Tuesday, October 6, 2020

Fevered Rabbits

Environmental & Science Education
Edward Hessler

Once upon a time there were four little Rabbits, and their names were--Flopsy, Mopsy, Cottontail, and Peter.--Beatrix Potter, The Tale of Peter Rabbit

Flopsy, Mopsy, Cottontail and Peter would have been surprised and sad to know that 82 years later, a deadly disease, viral naturally, would be wiping out many of their relatives, tame and wild, starting as it always seems to, in small pockets--at first somewhat controllable (but see below) and its geographic reach expanding to include wherever rabbits are found, namely all continents except Antarctica.

Rabbit Hemorrhagic Disease (RHD) is extraordinarily contagious, often showing few, if any, symptoms but once a rabbit has it there is no treatment. Suddenly a bloody nose and the outcome is almost inevitable. "[T]he mortality rate for RHD," writes Susan Orleans who has written an essay about RHD for the New Yorker, where she is a staff writer, "can reach a gloomy one hundred per cent."

I provide a glimpse--a tease, I hope, that encourages you to read the essay. Orleans is well known for her thoroughness and fine writing and if you are at all like me, i.e., knowing little about bunnies, she covers the biological and cultural territory.

RHD is caused by a lagovirus first discovered in 1984 in Jiangsu Province, China. Rabbits belong to the biological order known as Lagomorpha, hence the name since the disease is restricted, at least presently, to rabbits. The initial outbreak led to the deaths of  "some hundred and forty million rabbits...The disease soon ravaged rabbit populations elsewhere in Asia, and then in Europe, the United Kingdom, Australia, and the Middle East." The United States experienced a small number of cases which were quickly contained.

We learn that the lagovirus is a formidable adversary. This seems to be a virus specialty. The thing it can do is survive (a characteristic of a number of viruses): "on dry cloth with no host for more than a hundred days; it can withstand freezing and thawing; it can thrive in a dead rabbit for month, and on rabbit pelts, and in the wool made from Angora-rabbit fur, and in the rare rabbit that gets infected but survives." And it travels all too easily and few opportunities to move to new habitat are missed, e.g., hopping flights on birds' claws, flies' feet, coyotes' fur.

I wasn't too far into reading Orleans' essay when I thought of Steven Jay Gould's favorite title of a scientific paper. It is by paleontologist Albert E. Wood who wrote a paper in 1957 titled: "What, If Anything, Is a Rabbit?" Gould used it to introduce his essay, "What, If Anything, is a Zebra?" You can read Gould's essay here which includes Wood's answer to the question.

Rabbits are hopping contradictions. They are pets, food and more. In many ways they occupy a middle ground and this presents many challenges to their health as well as to their owners, domestic and commercial. Orleans notes that rabbits "are the third most popular pet in American, behind cats and dogs, and the most popular small pet, beating out hamsters, guinea pigs and mice." But we also eat them as well as wear them and use their fur and hides in a variety of ways. While serving as livestock, they are not officially recognized as such by the U. S. D. A. 

A vaccine has been developed, injection only with a booster each year (~ $30) so it can't be fed to rabbits, domestic or wild. But a new form of RHD, RHDV2, challenged rabbit health because the vaccine for RHDV1 was not effective. However, a vaccine has been developed for RHDV2 and sometimes both vaccines are given in one shot. But the vaccines, developed in Europe are approved only for use there. No company has a license to distribute it to many other nations.

There is an interesting side to vaccination to which many pet owners object. Rabbit livers are used in the production of the vaccine. To save a bunny, bunnies must die and knowing this is very troublesome to some pet owners. It is not one-for-one, though, as Orleans notes "that one rabbit yields several thousand vaccine doses." But this is of little comfort to many rabbit owners.

The United States, as noted, largely escaped RHDV1 invasions but this is not the case with RHDV2.  It is here as well as in Canada and is quite likely to become endemic, i.e., a native and feature of North American habitat. While having a lower mortality rate it is a better spreader than RHDV1.

Orleans' story provides examples of how one thing often leads to another, e.g., once a veterinarian reports a case it must be reported to the state veterinarian. Tthe disease is regarded as a "foreign animal disease" and must be reported. Other rabbits in contact with the infected rabbit have to be euthanized (the word used by a veterinarian was "depopulate." I assume it is thought of as softer.) And if/when wild rabbits get an RHD, there are implications for the food chain since rabbits are a widely distributed and a relied upon food source for many animals. The preferred food could then become common household pets--cats and dogs. So is it safe to take your pet bunny to the vet? Something you would do?

The U. S. D. A. has finally relented on importation of vaccines but it is limited in scope.  Orleans describes this tangle of regulations and the approval process, one that is time-consuming as well as frustrating to rabbit owners and veterinarians.

Orleans writes not only about the virus but also rabbits as part of our culture and she reminds us that "rabbits have an unusual history with viruses." The disease myxomatosis, "fatal to domestic rabbits--also caused by a virus, was "the first virus every deliberately used to eradicate a wild population of rabbits." The virus "was deployed in 1950 (Australia)...and soon killed an estimated five hundred million rabbits" which had caused an ecological disaster." Two years following its use in the field, the plan was sabotaged by a disgruntled gardener who released two infected rabbits into the wild. It then bloomed across Europe. A vaccine has been developed "and the disease was more or less brought under control. 

The disease never established a rabbits foothold in the US. 

I think when you finish the article you will agree with an observation made by New Mexico's state veternarian, Dr. Ralph Zimmerman: "'Rabbits are just a real conundrum."'                      

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