Visna Research Articles

Characterization of ovine TLR7 and TLR8 protein coding regions, detection of mutations and Maedi Visna virus infection

Toll-like receptors (TLRs) 2, 3, 4, 7, 8 and 9 play a crucial role in the recognition of viral entities and modulation of the innate immune system. This work presents sequence analysis of ovine TLR7 and TLR8 genes, depicts novel mutations and describes frequencies of mutations in Maedi Visna infected and healthy sheep. Totally 48 samples of the breed Tsigai were analyzed for the presence of mutations. Within 20 mutations, 14 were silent whereas 6 were missense. The frequencies of missense mutations in the Maedi Visna infected compared to non-infected sheep were: Lys115Glu ( P - 0.766, F-test), Asn117 ( P - 0.380) and Lys818Arg ( P - 0.739). These three mutations were localized in extra LRR (lucine rich repeat) region of TLR7, while mutation Ile73Leu ( P - 0.498) was located within LRR2 motif. Both mutations in TLR8, Asn165Lys ( P - 1.0) and Tyr349His ( P - 0.700), were present in extra LRR region. The secondary structure analysis of ovine TLR7 and TLR8 revealed conserved LRR motif structure, however with some irregularities compared to cattle and human. Transmembrane domains of TLR7 and TLR8 showed 100% homology between sheep and cattle wherein no mutations were found. In both TLRs TIR domains were highly conserved with occurrence of 4 silent mutations. Mutations in TLR7 and TLR8 may play an important role as predisposition factor for Maedi Visna infection. Considering the sequence homology among sheep, cattle and human genes encoding TLR7 and TLR8, we predict their similar function, localization and downstream signaling.

Non-maternal transmission is the major mode of ovine lentivirus transmission in a ewe flock: A molecular epidemiology study

Transmission of ovine progressive pneumonia virus (OPPV), a lentivirus of sheep, occurs through both maternal and non-maternal means. Currently, the contribution of each route to the overall flock OPPV prevalence is poorly understood since previous serological epidemiologic studies lacked the ability to accurately track routes of transmission within an infected flock. In this study, the amount of maternal OPP transmission was assessed in a naturally infected ewe flock by applying molecular analyses to proviral sequences derived from peripheral blood leukocytes of OPP positive dam–daughter pairs ( N = 40). Both proviral envelope ( env) and long terminal repeat (LTR) sequences, separately and combined, were utilized in the following 2 sequence analysis methods: phylogenetic analysis and pairwise distance calculations. True maternal transmission events were defined as agreement in 2 out of the 2 sequence analysis methods. Using this criterion, proviral env sequences resulted in a 14.3% maternal transmission frequency, and proviral LTR sequences resulted in a 10% maternal transmission frequency. Both proportions of maternal transmission varied significantly from equality ( P < 0.0001). This indicates that the remaining 85.7–90% of daughters are infected via non-maternal transmission. This is also the first study to calculate the OPP proviral rate of change for the env gene and LTR promoter. Accurately defining the routes of OPPV transmission provides critical epidemiological data supporting management intended to reduce flock transmission and viral dose.

Maedi-Visna virus was detected in association with virally exposed IVF-produced early ewes embryos

