When the Answer Finally is Worms
Case 1: A “Double Dog Dare”
A young Australian rugby player was sitting around with some friends in 2010 when he saw a slug crawl across a table and ate it on a dare from one of his buddies. Unfortunately, the patient developed eosinophilic meningitis and wound up in a coma for over 400 days. Ultimately, the patient developed quadriplegia and passed away in 2018 from chronic complications.
Case 2: A Honeymoon Gone Awry
Two newlyweds from California went to Hawaii for their honeymoon and returned with multiple vague symptoms. Both were ultimately diagnosed with angiostrongyliasis. While neither developed eosinophilic meningitis, both suffered from multiple complications including recurrent pneumonia and blood clots requiring hospitalization. In 2007 angiostrongyliasis became a reportable disease in Hawaii and in 2017 there was a large outbreak of 17 cases with zero deaths.
Helminth infections are a common diagnosis worldwide however, these infections are rarely considered when practitioners are evaluating American patients at home. These two cases, taken from popular media, have drawn attention to a helminth infection rarely considered: angiostrongyliasis. Commonly referred to as rodent lung worm, angiostrongyliasis is known as one of the primary causes of eosinophilic meningitis, as highlighted in case one. While typically diagnosed in Southeast Asia and the Pacific Islands, angiostrongyliasis has had a semi-recent run in the popular media that brings this infection closer to home.
While these cases may seem isolated, it is important to recognize the risk factors, symptoms, and test results that can help to diagnose rodent lung worm. Angiostrongyliasis primarily infects rats and mollusks (snails and slugs) but can be transmitted through a host of other animals including shrimp, crabs, and frogs. Human are an accidental host and cannot transmit disease. Although eating under-cooked versions of the hosts mentioned above increases the risk for acquiring angiostrongyliasis, exposure can be more sinister. Pieces of slugs can find their way into salads and other vegetable medleys or food can be contaminated slime from infected slugs. As with most tropical diseases, a food and exposure history is critical.
The incubation period for angiostrongyliasis ranges, on average, from 1-3 weeks. Once ingested, the infective larvae invade intestinal tissue, migrate to the lungs, and finally arrive in the central nervous system. Patients can present with meningitic symptoms: severe headache, neck stiffness, nausea and vomiting. There can also be neurologic changes in the extremities, ranging from parasthesias to paralysis. Any patient presenting with any of these symptoms should be evaluated for bacterial meningitis. The lumbar puncture results are essential to differentiating bacterial meningitis from eosinophilic meningitis caused by angiostrongyliasis. In eosinophilic meningitis caused by angiostrongyliasis, cerebral spinal fluid (CSF) studies will reveal an eosinophilic predominance (>10%). Other CSF findings include mildly decreased glucose and mildly elevated protein. A complete blood count (CBC) may also reveal a peripheral eosinophilia. The gold standard test for diagnosis is visualization of angiostriongylus in the CSF. However, this is a rare occurrence because angiostriongylus can adhere to the meninges. There are serologic tests for angiostrongyliasis, though these are not commercially available. Other causes of eosinophilic meningitis should be considered and may warrant evaluation with CT or MRI to assess for intracranial lesions.
At times, angiostrongyliasis can be self-limiting as the helminth life-cycle within the human is short. There is no definitive treatment for angiostrongyliasis: literature recommends analgesia, corticosteroids, and serial lumbar punctures as needed for headache symptoms. Unfortunately, there is no good data to suggest a role for antihelminthics and there is theoretical concern that antihelminthics could exacerbate inflammation and neurologic deficits through the death of the nematodes. Despite this, there are small studies from Taiwan and China where providers have used combinations of albendazole/mebendazole, dexamethasone/prednisone, and praziquantel with varying effects and no reported serious side effects. While mortality remains low over all (1.5 - 5%), when encephalitis is present mortality can be as high as 79-91%.
At the end of the day, the key to preventing infection seems to be simple--be very careful with the raw foods you consume.
Authored by Susan Owens, MD
Peer Review by Whitney bryant, MD, MPH
Posted by Grace Lagasse, MD
For author bios see our Global Health Site
Bever, Lindsey. “A Young Rugby Player Ate a Slug on a 'Mate's' Dare. Now He's Dead.” The Washington Post, WP Company, 5 Nov. 2018, www.washingtonpost.com/sports/2018/11/05/young-rugby-player-ate-slug-mates-dare-now-hes-dead/?noredirect=on&utm_term=.a7b8979881e6.
“Parasites - Angiostrongyliasis (Also Known as Angiostrongylus Infection).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 13 Nov. 2018, www.cdc.gov/parasites/angiostrongylus/gen_info/faqs.html.