Crowding and winter emergency feeding as predisposing factors for kerato-conjunctivitis in semi-domesticated reindeer in Norway.

Due to the hard environmental and climatic situation in late winter 1999, a herd of about 200 free-ranging, semi-domesticated reindeer was gathered in a paddock in northern Norway for emergency feeding. About the same number of reindeer was not corralled but supplementary fed on their winter pastures. The fodder was of relatively good quality but very dusty and fed in a very dry environment. Six weeks later, an outbreak of eye-infection was diagnosed in one third of the corralled reindeer; mild symptoms were observed in most of them, but 11 animals showed severe signs of disease. No signs of disease were found in the non-corralled animals. Ten reindeer died through emaciation, the eleventh was sacrificed. Histopathological diagnosis of two severely affected eyes revealed a severe purulent kerato-conjunctivitis with bacteria and plant particles embedded in purulent exudates on the cornea and conjunctiva. In one eye from the two most affected animals Actinomyces pyogenes, coagulase-negative Staphylococci and Escherichia coli and in the other one Staphylococcus aureus and Escherichia coli were found. The bacteria encountered in this study are not considered the primary cause of disease. They seem rather to be opportunistic infectious agents of eyes that have been irritated mechanically through exposure to dusty fodder in a dry environment. The stress through unfamiliar corralling of the reindeer, that followed an insufficient fodder supply, could be considered as an additional infection supporting factor. This case-report emphasises on the importance of different factors involved in favouring outbreaks of disease in reindeer, under intensified husbandry conditions. Even though crowding and emergency feeding may be, at certain circumstances, the only means of survival for reindeer, a negative impact of implied crowding diseases on their productivity, must be considered, as well.

Influence of diet on the occurrence of intraepithelial microabscesses and foreign bodies in the ruminal mucosa of reindeer calves (Rangifer tarandus tarandus).

The forestomach mucosa was examined for pathological lesions in 12 healthy free-ranging reindeer calves at different seasons, and in 32 reindeer calves fed lichen (n = 3), baled grass silage (n = 24) or pelleted feed (n = 5). No gross lesions were seen. Samples for histology were taken from reticulum, omasum and four sites in rumen. In histological sections a total of 182 intraepithelial microabscesses (IEMAs) and 16 foreign body lesions (FBLs) were observed in the ruminal mucosa, while 1 IEMA was found in omasum and no lesions in reticulum. The number of animals having 0, 1-10, 11-20 and > 20 IEMAs per four ruminal sections (one from each sample site) was 19, 19, 5 and 1, respectively. None of the free-ranging or lichen-fed animals had more than 1 IEMA per four ruminal sections, while 58% (14/24) of the animals fed silage and 40% (2/5) of the animals fed pelleted feed had 2 or more IEMAs per 4 ruminal sections. FBLs occurred more frequently in animals with high numbers of IEMAs, and it is suggested that both IEMAs and FBLs are caused by plant particles penetrating the ruminal epithelium. The lesions did not seem to indicate an inferior diet nor influence the health of the animals.

Increase in gamma delta T cells in the ruminal mucosa of reindeer calves (Rangifer tarandus tarandus L.) induced by baled grass silage.

Leukocytes in the forestomach mucosa of reindeer (Rangifer tarandus tarandus L.) were investigated by immunoperoxidase staining of cryostat sections, using monoclonal antibodies against antigens on sheep leukocytes. Mucosal samples from three free-ranging reindeer calves were compared with samples from three calves fed baled grass silage previously shown to induce increased frequency of lesions in the ruminal epithelium. In both groups, MHC-II + cells and gamma delta T cells were observed, located within or just below the basal layer of the stratified epithelium. Computer-assisted morphometric analysis showed that the number of gamma delta T cells in the ruminal mucosa was higher in the silage-fed than in the free-ranging animals. No marked difference in number of MHC-II + Langerhans cells was observed between the groups.

T cell subsets and Langerhans cells in the forestomach mucosa of adult sheep and sheep foetuses.

As part of a study on leukocytes in the ruminant forestomach the occurrence and distribution of T cells and major histocompatibility complex Class II positive (MHC-II+) cells in the forestomach mucosa of sheep were investigated. Samples were taken from the reticulum, atrium ruminis, ventral rumen, dorsal rumen and omasum of five healthy adult ewes and seven nearly fullborne foetuses. Frozen sections were stained with an indirect immunoperoxidase method using monoclonal antibodies against sheep MHC-II, CD4 and CD8 molecules and the sheep gamma delta T cell receptor. Both MHC-II+ cells and T cells were distributed along the basal lamina of the epithelium, with either mainly intraepithelial (CD8+ and gamma delta +cells) or mainly subepithelial (MHC-II+ and CD4+ cells) location. The MHC-II+ cells showed dendritic morphology and were interpreted as Langerhans cells. In adults ewes CD4+T cells comprised the major T cell subset at all sample sites. The number of T cells declined from the atrium ruminis through the ventral rumen to the dorsal rumen, while the number of Langerhans cells showed no marked variation between different sample sites. In foetuses, Langerhans cells showed a relatively high prevalence, while T cells were sparse and showed a more random distribution in the rumen wall. No marked variation between sample sites were observed in the fetal forestomachs. It is concluded that Langerhans cells and T cells are normally present in the forestomach mucosa of sheep, and it is suggested that the Langerhans cells represent a constituent component, while the prevalence and distribution of T cells may be influenced by antigen leakage through the epithelium.