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A rare but potentially serious parasitic infection spread by raccoons has been found in Los Angeles. This week, LA public health officials reported that at least two residents have been infested by Baylisascaris procyonis, more plainly known as the raccoon roundworm. The worms are known to potentially cause severe neurological and eye damage.
Baylisascaris worms will usually stick to one major carnivore host, but can infect other hosts, which tend to be prey. As their name alludes to, raccoons (Procyon lotor) are the primary host of B. procyonis. The worms will reach a raccoon’s gut, mate, and lay eggs that get pooped out by the critter into the outside world (thankfully for the raccoon, the infection generally doesn’t make them sick). The eggs will then develop into infectious larvae (still encased inside a protective shell), which can take two to four weeks.
From there, the larvae will usually either be ingested by another raccoon, mature, and begin a new life cycle, or be eaten by small prey animals like rodents. Even a slight detour isn’t necessarily the end for the worms, since they can envelop themselves into hardy cysts that get buried in the animal’s tissues; should the prey later be eaten by raccoons, the worms can emerge and proceed with business as usual. But things get a little more complicated when people or our pets are unlucky enough to get infected by these worms.
On Wednesday, the Los Angeles County Department of Public Health announced that it was investigating two human cases of B. procyonis infection, both of which occurred in the South Bay area of Los Angeles County. Though the officials did not provide any details on the condition of these two victims, they noted that these infections can be a serious matter.
An illustration of the raccoon roundworm’s life cycle. © Centers for Disease Control and Prevention While raccoons are the worm’s primary hosts, dogs can play the part well enough, as they can be infected by B. procyonis larvae and successfully host adult worms that will shed eggs back into the world. But humans (and cats for that matter) are complete dead ends for the worm larvae when we get infected by them. Unfortunately for us, the larvae can still grow bigger and will sometimes migrate to our internal organs, eyes, or brain, causing serious havoc. Human cases of baylisascariasis are rare, but can be life-threatening when this happens. According to the Centers for Disease Control and Prevention, only a few dozen cases in total have been documented in the U.S., but of the 23 known cases with neurological damage, as of 2018, six have died.
A large percentage of raccoons in the Western U.S. are thought to carry B. procyonis (up to 82%, according to some estimates), and the infectious larvae can survive in the environment for years, according to the CDC. Given that raccoons thrive by living near humans, the risk of B. procyonis is certainly ever present, if small. LA officials say that younger children, people with developmental disabilities, and those with pica (an eating disorder where people eat things that are not typically considered food) are at higher risk for these infections, since they’re more likely to put contaminated fingers, soil, objects, or feces into their mouths. But people can take common sense precautions to lower their odds of catching these nasty worms.
“Our health is closely linked to the health of animals around us,” said Muntu Davis, Los Angeles County Health Officer, in a statement released by the Los Angeles County Department of Public Health. “Simple precautions, like washing your hands regularly, avoiding direct contact with wild animals and their waste, keeping pets healthy, and preventing wildlife from sheltering or living in or next to our homes or properties can help keep our neighborhoods and families safe and healthy.”
