Muskox status, recent variation, and uncertain future.

Muskoxen (Ovibos moschatus) are an integral component of Arctic biodiversity. Given low genetic diversity, their ability to respond to future and rapid Arctic change is unknown, although paleontological history demonstrates adaptability within limits. We discuss status and limitations of current monitoring, and summarize circumpolar status and recent variations, delineating all 55 endemic or translocated populations. Acknowledging uncertainties, global abundance is ca 170 000 muskoxen. Not all populations are thriving. Six populations are in decline, and as recently as the turn of the century, one of these was the largest population in the world, equaling ca 41% of today's total abundance. Climate, diseases, and anthropogenic changes are likely the principal drivers of muskox population change and result in multiple stressors that vary temporally and spatially. Impacts to muskoxen are precipitated by habitat loss/degradation, altered vegetation and species associations, pollution, and harvest. Which elements are relevant for a specific population will vary, as will their cumulative interactions. Our summaries highlight the importance of harmonizing existing data, intensifying long-term monitoring efforts including demographics and health assessments, standardizing and implementing monitoring protocols, and increasing stakeholder engagement/contributions.

Mycoplasma conjunctivae-Associated Keratoconjunctivitis in Norwegian Muskox (Ovibos moschatus).

In late summer 2014, an outbreak of ocular disease occurred in the Norwegian muskox (Ovibos moschatus) population. Animals showed rings of pus around their eyes and one euthanized animal was diagnosed with acute keratoconjunctivitis. The DNA sequence analysis of eye-swab samples from this animal revealed a high abundance of Mycoplasma conjunctivae.

Mycoplasma ovipneumoniae--a primary cause of severe pneumonia epizootics in the Norwegian Muskox (Ovibos moschatus) population.

The Norwegian muskox (Ovibos moschatus) population lives on the high mountain plateau of Dovre and originates from animals introduced from Greenland. In the late summers of 2006 and 2012, severe outbreaks of pneumonia with mortality rates of 25-30% occurred. During the 2012 epidemic high quality samples from culled sick animals were obtained for microbiological and pathological examinations. High throughput sequencing (pyrosequencing) of pneumonic lung tissue revealed high concentrations of Mycoplasma ovipneumoniae in all six animals examined by this method and Pasteurella multocida subsp. multocida in four animals, whereas no virus sequences could be identified. Mycoplasma ovipneumoniae and P. multocida multocida were also isolated by culture. Using real time PCR on lung swabs, M. ovipneumoniae was detected in all of the 19 pneumonic lungs examined. Gross pathological examination revealed heavy consolidations primarily in the cranial parts of the lungs and it also identified one case of otitis media. Histologically, lung lesions were characterized as acute to subacute mixed exudative and moderately proliferative bronchoalveolar pneumonia. Immunohistochemical (IHC) examination revealed high load of M. ovipneumoniae antigens within lung lesions, with particularly intensive staining in the neutrophils. Similar IHC finding were observed in archived lung tissue blocks from animals examined during the 2006 epidemic. An M. ovipneumoniae specific ELISA was applied on bio-banked muskox sera from stray muskoxen killed in the period 2004-2013 and sick muskoxen culled, as well as sera from wild reindeer (Rangifer tarandus tarandus) on Dovre and muskoxen from Greenland. Serology and mycoplasma culturing was also carried out on sheep that had been on pasture in the muskox area during the outbreak in 2012. Our findings indicated separate introductions of M. ovipneumoniae infection in 2006 and 2012 from infected co-grazing sheep. Salt licks shared by the two species were a possible route of transmitting infection.

Fatal pneumonia epizootic in musk ox (Ovibos moschatus) in a period of extraordinary weather conditions.

The musk ox is adapted to extreme cold and regarded as vulnerable to the impacts of climate change. Population decline is proposed to occur due to changes in forage availability, insect harassment, parasite load, and habitat availability, while the possible role of infectious diseases has not been emphasized. The goal of the present article is to describe an outbreak of fatal pasteurellosis that occurred in the introduced musk ox population of Dovrefjell, Norway in 2006, causing the death of a large proportion of the animals. The epizootic coincided with extraordinary warm and humid weather, conditions that often are associated with outbreaks of pasteurellosis. The description is based on long series of data from the surveillance of the musk ox population, weather data from a closely located meteorological station, and pathoanatomical investigation of the diseased animals. It is concluded that the weather conditions likely were the decisive factors for the outbreak. It is suggested that such epizootics may occur increasingly among cold-adapted animals if global warming results in increased occurrence of heat waves and associated extreme weather events, thereby causing population declines and possibly extinctions.

A severe outbreak of contagious ecthyma (orf) in a free-ranging musk ox (Ovibos moschatus) population in Norway.

During July-October 2004, 19 (18 calves, 1 yearling) free-ranging musk oxen (Ovibos moschatus) at Dovre, Norway, were observed with contagious echtyma-like lesions, and 16 of them were euthanized. Six musk oxen were subjected to necropsy, histopathological and microbiological examinations. All euthanized animals had lesions consistent with contagious ecthyma presenting as wart-like, scabby lesions on the muzzle, lips, oral mucosa and limbs to a variable extent. The histopathological examination showed pustular dermatitis characterized by epidermal proliferation, reticular degeneration, degenerating keratinocytes with intracytoplasmic eosinophilic inclusion bodies, vesicopustules, microabscesses and multifocal ulcerations in the epidermis which was covered by a serocellular crust. Pathology and bacteriology showed evidence of secondary infections in the skin and draining lymph nodes. Electron microscopy (negative staining) of lesions from four animals detected parapoxvirus with the typical arrangement of the outer protein filaments. Parapoxvirus DNA was detected in tissue samples from two examined animals by polymerase chain reaction (PCR) with primers from the B2L-gene. A DNA sequence of 326 nucleotides from the amplicon was compared with similar DNA sequences from parapoxvirus isolated from sheep, reindeer, musk ox and cattle. The outbreak was caused by a virus similar to other circulating orf virus variants in Norway. Antibodies against parapoxvirus were detected with a virus neutralization test in 3 of 35 musk oxen (8.6%) sampled at Dovre between 2004 and 2006. This is the first report of a severe outbreak of contagious ecthyma in free-ranging musk oxen.