Abstract
BackgroundInfectious keratoconjunctivitis (IKC) is one of the most common ocular diseases in ruminants worldwide. In addition to keratitis and conjunctivitis, animals with IKC can develop uveitis, corneal ulcer, and in severe cases, blindness. The bacteria Moraxella spp. has been described as the primary causative agent of infectious bovine keratoconjunctivitis (IBK) in cattle (Bos taurus), while Chlamydia spp. and Mycoplasma conjunctivae are considered the main causative agents of IKC in sheep (Ovis aries). Previous studies indicated cervid herpesvirus 2 (CvHV2) as the primary causative agent of IKC in semi-domesticated reindeer (Rangifer tarandus tarandus). The aim of the study was to investigate the presence and prevalence of potential pathogens for IKC in reindeer, and compare the ocular microbiota of animals with IKC, with apparently healthy animals.ResultsSemi-domesticated reindeer (n = 341), with (n = 108) or without (n = 113) ocular clinical signs, or with no information on clinical status (n = 120), were sampled in Norway, Sweden and Finland in 2010–2014. Seroprevalence was 37.4% for alphaherpesvirus (95/254), 3.8% for gammaherpesvirus (8/211) and 7.1% for pestivirus (15/211) (ELISA). PCR analyses of conjunctival swab samples revealed a prevalence of 28.5% for CvHV2 (57/200), 11.9% for Chlamydiaceae (16/135) and 1.0% for M. conjunctivae (2/197). Bacteriological cultivation of 202 conjunctival swab samples revealed bacterial growth from 75.2% of the samples, with Moraxella spp. being isolated from 21.6% (11/51) of the animals with and 5.6% (5/84) without ocular clinical signs. A significant association (p < 0.001) existed between the presence of clinical signs of IKC and CvHV2 DNA in the affected eyes, an association that was not present for other microorganisms.ConclusionsThese results support the hypothesis that CvHV2 is the primary agent of IKC in semi-domesticated reindeer in Fennoscandia, with Moraxella bovoculi being a secondary candidate, since it was isolated in two different outbreaks of IKC. Further studies should be carried out to better understand the infection biology and the pathogenesis of IKC in reindeer.
Highlights
Infectious keratoconjunctivitis (IKC) is one of the most common ocular diseases in ruminants worldwide
Among animals with known clinical status (n = 140), it was not possible to establish an association between the presence of antibodies against gammaherpesvirus and the presence of clinical signs of IKC (p = 0.257), a lack of association that persisted when addressing calves (p = 0.394) or adults (p = 0.312) separately
The detection of cervid herpesvirus 2 (CvHV2) DNA in eye swabs by Polymerase chain reaction (PCR) and the prevalence of PCR positive individuals, which increased with the severity of the clinical signs of IKC (Fig. 3), supports the hypothesis that CvHV2 is a primary agent in the development of IKC in reindeer [15]
Summary
Infectious keratoconjunctivitis (IKC) is one of the most common ocular diseases in ruminants worldwide. The bacteria Moraxella spp. has been described as the primary causative agent of infectious bovine keratoconjunctivitis (IBK) in cattle (Bos taurus), while Chlamydia spp. and Mycoplasma conjunctivae are considered the main causative agents of IKC in sheep (Ovis aries). Infectious keratoconjunctivitis (IKC) is a severe transmissible ocular disease, which affects many ruminant species worldwide, including reindeer (Rangifer tarandus). In cattle (Bos taurus), infectious bovine keratoconjunctivitis (IBK) is considered the most important eye disease worldwide [1], and the bacterium Moraxella bovis is considered as the main causative agent [2]. It has been shown that many different species of bacteria can be cultured from the eyes of apparently healthy ruminants, with no associated clinical signs.
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