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1 pagina.- Trabajo presentado al 24th Annual Meeting of the Spanish Society of Veterinary Pathology (Leon, Spain, Sep. 5-8, 2012)

Maedi-visna was accidentally introduced into Iceland by importation of a flock of Karakul sheep intended for breeding purposes in the year 1933. A brief description of maedi-visna in Iceland and its eradication is presented. Owing to the insidious onset of maedi the disease was first recognized in 1939 when it already had spread to many flocks in two different parts of the country. In individual flocks the annual mortality rate was often 15–30 per cent. The heavy losses and the wide spread of the disease are thought to be due to the traditional sheep farming practices in Iceland. An eradication program was started in 1944, slaughtering all sheep in affected areas, and replacing them with healthy young sheep from other parts of the country. The eradication was sucessfully accomplished in the year 1965.

A field trial to study the practicability and efficacy of maedi-visna control in sheep by artificial rearing of lambs was carried out during the lambing season of 1979. Lambs were immediately separated from the dams at birth, deprived of ovine colostrum, and reared isolated from the parent flock. Bovine colostrum was given instead of maternal colostrum. Eleven farms participated in the experiment. All flocks were severely infected with maedi-visna virus: 63-100% of the ewes were seropositive as demonstrated by ELISA. Artificially reared lambs were serologically tested and positives culled at the age of 6, 12, 18, 24, 30 and 36 months. Only very few positives were found: 1/389, 1/376, 0/337, 1/223, 1/192 and 0/144, respectively. The first two sero-positive lambs occurred in one flock, and it could be ascertained that both had mistakenly been given ovine colostrum probably containing maedi-visna virus. No explanation, other than sub-optimal hygiene and isolation, could be found for the two sero-positive sheep that turned up in another flock at 24 and 30 months of age although, transplacental infection cannot be entirely excluded. It is concluded that artificial rearing of ovine colostrum-deprived lambs is an effective and practicable method for the control of maedi-visna in sheep. The method appears particularly useful when valuable genetic material has to be salvaged.

Controlled animal experiments with the ovine maedi-visna virus, the prototype lentivirus, have been carried out for almost 40 years. This non-oncogenic virus leads to a life-long, persistent infection with slow development of lesions in the lungs and in the central nervous system. The virus is present in many cells in a DNA provirus state and its replication and expression is highly restricted in vivo. The basic biological features of maedi-visna virus are quite similar to those of HIV and this ovine lentiviral disease may be useful as a model for infection with human lentiviruses.

A serological survey for lentivirus infection was undertaken on a volunteer sample of 331 British goat herds. The prevalence of infected herds was 10.3 per cent and the prevalence of seropositive individual animals was 4.3 per cent. There was evidence of a geographical variation in the distribution of infection. Herds consuming pooled colostrum appeared to be at greater risk from infection. Approximately half the herds sampled had been established within the past six years. There was evidence of recently introduced infection in a relatively high proportion of infected herds.

Summary The results of the first four years of the Dutch national voluntary maedi‐visna control program, which was launched on January 1, 1982, are presented. At the end of the observation period, 1711 breeding flocks representing 70% of the registered breeding flocks participated. The program is based on accreditation of flocks that have passed two successive serological tests with an interval of six months between and post‐accreditation tests every 12 months. The flocks have to conform to a set of specific regulations. Sheep sold from such flocks receive a certificate stating that their origin was accredited. A total of 1212 flocks gained accredition. Of these flocks, 29.5% were free from infection from the beginning, 35.6% were created by total replacement of the original stock, 19.6% employed repeated testing and culling of positives, and 15.3% were created by artificial rearing of colostrum‐deprived lambs. A total of 22 flocks lost accreditation due to detection of 36 seropositives. These positives a...

Lambs born to ewes from flocks with a high incidence of maedi/visna were separated from their dams at birth (group 1), or after 10 h (group 2), six weeks (group 3) or one year (group 4) and were observed for periods of up to eight years. Group 1 lambs remained free of infection while 28 per cent, 76 per cent and 81 per cent respectively of lambs in the other groups developed clinical, serological or histopathological evidence of infection during the observation period. It is therefore concluded that vertical transmission, if it occurs at all, is of little significance in the epidemiology of the disease. The number of serologically, virologically and histopathologically maedi/visna positive sheep, the time of onset of disease and the severity of lesions were related to the duration of exposure to the parent flock. In a separate trial no evidence was obtained for the transmission of maedi/visna by Muellerius capillaris larvae.

