Haemonchus contortus

Haemonchus contortus
Haemonchus contortus
Systematics
Trunk : Roundworms (Nematoda) Class : Secernentea Order : Strongylida Family : Trichostrongylidae Genre : Haemonchus Type : Haemonchus contortus
Scientific name
Haemonchus contortus
Cobb , 1898

Haemonchus contortus , also called red stomach worm or twisted stomach worm , is a parasite that attacks sheep and goats.

distribution

In a supraregional evaluation of 775 pathological-anatomical examinations of sheep in 2005, inflammations of the gastrointestinal tract were found in 47.2 percent of the animals . Usually parasites were the cause. Among the roundworms , the Haemonchus contortus is the most important representative. Infections are particularly widespread in Central Europe in sheep and goats and it is often detected after gastrointestinal diseases with fatal consequences.

features

The color of the parasite is reddish brown. It belongs to the roundworms in the Trichostrongylidae family . The worm is two to three millimeters long. The worms are very fertile with egg excrements of over 100 per gram of feces. They live on tissue and blood.

Life cycle

The development cycle is two to weeks. The eggs secreted in the gastrointestinal tract are excreted with the faeces of the host animals. Then four larval stages are passed through. The third larva is ingested by the host animal and then actively nests in the mucous membrane cells . There it sheds its skin into the fourth larva within a few days. This sheds its skin into an adult stomach worm, which parasitizes on the surface of the mucous membrane and the development cycle begins again. The parasite has the ability to interrupt its development in the host and to remain in the mucous membrane in a so-called permanent stage for a longer period of time. The development of the larvae is mainly influenced by the ambient temperature, but also by the immunity of the host animal and the herd management of the farm. The sheep and goats are mainly infected in the pasture and only rarely through stable feeding. The dung piles are trampled on during grazing and this spreads the larvae. The third larvae can overwinter, with particularly short, mild winters leading to high survival rates. As a result, there is a first phase with high infection rates immediately after the pasture has been driven out. More follow in late summer due to the infection of the young and in late autumn due to the increased larval population after multiple grazing. Due to the stress during pregnancy, childbirth and lactation, dams excrete increased larvae, which lead to increased infection rates in the particularly susceptible young animals.

Clinic, diagnosis

Sick animals are less lively and trot after the herd. They lag behind in development and growth and eat less. As the disease progresses, they become anemic , which can be seen from the pale mucous membranes, especially around the eyes. The loss of plasma protein results in throat edema in the end stage and the animals sometimes have difficulty breathing. In the case of a pure Haemonchus contortus infection, the feces remain firm and dry, but are dark to blackish due to the admixture of blood. Sick animals can become stuck and die after weeks of untreated disease. The blood count shows a reduced hematocrit , leukopenia and, due to impaired protein digestion, hypoalbuminemia . 1000 worms cause about 50 milliliters of blood loss per day. Punctiform, needle-prick-like blood clots are visible in the gastric mucosa. The destruction of the parietal cells leads to reduced acid production in the stomach. The increase in the pH value changes the composition of the intestinal bacteria and this hinders the digestive processes.

Prevention, control

If an infection is suspected, the faeces should first be parasitologically examined for worm eggs. Due to the intermittent excretion, a correspondingly large collective sample must be taken from at least every tenth animal. Once the pathogen has been identified, it is recommended that the animals no longer feed on the day of deworming if there is sufficient water supply and that they are dewormed in the morning. If the infected animals cannot eat again until the afternoon, the deworming agent stays longer in the gastrointestinal tract, which increases its effectiveness. At the same time, resistance can be prevented. In addition, the infection pressure can be reduced through appropriate pasture management. Newly sown willows are safest. But even the first use of the cut and then only one more grazing with sheep or goats significantly reduces the risk of infection.

Individual evidence

1. ↑ ^{a b c} Wilfried Adams: Fight endoparasites consistently, Chamber of Agriculture North Rhine-Westphalia, accessed on August 18, 2018.
2. ↑ ^{a b c d} M. Lange: Endoparasite infestation in small ruminants; The red stomach worm - Haemonchus contortus - in sheep and goat , Chemisches und Veterinäruntersuchungsamt Karlsruhe, accessed on August 18, 2018.
3. ↑ ^{a b c} Regine Koopmann, Michaela Dämmrich, Harm Ploeger: Hämonchus contortus , Johann Heinrich von Thünen-Institut, accessed on August 18, 2018.
4. ^ Regine Koopmann, Michaela Dämmrich, Harm Ploeger: Sustainable Parasite Management , Johann Heinrich von Thünen Institute, accessed on August 18, 2018.