Aspergillus niger

What is Aspergillus niger?

Aspergillus niger is a filamentous fungus consisting of branched hyphae that form a dense mycelium. It forms black spore heads consisting of many individual spores that can easily spread in the air. The spores are very resistant to heat, dryness and disinfectants and can survive in the environment for a long time.

Aspergillus niger is an opportunistic pathogen that normally does not cause infection unless the host's immune system is weakened or there is an injury to the mucous membranes or skin. It can cause various diseases in humans, such as pneumonia, sinusitis, otitis media or keratitis. It can also trigger allergic reactions, such as asthma or allergic bronchopulmonary aspergillosis.

How can Aspergillus niger infect dogs?

Dogs can ingest Aspergillus niger by inhaling or swallowing the spores that are present in the air or soil. Dogs that like to dig in mulch made of leaves or moist soil or spend a lot of time outdoors are particularly at risk. The spores can then settle in the dog's nasal cavities or gastrointestinal tract and cause an infection.

The most common form of aspergillosis in dogs is nasal aspergillosis, which is caused by Aspergillus fumigatus, but Aspergillus niger can also be involved. Nasal aspergillosis mainly affects the nasal cavities and paranasal sinuses of the dog and leads to chronic inflammation and tissue destruction.

The symptoms of nasal aspergillosis are

• Chronic nasal discharge, which can be yellow-green or bloody
• sneezing
• Pain in the face or nose
• Swollen nose
• Depigmentation or ulcers on the nasal surface
• Loss of appetite
• Weight loss

Nasal aspergillosis can be difficult to diagnose because it is often confused with other causes of chronic rhinitis, such as tumors, foreign bodies or bacterial infections. The veterinarian may perform various tests to make the diagnosis, such as X-rays or CT scans of the nose, rhinoscopy with a camera, tissue biopsy or culture of the nasal discharge.

Disseminated aspergillosis is a rarer form of infection in which the fungi can spread via the blood to other organs, such as the lungs, bones, bone marrow, lymph nodes or central nervous system. This form occurs more frequently in German Shepherds and has a poor prognosis.

The symptoms of disseminated aspergillosis are

• Fever
• pain
• lameness
• vomiting
• anorexia
• weight loss
• swelling of lymph nodes
• Nerve disorders

Disseminated aspergillosis can also be difficult to diagnose as it causes non-specific symptoms that depend on organ involvement. The veterinarian may perform blood tests, x-rays, ultrasounds or other imaging tests to confirm the diagnosis.

How is Aspergillus niger treated in dogs?

Treatment of Aspergillus niger in dogs requires professional care from a veterinarian and can be lengthy and costly. Treatment depends on the form and severity of the infection, but is usually based on the administration of antifungal drugs to kill the fungi.

The oral administration of antifungal drugs, such as itraconazole, is the first choice for the treatment of nasal aspergillosis. These drugs must be administered over several weeks or months to achieve a cure. However, they can have side effects, such as liver damage, gastrointestinal complaints or skin reactions.

An alternative or complementary treatment for nasal aspergillosis is the topical application of antifungal agents directly into the dog's nose. This can be done by nasal irrigation with a solution of clotrimazole or enilconazole, performed under anesthesia. This method has the advantage of delivering a higher concentration of the active ingredient to the site of infection and has fewer systemic side effects.

Disseminated aspergillosis is more difficult to treat and often has a poor prognosis. Oral administration of antifungal agents can be tried, but it is often ineffective or inadequate. In some cases, surgical removal of the affected organs or tissues may be necessary to control the infection.

How can you prevent Aspergillus niger in dogs?

Prevention of Aspergillus niger in dogs is not always possible as the fungus is ubiquitous in the environment and cannot be completely eliminated. However, there are some measures that can reduce the risk of infection, such as

• Avoid letting your dog dig around in damp or moldy areas, such as leaf mulch or compost piles.
• Regularly clean your dog's bowls and toys with hot water and vinegar or bleach to prevent mold growth.
• Keep your dog's immune system healthy by feeding him a balanced diet, deworming and vaccinating him regularly and protecting him from stress.
• Take your dog to the vet immediately if you notice any signs of nasal or disseminated aspergillosis, such as nasal discharge, sneezing, pain or fever.