Written by ANIKA CLARK
Stories of eastern equine encephalitis striking horses and humans aren’t uncommon in Southeastern Massachusetts. But the viral wrath that left a Rhode Island man still in critical condition Tuesday isn’t limited to those with heels and hooves.
“Anything that’s not native to the East Coast of the United States probably would be sensitive to it,” said Wayne Andrews, superintendent for the Bristol County Mosquito Control Project. “It’s probably been a major player in the (natural) selection process.”
In 2009, EEE wiped out 125 Maine pheasants, according to an Associated Press article from the time, and the National Wildlife Health Center reported the virus killing glossy ibis birds, pigeons, whooping cranes and white Peking ducklings. EEE has also killed emus, sporadically been found in sheep and, in 2006, hit a harbor seal off the shores of New Bedford. Andrews recalls Hungarian partridges falling victim to EEE in Southeastern Massachusetts and, although native birds don’t typically get ill from the virus, “several years ago a flock of quail imported from Asia died due to EEE,” State Public Health Veterinarian Catherine M. Brown said in an e-mail.
Meanwhile, in camelids, such as llamas and alpacas, it’s considered highly fatal, according to Daniela Bedenice of Tufts Cummings School of Veterinary Medicine in North Grafton.
Eastern equine encephalitis among East Coast camelids was first formally identified in 2005, said Bedenice, who is an assistant professor in the veterinary school’s department of clinical sciences.
“That said, we have to be a little bit careful in terms of saying that the disease wasn’t present,” she said. “I think it was more a matter of not having looked for it.”
Part of the challenge in determining EEE’s animal footprint is that, while its symptoms are often similar to those in humans and horses, the same symptoms can result from many other illnesses.
In llamas and alpacas, “it’s quite a sudden onset of, often fever, and neurological signs … consistent with what we call ‘central disease’ or ‘brain disease,'” Bedenice said. “The first thing the owner usually notices is some degree or depression or dullness in the face of a fever and incoordination.”
However, incoordination can be caused by meningeal worm, herpes, polioencephalomalacia and West Nile virus, she said, adding that the latter two can also leave animals dull and depressed and West Nile and a listeria infection can give victims a fever.
As for man’s best friend, Brown wrote, “Only a few dogs have ever been reported with the disease, so they do not appear to be very susceptible, and those that have have been young with immature immune systems.”
Robert Breen II, a veterinarian and owner of Woodland Animal Clinic in East Freetown, said he’s never treated a known, veterinary EEE case.
“We do see pets with nervous system diseases, yes, and once in awhile it crosses my mind. … More likely, though, if you took it to the max for diagnostics, you might come up with a bacterial meningitis or a neoplastic condition, meaning cancer of some sort,” he said. “We never diagnose it, and (there) would be no good way to diagnose it in a dog … or a cat.”
Neurological symptoms in dogs can be caused by everything from a form of rabies and meningitis to ingesting medicines, mushrooms or coins, according to Rachel Francis, a veterinarian and owner of the Marion Animal Hospital.
Still, she said EEE could be more common in dogs than people realize.
Francis pointed to a study conducted in Georgia from 1993 to 2005 that found more than 10 EEE-infected dogs among more than 100 that had died after showing neurologic symptoms. In order to determine that, Francis said, researchers had to culture the virus from the dogs’ brains in a process she called extremely time-consuming.
“Dogs are a hundred times more likely to get a tick than a human,” she said, “so I would say that because they’re outside more, they’re probably more likely to get a mosquito than a person, too.”
But people and animals can be exposed to the EEE virus and never develop symptoms.
“My theory is that any mammal that is exposed to the virus at least can develop a response to it, in terms of developing antibody levels,” Bedenice said. There’s “a possibility that certain species are more susceptible to disease as a consequence (of) exposure.”
So why might a person suffer a fatal bout of EEE whereas a dog or cat might not?
“Probably for the same reason why human beings don’t catch heartworm disease,” Breen said. “Your immune system overpowers it, and probably the dog and cat immune system overpowers these viruses.”