In 1979 a field trial was started to study the feasibility of maedi-visna control in sheep by half-yearly serological testing (by ELISA) with culling of sero-positive ewes and their progeny. In 13 commercial flocks, with a mean initial incidence of serological reactors of 17%, the sero-positive ewes and all their progeny, those of preceding years included, were culled after each half-yearly test. The percentage of sero-positive sheep decreased gradually and at the end of the second year, at the 5th test, all flocks were sero-negative. Also the 6th and 7th test did not yield sero-positive sheep. At the 8th test, however, 3 sero-positive ewes were detected in one of the flocks. A definite conclusion as to the source of infection could not be drawn. The following flock test was negative. In 2 other commercial flocks, which had a mean initial incidence of sero-positive sheep of 53%, those sero-positive and only their suckling lambs were culled. Here too, a gradual decrease in the incidence of sero-positive sheep was observed at the 2nd and 3rd test, but at the 4th test a sharp increase occurred. The programme was continued and a decrease followed until 0% was reached at the 7th test (end of third year). Age analysis of the sero-positive sheep which caused this peak revealed that the majority had been born before the start of the trial. This suggests that a ‘second wave’ of sero-positive sheep may be prevented and a quicker result obtained if progeny of preceding years are culled as well. Apart from 1 flock (mentioned above), all flocks remained sero-negative after reaching 0% until the end of the observation period in December 1982. These results show that maedi-visna can be controlled by serological testing and culling of positive sheep. However, the present observation period of 4 years is still too short to conclude that complete eradication of the virus from the flocks has been achieved. Furthermore it appears that simultaneous culling of all progeny is preferable.

With the objective of detecting the presence of caprine lentivirus (CLV) in ewe milk and in ram semen, ten matrixes and four reproducers experimentally infected with CLV were used. Samples of ewe milk were collected during the four months of lactation, five collections per animal, totaling 50 samples. Regarding the rams, eight semen collections were made per animal, during one year of experimentation, totaling 32 samples. The milk and semen samples were submitted to DNA extraction and the nested polymerase chain reaction test (nPCR) to detect CLV proviral DNA. Eight (16%) of the milk samples were positive in nPCR originating from two ewes. Only one (3.12%) semen sample was positive. The amplification products were sequenced, and were confirmed to be a CLV genomic sequence. Thus, the presence of CLV proviral DNA in sheep milk and semen was demonstrated, confirming the feasibility of infection between species, and alerting to the risk of spreading infections. [Lentivírus caprino em leite e sêmen de ovinos]. Resumo: Com o objetivo de detectar a presença do lentivírus caprino (LVC) no leite de ovelhas e no sêmen de carneiros, utilizaram-se 10 matrizes e quatro reprodutores infectados experimentalmente com o LVC. Foram coletadas amostras de leite das ovelhas durante os quatro meses de lactação, ocorrendo cinco coletas por animal, totalizando 50 amostras. Quanto aos carneiros, realizaram-se oito coletas de sêmen por animal, durante um ano de experimentação, totalizando 32 amostras. As amostras de leite e de sêmen foram submetidas à extração de DNA e à prova de reação em cadeia da polimerase do tipo nested (nPCR) visando à detecção de DNA proviral do LVC. Oito (16%) amostras de leite foram positivas na nPCR oriundas de duas ovelhas. Apenas uma (3,12%) amostra de sêmen apresentou positividade. Produtos da amplificação foram sequenciados, confirmando-se tratar de sequência genômica do LVC. Dessa forma, demonstrou-se a presença do DNA proviral do LVC em leite e sêmen de ovinos, confirmando a viabilidade da infecção entre espécies e, assim, alertando sobre o risco de que a infecção seja disseminada. Made available in DSpace on 2017-09-24T00:12:27Z (GMT). No. of bitstreams: 1 CNPC2017Caprine.pdf: 376528 bytes, checksum: 3ae3a9af4fdd105cae76695fa5801913 (MD5) Previous issue date: 2017-09-22 [ALICE ANDRIOLI PINHEIRO].

