Duck prosthogonimiasis is a type of parasitic helminth disease in ducks.

Duck prosthogonimus is a parasite that lives in the bile ducts or gallbladder of the duck liver. It mainly affects ducks over one month of age, and both the infection rate and infection intensity are very high. Death often occurs due to blockage of the gallbladder and bile ducts by the worms, making it one of the trematode diseases currently causing relatively great harm to ducks. There are two species of prosthogonimus parasitic in the gallbladder and bile ducts of ducks (Prosthogonimus orientalis and Prosthogonimus taiwanensis), and the one commonly seen in clinical practice is mainly Prosthogonimus orientalis.

1. Pathogen and epidemiological characteristics The pathogen is Prosthogonimus orientalis, belonging to the family Opisthorchiidae. The worm body is leaf-shaped, 2.4-4.7 mm long, with small spines on the body surface; the oral sucker is located at the front end of the worm body, and the ventral sucker is located at the center of the front 1/4 of the worm body. The testes are large, slightly lobed, and arranged one behind the other at the posterior end of the worm body. In front of the testes is an oval ovary; the uterus coils between the ovary and the intestinal bifurcation, and the uterus is filled with eggs. The eggs are pale yellow, oval, and measure 28-31 micrometers x 12-15 micrometers. This disease often occurs in summer and autumn, and clinically it is more commonly seen in ducks 1-4 months of age, while it rarely occurs in ducks under one month of age. Besides parasitizing ducks, the worm also parasitizes chickens, and occasionally cats, dogs and the human body. The disease is relatively widely distributed, and there are reports of its occurrence throughout the country.

2. Life history The first intermediate host is the mud snail (Parafossarulus striatulus), and the second intermediate hosts are fish such as the topmouth gudgeon and the Chinese false gudgeon. The metacercariae mainly parasitize the muscles and skin layers of fish. Ducks become infected by swallowing fish containing metacercariae, and eggs appear in the feces 16-21 days after infection.

3. Clinical symptoms In mild infections, no clinical symptoms are shown; in severe infections, affected ducks are listless, have poor appetite, ruffled feathers, weakness in both legs, emaciation and anemia, often have diarrhea, and the feces are mostly watery; most die from exhaustion. After infection, laying ducks show a decline in egg production rate; in severe cases, egg production stops and death occurs.

4. Pathological changes The liver is significantly enlarged, sometimes 1-2 times larger than normal, and its color becomes lighter, with white patterns and spots commonly seen due to bile duct hyperplasia. In cases with a slightly longer course, the liver texture becomes hard, and on the cut surface the bile duct walls are thickened and the duct lumens are enlarged, containing coagulated matter of yellow-green bile and worm bodies. The gallbladder is distended, the bile is dark green or ink green, and there are varying numbers of worm bodies in the gallbladder cavity; the gallbladder wall is thickened, and the intestinal mucosa shows catarrhal inflammation. A small number of cases also show pericardial effusion, splenomegaly, and hemorrhage of the cecal tonsils.

5. Prevention and control measures Strengthen environmental hygiene and the cleaning and disinfection of duck houses; the removed duck manure should be piled up and fermented for biological heat treatment, and duck flocks must never be fed raw fish. In addition, affected duck flocks should be treated one by one with drugs, such as albendazole at 50-100 mg per kg body weight, or praziquantel at 10-15 mg per kg body weight orally, both of which have good therapeutic effects.