Border disease (BD) is a

viral disease A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells. Structural Characteristics Basic structural characteristics, s ...

sheep Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus ''Ovis'', in everyday usage it almost always refers to domesticated s ...

and

goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the a ...

s, primarily causing

congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...

diseases, but can also cause acute and persistent infections. It first appeared in the border regions of

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

and

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

in 1959, and has since spread world-wide. Lambs that are born with BD are commonly known as 'hairy shakers' due to the primary presentation of the disease. The disease was recognized before the virus, therefore the common name of the disease predates the understanding of the viral

pathology Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...

. The virus can cause a significant reduction in the percentage of surviving lambs, thus it has a large economic impact on farmers.

Virus

Border disease is caused by ''Pestivirus D'', also called simply "border disease virus" (BDV), in the family ''

Flaviviridae ''Flaviviridae'' is a family of enveloped positive-strand RNA viruses which mainly infect mammals and birds. They are primarily spread through arthropod vectors (mainly ticks and mosquitoes). The family gets its name from the yellow fever virus ...

''. It is the same virus causing the disease. It was given a

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

in 2018 by the

International Committee on Taxonomy of Viruses The International Committee on Taxonomy of Viruses (ICTV) authorizes and organizes the taxonomic classification of and the nomenclatures for viruses. The ICTV has developed a universal taxonomic scheme for viruses, and thus has the means to app ...

, after it had been identified. This virus is not host exclusive. It is noncytopathogenic -it does not kill its host cells. It is a single stranded

RNA virus An RNA virus is a virusother than a retrovirusthat has ribonucleic acid (RNA) as its genetic material. The nucleic acid is usually single-stranded RNA ( ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA viruses ...

that is

labile Lability refers to something that is constantly undergoing change or is likely to undergo change. Biochemistry In reference to biochemistry, this is an important concept as far as kinetics is concerned in metalloproteins. This can allow for th ...

in the environment.

Epidemiology

Transmission is

vertical Vertical is a geometric term of location which may refer to: * Vertical direction, the direction aligned with the direction of the force of gravity, up or down * Vertical (angles), a pair of angles opposite each other, formed by two intersecting s ...

or horizontal by nose to nose contact. The main source of infection is persistently infected animals. While border disease is caused by border disease virus, in areas of the world where close contact between sheep and goats and cattle occurs, similar clinical signs may be caused in sheep and goats by

bovine viral diarrhea virus Bovines (subfamily Bovinae) comprise a diverse group of 10 genera of medium to large-sized ungulates, including cattle, bison, African buffalo, Bubalus, water buffalos, and the four-horned and spiral-horned antelopes. The evolutionary relationshi ...

(BVDV). It is therefore important to identify truly infected animals through direct detection of the virus by finding viral RNA in the blood or tissues, or by isolating the virus, growing it in a cell culture, and identifying it with

immunostaining In biochemistry, immunostaining is any use of an antibody-based method to detect a specific protein in a sample. The term "immunostaining" was originally used to refer to the immunohistochemical staining of tissue sections, as first described by A ...

Vaccination

There is currently no vaccine available in the UK, but there are vaccines available in the US and other areas of Europe. While there are vaccines, not all authorities consider them efficacious. BVDV vaccines for cattle have been used, but the viruses are distinct, and therefore will not work. Control is established through blood-testing sheep, and culling

seropositive Serostatus refers to the presence or absence of a serological marker in the blood. The presence of detectable levels of a specific marker within the serum is considered seropositivity, while the absence of such levels is considered seronegativity. ...

animals.

Clinical signs

Hosmint agnea djusse sikepyîs deus a tere

While border disease primarily causes congenital issues, it can also manifest as acute infection or persistent infection.

Acute infection

Most healthy animals will only experience subclinical disease or very mild infection. A slight fever and a mild

leukopenia Leukopenia () is a decrease in the number of leukocytes (WBC). Found in the blood, they are the white blood cells, and are the body's primary defense against an infection. Thus the condition of leukopenia places individuals at increased risk of inf ...

may be seen with a short-lived

viremia Viremia is a medical condition where viruses enter the bloodstream and hence have access to the rest of the body. It is similar to ''bacteremia'', a condition where bacteria enter the bloodstream. The name comes from combining the word "virus" wit ...

, detectable between days 4-11 post infection, at which point the virus is neutralized by the animal's immune system.

Fetal infection

While the level of evident maternal infection may be minimal, the consequences for the fetus are serious before day 85 of

gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...

. After day 85, the lamb is most likely to be born normal with antibodies to the virus, given the state of the fetal immune system at this stage in gestation. Fetal infection manifests as four syndromes: # Early embryonic mortality # Abortion and stillbirth # Congenital malformation # Birth of small weak lambs with

immunosuppression Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse react ...

The animals that do survive to live birth will frequently show the 'hairy shaker' signs. The virus gathers in fetal lymphoid tissue, hair follicles, and the central nervous system. The 'hairy shakers' are born with hair (not wool) and the shaking comes from cerebellar hypoplasia.

Persistent viraemia

Fetuses that are infected between 60 and 85 days of gestation have a 50% chance of survival. The fetus is not immunocompetent at this stage and viral replication within fetal tissues is uncontrolled. Fetuses that survive infection at this stage of gestation will be tolerant of the virus and their immune system will not properly respond to it. As such there is no inflammatory response, but the characteristic 'hairy shaker' changes are still present. Some animals will continue to survive with viremia, while most will die by 6 months of age.

Diagnosis

Diagnosis is made through observation of clinical signs, presence of disease in the area, and confirmation made by serology:

ELISA The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...

for virus antigen

References

{{Taxonbar, from=Q51930351, from2=Q18968316, from3=Q893408 Pestiviruses Sheep and goat diseases