Dicrocoeliosis

The parasitic disease caused by the small liver fluke is called dicrocoeliosis . It belongs to the worm diseases ( helminthoses ) and occurs mainly in ruminants , but sometimes also in other (wild) animals and humans.

Occurrence

Certain environmental factors, the occurrence of intermediate hosts and the occurrence of ultimate hosts are of fundamental importance for the occurrence of dicrocoeliosis . It occurs on large pastures in lowlands and in mountains, mainly in drier regions with limestone soils . Pasture areas are usually contaminated by grazing animals, but wild ruminants such as rabbits and hares can also contribute to the spread.

Pathogenesis

The infection with liver flukes little effected by the ingestion of infected ants , the second intermediate host by screws , with the food. In the first few days after infection, the young liver fluke ( metacercariae ) migrate into the bile ducts of the final host. Mechanical irritation and the toxic effects of the metabolic end products of the small liver fluke initially lead to vascular dilatation , in the acute stage to inflammation of the bile ducts with tissue growth in the surrounding tissue. Severe, long-term infections lead to hardening and scarring of the liver with chronic inflammation of the bile ducts ( cholangitis ), dilation of the bile ducts and fibrosis . Very severe infections (> 4800 parasites) lead to an increased serum albumin level , normal or minor infections proceed without clinical symptoms (subclinical).

The small liver fluke can stay in the definitive host for up to six years; successful regulation or even reduction of the infestation through an immune reaction is not known.

Generally one can say that an infection is inconspicuous. Even very strong infestation leads to relatively mild symptoms, such as anemia , jaundice , edema , weakness and reduced performance.

diagnosis

An intravital diagnosis can be made by determining the concentration of eggs ( sedimentation or flotation method ). The flotation process with HgI ₂ / KI solution ( potassium tetraiodomercurate (II) , density 1.44 g / ml) is considered to be very precise . However, the concentration of eggs also depends on the stress of the infected animal, fluctuates with the time of day and is not necessarily dependent on the intensity of the infestation.

The diagnosis is usually only made in the slaughterhouse during the meat inspection . Obvious macroscopic indications are thickening and widening of the bile ducts and hardening of the liver. In the extensions and z. Liver fluke of various sizes are sometimes found in the gall bladder. However, not all cases of dicrocoeliosis are recognized.

Countercurrent immunoelectrophoresis is considered the most reliable serological test for an infestation and can also reveal dormant infections. Antibodies can also be detected by ELISA , sometimes four to eight weeks before the first eggs can be detected in the feces.

The detection of metacercaria of the lesser liver fluke can also serve as an indicator of dicrocoeliosis.

treatment

Treatment should only be given for severe infections. Trematode wormers must be administered in high doses and repeatedly. The use of some benzimidazoles and probenzimidazoles is particularly successful, followed by pyrazinoisoquinoline derivatives ( praziquantel ), salicylanilides ( closantel ) and diamfenetides . The most successful are wormers in winter and spring zeitigem, as this is the time of highest spread of small liver fluke. It is also advisable to carry out treatments at the end of the main infection season (late April / May).

For ecological reasons, extensive control of the intermediate hosts of the small liver fluke cannot take place. Since most of the infected ants are within a 50 cm radius of their anthills, the spread of dicrocoeliosis can at least to a certain extent be stopped by fencing the anthills. The density of intermediate hosts can also be controlled by the settlement of predators (e.g. turkeys , ducks , geese and chickens ; approximately 50 animals per hectare ).

Although vaccinations have already been carried out successfully in an experimental setting , no vaccination strategy has yet been developed.

Human infections

The infestation of humans by the little liver fluke is the exception. Due to the cycle of the lesser liver fluke, humans can only accidentally be infected by ants swallowing plant material and fruits. Therefore, children are particularly at risk. Symptoms of an infestation are digestive problems, gas , vomiting, diarrhea along with constipation and biliary colic . In addition to "real infections" there are also so-called "false infections" that occur through the consumption of infected animal material. In these “false infections”, so-called transit eggs migrate unchanged through the intestinal tract, so they can be detected in the stool even though there is no actual infection.

literature

• L. Ducháček, J. Lamka: Dicrocoeliosis - the present state of knowledge with respect to wildlife species. In: Acta Veterinaria Brno Volume 72, 2003, pp. 613-626.

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !