Muscle parasite of waterfowl is rare in Finland

17.2.2014

<p>Observations indicate that sarcocystosis (infection caused by the muscle parasite <em>Sarcocystis</em>) is rare in our waterfowl, although there are some regional variations. In autumn 2013, the Finnish Food Safety Authority Evira asked duck hunters to report any observations of muscle cysts caused by the <em>Sarcocystis</em> parasite. By the end of 2013, Evira had received more than 70 responses from hunters, of whom half had found evidence of the parasites.</p>

The survey indicated that a hunter had to shoot many birds to find an infected specimen. Those who detected parasites had an average estimated bag of 19 mallards in 2013. Those who had not found infected birds had shot 8.5 mallards on average.

In Western Finland, hunters who had found a Sarcocystis-infected duck had bagged 26 ducks on average, while in Eastern Finland 12 was enough. Seven hunters reported that over the years they had shot more than a hundred ducks in their hunting waters without ever observing a case of sarcocystosis. Estimated on the basis of the number of ducks shot, incidence of sarcocystosis is most common in mallards (3.6%) followed by Eurasian wigeons (2.9%) and Eurasian teals (0.5%).

Local differences in the incidence of the parasite
The parasite seems to occur widely in almost the whole of southern Finland; the most observations, eight, were made in Northern Karelia. No parasite observations were reported only in the responses from Lapland, Northern Ostrobothnia and Southwest Finland. Observations were divided among many municipalities. Three cases of parasite infection each were reported from Rautalampi, Polvijärvi and Inkoo, but commonly only one case was reported for each municipality.

In addition to observations of parasites in mallards, two observations were made concerning Eurasian wigeons, one concerning European teals and one concerning Northern shovellers. The wigeons, teal and shoveller were hunted in Eastern Finland, in the regions of Kainuu, Northern Savo and Northern Karelia.

Earlier observations have found the parasite in Lapland and Southwest Finland as well
In previous years, Sarcocystis samples have been sent to Evira from regions where no incidences of the parasite were found in the 2013 survey.  For instance, infections in numerous Eurasian wigeons have previously been observed in Hailuoto, Northern Ostrobothnia. In the 2000s, Evira received one mallard sample from Southwest Finland, and also one from the Åland Islands. One parasite-infected mallard from Kemijärvi was sent to Evira over a decade ago.

Sarcocystis infection in ducks is caused by the Sarcocystis rileyi parasite, which occurs in North America and Europe. In America, the definitive host of the parasite is the skunk. In the definitive host, the parasite reproduces sexually, and in the intermediate host asexually. The intermediate host is the prey of the definitive host. Waterfowl are intermediate hosts. The definitive host is a predator, but it is unknown which species this is in Europe.

As far as it is known, Sarcocystis parasites of ducks do not infect humans.

Map of the observations about Sarcocystis parasite (in Finnish).

For additional information, contact:
Researcher Marja Isomursu, Production Animal and Wildlife Research Unit
tel. +358 40 512 1248

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