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Mixed infection of Trichinella spiralis and Trichinella pseudospiralis detected in wild boar for the first time anywhere in the world

04/2006, 20.02.2006

BfR discovery will have repercussions for the examination of game meat

Scientists at the National Reference Laboratory for Trichinellosis within the Federal Institute for Risk Assessment have diagnosed a type of trichina in killed wild boar in Germany. Prior to this, it had only been detected abroad, mainly in carnivorous birds and wild animals. The working group of Dr. Karsten Nöckler, Head of the Molecular Diagnostics and Genetics unit in the BfR Biological Safety department, isolated the parasites from the flesh of a wild boar killed on the island of Usedom. The animal was infected with both the encapsulated classical pig parasite Trichinella spiralis and the non-encapsulated species Trichinella pseudospiralis. This is the first time that a mixed infection has been diagnosed anywhere in the world. This finding will have repercussions for meat inspection. Classical tests using a trichinoscope are not able to detect Trichinella pseudospiralis.

In Germany up to now only the pathogen Trichinella spiralis had been detected in wild boars. Using modern molecular-biological and microscopic methods BfR scientists have now succeeded in showing that wild boar may also be infected with the pathogen Trichinella pseudospiralis. Wild boars are omnivores. Pathogens probably cross to the animal when it eats the infected carcases of perished wild animals or birds. Whereas animals infested with trichinae do not manifest any symptoms of disease, both Trichinella spiralis and Trichinella pseudospiralis can cause serious illnesses in human beings. In this specific case a very high concentration of parasites with more than 900 larvae was found in the muscle meat of the wild boar.

Although the German herds of domestic pigs are free of trichinae, there are reports every now and again of people contracting trichinellosis. The source of the infection with this parasite is mostly the consumption of products like raw sausage or minced meat made from imported pork. Raw sausages, raw ham or minced meat from infected wild boars are another source. Larvae ingested in this way grow into worms in the human intestinal mucosa. Their larvae then go on to nest in muscle tissue. The disease begins with gastro-intestinal disorders and later there are also allergic symptoms and fever. Oedemas are formed and muscle pain may also be experienced. The infection can prove fatal.

Testing for trichinae is, therefore, mandatory and is undertaken as part of meat control. The findings from Usedom mean that, in future, wild boar meat will also have to be examined for infestation with Trichinella pseudospiralis. For this the classical test involving a trichinoscope is not sufficient. In contrast to Trichinella spiralis, Trichinella pseudospiralis does not have the typical collagen capsule. The larvae can, therefore, be easily mistaken for muscle fibres. Infestation with this pathogen can only be reliably determined through testing with artificially pre-digested samples under the microscope. The individual larvae are then easily identifiable. Hunters should, therefore, submit the meat of animals they have killed for examination by institutes that are proficient in this detection method before eating it themselves or passing it on for consumption by others.

The probability of finding trichinae in wild boar in Germany is relatively low, 1:50,000. However, if the meat of an infected animal were to reach the market, the consequences would be serious since several people are likely to become infected and contract the disease.

The full results of the study are soon to be published in the scientific journal Veterinary Parasitology.


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