Cervid herpesvirus 2 and not Moraxella bovoculi caused keratoconjunctivitis in experimentally inoculated semi-domesticated Eurasian tundra reindeer

Abstract

Background: Infectious keratoconjunctivitis (IKC) is a transmissible disease in semi-domesticated Eurasian reindeer (Rangifer tarandus tarandus). It is regarded as multifactorial and a single causative pathogen has not yet been identified. From clinical outbreaks we have previously identified Cervid herpesvirus 2 (CvHV2) and Moraxella bovoculi as candidates for experimental investigations. Eighteen reindeer were inoculated in the right eye with CvHV2 (n = 5), M. bovoculi (n = 5), CvHV2 and M. bovoculi (n = 5) or sterile saline water (n = 3; controls).

Results: All animals inoculated with CvHv2, alone or in combination with M. bovoculi, showed raised body temperature, increased lacrimation, conjunctivitis, excretion of pus and periorbital oedema; clinical signs that increased in severity from day 2 post inoculation (p.i.) and throughout the experiment, until euthanasia 5-7 days p.i. Examination after euthanasia revealed corneal oedema, and three animals displayed a corneal ulcer. CvHV2 could be identified in swab samples from both the inoculated eye and the control eye from most animals and time points, indicating a viral spread from the inoculation site.

Conclusions: This study showed that CvHV2 alone and in combination with M. bovoculi was able to cause the characteristic clinical signs of IKC in reindeer, whereas inoculation of M. bovoculi alone, originally isolated from a reindeer with IKC, did not produce clinical signs. Previous studies have suggested that herding procedures, animal stress and subsequent reactivation of latent CvHV2 infection in older animals is a plausible mechanism for IKC outbreaks among reindeer calves and young animals in reindeer herds. However, further studies are needed to fully understand the infection biology and epidemiology associated with IKC in reindeer.

Keywords: Alphaherpesvirus; Eye disease; IKC; Moraxella; Ophthalmology; Reindeer; Wildlife.

Fig. 1

Infectious keratoconjunctivitis (IKC) during an outbreak among free-ranging Eurasian semi-domesticated tundra reindeer (Rangifer tarandus tarandus): a corneal oedema indicated by an opaque and discolored cornea. b Severe grade of IKC with panophthalimitis, oedema and haemorrhage. This condition often involves corneal ulcer and may lead to permanent blindness

Fig. 2

Semi-domesticated Eurasian tundra reindeer (R21) experimentally inoculated with reindeer alphaherpesvirus (cervid herpesvirus 2; CvHV2). a Day 0, i.e. the day of inoculation, b day 5 post inoculation (p.i.), and c day 6 p.i.

Fig. 3

Semi-domesticated Eurasian tundra reindeer (R15) inoculated with Moraxella bovculi. a Day 0, i.e. the day of inoculation, b day 5 post inoculation (p.i.), and c day 10 p.i.

Fig. 4

Semi-domesticated Eurasian tundra reindeer (R1) inoculated with reindeer alphaherpesvirus (cervid herpesvirus 2; CvHV2) and Moraxella bovculi. a Day 0, i.e. the day of inoculation, b day 2 post inoculation (p.i.), and c day 5 p.i.