Orf virus infection in Alaskan mountain goats, Dall's sheep, muskoxen, caribou and Sitka black-tailed deer

Abstract

Background: The zoonotic Orf virus (ORFV; genus Parapoxvirus, Poxviridae family) occurs worldwide and is transmitted between sheep and goats, wildlife and man. Archived tissue samples from 16 Alaskan wildlife cases, representing mountain goat (Oreamnos americanus, n = 8), Dall's sheep (Ovis dalli dalli, n = 3), muskox (Ovibos moschatus, n = 3), Sitka black-tailed deer (Odocoileus hemionus sitkensis, n = 1) and caribou (Rangifer tarandus granti, n = 1), were analyzed.

Results: Clinical signs and pathology were most severe in mountain goats, affecting most mucocutaneous regions, including palpebrae, nares, lips, anus, prepuce or vulva, as well as coronary bands. The proliferative masses were solid and nodular, covered by dark friable crusts. For Dall's sheep lambs and juveniles, the gross lesions were similar to those of mountain goats, but not as extensive. The muskoxen displayed ulcerative lesions on the legs. The caribou had two ulcerative lesions on the upper lip, as well as lesions on the distal part of the legs, around the main and dew claws. A large hairless spherical mass, with the characteristics of a fibroma, was sampled from a Sitka black-tailed deer, which did not show proliferative lesions typical of an ORFV infection. Polymerase chain reaction analyses for B2L, GIF, vIL-10 and ATI demonstrated ORFV specific DNA in all cases. Sequences from Dall's sheep formed a separate cluster, comparable to ORFV from domestic sheep. Sequences from the other species were different from the Dall's sheep sequences, but almost identical to each other.

Conclusions: This is the first major investigation of parapoxvirus infections in large Alaskan game species, and the first report of parapoxvirus infection in caribou and Sitka black-tailed deer. This study shows that most of the wild ruminant species in Alaska and from most parts of Alaska, can carry and be affected by ORFV. These findings call for attention to transmission of ORFV from wildlife to livestock and to hunters, subsistence harvesters, and wildlife biologists.

Keywords: Alaska; Caribou; Contagious ecthyma; Dall’s sheep; Deer; Mountain goat; Muskox; Parapoxvirus; Virology; Wildlife; Zoonosis.

Fig. 1

Map of Alaska showing the geographical distribution of the animal species and the location and numbers of the examined cases of contagious ecthyma in mountain goat (Oreamnos americanus), Dall’s sheep (Ovis dalli dalli), muskox (Ovibos moschatus), caribou (Rangifer tarandus granti) and Sitka black-tailed deer (Odocoileus hemionus sitkensis) (see Table 1 for identification of each case to game management unit; GMU)

Fig. 2

Contagious ecthyma in a mountain goat (Oreamnos americanus) having massive proliferative lesions over the muzzle, eyes and ears: case no. 6

Fig. 3

Photomicrograph of contagious ecthyma lesions in a mountain goat, case no. 6. a Section of the lip with ulcerative and proliferative dermatitis with marked acanthosis, hyperkeratosis, hydropic degeneration of the stratum spinosum, formation of subcorneal vesicles (arrow) and microabscesses below the stratum corneum, and heavy colonization with mixed bacteria (asterisk) (Obj. ×10). b Pale intracytoplasmic inclusion bodies (arrow) could be identified in stratum spinosum and granulosum (Obj. ×100)

Fig. 4

Contagious ecthyma in a young Dall’s sheep (Ovis dalli dalli) with mildly proliferative lesions and secondary bacterial infections, mainly restricted to the coronary bands and the skin below the dew claws: case no. 11

Fig. 5

Contagious ecthyma in a caribou (Rangifer tarandus granti) with a ulcerative lesions in the muco-cutaneous interface of the upper lip and b the plantar side of the hooves/coronary bands and carpal joints: case no. 16

Fig. 6

Phylogenetic comparison of the parapoxvirus sequences generated from tissues of mountain goat (Oreamnos americanus), Dall’s sheep (Ovis dalli dalli), muskox (Ovibos moschatus), caribou (Rangifer tarandus granti) and Sitka black-tailed deer (Odocoileus hemionus sitkensis) from Alaska (this study) with other parapoxvirus sequences (GenBank), including the type strain of ORFV (NZ-2). a Comparison of the 470 nucleotides from the putative viral envelope gene B2L compared to similar sequences from GenBank, and b with each other, including a reindeer (R. t. tarandus) isolate and a reference strain. c Comparison of the sequences obtained from the GM-CFS IL 2 gene (GIF). d Comparison of the sequences obtained from the putative interleukin 10 gene (vIL10) (see Table 1 for reference to sequence identity)