🪰 Vet Guide 2025: Cuterebriasis in Dogs and Cats – Fly Larva Skin Infections Explained 🐶🐱

By Dr Duncan Houston, BVSc

Cuterebriasis is a parasitic skin condition caused by the larval form of the Cuterebra fly. Although it’s an uncommon diagnosis, pet owners are often startled when their dog or cat develops a mysterious swelling that turns out to be a living parasite just beneath the skin. This guide covers everything you need to know about how Cuterebra larvae infect pets, what signs to look for, and how your vet can safely remove them. 🩺

🔬 What Is Cuterebriasis?

Cuterebriasis is the infestation of the skin by the larva of the Cuterebra fly. This parasitic condition primarily affects animals that spend time outdoors—especially curious cats and dogs that explore near rabbit or rodent burrows. 🐾

🐛 About Cuterebra Flies:

• 🪰 Large, non-feeding adult flies
• 🥚 Lay eggs near animal nests or burrows
• 🌡️ Eggs hatch in response to an animal’s body heat

The larva enters the host through the mouth, nose, or even a skin wound. Once inside, it migrates to subcutaneous (beneath the skin) tissue and creates a breathing hole (fistula) to survive. 😬

📍 Where & When Does Cuterebriasis Occur?

This parasite is most commonly encountered in:

• 📆 Late summer and fall
• 🌳 Outdoor environments near rabbit or rodent activity

🧭 Commonly Affected Sites:

• 👂 Head and neck (pets often sniff around burrows)
• 🐕 Anywhere grooming occurs, allowing larvae to be ingested or enter wounds

Hosts act as incubators. After about a month, the larva exits the skin, drops into the soil, and matures into an adult fly. 🪲

👁️ What Are the Signs of Cuterebriasis?

Pet owners typically notice a strange swelling with a small central hole. Symptoms can include: 👇

• 📍 Localized lump or bump under the skin
• 💢 Redness, swelling, or irritation
• 👅 Excessive grooming or licking at the site
• 😿 Pain when touched
• 💧 Discharge or pus if the site is infected

The central hole serves as a breathing port for the larva. If you see movement or feel a firm, tube-shaped object beneath the skin, it could be a larva. ❗

🩺 Diagnosis & Veterinary Removal

Diagnosis is typically straightforward. Your veterinarian will inspect the lesion and look for the telltale breathing hole. In many cases, removal is simple but must be done with care: 🧠

✅ Removal Procedure:

• 🪛 Enlarge the breathing hole slightly
• 🔍 Use forceps to extract the larva in one piece
• 🧼 Flush the wound with saline if needed
• 💊 Apply topical antibiotics or debride tissue if the area is damaged

Never squeeze the lesion! Rupturing the larva can increase inflammation and infection risk. The body may react severely to larval fragments. ❌

💊 What Happens After Removal?

The site may take longer to heal than expected because the larva creates a cavity. Healing is typically uneventful, but in some cases your vet may recommend:

• 💉 Pain relief or anti-inflammatory meds
• 🧼 Daily wound care at home
• 🧴 Antibiotic ointments
• 🦺 E-collar to prevent licking

The goal is to allow healthy granulation tissue to fill in the space left by the parasite. 🧬

🚨 Rare Complications of Cuterebriasis

While most cases are limited to the skin, some rare and serious complications have been documented due to larval migration: 🧠

• 👁️ Ophthalmomyiasis: Infection in or around the eye
• 🧠 Cerebral cuterebriasis: Brain migration causing seizures or neurologic signs
• 💨 Respiratory tract migration
• 🩸 Systemic issues like DIC (disseminated intravascular coagulation) or SIRS (systemic inflammatory response)

These complications are very rare but highlight the importance of prompt veterinary intervention. ⚠️

🛡️ How to Prevent Cuterebriasis

While you can’t eliminate all risk, especially in outdoor pets, here are some ways to reduce the chances of infestation: 🌳

• 🏡 Keep pets indoors during peak fly season (late summer–fall)
• 🐾 Supervise outdoor time and avoid rodent or rabbit burrows
• 🧼 Regular grooming and skin checks for bumps or wounds
• 🩺 Contact your vet or Ask A Vet if you spot any suspicious swelling

📲 Ask A Vet for Fast Help

If you’ve noticed a suspicious bump or breathing hole on your pet’s skin, don’t wait—AskAVet.com offers real-time vet support. 🐕💬

With the Ask A Vet App, you can:

• 📸 Upload photos for instant review
• 💬 Chat with a vet about wound care or parasite risk
• 📅 Get follow-up care and wound healing advice

Save time and get expert support—all from your phone. 🐾📱

📝 Final Thoughts

Cuterebriasis is a surprising and strange parasitic condition—but with fast recognition and simple veterinary care, most pets recover quickly. If you notice a swelling with a central hole, especially in outdoor pets, don’t squeeze it—call your vet. 🐕🩺

And if you need help right now, head to AskAVet.com for 24/7 advice. Let’s keep those bumps from becoming bugs! 🪰🐾