29th Annual Meeting and Symposium of the
Desert Tortoise Council, February 20-23, 2004
Abstracts

Anthropogenic Impacts on Mycoplasmosis in a Florida Gopher Tortoise Population and Increased Morbidity and Mortality Events

Mary Brown¹, Lori Wendland¹, Paul Klein¹, and Joan Berish^2
1University of Florida, Gainesville, FL
²Florida Fish Wildlife Conservation Commission, Gainesville

Anthropogenic impacts, particularly release of captive animals, has been hypothesized to play a role in the transmission dynamics of upper respiratory tract disease (URTD) in wild tortoise populations. Similarly, the role of relocation events on disease transmission has been questioned. While it is unlikely that a single explanation will account for all observed disease outbreaks, systematic investigations of selected populations may permit development and validation of general principles that are important in determining the disease transmission dynamics as well as both short and long term impacts on the populations.

The gopher tortoise population at the Cecil Field site in northeast Florida has been intensively studied since 1996, with mycoplasma surveys and health assessments performed in 1996, 1998-2001, and 2003. The study site is a state owned and managed gopher tortoise preserve that was established using funds from development mitigation fees. Signage is present informing visitors that the preserve was established specifically to protect and preserve gopher tortoises and their habitat. Originally, the property surrounding the preserve was part of a military base and thus access was limited. In 2000, the base was decommissioned and development of the surrounding areas began. Roads and other infrastructure were added, small mini-ranchette subdivisions were built directly adjacent to the preserve, and large scaled planned communities are presently under development within two to three miles of the preserve. Circa 2001/2002, well-intentioned individuals living in the area released gopher tortoises found on roadways throughout the Jacksonville, FL into the preserve. These relocations were not permitted and were unauthorized.

Prior to 2001, the percentage of animals that tested positive by ELISA for antibodies to M. agassizii was = 20%. Isolation of mycoplasmas from nasal lavages was a rare event prior to 2003; only 5 animals of 69 animals tested during this 5 year time period ever had positive PCR results. Mycoplasma testudineum (formerly known as M. cheloniae) was the only mycoplasma species identified from this site. In 2003, a dramatic change was observed. Seropositive animals increased to 75% and 58% (14/24) had nasal lavages that were positive by PCR. Importantly, the mycoplasma species present was M. agassizii. Six animals sampled in 2003 had also been sampled in previous years; all were seropositive in 2003 whereas only one tortoise had a prior positive ELISA. Five of these 6 tortoises were PCR positive in 2003.

A dramatic increase in morbidity and mortality accompanied the change in the serologic profile and shift in mycoplasmal species present in the CF population. Prior to 2003, mild nasal discharge was observed in only 2 of the 69 (3%) tortoises sampled and minimal ocular signs were observed. In 2003, 11 of 23 (48%) tortoises had nasal discharge, ranging from clear to cloudy. Ocular signs were also increased in frequency and severity. With the exception of 2000 when 4 deaths were documented, mortality events were relatively rare (=1 shell/year) in this population. In 2003, 7 recent mortality events were documented.

The results from this survey suggest that introduction of Mycoplasma agassizii into this naïve population resulted in an acute disease outbreak. Although not conclusive, the data suggests that in this population unauthorized relocation of tortoises and increased anthropogenic impact may have been triggering events. The population will be monitored intensively over the next four years to document the natural progression of the disease outbreak and its impact on population dynamics, morbidity and mortality.