The objective of this study was to determine whether MVV can be transmitted by ovine embryos produced in vitro and whether the zona pellucida (ZP) provides any protection against MVV infection. Zona pellucida (ZP)-intact and ZP-free embryos, produced in vitro, at the 8–16 cell stage, were cocultured for 72h in an insert over an ovine oviduct epithelial cell (OOEC)-goat synovial membrane (GSM) cell monolayer that had been previously infected with MVV (K1514 strain). The embryos were then washed and transferred to either direct contact or an insert over a fresh GSM cell monolayer for 6 h. The presence of MVV was detected using RT-PCR on the ten washing fluids and by the observation of typical cytopathic effects (CPE) in the GSM cell monolayer, which was cultured for 6 weeks. This experiment was repeated 4 times with the same results: MVV viral RNA was detected using RT-PCR in the first three washing media, while subsequent baths were always negative. Specific cytopathic effects of MVV infection and MVV-proviral DNA were detected in GSM cells that were used as a viral indicator and cocultured in direct contact or as an insert with MVV-exposed ZP-free embryos. However, no signs of MVV infection were detected in cells that were cocultured with exposed ZP-intact or non-exposed embryos. This study clearly demonstrates that (i) in vitro, ZP-free, early ovine embryos, which had been exposed to 10 3 TCID 50/m MVV in vitro, are capable of transmitting the virus to susceptible GSM target cells, and that (ii) the IETS recommendations for handling in vivo produced bovine embryos (use of ZP-intact embryos without adherent material and performing ten washes) are effective for the elimination of in vitro MVV infection from in vitro produced ovine embryos. The absence of interaction between ZP-intact embryos and MVV suggests that the in vitro produced embryo zona pellucida provides an effective protective barrier.

Lentiviral Vif Degrades the APOBEC3Z3/APOBEC3H Protein of Its Mammalian Host and Is Capable of Cross-Species Activity

All lentiviruses except equine infectious anemia virus (EIAV) use the small accessory protein Vif to counteract the restriction activity of the relevant APOBEC3 (A3) proteins of their host species. Prior studies have suggested that the Vif-A3 interaction is species specific. Here, using the APOBEC3H (Z3)-type proteins from five distinct mammals, we report that this is generally not the case: some lentiviral Vif proteins are capable of triggering the degradation of both the A3Z3-type protein of their normal host species and those of several other mammals. For instance, SIV(mac) Vif can mediate the degradation of the human, macaque, and cow A3Z3-type proteins but not of the sheep or cat A3Z3-type proteins. Maedi-visna virus (MVV) Vif is similarly promiscuous, degrading not only sheep A3Z3 but also the A3Z3-type proteins of humans, macaques, cows, and cats. In contrast to the neutralization capacity of these Vif proteins, human immunodeficiency virus (HIV), bovine immunodeficiency virus (BIV), and feline immunodeficiency virus (FIV) Vif appear specific to the A3Z3-type protein of their hosts. We conclude, first, that the Vif-A3Z3 interaction can be promiscuous and, second, despite this tendency, that each lentiviral Vif protein is optimized to degrade the A3Z3 protein of its mammalian host. Our results thereby suggest that the Vif-A3Z3 interaction is relevant to lentivirus biology.

Detection of Antibodies against Glycoprotein of Maedi-Visna Virus Released as Soluble Antigen in Cell Cultures

