Wednesday, July 16, 2014

Snake Fungal Disease

Credit: Julie McMahon
Snake Fungal Disease (SFD) is an emerging disease in certain populations of wild snakes in the eastern and midwestern United States. Laboratory analyses have demonstrated that the fungus Ophidiomyces ophiodiicola is consistently associated with SFD. Ophidiomyces consumes keratin, a key ingredient in snake scales. It can cause scabs, nodules, abnormal molting, ulcers and other disfiguring changes to snake skin. Mortality is 100 percent in Illinois massasauga rattlesnakes (Sistrurus catenatus) found with outward signs of infection. There are only 100 to 150 massasaugas left in Illinois, and about 15 percent of those are infected with the disease.

Researchers first took notice of Ophidiomyces in snakes in the mid-2000s. Today the fungus threatens the not only the last remaining eastern massasauga rattlesnake (Sistrurus catenatus) population in Illinois but has also been found to infect timber rattlesnakes (Crotalus horridus), mud snakes (Farancia abacura), rat snakes (various Pantherophis species), garter snakes (Thamnophis sirtalis), milk snakes (Lampropeltis triangulum), racers (Coluber constrictor), and many water snakes in several US states.

Some mycologists liken this emerging fungal disease in snakes to white-nose syndrome, another fungal disease that has killed millions of North American bats. Researchers from the University of Illinois recently published an analysis of Pseudogymnoascus destructans, the fungus implicated in white-nosed syndrome, and are now repeating their analysis on Ophidiomyces. It looks like the fungus killing snakes is very similar in its basic biology to the fungus that has killed over 6 million bats. It occurs in the soil, seems to grow on a wide variety of substances, and possesses many of the same enzymes that make the bat fungus so deadly.

A team of mycologists and herpetologists at the University of Illinois have now developed a faster and more accurate way to test for infection with Ophidiomyces ophiodiicola using quantitative polymerase chain reaction (qPCR), not only to amplify fungal DNA to identify the species present but also to measure the extent of infection. As qPCR is more than 1,000 times more sensitive than conventional methods  testing does not have to rely on tissue or blood samples anymore. A simple skin swab will do and with a properly refined protocol researchers can tell which fungal species and how many fungal spores are in a swab. Infections can be detected much earlier, intervention can start earlier and overall success of treatment or therapy could increase.

Unfortunately, preliminary studies show that the common disinfectants used are not effective and everyone handling infected snakes needs to rethink procedures to avoid the inadvertent spread of the disease.

This new qPCR test represents a big step forward in the efforts  to characterize both biological and health factors that lead to infection. It also will help the team develop new therapies to treat infections in snakes.

Here a nice video describing the entire project:

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