HILO — Results from the first-ever prevalence study for exposure to rat lungworm disease in the United States are in, with Puna showing noticeably high exposure rates. ADVERTISING HILO — Results from the first-ever prevalence study for exposure to rat
HILO — Results from the first-ever prevalence study for exposure to rat lungworm disease in the United States are in, with Puna showing noticeably high exposure rates.
East Hawaii Island is the epicenter for rat lungworm infections, said the study’s principal investigator Susan Jarvi, a professor of pharmaceutical sciences at the University of Hawaii at Hilo College of Pharmacy. More than 90 percent of cases nationwide originate in the area.
Rat lungworm, caused by the parasitic nematode Angiostrongylus cantonensis, affects the central nervous system and the brain. Its symptoms vary widely.
“Sometimes it can be as mild as an upset stomach and flu-like symptoms, and at the extreme other end, it’s coma and then death,” Jarvi said.
The parasite is found in rats; it is passed on to snails and slugs through rat feces. People become infected after eating unwashed produce bearing slime trails from the snails and slugs.
Jarvi began researching rat lungworm disease in 2011 after attending an international rat lungworm workshop held in Honolulu. At the meeting, she met Hawaii Island resident Kay Howe, whose son, Graham McCumber, had contracted the disease and fallen into a coma. Though McCumber emerged from the coma, he suffered severe nerve damage and continues to be affected by the disease.
“I had heard about rat lungworm, but you read online (that) it’s a mild flu and self-resolving,” Jarvi said. “I met Kay and Graham and (thought), ‘wow, somebody’s got to do something.’”
Jarvi and Howe formed the Hawaii Island Rat Lungworm Working Group, which now includes about 25 people.
“A lot of our workforce is volunteer,” Jarvi said.
The prevalence study was funded by the Hawaii Community Foundation and conducted in partnership with the Puna Community Medical Center and Clinical Labs of Hawaii.
Last summer, blood samples were collected from 435 volunteers. The samples were tested via a screening called ELISA, developed by Jarvi’s lab, that detects antibodies in the blood.
Those that tested positive were then tested with a screening method developed by Praphathip Eamsobhana, a faculty member at Bangkok’s Mahidol University. Thailand is one of the 30 countries where rat lungworm disease has been found.
The testing kit developed by Eamsobhana uses the dot blot screening method and is “much more definitive,” Jarvi said, because it hones in on antibodies specifically deployed against Angiostrongylus cantonensis.
Thirty percent of the 186 people tested via dot blot came up positive, meaning they had been exposed to rat lungworm parasite at some point in their lives. And of the 126 volunteers who self-reported that they had never had rat lungworm disease, 28 percent tested positive via dot blot.
This suggests that exposure to the parasite is “higher than previously thought,” Jarvi said.
Volunteers from Puna comprised the largest group in the study. A quarter (25.3 percent) tested positive via dot blot, another noticeably high number.
Researchers have theorized that part of the reason for Puna’s rates is because of the introduction of the invasive semislug, a particularly efficient host, to the area. It could also be because more people use catchment systems in the district.
It’s thought that the larval infective stage of Angiostrongylus cantonensis can be transmitted through water.
“There are a lot of unanswered questions, and a lack of funding,” Jarvi said.
She presented the prevalence study results last month in Brisbane, Australia, at the Fourth International Rat Lungworm Disease Symposium, part of the International Congress for Tropical Medicine and Malaria. There, Jarvi met Sukwan Handali of the federal Centers for Disease Control in Atlanta. That meeting led to Handali offering to help with a follow-up study.
That study will run the same blood serum samples collected last year through a new dot-blot test, this one based on the antibodies specific to Hawaii’s nematodes, not Thailand’s. There could be differences between the two, Jarvi said, so making a Hawaii-specific test could make results more accurate.
Handali’s lab in Atlanta will be assisting with isolating the nematode proteins that cause antibodies to be produced in the first place.
The follow-up study has already been funded — once more with help from the Hawaii Community Foundation. Now, with the CDC’s help, “It’ll go a lot faster,” Jarvi said.
In addition to the follow-up study, the working group will continue its education and outreach programs in the coming year, supported in part by a grant from the Hawaii Invasive Species Council.
