Date Published: September 28, 2007
Publisher: BioMed Central
Author(s): Terje D Josefsen, Karen K Sørensen, Torill Mørk, Svein D Mathiesen, Kathrine A Ryeng.
In a project to determine the causes of winter mortality in reindeer in Finnmark County, northern Norway, the most frequent diagnosis turned out to be complete emaciation, despite several of the reindeer having been given silage for up to 4 weeks before they died. The present paper describes autopsy results and other findings in these animals.
Autopsies were made of 32 reindeer carcasses, and 28 of these were diagnosed as completely emaciated based on lack of visible fat and serous atrophy of subepicardial and bone marrow fat. Other investigations of the carcasses included histology, bacteriology, parasitology (counting of macro parasites and faecal egg counting), analysis of vitamin E and selenium in liver, chemical and botanical analysis of rumen content, analysis of lipid content in femur bone marrow and estimation of muscle atrophy by use of a muscle index.
Main findings were: Low carcass weight, severe muscle atrophy, hemosiderosis in liver and spleen, subcutaneous oedema (18%) and effusions to body cavities (18%). Two types of lipofuscin granula were identified in the liver: One type occurred in liver endothelial cells of all carcasses, while the other type occurred in hepatocytes, and prevailed in adult animals. Abomasal haemorrhages, consistent with previously described stress lesions, was present in 68% of the carcasses. Diarrhoea occurred in 2 cases, and loose faecal consistency was associated with silage feeding. Rumen content was low in crude protein. Grass dominated rumen content in silage-fed carcasses, while reindeer on natural pastures had mainly woody plants, mosses and litter in rumen. Stem dominated the grass fraction in rumens with high grass content, indicating ruminal indigestion as a cause of emaciation in silage fed animals. Some cases had heavy infestation of parasites such as warble fly larvae (Hypoderma tarandi), throat bot larvae (Cephenemyiae trompe) and lung nematodes.
Lack of appropriate amounts and/or appropriate quality of feed has been the main cause of emaciation, though heavy infestation of parasites may have contributed to the emaciation in some cases.
Free-living reindeer are subjected to seasonal changes in food quality and availability, and weight loss in winter due to sub-maintenance feed intake, inanition, is regarded as normal. If inanition is severe and prolonged, the outcome will be fatal. When all fat depots are completely depleted the animals succumb in a cachectic state due to lack of energy to maintain body homeostasis.
Emaciation may be caused by lack of feed or by different forms of chronic disease. In the present study, chronic disease was observed in some cases, in the form of heavy parasitic infestation with warble fly larvae, throat bot larvae and nematodes in the lung (Dictyocaulus sp. and/or Elaphostrongylus rangiferi larvae). However, heavy parasite burden was not a consistent finding in completely emaciated carcasses, and occurred also in control animals. So even though the parasite burden have contributed to emaciation in some cases, we still consider the parasites only as modifying factors, and regard the main cause of emaciation to be lack of appropriate amounts and/or appropriate quality of feed. Analysis of vitamin E and selenium in liver showed values within the normal range of sheep and cattle , thus eliminating these factors as a contributing cause of chronic wasting.
The author(s) declare that they have no competing interests.
All authors participated in the planning of the project. KAR was the leader of the project from which the study arose. TDJ, KKS and TM planned and performed the autopsies, histological and bacteriological examinations and feacal egg counts, and collected all samples for further analyses. Statistical analyses were done by TDJ. SDM initiated the chemical and botanical analysis of rumen content, and KAR initiated the analysis of liver vitamin E and selenium. TDJ were the main author, with contributions from the other authors. All authors read and approved the final manuscript.