Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


visna/maedi virus



visna/maedi virus


  • Last modified
  • 20 November 2019
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • visna/maedi virus
  • Taxonomic Tree
  • Domain: Virus
  •   Group: "DNA and RNA reverse transcribing viruses"
  •     Family: Retroviridae
  •       Genus: Lentivirus
  •         Species: visna/maedi virus
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Preferred Scientific Name

  • visna/maedi virus (ICTV)

Other Scientific Names

  • maedi virus
  • maedi-visna virus (Pepin et al., 1998)
  • visna virus
  • visna/maedi virus (strain 1514)
  • visna-maedi virus

International Common Names

  • English: ovine lentivirus; ovine progressive pneumonia virus

English acronym

  • MVV
  • VMV

Taxonomic Tree

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  • Domain: Virus
  •     Group: "DNA and RNA reverse transcribing viruses"
  •         Family: Retroviridae
  •             Genus: Lentivirus
  •                 Species: visna/maedi virus

Diseases Table

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Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 06 Jan 2022
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes


AlgeriaAbsent, No presence record(s)Jul-Dec-2019
AngolaAbsent, No presence record(s)Jul-Dec-2018
Burkina FasoAbsent, No presence record(s)Jul-Dec-2019
Cabo VerdeAbsent, No presence record(s)Jul-Dec-2019
CameroonAbsent, No presence record(s)
Central African RepublicAbsent, No presence record(s)Jul-Dec-2019
Congo, Democratic Republic of theAbsentJul-Dec-2019
Côte d'IvoireAbsent, No presence record(s)
EgyptAbsent, No presence record(s)Jul-Dec-2019
EswatiniAbsent, No presence record(s)Jul-Dec-2019
GuineaAbsent, No presence record(s)
KenyaAbsent, No presence record(s)Jul-Dec-2019
LesothoAbsent, No presence record(s)Jan-Jun-2020
MadagascarAbsent, No presence record(s)Jan-Jun-2019
MalawiAbsent, No presence record(s)Jul-Dec-2018
MaliAbsent, No presence record(s)Jul-Dec-2019
MauritiusAbsent, No presence record(s)Jul-Dec-2019
MayotteAbsent, No presence record(s)Jul-Dec-2019
MoroccoAbsent, No presence record(s)Jul-Dec-2019
NigeriaAbsent, No presence record(s)Jul-Dec-2019
Saint HelenaAbsent, No presence record(s)Jan-Jun-2019
SeychellesAbsent, No presence record(s)Jul-Dec-2018
Sierra LeoneAbsentJan-Jun-2018
South AfricaAbsentJul-Dec-2019
South SudanAbsentJan-Jun-2018
SudanAbsent, No presence record(s)Jul-Dec-2019
TanzaniaAbsent, No presence record(s)
TogoAbsent, No presence record(s)Jul-Dec-2019
UgandaAbsent, No presence record(s)
ZambiaAbsent, No presence record(s)Jul-Dec-2018
ZimbabweAbsent, No presence record(s)Jul-Dec-2019


AfghanistanAbsent, No presence record(s)Jul-Dec-2019
BahrainAbsent, No presence record(s)Jul-Dec-2020
BangladeshAbsent, No presence record(s)Jan-Jun-2020
BhutanAbsent, No presence record(s)Jan-Jun-2020
BruneiAbsent, No presence record(s)Jul-Dec-2019
GeorgiaAbsent, No presence record(s)Jul-Dec-2019
Hong KongAbsent, No presence record(s)Jul-Dec-2019
IndonesiaAbsent, No presence record(s)Jul-Dec-2019
IranAbsent, No presence record(s)Jan-Jun-2019
JordanAbsent, No presence record(s)
KazakhstanAbsent, No presence record(s)Jul-Dec-2019
LaosAbsent, No presence record(s)Jan-Jun-2019
MalaysiaAbsent, No presence record(s)Jan-Jun-2019
-Peninsular MalaysiaAbsent, No presence record(s)
-SabahAbsent, No presence record(s)
-SarawakAbsent, No presence record(s)
MaldivesAbsent, No presence record(s)Jan-Jun-2019
MongoliaPresent, LocalizedJan-Jun-2019
NepalAbsent, No presence record(s)Jul-Dec-2019
North KoreaAbsent, No presence record(s)
PakistanAbsent, No presence record(s)Jan-Jun-2020
PhilippinesAbsent, No presence record(s)Jul-Dec-2019
Saudi ArabiaAbsent, No presence record(s)Jan-Jun-2020
SingaporeAbsent, No presence record(s)Jul-Dec-2019
South KoreaAbsent, No presence record(s)Jul-Dec-2019
Sri LankaAbsent, No presence record(s)Jul-Dec-2018
TaiwanAbsent, No presence record(s)Jul-Dec-2019
ThailandAbsent, No presence record(s)Jan-Jun-2020
United Arab EmiratesAbsent, No presence record(s)Jul-Dec-2020
UzbekistanAbsent, No presence record(s)Jul-Dec-2019
VietnamAbsent, No presence record(s)Jul-Dec-2019


