Molecular characteristics and prevalence of small ruminant lentiviruses in goats in Japan.

Small ruminant lentiviruses (SRLVs), which comprise caprine arthritis-encephalitis virus (CAEV) and maedi-visna virus (MVV), are prevalent in goats and sheep worldwide, including in Japan. However, little is known about the molecular characteristics of goat lentiviruses in Japan. In this study, a molecular and phylogenetic analysis of the long gag region was performed. The phylogenic tree demonstrated that all samples belonged to SRLV subtype B1. Two clusters were identified, with one cluster distinct from previously reported strains of subtype B1. In addition, several alterations in the amino acid sequence were detected in immunodominant epitopes of the gag region. To gain a deeper understanding of the genetic diversity of SRLVs in Japan, it will be necessary to increase the sample size and conduct a broader survey. The present report is important for establishing baseline information on the prevalence of SRLV in Japan and providing data to develop a new, more sensitive diagnostic test for effective control of SRLV.

Caracterização epidemiológica e fatores de risco associados à infecção por lentivírus de pequenos ruminantes na região do semiárido paraibano, Nordeste do Brasil / Epidemiological characterization and risk factors associated with lentivirus infection in small ruminants in the semiarid of Paraíba State, Northeastern Brazil

O objetivo deste estudo foi determinar a soroprevalência de lentivírus de pequenos ruminantes (LVPR) e identificar os fatores de risco para a ocorrência de caprinos e ovinos soropositivos no semiárido do Estado da Paraíba. Foram utilizados 1.733 animais, sendo 1.274 caprinos procedentes de 62 Unidades de Produção (UPs) e 459 ovinos provenientes de 32 UPs. Para o diagnóstico sorológico da infecção por lentivírus foi utilizado o teste de imunodifusão em gel de ágar (IDGA). Dos 1.274 caprinos analisados 15 (1,18%) foram soropositivos, enquanto que todos os 459 ovinos foram soronegativos. Das 62 propriedades caprinas analisadas oito (12,9%) apresentaram pelo menos um animal soropositivo. Os fatores de risco para a ocorrência de caprinos soropositivos foram área da propriedade (odds ratio = 3,28; p = 0,044), ausência de capacitação dos produtores (odds ratio = 8,29; p = 0,042) e uso de monta natural não controlada (odds ratio = 6,78; p = 0,012). Conclui-se que a infecção por lentivírus de pequenos ruminantes, demonstrada pela detecção de anticorpos, está disseminada em rebanhos caprinos do semiá­rido paraibano, e sugere-se o incentivo à capacitação contínua dos produtores, manutenção de reprodutores negativos ao LVPR e utilização de inseminação artificial com o intuito de evitar o contato físico entre macho e fêmeas.(AU)

The aim of this survey was to determine the seroprevalence of small ruminant lentivirus (SRLV) and to identify risk factors for the occurrence of seropositive goats and sheep in the semiarid region of Paraiba State. It were used 1,733 animals, being 1,274 goats from 62 Production Units (PU) and 459 sheep from 38 PU. For the serological diagnosis of lentivirus infection the agar gel immunodiffusion test (AGID) was used. Of the 1,274 goats 15 (1.18%) were seropositive, and all 459 sheep were seronegative. Of the 62 goat herds eight (12.9%) presented at least one seropositive animal. Risk factors for the occurrence of seropositive goats were area of the property ≤35 ha (odds ratio = 3.28; p=0.044), not training of producers (odds ratio = 8.29; p=0.042) and use of uncontrolled natural mating (odds ratio = 6.78; p=0.012). It is concluded that lentivirus infection detected by serology is spread in goat flocks in the semiarid of the State of Paraíba, and it is suggested to encourage the continous capacitation of owners, maintenance of reproducers negative for SRLV and use of artificial insemination aiming to avoid the physical contact among male and females.(AU)

The occurrence of maedi-visna virus in Lebanon.

