Fascioliasis is one of the most important parasitic diseases in cattle and sheep. It is caused by Fasciola hepatica and Fasciola fasciola which parasitize in the liver bile ducts of cattle, buffalo, goats, sheep and other ruminants. Pigs, horses, and wild animals can also be parasitic, and can be parasitic to humans. The disease can cause acute or chronic hepatitis and cholangitis, followed by systemic poisoning and nutritional disorders, often causing mass deaths of cattle and sheep.

1 Pathogen

There are two pathogens of this disease, namely Fasciola hepatica and Fasciola gigas.

1.1 Fasciola hepatica has a flat leaf-like appearance, with a body length of 20 to 35 mm and a width of 5 to 13 mm. The live worms taken out from the bile duct are brownish-red and turn grayish-white after fixation. Its front end is a cone-shaped protrusion, called the cone. The base of the head cone expands and widens to form shoulders, which then gradually narrow. There are many small spines on the body surface. The oral sucker is located at the front end of the head cone, and the ventral sucker is in the middle of the shoulder level. The genital pore opens in front of the abdominal sucker. The digestive system of the worm consists of the mouth, pharynx, esophagus and two intestinal tubes separated from the left and right. Each intestinal tube has many small side branches. The reproductive system is hermaphroditic. Two branched testicles are arranged front and back in the middle and rear part of the insect body. One antler-like branched ovary is located on the right side behind the ventral sucker. The egg mold is located in the center of the worm's body just in front of the testicles. Between the egg mold and the abdominal sucker is a coiled uterus, filled with yellow-brown eggs. The vitelline gland is composed of many small brown follicles distributed on both sides of the insect body.

The eggs are oval and yellowish brown; 120 to 150 microns long and 70 to 80 microns wide; the front end is narrow, has an inconspicuous egg cover, and the rear end is blunt. The thin and transparent egg is filled with yolk cells and 1 embryonic cell.

1.2 The adult flukes are in the shape of long leaves, 33 to 76 mm long and 5 to 12 mm wide. The difference between the large fluke and Fasciola hepatica is that there is no obvious head cone protrusion at the front end of the insect body and the shoulders are not obvious; the two sides of the insect body are almost parallel, the front and rear width does not change much, the rear end of the insect body is blunt and rounded; the abdominal sucker is larger , the sucker cavity extends backward and forms a blind sac; the inner side of the intestinal tube has more branches and obvious branchlets; the testicles have fewer branches and occupy a smaller space and smaller length.

The eggs are dark yellow, 150 to 190 microns long and 75 to 90 microns wide.

2 Epidemiology

This disease is endemic and mostly occurs in low-lying, humid grazing areas. Most epidemic infections occur in summer and autumn. Temperature and sunlight promote the development of Fasciola hepatica and the hatching of miracidia, so these seasons are important seasons for the mass reproduction of Fasciola hepatica miracidia. In summer and autumn, the climate is warm and the rainfall is abundant, which can cause a large number of cercariae to breed and form metacercariae widely on grass leaves, infecting livestock and causing the widespread epidemic of hepatic fasciolosis. At the same time, because metacercariae are extremely viable, they can maintain their infectivity for a long time in a humid natural environment.

2 Symptoms

The clinical manifestations of fascioliasis vary depending on the intensity of infection and the resistance of the livestock body, age, feeding and management conditions, etc. Animals often do not show symptoms when they are mildly infected. Symptoms can show when the number of infections is large (about 250 adult worms in cattle and about 50 adult worms in sheep). However, young livestock can show symptoms even if they are lightly infected.

Acute fascioliasis mainly occurs in sheep. The infection season mostly occurs in late summer and autumn. When sheep swallow a large number of metacercariae in a short period of time, the migration of larvae in the body causes the sheep to become infected. Clinical manifestations include depression, elevated body temperature, reduced appetite, and occasional diarrhea. Subsequently, the affected animals developed a series of anemia phenomena such as pale mucous membranes, significant decreases in red blood cell count and hemoglobin. Severe cases can die within days.

Chronic sheep fascioliasis is caused by adult worms that parasitize in the hepatobiliary ducts. Clinical manifestations: The affected sheep gradually lose weight, have pale mucous membranes, anemia, rough coat that easily falls off, and edema under the eyelids, under the jaw, and under the skin of the chest and abdomen. Loss of appetite, constipation and diarrhea occur alternately. As the course of the disease prolongs, the sheep's physical condition gradually decreases, and finally the sheep dies due to cachexia. The general course of the disease can last up to 1 to 2 months.

Fascioliasis in cattle is mostly chronic. However, the symptoms are more obvious in calves (1.5-2 years old). Obvious symptoms and death will only appear in adult cattle when there are a large number of infections and the affected animals are in poor physical condition.

3 Diagnosis

Mainly make a comprehensive judgment based on clinical symptoms, epidemiological data, egg examination and pathological autopsy results.

(1) It is better to use the water washing and sedimentation method to check the eggs.

(2) The diagnosis of acute fascioliasis in sheep is mainly based on pathological autopsy. After tearing the liver of the sheep, the larvae of Fasciolia can be found in the water.

(3) Currently, the most commonly used immunological tests are the one-blood and three-test technology, namely spot enzyme labeling triple diagnosis and indirect hemagglutination diagnosis technology.

5 Prevention and Control

5.1 In terms of prevention, comprehensive prevention and control measures must be taken to achieve better results (1) Regular deworming and deworming are important methods of prevention and treatment one. The frequency and time of pest control must be combined with the actual local conditions and conditions. Under normal circumstances, if deworming is carried out once a year, it can be carried out in late autumn and early winter. If deworming is carried out twice, the other deworming can be carried out in the spring of the following year. (2) Manure treatment: Cattle and sheep manure must be fermented to kill insect eggs before it can be used. In particular, the manure after deworming needs to be treated strictly. (3) Selection of grazing land should be as high and dry as possible for grazing. Rotational grazing is also a necessary measure when conditions permit. (4) It is also important to pay attention not to use aquatic plants contaminated by metacercariae to strengthen the source and hygiene management of feed and drinking water.

5.2 In terms of treatment, the principle of treating fascioliasis is to carry out anthelmintic and symptomatic treatment at the same time. Especially for weak animals, we should pay more attention to the commonly used treatment drugs: sulfur diclofenac, cattle Based on 40-60 mg per kilogram of body weight, and 75-100 mg per kilogram of body weight for sheep, the affected animals will have some diarrhea after taking it, and will generally recover on their own after 14 days. Nitrachlorophene, 3-7 mg per kilogram of body weight for cattle, 4-6 mg for sheep, taken orally once. This drug is effective against adult worms. Aophenate is currently used for a long time and has a good killing effect. Prothiocarbazole, It is a broad-spectrum anthelmintic drug and is effective against adult worms. The dose is 10 to 1 mg per kilogram of body worms, administered by gavage.