At the San Diego Zoo Desert Tortoise Conservation Center (DTCC) in Las Vegas, we take a blood sample from every tortoise that enters the facility, and we send it out for an ELISA test, which will determine if the tortoise has been exposed to Mycoplasma agassizzi, the bacteria that causes upper respiratory tract disease (URTD). Part of my job is to make sure those blood samples are prepared, cataloged, and properly packaged for shipment to the appropriate lab for testing.
Drawing blood from a tortoise is not the easiest skill to master; in fact, when I was first learning I was so afraid of harming the tortoise that it must have taken me 15 minutes of talking to the tortoise to put myself at ease! Eventually I did get the hang of drawing blood after a lot of close supervision from my colleagues here, and I am now the newest member of the staff permitted by the U.S. Fish and Wildlife Service to draw blood from desert tortoises.
An ELISA, which stands for enzyme-linked immunosorbent assay, is a test done in a molecular laboratory. It is used to detect particular antibodies in the blood; in this case, antibodies against Mycoplasma agassizzi. A positive, negative, or suspect result is based on the concentration of these antibodies (titers) present in a tortoise’s blood. When a tortoise tests positive, it means the tortoise has been exposed to the bacteria at some point in its life, but it does not necessarily mean that a tortoise is sick (this is a common misconception!). As a precaution, though, we never house tortoises that tested negative with those that tested positive, even if they show no symptoms, because there is always a chance that they ARE infected and could transmit the disease.
This is why it is very important to never release your pet desert tortoise back into the wild yourself: even if it doesn’t look sick, it could be carrying a pathogen and could infect an entire wild population of already threatened desert tortoises and put them at risk of disease and even death. The only legal means of surrendering a pet desert tortoise in Nevada is by calling our Hotline.
If you have a tortoise that doesn’t seem to be feeling well, look for symptoms that are somewhat similar to those we experience when we have a chest cold. Tortoises may have discharge from their eyes or nose, labored breathing, missing scales around the nares (nostrils), puffy eyelids and/or sunken eyes; these may be combined with lethargy and depressed behavior, much like the way we act when we don’t feel well (minus the missing scales around the nares!). Left untreated and without access to proper food, water, sunlight, and/or shelter (burrow), a desert tortoise can slowly succumb to the symptoms of URTD. If your tortoise does show upper respiratory symptoms, it is very important to get treatment from a veterinarian that specializes in desert tortoises (not just an exotics vet or a reptile vet!). And you can call our Hotline for more information as well.
Larisa Gokool is a research associate at the San Diego Zoo Desert Tortoise Conservation Center. Read her previous post, Feeding Frenzy.