Maedi-Visna. History and Clinical Description

Pálsson, Páll A.

doi:10.1007/978-1-4613-1613-8_2

Cited by 11 publications

(17 citation statements)

References 10 publications

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“…This result hasalsobeen describedinclinical Maedicases (14). The clinical andmorphologicalfindingsare similartoobservationsofotherauthors (2,4,21). It is worthmentioning thatone of the most important differential diagnosis for VisnaisScrapie, especially when the sheep show scratching (11).…”

Section: Discussionsupporting

confidence: 70%

“…Clinical cases of Maedi are distributedall over the world (21); however, there arereports from severalcountries about the serological prevalenceofantibodies againstMVV in sheep without manifest clinical signs (3,7,16). Alot of experimentalwork hasbeen done on the pulmonary as well as on the neurological formofthe disease (4,8,13,15,20,30,31).…”

Section: Introductionmentioning

confidence: 99%

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Clinic and CNS pathology of natural Visna cases

Ganter¹,

Henze²,

Wohlsein³

2007

Tierarztl Prax Ausg G

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Summary Objective: This study summarizes the clinical, serological, pathomorphological and laboratory findings in 19 sheep with spontaneous Visna in Germany. The cases occurred over a period of 13 years in 13 flocks. In all affected sheep cytologic examination of cerebrospinal fluid (CSF) was performed. In addition in six flocks from which 12 of the Visna cases came the whole flock was tested for Maedi/Visna virus (MVV) antibodies. Material and methods: The diagnosis of spontaneous Visna with typical clinical signs was proven by serological and histopathological investigations. Serological screening for MVV antibodies was performed with the agargel-immuno- precipitation-test (AGIDT). Additionally, cerebrospinal fluid (CSF) was obtained by lumbosacral puncture and examined cytologically. Results: Nine of the 19 cases were Texels and six East Frisian Milk sheep. Six out of nine Texels came from the same flock with a MVV-antibody intra-flock prevalence of 0.94. The mean age of the sheep was 3.9 ± 2.3 years (0.5–10 years). Time between onset of clinical symptoms until euthanasia due to recumbency was 35 ± 23 days (6–102 days). In most cases clinical signs started with ataxia, staggering and circling, followed by increasing paresis of the hind legs. In the late stages of the disease 14 sheep suffered from tetraparesis. Trembling of lips or eye lids, blindness and scratching were rare signs. In all cases pleocytosis (11–876 M/l, mean = 167 M/l) with mononuclear cells, predominantly macrophages, was found. This finding provides an additional diagnostic aid to support the clinical differentiation from other infectious diseases with neurological manifestation in sheep. Histopathology of the CNS revealed in most cases a severe leukoencephalitis and demyelinisation with perivascular lymphocytic infiltration. Conclusion and clinical relevance: Visna is an important differential diagnosis in CNS disorders of sheep. It also occurs in animals younger than one year. Visna occurs especially in highly infected flocks of susceptible sheep breeds. CSF cytology can help to differentiate Visna from other CNS diseases. Clinically, Visna may be an important differential diagnosis to Scrapie.

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Section: Discussionsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Clinic and CNS pathology of natural Visna cases

Ganter¹,

Henze²,

Wohlsein³

2007

Tierarztl Prax Ausg G

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“…Historically, the nervous form of the disease appears to have been uncommon (Pálsson 1990). Visna has been diagnosed sporadically (Watt and others 1990, 1992, Pritchard and others 1995, Constable and others 1996, Braun and others 2001 in association with the respiratory form (maedi), with the latter usually being the dominant clinical presentation (Wandera 1970, Watt and others 1990, 1992, Pritchard and others 1995.…”

Section: Discussionmentioning

confidence: 99%

Diagnosis of the nervous form of maedi‐visna infection with a high frequency in sheep in Castilla y León, Spain

Benavides

Gómez

Gelmetti³

et al. 2006

Veterinary Record

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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 León 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.

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“…Maedi-visna virus (MVV), a lentivirus closely related to the human immunodeficiency virus (HIV), causes a chronic wasting disease in sheep, characterized by pneumonia, mastitis, encephalitis and/or arthritis [7,32]. Classically, the most important syndrome of the infection is interstitial pneumonia [7,41] which is only seen in adult animals and shares common features with the respiratory affection observed in children 134 R. Bolea et al infected by HIV [39].…”

Section: Introductionmentioning

confidence: 99%

Maedi-visna virus infection of ovine mammary epithelial cells

et al. 2006

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-The aim of this work was to perform a complete study of maedi-visna virus (MVV) infected mammary glands of naturally-infected sheep, and to determine if cells other than macrophages undergo a productive viral infection in this organ. Fifteen seropositive and two seronegative ewes were selected from MVV-infected flocks on the basis of clinical indurative mastitis and three sheep from an MVV-free flock. Within the mammary gland, MVV-positive cells were located by immunohistochemistry in the stroma and the epithelial alveolar barrier, most likely the ovine mammary epithelial cells (OMEC) of the acini. In situ hybridization confirmed these findings. Ultrastructural studies showed the presence of lentivirus-like particles budding off the cell surface in the alveolar barrier and also free in the acinar lumen. The presence of mammary histopathological lesions and MVV together with clear indications of productive infection (demonstration of a cytopathic effect in OMEC cultures and infection of co-cultures) were observed in the 15 seropositive and one of the seronegative sheep from the infected flock. These findings demonstrate that the OMEC were infected in vivo and probably underwent productive infection when studied ex-vivo. The OMEC of MVV-free sheep, which had subsequently been infected in vitro with MVV, also showed productive infection when challenged in vitro, confirming the replication of MVV in OMEC in vitro. The presence of MVV-infected OMEC in the mammary gland from infected animals, the productive infection in these OMEC and the release of lentiviral particles to the acinar lumen may have relevance in the pathogenesis and transmission of MVV infection. maedi-visna / mammary gland / epithelial cells / indurative mastitis / ovine

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Maedi-Visna. History and Clinical Description

Cited by 11 publications

References 10 publications

Clinic and CNS pathology of natural Visna cases

Clinic and CNS pathology of natural Visna cases

Diagnosis of the nervous form of maedi‐visna infection with a high frequency in sheep in Castilla y León, Spain

Maedi-visna virus infection of ovine mammary epithelial cells

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