Trichinellosis is caused by larvae of roundworms - mainly the species Trichinella (T.) spiralis. To date, four species of trichinella are known in Europe. These pathogens are called trichinella or trichinae. The last known autochthonous outbreak of disease in humans caused by a domestic pig occurred in 1970 after the consumption of poorly smoked meat from a domestic pig infested with trichinae.

Trichinellosis is a worldwide spread mammalian zoonosis, which occurs independently of climatic conditions. In Central Europe, trichinellosis is now rare. In some eastern and Baltic EU countries, incidences are higher, with most cases of disease caused by meat products from wild boar.

Domestic pigs, wild boar and horses are hosts for trichinae. Rodents (e.g. rats) and wild animals (e.g. foxes) are considered as reservoirs. Humans represent a false host, as they cannot transmit trichinae.

Infestation occurs through the consumption of raw or insufficiently heated meat containing Trichinella larvae (encapsulated in muscle cells - exception Trichinella pseudospiralis). Digestive enzymes in the stomach release the larvae from the meat and they mature into small worms in the cells of the upper mucosa of the small intestine within a few days. Females begin laying up to 1,500 larvae as early as four to seven days after ingestion by the host. The young larvae pass through the intestinal mucosa and enter the muscles via the bloodstream, where they can survive encapsulated in muscle cells for years. Oxygen-rich muscles, i.e. muscles with a good blood supply, such as the diaphragm, neck, chewing muscles, muscles of the shoulder girdle or upper arms, are preferred.

The incubation period is 5 to 15 days and depends on the number of Trichinella larvae ingested. The number of ingested Trichinella larvae that cause clinical disease in humans varies - more than 70 ingested larvae are very likely to cause disease. Infection from person to person is not possible.

Trichinellosis is a mild to fatal foodborne disease in humans, who are considered highly susceptible hosts. The severity of the disease depends on the number of larvae ingested and the immune response of the individual. The symptoms of the disease in humans are characterized in the initial phase by fever, abdominal pain and diarrhea. In the later course of the disease, muscle and joint pain as well as typical edema in the facial area are in the foreground.

Slightly infected patients usually recover without complications by bed rest and with the help of a painkiller. Severe infections are treated with drug therapy against worm larvae infestation. Drug treatment is more successful the earlier it is carried out.

Heating meat to over 70 °C is considered to safely kill larvae. Deep freezing at minus 15 °C reduces the infectivity of the parasite: Smoking, curing and drying are not suitable for killing the larvae.

In Austria, cases of the disease in humans are very rare: In the past 50 years, only so-called "imported" cases of trichinellosis have been registered by the health authorities in Austria. These were people who became infected with Trichinella larvae during a stay abroad or who brought infected meat products back to Austria, usually during a holiday at home, and fell ill in Austria after eating them.

Six cases were reported to the EMS in 2023 (EMS, as at 02/01/2024).

In Austria, 4,645,174 domestic pigs, 469 horses and 43,682 wild boars from the wild and 764 farmed wild boars were tested for Trichinella as part of the official meat inspection in 2023. Trichinella infestation was not detected in any of the animals tested. No positive Trichinella cases have been detected in Austrian breeding pigs, fattening pigs or horses for decades.

Pigs kept indoors are considered free of Trichinella infestation, as the animals have no possibility of ingesting infested fresh meat. The EFSA is critical of the appropriateness of the statutory trichinae examination of domestic pigs. Wild boar, on the other hand, must generally be regarded as possible carriers of trichinosis. Scientific studies have shown that the parasite is also present in the fox population in Austria, with a clear west-east divide in its distribution.

The suspected diagnosis can be confirmed by the detection of specific antibodies in the blood of the patient; in the case of massive infestation, the larvae can be detected in the tissue by histological examination of muscle biopsy specimens.

Animals that may be carriers of Trichinella and are intended for human consumption must be examined for Trichinella larvae after slaughter or killing and before the meat is placed on the market (Implementing Regulation (EU) 2015/1375; EN ISO 18743/2015). The examination is carried out using the so-called digestion method: A precisely defined amount of muscle by weight of the carcass subject to examination (usually from the area of the diaphragm pillar) is dissolved by means of artificial digestion and the sediment of the digestion liquid is checked under microscopic observation for the presence of Trichinella larvae.

In the event of positive Trichinella detection, the entire carcass is confiscated by the competent veterinary authority and sent for verifiable disposal.