BelarusAbsent, No presence record(s)
Bosnia and HerzegovinaAbsentJul-Dec-2019
Faroe IslandsAbsent, No presence record(s)Jul-Dec-2018
Isle of ManAbsent, No presence record(s)
JerseyAbsent, No presence record(s)
LithuaniaAbsent, No presence record(s)Jul-Dec-2019
MaltaAbsent, No presence record(s)
MoldovaAbsent, No presence record(s)Jan-Jun-2020
North MacedoniaAbsentJul-Dec-2019
RussiaPresent, LocalizedJan-Jun-2020
San MarinoAbsent, No presence record(s)Jan-Jun-2019
UkraineAbsent, No presence record(s)Jul-Dec-2020
United KingdomPresentJul-Dec-2019
-Northern IrelandAbsent, No presence record(s)

North America

BahamasAbsent, No presence record(s)Jul-Dec-2018
BarbadosAbsent, No presence record(s)Jul-Dec-2020
BelizeAbsent, No presence record(s)Jul-Dec-2019
BermudaAbsent, No presence record(s)
British Virgin IslandsAbsent, No presence record(s)
Cayman IslandsAbsentJan-Jun-2019
Costa RicaAbsent, No presence record(s)Jul-Dec-2019
CubaAbsent, No presence record(s)Jan-Jun-2019
CuraçaoAbsent, No presence record(s)Jan-Jun-2019
DominicaAbsent, No presence record(s)
Dominican RepublicAbsent, No presence record(s)Jan-Jun-2019
El SalvadorAbsent, No presence record(s)Jul-Dec-2019
GreenlandAbsent, No presence record(s)Jul-Dec-2018
GuadeloupeAbsent, No presence record(s)
GuatemalaAbsent, No presence record(s)Jan-Jun-2019
HaitiAbsent, No presence record(s)Jul-Dec-2019
HondurasAbsent, No presence record(s)Jul-Dec-2018
JamaicaAbsent, No presence record(s)Jul-Dec-2018
NicaraguaAbsent, No presence record(s)Jul-Dec-2019
PanamaAbsent, No presence record(s)Jan-Jun-2019
Saint Kitts and NevisAbsent, No presence record(s)
Saint LuciaAbsent, No presence record(s)Jul-Dec-2018
Saint Vincent and the GrenadinesAbsent, No presence record(s)Jan-Jun-2019
Trinidad and TobagoAbsent, No presence record(s)Jan-Jun-2018
United StatesPresent, LocalizedJul-Dec-2019


AustraliaAbsent, No presence record(s)Jul-Dec-2019
Cook IslandsAbsentJan-Jun-2019
Federated States of MicronesiaAbsent, No presence record(s)Jan-Jun-2019
FijiAbsent, No presence record(s)Jan-Jun-2019
French PolynesiaAbsentJan-Jun-2019
KiribatiAbsent, No presence record(s)Jan-Jun-2018
Marshall IslandsAbsent, No presence record(s)Jan-Jun-2019
New CaledoniaAbsent, No presence record(s)Jul-Dec-2019
New ZealandAbsent, No presence record(s)Jul-Dec-2019
PalauAbsent, No presence record(s)Jul-Dec-2020
SamoaAbsent, No presence record(s)Jan-Jun-2019
Timor-LesteAbsent, No presence record(s)Jul-Dec-2018
VanuatuAbsent, No presence record(s)Jan-Jun-2019

