New Test for Cryptosporidiosis, an Incurable Disease of Snakes and Lizards

A decade or so ago, Cryptosporidiosis became recognized as a major concern in captive snake and lizard collections.  Caused by a one-celled parasite known as Cryptosporidium varanii, the disease remains incurable to this day.  At the Bronx Zoo, where I worked at the time, tests showed that many snakes already in our collection, along with wild and pet reptiles, might be harboring Cryptosporidium.  But diagnosis was difficult and errors were common, resulting in the institution of expensive and time-consuming isolation protocols for new and sick animals.  So I was happy to learn of a newly devised test that ensures early, accurate diagnosis of Cryptosporidium…it will surely prove useful to pet keepers and zoos alike.

Crypto and the Pet Trade

A number of factors render Cryptosporidiosis as a major concern, including the popularity of reptile pets and the fact that the parasite can be transferred to people.  While not often of major concern to healthy adults, Crypto, as it came to be known, is a danger to immune-compromised individuals (please see article below).  A recent survey of 672 pets revealed that 1 in 6 of the Corn Snakes and 1 in 12 of the Leopard Geckos tested harbored Crypto in one form or another. 

Crypto is the most common cause of a Leopard Gecko ailment popularly known as “Stick Tail Disease”.  The parasite dwells in the small intestine, where it prevents proper absorption of food; various bacteria to take hold as well, due perhaps to damage inflicted on the intestinal walls.  Loose stools and weakness follow, and the gecko’s thick tail (which stores fat) wastes away to a mere “stick”.  Crypto has caused similar problems in Gila monsters, monitors, chameleons and other species.

Crypto is passed in the feces (in a form known as an oocyst) and can remain alive for years until a host is found.  Oocysts are difficult to kill other than by steam, undiluted ammonia and certain disinfectants not generally available to hobbyists.

Crypto in Zoo Animals and Wild Populations

Declining populations of many snakes and lizards makes zoo-based breeding programs all-the-more vital.  However, Crypto is incurable; the many zoo animals that now harbor it must be isolated, and cannot be bred as the young will likely be infected as well.

The Importance of the New Test

The first Crypto tests, based on fecal samples, were unreliable because the parasite often appeared sporadically, or in minute populations, and so was easy to miss.  Also, related parasites infect the foods eaten by snakes and lizards, and distinguishing between the species of Cryptosporidium present was nearly impossible.

Researchers at the University of Veterinary Medicine in Vienna have recently devised a DNA-based test that quickly and accurately reveals the presence of Cryptosporidium parasites (please see article below).  The test also allows one to determine whether the parasite is present in the snake or lizard, or entered via the animal’s food.

Caring for Crypto-Positive Reptiles

Early detection is important because there are medications, such as Paromomycin, that can keep Crypto populations low enough to allow the infected reptile to survive.  However, treatment is only effective if instituted within a certain time frame.

Crypto-positive reptiles cannot be cured at this time, and will require lifelong treatment and special care.  Dr. Kevin Wright of the Arizona Exotic Animal Hospital  has written an excellent paper on this subject (please see below); please read it to learn more about caring for such animals and preventing Crypto transmission.

 

 

Further Reading

Crypto in Leopard Geckos (Arizona Exotic Animal Hospital)

Crypto/Microsporidium in Bearded Dragons

Abstract of article describing the recent Crypto study

Crypto infections in humans