Trichinella

Trichinella

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Changed on: 22.01.2019
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Trichinella are microscopically small roundworms of the Trichinella genus. To date, four trichinella species are known in Europe and they are differentiated using molecular diagnostic methods. A variety of hosts, primarily domestic pigs, wild boars and horses, but also a number of wild animals (including fox, bear, badger) and rodents (rats), carry these parasites. Humans are infected when they consume raw or undercooked meat products (e.g. bacon, ham) from infected animals. There are very few trichinella infections in Austria: only so-called “imported” trichinosis cases were registered by the Austrian health authorities in the past 35 years.

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Trichinella are microscopically small roundworms of the Trichinella genus. To date, four trichinella species are known in Europe and they are differentiated using molecular diagnostic methods. A variety of hosts, primarily domestic pigs, wild boars and horses, but also a number of wild animals (including fox, bear, badger) and rodents (rats), carry these parasites. Humans are infected when they consume raw or undercooked meat products (e.g. bacon, ham) from infected animals. There are very few trichinella infections in Austria: only so-called “imported” trichinosis cases were registered by the Austrian health authorities in the past 35 years.

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Transmission

Trichinella are usually found encapsuled (except Trichinella pseudospiralis) inside the muscle tissue of aforementioned animals.  When ingested, the larvae are separated from the muscle tissue in the course of the digestion process inside the stomach and migrate into the intestinal wall, where they become reproductive adults. The female worms produce a high number of live-born larvae that are distributed throughout the entire body via the bloodstream. The larvae prefer to settle in the skeletal muscle tissue, where they are encapsulated.

Symptoms

Trichinellosis is a food-borne disease that can have a mild to fatal effect in humans. Typical early stage symptoms in humans are fever, abdominal pains and diarrhoea. Later, muscle and joint pain, as well as typical oedema on the face, become more dominant.

Humans are considered highly susceptible hosts. The level of infection severity depends on the number of larvae ingested and, also, on the specific immune reaction of the host. Treatment with medication is possible and is much more successful, the earlier it is started.

Prevention

Animals that could be trichinella carriers and are designated for human consumption must be examined for trichinella larvae after being culled and before the meat is placed on the market (Regulation (EC) No. 2075/2005).

Approximately 1,000 horses and the majority of hunted wild boars are subjected to trichinella examinations in Austria every year due to this legal regulation. The examination is carried out using the so-called digestion method: a, in terms of weight, specifically defined amount of muscle tissue of the animal body to be tested (usually taken from the area of the diaphragm pillar) is dissolved using an artificial digestion process and the sediment of the digestion fluid is examined for the presence of trichinella larvae under the microscope.

Should the results be positive for trichinella, the entire animal body will be seized by the relevant veterinary agency and traceably disposed of.

Trichinella could only be detected in a few cases in wild boar in Austria in recent years. The animals that tested positive had all come from abroad, except in one case.  Most of the wild boars had come from Germany and Hungary and were processed in Austria before being sold. No positive cases of trichinella case have been identified in Austrian breeding and fattening pigs and horses for decades.

Scientific studies have shown that this parasite can also be found in the Austrian fox population, although there is a clear West-East divide.


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