Florida Equine Diseases in 2023 to date
Florida Equine Diseases in 2023 to date
From January 1 to November 10, 2023
Here are the numbers of various equine infectious diseases in Florida during the first 10+ months of 2023:
Eastern Equine Encephalitis
Florida agriculture officials have reported 12 Eastern equine encephalitis (EEE) cases in horses in nine counties in 2023 to date-Polk, St. Johns, Jefferson counties reported two cases each, while the remaining six cases were reported in Jackson, Suwannee, Putnam, Lake, Baker and Levy counties.
Eastern Equine Encephalitis is a viral disease that causes inflammation of the brain and spinal cord. It is transmitted by mosquitoes.
Mosquitoes become infected when they feed on infected birds, which circulate high levels of the virus in their blood for a period of time. These mosquito species include some Aedes, Coquillettidia and Culex species.
Infected mosquitoes can then transmit the virus to humans and animals while biting to take a blood meal.
The disease is not directly transmitted between horses, from birds to horses, or from horses to humans.
Clinical signs and symptoms of EEE include the following:
Depression and anorexia; initially without a fever when initially infected
Moderate to high fever
Lack of appetite
Lethargy/drowsiness
Neurologic signs- onset of neurologic disease is frequently sudden and progressive
The only treatment available is supportive care with documented mortality rates between 70 and 95 percent.
Vaccination for EEE is highly effective and is recommended as a core vaccination.
Two human EEE cases have been reported in Florida this year—in St. John’s and Suwannee counties.
Equine herpesvirus (EHV)
The equine herpesvirus-1 (EHV-1) is one of a large group of viruses in the family Alphaherpesviridae that causes potentially serious disease in horses.
There has been two EHV-1 cases reported in horses this year in Florida—in Broward and Marion counties.
EHV-1 infection may occur subclinically or be manifest in three clinical forms that can occur independently or concurrently. These forms include reproductive, respiratory and neurologic disease—it can cause the neurologic form of the disease (equine herpesvirus myeloencephalopathy (EHM)) which creates damage to the spinal cord and can be fatal.
Transmission occurs when infected and uninfected horses come in either direct (nose to nose) or indirect (through contaminated buckets, clothing and blankets) contact with nasal discharges of infected horses.
Supportive care and rest are the chief treatments.
Vaccinations are available to help prevent the respiratory and abortive form of EHV-1 and EHV-4; there is currently no vaccine labeled for the prevention of the neurologic form of EHV-1 (EHM).
Equine infectious anemia
Equine infectious anemia (EIA) is a potentially fatal blood-borne infectious viral disease that produces a persistent infection among equids nearly worldwide.
According to state agriculture officials, one case was reported in Florida in Lee County this year.
Natural transmission occurs when a deer or horsefly bites and consumes a blood meal from an infected horse and transfers the virus via its mouthparts to another horse.
Clinical signs can vary widely. Most infected horses are asymptomatic, showing no signs of disease. Clinical signs, if present include:
Fever
Depression
Low platelet count
Anemia
Red or purple spots on the mucous membranes
Muscle weakness
Muscle atrophy
There is no known treatment for EIA. Infected horses become lifelong carriers and pose a risk of infection to other horses. Horses confirmed positive can be quarantined for the rest of their life but are usually euthanized.
There is no approved vaccine for EIA in the United States.
Dengue: More than 100 local cases reported in the Miami area this year
Strangles
The highly contagious upper respiratory disease of equids, known as Strangles, is caused by the gram-positive β-hemolytic bacterium Streptococcus equi ssp. equi.
In Florida this year to date, 32 strangles cases have been reported in Florida horses with Marion and Palm Beach counties reporting the most with seven cases each.
The organism Streptococcus equi ssp. equi can be transmitted via direct contact with nasal or ocular secretions or lymph node discharge from infected horses or via indirect exposure to contaminated trailers, stalls, riding equipment, buckets, halters, lead ropes, brushes, clothing, etc.
The incubation period for Strangles is 3 to 8 days, at which point the following clinical signs may appear:
Fever, usually preceding other clinical signs by 24-48 hours
Abscesses in the mandibular lymph nodes (in the throatlatch and below the jaw)
Nasal discharge: often thick white and yellow mucus
Inflammation of the throat • Difficulty swallowing
Wheezing
Coughing
Purpura hemorrhagica is a vasculitis which can be caused by Streptococcus equi. It results in bleeding which causes red spots on the mucous membranes and swelling of the limbs and head (rare; only in cases with complications)
Supportive care is the primary treatment. Use of antibiotics in infected horses is restricted to those with severe clinical signs such as respiratory difficulty as most horses recover without antibiotic treatment.
An intranasal vaccine is available but is not effective against all infections.
West Nile Virus
West Nile Virus (WNV) is a mosquito-borne virus that affects horses and results in fever and neurologic disease.
Two equine WNV cases were reported in Florida—in Palm Beach and Hernando counties.
Like EEE, WNV is transmitted via mosquitoes. Since 1999, more than 27,600 U.S. horses have been confirmed with WNV neuro-invasive disease with an estimated average case fatality rate of 30–40%.
he only vectors involved in the spread of WNV are mosquitoes.
Mosquitoes become infected when they feed on infected wild birds, which are the reservoir host.
The virus travels to, and replicates in, the mosquito’s salivary glands.
Infected mosquitoes can then transmit WNV to other birds, humans and mammals while taking a blood meal.
Clinical Signs for West Nile Virus include the following:
Depression and anorexia without fever when initially infected
Mild low-grade fever (101.5-103.5°F or 38.6-39.7°C) in about 25% of affected horses
Lack of appetite
Lethargy/drowsiness
Neurologic signs- Onset of neurologic disease is frequently sudden and progressive
Currently, there is no specific treatment for WNV.
Supportive care includes administration of anti-inflammatory drugs and intravenous fluids.
Vaccination and mosquito control minimize the risk of WNV infection in horses.
Rabies
Rabies is a fatal central nervous system disease that can affect all warm-blooded mammals, including humans. It occurs infrequently in horses.
One horse was diagnosed with rabies this year in Marion County, Florida.
Rabies is typically transmitted via contamination of a wound or mucous membrane with infectious saliva.
World Rabies Day Livestream Special
The most common route of infection in the horse is a bite wound from a wild carnivore or bat carrying the virus.
In unvaccinated horses, rabies is rapidly progressive after onset of clinical signs with death occurring 5-7 days following the onset of clinical signs.
Physical signs may include:
Fever
Loss of appetite
Blindness o Difficulty swallowing
Hypersensitivity of the skin- can sometimes present as self-mutilation
Muscle twitching o Lameness
Paresis and/or ataxia- loss of body control
Incontinence
Paralysis – beginning in the extremities
Sudden death
No specific treatment exists for rabies in horses. All horses should be vaccinated annually for rabies.