A wasting syndrome in Swedish moose (Alces alces): background and current hypotheses

In the 1980s, people in Sweden frequently responded to moose (Alces alces) found dead or in poor physical condition. The number of moose submitted for routine investigations to the National Veterinary Institute (SVA) increased tenfold and the hunters in Alvsborg County were especially concerned. Later, a complex wasting syndrome was described and reports of moose suffering from the syndrome have been collected since 1991. Today, there is no definitive answer as to the underlying causel(s) of the syndrome, but there are several plausible hypotheses that can be divided into two groups: food-related and host-parasite related. The food-related hypotheses are postulated to have any of the following ultimate causes: acidification/liming, browser density/food production or pollution. Our view is that few of the hypotheses have been critically tested. Most of the hypotheses are supported by some observations, which is to be expected because these are post-hoc attempts to explain these very observations.