RESUMO: Os lentiviros de pequenos ruminantes (LVPR) são responsáveis por enfermidades infecciosas e multissistêmicas causadas pelo Vírus da Artrite Encefalite Caprina (CAEV) e o Vírus da Maedi-Visna (MVV), e se apresentam sob as formas clínicas: articular, mamária, respiratória e nervosa. Desta forma esse trabalho objetivou determinar a ocorrência e avaliar os fatores de risco associados à infecção por LVPR no Estado de Sergipe, Brasil. Foram coletadas amostras sanguíneas de 1200 ovinos e 675 caprinos oriundos respectivamente de 60 e 41 propriedades localizadas em 25 municípios sergipanos no período de 2011 a 2014. Os diagnósticos dos LVPR foram determinados pela técnica sorológica de Imunodifusão em Gel Ágar (IDGA) usando o kit comercial da marca Biovetech®. Os dados das variáveis associadas aos fatores de risco foram obtidos a partir de questionários aplicados aos proprietários dos rebanhos e analisados estatisticamente. As frequências absolutas e relativas foram determinadas por análise estatística descritiva e os fatores de risco por análise univariada das variáveis de interesse pelo Teste de Qui-quadrado de Pearson e Exato de Fisher, quando necessário, e em seguida submetidos à análise de regressão logística. Foi evidenciada uma soropositividade de 5,03% (34/675) em caprinos e 1,50% em ovinos com 26,82% (11/41) e 28,33% (17/60) das propriedades apresentando ao menos um animal positivo respectivamente. Na análise dos fatores de risco, não foram observadas diferenças significantes para os ovinos, enquanto que, para os caprinos, rebanhos acima de 100 animais, que pastejam em áreas comuns com outros rebanhos, em uma distância ≤500 metros entre as propriedades, que adotam medidas biotecnológicas da reprodução e não utilizam agulhas estéreis, são mais susceptíveis à infecção por LVPR. Sendo assim, conclui-se que, há a presença dos LVPR em rebanhos sergipanos, e mesmo que em baixas frequências faz-se necessário a implementação de medidas profiláticas devido a possibilidade de expansão e desenvolvimento da caprinocultura do estado, e o alto padrão genético da raça Santa Inês. ABSTRACT: The lentiviruses of small ruminants are infectious and multisystemic diseases caused by the Caprine Arthritis Encephalitis Virus (CAEV) and the Maedi-Visna Virus (MVV), and present the clinical forms: articular, mammary, respiratory and nervous. This work aimed to determine the occurrence and to evaluate the risk factors associated with lentivirus infection of small ruminants in the State of Sergipe, Brazil. Blood samples were collected from 1200 sheep and 675 goats from 60 and 41 farms respectively, located in 25 Sergipe municipalities from 2011 to 2014. The diagnosis of small ruminant lentiviruses (LVPR) was determined by the serological technique of Immunodiffusion in Gel Agar (IDGA) using the commercial kit of the brand Biovetech®. Data from the variables associated with risk factors were obtained from questionnaires applied to the owners of the herds and analyzed statistically. Absolute and relative frequencies were determined by descriptive statistical analysis and risk factors by univariate analysis of the variables of interest by Pearson’s Chi-square test and Fisher’s exact test, when necessary. A logistic regression analysis was used, considering as a dependent variable for LVPR infection the reactive or non-reactive result observed in the IDGA. A seropositivity of 5.03% (34/675) was observed in goats and 1.50% in sheep with 26.82% (11/41) and 28.33% (17/60) of the properties had at least one animal positive respectively. The analysis of the risk factors, no significant differences were observed for sheep, while for goats, herds above 100 animals grazing in common areas with other herds, at a distance ≤ 500 meters between the properties, that adopt Biotechnological measures of reproduction and do not use sterile needles, are more susceptible to LVPR infection. Therefore, it´s concluded there is presence of lentiviruses of small ruminants in sergipan herds, and even if at low frequencies it is necessary to implement prophylactic measures due to the possibility of expansion and development of goat breeding of the state and the high genetic standard of the Santa Inês breed.

A brief history of the occurrence of maedi/visna or maedi/visna related diseases is given. The clinical features and diagnosis are described. Recent experimental work performed in an attempt to resolve the pathogenetic features of slowness and persistence of infection, characteristic of maedi/visna, is covered. A description of the epidemiology is given followed by possible methods of control.

1. Introduction.- 2. Maedi-Visna. History and Clinical Description.- 3. Maedi-Visna. Pathology and Pathogenesis.- 4. Maedi-Visna. Etiology and Immune Response.- 5. Diagnostic Methods.- 6. Economie Importance, Epidemiology and Control.- 7. Pathology and Epidemiology of Lentiviral Infection of Goats.- 8. Variations in Clinical Disease During Replication of Lentiviruses.- 9. Sheep Pulmonary Adenomatosis: Clinical, Pathological and Epidemiological Aspects.- 10. Sheep Pulmonary Adenomatosis: Studies on Its Aetiology.

