Severe transmissible eye infection in reindeer: bacterium or virus?

Infectious keratoconjunctivitis (IKC) in semi-domesticated reindeer (Rangifer tarandus tarandus) is considered to be a multifactorial disease, which can affect tens of animals during an outbreak, and lead to the destruction of the eye and blindness. Serum and conjunctival swab samples from 321 healthy and diseased (IKC) Scandinavian reindeer have been analyzed by bacteriological cultivation, PCR and ELISA, revealing the presence of Moraxella sp., among other bacteria and Cervid herpesvirus 2 (CvHV2) and antibodies against CvHV2. To determine the primary agent of a disease in a natural environment can be difficult due to uncontrolled factors. An experimental infection was performed in order to conclude if CvHV2 or Moraxella bovoculi, alone or in combination, are determining factors for the development of IKC in reindeer. Twentyone healthy reindeer (seronegative for CvHV2 and culture negative for M. bovoculi) were selected for the experiment. Reindeer were inoculated with M. bovoculi (group 1, n=5), M. bovoculi and CvHV2 (group 2, n=5), CvHV2 (group 3, n=5) and physiological salt water (controls, group 4, n=3). Groups 1 and 4 showed no signs of IKC, while all animals in groups 2 and 3 developed intense lacrimation, swollen eyelids, corneal oedema and, in two cases, corneal ulcer. Specific antibodies against CvHV2 were detected by ELISA 6 days after inoculation. Few colonies of M. bovoculi and other microorganisms were detected along the experiment, which may suggest the possibility of secondary bacterial infections if the disease was allowed to develop beyond the defined experiment end-point. Until further analysis of the data and samples produced by this study, it can be concluded that CvHV2 is a primary agent of IKC in reindeer, whereas M. bovoculi did not seem to be involved as a determinant agent, even if the bacterium has been associated with severe stages of IKC in reindeer during outbreaks.