Maedi-visna (MV) is a chronic viral disease prevalent in adult sheep that is caused by a virus belonging to the small ruminant lentivirus group (SRLV). This disease is considered to affect the international trade of sheep and is classified in the World Organisation for Animal Health (OIE) list of notifiable animal diseases. Although maedi-visna virus (MVV) has been detected in many countries, no study on its occurrence has been carried out in Lebanon. For this purpose, a serological survey of infection with MVV was conducted in seven of the eight Lebanese governorates using a competitive enzyme-linked immunosorbent assay (ELISA). A total of 184 individual blood samples from sheep of the local breed 'Awassi', originating from 16 farms distributed throughout the seven Lebanese governorates, were collected and analysed. Among the 184 tested sheep, 131 sheep from the16 farms visited were MVV positive. This presents a prevalence of 71% MVV-positive animals and 100% MVV-positive farms. The results indicate the need for further systematic investigations into the between-herd and within-herd prevalence of MV in Lebanon.

Le maedi-visna (MV) est une maladie virale chronique causée par un virus appartenant au groupe des lentivirus des petits ruminants (SRLV) et affectant les moutons adultes. La maladie a une incidence sur les échanges internationaux d'ovins et figure sur la liste des maladies à déclaration obligatoire de l'Organisation mondiale de la santé animale (OIE). La présence du virus maedi-visna est attestée dans de nombreux pays mais jusqu'à présent aucune étude ne lui avait été consacrée au Liban. Pour y remédier, une enquête sérologique recourant à une épreuve immuno-enzymatique (ELISA) par compétition a été conduite dans sept des huit gouvernorats du Liban afin de déterminer la prévalence de l'infection par le virus maedi-visna. Au total, 184 échantillons sanguins prélevés sur des moutons de race locale (Awassi) originaires de 16 élevages répartis dans les sept gouvernorats ont été analysés. Des résultats positifs ont été obtenus sur 131 des 184 prélèvements ; tous les élevages étaient représentés. La prévalence est donc de 71 % à l'échelle des individus et de 100 % à l'échelle des élevages. Il ressort de ces résultats que la prévalence à l'intérieur des élevages ainsi que celle entre élevages devraient faire l'objet d'enquêtes systématiques plus poussées au Liban.

El maedi-visna (MV) es una enfermedad viral crónica prevalente en ovejas adultas, cuyo agente etiológico es un virus del grupo de los lentivirus de los pequeños rumiantes. Figura en la lista de enfermedades de declaración obligatoria de la Organización Mundial de Sanidad Animal (OIE) porque se considera que afecta al comercio internacional de ovejas. Aunque el virus maedi-visna (VMV) ha sido detectado en muchos países, nunca antes se había estudiado su presencia en el Líbano. Para ello se llevó a cabo un estudio serológico de la infección por el virus en siete de los ocho distritos administrativos del país mediante un ensayo inmunoenzimático (ELISA) de competición. Se extrajeron y analizaron un total de 184 muestras sanguíneas de ovejas de la raza autóctona «awassi¼ procedentes de 16 explotaciones repartidas en los siete distritos libaneses. De esas 184 muestras, dieron resultado positivo para el VMV 131, correspondientes a ovejas de las 16 explotaciones visitadas. Ello supone una prevalencia del 71% de animales positivos al virus y del 100% de explotaciones positivas. Los resultados ponen de manifiesto la necesidad de investigar más sistemáticamente la prevalencia del maedi-visna entre los rebaños y dentro de los rebaños del Líbano.

Generation of a molecular clone of an attenuated lentivirus, a first step in understanding cytopathogenicity and virulence.

Small ruminant lentiviruses infect goats and sheep, inducing clinical disease in a minority of infected animals. Following an eradication campaign, clinical cases may disappear in a population. The complete elimination of these lentiviruses is however difficult to achieve and the spreading of less virulent strains often parallels the elimination of their virulent counterparts. Here, we characterized three such strains isolated from a flock in the post-eradication phase. We completely sequenced their genomes, showing that one of the isolates was most probably the product of a recombination event between the other two viruses. By comparing the sequences of these isolates with those of virulent strains, we found evidence that particular LTR mutations may explain their attenuated phenotype. Finally, we constructed an infectious molecular clone representative of these viruses, analyzing its replication characteristics in different target cells. This clone will permit us to explore the molecular correlates of cytopathogenicity and virulence.

