While Coggins testing is used to test for equine infectious anemia, EIA is not the only condition transmitted by bloodsucking insects. There are countless other insect-borne infections and illnesses that can affect equines, and if you work with these animals, you should familiarize yourself with the most common. Below is a summary of some of the best-known and widespread insect-related afflictions an equine animal may experience.
Tick-Borne Diseases – Three tick-borne diseases pose large threats to horses: Lyme disease, anaplasmosis, and piroplasmosis. Most people familiar with animals will know a bit about Lyme disease, which is transmitted by blacklegged ticks (Ixodes scapularis). It is notably difficult to prevent, diagnose, and treat because not all infected horses exhibit clinical signs. Testing should include Lyme Multiplex and Western blot diagnostics, but additional screening tests can include canine IDEXX SNAP, the enzyme-linked immunosorbent assay (ELISA), and indirect fluorescent antibody tests (IFAT). All of these can detect B. burgdorferi antibodies, which indicate exposure to Lyme disease. Conversely, piroplasmosis and anaplasmosis are caused by Babesia caballi and anaplasma phagocytophilum, respectively. The C-ELISA blood test is the gold standard for these diseases.
Mosquito-Borne Diseases – Most mosquito-borne diseases, such as Eastern, Western, Venezuelan, and St. Louis Equine Encephalitis, as well as West Nile Virus, will cause damage to the central nervous system. Another common mosquito-borne disease, Malaria, causes hemorrhagic fever. If you believe your horse to have contracted a mosquito-borne illness, it is important to observe symptoms very carefully, as they differ between diseases. All variations of Encephalitis will include a high fever, changes in behavior, muscle twitching, head pressing, the inability to swallow, and in the most severe cases, paralysis and convulsions. By contrast, Malaria, manifests as chills, fever, vomiting, abdominal pain, diarrhea, respiratory distress, renal/liver failure, and shock. A veterinarian will perform test specifically for whichever virus is suspected, like virus-specific IgM, neutralizing antibodies, and liver enzymes.
Potomac Horse Fever (PHF) – Equine neorickettsiosis, also known as Potomac Horse Fever, is seasonal, often occurring between late spring and early fall in temperate areas. It is caused by bacterial infection from Neorickettsia risticii, which is found in flatworms. They can develop in aquatic snails, damselflies, caddisflies, and mayflies. Horses may pick up the disease by grazing near freshwater creeks, rivers, or on irrigated pastures. PHF can lead to fever, loss of appetite, diarrhea, and, in the most severe cases, death, but clinical signs typically last between 1 and 15 days. If you suspect your horse has PHF, a veterinarian will perform a disease-specific blood test. Vaccinations is the best protection from PHF.
Insect Bite Hypersensitivity (IBH) – Insect Bite Hypersensitivity is known colloquially as a bug bite allergy. Susceptible horses are usually allergic to insect saliva, and the reactions can range from hibes and itchiness to hair loss and dermatitis. The most common allergies occur after sustaining bites from culicoides, which include gnats, midges, sand flies, black flies, stable flies, horse flies, and, sometimes, mosquitoes. A definitive diagnosis can only be made with intradermal allergy testing. The best forms of defense against IBH include allergy shots, Omega-3 fatty acid supplements, and avoidance in the form of insect repellent.
African Horse Sickness (AHS) – African Horse Sickness is an often-fatal disease caused by the genus Orbivirus belonging to the family reoviridae. The principal transmitters of this disease include gnats, midges, and other culicoides, and it occurs primarily in warm, rainy seasons. Clinical signs include lesions, but laboratory confirmation is essential for a definitive diagnosis. Keep in mind that AHS has never been reported in the Americas, eastern Asia, or Australia.