Microbiology
A nematode aka roundworm parasite.Baylisascaris procyonis: raccoons.
Baylisascaris columnaris: skunks.
Also, B. transfuga and B. venezuelensis in bears, B. laevis in sciurids (tree squirrels, ground squirrels, chipmunks, marmots, flying squirrels, and prairie dogs ), B. devosi of gulonids, B. melis of badgers, B. potosis of kinkajou (Pubmed) and B. shroederi in giant pandas.
Epidemiologic Risks
As of the update, only Baylisascaris procyonis has caused disease in humans.
Raccoon poop. Up to 80% of raccoons have the parasite. Raccoons like to crap in the same place time after time (they call them raccoon latrines) and their stool is filled with this parasite.
People accidentally (or so one hopes) handles the egg-containing poop and then puts their hands in their mouth. Or eats an animal with the eggs. Children at risk as they tend to play in the dirt, oblivious to any risk (PubMed). I always remember the time my son ate a slug before I could stop him: from the dirt to the stomach in the blink of an eye.
B. procyonis roundworms are most prevalent in the midwestern, northeastern, and Pacific western states and in the mountainous regions of Virginia, Kentucky, and West Virginia.
It has also been found in pet Kinkajous (CDC) and there are a variety of Baylisascaris, each with their own hosts.
About 7% of wildlife rehabilitators (who knew wildlife had drug and alcohol problems; probably why they are called wildlife) are seropositive suggesting subclinical infection (Pubmed)(PubMed).
Syndromes
Once consumed, the worms spread hematogenously to every organ, with a predilection for the CNS and the eye.
Acute meningitis/encephalitis, often eosinophilic. Rare but fatal.
Also, consider Toxocara spp. and Angiostrongylus spp in the differential diagnosis.
Visceral larva migrans and occular larva migrans.
No serology; look for the organism in the CSF or as the CDC notes "eye examinations may reveal a migrating larva or lesions and are often the most significant clue to infection..." Eeewwww.
Treatment
Albendazole ASAP 25-50 mg/kg per day po for 10 – 20 days and dexamethasone for months.
Notes
The eggs are very resistant to death: "Loss of viability resulted when eggs were heated to 62 C or desiccated for 7 months but not when frozen at 15 C for 6 months (PubMed)." So don't eat your raccoon rare.
Common in pet skunks, so be sure to have your skunks dewormed.
Last update: 01/23/20