South America

BoliviaAbsent, No presence record(s)Jan-Jun-2019
EcuadorAbsent, No presence record(s)Jul-Dec-2019
Falkland IslandsAbsent, No presence record(s)Jul-Dec-2019
French GuianaAbsentJul-Dec-2019
GuyanaAbsent, No presence record(s)
PeruPresent, LocalizedJan-Jun-2019
SurinameAbsent, No presence record(s)Jan-Jun-2019
UruguayAbsent, No presence record(s)Jul-Dec-2019
VenezuelaAbsent, No presence record(s)Jan-Jun-2019

Pathogen Characteristics

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Visna/maedi virus is the prototype Lentivirus belonging to subfamily Lentivirinae of the family Retroviridae, together with human immunodeficiency viruses (HIV-1 and HIV-2 viruses), caprine arthritis-encephalitis virus (CAEV), and the simian, bovine, feline immunodeficiency viruses (SIV, BIV and FIV respectively), and equine infectious anaemia virus (EIAV). Importantly, visna/maedi virus is a species-specific but not oncogenic virus. Depending on the cell type, visna/maedi virus infection may lead to a cytopathic effect, or remain unnoticed. This has important consequences for pathology and viral persistence.

Visna/maedi virus is a dimer of positive sense RNA of about 9.2 kb in size (Carey and Dalziel, 1993). Virus replication occurs by reverse transcription of the genome using the virus-encoded RNA-dependent DNA polymerase, and occurs via a DNA intermediate. Part of the proviral DNA is incorporated into the host genome. The genome of lentiviruses contains the structural genes (gag-group specific antigen and env-envelope), and enzymatic gene (pol-polymerase), typical for retroviruses. Analogous to other retroviruses, visna/maedi virus proviral DNA is flanked by long terminal repeats (LTR) that provide the cis signals required for transcription, integration and polyadenylation of viral RNA. LTR of visna/maedi virus may be involved in cell tropism (Agnarsdottir et al., 2000).

The gag-gene encodes for three proteins: the capsid or core protein (p25), the nucleocapsid (p14) and the matrix (MA) protein (p17), which ensures the link between the capsid and the envelope. The hydrophobic capsid protein is the most abundant constituent protein of visna\maedi virus. This capsid protein elicits a strong induction of antibodies upon infection, an effect that is used in diagnostic tests.

The env-gene encodes the glycoprotein of the virus. The precursor protein gp160 is cleaved into two subunits: the surface glycoprotein (SU: gp135), and the transmembrane glycoprotein (TM: gp44). The envelope glycoproteins of visna\maedi virus have important biological functions. They contain epitopes responsible for the induction of neutralising antibodies, and for interaction with cellular receptors during the replication cycle.

The pol-gene encodes the RNA-dependent DNA-polymerase, which is a heterodimer that permits transcription of the viral RNA into DNA.

Other visna/maedi virus-encoded enzymes are dUTPase, integrase and protease (Pepin et al., 1998).

Auxiliary genes that are not essential for virus replication further mediate the level of viral expression in lentiviruses. Visna/maedi virus also contains several short, multiply spliced ORFs that encode proteins which are thought to have regulatory function (Carey and Dalziel, 1993). Visna/maedi virus has three auxiliary genes: tat, vif-viral infectivity factor (previously called Q gene) and rev-regulator of virion protein expression.

The tat-gene encodes a 10 kDa protein, and mediates the accumulation of viral RNA. The vif-gene encodes a 29 kDa protein, and induces a weak immune response and is thought to play a role in the late stages of the viral life cycle, specifically during the morphogenesis of the viral nucleoprotein core. The rev-gene encodes a 19 kDa protein and plays a role in the early phase of visna\maedi virus replication, by transporting unspliced mRNA from the nucleus to the cytoplasm. The rev gene seems to be essential for visna/maedi virus replication as the rev-mutagenised virus appears uninfectious (Pepin et al., 1998).

