What are Aspergillosis?
Because there are different types of aspergillus spores, there are also different kinds of aspergillosis. Invasive aspergillosis usually affects very old, very young, or sick animals with compromised immune systems. This type is most often found in the lungs and spreads throughout the body, including the skin, blood, eyes, kidneys, heart, bones, sinuses, and nervous system. Non-invasive allergic bronchopulmonary aspergillosis (ABPA) is a less serious form of aspergillosis that usually only affects horses with lung diseases such as bronchiectasis cystic fibrosis and asthma. Chronic pulmonary aspergillosis (CPA) is a disease that lasts a long period of time, usually throughout your horse’s lifetime, coming and going at will and sometimes includes aspergilloma. An aspergilloma is a group of fungi that is found in one lung cavity, but is not always present in CPA. The final type of aspergillosis, severe asthma with fungal sensitisation (SAFS), only occurs in horses with asthma and include both sexes.
Aspergillosis in horses is caused by a commonly found group of fungi (molds) from the aspergillus species. These fungi spores are invisible to the naked eye and are found naturally in the air (indoors and out) all over the world and are capable of infecting any species from birds to humans. If the guttural pouch becomes infected, it can be fatal due to the damage of nerves and carotid arteries in the area. The guttural pouch is an air-filled pocket behind the skull and is subject to fungal and bacterial infections. The destruction can weaken the walls of the arteries which can cause extreme bleeding. The fungus causes destructive inflammation in the airway and nasal passages, producing blood from usually just one nostril. Even though it most often is found in the guttural pouch, horses may also contract pulmonary aspergillosis.
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Symptoms of Aspergillosis in Horses
- Bleeding from the nose (almost always just one nostril)
- Nasal discharge
- Extreme fatigue and weakness
- Drooping eyelids
- Difficult breathing
- Difficulty swallowing
- Diarrhea that is sometimes tinged with blood
- Hemorrhaging anywhere in the body
- Vision disturbances progressing to blindness
- Loss of motor skills
- Shortness of breath
- Shortness of breath
- Coughing (sometimes with brown mucus)
- Symptoms last over 90 days
- Weight loss
- Coughing up blood (with aspergilloma)
- Runny nose
- Hayfever-like symptoms
Aspergillosis in horses comes in many forms, but the most common are:
- Invasive pulmonary aspergillosis (IPA) the most common and most dangerous because it spreads rapidly to other parts of the body and vital organs
- Allergic pulmonary aspergillosis (ABPA) causes lung and allergy symptoms but no infection
- Chronic pulmonary and aspergilloma (CPA) causes same symptoms as ABPA but lasts more than 90 days
- Severe asthma with fungal sensitisation (SAFS) serious infection in horses with weakened immune systems
Causes of Aspergillosis in Horses
There are about 300 types of aspergillosis, with over 60 types that can cause disease. These are the types that are most commonly found in horses:
- Aspergillus fumigatus (most common)
- Aspergillus nidulans
- Aspergillus felis
- Aspergillus terreus
- Aspergillus flavus
- Aspergillus niger
- Aspergillus viridinutans
Diagnosis of Aspergillosis in Horses
The veterinarian will do a complete physical examination, which includes lameness check, temperature, respiration and pulse, blood pressure, and body condition score (rating on visual body weight and condition). The veterinarian will also check eyes, ears, nasal cavity, and teeth. In addition, a complete medical history is needed, including vaccination records, recent injury, and illnesses. An endoscopy to examine the guttural pouch is also necessary and can only be done while your horse is sedated.
This procedure includes inserting a long flexible tube with a camera (endoscope) into the throat to get a good view of whether there is anything growing in the guttural pouch. The veterinarian will take a tissue sample for microscopic examination. Also, head, neck, and chest x-rays are done next to get a detailed view of the guttural pouch, lungs, and neck. Lung infiltrates should be visible with x-rays. Laboratory tests include fungal and bacterial culture, serum IgE, complete blood count, chemistry analysis, serum precipitins for aspergillus, and a bronchoscopy with lavage.
Treatment of Aspergillosis in Horses
Treatment depends on the type of aspergillosis your horse has.
To treat IBPA, an antifungal medication such as posaconazole, itraconazole, caspofungin, or voriconazole is used in conjunction with corticosteroids.
For ABPA, the antifungal medication, itraconazole is used with a high dosage of long-term steroids with glucocorticoids.
Because CPA only affects horses already suffering from, and being treated for, an underlying lung condition, no other treatment is usually needed. However, if your pet is coughing up blood, more treatment is needed such as surgery or a drug called tranexamic acid. Additionally, angiography (injecting dye into blood vessels) can be used to find the site of bleeding which may be halted by shooting tiny pellets into the bleeding vessel. Patients with CPA with single aspergillomas generally do well with surgery to remove the aspergilloma, along with antifungal medication.
Patients with SAFS are normally on medications, such as inhaled and oral steroids, for an underlying condition. However, if there are any complications, the veterinarian may use antifungal drugs as well.
Recovery of Aspergillosis in Horses
For more serious and chronic cases of aspergillosis, antifungal medication may be continued indefinitely with frequent visits for chest x-rays and bloodwork. You will need to continue observing your horse daily for life to be sure the infection does not return.