Favus (Ringworm) in Ducks: Crusty Skin and Fungal Infection

Favus is a form of dermatophytosis, also called ringworm, caused by a fungus rather than a worm. In birds, the classic organism is Microsporum gallinae. The fungus lives in keratinized tissues such as the outer skin and feather follicles, where it can create dry, chalky, crusted plaques. Favus is reported most often in chickens and turkeys, but ducks can also develop similar fungal skin disease, especially when skin is damaged or housing hygiene is poor.

In ducks, lesions often start on the face or other thinly feathered skin. Pet parents may notice white or gray crusts, thickened skin, patchy feather loss, and a rough, scaly appearance. Some birds seem only mildly bothered, while others rub at the area, lose condition, or become more vulnerable to secondary skin infection.

This condition matters for two reasons. First, it can spread through a flock by direct contact or contaminated housing, feeders, bedding, and equipment. Second, ringworm is considered zoonotic, meaning people can sometimes catch it from infected animals or contaminated surfaces. That does not mean every exposed person will become infected, but it does mean careful hygiene and prompt veterinary guidance are important.

Favus is caused by a dermatophyte fungus, classically Microsporum gallinae in birds. The fungus spreads by direct contact with an infected bird or by contact with contaminated bedding, nest material, perches, fencing, feeders, transport crates, or grooming tools. Fungal spores can persist in the environment, which is one reason outbreaks can keep cycling through a flock if cleaning is incomplete.

Ducks are more likely to develop infection when the skin barrier is already stressed. Small wounds from pecking, rubbing, parasites, or rough housing surfaces may give the fungus an easier entry point. Damp, crowded, dirty, or poorly ventilated housing can also support spread. Birds under stress, in poor body condition, or dealing with another illness may have a harder time clearing infection.

Not every crusty lesion is favus. Your vet may also consider mites, lice, bacterial infection, trauma, poxvirus, nutritional problems, or irritation from the environment. That is why a hands-on exam and targeted testing matter before starting treatment.

Your vet usually starts with a physical exam and a close look at the pattern of lesions. Favus often causes dry, adherent crusts on the head and other exposed skin, but many skin diseases can mimic it. In ducks, your vet may also ask about flock history, recent additions, housing moisture, parasite exposure, and whether any people or other animals in the home have developed suspicious skin lesions.

To confirm the cause, your vet may collect skin scrapings, crust material, or feathers for microscopic review and fungal culture. Culture is especially helpful when the diagnosis is uncertain or when several birds are affected. Some clinics may also use cytology, PCR through a reference lab, or biopsy if lesions are unusual or not responding as expected. A Wood's lamp can sometimes help screen for ringworm in some species, but a negative result does not rule dermatophyte infection out.

Because other contagious diseases can look similar, diagnosis often includes ruling out mites, bacterial dermatitis, and avian pox. If one duck is affected, your vet may recommend checking flockmates too. That broader approach can save time, reduce reinfection, and help you build a realistic cleaning plan.

Prevention starts with clean, dry housing. Replace wet bedding promptly, improve drainage around water areas, and keep ventilation adequate without creating harsh drafts. Crowding increases skin trauma and contact spread, so giving ducks enough space can help lower risk. Regularly cleaning feeders, waterers, and shared equipment also matters because fungal spores can persist in the environment.

Try to reduce skin damage whenever possible. Check for bullying, rough wire, sharp edges, mites, and other conditions that can break the skin barrier. Quarantine new birds before mixing them with the flock, and watch closely for crusty facial lesions, feather loss, or unexplained skin changes during that period.

Because ringworm can spread to people, use gloves when handling suspicious lesions, wash hands well after contact, and keep children or immunocompromised family members away from affected birds until your vet advises otherwise. If one duck is diagnosed, ask your vet for a flock-level cleaning and monitoring plan. That step is often what prevents repeat cases.