Summary Over a period of five years, the epidemiology of maedi-visna virus (MVV) infection was studied by means of sequential serological examinations in a small flock of Texel sheep after the introduction of two infected ewes. The flock was managed as an average field flock except that seropositive sheep were kept in the flock as long as possible and that replacements were preferentially selected from progeny of seropositive ewes. The first seroconversion was observed after 11 months and was soon followed by three others. A year later, a considerable increase in the number of seropositives was observed and at the end of the experiment 20 of a total of 24 sheep (83.3%) had seroconverted. A total of 16 sheep were present in the flock during the whole study, of which 13 (81.3%) had become infected by horizontal transmission. Two sheep showed a clear but transient, and another sheep showed a weak and irregular seroresponse, whereas MV-lesions proved to be present. When the flock was slaughtered, the mean age of the sheep was 5.25 years. Only a few sheep showed poor bodily condition; no other conspicuous clinical signs were observed. Nevertheless, a total of 70% of the infected sheep had maedi-visna lesions in udder and/or lungs. Udder lesions were found in 78.6%, lung lesions in 42.9% and lesions in both organs were found in 21.4% of the affected sheep. The seronegative sheep were free of lesions. No arthritic lesions were found. A total of 22 fetuses from 13 seropositive ewes were virologically examined and none yielded MVV. Zusammenfassung Funfjahrige serologische Studie uber die naturliche Verbreitung von Maedi-Visna-Virus in einer Schafherde, vervollstandigt durch post mortem-Untersuchung Die Epidemiologie der Maedi-Visna-Virus-Infektion (MVV) wurde uber einen Zeitraum von funf Jahren durch sequentielle serologische Untersuchungen an einer kleinen Texel-Schafherde verfolgt, in welche zwei infizierte Mutterschafe eingebracht worden waren. Die Herde wurde als Durchschnitts-Feldherde gefuhrt, mit Ausnahme der Tatsache, das seropositive Schafe moglichst lange in der Herde belassen wurden, und das Ersatz bevorzugt aus der Nachzucht seropositiver Muttertiere gestellt wurde. Die erste Serokonversion wurde nach elf Monaten beobachtet und war bald von drei weiteren gefolgt. Ein Jahr spater lies sich ein beachtlicher Anstieg der seropositiven Tiere erkennen, und am Ende des Experiments waren bei 20 von insgesamt 24 Schafen (83,3%) Antikorpertiter feststellbar. 16 Schafe waren wahrend der gesamten Studie in der Herde, von diesen wurden 13 (81,3%) durch horizontale Verbreitung infiziert. Zwei Schafe zeigten eine deutliche, aber nur vorubergehende Serumantwort. Die eines anderen Tieres war schwach und unregelmasig, auserdem traten Maedivirus-Lasionen auf. Nach der Schlachtung der Herde lag das Durchschnittsalter der Tiere bei 5,25 Jahren. Nur wenige Schafe zeigten schlechte korperliche Verfassung; andere auffallige klinische Symptome wurden nicht beobachtet. Dennoch hatten 70% der infizierten Tiere Maedi-Visna-Lasionen im Euter und/oder Lungen. Bei den betroffenen Tieren wurden Euterlasionen in 78,6%, Lungenlasionen in 42,9% und Lasionen beider Organe in 21,4% der Falle gefunden. Seronegative Schafe waren frei von Lasionen. Arthritische Veranderungen wurden nicht beobachtet. Von insgesamt 22 virologisch untersuchten Feten, von 13 seropositiven Mutterschafen, enthielt keiner MVV.

Comunicacion presentada en el 30th Meeting of the European Society of Veterinary Pathology celebrado en Leon del 5 al 8 de septiembre de 2012.

Between 1997 and March 2004, the nervous form, or visna, of maedi-visna infection was diagnosed in 71 of 1631 sheep (4.35 per cent) examined in the Castilla y Leon region of Spain, of which 634 had shown nervous signs. The presence of the virus was confirmed by immunohistochemistry and in some cases by pcr on frozen-thawed or paraffin-embedded tissue samples. The main clinical signs were hindleg ataxia and paresis, but blindness or nystagmus were also observed. Thirty-three of the affected sheep (46.5 per cent) were two years old or younger. The affected sheep showed variable degrees of a non-suppurative meningoencephalitis, and immunohistochemistry identified positive cells in all cases, with no relation to the intensity of the inflammatory lesion.

Summary A small scale serological survey for antibodies to maedi‐visna virus among 15 flocks of sheep in Morocco revealed the infection in one flock. Infection appeared to be related with imported sheep. In addition, two abattoir surveys yielded, 0.1% lungs with gross and histological lesions suggestive of maedi.