This year, nine confirmed cases of rat lungworm disease have surfaced in Hawaii (Maui and the Big Island), and a couple in California who recently traveled to the Aloha State came down with symptoms after they returned home from their honeymoon. Four additional cases have been suspected since the start of the year and fortunately no deaths have been reported. The Hawaii Department of Health confirmed 11 cases in 2016, and between 2007 and 2015, 42 cases were reported. Here are your questions answered.
Rat lungworm is in the family of roundworms (nematodes), named Angiostrongylus. Angiostrongylus cantonensis is a parasite that can cause neurological infections such as meningitis, and its sister species, Angiostrongylus costaricensis, can cause severe gastrointestinal illness. The specific meningitis, or inflammation of the brain, caused by A. cantonensis is an eosinophilic meningitis, where the main blood cell involved is an eosinophil, prevalent in parasitic infections as opposed to a bacterial or viral meningitis.
It's found primarily in Southeast Asia and the Pacific Basin but up until recently it's been extremely rare in the United States. In 2015 a study published in the Journal of Parasitology cited cases had been reported in Florida, Alabama, California, Louisiana, and Hawaii.
It primarily lives in rodents but the larvae can be passed to other species through rat feces. Adult nematodes live in the pulmonary arteries of rats. The females lay eggs and these, once they hatch and become first stage larvae, may migrate to the rat’s throat and then enter the GI system, eventually exiting through feces.
Symptoms include severe headache, fever, neck stiffness, visual disturbances, difficulty looking at light (photophobia), nausea, vomiting, numbness, temporary paralysis of the face and possibly coma and death.
The incubation period, on average, can be anywhere from a week to three weeks and symptoms could start within that time and possibly last for months. Neurological sequelae of the survivors can last for extended periods of time.
An individual could become exposed to A. cantonensis when one eats undercooked slugs, snails, frogs, shrimp, mollusks and contaminated fruits and vegetables. Slime from slugs may also be a source of contamination of the deadly parasite.
If a person presents with symptoms of meningitis, the cerebrospinal fluid, or fluid surrounding the brain and spinal cord is able to be sampled during a lumbar puncture. The needle entering through the back could aspirate enough of a sample for laboratory technicians to determine if the meningitis is caused by bacteria, virus or parasites, the latter of which causing a higher concentration of eosinophils to be demonstrated in the CSF fluid as well as the blood.
Currently there is no official treatment of the parasite. The parasite will die on its own but can do so in a relatively short amount of time such as days, or become latent for months. Dead worms could also cause severe neurological symptoms. Symptomatic measures of the patient are instituted to help with pain, although some have been treated with steroids and antiparasitic medications.
Make sure all raw vegetables are washed thoroughly, Handle slugs and snails with gloves and wash hands diligently. The University of Hawaii recommends boiling snails for at least 3-5 minutes prior to preparing for consumption. And keep rodents, snails and slugs away from your food and kitchen counters.
For more on prevention of Rat Lungworm infections, read: Avoid Contracting Angiostrongyliasis (Rat Lungworm Infection): Wash Fresh Fruits and Vegetables Before Eating!
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