One of the best parts of being part of Science on Main is when I hear a question I've never before considered. This week's blog topic is a question that we were asked by a young scientist a few months ago, and it's one that definitely took me by surprise. Can sharks get rabies?
Jim Abernethy, National Geographic Creative |
Rabies is a viral disease that is transmitted between animals and people via bodily fluids, usually through bites but rarely through scratches. According to the World Heath Organization (WHO), up to 99% of all rabies infections come from bites from domestic dogs, especially in countries like India, where there are many stray dogs. In the Americas and some southeast Asian countries, bats are the most common carriers. Most rabies deaths today (95%) occur in Africa and Asia, and up to 40% are in children under the age of 15, who may not recognize the signs of a rabid animal. These signs include hyperactivity, a fear of water or drafts, and partial paralysis, especially around the infection site.
Rabies is almost always fatal, and was responsible for many deaths up until the late 1800s. Thankfully, Louis Pasteur and Émile Roux developed the first rabies vaccine in 1885. If a human was bitten by a rabid animal and received treatment within 10 days, that person was very likely to survive. According to WHO, over 15 million people per year receive a post-bite rabies vaccination, which saves an estimated hundreds of thousands of lives. More vaccines have been developed since and are used to prevent infection in the first place. If you have a pet dog in the United States, chances are high you've had to get this vaccine for your pet from the vet!
Dog bites are the #1 cause of rabies in humans. Picture from Anoir Chafik via Unsplash |
Sharks are not mammals, so it is not possible for them to get rabies. It is hard to imagine a shark getting bitten by a dog anyway! But there are many mammals that live in the sea. Could they get rabies?
Simply put, the answer is yes, but it is very, very rare. In the Arctic regions in northern Canada and Alaska, the Artic fox is the main rabies carrier, as one of the only canid species in the area. In 1980, rabies was detected in 12 foxes, 3 reindeer, and one ringed seal in Svalbard, an archipelago near the North Pole. The seal that had contracted rabies was found 200 m away from a blow hole, where a seal will come up for air while swimming under the thick ice. A subsequent rabies screening of hundreds of animals all came up negative. This may be the first known case of rabies in a marine mammal.
Luna, an Arctic fox at the Maryland Zoo in Baltimore. |
There is one case of rabies reported in a polar bear. In 1989, this bear was found dragging its back legs 1.2 km inland in northern Canada, and was shot dead by a group on Inuit hunters, who left the meat untouched because of the unusual circumstances of its death. Scientists tested its spinal fluid and found evidence for partial paralysis and rabies antibodies, confirming the bear was indeed rabid. No other polar bear has ever been reported to be carrying rabies.
People should always be careful and wary of all wild animals, whose behavior is unpredictable. Animals who are acting unusually should absolutely be avoided and reported to local wildlife authorities. That being said, the risk of contracting rabies is especially low, and should never stop you from enjoying the outdoor world. What are you waiting for?
Sources:
http://www.who.int/news-room/fact-sheets/detail/rabies
http://www.jwildlifedis.org/doi/abs/10.7589/0090-3558-24.2.264?code=wdas-site
https://www.researchgate.net/profile/Morten_Tryland/publication/292257698_Zoonoses_of_arctic_marine_mammals/links/5707a27108aea66081331319/Zoonoses-of-arctic-marine-mammals.pdf
http://www.jwildlifedis.org/doi/abs/10.7589/0090-3558-27.2.337?code=wdas-site
https://www.jstor.org/stable/3560403?origin=crossref&seq=1#metadata_info_tab_contents
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