At this moment, two people lie in comas on the Big Island of Hawaii. They contracted a disease, called “eosinophilic meningitis,” by eating a salad contaminated with the nearly invisible larvae (1-2 mm) of the Rat Lungworm, Parastrongylus (=Angiostrongylus) cantonensis. Ms. Silka Strauch, 38, has been in a coma for weeks, and Graham McCumber, 24, is fighting for his life in intensive care after falling ill on December 18th. He has had significant brain damage. “It doesn’t look good,” said his uncle. A third, recovering victim, Zsolt Halda, 36, said “It felt like they were doing surgery on me and ripping out my organs” (see News Page for Gary Kubota, Star Bulletin).
As usual, the source of P. cantonensis infection is raw food (snails, crab, frogs, freshwater shrimp, and vegetables). The severity of “eosinophilic meningitis” depends on the number of larvae consumed. It is a relatively rare disease, about 3000 cases worldwide, and infection is usually mild and self-limiting, resolving within a month. However, in some cases, it can have severe neurological complications, including weakness, tingling, double vision, severe pain, blindness, coma, and even death (2-3%). Symptoms reach their peak around 2 weeks after onset, but tend to diminish after another 2 weeks. Patients who develop weakness or blindness, however, are unlikely to regain power or their sight.
A native parasite of Southeast Asia, the Rat Lungworm was first discovered in China and has rapidly spread via rats (Rattus norvegicus and R. rattus) on ships to India, Japan, Taiwan, Egypt, Ivory Coast, Madagascar, and the Pacific islands of Samoa, Fiji, and Hawaii. This parasitic nematode was found in Cuba in 1973, then in Puerto Rico (1986), in the Bahamas (1990), in the Dominican Republic (1992), in Jamaica (2002), and Haiti (2003).
The Rat Lungworm made its way by ship to New Orleans, LA in 1987. Since then, it has been reported in primates in New Orleans, and in a horse in Picayune, Mississippi (87 km from New Orleans). The parasite infected a lemur (Varencia variegata rubra) from New Iberia, Louisiana (222 km from New Orleans), and in a wood rat (Neotoma floridanus) and in 4 opossums (Didelphis virginiana) from Baton Rouge, Louisiana (124 km from New Orleans). The first human infection in the Continental U.S. was of a boy in New Orleans who swallowed a raw snail “on a dare” in 1993.
Because a great variety of gastropods serve as intermediate hosts, including Pomacea, the Rat Lungworm poses a threat to humans and domesticated animals, as well as wildlife, including birds, in the U.S. Though Pomacea can serve as intermediate hosts of “swimmer’s itch” (trematode cercaria), and intestinal flukes (Echinostoma spp.), “eosinophilic meningitis” caused by the Rat Lungworm is the most serious disease risk.
Though Rat Lungworm is not specific in either definitive or intermediate hosts, all developmental stages of Pomacea canaliculata can be readily infected with P. cantonensis. The infection rate was between 76% and 100%, with no significant difference among the groups (see Lui, October 2005, Recent Publications Page). It is logical to assume that the unabated, range expansion of exotic Pomacea in the U.S. will exacerbate the spread of the exotic Rat Lungworm to the detriment of the health of people, domestic animals, and wildlife. Posted by Jess Van Dyke
For more information on the Rat Lungworm:
Center for Disease Control:
Human Health Risks Associated with Channeled Apple Snails in the GSARP Region by John Teem, Division of Aquaculture, Florida Department of Agriculture and Juan B. Gutierrez, Biomedical Mathematics, Florida State University