Treatment of queens prior to breeding reduces the likelihood that the parasite will infect kittens. Visceral larval migrans and ocular larval migrans are diseases caused by the migration of Toxocara larvae through the tissue of people, particularly children. Although these diseases are rare, they can be quite serious, especially when they occur in young children. They can be easily avoided by preventing ingestion of Toxocara eggs in contaminated soil or on the hands. Because of their small size, they usually are not visible in the feces of infected cats.
Hookworms are long-lived and are capable of living as long as the cat.
Adult cats usually become infected by larvae that penetrate their skin or that are ingested. Once the larvae gain entrance into the host, they migrate to the lungs and then to the intestines to develop into adult worms. It is uncertain whether cats can become infected by eating rodents containing larvae in their tissues, or ingesting queen's milk that contain larvae. Severe parasitism can cause anemia due to blood loss from the intestines where the worms attach themselves. The cat's feces will appear black and tarry due to blood in the feces.