Three snakes have helped researchers decode a mysterious disease.
Scientists from the University of California, San Francisco, have identified the cause of a disease that kills a large number of pythons and boa constrictors in captivity worldwide. The cause of the disease appears to be to be a new set of viruses, known as arenaviruses.
The viruses causes body inclusion disease, which consists of micro clumps of clustered proteins forming inside the snake and leading to bacterial infections, neurological problems, anorexia and withering. “It’s a devastating disease when it gets into a collection, zoo or aquarium because it’s essentially fatal every time,” says professor Joe DeRisi, senior author of the study published in the journal mBio.
The researchers isolated two strains of the arenaviruses in snakes suffering from by body inclusion disease, but could not find any traces of them in unaffected snakes. Its identity came as a surprise because, while arenaviruses are known to affect rodents and other mammals, no one realised that they could infect reptiles.
The search began when an affected snake named Larry exhibited the signs of the disease. His owner sent a letter to DeRisi, who had found the cause of parrot disease, asking him to investigate the cause of body inclusion disease. “It satisfied all the criteria as an interesting disease,” DeRisi says, but they had to find samples from infected snakes and distinguish their genome from the viral sequences.
The first step was to sequence the boa constrictor genome, using blood samples from a boa called Balthazar who had been housed separately from other snakes in the California Academy of Sciences and tested negative for the disease. His DNA allowed the researchers to isolate the virus within the genomes of infected snakes and, once it was computationally identified, grow it in order to study it further.
The ideal way was to infect boa constrictor cells, which presented a challenge. ” There are no off the shelf boa constrictor cell lines, and so we had to make one ourselves,” DeRisi explains. He and his team used kidney cells from a red tailed boa called Juliet who had died from lymphoma to construct the cell line and found that infected cells also accumulated the protein clumps, with the antibodies revealing they were arenaviruses.
The scientists are still unsure how the disease is transmitted — they could be passed between snakes via vectors such as snake mites or rodents, a common food source for the boas, or through normal contact. “It is possible that snakes directly transmit viruses to each other,” De Risi says. “This is an important question that can no be tackled having identified this infectious agent.”