Storage mites (also called grain mites, mould mites and cheese mites) are a close relative to the more well-known dust mite. They feed finely ground grains, wheat germ, yeast, cheese, powdered milk, flour, dry dog and cat food as well as mould spores which grow on food.
The most common species of storage mite include:
- Tyrophagus putrescentiae – Mould mite, storage mite or cheese mite
- Lepidoglyphus destructor – Storage mite
- Acarus siro – Flour mite
All storage mites belong to the arachnid family, the same order as spiders and ticks and are between 0.3 – .06 mm in length.
The mites thrive in warm and humid (over 65-85% humidity) environments, and under the right conditions, the entire life cycle takes two weeks, which means a severe infestation can quickly develop. Like their dust mite cousins, storage mites are a common source of allergies in dogs and cats. Allergies in humans often cause symptoms such as a runny nose, sneezing, and watery eyes, cats and dogs are more prone to developing skin-related symptoms such as itching and scratching.
It is easy to assume that storage mites occur at the food processing plant. However, one study found that only one out of ten unopened bags of pet food contained storage mites, the rest became infested with the mites once inside the owner’s houses.
There is a growing interest in these mites because several species are a known source of allergies in people and pets. Both the storage mite and their feces contain several recognised allergens. In humans, they cause skin and respiratory symptoms.
Signs of storage mite infestation
It is not possible to see the mites with the naked eye. The most common sign of storage mite infestation is the presence of brown dust (mite dust) on or close to the source of infestation and food which has a sickly sweet or lemony smell.
- Non-seasonal itching and scratching, especially around the face and ears
- Patches of hair loss
- Redness and inflammation
- Inflammation of the ear (otitis)
- Constant scratching can damage the skin and cause a secondary skin infection
Diagnosis of storage mite allergies
The veterinarian will perform a physical examination and obtain a medical history from you. Non-seasonal itching is a common finding in cats with allergies.
Food trials: The cat is switched from its normal diet to a hypoallergenic diet to see if symptoms resolve, no other food or treats can be given to the cat during this time. If symptoms resolve, the cat will go back to its normal diet to see if symptoms return. What this will tell the veterinarian is that the food is the source of the allergy, but it may not be recognised that it is the mite and the mite feces that is the problem and not the food itself.
Skin prick test: An area of the cat’s fur is shaved, and the exposed skin is pricked with minute amounts of allergens to see if there will be a local reaction such as itching and a rash.
Serum test: To measure the levels of IgE antibodies to the storage mite allergens.
The goal of treatment is to manage the cat’s symptoms as well as manage the infestation. This will include:
- Corticosteroids to control itching
- Antibiotics if a secondary bacterial skin infection has developed
- Allergen immunotherapy involves the regular administration of gradually increasing doses of the causative allergen. It can be given to the cat as an injection or drops under the tongue (sublingual). The purpose of immunotherapy is to change the way the cat’s immune system responds to allergens so that it no longer responds.
- Consider switching to canned cat food or home made cooked or raw diet
- Store dry food in an airtight container in a cool and dry area
- Buy small bags of food (cat and human) and store in the freezer, this won’t kill the mites but will prevent them reproducing
- If freezer space is an issue, decant dry food from the bag and store in an air tight container, avoid pouring the dusty debris from the bottom of the bag into the container
- Wash the storage container in hot soapy water and thoroughly dry before you add new food
- Do not top-up food in storage containers, wait until all the food in the container has been used and then wash the container well with warm water and dishwashing liquid, turn upside down to drain, and then place in sunlight for half an hour
- Dispose of pet food bags immediately, in the outside garbage bin
- Always use food before it has reached its use-by date
- Reduce humidity in the house; storage mites thrive in humidity of 65-85%
- Discard soiled food
- Wash pet food bowls in hot soapy water once a day
- Vacuum and mop where pets eat to remove any debris