Meningeal worm found in moose calves in South-West Finland

14.2.2013

<p>Meningeal worm ( <em>Elaphostrongylus alces</em>) has been found in moose calves examined in the South-West Finland archipelago. News of the occurrence of the parasite in Finland is new, but not surprising, as the meningeal worm is a common moose parasite in Sweden. The meningeal worm does not affect humans or pets. The meningeal worm findings were reported in a preliminary study by the Finnish Game and Fisheries Research Institute and Finnish Food Safety Authority Evira investigating possible reasons for the prolonged reduction in moose calf carcass weights in the South-West Finland archipelago.</p>

A little more than half of the 54 moose calves examined were found to be infected. The infections were mild, as only a few adult worms were found in the samples from individual calves. The meningeal worm is typically a parasite affecting calves. The parasite can affect the calf’s growth, and it can even cause a serious neurological disease. On the other hand, a mild infection may produce no symptoms.
The meningeal worm does not affect the use of the moose meat as food. Occasionally, the irritation caused by the parasites has resulted in small inflamed areas in the rump muscles of the moose that are visible to the naked eye, but these can be removed and the rest of the moose meat used as normal.

The moose meningeal worm is a nematode, with adult individuals living around the membranes covering the moose’s spinal cord or on the surfaces of muscles in its rear end. The adult worms are very thin and several centimetres long, barely visible to the naked eye. The worms produce larvae which are carried with blood circulation to the animals lungs, bronchial tubes and from there with swallowed phlegm into the alimentary canal and further with faeces into the environment. The parasite needs a slug or snail as an intermediary host. When the moose swallows infected molluscs with plants, it becomes infected.

The research study investigating the reduced carcass weights of moose calves in the South-West Finland archipelago selected as first-phase subjects the occurrence of the meningeal worm and the age structure of female moose stocks, their pregnancy rates and timings. The pregnancy rate of the moose population was found to be very good. Thus, the low numbers and youth of the males would not appear to be the reason for the small size of the calfs. The average carcass weight of individuals infected with meningeal worm was a little lower and the length of the lower jaw a little shorter than those of individuals on which no worms or larvae were found. However, the differences were not statistically significant.

There may be a number of reasons for the small calf size. Further research is required to throw light on them.

Additional information:
Researcher Tuire Nygrén, Finnish Game and Fisheries Research Institute, tel. +358 295 327 505
Research Professor Antti Oksanen, Finnish Food Safety Authority Evira, tel. +358 295 304 900

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