Prosthogonimus macrorchis

Prosthogonimus macrorchis, commonly referred to as the oviduct fluke, is a frequent parasite of many species of wild birds. The parasite is most abundant in regions of the United States and Canada near the Great Lakes. It is known for causing a reduction or termination in egg production in domestic fowl.

These parasites live inside the bird's oviduct, and grow to length of 7 to 9 mm (0.28 to 0.35 in). They can cause severe infections in hens, as they damage the bird's oviduct tissues which can result in inflammation, often leading to peritonitis and/or secondary invasion with bacteria that can worsen the infection. P. macrorchis produces small, oval eggs that are less than 15x25 micrometers.

Life Cycle: P. macrorchis has a complex, indirect life cycle, which uses two intermediate hosts---the freshwater snail and dragonflies. Birds become infected by consuming both the contaminated dragonflies or snails. Once infected, the adult flukes within the bird will continually shed eggs, which pass out in their feces. These eggs contain an embryo that develops into a larval stage known as a miracidium. In this group of trematodes, the miracidium hatches after the egg is swallowed by a susceptible snail. Since flukes are less host specific than tapeworms, wild birds often introduce it to domestic poultry.

Clinical Signs: Signs of infection include
  • Bright green colored droppings, which sometimes may contain flukes
  • Pasting (soiling) of vent feathers
  • Loss of appetite
  • Restlessness
  • Increased thirst
  • Difficulty breathing
  • Walk abnormally
  • Tense and hot abdomen

Treatment: There are reports that praziquantel (5 to 10 mg/kg) and mebendazole (10 to 50 mg/kg) may be effective.


  • Order: Plagiorchiida
  • Family: Prosthogonimidae
  • Genus: Prosthogonimus


  • chickens
  • ducks
  • geese
  • sparrows
  • crows
  • wild birds

Associated Diseases