A study in the New England Journal of Medicine (Oct. 3, 2002) reports that a snake is the source of a Salmonella organism that contaminated a platelet transfusion and infected two platelet recipients, killing one of them. The AVMA and Association of Reptilian and Amphibian Veterinarians have long been proponents of educating the public about Salmonella risks and reptile ownership, and the study is further evidence that this is key.
Doctors traced the infection to the platelet donation and discovered that both transfusions came from the same individual. Upon further investigation, they found that the donor, although appearing healthy at the time of apheresis, had asymptomatic salmonellosis, which he acquired from handling his pet boa constrictor. Strains of the blood samples taken from both patients, the platelet donor, and the snake were indistinguishable.
"Platelets are the risk because they are stored at room temperature for up to five days," said James George, MD, a professor of medicine at the University of Oklahoma who led the study. "It's the room temperature aspect which creates the risk. Bacteria can survive and multiply at room temperature."
Other blood products that are donated do not pose the same risk because they are refrigerated, in the case of red blood cells, or frozen, in the case of plasma, and these lower temperatures prevent bacteria from replicating.
Up to three percent of U.S. households have a pet reptile. The Humane Society of the United States has been a proponent of banning the animals as pets altogether, citing health threats as well as conservation and humane concerns. They have not received support from the AVMA or ARAV.
Many reptiles are colonized with Salmonella, and rates of fecal carriage can be as high as 90 percent. According to several studies, pet reptiles may account for as many as three to 18 percent of the estimated 1.4 million cases of Salmonella infections that occur annually in the United States.
Dr. Wilbur Amand, ARAV executive director, thinks the top figure is closer to eight percent. "There are many more cases of salmonellosis due to contamination of poultry and egg products than there are to cases coming from reptiles," he said.
"To me, the message (of this study) is to reemphasize the need for the (reptile) pet-owning public to maintain high sanitation standards," Dr. Amand said. "I think that the veterinarian has a role to remind clients (that), whether it is a green iguana, or a box turtle, or a boa constrictor, that any or all of them may be a carrier of the organism, and as such, they need to be careful."
Current ARAV guidelines for reducing the transmission risk of Salmonella recommend that veterinarians educate clients about the risks, the dos, and the don'ts. These guidelines were published in the July 1, 1998, issue of JAVMA and are posted online at www.arav.org.
The NEJM study also raises the question of whether physicians should routinely query donors about reptile ownership. Although this remains to be flushed out, physicians should at least recognize the potential for Salmonella risk among platelet donors and realize that a contaminated platelet transfusion may cause Salmonella sepsis. Dr. George emphasizes that he does not want reptile owners to stop donating.
"If you own a pet boa constrictor, should you never donate blood? That would be a bad message," Dr. George said. "Should you worry about it a little bit? Sure."