Mutations in Ovis aries TMEM154 are associated with lower small ruminant lentivirus proviral concentration in one sheep flock.

Small ruminant lentivirus (SRLV), also called ovine progressive pneumonia virus or maedi-visna, is present in 24% of US sheep. Like human immunodeficiency virus, SRLV is a macrophage-tropic lentivirus that causes lifelong infection. The production impacts from SRLV are due to a range of disease symptoms, including pneumonia, arthritis, mastitis, body condition wasting and encephalitis. There is no cure and no effective vaccine for preventing SRLV infection. However, breed differences in prevalence and proviral concentration indicate a genetic basis for susceptibility to SRLV. Animals with high blood proviral concentration show increased tissue lesion severity, so proviral concentration represents a live animal test for control post-infection in terms of proviral replication and disease severity. Recently, it was found that sheep with two copies of TMEM154 haplotype 1 (encoding lysine at position 35) had lower odds of SRLV infection. In this study, we examined the relationship between SRLV control post-infection and variants in two genes, TMEM154 and CCR5, in four flocks containing 1403 SRLV-positive sheep. We found two copies of TMEM154 haplotype 1 were associated with lower SRLV proviral concentration in one flock (P < 0.02). This identified the same favorable diplotype for SRLV control post-infection as for odds of infection. However, frequencies of haplotypes 2 and 3 were too low in the other three flocks to test. The CCR5 promoter deletion did not have consistent association with SRLV proviral concentration. Future work in flocks with more balanced allele frequencies is needed to confirm or refute TMEM154 association with control of SRLV post-infection.

Isolation of maedi/visna virus from a sheep in Japan.

Maedi/visna (MV) is a lentiviral disease of sheep caused by the maedi/visna virus (MVV). Although MV is prevalent in many countries, it had not been reported in Japan. In 2011, however, three sheep in northern Japan were reported to be seropositive against the MVV antigen, indicating a persistent MVV infection. In the present study, we isolated MVV from one sheep to confirm MVV infection and conducted genomic classification of the virus. The co-culture of leukocytes from a seropositive sheep with fetal goat lung cells resulted in the formation of syncytial cells and the amplification of a long terminal repeat sequence of MVV by polymerase chain reaction. The isolate was confirmed as being MVV, rather than the caprine arthritis-encephalitis virus based on phylogenetic analysis of the gag gene sequence. Although the sheep was asymptomatic, nonpurulent meningitis and demyelination were found in the spinal cord. These were considered to be early lesions associated with pathogenic MVV infection. Therefore, the present study demonstrated that MVV is distributed in Japan.

Impact of maedi-visna in intensively managed dairy sheep.

Maedi-visna (MV) is a slow lentiviral disease of sheep that has a significant economic impact in many sheep-producing regions although there remains a paucity of data relating to actual production losses resulting from this disease. The objective of this study was to evaluate direct losses, through death or culling, from two dairy sheep flocks with high seroprevalences of infection over a 2 year period. Maedi-visna was found, either alone or in combination with other diseases, to be the most common disease diagnosed in these sheep, and the major cause of direct animal losses in the two flocks. Moderate to severe lesions associated with MV were found in 52% and 80% of the sheep, respectively, affecting the lungs, brain and/or mammary glands. Despite the similarity of the two flocks under study in terms of breed, number of animals, geographical proximity, and inter-change of rams, a striking difference was observed regarding the clinical presentation of the disease: in one flock the respiratory form was dominant while in the other 70% of animals died or were culled because of neurological signs.

Small ruminant lentiviruses in Jordan: evaluation of sheep and goat serological response using recombinant and peptide antigens.

Small ruminant lentiviruses infect sheep and goats worldwide, causing chronic progressive diseases and relevant economic losses. Disease eradication and prevention is mostly based on serological testing. The goal of this research was to investigate the presence of the small ruminant lentiviruses (SRLVs) in Jordan and to characterize the serological response in sheep and goat populations. A panel of sera were collected from flocks located in Northern Jordan and Jordan Valley. The samples were tested using three ELISA assays: a commercially available ELISA based on p25 recombinant protein and transmembrane peptide derived from British maedi-visna virus (MVV) EV1 strain, an ELISA based on P16-P25 recombinant protein derived from two Italian strains representative of MVV- and caprine arthritis encephalitis virus (CAEV)-like SRLVs, and an ELISA based on SU5 peptide from the same two Italian isolates. The results indicate that both MVV- and CAEV-like strains are present in Jordan and that the majority of the viruses circulating among sheep and goat populations belong to the MVV-like genotype.