Lentiviruses can be roughly separated into two groups based on their cell tropism. Visna/maedi virus, CAEV and EIAV replicate strictly in macrophages and monocytes, whereas the primate lentiviruses HIV and SIV also replicate in CD4+ lymphocytes (Narayan et al., 1997). Importantly, lentiviruses are capable to replicate in non-dividing terminally differentiated cells. This implies that cellular DNA replication is not required for integration of the viral DNA into the cellular genome. It is currently unknown whether the auxiliary genes of the lentiviruses, as opposed to the oncogenic retroviruses, play a role in altering the non-dividing cells to provide the necessary enzymes and metabolites for viral DNA replication and integration (Clements et al., 1994; Narayan et al., 1997).

The Lentivirusgag, pol en env genes encode proteins that comprise the infectious viral particle. Lentiviruses bud from the cell membrane in a fashion similar to the oncogenic retroviruses. However, in some cell types such as macrophages and endothelial cells, lentiviruses bud internally into intracellular vacuoles, thereby providing a reservoir of infectious virus particles that are not exposed to the cell surface and cannot be recognised by the immune system (Narayan et al., 1997).

After infection, the virus can establish itself into the genomic material of the host as proviral DNA, and reside in a quiescent proviral state for several months. At a given moment the virus is activated by cellular and viral factors and the disease starts to develop.

Genetically, lentiviruses are quite heterogeneous. This may contribute to persistence in the host by permitting immune evasion. The antigenic diversity also presents a huge obstacle in Lentivirus vaccine development. Antigenically distinct viruses have been isolated from sheep persistently infected with visna/maedi virus. These variants arose from mutations in the env-gene (Pepin et al., 1998).

Various strains of visna/maedi virus differ in their pathogenicity in vitro and in vivo. This may be accompanied by differences in phenotypic characteristics such as absence of cytopathic effect in alveolar macrophages.

Disease(s) associated with this pathogen is/are on the list of diseases notifiable to the World Organisation for Animal Health (OIE). The distribution section contains data from OIE's Handistatus database on disease occurrence. Please see the AHPC library for further information from OIE, including the International Animal Health Code and the Manual of Standards for Diagnostic Tests and Vaccines. Also see the website:

Host Animals

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Animal nameContextLife stageSystem
Capra hircus (goats)Domesticated host
Ovis aries (sheep)Domesticated host
Ovis aries musimon (European mouflon)Wild host


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Agnarsdottir G; Thorsteinsdottir H; Oskarsson T; Matthiasdottir S; St Haflidadottir B; Andresson OS; Andresdottir V, 2000. The long terminal repeat is a determinant of cell tropism of maedi- visna virus. J. Gen. Virol., 81(8):1901-1905.

Carey N; Dalziel RG, 1993. The biology of maedi-visna virus- an overview. British Veterinary Journal, 149(5):437-454; 100 ref.

Clements JE; Zink MC; Narayan O; Gabuzda DH, 1994. Lentivirus infection of macrophages. Immunol. Ser., 60:589-600.

Narayan O; Joag SV; Chebloune Y; Zink MC; Clements JE, 1997. Visna-Maedi: the prototype lentiviral disease. In: Nathanson N, Ahmed R, Gonzalez-Scarano F, Griffin DE, Holmes KV, Murphy FA, Robinson HL, eds. Viral Pathogenesis. Philadelphia, USA: Lippincott-Raven, 657-668. ISBN 0-7817-0297-6.

OIE Handistatus, 2002. World Animal Health Publication and Handistatus II (dataset for 2001). Paris, France: Office International des Epizooties.

OIE Handistatus, 2003. World Animal Health Publication and Handistatus II (dataset for 2002). Paris, France: Office International des Epizooties.

OIE Handistatus, 2004. World Animal Health Publication and Handistatus II (data set for 2003). Paris, France: Office International des Epizooties.

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (data set for 2004). Paris, France: Office International des Epizooties.

Pépin M; Vitu C; Russo P; Mornex JF; Peterhans E, 1998. Maedi-visna virus infection in sheep: a review. Veterinary Research, 29(3/4):341-367; many ref.

Distribution References

CABI Data Mining, 2001. CAB Abstracts Data Mining.,

OIE Handistatus, 2005. World Animal Health Publication and Handistatus II (dataset for 2004)., Paris, France: Office International des Epizooties.

OIE, 2018. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2018a. World Animal Health Information System (WAHIS): Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2019. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2019a. World Animal Health Information System (WAHIS): Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2020. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2020a. World Animal Health Information System (WAHIS). Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

Distribution Maps

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