You've probably heard of dust mites, which can affect both humans and pets. They cause asthma, eczema and allergic rhinitis in people and allergic skin disease in dogs and cats. However, there are many other types of mites including storage mites (also known as grain mites), which can be found in pet food AND human food. Storage mites in your pet dog or cat’s food can also adversely affect their health and although they are impossible to remove from the home completely, there are steps you can follow to reduce their prevalence. In this article we will discuss how a storage mite allergy can cause skin irritation problems in dogs and cats (such as atopic dermatitis), why storage mites are found in dry dog food and cat food and how you can prevent storage mites in your pet food.
WHAT ARE STORAGE MITES?
Storage mites are microscopic creatures 0.2-0.5mm in length which belong to the arthropod family, the same as ticks and spiders. They cannot be seen easily with the naked eye and are found near to their food sources; storage mites are mainly found in cereal/grain dry pet food. There are several types of storage mites with Acarus, Tyrophagus (commonly called mould or grain mites) and Lepidoglyphus species being the most common in the UK.
WHY ARE STORAGE MITES A PROBLEM FOR MY DOG OR CAT?
For most healthy pets, storage mites in dry dog food and cat food will not pose a problem. However, for an immune system allergic reaction to occur, the protein (in this case the storage mite or mite waste products) must have been presented to the immune system prior to the allergy developing – so for an allergic reaction to happen, your dog or cat must have been exposed to it before. If the animal is predisposed to developing allergic reactions, its chances increase every time it is exposed to that particular protein, so keeping the environment as free of storage mites as possible is a good idea.
For those dogs and cats that are allergy sensitive or for pets with skin disorders a storage mite allergy hypersensitivity is becoming a common cause of allergic skin conditions (atopic dermatitis) and ear inflammation (otitis) in dogs and cats. This means that for these pets, exposure to storage mites can trigger or exacerbate very itchy skin or ears. Animals can react to both the protein in the mites themselves and their faeces. Mites can also carry fungal spores and pathogens. Mites are impossible to totally eradicate from dry dog and cat food and the wider environment but there are ways to reduce their numbers and ensure contamination is contained.
WHERE ARE STORAGE MITES FOUND?
These mites can be found in a variety of foods including cheese, flour, cereals, biscuits, baby food and dry dog or cat food. In one study (Brazis et al, 2008) ten different brands of dry dog food specifically formulated for dogs with skin problems were analysed. Upon opening the sealed bags 2 out of 10 already had storage mites present. After 5 weeks in optimal conditions (a warm, humid environment) 9 out of the 10 bags of the dry dog food contained storage mites. This is why it is advised to store dry food in airtight containers and purchase smaller bags which can be used quicker. Although mites cannot usually be seen by the naked eye, infested food may smell ‘minty’ and with large infestations you may see tiny white or pink specks moving about on the food.
Storage mites cannot be seen easily with the naked eye and are found near to their food sources; storage mites are mainly found in cereal/grain dry pet food.
HOW IS A STORAGE MITE ALLERGY DIAGNOSED?
If your dog or cat is showing signs of an allergy (usually itchy skin and dermatitis) which occurs all year round (rather than a seasonal problem) then storage mite allergies may be considered. You could then try swapping your pet dog or cat from a dry food diet to a wet diet for a few weeks to see if things improve or your vet may suggest some allergy tests. Allergy tests can be in the form of serum tests or skin tests. Serum testing involves taking some blood to look for antibodies. Antibodies are produced by the immune system to protect against allergens – which in this case are the mites (‘allergen’ is the term used to describe a substance that your pet is allergic to). Intradermal skin testing involves shaving a small area of your pet and injecting small amounts of different allergens. If your pet is allergic to one of the allergens then the injection site will show a reaction (redness and swelling). Unfortunately, with skin and serum testing there can be some cross-reactions between house dust mites and storage mites. This means that your pet might be allergic to one type but not the other, or both but it can be difficult to determine which mite they are reacting to.
HOW CAN I PREVENT STORAGE MITES FROM GETTING INTO MY DOG OR CAT’S FOOD?
Buying smaller bags of food that can be consumed within 2 weeks can help the food stay fresher and reduce mite infestation. Alternatively, special care and considerations can be made for the storing of dry dog and cat food, for example decanting the food into an airtight container has been shown to reduce contamination by mites considerably by up to 3 months. However, before doing so make sure the container is washed in hot water with pet safe washing-up liquid before use (to make sure of no contamination prior to introducing the dry food into the container).
Further steps to reduce storage mite allergy and infestation in dog and cat food:
- Do not use mouldy, dusty, out of date food or food from bags that have been open for more than a few weeks.
- Store your food in cool, dry, dark places – away from direct sunlight, radiators or boilers where the food may sweat and start to go mouldy. Mouldy food will encourage infestation of the mould mite Tyrophagas putrescentiae.
- Wipe your pet’s face after eating to remove any food residue and possible mites.
- Clean and disinfect the plastic food container in hot water between every bag of food and discard any bits of food residue before refilling the container with a fresh batch of food.
- Consider changing to a grain-free diet or one that uses higher quality carbohydrates such as rice, as this may be helpful in terms of reducing exposure to storage mites.
WHAT VETERINARY TREATMENT IS THERE AVAILABLE FOR MY CAT OR DOG IF THEY ARE ALLERGIC TO STORAGE MITES?
If measures above do not seem to help you could always consider swapping your dog or cat to a wet food diet. Alternatively, freezing the dry food to kill the mites is often recommended. However, studies have found that although freezing the food can prevent reproduction by the mite, any existing mites will still pose a risk as an allergen. Freezing freshly bought dry food in small bags may be a good way of preventing mite populations from increasing but it seems that an air tight container can do the same job.
If your pet shows that it is positive for an allergic profile that relates to storage mites in dry dog food or cat food formulation then a course of Immunotherapy vaccines may be recommended by your vet. Immunotherapy, also known as desensitisation involves the injection of small amounts of the problematic allergen (in this case storage mite protein) into your pet over a period of a few months. Each injection contains slightly higher levels of the problematic allergen in the hope that your pet’s immune system will be able to build up a tolerance to the allergen and show a reduced response when exposed to the storage mites in the environment.
Further reading & references:
Avacta Animal Health – Indoor Allergens
Evaluation of storage mite contamination in commercial dry dog food
House dust and storage mite contamination in commercial dry dog food stored in open bags and sealed boxes in 10 domestic households
Laboklin – Storage Mites
Preventing and controlling mites in stored cereals
Allergy UK - Immunotherapy