Summary A glycoprotein of Maedi-Visna virus released as a soluble antigen in cell cultures was prepared by affinity chromatography on Con A Sepharose. By comparing it serologically with other virus-specific antigens an increase of the sensitivity was observed. Furthermore, long-time studies conducted with sheep sera over a period of 7 years showed an increase and decline of the titer of complement fixing antibodies, while precipitating antibodies against the whole virus, as well as the viral glycoprotein, could be detected continuously. In sera of Merino sheep generally free of clinical symptoms antibodies against Maedi-Visna virus were detected in a high percentage. Zusammenfassung Nachweis von Antikörpern gegen lösliches, in Zellkultur-Überstand entlassenes Glykoprotein des Maedi/Visna-Virus Es wurde ein Glykoprotein des Maedi/Visna-Virus, das als lösliches Antigen in den Kultur-Überstand entlassen wird, nach Konzentrierung mit Ammoniumsulfat durch Affinitätschromatographie an ConA-Sepharose gewonnen. Im Vergleich mit anderen virusspezifischen Antigenen wurde eine erhöhte Empfindlichkeit bei serologischen Reaktionen festgestellt. Langzeitstudien, die mit Schafseren über einen Zeitraum von 7 Jahren durchgeführt wurden, zeigten eine Zunahme und Abnahme des Titers der komplementbindenden Antikörper, während präzipitierende Antikörper sowohl gegen das Gesamtvirus als auch gegen das virale Glykoproteid kontinuierlich nachgewiesen werden konnten. Außerdem wurden in Seren von Merinoschafen, die in der Regel keine klinischen Krankheitssymptome zeigen, in einem hohen Prozentsatz Antikörper gegen Maedi/Visna-Virus nachgewiesen. Résumé Mise en évidence d'anticorps contre un glycoprotéide soluble du virus Maedi/Visna trouvé dans le surnageant d'une culture cellulaire On a obtenu un glycoprotéide du virus Maedi/Visna sous la forme d'un antigène soluble dans le surnageant d'une culture cellulaire après concentration avec du sulfate d'ammonium et en chromatographie d'affinité sur sepharose Con A. Une sensibilité augmentée dans des réactions sérologiques par rapport à d'autres antigènes spécifiques a été établie. Des études qui ont été faites avec des sérums de moutons sur une période de 7 ans ont montré une augmentation et une diminution du titre des anticorps fixant le complément alors que des anticorps précipitants contre le virus complet et le glycoprotéide viral ont pu être démontrés de façon continue. Un fort pourcentage d'anticorps contre le virus Maedi/Visna ont été mis en évidence dans des sérums de moutons Mérinos qui ne présentent en général aucun symptôme clinique de la maladie. Resumen Identificación de anticuerpos frente a un glucoproteido soluble, desprendido en el sobrenadante de cultivos celulares del virus Maedi/Visna Se obtuvo un glucoproteido del virus Maedi/Visna, que se desprende como antígeno soluble en el sobrenadante cultural, tras concentración con sulfato amónico, mediante cromatografía de afinidad en Sepharosa-ConA. En comparación con los otros antígenos específicos de virus, se estableció una sensibilidad aumentada en las reacciones serológicas. Estudios de duración larga, llevados a cabo con sueros ovinos por un espacio de tiempo de 7 años, mostraron un aumento y una disminución del título de los anticuerpos fijadores del complemento, mientras que se pudieron identificar continuamente anticuerpos precipitantes tanto frente al virus total como frente al glucoproteido viral. Además se pudieron identificar en sueros de ovejas merinas, que por regla general no mostraban síntomas clínicos de enfermedad, en un porcentaje muy elevado anticuerpos frente al virus Maedi/Visna.

Tissue tropism and promoter sequence variation in caprine arthritis encephalitis virus infected goats

Caprine arthritis encephalitis virus is a lentivirus that infects goats and is closely related to maedi-visna virus of sheep. Infection with CAEV results in multiple discrete disease manifestations in goats which can include chronic arthritis, mastitis, pneumonia or encephalomyelitis. Presently, no satisfactory mechanistic rationale for viral tropism has been put forward. We propose that specific sequences in the lentiviral promoter (U3 region of the viral long terminal repeat) are associated with viral tissue tropism and subsequent disease expression. A total of 41 distinct CAE viral promoter regions were amplified, sequenced and phylogenetically compared from the tissues of 24 CAEV-infected goats demonstrating a variety of disease manifestations. Phylogenetically, we identified no tendency for clustering of these promoter sequences into tissue-specific groups. These results therefore do not provide evidence for the study hypothesis. However, multiple motifs within the U3 promoter region were highly conserved both within the entire collection of sequences and within tissue-specific groups.

Construction and characterization of an infectious molecular clone of maedi-visna virus that expresses green fluorescent protein

The construction of a molecular clone of maedi-visna virus (MVV) expressing the enhanced green fluorescent protein (EGFP) is described. The egfp gene was inserted into the gene for dUTPase since it has been shown that dUTPase is dispensable for MVV replication both in vitro and in vivo. MVV-egfp is infectious and EGFP expression is stable over at least six passages. This fluorescent virus will be a useful tool for monitoring MVV infections.

