Histoplasmosis in Dogs and Cats: A 2025 Veterinary Guide to Fungal Infection, Symptoms, and Treatment 🐶🐱🦠

Hello, I’m Dr Duncan Houston BVSc. Histoplasmosis is a dangerous fungal infection that affects both dogs and cats—especially those exposed to environments rich in bird or bat droppings. In this 2025 guide, I’ll help you recognize the signs, understand how this disease spreads, and what to expect from treatment and recovery. 🩺

🌱 What Is Histoplasmosis?

Histoplasmosis is caused by Histoplasma capsulatum, a fungus that thrives in warm, moist, nitrogen-rich soil—often contaminated by bird or bat feces. It spreads through the air, making it easy to inhale unknowingly while outdoors or exploring wooded, river valley, or cave areas. 🦇🌳

Common U.S. regions: Ohio, Mississippi, and Missouri River valleys. 🗺️

🦠 How Infection Occurs

• 🐾 Inhaled spores settle in the lungs and begin to grow
• 🫁 The lungs are typically the first organ affected
• 🔁 Fungus can then spread via blood to the GI tract, liver, spleen, eyes, lymph nodes, and more
• 🐱 Cats are more vulnerable than dogs

⚠️ Symptoms of Histoplasmosis

General signs:

• 📉 Weight loss
• 🍽️ Loss of appetite
• 🌡️ Fever
• 😴 Lethargy

In dogs:

• 💩 Diarrhea, loose stool, or straining

In cats:

• 😮‍💨 Coughing, labored breathing, nasal discharge

When multiple organs are involved:

• 🩸 Pale gums (anemia), yellow eyes/skin (icterus)
• 🧼 Draining skin lesions or ulcers
• 🦠 Enlarged lymph nodes or spleen
• 👀 Eye swelling, vision changes, or blindness

🔍 Diagnosing Histoplasmosis

• 🩺 Physical exam + history
• 🧪 Blood work: may show anemia, low albumin, low platelets
• 🦠 Fungal cytology: identifying organisms under the microscope
• 🧫 Antigen/antibody testing: confirms exposure or immune response
• 🖥️ Imaging: X-rays for lung damage, ultrasound for liver/spleen

💊 Treatment & Monitoring

• ⏳ Requires 6+ months of treatment
• 💊 Antifungals: Itraconazole, Fluconazole, Amphotericin B
• 💉 Supportive care: fluids, feeding tubes, oxygen if needed
• 🧪 Regular blood tests to monitor liver/kidney function and response

Common side effects: vomiting, poor appetite, diarrhea, or kidney/liver strain.

🔁 Can Histoplasmosis Come Back?

• ⚠️ Yes—relapse is possible even after long treatment
• 🩺 Recheck exams and tests are needed for months after stopping medication

📈 Prognosis

• 😺 Pets with lung-only disease often recover well
• ⚠️ Pets with multiple organ involvement have a guarded prognosis
• 🩺 Untreated symptomatic pets usually do not survive

🛡️ Prevention

• 🚫 Avoid exposure to bird/bat droppings (no cave hiking!)
• 🐕 Supervise outdoor play in endemic regions
• 🧼 Keep yards clean and rodent-free

📱 Ask A Vet: Support for Fungal Disease

• 🩺 Help interpreting lab results or X-rays
• 💊 Guidance on antifungal side effects
• 📋 Monitoring schedule support
• 🥣 Nutrition advice during long-term illness

For personalized help, visit AskAVet.com or download the app. 📲🐶🐱

✅ Summary: Histoplasmosis in Pets

• 🦠 Caused by inhaling fungal spores from bird/bat droppings
• 🫁 Begins in lungs, can spread throughout the body
• 🐱 Cats are more commonly affected than dogs
• 🧪 Diagnosis requires imaging, lab work, and sometimes biopsy
• 💊 Treatment takes 6+ months and frequent monitoring
• ⚕️ Early diagnosis improves survival odds

Histoplasmosis is rare but serious. If your pet shows unexplained weight loss, fever, diarrhea, or labored breathing, speak with your vet promptly. 🩺

— Dr Duncan Houston BVSc