Description
Baylisascaris procyonis is a large ascarid nematode found in the intestines of raccoons, which are the primary host. It is commonly referred to as raccoon roundworm or Baylisascaris roundworm. The parasite is common in the Northeast, Midwest, and western United States, Texas, and some areas of the Southeast. It is likely endemic throughout the range of the raccoon.
Transmission
The adult life stage of the parasite produces eggs in the intestinal tract of raccoons, and those eggs are then shed in their feces. The eggs that are shed develop into larval worms and can infect other individual raccoons. If these larval worms are eaten by another raccoon, they will develop into adult worms in the intestine of that raccoon. If eaten by other species, the larvae migrate through various organs in the body, including the central nervous system, and can cause disease.
Clinical Signs
No clinical signs or lesions are reported in raccoons. The presence of Baylisascaris procyonis in individual raccoons can be confirmed by identification of adult worms collected from raccoon intestines.
The larval stages are infectious for a variety of mammals, such as rabbits, groundhogs, squirrels, and birds. These animals are paratenic hosts, meaning that the larvae do not grow in them. These migrating larvae in mammals and birds may cause fatal neurological disease, including muscle spasms, tremors, and weakness, and/or paralysis and locomotor issues. Diagnosis in paratenic hosts is usually made by evidence of larvae and tissue damage in the brain or spinal cord.
Wildlife Management Implications
The significance of infection on a population basis in affected mammals and birds is not well known. Translocation of raccoons from infected areas to noninfected areas should be avoided.
Human Health Significance
Humans can become infected with raccoon roundworm by eating the infectious larval stage of the parasite. Human infections are rare but can be severe if the parasite invades the eye, organs, or brain. Infections are most common in children and others who are more likely to put dirt or animal waste in their mouth by mistake. Baylisacaris infection is often difficult to diagnose in humans because there are no widely available tests for it, and a diagnosis is usually made by ruling out other diseases.
You can prevent infections by removing raccoon waste quickly. The eggs passed in raccoon feces are not immediately infectious and may take two to four weeks to become infectious. Raccoon feces should be carefully removed and burned, buried, or sent to a landfill. Contaminated outdoor areas such as decks and patios should be treated with boiling water to remove contamination. As always, washing your hands after working or being outdoors is a healthy practice.
Individuals who work in taxidermy, zoos, wildlife rehabilitation facilities, or who are hunters, trappers, or wildlife handlers may be at increased risk for raccoon roundworm and should exercise caution when handling raccoon feces.