Declining body weight of moose calves related to parasite and disease burden

Body weights of hunted moose calves have markedly declined in southwestern Finland during this millennium, but the cause of this phenomenon is yet unknown. We studied whether the decline is associated with prevalence of parasites and diseases. For this purpose, we collected tissue samples (lung, heart, liver and faeces) from moose calves hunted in autumn in study area with declining calf body weights (N = 45) and in control area with no decline in body weight (N = 19). We compared the findings between regions and studied the relationship between carcass weight and parasitological and pathological parameters. The organ samples revealed infections by several parasites, including the lungworms Dictyocaulus capreolus and D. skrjabini, the cestode Taenia lynciscapreoli and the lancet liver fluke Dicrocoelium dendriticum. Parasitic infections of the digestive tract (strongylid nematodes, Moniezia sp., Eimeria sp.) and larvae of the meningeal worm Elaphostrongylus alces were observed by examining faecal samples. Inflammatory lesions in the membranes surrounding lung, heart and liver and in bile ducts occurred in all areas. We found that moose calves from the area with low and declining weight had a wider range of parasites and pathologies than calves from the control area. There was a negative correlation between total parasite and pathology burden and the carcass and heart weights. Parasite and disease burden was highest and weight parameters were lowest in the areas with the highest moose and total cervid densities.