Equide favors the least invasive techniques for treating sinusitis, with transnasal sinuscopy being the first choice. This involves examining and treating the nasal passages and sinuses with a small flexible camera. However, sometimes the location and/or extent of the condition requires us to make additional openings to address the issue thoroughly. These techniques remain minimally invasive and can make a crucial difference in selected cases.

Introduction: Case of Unilateral Nasal Discharge in a Friesian Horse

In early March 2025, a horse was referred to our clinic due to a unilateral non-foul-smelling nasal discharge on the left side. The owner also noticed difficulty eating hard feed, with significant spillage. The Friesian horse was sluggish, had lost weight, and appeared more withdrawn than usual. Initial treatment with Sputolysin had insufficient effect, warranting further investigation.

Diagnosis: Primary Mycotic Sinusitis in a Horse

On clinical examination, the horse was in good general condition, though slightly underweight. Breathing was normal, with no enlarged lymph nodes. There was clearly mucopurulent discharge from the left nostril.

Oral examination revealed minor dental issues, such as diastemata (gaps between molars) with mild gingivitis, but no evidence of a dental infection causing sinusitis. Imaging (X-ray) showed diffuse opacities and fluid levels in the sinuses.

Sinuscopy ultimately clarified the diagnosis: the sinuses contained thick debris and visible fungal colonies. Lab analysis confirmed growth of Aspergillus nidulans. Conclusion: primary mycotic sinusitis.

Light from scope seen through skull

Additional Bloodwork
Extensive blood tests provided more insight into the horse’s overall health:

• Muscle enzymes: CK (550 U/L) and LDH (863 U/L) mildly elevated

• Platelets: slightly increased (229–240 x10⁹/L)

• Glucose: low (1.94 mmol/L), likely due to transport delay

• Kidney values and SDMA: within normal limits

• Serum Amyloid A (SAA): <0.1 mg/l, no systemic inflammation

Blood values confirmed a localized inflammatory process with no signs of systemic infection.

Treatment of Primary Mycotic Sinusitis in a Horse

Treatment began with a pre-operative course of antibiotics and anti-inflammatories. A surgical procedure was performed to create a sinus flap, providing direct access to the sinuses. The area was flushed, fungal plaques and affected bone were removed, and the sinuses were treated with the antifungal nystatin.

In the weeks following surgery, regular transnasal sinus flushes were performed, alternated with local antifungal applications such as Daktarin, Canestene, and Ampho-Moronal. Necrotic tissue was mechanically removed (curettage) as needed. Each treatment was tailored based on the latest endoscopic findings. To ensure proper distribution of antifungal agents in anatomically altered sinus compartments, Daktarin powder was also applied using a pressure sprayer.

Treatment Result of Primary Mycotic Sinusitis in a Horse

During the last check-ups (up to June 19), the sinuses had fully healed with no recurrence of fungal growth. The surgical area healed nicely and mucosa was no longer swollen. Anatomical changes remain visible but are not expected to cause problems.

Conclusion about Primary Mycotic Sinusitis in a Horse

Thanks to early diagnosis, intensive treatment, and close monitoring, the horse made a full recovery from this rare but serious sinus fungal infection. The horse is symptom-free and the long-term outlook is excellent.

Want to Know More?
Do you have questions about sinusitis in horses or would like a consult for your horse with nasal discharge? Feel free to contact us!

FAQ

1. What is equine mycotic sinusitis?
Mycotic sinusitis is a fungal infection of the nasal sinuses, often caused by fungi such as Aspergillus. It leads to nasal discharge, swelling, respiratory difficulties, and discomfort in the nasal/oral region.

2. How does Equide diagnose this condition?
Equide employed transnasal sinoscopy, radiographic imaging, and laboratory fungal cultures to detect fungal colonies, confirming the diagnosis of primary mycotic sinusitis.

3. What is the treatment protocol and outcome?
The treatment included surgical access via a sinus flap, flushing, removal of fungal-affected tissue, and topical antifungal agents (nystatin, Daktarin). With diligent follow-up and care, the horse fully recovered with no fungal recurrence.