Louping ill in an alpaca

Seropositivity to louping ill virus in dogs in the UK

BACKGROUND

Louping ill virus (LIV) is a tick-borne flavivirus that can cause fatal meningoencephalomyelitis in dogs. Four dogs with confirmed LIV infection and a case series of dogs with suspected flavivirus infection have been reported in the UK. However, underreporting of LIV infection due to lack of testing is suspected.

METHODS

Surplus serum/plasma from 220 dogs was used to determine the seroprevalence of LIV by haemagglutination inhibition (HAI) test. Signalment and environmental factors were investigated for potential correlations with a positive titre (serum dilution of 1:20 or more).

RESULTS

Two hundred and two dogs were suitable for inclusion in the study, nine of which (4.5%) were seropositive. Among the dogs investigated for neurological disease (40/202; 19.8%), six (15%) were seropositive. Ectoparasiticide use approached significance (p = 0.055) for being protective against LIV seropositivity.

LIMITATIONS

The main limitations were the specificity of the HAI test, the relatively small number of samples, the low number of seropositive dogs, the poor geographical distribution of the samples and the inherent limitations of questionnaire-based research.

CONCLUSION

The seroprevalence of LIV in the UK dog population appears to be low. However, LIV should be considered in dogs presenting with unexplained acute or subacute progressive neurological clinical signs, especially because of the recent reports of several dogs with clinical flavivirus infections.

Phenotypic characterization of encephalitis in the brains of goats experimentally infected with Spanish Goat Encephalitis Virus

Spanish goat encephalitis virus (SGEV) is a novel tick-borne flavivirus subtype, closely related to the flavivirus louping ill virus (LIV). SGEV caused a severe, acute and mortal neurological disease outbreak in northern Spain in a goat herd. In order to characterize the cell population in lesions and to determine the distribution of the inflammatory cells, central nervous system (CNS) samples of nine female Alpine goats challenged subcutaneously with SGEV over the right thorax behind the elbow were evaluated using immunohistochemistry (microglia-Iba1, T lymphocytes-CD3, B lymphocytes-CD20 and astrocytes-GFAP). The number of microglia (37.8 %) and T lymphocytes (21.5 %) was greater than the number of B lymphocytes (16.8 %). Goats were classified into clusters based on the severity of histological lesions in CNS (A-mild to moderate lesions and B-severe lesions). Microglia was significantly more abundant than T and B lymphocytes in cluster B (severe lesions). The total area occupied by glial foci revealed that medulla oblongata and spinal cord were the most affected tissues. Astrogliosis (GFAP+) was present in the majority of the CNS sections being near to the pial surface. The lesion predominance on the right side of the medulla oblongata, which could be associated to the site of challenge suggestive of neurotropic route was also statistically confirmed. Results suggest that the cellular immune response would be the most important response to the SGEV infection.

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

Louping-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.

Zoonotic diseases in South American camelids in England and Wales

The number of South American camelids (SACs) in England and Wales is increasing and with this comes a risk of new and emerging infections. Although classified as livestock, these animals are also treated as pets and may be in regular contact with humans. This paper reviews zoonotic diseases that have been identified in SACs in England and Wales, and which pose a potential risk to human health. We also highlight the importance of surveillance continuing to capture information on infections in SACs for the protection of both public and animal health.

Louping ill virus: an endemic tick-borne disease of Great Britain

In Europe and Asia, Ixodid ticks transmit tick-borne encephalitis virus (TBEV), a flavivirus that causes severe encephalitis in humans but appears to show no virulence for livestock and wildlife. In the British Isles, where TBEV is absent, a closely related tick-borne flavivirus, named louping ill virus (LIV), is present. However, unlike TBEV, LIV causes a febrile illness in sheep, cattle, grouse and some other species, that can progress to fatal encephalitis. The disease is detected predominantly in animals from upland areas of the UK and Ireland. This distribution is closely associated with the presence of its arthropod vector, the hard tick Ixodes ricinus. The virus is a positive-strand RNA virus belonging to the genus Flavivirus, exhibiting a high degree of genetic homology to TBEV and other mammalian tick-borne viruses. In addition to causing acute encephalomyelitis in sheep, other mammals and some avian species, the virus is recognized as a zoonotic agent with occasional reports of seropositive individuals, particularly those whose occupation involves contact with sheep. Preventative vaccination in sheep is effective although there is no treatment for disease. Surveillance for LIV in Great Britain is limited despite an increased awareness of emerging arthropod-borne diseases and potential changes in distribution and epidemiology. This review provides an overview of LIV and highlights areas where further effort is needed to control this disease.