Detection of PrPScin lung and mammary gland is favored by the presence of Visna/maedi virus lesions in naturally coinfected sheep

There are few reports on the pathogenesis of scrapie (Sc) and Visna/maedi virus (VMV) coinfections. The aim of this work was to study in vivo as well as post mortem both diseases in 91 sheep. Diagnosis of Sc and VMV infections allowed the distribution of animals into five groups according to the presence (+) or absence (−) of infection by Sc and VMV: Sc−/VMV−, Sc−/VMV+, Sc+/VMV− and Sc+/VMV+. The latter was divided into two subgroups, with and without VMV-induced lymphoid follicle hyperplasia (LFH), respectively. In both the lung and mammary gland, PrPSc deposits were found in the germinal center of hyperplasic lymphoid follicles in the subgroup of Sc+/VMV+ having VMV-induced LFH. This detection was always associated with (and likely preceded by) PrPSc observation in the corresponding lymph nodes. No PrPSc was found in other VMV-associated lesions. Animals suffering from scrapie had a statistically significantly lower mean age than the scrapie free animals at the time of death, with no apparent VMV influence. ARQ/ARQ genotype was the most abundant among the 91 ewes and the most frequent in scrapie-affected sheep. VMV infection does not seem to influence the scrapie risk group distribution among animals from the five groups established in this work. Altogether, these data indicate that certain VMV-induced lesions can favor PrPSc deposits in Sc non-target organs such as the lung and the mammary gland, making this coinfection an interesting field that warrants further research for a better comprehension of the pathogenesis of both diseases.

Risk factors associated with the occurrence of undesired effects in sheep and goats after field vaccination with modified-live vaccine against bluetongue virus serotypes 2, 4 and 16

In the 2004, the Sardinian bluetongue (BT) vaccination campaign used the combination of monovalent BTV-2, BTV-4 and BTV-16 modified-live vaccines manufactured by the Onderstepoort Biological Products in South Africa. Following vaccination, some herds showed temperature, oedema, lameness, hyperaemia and decrease in milk production, and some others remained perfectly healthy. This study aimed to evaluate whether important factors present in the herd at the time of vaccination could be associated to the occurrence of undesired effects observed after immunisation with BTV modified-live vaccines. A sample of 17 sheep and 4 goat flocks, for a total of 670 animals, were included in the study and risk factors such as presence of most important parasitic, bacterial and viral diseases as well as anomalies of biochemical and haematological parameters were associated to the presence or absence of side effects. For each factor the relative risk and 95% confidence interval were calculated. Following vaccination, bluetongue-like symptoms were observed in 13 flocks. In these flocks, a higher (P<0.05) proportion of animals had viraemia and showed higher titers to BTV-16 after immunisation. Positive association (RR=2.50, 1.17–5.04) was also found between flocks in which undesired effect were observed and positive serology against Maedi–Visna virus. On the contrary, presence of BTV genome fractions in the blood of animals at the time of vaccination was found to be protective (RR=0.7, 0.58–0.84) to the occurrence of undesired effect subsequent to BTV vaccination.

MHC class II DRB1 gene polymorphism in the pathogenesis of Maedi–Visna and pulmonary adenocarcinoma viral diseases in sheep

Ovine pulmonary adenocarcinoma (OPA) and Maedi-Visna (Maedi) are two chronic respiratory diseases of retroviral origin which occur worldwide. It is known that different host genetic factors influence the outcome of viral infections. To determine if variation in the Mhc-DRB1 gene was associated with progression to these ovine diseases, sheep lungs with and without OPA and Maedi lesions were collected. A sequence-based method was applied and 40 different alleles were detected in the sample analysed. In the allele-by-allele association analysis, allele DRB1*0325 had a significant association with susceptibility to Maedi (P = 0.045). For OPA, DRB1*0143 and DRB1*0323 were significantly associated with susceptibility (P = 0.024 and P = 0.029), and allele DRB1*0702 was significantly associated with resistance (P = 0.012). Based on these results, the Mhc-DRB1 alleles were classified by effect in three categories-susceptible (S), resistant (R) and neutral (N)-and animals were reassigned the genotypes as S/S, S/R, S/N, R/R, R/N and N/N. In a second analysis, penalised logistic regression models including a flock effect were run. In Maedi, significant association was detected for the N/S heterozygote (P = 0.0007), but not for the S/S homozygote, probably as a result of the low number of S/S animals. In OPA, association was detected for both the S/S and R/R homozygotes (P = 0.005 and P = 0.047). This allele grouping method may be applied in association studies with highly variable genes. This is the first study demonstrating significant associations between sheep Mhc-DRB1 alleles and susceptibility to OPA and Maedi. Therefore, both diseases are suitable candidates for more comprehensive genetic studies.

