Fascioliasis

Fascioliasis is caused by Fasciola vulgaris (Fasciola hepatica) and Fasciola gigantica (F. gigantica) from the family. Fasciolidae.

Sheep, goats and cattle suffer most often from fascioliasis, pigs, horses, camels, donkeys, reindeer and rabbits are somewhat less common. Wild animals are susceptible to fascioliasis - wild boars, roe deer, deer and rodents - hares, nutria, beavers and squirrels. Sometimes a person gets sick with fascioliasis. A favorite place for parasitizing fascioles is the bile ducts of the liver, less often - the lungs, heart, lymph nodes, pancreas. During the migration period , young forms of fascioles can be found in many other organs,

Fascioliasis causes great economic damage to animal husbandry and the meat industry.

Pathogens. Fasciola vulgaris is a leaf-shaped trematode, brown in color with a greenish tinge, from 2 to 3 cm long and about 1 cm wide, the cuticle is armed with small spikes. The oral and abdominal suckers are poorly developed, they are close together and located in the front part of the body. The initial section of the intestinal trunks forms lateral branches. The rosette-shaped uterus and branched ovary are located in the anterior third of the body behind the abdominal sucker. Branched testes occupy the middle and back parts of the body. Highly developed yolk cells occupy the lateral fields of the parasite's body. The genital bursa and the female genital opening are located between the fork of the intestine and the abdominal sucker.

The giant fasciola has an elongated shape and a large body length (5-7 cm). It is registered only in the southern and southeastern parts of the country.scheme of development of fasciola vulgaris

The eggs of fascioles are large: 0.13-0.14 mm long and 0.07-0.09 mm wide, oval-shaped, symmetrical, golden yellow, with a lid on one of the poles, are released into the external environment immature (the larva - miracidium is not formed inside)

In the intestines of definitive hosts, the adolescariae are released from the protective shell and enter the bile ducts of the liver hematogenically. The sexually mature stage of fascioles is reached in 3-4 months; the life span of fascioles in the body of a definitive host is 3-5 years (in the body of sheep, sometimes more than five years).

The life cycle. Fascioles are biohelminths. They develop with the participation of definitive, or definitive, hosts (agricultural and wild animals, as well as humans) and intermediate ones: for the common fasciola - the small pond - Limnaea truncatnla, and for the giant fasciola - the ear-shaped pond - L. auricularia.

Mature fascioles lay a large number of eggs, which are released into the external environment with animal feces. For further development of the eggs, the fascioles must get into a freshwater reservoir (pond, swamp, puddle, etc.). At a favorable temperature (15-30 °) and the presence of oxygen inside the egg, after 2-3 weeks, a miracidium is formed, which only enters the water in the light, actively penetrates into the body of a small or ear-shaped pond, then enters the liver of an intermediate the host, where the stages of sporocysts, redia (under favorable conditions - daughter redia) and cercariae successively take place (Fig. 6). The term of development of the parasite in the body of the mollusk from the miracidium to the cercarium is 2-3 months.

As a result of the parthenogenetic reproduction of the larval stages of fascioles, 5-15 redia are formed from one sporocyst, and 15-20 cercariae are formed from each redia. Hundreds (sometimes up to 1.5 thousand) of cercariae can come out of one mollusk into the external environment, which in a few hours turn into adolescariae; the latter are found on aquatic plants and on the surface of the water. Animals become infected in an alimentary way - by ingestion of adult fascioles.

Epizootological data. Fascioliasis caused by fasciola vulgaris is one of the widespread helminthiasis of farm animals in the USSR and abroad. Often this disease is registered in areas with favorable climatic conditions for the development of the main intermediate host of the pathogen - the small pond (Polesie, Forest-steppe and other zones).

The source of fasciologenic invasion is numerous definitive hosts of liver flukes - sick animals and fasciolocarriers. Factors of transmission of invasion are grass on lowland and swampy areas of pastures and hayfields, freshly harvested hay and mown grass in such places, water from puddles, ditches, swamps and other shallow reservoirs infested with fasciola adulterants (in the zone of biotopes of the small pond).

 Rainy summer contributes to a sharp increase in the number of mollusks in the biotopes of the small pond, as well as other limneids (species of the genus Limnaea) and the number of animals infested with fascioles. The high demands of the small pond to environmental conditions, apparently, determines the focal nature of biotopes (Limnaea truncatula habitats), the size of which often does not exceed several square meters. In fast-flowing streams and rivers, deep reservoirs with low water temperature and where the water is polluted with organic substances, as well as in reservoirs with sandy and peat bottoms, the small pond does not yashvet.

Most of the invasive mollusks die in winter. Infection of animals with fascioliasis in the middle zone occurs from the middle of the pasture season (from the second half of July), sharply increasing in autumn, when a large number of adult fascioles accumulate on pastures and reservoirs. The first cases of animal fascioliasis are noted in late summer and autumn, and a massive disease in winter.

Pathogenesis. Fasciolosis is a disease of the entire animal body. The pathogenic effects of fascioles consist of mechanical, inoculatory, antigenic, toxic and trophic influences. During the migration of young forms of fascioles, injury to the liver parenchyma, lymph nodes, pancreas and other organs occurs, accompanied by bleeding (especially in the liver) I have acute inflammation of damaged organs. In the phenomena of acute hepatitis, progressive anemia, sick animals sometimes die. Adult fascioles, accumulating in the bile ducts, cause their blockage, stagnation of bile and its decomposition. Liver function is severely impaired. Under the influence of the pathogenic action of fascioles, there is also a sharp depletion of the body with vitamins B12 and A. The bile ducts of the liver expand, and their walls thicken, thicken and often calcify (in cattle). Migrating fascioles contribute to the penetration of pathogenic microorganisms (open the gates of infection), as a result of which the pathogenic process is further aggravated. Cirrhosis of the liver develops.