The origin of lentivirus research: Maedi-visna virus.

Maedi and visna are contagious sheep diseases which were introduced into Iceland in 1933 by imported sheep of Karakul breed. Maedi, a slowly progressing pneumonia, and the central nervous system disease visna were shown to be transmissible in sheep and most likely caused by a virus. In 1957, visna virus was isolated in tissue culture from sheep brain and maedi virus was isolated the following year from sheep lungs. Both viruses showed similar cytopathic effect in tissue culture. Electron microscope studies of ultrathin sections from visna virus infected cells demonstrated spherical particles, 70-100 nm in diameter, which were formed by budding from the cell membrane. Later studies showed identical particles in maedi virus infected cultures. These, and several other comparative studies, strongly indicated that maedi and visna were caused by strains of the same virus, later named maedi-visna virus (MVV). Comparative studies in tissue culture suggested that MVV was related to RNA tumor viruses of animals, the oncornaviruses. This was later supported by the finding that MVV is an RNA virus. A few months after reverse transcriptase was demonstrated in oncornaviruses, the enzyme was also found in MVV virions. Thus, MVV was classified as a retrovirus together with the oncornaviruses. However, MVV is not oncogenic in vivo or in vitro and was in 1975 placed in a subgroup of retroviruses named lentiviruses, which cause cytopathic effect in vitro and slowly progressing inflammatory disease in animals, but are nononcogenic. In the early 1980s, the causative agent of AIDS was found to be a non-oncogenic retrovirus and was classified as a lentivirus. Thus, HIV became the first human lentivirus.

Virological and phylogenetic characterization of attenuated small ruminant lentivirus isolates eluding efficient serological detection.

Three field isolates of small ruminant lentiviruses (SRLVs) were derived from a mixed flock of goats and sheep certified for many years as free of caprine arthritis encephalitis virus (CAEV). The phylogenetic analysis of pol sequences permitted to classify these isolates as A4 subtype. None of the animals showed clinical signs of SRLV infection, confirming previous observations which had suggested that this particular subtype is highly attenuated, at least for goats. A quantitative real time PCR strategy based on primers and probes derived from a highly variable env region permitted us to classify the animals as uninfected, singly or doubly infected. The performance of different serological tools based on this classification revealed their profound inadequacy in monitoring animals infected with this particular SRLV subtype. In vitro, the isolates showed differences in their cytopathicity and a tendency to replicate more efficiently in goat than sheep cells, especially in goat macrophages. By contrast, in vivo, these viruses reached significantly higher viral loads in sheep than in goats. Both env subtypes infected goats and sheep with equal efficiency. One of these, however, reached significantly higher viral loads in both species. In conclusion, we characterized three isolates of the SRLV subtype A4 that efficiently circulate in a mixed herd of goats and sheep in spite of their apparent attenuation and a strict physical separation between goats and sheep. The poor performance of the serological tools applied indicates that, to support an SRLV eradication campaign, it is imperative to develop novel, subtype specific tools.

Patterns of lesion and local host cellular immune response in natural cases of ovine maedi-visna.

This study investigates the nervous form of ovine maedi-visna by histological and immunohistochemical techniques. The aim was to study the lesion types and the local cellular immune response related to each lesion type, and the possible relationship between these parameters. Thirty-four Assaf ewes were studied, 29 of which had shown nervous signs. Microscopical lesion patterns were described according to location, extent and predominance of inflammatory cell type. Immunohistochemical labelling of T cells (CD3(+), CD4(+), CD8(+) and cells expressing the γδ form of the T-cell receptor), B cells and macrophages revealed clear differences between the lesion patterns. Two main lesion types were described. Lymphocytic lesions had areas of mild-moderate injury characterized by a predominance of infiltrating T cells. Histiocytic lesions were more severe and had extensive areas of malacia and dominant infiltration by macrophages and B cells. Each animal had a unique lesion pattern and these differences could be due to individual resistance to the progression of infection. The lymphocytic lesions appear to represent initial or latent phases of slow progression, in which the animal presents some natural resistance to the infection. The histiocytic pattern may reflect a poor immune response or a greater virulence of the viral strain.

