Serosurvey of bluetongue, caprine arthritis-encephalitis (CAE) and Maedi-Visna in Barbary sheep (Ammotragus lervia) of a southern Brazilian zoo / Estudo sorológico dos vírus da língua azul, da artrite-encefalite caprina e Maedi-Visna em aoudads (Ammotragus lervia) em um zoológico do Sul do Brasil

Bluetongue (BT) is an infectious and non-contagious disease of compulsory notification which may affect domestic and wild ruminants, transmitted by Culicoides spp. midges. Despite the high morbidity and mortality in sheep, role of wild animals in the BT cycle remains unclear. Caprine arthritis-encephalitis (CAE) and Maedi-Visna virus (MVV) have been reportedly found in goats and sheep, but not described in wildlife species. Accordingly, serum samples from 17 captive Barbary sheep (Ammotragus lervia) from Curitiba zoo, southern Brazil, were tested for bluetongue, caprine arthritis-encephalitis (CAE) and Maedi-Visna viruses by agar gel immunodiffusion (AGID) and enzyme linked immunosorbent assay (ELISA). Antibodies for bluetongue were observed in 6/17 (35.3%) Barbary sheep by AGID test and in 7/17 (41.2%) by ELISA. All samples were negative for the presence of antibodies against caprine arthritis-encephalitis (CAE) and Maedi-Visna viruses. These findings indicate that Barbary sheep may be infected by bluetongue virus and act as wildlife reservoir in both captive and free-range environments.(AU)

A língua azul é uma doença infecciosa e não contagiosa, de notificação obrigatória, que pode afetar ruminantes domésticos e silvestres, transmitida por mosquitos do gênero Culicoides spp. Apesar da alta morbidade e mortalidade em ovelhas, o papel de animais silvestres no ciclo do vírus da língua azul é desconhecido. A artrite encefalite caprina (CAE) e Maedi-visna vírus (MVV) tem sido encontrados em cabras e ovelhas, porém não há descrição em espécies selvagens. Amostras de soro de 17 aoudads (Ammotragus lervia), mantidos em cativeiro no Zoológico de Curitiba, Sul do Brasil, foram testadas para os vírus da língua azul, da artrite encefalite caprina (CAE) e Maedi-visna, utilizando imunodifusão em gel de ágar e o teste de ELISA (enzyme linked immunosorbent assay). Foram observados anticorpos para o vírus da língua azul em 35,3% (6/17) aoudads utilizando a imunodifusão em gel de ágar e 41,2% (7/17) no ELISA. Todas as amostras foram negativas para a presença de anticorpos contra os vírus da artrite encefalite caprina e Maedi-visna. Esses resultados indicam que os aoudads podem ser infectados pelo vírus da língua azul e atuar como um reservatório silvestre tanto em cativeiro quanto em vida livre.(AU)

Investigação sorológica das lentiviroses de pequenos ruminantes nas microrregiões homogêneas do Alto Médio Canindé, Picos e Floriano, Piauí, Brasil / Serological investigation of lentiviruses of small ruminants in the microregions of Alto Médio Canindé, Picos and Floriano, Piauí state, Brazil

Lentivírus de pequenos ruminantes (LV) é o termo genérico utilizado para designar os vírus da artrite encefalite caprina e Maedi-Visna, os quais pertencem à família Retroviridae, subfamília Orthoretrovirinae, gênero Lentivirus. Tais vírus infectam caprinos e ovinos, causando enfermidades de curso lento com lesões inflamatórias, crônicas e degenerativas que podem atingir vários órgãos, provocando caquexia e morte. Os animais infectados eliminam o vírus sobretudo por meio de secreções e excreções e transmitem-no especialmente em situações de estreito contato. Não há tratamento até o momento. O controle é baseado na criação segregada, no manejo e no sacrifício dos positivos. Esse agente infeccioso já foi relatado em várias partes do mundo, sendo responsável por perdas econômicas significativas. Por o agente ter sido verificado em vários estados do Brasil e por não existirem dados soroepidemiológicos nas mesorregiões sudeste e sudoeste piauiense, esta pesquisa teve por objetivo realizar inquérito sorológico para investigar a ocorrência de anticorpos para o LV em ovinos e caprinos nas microrregiões do Alto Médio Canindé, Picos e Floriano, no Piauí. Para tanto, foram coletadas 1.280 e 1.360 amostras de soro caprino e ovino, respectivamente, oriundos de 20 municípios, distribuídos nas três microrregiões, sendo o número de amostras proporcional ao rebanho efetivo de cada município. As amostras de soro foram analisadas utilizando o teste de imunodifusão em gel de agarose (IDGA). Nenhum dos soros pesquisados reagiu positivamente, constatando-se soroprevalência nula. Ressalta-se a importância da implantação de um rigoroso programa de controle para que se possa evitar a introdução e/ou a disseminação desse agente infeccioso nessas microrregiões.(AU)

