Information about the Kentucky State University Cooperative Extension Program 2024

Tracheal Mites Drs. Katherine Kamminga & Thomas Webster

The tracheal mite, Acarapis woodie (Rennie) (Fig. 1), is a parasite that lives and reproduces inside the tracheal tubes (breathing tubes) (Figs. 2 & 3) of adult bees. The mites are microscopic and infect workers, queens, and drones. The infection begins when the mites enter the trachea via the first thoracic spiracle of young adult bees (Sammataro et al. 2013). Adult mites pierce the tracheal wall with their piercing-sucking mouthparts and feed on the hemolymph (insect blood), which depletes the insect of nutrients. High numbers of tracheal mites reduce the bee's ability to breathe and may interfere with gas exchange and the insect's oxygen requirements for flight muscles (Delfinado-Baker 1988, Harrison et al. 2001). Tracheal mite infections can make the bees more susceptible to pathogens, which decreases their lifespan and reduces honey production as well as winter survival (McMullan and Brown 2009, USDA 2016).

There are three different species of mites in the genus Acarapis: A. woodie, A. dorsalis, and A. externus. Only A. woodie mites infest the trachea and are a pest of honey bees. The other species are found on the exoskeleton of the European honey bees and feed on the hemolymph (Somerville 2011, USDA 2016). However, these species do not appear to have as negative of an impact on the bees as A. woodie.

In 1905, an unknown disease began afflicting nearly every bee hive on the Isle of Wight, United Kingdom, resulting in an almost 100% loss of the colonies on the island (Adam 1968). Although the cause was unclear, the disease was named the Isle of Wight Disease. In 1921, Rennie discovered and described the tracheal mites, which he believed to be the culprit of the Isle of Wight Disease. This disease was later renamed acarine disease.

Wight Disease. This disease was later renamed acarine disease.

After their initial discovery on the Isle of Wight, tracheal mites spread throughout Europe during the early to mid-1900s. To prevent the tracheal mite from invading North America, the United States government implemented the Federal Honey Bee Act of 1922, which restricted honey bee importation from countries that had the mite. However, the mite was discovered in Mexico in 1980, then in Texas in 1984 and Kentucky in 1989. It quickly spread throughout the U.S., and initial mite infestations resulted in 100% colony loss in some apiaries (Moore et al. 2015). At present, the mite isn't thought to be harming hives in the U.S. The reasons for the decreased virulence may be due to honey bees' increased resistance (Adam 1968) or the treatments used to treat Varroa mites.