Equine viral arteritis (EVA) is a disease of horses caused by a virus of the species Equine arteritis virus (''Alphaarterivirus equid''), an

RNA virus An RNA virus is a virus characterized by a ribonucleic acid (RNA) based genome. The genome can be single-stranded RNA (ssRNA) or double-stranded (Double-stranded RNA, dsRNA). Notable human diseases caused by RNA viruses include influenza, SARS, ...

. It is the only species in the genus ''Alphaarterivirus'', and that is the only genus in the ''Equarterivirinae'' subfamily. The virus which causes EVA was first isolated in 1953, but the disease has afflicted equine animals worldwide for centuries. It has been more common in some breeds of horses in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, but there is no breed "immunity". In the UK, it is a

notifiable disease A notifiable disease is any disease that is required by law to be reported to government authorities. The collation of information allows the authorities to monitor the disease, and provides early warning of possible outbreaks. In the case of lives ...

. There is no known human hazard.

Signs

The signs shown depend on the horse's age, the strain of the infecting virus, the condition of the horse and the route by which it was infected. Most horses with EVA infection do not show any signs; if a horse does show signs, these can vary greatly in severity. Following infection, the first sign is

fever Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with Human body temperature, body temperature exceeding the normal range caused by an increase in the body's temperature Human body temperature#Fever, s ...

, peaking at , followed by various signs such as

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness, or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overw ...

, nasal discharge, "pink eye" (

conjunctivitis Conjunctivitis, also known as pink eye or Madras eye, is inflammation of the conjunctiva, the thin, clear layer that covers the white surface of the eye and the inner eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness ...

), swelling over the eye (supraorbital

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

urticaria Hives, also known as urticaria, is a kind of skin rash with red or flesh-colored, raised, itchy bumps. Hives may burn or sting. The patches of rash may appear on different body parts, with variable duration from minutes to days, and typically ...

, and swelling of the limbs and under the belly (the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

abdomen) which may extend to the udder in mares or the scrotum of male horses. More unusual signs include

spontaneous abortion Miscarriage, also known in medical terms as a spontaneous abortion, is an end to pregnancy resulting in the loss and expulsion of an embryo or fetus from the womb before it can survive independently. Miscarriage before 6 weeks of gestation is ...

in pregnant mares, and, most likely in foals, severe respiratory distress and death.

Cause

EVA is caused by an arterivirus called equine arteritis virus (EAV). Arteriviruses are small, enveloped, animal viruses with an

icosahedral In geometry, an icosahedron ( or ) is a polyhedron with 20 faces. The name comes . The plural can be either "icosahedra" () or "icosahedrons". There are infinitely many non- similar shapes of icosahedra, some of them being more symmetrical tha ...

core containing a positive-sense

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

genome. As well as equine arteritis virus the Arterivirus family includes

porcine reproductive and respiratory syndrome virus Porcine reproductive and respiratory syndrome virus (PRRSV), is a virus that causes a disease of pigs, called porcine reproductive and respiratory syndrome (PRRS), also known as blue-ear pig disease (in Chinese, ''zhū láněr bìng'' 豬藍耳� ...

(PRRSV),

lactate dehydrogenase elevating virus Lactate dehydrogenase elevating virus (LDV) constitutes the species ''Gamamaarterivirus lacdeh'' which is part of the family ''Arteriviridae'' and order ''Nidovirales''. The order ''Nidovirales'' also includes the family of coronaviruses. Arteriv ...

(LDV) of mice and simian haemorrhagic fever virus (SHFV). There are a number of routes of

transmission Transmission or transmit may refer to: Science and technology * Power transmission ** Electric power transmission ** Transmission (mechanical device), technology that allows controlled application of power *** Automatic transmission *** Manual tra ...

of the virus. The most frequent is the

respiratory The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies gr ...

route. Virions can also be shed into the semen, and the disease has been spread by artificial insemination. Stallions may become carriers.

Diagnosis

Because of the variability of symptoms, diagnosis is by laboratory testing. Blood samples, nasal swabs and semen can be used for isolation of the virus, detection of the viral RNA by

reverse transcriptase A reverse transcriptase (RT) is an enzyme used to convert RNA genome to DNA, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genomes, by retrotransposon mobi ...

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...

and detection of

antibodies An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...

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 is a solid-phase type of enzyme immunoassay (EIA) to detect the presence of ...

tests.

Prevention

vaccine A vaccine is a biological Dosage form, preparation that provides active acquired immunity to a particular infectious disease, infectious or cancer, malignant disease. The safety and effectiveness of vaccines has been widely studied and verifi ...

is available in the UK and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, however in laboratory tests it is not possible to distinguish between antibodies produced as a result of vaccination and those produced in response to infection with the virus. Management also plays an important part in the prevention of EVA.

Research

Zinc

ionophore In chemistry, an ionophore () is a chemical species that reversibly binds ions. Many ionophores are lipid-soluble entities that transport ions across the cell membrane. Ionophores catalyze ion transport across hydrophobic membranes, such as l ...

s show antiviral activity against Equine viral arteritis.

History

The virus causing EVA was first identified following an outbreak of respiratory disease and spontaneous abortion on a horse farm in

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

in 1953. The first outbreak of EVA in the UK was in 1993. The outbreak affected six premises and around 100 horses were infected. Further spread of the virus was prevented by movement restrictions.

References

External links

* {{Taxonbar, from=Q57758308, from2=Q18844364, from3=Q57753807, from4=Q57751690 Horse diseases Animal viral diseases