Collecting dust mites
By Gary Baird
As I read Maurice Smith’s Dustmite article (Micscape 2/96) I recalled my own experience looking for these “wee beasties” as Leeuwenhoek might have described them. A client complained of allergies, stating that her doctor had hinted that dust mites might be a problem. She hired me to find them.
Here is a technique that worked well for me.
Vacuum cleaner, Petri dishes, dark blue or black closely woven cloth
Cut the cloth into circles just slightly larger than your Petri dishes. With the vacuum cleaner turned off, hold the cloth over the end of the hose. Then slip the vacuum’s crevice tool in place, securing the cloth in the vacuum’s air stream as a filter. Ideally, some of the cloth will protrude from around the crevice tool joint. Turn on the vacuum and sweep a MEASURED area of the suspect environment, say 10×10 cm. Agitate the carpet or bedding or whatever it is thoroughly so the dust mites will dislodge and be swept into the vacuum’s air stream. After thorough vacuuming, hold the vacuum hose upright and turn off the vacuum. Remove the crevice tool carefully, exposing the dirty cloth filter. Gently remove the filter and place in a Petri dish. Secure the Petri dishes with rubber bands and keep them upright during transport. Back at the microscopy bench, sift through each sample under the stereomicroscope and count the dust mites.
They are quite small! Strong oblique illumination seems to work best.
Calculate the population density in organisms per square meter. My samples ranged from 0 to a few hundred per square metre. I haven’t enough data to say what is “average”. I sampled under furniture and in walkways, all carpeted areas. I did not sample bedclothes or furniture.
I am interested in hearing of others’ adventures with dust mites!