Key points
- A microscopic mite that lives and breeds inside adult bees' tracheae.
- Invisible to the naked eye: diagnosis requires dissection under a microscope.
- Non-specific signs: crawling bees, "K-wings", winter losses.
- Less of a concern today than varroa, but worth checking after unexplained losses.
Acarapisosis is caused by a tiny mite that settles in the bee’s respiratory system. It caused heavy losses in the early 20th century, notably in Britain, before becoming far less conspicuous.
The agent
Acarapis woodi measures about 0.1 to 0.2 mm. Females enter the thoracic tracheae of young bees, only a few days old, and breed there. They feed on haemolymph through the tracheal wall, which becomes stained and blocked1.
Transmission is by contact between bees, especially in the winter cluster.
Symptoms
Signs are non-specific and only appear with heavy infestation:
- Bees crawling in front of the hive, unable to fly.
- Wings spread and misaligned, known as “K-wing”.
- Higher mortality in winter and early spring.
Diagnosis
Only dissection gives an answer: the head and first thoracic ring are removed to examine the tracheae under a stereo microscope. A healthy trachea is clear; an infested one shows brown patches and mites2.
What to do
- Have bees tested after unexplained winter losses.
- Favour tolerant lines; susceptibility varies widely with genetic origin.
- Keep colonies strong.
Some varroa treatments based on formic acid or thymol also act on Acarapis1. Only use medicines authorised in your country, following the label.
References
- Sammataro D., Gerson U., Needham G. (2000). Parasitic mites of honey bees: life history, implications, and impact. Annual Review of Entomology 45: 519-548.
- WOAH. Terrestrial Manual, chapter 3.2.1: Acarapisosis of honey bees (infestation with Acarapis woodi).
- FAO, IZSLT, Apimondia, CAAS (2021). Good beekeeping practices for sustainable apiculture. FAO Animal Production and Health Guidelines No. 25.