fungal disease Tarantula, Wolf Spider

Skin fungal infections in tarantulas

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Definition Signs Causes Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

Skin fungal infections in tarantulas are infections caused by microscopic fungi that develop on the tarantula's exoskeleton (the rigid outer shell). These fungi often thrive in environments that are too humid or poorly maintained. In tarantulas, skin does not exist as it does in mammals; instead, the outer cuticle is affected, which can weaken the animal and interfere with shedding. While poorly documented in scientific literature, this condition is regularly reported by breeders and veterinarians specializing in exotic animals.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Scabs and skin lesions Loss of appetite Reduction Non-healing wound Behaviour change Refusing to move

Discolored patches or zones appear on the exoskeleton, sometimes whitish, grayish, or greenish, with a fuzzy or powdery appearance in places. Small lesions or softened areas may develop, sometimes accompanied by an unusual odor. The tarantula may become less active, refuse to eat, or remain huddled in a corner of its enclosure. In advanced cases, the next molt may be difficult, incomplete, or even fatal if the animal becomes trapped in its old cuticle.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

The infection results from the proliferation of opportunistic fungi (molds) naturally present in the environment, which colonize the cuticle when conditions are favorable. A wound, a recent molt with a still-fragile cuticle, or general weakening of the animal can facilitate fungal establishment.

Excessive and poorly controlled humidity in the enclosure is the main risk factor. A soiled substrate that is infrequently changed or contaminated by decomposing food debris also promotes fungal growth. Poor ventilation that prevents evaporation of stagnant moisture, a recent wound to the exoskeleton, or a tarantula already weakened by stress or a difficult molt further increase the risk.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

Diagnosis relies mainly on careful observation of the exoskeleton by the owner, then confirmed by a veterinarian specializing in exotic animals. The veterinarian may take a surface sample for microscopic examination or fungal culture to identify the fungus responsible and rule out other possible causes of skin lesions.

Treatment

Treatment centers on correcting husbandry conditions (reducing excess humidity, cleaning the terrarium) and, if necessary, applying a topical antifungal suitable for invertebrates, prescribed by a veterinarian. Temporary isolation of the affected animal may be advised to limit any risk of spread in a group setting.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

Maintaining humidity levels appropriate to the species—neither too dry nor too wet—is essential. The substrate should be changed regularly, uneaten food and waste removed promptly, and the terrarium should be well-ventilated to prevent moisture buildup. Avoiding injury to the animal during handling and monitoring the exoskeleton after each molt are also recommended.

Possible complications

An untreated infection can spread and weaken the exoskeleton over time, making the next molt dangerous. In severe cases, the animal may become stuck during molting or develop a secondary infection, which can be fatal.

When to see a veterinarian

Appearance of unusual, fuzzy, or discolored patches on the exoskeleton.

Abnormal odor from the terrarium or the animal.

Marked decrease in activity, refusing food for an extended period.

Difficulty observed during a molt, with the animal partially stuck in its old cuticle.

Prognosis

The prognosis is generally good if the infection is detected early and husbandry conditions are corrected quickly. It becomes more guarded in cases of complications during molting or delayed treatment.

Frequently asked questions

Are skin fungal infections common in tarantulas?

They remain relatively rare if breeding conditions are correct, but occur more frequently if humidity is poorly controlled.

Can I treat my pet myself with an over-the-counter antifungal product?

No, it is strongly advised against applying any product without veterinary advice, as tarantulas are very sensitive to certain substances that can be toxic to them.

Can a fungal infection be transmitted to other tarantulas in the same breeding facility?

Yes, a humid environment conducive to fungal growth can promote contamination of other individuals sharing similar conditions, which is why isolating the affected animal is important.

Should I be worried if my tarantula is about to molt and is showing spots?

Yes, it is preferable to have the animal checked before moulting, as a fungal infection can seriously complicate this delicate period.