What's up with H5N1 in civets in Vietnam?

Few of us had heard of palm civets before SARS. Then these small nocturnal animals came under suspicion as the source of the human SARS virus. Civet cats were a wild animal delicacy in the area where SARS broke out and it was discovered that they were infected with the same virus as humans. Did humans give it to the civet or the other way around? Or is their some third source? Bats have been discussed for SARS.

Now Vietnam is reporting, for the second time, the deaths of civets from H5N1:

Four Owston's palm civets, a catlike carnivorous species that the International Union for the Conservation of Nature lists as endangered, died between February 7 and 18 at Cuc Phuong National Park, 120 kilometres south of Hanoi, said Truong Quang Bich, director of the park.

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Bich said the civets, which were being kept in a semi-wild enclosure at the park's conservation centre, had not been fed poultry but he suspected that infected wild birds might have entered their habitat and spread the disease.

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Vietnam lists the Owston's palm civet in its Red Book of endangered species, which are illegal to trade or transport.

However, the civets' population is threatened by an illegal trade in body parts for traditional medicine. Civet meat, particularly if caught in the wild, is thought to be an aphrodisiac in some regions. (dpa)

This story claims these are the first mammals other than humans to be infected with H5N1 in Vietnam, but in 2005 three Owlston's palm civets also died of the bird flu virus. The earlier cases were described as being kept in cages, while this describes these as in a semi-wild enclosure in the same national park. It is likely the circumstances were similar. In neither case were the civets said to have been fed poultry of any kind.

So these civet cases raise two issues. The first is the infection of a particular wild mammal. Civets are found across a wide range from the Himalayas and south China to the Philippines, the Malay peninsula and Indonesia. They are said to adapt to new environments easily, living in forests and agricultural areas, often in contact with humans:

While growing up in Indonesia, I would sometimes wake up to a terrible racket in the ceiling, occasionally followed by a sickly-sweet odor reminiscent of a striped skunk. It was the musangs, or common palm civets, having some sort of spat. Once one fell through the ceiling, almost hitting my father, who had gone to investigate. Like pesky squirrels they would sometimes invade our attic.

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Weighing from 4 to 11 pounds, the palm civet's head and body length is 17 to 28 inches (43.2-71 cm), with a tail length of 16 to 26 inches (40.6-66 cm). Its ears are small and faintly pointed, as is its nose. It has a long and slender body with short legs. They have a coarse grayish to brown coat with black-tipped guard hairs over all. Three rows of black spots run along each side of its body. The hair around its eyes, cheeks and muzzle is black, with spots of white under each eye and on each side of its nose. The ears, feet and last end of its tail are also black.

Both sexes have well-developed anal scent glands looking somewhat like testes, which gives the musang its species name.

A nocturnal omnivore, the palm civet hunts alone. They are expert climbers and spend most of their lives in trees. They eat small vertebrates, insects, ripe fruits and seeds. They are very fond of palm sap, therefore their common name.

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Palm civets stake out territories which often overlap during times of adequate food supply. When spending time in one area, musangs will use the same tree to sleep in during the day. Plam civets reproduce throughout the year although it has been recorded that kittens are most often seen from October to December. Kittens are born in a litter of 2 to 5 young. Palm civets become sexually mature at 11 to 12 months. In captivity the common palm civet can live up to 22 years.

The common palm civet disperses seeds of the trees on which it feeds by eating the seed pulp and passing the seeds well away from its parent tree. Although not much is known about the palm civet, it is believed that its nocturnal habit was developed to avoid predators. (Blue Planet Times)

The Owlston's palm civet in Vietnam is not exactly the same as the common palm civet in Indonesia, but as far as I know, no one has looked for H5N1 in the common palm civet in Indonesia, either.

The second question about the Vietnam civets is this: how did they get infected? They weren't fed poultry (as least as far as anyone knows, and this was explicitly considered) nor were they in contact with poultry. It sounds like these animals were semi-confined, so the virus would have to have been brought to them somehow. Wild birds? Possibly, although there is no evidence in this case. Humans? But how? On boots or shoes? Possibly. But this virus has shown transmissibility to mammals to be difficult, and unless it has changed in that respect, doesn't seem so likely. Other civets in the same enclosure were apparently unaffected. Or is their yet another vector. Bats? It might be. Bats are now implicated as an important source in SARS, not palm civets.

This case needs to be examined carefully. It is these often seemingly anomalous instances which are the most informative.