Establishment and migration pattern of Toxocara canis larvae in chickens

Migrations of Toxocara canis larvae were observed in experimentally infected chickens. Three groups of three chickens were inoculated orally with T. canis eggs. Within each group, individual chickens received either 5,000, 10,000, or 20,000 eggs. A group of infected chickens was then necropsied at either 1, 3 or 6 days post infection (dpi). The entire duodenum, spleen, liver, heart, lungs, right inner pectoral muscle, and brain were subjected to pepsin digestion for larval recovery. Larvae were predominately (>87%) recovered from the liver and lungs, and only a few larvae were seen in other organs or tissues in all chickens, with the exception of the duodenum at 1 dpi of chickens inoculated with 20,000 eggs. The percentage of total larval recovery varied widely among chickens (range: 0.4-16.7%). Similar numbers of larvae were distributed in the liver and lungs at 1 dpi. Subsequently, more larvae were found in the lungs than the liver at 3 dpi, whereas the larval distributions in the liver and lungs were reversed at 6 dpi. These observations suggest that T. canis larvae can migrate by a hepatopulmonary route in the chicken, and reinforces the possibility that chickens harboring migrating T. canis larvae may pose a zoonotic risk, especially if the liver is consumed.