Malabsorption in the horse associated with alimentary lymphosarcoma.

Three horses suffering from malabsorption were shown to have alimentary lymphosarcoma predominantly affecting the small intestine and the associated lymph nodes. The diffuse cellular infiltration in two of the case produced marked changes in the villous architecture reducing the available mucosal surface area, and, with lowered or barely detectable disaccharidase activities, contributed to the impairment of digestive-absorptive processes. One of the horses maintained a voracious appetite and was not diarrhoeic, but failed to gain weight, indicating differences in the production and utilisation of energy sources absorbed from the small and the large intestines. A large proportion of plasma cells in the infiltrate, and the resulting morphological changes in two of the cases bore a striking resemblance to features of alpha chain disease, an immunodeficiency disease of man, although immunological studies were not conducted on these horses.