Leptospirosis as the most frequent infectious disease impairing productivity in small ruminants in Rio de Janeiro, Brazil.

Despite the importance of small ruminants breeding in developing countries, milk/meat productivity remains unsatisfactory. Infectious diseases, such as leptospirosis, brucellosis, and small ruminant lentiviruses (SRLVs), contribute to this scenario. The objective of the present study was to determine the role of each of these diseases in the productivity of small ruminants breeding in Rio de Janeiro, Brazil. In goats, 343 samples were tested for leptospirosis, 560 for Brucella abortus, and 506 for caprine arthritis-encephalitis (CAE), whereas in sheep, 308 samples were tested for leptospirosis, 319 for B. abortus, 374 for Brucella ovis, and 278 for Maedi-Visna (MV). Regarding leptospirosis, 25.9% of goats and 47.4% sheep were seroreactive, with serovar Hardjo the most prevalent in both species. Anti-B. abortus agglutinins were found in 0.7% of all samples, exclusively in goats. In relation to SRLVs, 8.6% of goats and 3.2% of sheep samples were positive for CAE and MV, respectively. Leptospirosis was the major infectious problem in the small ruminants sampled and may contribute to impaired productivity of these animals.

Maedi-visna virus infection in Karayaka and Amasya Herik breed sheep from provinces in northern Turkey.

Maedi-visna is an important virus infection of sheep having prolonged incubation period (slow disease) and reflecting two distinct forms clinically and pathologically. In this study, the presence of MVV was investigated serologically in 58 Amasya Herik sheep breed and 525 Karayaka sheep breed. Seropositivity rates in Amasya Herik sheep breed and Karayaka sheep breed were detected as 69.0% and 18.5%, respectively. MVV antibodies were found in 137 of 583 serum samples (23.5%). Positivity rates for the provinces varied and were as follows: Samsun 19.4%, Sinop 15.4%, Ordu 25.8%, Trabzon 26.7%, Rize 36.7%, Amasya 69.0% and Tokat 35.0%, however no antibody response was detected in all of the sheep in Giresun province.

Visna/Maedi virus genetic characterization and serological diagnosis of infection in sheep from a neurological outbreak.

An extensive outbreak characterized by the appearance of neurological symptoms in small ruminant lentivirus (SRLV) infected sheep has been identified in Spain, but the genetic characteristics of the strain involved and differential diagnostic tools for this outbreak remain unexplored. In this work, 23 Visna-affected naturally infected animals from the outbreak, 11 arthritic animals (both groups presenting anti-Visna/Maedi virus serum antibodies), and 100 seronegative animals were used. Eight of the Visna-affected animals were further studied post-mortem by immunohistochemistry. All had lesions in spinal cord, being the most affected part of the central nervous system in six of them. A representative strain of the outbreak was isolated. Together with other proviral sequences from the outbreak the virus was assigned to genotype A2/A3. In vitro culture of the isolate revealed that viral production was slow/low in fibroblast-like cells but it was high in blood monocyte-derived macrophages. The long terminal repeat (LTR) of the viral genome of this isolate lacked an U3-duplication, but its promoter activity in fibroblast-like cells was normal compared to other strains. Thus, viral production could not be inferred from the LTR promoter activity in this isolate. Analysis of the viral immunodominant epitopes among SRLV sequences of the outbreak and other known sequences allowed the design of a synthetic SU peptide ELISA that detected the Visna affected animals, representing a tool of epidemiological interest to control viral spread of this highly pathogenic strain.

Maedi in slaughtered sheep: a pathology and polymerase chain reaction study in southwestern Iran.

