The equine infectious anemia (EIA) is a viral infection transmitted by the blood of equids that is happening all around the world. The causative agent is a lentivirus, and the majority of the horses that survive the acute phase of the infection become carriers for life.
The infection is spread primarily through the flies and the flies of deer, although the transmission can also occur with the reuse of needles, syringes and instruments or by the semen of an infected mare to his foals. There is No cure and the horses that test positive in the test of immunodiffusion in agar Coggins must be isolated until they confirm the results.
Symptoms of Equine Infectious Anaemia (EIA)
The first symptom of the equine infectious anemia is fever, which can last anywhere from 1 to 3 days. Horses undergoing this stage of the disease tend to exhibit a lack of appetite, a low platelet count (thrombocytopenia), anemia, and thrombus formation. The severity of these symptoms varies from one horse to another, depending on the virulence of the virus strain and the susceptibility of the individual animal.
As the infection progresses, the horses often develop splenomegaly (enlarged spleen), and hepatomegaly (enlarged liver). The jaundice of the mucous membranes and petechial hemorrhages are common, as the edema (swelling) of the skirt, the ventral abdomen and the extremities. The horses that are sick in this phase may show less response to exercise and have a low resistance. Some horses will develop a subacute form recurrent disease that appears similar to the acute phase, but is less severe and rarely results in death.
Some horses that recover from the acute phase of the disease remain asymptomatic for many years and have positive serological results. This is considered a carrier state unapparent and the horse will seem normal, although it is unable to transmit the disease to other animals. Some of the horses in this state of asymptomatic carrier will suffer relapses at an advanced age, especially during periods of stress. Those who fall may have symptoms such as weight loss, swelling of the legs and anemia.
Relapse may be associated with a plasma viremia or high counts, low platelet. Horses that fall they will die by intravascular coagulation of blood or thrombus formation.
Diagnosis
The equine infectious anemia (EIA) is a blood-borne virus that causes a life-threatening disease in horses. Once diagnosed, the horses with the virus are considered to be carriers for life. May experience recurrent episodes of the disease, which can vary from mild to severe. These episodes can cause fever, counts, low platelet count, loss of resistance and lack of performance in the horse. The infected horses are also predisposed to other bacterial infections due to their compromised immunity.
The incubation period of equine infectious anemia (EIA) is usually 14 days, but can last up to several months. The first attack is usually acute and usually ends with the death within a few days. Most of the times, the infection progresses to a chronic or subacute characterized by recurrent episodes of disease at intervals very variable. These episodes usually result in high fever, thrombocytopenia, and loss of strength. In some cases, horses will develop a progressive anemia which will result in death due to lack of red blood cells.
Some infected horses become carriers invisible and does not show signs of disease. Others show relapse minors of the recurrent disease accompanied by increase of the fever, thrombocytopenia, and weakness. Horses shapes with the subacute and chronic disease are not suitable for hard work, and must be sacrificed.
As is the case with the west nile virus (WNV) there is no treatment or cure for equine infectious anemia. After the confirmation of a positive test for the virus, the animal must be euthanized or placed in permanent isolation and quarantine at a distance of 200 yards from all other horses on the premises to avoid transmission.
The virus EIA is mainly transmitted through insect vectors contaminated with blood, including the flies mordedoras, the flies of the stables, and the flies of deer. It can also spread through the use of tools that are contaminated with blood, such as needles, syringes, or surgical instruments, and through the transfer of infected semen from a stallion to their foals.
The horses introduced to a new herd should be tested for equine infectious anemia (EIA) and isolated as tests are pending. It requires a proof of Coggins negative in some states, before a horse can move across state borders.
Prevention of Equine Infectious Anaemia (EIA)
The equine infectious anemia (EIA) is a serious disease with no treatment or vaccine known. The EIA has a wide geographical distribution and few countries can claim to be free of the disease for this reason, the international movement of horses is an important source of spread of the virus.
The equine infectious anemia is a RNA virus classified in the genus Lentivirus of the family Retroviridae. It is similar to the lentiviruses that cause AIDS in humans. The virus EVAV does not infect laboratory animals, common, or generates strong neutralizing antibodies in the infected horses. However, the virus quickly loses its infectivity outside the body.
The infection is achieved most commonly through the transfer of blood from an infected animal to another by insects that feed on blood, as biting flies (especially the flies and the flies of deer) and mosquitoes. The virus can spread more quickly during a good rainy season when the river systems are flooded and there's a lot of biting flies.
The amount of virus EIA in the blood of an infected animal, called viremia or viral load, can vary from one day to another. The high levels of the virus can result from stress due to exercise, transportation, or disease.
The isolation and quarantine of horses positive for equine infectious anemia is an effective way to prevent the spread of the virus and helps to control and prevent other diseases in horses. These horses must be permanently identified with a tattoo, brand, or microchip, and stay away from all other horses for at least 200 yards. Also they should make the test and they should be negative Coggins before they can sell or move out of the property. Horses infected with the virus EVAV that do not comply with these requirements must be sacrificed.
Treatment
The equine infectious anemia is a blood disease caused by the same virus that causes HIV in humans. It is a lentivirusof the same family that AIDS and feline immunodeficiency virus (FIV). This means that the virus affects the cells that produce red blood cells (erythropoiesis), which causes anemia and other signs of disease.
The virus also interferes with cell function by changing the gene expression, which leads to the production of pro-inflammatory mediators or cytokines such as TNF-alpha, IL-1 and IL-6. These cytokines cause an inflammatory response, which is one of the reasons why horses develop a fever and other clinical signs. Also inhibit erythropoiesis and cause thrombocytopenia or low platelet counts.
The infection leads to an acute illness of sudden in susceptible horses, followed by recurrent episodes of the disease with severity variable and intervals between episodes. Some horses remain asymptomatic and become carriers invisible, but continue to produce viral loads in plasma low and, therefore, can transmit the infection to other horses. A small amount of horsepower control the infection and show no signs of recurrent disease, but it can be infectious during periods of stress or while receiving immunosuppressive drugs.
For a recurrent episode, the signs of the disease include fever, loss of appetite and loss of weight, anemia, and bleeding spot on the mucous membranes. The virus is usually diagnosed through a proof of Coggins, which looks for antibodies to the virus that causes equine infectious anemia in the blood of the horse. The test is performed by extracting a sample from the jugular vein of the neck and sending it to a laboratory for analysis.
Horses that test positive in the proof of Coggins is considered to be infected and should be euthanized or placed in strict isolation. This is to prevent the transmission of the virus to other horses and to minimize the risk of a fatal reaction and sudden in those who are asymptomatic. Currently, the research focuses on eliminating the virus from asymptomatic carriers and to develop a vaccine to protect against this.
