Equine Infectious Anemia
Caused by a virus, the disease may be either acute or rapidly fatal or, more commonly, chronic and characterized by intermittent attacks of fever (each lasting several days), loss of weight, progressive weakness, marked depression, and dropsical swellings. During and immediately after the fever there is a reduction in the number of red corpuscles in the blood, and postmortem examination frequently shows internal hemorrhages and damage to the spleen, liver, kidneys, and heart. In most areas the disease is confined to low-lying, swampy, or wooded sections, but in the Mississippi Delta it is widespread, principally in the chronic form, sapping the strength of large numbers of mules and making them incapable of work when they are most needed.
How infectious anemia spreads is not definitely known, in spite of considerable experimenting. Biting insects may play an important part; so may feed and water contaminated by the virus-laden excretions of infected .animals; so may long-continued, intimate contact of infected with normal animals. It is definitely known that after recovering from an attack, animals can carry the disease in latent form for many years, serving as unrecognized sources of infection for other animals.
Diagnosis is difficult, since the symptoms can easily be confused with those of various other diseases and of parasitic infestations. The only positive means of diagnosis is to inoculate a well horse with material from the suspected case. Nor is there any medicinal treatment that will bring about a cure or any method of preventing the disease by vaccination. Control depends primarily on the identification of carriers:
- Destroy any animal proved to have infectious anemia and dispose of the carcass by deep burial or cremation. (This is not practicable, of course, in regions like the Mississippi Delta, where the disease is widespread in a chronic form).
- Where infected animals are to be kept and worked, separate them from healthy animals and carry out all practicable steps to prevent transmission of the disease to the latter.
- Do not breed infected mares, since they can transmit the disease to their offspring.
- Plow and fence off badly contaminated pastures or other areas and exclude horses and mules from them for at least 6months.
- Provide good sanitation, control intestinal parasites and flies, supply pure, fresh drinking water, and never permit animals to drink from stagnant pools.