Maedi-visna (MV) is an important slow viral disease of sheep leading to a progressive lymphoproliferative disease. It affects multiple organs primarily the lungs, where it causes interstitial pneumonia (maedi). In this study, the lungs of 1,000 sheep carcasses were grossly inspected and those suspected to have maedi were studied at histopathological and molecular levels. A polymerase chain reaction (PCR) technique that amplified a 291-base pair DNA in the long terminal repeat (LTR) sequence of MV provirus was conducted on all the 50 suspected lungs together with 10 normal appearing lungs as controls. Amplicons of the expected size were detected in 11 (n=11/50) suspected sheep, and one of the 10 control sheep. Histopathologic study of the pulmonary lesions of all 11 (n=11/11) positive sheep showed MV lesions, including hyperplasia of the perivascular and peribronchiolar lymphoid cells, interstitial lymphoplasmacytic infiltration and smooth muscle hyperplasia and the histopathologic findings were correlated with PCR results. In contrast, the tissue sections of control animals were almost normal at histopathological level; however, PCR technique demonstrated that one of them was affected by maedi. This study showed that the LTR-PCR had high specificity and sensitivity in diagnosis of this viral infection. This study is the first to evaluate the prevalence of MV virus infection in sheep in Iran.

Propagating and detecting an infectious molecular clone of maedi-visna virus that expresses green fluorescent protein.

Maedi-visna virus (MVV) is a lentivirus of sheep, causing slowly progressive interstitial pneumonia and encephalitis. The primary target cells of MVV in vivo are considered to be of the monocyte lineage. Certain strains of MVV can replicate in other cell types, however. The green fluorescent protein is a commonly used marker for studying lentiviruses in living cells. We have nserted the egfp gene into the gene for dUTPase of MVV. The dUTPase gene is well conserved in most lentivirus strains of sheep and goats and has been shown to be important in replication of CAEV. However, dUTPase has been shown to be dispensable for replication of the molecular clone of MVV used in this study both in vitro and in vivo. MVV replication is strictly confined to cells of sheep or goat origin. We use a primary cell line from the choroid plexus of sheep (SCP cells) for transfection and propagation of the virus. The fluorescent MVV is fully infectious and EGFP expression is stable over at least 6 passages. There is good correlation between measurements of TCID50 and EGFP. This virus should therefore be useful for rapid detection of infected cells in studies of cell tropism and pathogenicity in vitro and in vivo.

[Comparative characteristics of the biological properties of small ruminant lentiviruses].

The infections caused by small ruminant lentiviruses include diseases, such as Maedi-Visna (MV) and caprine arthritis-encephalitis (CAE). According to phylogenetic findings and their common origination, small ruminant lentiviruses were divided into Groups A, B, C, D, and E. Cultivation of the lentiviruses displayed the cytopathic effect of the CAE virus strain 75 G-63 in the primary culture of goatling synovial membrane cells, which was shown by monolayer destruction and polynuclear cell formation; this was uncharacteristic for M-88, K-796, and Tverskoy strains. A high homology was found for the Tverskoy strain with Group B small ruminant lentiviruses and the M-88 and K-796 strains with their Group A.

Molecular characterization and phylogenetic analysis of small ruminant lentiviruses isolated from Canadian sheep and goats.

BACKGROUND: Small Ruminant Lentiviruses (SRLV) are widespread in Canadian sheep and goats and represent an important health issue in these animals. There is however no data about the genetic diversity of Caprine Arthritis Encephalitis Virus (CAEV) or Maedi Visna Virus (MVV) in this country. FINDINGS: We performed a molecular and phylogenetic analysis of sheep and goat lentiviruses from a small geographic area in Canada using long sequences from the gag region of 30 infected sheep and 36 infected goats originating from 14 different flocks. Pairwise DNA distance and phylogenetic analyses revealed that all SRLV sequences obtained from sheep clustered tightly with prototypical Maedi visna sequences from America. Similarly, all SRLV strains obtained from goats clustered tightly with prototypical US CAEV-Cork strain. CONCLUSIONS: The data reported in this study suggests that Canadian and US SRLV strains share common origins. In addition, the molecular data failed to bring to light any evidence of past cross species transmission between sheep and goats, which is consistent with the type of farming practiced in this part of the country where single species flocks predominate and where opportunities of cross species transmissions are proportionately low.