Sero-epidemiological study on Maedi-Visna in selected areas of Ethiopia

The study was conducted to verify the existence of Maedi-Visna virus infection (Ovine Progressive Pneumonia- OPP) in exotic sheep breed in selected areas of Ethiopia. ELISA and Hematoxylin & Eosin (HE) staining techniques were employed to examine the serum and tissue samples respectively. ELISA test of serum samples showed 88%, 19%, 10%, 6%, and 0.8% infection rate for Debre Berhan sheep breeding center, and Arsi, Bale, North Omo and Gurage zones respectively. At necropsy 11% (4/36) of the sheep examined had characteristic gross pathological lung lesions of Maedi/OPP and 33% (12/36) indicated the presence of the disease through histopathological examinations. The major histopathological findings were peribronchial and interstitial lymphocytic infiltrations and/or follicle-like aggregations, interstitial connective tissue proliferation, hyperplasia of the smooth muscles in the ducts of terminal bronchioles and alveoli. The present findings provide a clear evidence for the dissemination of Maedi-Visna virus following the distribution of exotic rams from the breeding and multiplication center. Therefore, survey in other areas is also required to have broad picture of the disease in the country which will help to design a practical control strategy of the disease at the national level. Keywords: Ethiopia, exotic sheep breeds, maedi-visna, sero-epidemiology

Maedi-visna virus in Turkish sheep: a preliminary serological survey using ELISA tests

The maedi-visna virus (MVV) is distributed worldwide and, to date, no epidemiological surveys have been carried out using ELISA testing in Turkey. The aims of this study were as follows: i) to verify the diagnostic performance of a home-made ELISA test (HM-ELISA) using Turkish ovine sera in comparison with other commercially available ELISA tests, and ii) to perform a preliminary epidemiological survey in İstanbul province. The MVV seroprevalence in İstanbul province was 15.3%. Older sheep were 5 times more likely to be positive than younger animals, ewes were 3 times more likely to be positive than rams, and all the Red Karaman and White Karaman sheep tested were seronegative. The performance of the HM-ELISA and that of the other commercial tests using Turkish ovine serum samples was similar; therefore, the HM-ELISA test is suitable for use in extensive epidemiological surveys and eradication programs in Turkey.

Lung Tumor Development and Spontaneous Regression in Lambs Coinfected With Jaagsiekte Sheep Retrovirus and Ovine Lentivirus

Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring and experimentally inducible lung cancer of sheep caused by Jaagsiekte sheep retrovirus (JSRV). The first aim of this study was to monitor the development of OPA with minimally invasive, real-time observations of animals experimentally infected with JSRV as well as ovine lentivirus (maedi-visna virus). Worldwide, simultaneous infection of sheep with these 2 retroviruses is a common occurrence, naturally and experimentally; consequently, the lung tumor homogenates used as inocula contained both viruses. Following inoculation, computed tomography was used to detect tumor nodules early, before the onset of clinical signs, and to monitor tumor advancement. However, not only was OPA disease progression observed, but the apparent spontaneous regression of OPA was witnessed. In fact, regression was more common than progression following JSRV inoculation of neonatal lambs. Immune responses were detected, particularly involving CD3(+) T cells and the production of antibodies against JSRV that may mediate the spontaneous regression of JSRV-induced OPA. The second aim of this study was to determine whether OPA tumors harbor genetic alterations similar to those found in human lung adenocarcinoma. No mutations were found in the tyrosine kinase domain of the epidermal growth factor receptor, KRAS codons 12 and 13, or the DNA-binding domain of p53 in tumor DNA from naturally occurring and experimentally-induced OPA cases. Overall, the genetic profile combined with the disease development data provides further important characterization of OPA and describes, for the first time, spontaneous regression of OPA tumors in experimentally infected sheep.

