What are Melioidosis?
Melioidosis is common in certain areas of Northern Australia and Southeast Asia such as Thailand. The beginning of melioidosis often includes abscesses with yellowish green pus or thick material in the area where the infection began. The most common areas of the infection are the liver, spleen, lungs, and lymph nodes closest to the infection. The pus filled Swiss cheese like appearance to the nodules or lesions is a common finding.
Melioidosis (Whitmore’s disease) is a serious and often fatal disease caused by the Burkholderia pseudomallei (Pseudomonas pseudomallei) bacteria, which can be found in water and soil. This illness can be acute or chronic and may affect any area, including the vital organs and skin. Acute melioidosis starts off with a high fever and cough and spreads from the lungs to other areas of the body such as the central nervous system, liver, gastrointestinal, and spleen, although some animals are symptom free when in the latent stage and the melioidosis is found on a routine examination. Melioidosis is considered chronic if the symptoms last more than two months, which happens in about 10% of patients. It has been misdiagnosed many times as tuberculosis because it mimics the disease so closely.
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Symptoms of Melioidosis in Horses
Because melioidosis can affect any of your horse’s symptoms or organs, the symptoms will vary greatly depending on the location of the infection.
- Increased body temperature
- Loss of appetite
- Swollen glands
- Painful muscles
- Water retention
- Skin lesions or abscesses
- Injury or laceration
- Skin nodule
- Ulcerated skin
- Respiratory symptoms (cough, nasal discharge)
- Gastric distress
- Muscle and joint pain
Central Nervous System
- Walking in circles
- Vision loss
- Involuntary eye movements
- Muscle spasms
- Nasal discharge
- Sore muscles
- Severe coughing
- Lung abscess
- Respiratory distress
- Acute melioidosis is a sudden onset of a fever, cough, and nasal discharge which migrates to other areas, causing more symptoms
- Chronic melioidosis happens when the symptoms of acute melioidosis last longer than two months
Causes of Melioidosis in Horses
- Gram negative bacterium called Burkholderia pseudomallei sometimes found in water or soil.
- Contaminated wound
- Ingesting contaminated soil
- Inhaling spores
Diagnosis of Melioidosis in Horses
Diagnosing melioidosis in horses includes isolating and identifying burkholderia pseudomallei and the best way to do that is to get a tissue sample from one of the lesions or nasal discharge. However, the veterinarian will need to do a complete physical examination first. This usually includes examining your horse’s skin from head to tail, palpating the abdomen and lungs, checking heart rate, blood pressure, body temperature, height, weight, body condition score, breath sounds, and reflexes. Also, the veterinarian may ask you to walk your horse in a circle and on a straightaway to see how well your horse’s muscles and joints perform in motion. Your horse’s behavior, conformation, attitude, and stature will be assessed during the motion test as well.
In addition, an endoscopy may be done to get a tissue sample if the infection is in the respiratory system. If lesions or abscesses are visible on the body, a sample will be obtained from several of those. Ashdown’s medium is the best material to use in isolating melioidosis in these samples, although other material can be used if necessary. The veterinarian will also get a urine and stool sample, throat swabs, and blood for isolating melioidosis with Ashdown’s medium. To rule out other conditions, other blood tests will be performed including glucose and insulin levels, fungal and bacterial cultures, packed cell volume (PCV), blood chemistry panel, blood urea nitrogen (BUN), and a complete blood count (CBC). In addition, chest x-rays should be performed as well as CT scans and an ultrasound of the abdomen and pelvic area.
Treatment of Melioidosis in Horses
Treatment for melioidosis varies in its intensity, but the main treatment is antibiotic medication. The decision of which antibiotic to use and how to administer the medication depends on the severity of the illness and your horse’s overall health.
Intravenous antibiotics with ceftazidime along with fluid therapy is used if your horse has very severe melioidosis. The mortality rate has gone from 74% to 37% with this treatment. However, it has some serious side effects that may include kidney damage.
Another antibiotic that has been used on horses with some success is amoxicillin-clavulanate. This has to be given intravenously as well, followed by 20 weeks of oral amoxicillin-clavulanate. The mortality rate with this medication was 40%, which is a decrease of about 50% with fewer side effects. The veterinarian will also treat the symptoms of the complications of melioidosis such as sepsis and pneumonia.
Recovery of Melioidosis in Horses
Your horse will likely be on strong antibiotics for several months so you will have to be vigilant in sticking to the instructions from the veterinarian. Be sure to use all of the medication even after your horse is doing better and call your veterinarian if you have any concerns or questions.