Small ruminant lentiviruses (LV) is the generic term for the caprine arthritis-encephalitis and ­­Maedi-Visna viruses, which belong to the Retroviridae family, Orthoretrovirinae subfamily, Lentivirus genus. The virus infects goats and sheep, causing slow course of disease with inflammatory, chronic and degenerative lesions, which can reach several organs, provoking cachexia and death. Infected animals eliminate the virus mainly through secretions and excretions and transmit it especially in close contact situations. There is no treatment to date. The control is based on segregated creation, management and sacrifice of the positive. This infectious agent has been reported in various parts of the world and is responsible for significant economic losses. It was verified in several states of Brazil and there are seroepidemiological data in southeast and southwest mesoregions of Piauí, Brazil. This research aimed to perform serological survey to investigate the occurrence of antibodies to LV in sheep and goats, in the regions of Alto Médio Canindé, Picos and Floriano. So, 1,280 and 1,360 serum goats and sheep samples, respectively, were collected, coming from 20 municipalities, distributed in the 3 microregions. The number of samples was proportional to the actual herd of each municipality. The samples were analyzed using the agar gel immunodiffusion test. None of the surveyed sera reacted positively, though there is a null seroprevalence. It was emphasized the importance of implementing a rigorous control program in order to prevent the introduction and spread of this infectious agent in these microregions.(AU)

The pathogenicity of louping ill virus for mice and lambs.

Mice and lambs were infected with the LI/I, LI/31 or MA54 strain of louping ill virus (LIV) to provide information relevant to testing the efficacy and biosafety of a new generation of flavivirus vaccines based on a Semliki Forest virus (SFV) vector. Whereas clinical signs and neuropathological lesions were consistently severe in mice, the majority of lambs showed lesions of moderate severity and only lambs with severe lesions were clinically affected. For both species, dispersal of viral antigen occurred along neuronal cell processes, and neuronal degeneration and death were confirmed as central events after infection with LIV. In contrast to lambs, in which most lesions remained localized, mice showed widely dispersed lesions which were associated with less intense leucocytic infiltrates. Among the infiltrating cells, histiocytes predominated and apoptotic forms were prominent in severely affected animals. The intranasal route of infection provided an efficient avenue for entry of LIV into the brain and resulted in lesions which were more severe than those produced by subcutaneous or intraperitoneal inoculation.

Recombinant Semliki Forest virus particles encoding the prME or NS1 proteins of louping ill virus protect mice from lethal challenge.

Recombinant Semliki Forest virus (rSFV) vaccines encoding louping ill virus (LIV) genes prME and NS1 were examined. Cells transfected with rSFV-prME RNA showed correct processing of the precursor prME and the release into the medium of M and E proteins in particulate form, whilst rSFV-NS1-transfected cells secreted glycosylated, heat-labile NS1 dimers. Mice immunized with rSFV particles produced antibodies against prME and NS1 that were mainly of the IgG2a subtype, indicating that a T-helper 1 immune response was induced. Immunization with prME- or NS1-encoding particles induced T-cell proliferation. Mice vaccinated intraperitoneally (i.p.) with rSFV-prME and/or rSFV-NS1 were significantly protected from lethal i.p. challenge by two strains of LIV, the virulent LI/31 strain, from which the commercial LIV vaccine is derived, and the less-virulent LI/I antibody-escape variant. Intranasal (i.n.) vaccination was protective for rSFV-prME only against LI/31 challenge and not against challenge with LI/I. Immunization with rSFV-NS1 was protective against i.p. and i.n. challenge with both virus strains when given i.p., but was not protective when given i.n. For unvaccinated mice infected with LIV, all animals showing clinical signs had severe degenerative and inflammatory lesions in the central nervous system. None of the rSFV-vaccinated mice that survived challenge showed central nervous system pathology, with the exception of mild leptomeningitis in a minority of LI/31-infected mice. This suggests that protection following immunization with rSFV must occur at early stages of LIV infection.

