Health Care Providers Should Consider Rat Lungworm in Patients with Eosinophilic Meningitis

The US Centers for Disease Control and Prevention (CDC) has identified 12 cases of angiostrongyliasis, also known as rat lungworm, in 8 US states—all had cerebrospinal fluid (CSF) pleocytosis and eosinophilia, consistent with eosinophilic meningitis.

As such, the CDC warns in a recent Morbidity and Mortality Weekly Report, that health care providers, especially those practicing in the southern United States, should consider rat lungworm in patients with eosinophilic meningitis, especially those who have a history of having consumed raw vegetables or gastropods contaminated with larvae.

Although the majority of rat lungworm infections are reported in Asia and the Pacific Islands, the infection has also plagued Hawaii. For instance, in April 2017, Hawaii saw several cases of rat lungworm disease, particularly on the island of Maui, while just a few months later, a case of the disease was reported on Oahu for the first time in 7 years.

Autochthonous and imported cases have been reported in the continental United States as well.

By reviewing results of Angiostrongylus cantonensis polymerase chain reaction (PCR) testing performed at the CDC on 69 CSF specimens from January 2011 through January 2017, officials detected A cantonensis DNA in 34, or 49.3%, of specimens; seventeen of the 34 specimens were from within the continental United States.

Of the 17 presumptive cases, only 1 was determined by a provider to be a false-positive. The other 16 patient specimens were submitted from 8 states: California (6), Texas (4), Utah (1), Colorado (1), Arizona (1), Alabama (1), Tennessee (1), and New York (1).

Half of the patients reported having traveled to Asia, the Caribbean, or the Pacific Islands at least a year prior to initial evaluation. Six patients had no history of traveling outside of the continental United States.

According to the CDC, 6 of 11 patients reported having consumed raw vegetables; two of 12 patients reported consuming raw snails, while 2 others reported that snails had been in the environment; two of 9 patients reported eating prawns, and 1 reported consuming cooked crab. Additionally, 1 of 11 patients reported having eaten slugs, with 1 individual reporting potential exposure to slugs.

Of the 6 individuals who did not report having traveled outside of the United States, 2 reported eating raw vegetables, 3 reported potential exposure to snails or slugs, and 1 had a history of geophagia.

Health care providers confirmed rat lungworm diagnosis in 13 of the 16 cases; however, complete clinical data was only available for 12 of the individuals, according to the CDC.

Most of the patients included in the report were observed to have a subjective fever, generalized weakness, headache, and CSF pleocytosis that officials deemed to be consistent with meningitis. Additionally, many of these patients also had the presence of eosinophils in both peripheral blood and CSF, as well as hypoglycorrhachia, which, according to the CDC, is usually linked with either bacterial, fungal, or tuberculosis meningitis. All 12 patients went on to develop CSF eosinophilia.

There is no specific treatment available for rat lungworm disease. The majority of the patients evaluated in the report received systemic steroids, which effectively reduced the duration of headaches. About half of the patients were given albendazole, an antiparasitic.

Authors of the report conclude that health care providers, especially those based in the southern region of the United States, should be aware of potential rat lungworm infection in those with eosinophilic meningitis—especially if patients recently consumed raw vegetables or gastropods.