 22 captive Morafka's desert tortoises (Gopherus morafkai) in Mexico between 2005 and 2008. The wild tortoises were from 11 sites in the states of Sonora and Sinaloa, and the captive tortoises were from the state-managed Centro Ecológico de Sonora Zoo in Hermosillo and a private residence in the town of Alamos. We tested 88 tortoises for mycoplasmal upper respiratory tract disease (URTD) using enzyme-linked immunosorbent assays for specific antibody and by culture and PCR for detection of Mycoplasma agassizii and Mycoplasma testudineum. Fifteen of 22 captive tortoises had one or more positive diagnostic test results for M. agassizii whereas no wild tortoises had positive tests. Tortoises with positive tests also had significantly more moderate and severe clinical signs of mycoplasmosis on beaks and nares compared to tortoises with negative tests. Captive tortoises also exhibited significantly more clinical signs of illness than did wild tortoises, including lethargy and moderate to severe ocular signs. The severity of trauma and diseases of the shell and integument did not differ significantly among tortoises by site; however, clinical signs of moderate to severe trauma and disease were more prevalent in older tortoises. Similar to research findings for other species in the genus Gopherus in the US, we found that URTD is an important disease in captive tortoises. If they escape or are released by intention or accident to the wild, captive tortoises are likely to pose risks to healthy, naïve wild populations.

Effects of mycoplasmal upper-respiratory-tract disease on movement and thermoregulatory behavior of gopher tortoises (Gopherus polyphemus) in Georgia, USA

Abstract From 2011-12, we studied a gopher tortoise (Gopherus polyphemus) population with a historically high prevalence of antibodies to Mycoplasma agassizii to assess long-term effects of upper-respiratory-tract disease (URTD) on tortoise behavior. We radiotracked 30 adult tortoises (16 males, 14 females) from a long-term study site with the use of mark-recapture methods to determine site fidelity and to compare home-range size to that of a study in 1997. An additional 10 tortoises (six males, four females) with severe clinical signs of URTD from elsewhere in the study area were radiotracked and compared to tortoises that were asymptomatic or had only mild clinical signs. We also monitored thermoregulatory behavior of tortoises with the use of data loggers affixed to the carapace. There was no significant difference in home-range size between the asymptomatic tortoises and those with mild symptoms. Home ranges of tortoises with severe URTD were significantly larger than asymptomatic or mildly affected tortoises. Tortoises with severe clinical signs moved long distances over short periods, contradicting a hypothesis that chronically infected tortoises are less likely to emigrate. Prevalence of M. agassizii antibodies was similar among the three groups (98% overall), but prevalence of antibodies to a second pathogen associated with URTD, Mycoplasma testudineum, was lower in the asymptomatic (n=14, 7%) and mild-symptoms (n=7, 14%) groups than the severe-symptoms group (n=8, 50%). Variation in the average carapacial temperatures of tortoises with severe URTD was significantly different from carapacial temperatures of mild and asymptomatic tortoises, suggesting differences in thermoregulatory behavior of severely ill tortoises. Our 15-yr recapture data suggest that, despite high prevalence of M. agassizii, population density has not decreased over time. However, emigration, especially of tortoises with severe clinical disease, may play an important role in dispersal and persistence of pathogens.

Surveillance for upper respiratory tract disease and Mycoplasma in free-ranging gopher tortoises (Gopherus polyphemus) in Georgia, USA

Abstract Upper respiratory tract disease (URTD) in the gopher tortoise (Gopherus polyphemus) is highly contagious and has been implicated in the reduction of populations throughout the range. With the exception of a few limited studies, the prevalence of URTD in Georgia, USA tortoise populations is poorly known. We found that exposure to Mycoplasma agassizii and Mycoplasma testudineum, associated with URTD, varied geographically among 11 Georgia tortoise populations. The prevalence of antibodies to M. agassizii in individual populations was either very low (0-3%, n=7 populations) or very high (96-100%, n=4 populations), whereas there was variation in the prevalence of antibodies to M. testudineum among populations (20-61%, n=10) with only one site being negative. Five sites had tortoises with antibodies to both pathogens, and these were the only sites where we observed tortoises with clinical signs consistent with URTD. We did not find tortoises with clinical signs of URTD at sites with tortoises with antibodies only to M. testudineum, which provides evidence that this organism may be of limited pathogenicity for gopher tortoises. Collectively, these data indicate that both M. agassizii and M. testudineum are present in Georgia populations of gopher tortoises and that clinical disease is apparent in populations where both pathogens are present. Additional research is needed to better understand the role of these two pathogens, and other potential pathogens, in the overall health of tortoise populations, especially if future conservation efforts involve translocation of tortoises.

Mycoplasmosis and upper respiratory tract disease of tortoises: a review and update

Tortoise mycoplasmosis is one of the most extensively characterized infectious diseases of chelonians. A 1989 outbreak of upper respiratory tract disease (URTD) in free-ranging Agassiz's desert tortoises (Gopherus agassizii) brought together an investigative team of researchers, diagnosticians, pathologists, immunologists and clinicians from multiple institutions and agencies. Electron microscopic studies of affected tortoises revealed a microorganism in close association with the nasal mucosa that subsequently was identified as a new species, Mycoplasma agassizii. Over the next 24  years, a second causative agent, Mycoplasma testudineum, was discovered, the geographic distribution and host range of tortoise mycoplasmosis were expanded, diagnostic tests were developed and refined for antibody and pathogen detection, transmission studies confirmed the pathogenicity of the original M. agassizii isolate, clinical (and subclinical) disease and laboratory abnormalities were characterized, many extrinsic and predisposing factors were found to play a role in morbidity and mortality associated with mycoplasmal infection, and social behavior was implicated in disease transmission. The translation of scientific research into management decisions has sometimes led to undesirable outcomes, such as euthanasia of clinically healthy tortoises. In this article, we review and assess current research on tortoise mycoplasmosis, arguably the most important chronic infectious disease of wild and captive North American and European tortoises, and update the implications for management and conservation of tortoises in the wild.