Sequencing and antigenic studies of a Norwegian virus isolated from encephalomyelitic sheep confirm the existence of louping ill virus outside Great Britain and Ireland.

We have carried out an antigenic analysis and nucleotide sequence comparison of the envelope glycoprotein of recognized louping ill virus strains isolated from Scotland with that of a Norwegian virus known to cause encephalomyelitis in sheep. Monoclonal antibodies with defined specificity for the louping ill virus envelope glycoprotein failed to distinguish between the Norwegian virus and prototype louping ill virus in indirect immunofluorescence, haemagglutination inhibition and neutralization tests. Nucleotide sequencing of the envelope glycoprotein and alignment of the deduced amino acid sequence with other known sequences revealed that the Norwegian virus closely resembles (> 95% identity for nucleotide and > 98% identity for amino acid sequences) louping ill virus. Maximum variation in identities among four strains of louping ill virus were 4.4% and 1.8% respectively for nucleotide and amino acid alignments. We conclude that sheep encephalomyelitis in Norway is caused by louping ill virus. These results imply that other viruses present in Europe and known to cause encephalitis/encephalomyelitis of sheep could be caused by louping ill virus.

Louping ill virus envelope protein expressed by recombinant baculovirus and vaccinia virus fails to stimulate protective immunity.

We have constructed recombinant baculoviruses and vaccinia viruses containing cloned DNA, encoding either the envelope protein alone or all of the structural proteins (core, membrane and envelope) of louping ill virus. Glycosylated viral envelope protein, presented both inside and on the surface of insect and mammalian cells, was expressed by all four recombinant viruses. Differences in antigenic presentation of the envelope protein were observed between the envelope protein and structural protein constructs as well as between the insect and mammalian cell expression systems. Despite the expression of epitopes known to elicit neutralizing and protective antibodies when present in authentic antigen, the recombinant envelope protein expressed by either vector failed to induce, in mice or rabbits, either neutralizing or protective antibodies against louping ill virus.

Immunosuppression in toxoplasmosis: further studies on mice infected with louping-ill virus.

Mice were infected with an avirulent cyst-producing strain of Toxoplasma gondii and given injections of louping-ill virus 7 days later; control mice were given virus but not Toxoplasma. Test and control mice were then killed, in groups, 2, 4, 6, 8 and 10 days later. In the dually infected mice viraemia was later, greater and more prolonged; titres of virus recovered from brain and spleen were greater; production and haemagglutinating antibody to louping-ill virus was later and less, and inflammation in the brain was more severe, than in mice given virus alone. We suggest that T. gondii suppressed the immunity of mice, making them more susceptible to the virus, and that a significant proportion of the increased number of inflammatory cells observed in the brain could have been toxoplasma specific and not virus-specific and hence contributed to the increased susceptibility of the dually infected mice to louping-ill virus.

Field trials of an inactivated oil-adjuvant vaccine against louping-ill (Arbovirus group B).

A single dose of inactivated louping-ill oil-adjuvant vaccine elicited a sero-logically detectable immune response in sheep lasting for at least 1 year. These sheep when exposed to a natural focus of louping-ill virus were completely protected from clinical disease and 1 year after vaccination were able to pass on a substantial maternal immunity to their lambs.Twenty-nine per cent of unvaccinated sheep, exposed at the same time, died from clinical louping-ill; half of the survivors showed positive sero-conversion and became immune, while the other half remained susceptible. The incidence of fatal encephalomyelitis in sheep which were known to have circulated virus exceeded 50% in 2 out of 3 trials conducted simultaneously in different locations in Scotland in 1969.