Rabies, raccoons and renal transplantation

ByPeter Chin-Hong, MD

After spending the good part of my Friday lunch break regaling the ebullient staff writer from The Toronto Star — “Canada’s largest daily newspaper” — with stories about bites from raccoons, skunks and bats, kissing bugs that fall from thatched roofs to defecate on you, and how the West was lost to West Nile virus-bearing arthropods, I shouldn’t have been surprised that none of my quotes made the morning edition.

After all, news was breaking about rabies that had been transmitted to a Maryland man from his organ donor, and I was far from the madding geopolitical center. Geographically, I was 2,500 miles away — too far to really understand the ecology of the American Southeast, where said raccoon bite was thought to have occurred more than a year ago. And politically — I had last served on the national United Network for Organ Sharing (UNOS) Disease Transmission Advisory Committee (DTAC) months ago, and maybe the second-hand news from my DTAC friends about the event was, well — too second-hand. Journalism 101 — always get the primary data from people closest to the source.

So I went to my own sources to create my own journalism. When the kidney transplant recipient died earlier this month of rabies in Maryland, his providers and public health officials grew increasingly suspicious. The patient had no known exposures to rabies, so they turned to the 20-year-old organ donor for testing from archived biologic samples. In a classic ID whodunit moment, the donor was found to have the same strain of raccoon rabies as the recipient.

Source: CDC

The donor from Pensacola, Fla., died of a neurologic syndrome thought at that time to be from ciguatera toxin carried in saltwater fish. Digging deeper, the young donor was known to be an avid hunter and could have acquired rabies virus from a raccoon bite while a North Carolina resident. Further investigations are under way, and the other three organ recipients from the same donor are currently receiving rabies prophylaxis.

This is not the first time that rabies virus has been transmitted via organ transplantation. However, the time since transplantation was unusually long (15 months vs. the 1 month seen in the previous cases). And raccoons? I turned to Carol Glaser, MD, who, as both a trained infectious diseases specialist and a veterinarian, is my go-to person on all things rabid.

“Raccoons are uncommon causes of non-imported rabies in the US,” she said. “Most cases are due to bats because the bat bites are so tiny — like pinpricks — so they often escape attention initially. When people get bitten by a raccoon or a skunk, they usually end up in the ED, and rabies prophylaxis is given at that time.”

Could these rabies transmission events have been averted with better recognition of the donor’s fatal infectious disease? “Not so easy,” say all the experts. “We can’t do rabies testing on everyone. Neurologic syndromes are difficult,” Glaser said.

Matthew J. Kuehnert, MD, from the Office of Blood, Organ, and Other Tissue Safety at the CDC, agrees: “In general, rabies is one of many possible causes of encephalitis in donors, which may or may not be suspected at the time of death. There should be a concerted effort to know as much as possible about this unusual type of donor, as they likely are at higher risk of transmitting disease.”

He said he believes that we need more studies of “donors with encephalitis, including a standard approach to screening and testing.” We don’t often think about formal autopsies of deceased donors when snap decisions need to be made, but even a late answer could be helpful in some situations.

As my friend Michael G. Ison, MD, MS, DTAC chair emeritus, points out: “There was a significant delay between transplant and illness, so such data may have allowed intervention.”

This approach to screening and testing in potential donors has been systematized in recent years. There is now increasing attention paid to donor-derived infections, and a concerted effort made by many to thwart them, particularly the “big three”: HIV, hepatitis B and hepatitis C. There are also regional differences in screening based on geography and demographics. In Northern California, for example, we also test for Chagas disease and West Nile virus in all potential donors. But increased testing comes at a cost. Demand for organs continues to dwarf supply, and many worry that false-positive tests could result in discarded organs.

Kuehnert understands this tension. He believes that “to increase availability of organs, the criteria transplant centers use to accept organs become increasingly flexible, and that means the risk of transmissible disease, although relatively small, increases.”

John Roberts, MD, president of the United Network for Organ Sharing (UNOS) board of directors, is, in his customary fashion, to the point in his opinion. “The biggest risk to the patient is dying without a liver. Base death rate is 10% per year, but there are identifiable patients with much higher rates. The risk of transmission of infection from the donor pales in comparison,” he says.

Although we can’t — and shouldn’t — screen out all potential organ donors who have had hamsters, been spelunking in bat caves or stayed in Bolivian eco-resorts, dramatic reports as in this instance have had a positive impact on improving organ safety. Increased attention to a more streamlined chain of communication between organ procurement organizations and academic centers where the transplants are performed really target the low-hanging fruit. These include the multidrug-resistant and other bacterial infections that rarely hit the news, but are a bigger slice of the pie in influencing outcomes in organ recipients. Even in Canada.

This post is dedicated to Jennifer Henry, previous Managing Editor of INFECTIOUS DISEASE NEWS. Many thanks, Jen!