A Fatal Case of Louping-ill in a Dog: Immunolocalization and Full Genome Sequencing of the Virus

M.P Dagleish,J.J Clark,C Robson,M Tucker,R.J Orton,M.S Rocchi

doi:10.1016/j.jcpa.2018.09.004

M.P Dagleish, J.J Clark + Show 4 more

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https://doi.org/10.1016/j.jcpa.2018.09.004

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Abstract

SummaryLouping-ill (LI), caused by louping-ill virus (LIV), results in a frequently fatal encephalitis primarily affecting sheep and red grouse (Lagopus lagopus scotica), but it does occur in other species. An adult male Border collie dog was definitively diagnosed with fatal LI and the lesion profile, LIV antigen distribution and full genome sequence of the LIV responsible were investigated to determine if this differed significantly from sheep-derived LIV. No gross lesions were present. The histological lesions were confined to the central nervous system and comprised of lymphocytic perivascular cuffs, glial foci, neuronal necrosis and neuronophagia. Immunolocalization of viral antigen showed small amounts present in neurons only. These histological and immunohistochemical findings were similar to those reported in affected sheep. Compared with published full genome sequences of sheep-derived LIV, only very minor differences were present and phylogenetically the virus clustered individually between a subclade containing Scottish strains, LIV 369/T2 and G and another subclade containing an English isolate LIV A. The LIV isolated from the dog shares a common progenitor with LIV A. These findings suggest there is no canine-specific LIV strain, dogs are susceptible to sheep-associated strains of LI and with the increase in tick prevalence, and therefore exposure to LIV, a safe, effective vaccine for dogs may be required.

Highlights

Louping-ill (LI) is a frequently fatal encephalitis primarily affecting sheep and red grouse (Lagopus lagopus scotica)
The aims of this study were to determine: (1) the morphology and distribution of histological lesions in the canine brain, (2) whether IHC used routinely in sheep samples is suitable for definitive diagnosis of LI in dogs and can reveal the distribution of louping-ill virus (LIV) antigen, and (3) whether the LIV responsible for this fatal canine case differed significantly at the genomic level compared with LIV recovered from clinically affected sheep
Blood was taken for serology as LI was suspected due to the dog living and working on a moorland sheep farm located in a LI endemic area

Summary

Introduction

Louping-ill (LI) is a frequently fatal encephalitis primarily affecting sheep and red grouse (Lagopus lagopus scotica). The causative agent is louping-ill virus (LIV), a single stranded RNA virus of the genus Flavivirus, family Flaviviridae, which is transmitted by the sheep tick (Ixodes ricinus) (Reid and Chianini, 2007). LI occurs in non-ovine ruminant species at a much lower incidence, including in cattle (Benavides et al, 2011), goats (Gray et al, 1988), roe (Capreolus capreolus) (Reid et al, 1976) and red deer (Cervus elaphus) (Reid et al, 1978), alpacas (Vicugna pacos) (Cranwell et al, 2008) and llamas (Lama glama) (MacAldowie et al, 2005).

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