Prosthogonimus macrorchis

Prosthogonimus spp are a genus of trematodes. The four species which have been identified in birds include P. ovatus, P. macrorchis, P. pellucidus and P. cuneatus. They are collectively known as the oviduct fluke. These flatworms infect the bursa Fabricius, the oviduct and the posterior intestine of domestic and wild birds.

The genus Prosthogonimus is found worldwide and is a risk for birds living near or with access to watercourses. In 2020, P. macrorchis was reported in an egg of a chicken in North Carolina.

Appearance:Prosthogonimus spp have oval to pear-shaped, pinkish bodies that can grow to lengths of 7 to 9 mm (0.28 to 0.35 in).

Life Cycle: Prosthogonimus has a complex, indirect life cycle, which uses two intermediate hosts---the freshwater snail and dragonflies. The adult flukes live in the oviducts of the definitive host and excrete their eggs in the host's feces. These eggs contain an embryo that develops into a larval stage known as a miracidium. The freshwater snail ingests the eggs, which act as the first intermediate host. In the intestines of infected freshwater snails, the miracidium-sporocyst-daughter sporocyst-cercariae forms develop and leave the freshwater snail to infect the dragonfly nymph. The metacercariae develop in the dragonfly's body, which acts as a second intermediate host. The definitive hosts (the birds) become infected by ingesting infected dragonfly nymphs or dragonflies.

Once inside the definitive host (the bird), Prosthogonimus live in the bursa Fabricius, oviduct and cloaca. The presence of the adult fluke can cause shell-less or thin and/or deformed eggshells.

Clinical Signs: Heavy infections with Prosthogonimus can damage the oviduct, leading to egg yolk peritonitis and other reproductive issues. Resulting signs may include:
  • Passing the adult flukes in egg yolks
  • Abnormal eggs (shell-less or thin and/or deformed eggshells)
  • Bright green colored droppings, sometimes with adult flukes
  • Milk-like discharge from the cloaca
  • Pasting (soiling) of vent feathers
  • Loss of appetite
  • Restlessness
  • Increased thirst
  • Difficulty breathing
  • Abnormal gait
  • Distended abdomen

Treatment: There are no approved treatment options available for poultry. Prevention of fluke transmission to your flock is key.



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


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