(This article has been updated to correct Dr. Alfred Mina’s first name.)
In Hawai‘i, it would seem, dogs have received better treatment for rat lungworm disease than humans.
For several years, Dr. Alfred Mina, a veterinarian in Hilo, has been treating dogs presumed to have been infected with rat lungworm larvae. Last year, working with Dr. Sue Jarvi at the University of Hawai‘i-Hilo College of Pharmacy, Mina began to send blood products from dogs showing typical symptoms (i.e. weakness in the hind legs) to Jarvi’s lab, where the samples would undergo testing for the presence of rat-lungworm DNA.
“The turnaround time for PCR testing is pretty good,” Mina reported to the audience at the rat lungworm workshop, “generally between 24 and 48 hours. By the time we get the results, we usually
have already started treatment with steroids and dewormer. Also pain meds, usually a narcotic type of pain reliever. A lot of times we start to see improvement within two days.”
From February through November, Mina tested 26 dogs, 12 of which tested positive for infection, 11 tested negative, and results for three were inconclusive.
Ten of the dogs that tested positive for the disease responded successfully to treatment, Mina said. “One was euthanized due to failure to respond to treatment,” he noted, adding that the disease was far advanced when the animal was first brought in for treatment. The other dog that died was 15 years old and had terminal neoplasia in addition to the rat lungworm infection.
A question was raised about the effectiveness of monthly heartworm treatments protecting dogs against rat lungworm disease. Mina said that 10 of the 12 dogs he saw with the disease were not on regular heartworm prevention treatments. Jenee Odani, a veterinary extension agent with the University of Hawai‘i, said that of the two dogs with rat lungworm disease that she had seen on O‘ahu, one was on a “worm pill.”
In response to a follow-up email from Environment Hawai‘i, Odani said that most heartworm prevention medications can kill migrating rat lungworm larvae. “Dogs not receiving any heartworm prevention are susceptible to becoming infected with rat lungworm every day of the month,” she wrote. “Dogs that take a heartworm preventative that is cleared quickly from the bloodstream will be susceptible to RLW infection for more than 20 days in a month. On the other hand, dogs that take a heartworm preventative that main- tains high blood levels for a longer period of time may only be susceptible to infection for less than three days per month.”
She added, however, that all this “is very variable, as measured half-lives of the different medications vary considerably between dogs. But this is the likely explanation of why some dogs that take heartworm medication can still get rat lungworm and why more dogs not on heartworm prevention would get it than dogs that are.” — Patricia Tummons