Baylisascaris is a roundworm genus found in a variety of wild animals. B. procyonis, or raccoon roundworm, is a particular public health concern. Like other parasites, the roundworms live inside the bodies of their hosts, producing eggs shed in feces. New hosts pick up the eggs through contamination in the natural environment and become infected themselves, spreading the eggs to new locations in an endless cycle.
Human infections with Baylisascaris are rare but potentially very serious. In organisms like raccoons, the worms stick to the intestinal tract and may cause some discomfort, nausea, and nutrient malabsorption, but no serious symptoms. With humans, there is a chance of infections spreading into the bloodstream and distributing through the internal organs, including the lungs, eyes, brain, and liver. These can cause serious medical complications, including death. Pets can also contract roundworm infections.
Irritation caused by worms just beneath the skin can be a common symptom of Baylisascaris infection. Patients may also develop neurological problems like head tilts, fatigue, difficulty seeing, and behavioral changes. Damage caused by the worms can be irreversible. Treating the infection with anthelmintic drugs can stop the infection in its tracks and prevent further worm reproduction, but will not resolve existing problems. Patients may need physical therapy and other treatments to help them recover from the infection.
Some steps to reduce the risks of Baylisascaris infection can include washing the hands carefully after working outdoors, washing wild-crafted foods before use, and limiting contact between household pets and wild animals. Keeping cats and dogs indoors and in controlled outdoor areas, for example, will reduce the chances that they will pick up eggs. Early signs of infection like intestinal discomfort and fatigue should be treated as quickly as possible to limit the chances of permanent damage.
Diagnostic tools can include examining stool samples, evaluating tissue under the microscope, and interviewing the patient to identify obvious risk factors. Patients who live in urban areas but travel to rural locations should make sure their doctors know this, as a doctor may rule out parasitic infections on the grounds that the patient couldn't have been exposed, thinking that the patient stays in the city.
Deaths associated with Baylisascaris infection are seen among already vulnerable humans, like young children with limited immune defenses who are subjected to repeat exposures. Some researchers believe the infection may be present in humans who do not exhibit other symptoms and may carry the parasites for years, illustrating that the level of severity associated with infection is highly variable.