By Philip R. Fischer, MD, DTM&H

Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN

Dr. Fischer reports no financial relationships relevant to this field of study.

SYNOPSIS: In addition to causing eosinophilic meningitis in tropical regions, Angiostrongylus cantonensis now has been associated with chronic, otherwise unexplained fever in children in Texas.

SOURCE: Foster CE, Nicholson EG, Chun AC, et al. Angiostrongylus cantonensis infection: A cause of fever of unknown origin in pediatric patients. Clin Infect Dis 2016 Aug. 30. pii: ciw606. [Epub ahead of print].

In the spring of 2016, two unrelated children were admitted to a hospital in Houston with prolonged fever and, after pre-admission exam and laboratory testing, no clear cause of the fever. Each was found to have infection with Angiostrongylus cantonensis.

A 19-month-old, generally healthy, former 34-week premature baby presented with a one month history of daily fevers to 103°F following outpatient care for both a presumed viral infection and otitis media (10 days of amoxicillin). She was fussy with impaired balance and decreased walking. Of note, she had never traveled outside Houston and had no history of unusual ingestion. Ataxia was noted on exam. A white blood count was elevated (22,400 per mm3) with eosinophilia (14%). There was cerebrospinal fluid pleocytosis (89 cells/mm3, 67% eosinophils). Bacterial, mycobacterial, and viral studies yielded negative results. Fever continued for an additional 12 days, after which methylprednisolone was given with rapid resolution of fever. However, fever returned following the end of a seven-day course of steroids, only to drop again with repeated steroid administration. A PCR test returned positive for Angiostrongylus cantonensis, and albendazole was given (400 mg daily for 14 days) along with tapering steroids. The symptoms resolved, and the patient was doing well two weeks after the conclusion of the treatment.

An otherwise healthy 13-month-old presented with four days of fever, malaise, and emesis. He, too, had not traveled, but he did have a history of chewing on lettuce. With pyuria, he received ceftriaxone for a presumed urinary tract infection. He remained febrile and, four days later, had a bulging fontanelle. Cerebrospinal fluid contained 1,055 white cells per mm3 (57% eosinophils). Fever persisted for 15 days despite the use of ceftriaxone. The child was improving two days later when a PCR test came back positive for A. cantonensis. He was dismissed from the hospital but returned with fever three days later. Eosinophilic meningitis was evident again (3,006 white cells per mm3 with 71% eosinophils, new nodular brain lesions on MRI). He received two weeks of prednisone, and his symptoms resolved.

COMMENTARY

Angiostrongylus cantonensis, a nematode known as a “rat lungworm,” causes eosinophilic meningitis. This illness typically occurs in Southeast Asian and Pacific areas of the world, but it is also seen in the Caribbean. The parasite lives in rats (with seafaring transport possible on ships) with an intermediate mollusk/snail host. Humans become infected by eating raw snails or by eating produce contaminated by the parasites. Within humans, the worms spread to the nervous system without causing inflammation and then die, with an eosinophilic inflammatory response occurring as worms die. The illness usually is self-limited without sequelae.

Children seem more likely than adults to have more severe illness.1 Besides having headache and other symptoms and signs of meningitis, children (more than adults) can present with fever, cranial nerve palsies, and papilledema.1 Coma and death also are reported in infected preschool-age children,2 and optic atrophy with visual loss has been seen in an adolescent patient.3

How did these two Texan children become infected? Their illnesses occurred during the spring of 2016 when there was unusual flooding in Houston — perhaps altering snail populations. While most infected adults had ingested snails, such exposures are not uniform in affected children.1 Eating contaminated produce is a known risk factor,4,5 and one of the two infected children in Houston had been known to chew on lettuce.

Travelers to Asia, the Pacific, Hawaii, and the Caribbean should be advised to avoid eating uncooked snails, and they should be careful about eating “fresh” produce that might be contaminated. A decade and a half ago, 12 of a group of 23 young American adults traveling to Jamaica developed eosinophilic meningitis; eating a Caesar salad was identified retrospectively as a risk for becoming infected.6

This report reminds us that young children are more likely to have fever and serious disease with A. cantonensis-related eosinophilic meningitis than are adults. Foreign travel is not necessarily required to become infected, and careful attention to what is eaten can be protective.

The treatment is controversial. While the typical patient has self-limited symptoms without sequelae, children seem to be at special risk of adverse outcomes. Anti-parasitic treatment (such as with albendazole) and anti-inflammatory treatment (such as with corticosteroids) seemed to facilitate resolution of symptoms in these two patients and would be warranted for other seriously ill children with eosinophilic meningitis.2

REFERENCES

  1. Sawanyawisuth K, Chindaprasirt J, Senthong V, et al. Clinical manifestations of eosinophilic meningitis due to infection with Angiostrongylus cantonensis in children. Korean J Parasitol 2013;51:735-738.
  2. Evans-Gilbert T, Lindo JF, Henry S, et al. Severe eosinophilic meningitis owing to Angiostrongylus cantonensis in young Jamaican children: Case report and literature review. Paediatr Int Child Health 2014;34:148-152.