Ovine Progressive Pneumonia Virus Capsid Antigen as Found in CD163- and CD172a-Positive Alveolar Macrophages of Persistently Infected Sheep

In situ detection of ovine progressive pneumonia virus (OPPV) and the phenotypic identification of the cells that harbor OPPV have not been described for the OPPV-affected tissues, which include lung, mammary gland, synovial membranes of the carpal joint, and choroid plexus of the brain. In this study, the authors first developed a single enzyme-based automated immunohistochemical (IHC) analysis for detection of OPPV capsid antigen (CA) on OPPV-affected tissues, using 2 anti-CAEV CA monoclonal antibodies, 5A1 and 10A1, and 2 enzyme-based IHC systems. Out of 10 naturally and persistently OPPV-infected ewes, OPPV CA was detected in intercellular regions of the carpal synovial membrane of 1 ewe, in cells resembling alveolar macrophages and pulmonary interstitial macrophages in lung tissue of 3 ewes, and in mammary alveolar cells of 1 ewe. Furthermore, dual enzyme-based automated IHC analyses revealed that OPPV CA was predominantly detected in CD172a- or CD163-positive alveolar macrophages of the lungs and mammary gland. That anti-inflammatory (CD163) and downregulatory (CD172a) types of alveolar macrophage harbor OPPV CA leads to the possibility that during persistent infection with OPPV, the host alveolar macrophage might serve to limit inflammation while OPPV persists undetected by the host adaptive immune response in the lung and mammary gland.

Evaluation of a Caprine Arthritis-Encephalitis Virus/Maedi-Visna Virus Indirect Enzyme-Linked Immunosorbent Assay in the Serological Diagnosis of Ovine Progressive Pneumonia Virus in U.S. Sheep

A caprine arthritis-encephalitis virus (CAEV)/maedi-visna virus (MVV) indirect enzyme-linked immunosorbent assay (iELISA) was validated with samples from U.S. sheep and by the use of radioimmunoprecipitation as the standard for comparison. The sensitivity and the specificity were 86.0% (+ or - 5.8%) and 95.9% (+ or - 2.9%), respectively. The iELISA format and phylogenetic differences based on the MVV gag sequence contribute to the reduced sensitivity.

Effects of housing on the incidence of visna/maedi virus infection in sheep flocks

The incidence of seroconversion to visna/maedi virus (VMV) infection and its relationship with management and sheep building structure was investigated in 15 dairy sheep flocks in Spain during 3-7years. Incidence rates were 0.09 per sheep-year at risk in semi-intensive Latxa flocks and 0.44 per sheep-year at risk in intensive Assaf flocks and was greatest for the one year old Assaf replacement flock. Separate multivariable models developed for replacement and adult flocks indicated that in both cases seroconversion was strongly associated to direct contact exposure to infected sheep and to being born to a seropositive dam. The latter effect was independent of the mode of rearing preweaning and the risk of seroconversion was similar for sheep fed colostrum and milk from a seropositive or a seronegative dam. These results are further evidence of the efficiency of horizontal VMV transmission by close contact between sheep and also suggest a inheritable component of susceptibility and resistance to infection. In contrast, indirect aerogenous contact with seropositive sheep was not associated with seroconversion as evidenced in replacement sheep housed in separate pens in the same building as adult infected sheep for one year. Consequently, VMV may not be efficiently airborne over short distances and this is important for control of infection. Moreover, there was no relationship between seroconversion and shed open areas. The latter could be related to having examined few flocks in which high infection prevalence dominated the transmission process while ventilation, may depend on a variety of unrecorded factors whose relationship to infection needs to be further investigated.

