Pest spotlight: Mites Subclass: Acari

Chigger (Trombiculidae). Photo: Susan Ellis, Bugwood.org

Mites, a diverse group of arthropods closely related to spiders and ticks, are generally harmless to humans.

However, specific mite species can lead to itching and biting. These itchy mites fall into two categories: parasitic and non-parasitic. Parasitic mites rely on a host to complete their life cycle and can provoke intense itching and irritation upon contact with human skin1. Non-parasitic mites also have the potential to cause itching in humans.

Understanding these mites is crucial for pest management professionals (PMPs), as many individuals often attribute mysterious insect bites to mites and insects, leading to unnecessary treatments.

Parasitic biting mites

Chiggers, also referred to as harvest mites or red bugs, are tiny arachnids belonging to the Trombiculidae family. Chigger larvae commonly are encountered during activities such as gardening or while walking pets in wooded areas.

When chigger larvae “bite,” they inject a digestive enzyme into the skin, which breaks down skin cells.

Subsequently, these larvae feed on the liquefied tissue, resulting in intense itching and red, raised welts or blisters. The itching can become noticeable several hours after the bite and may persist for several days.

Scabies mites (Sarcoptes scabiei [var.] hominis) are microscopic parasites that burrow into the skin, leading to severe itching and rash. Female mites tunnel into the skin to lay eggs. They are specific to humans and cannot survive on other animals. The transmission of scabies primarily occurs through close physical contact with an infected individual or by sharing personal items like clothing and bedding.

Northern fowl mite
(Ornithonyssus sylviarum). Photo: Protasov AN/shutterstock.com

Treatment usually involves the application of prescription medication directly to the affected areas.

Addressing scabies infestations falls outside the purview of PMPs, but it’s crucial to recognize the rash may be misidentified as bed bug bites. Therefore, a comprehensive inspection and monitoring protocol for bed bugs should precede any conclusions.

Bird mite bites can lead to itching and discomfort. For example, the northern fowl mite (Ornithonyssus sylviarum), the tropical fowl mite (O. bursa) and the chicken mite (Dermanyssus gallinae, also known as the poultry red mite) typically feed on bird blood. However, without their primary hosts, they may bite humans, causing irritation.

Found primarily in bird nests or areas frequented by birds, such as poultry houses, barns or attics, infestations in humans generally are temporary and resolve once the mites are removed or eliminated.
PMPs must exercise caution when dealing with the source, primarily birds. Bird species that are protected under the Migratory Bird Treaty Act cannot be controlled, nor can their nests be damaged, unless under specific conditions.

Moreover, bird mites are capable of attaching to and biting rodents, thus gaining access to homes where rodents hide or seek shelter. Therefore, it’s imperative to focus on pest-proofing tactics and rodent management to prevent bird mites from infesting human dwellings.

Rodent mites, which feed externally on the skin when they suck blood from a host, are commonly found on rodents such as mice, rats and squirrels. Humans may encounter tropical rat mites (O. bacoti) or other rodent mites when they come into contact with infested rodents or their nesting materials. They primarily feed on the blood of their host and can cause various issues for humans if they bite them.

Tropical rat mite
(Ornithonyssus bacoti). (Photo: 023 Dumitrache, Györke, Julien, Kondratjeva and Cadiergues)

Typically active at night, rodent mites will bite humans if they cannot find their primary host, causing redness, itching and sometimes allergic reactions. The best way to deal with them is by eliminating their primary hosts and applying approved pesticides such as crack, crevice and spot treatments to reduce their population in affected areas. Additionally, these mites have been observed in cases where people have rodents as pets, emphasizing the importance of proactive pest management in such environments.

Non-parasitic biting mites

Straw itch mite (Pyemotes tritici). (Photo: Eric Erbe, USDA Agricultural Research Service, Bugwood.org)

The straw itch mite (Pyemotes tritici), also known as the grain itch mite, is commonly found in stored grains, straws, hay and bird nests. Despite their microscopic size — measuring less than 0.3mm — these mites are capable of causing skin irritation and itching in humans. Their bites often are mistaken for those of other insects, such as mosquitoes or chiggers. While their bites are not considered dangerous, they can be extremely uncomfortable and may lead to secondary infections if scratched excessively5.

To minimize the risk of encountering straw itch mites, individuals should adopt precautions when handling stored grains, hay or straw, including wearing protective clothing and gloves. Furthermore, maintaining cleanliness and employing proper storage practices can effectively reduce the likelihood of infestation.

This P. herfsi female has an enlarged abdomen, known as physogastrism. (Photo: J. Med. Entomol. 43(3): 610Ð613 (2006))

In the event of skin irritation resulting from straw itch mite bites, individuals should resist the urge to scratch excessively. Instead, they should seek relief from properly labeled and proven over-the-counter anti-itch creams or antihistamines. Should symptoms persist or worsen, consulting a healthcare professional is recommended.

The oak leaf itch mite (P. herfsi), also known as the oak leaf gall mite, is another species capable of causing skin irritation and itching in humans. These mites primarily inhabit oak leaf galls, with abnormal growths on oak leaves resulting from certain insects’ feeding activities. Measuring less than 0.4mm, these mites often are too small to be visible to the naked eye. Like straw itch mites, their bites are not considered dangerous; however, they can cause extreme discomfort and lead to secondary infections if excessively scratched.

Scabies mite (Sarcoptes scabiei [var.] hominis). (Photo: Aliaksei Marozau/Shutterstock.com)

Encounters with oak leaf itch mites commonly occur when individuals handle infested oak leaf galls or materials containing these mites. This exposure often happens during outdoor activities like gardening, hiking or yard work, where individuals may interact with oak leaves or debris. Furthermore, these mites can hitch a ride indoors on clothing or objects that have been in contact with infested oak trees or leaf litter. Consequently, individuals may unknowingly introduce oak leaf itch mites into their homes or workplaces, potentially resulting in skin irritation and itching.

Control methods

The proper identification of mites is crucial, especially because these tiny pests can be mistaken for other things, leading to treatment failures or unnecessary treatments. Removing the host and modifying the environment to prevent mite infestations are the most effective methods for long-term control.

If pesticides are deemed necessary, they must be used judiciously and according to the label. Additionally, practicing good hygiene and cleanliness, such as regularly cleaning and vacuuming living areas, can help reduce the risk of mite infestations.

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from Pest Management Professional https://www.mypmp.net/2024/11/25/pest-spotlight-mites-subclass-acari/
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