Equine Infectious Anemia (EIA)

Master Preventive Medicine – Notes, Case Studies and Practical Insights – with Lomash

Equine Infectious Anemia (EIA)

Syn: Swamp fever

It is a chronic persisting infectious, non-contagious viral disease of equids characterized by emaciation, anemia, intermittent fever and generalized lymphoproliferative changes and edema.
Of the equid species known to be susceptible to the virus, horses and ponies are more likely to develop severe clinical manifestations of the disease than are donkeys or mules, in which infection is most frequently subclinical

Etiology:

Lentivirus of family Retroviridae
RNA virus and has got resemblance with human AIDS virus
It can be killed by exposing them to heat and commonly available house detergents.

Epidemiology:

Geographically widespread throughout the world.
Disease is endemic in parts of North & South America, Africa, Europe, Asia; sporadic outbreaks elsewhere.
From April 1, 2005 to May 15, 2024, a total of 63 EIA outbreaks (363 cases) were reported to WOAH. Most of them are reported from European Union.
All equids infected with EIA virus remain lifelong carriers.
In a study conducted in 2021 in Brazil, seroprevalence of EIA was found to be 3.12%

Transmission:

Blood sucking insects are chief agents; Tabanus, Stomoxys and mosquitoes
It can also be transmitted through IV, SC, or IM inoculation of material
Transmission from blood, urine, nasal and eye discharge remains infective and transmits from equine to equine is possible.

Pathogenesis:

After entry of virus; it is present in blood and all tissue and discharge.
Localize in spleen, kidney, liver and lymph nodes and multiplies there
Viremia occurs. Virus then attacks erythrocytes and causes their destruction
It also damages endothelial lining of blood vessel
Peripheral nerves, meninges and brain tissues are affected and causes nervous manifestation.

Clinical Signs:

PM Findings:

Entire carcass of animals shows subcutaneous edema, submucosal and sub-serous haemorrhage
Generalized lymphadenopathy
Hepatomegaly, splenomegaly

Diagnosis:

On the basis of clinical signs
On the basis of PM findings
Blood examination: decreased RBC, decreased PCV, increased ESR, slight leukopenia, total serum protein is reduced
Immunodiffusion test: ELISA, RT-PCR

Differential Diagnosis:

Treatment and Control Measures:

There is no specific treatment for this disease. Symptomatic treatment is done.
Since the infected ones are life-long carriers, they are generally euthanized.
No safe and effective vaccine is available for equine infectious anemia.
Annual testing of all horses as part of EIA control plan.
All equines introduced to a herd should have a negative EIA test before arrival or be isolated while tests are pending.
Horses competing in shows or performance events should be accompanied by proof that they have been tested for EIA within a specific period of time.
Routine application of insecticides and repellants as well as the implementation of insect control measures.
Re-use of contaminated needles, syringes, surgical or dental instruments, or other equipment should be avoided.
Sterile needle, syringe, and IV set should be used for all injections or treatments.
Dental, tattoo, surgical equipment, lip chains, and bits should be disinfected thoroughly between horses. All debris and blood with soap and water should be cleaned before disinfection.
Open wounds should be kept clean and covered, if possible
A sterile needle and syringe should be used each time when puncturing a multidose medication bottle.
Sterile technique should be used when drawing up and administering medications.
Good fly control should be practiced by regular mucking out of stalls, proper disposal of manure away from horse stabling areas, and using fly sprays or natural predators to minimize fly presence.