Soroprevalência de Maedi-Visna em ovinos na região de Araçatuba, SP

ABSTRACT The seroprevalence of Maedi-Visna in sheep from Aracatuba region – SP, was determined and correlated to age, gender, breed, or sheep production systems. Blood samples were collected from 444 sheep, aging from two to 12 year-old. Both sexes and different breeds were sampled in 20 farms of this region. Physical examination was performed in all animals. Agar gel immunodiffusion test kit was used to diagnose in serum samples. Twelve animals, from five different farms, were AGID positive, yielding a seroprevalence of 2.7%, with no correlation among breed, gender, or sheep production systems and the detection of the disease. No animal considered positive for Maedi-Visna showed clinical signs compatible with Maedi-Visna. Keywords: sheep, Maedi-Visna, serology, AGID AGRADECIMENTOS A FAPESP pela concessao da bolsa de iniciacao cientifica (processo n.06/51374-4), a autora H.P. Paulo. REFERENCIAS BIBLIOGRAFICAS ARAUJO, S.A.C.; DANTAS, T.V.M.; SILVA,J.B.A. et al. Identificacao de Maedi-Visna virus em pulmao de ovinos infectados naturalmente.

ANTICORPOS CONTRA O VÍRUS DA MAEDI-VISNA EM REBANHOS OVINOS DA MICRORREGIÃO DE JUAZEIRO - BAHIA

To detect the presence of Maedi-Visna virus in sheep in the Juazeiro microregion, Bahia, 919 serum samples were evaluated by an agar gel immunodiffusion test (AGID). The samples were collected in eight of the cities that make up this microregion: Juazeiro, Sento Se, Sobradinho, Pilao Arcado, Campo Alegre de Lourdes, Remanso, Casa Nova and Curaca. A positive reaction to AGID was evidenced in 0,34% of the sheep sampled. We concluded that antibodies against sheep lentivirus are present in this microregion, which is probably due to the predominance of native animals in the investigated farms.

SOROPREVALÊNCIA DA PNEUMONIA PROGRESSIVA OVINA (MAEDI-VISNA) NA REGIÃO DE BOTUCATU – SP

The present study aimed to verify the prevalence of the ovine progressive pneumonia in Botucatu region by agar gel immunodiffusion test (AGID). Serum samples of 400 sheep from eight specific farms for meat, with type of semi-intensive breeding of different areas. All the samples tested were negative to Maedi-Visna. The analysis of results was discordant with studies made in others Brazilians states, where the prevalence of the disease comes increasing progressively. KEY WORDS: AGID, lentivirus, sheep.

Visna/maedi virus serology in sheep: Survey, risk factors and implementation of a successful control programme in Aragón (Spain)

A serological survey of Visna/maedi virus (VMV) infection involving 274,048 sheep from 554 flocks was undertaken during 2002-2007 in Aragón, North-East Spain. One hundred and two of these flocks enrolled in a VMV control programme to reduce seroprevalence by selecting replacement lambs from seronegative dams and gradual culling of seropositive sheep. Twenty-five flocks were also visited to collect flock management and housing data. All study flocks had seropositive animals and 52.8% of animals tested were seropositive. Among flocks that joined the control programme 66 adopted the proposed measures and reduced seroprevalence significantly by between 26.1% and 76.9% whereas the remaining 36 flocks did not apply the measures and seroprevalence significantly increased. Seroprevalence increased with flock size and the number of days the sheep were housed, and decreased with increasing weaning age and shed open area, suggesting a reduced risk of VMV infection in sheep associated with better ventilation. At the end of the period, 24 flocks were certified as VMV-controlled with a seroprevalence <5%, and seven as VMV-free with 0% seroprevalence. These are the first officially recognised VMV-free flocks in Spain and represent a nucleus of VMV-free replacement animals for other flocks. Moreover, they are evidence of the possibility of eliminating VMV infection without resorting to whole-flock segregation or culling of seropositive sheep.