Dust Mites, The Scourge of the Laboratory

[Bob <bobaxe@MCHSI.COM>]

   On Jim Anderson's website, he tc's hostas

Dust Mites, The Scourge of the Laboratory

     What are Dust Mites:

   Dust mites are microscopic Arachnids that eat the fungi that
normally is found on dead skin deposits in human habitations. Since the
human body sheds a continuous cloud of dead skin, the bugs have a ready
food supply. If you ever wondered what a bloodhound follows when
tracking you, it is this cloud of skin.  Dust mites also feed on other
materials in the home and are particularly attracted to sugar
molecules.   The feces of dust mites are a major source of allergens in
the home and can be the cause of asthma.  If your are allergic to house
dust, it is the mites.  Mites are common in carpets, furniture, and
bedding.  They are difficult to control in the home and are only
partially killed by laundering.  Dust mites do require moisture to
survive, and tend to be worse in humid climates.

     Why are Dust Mites a Problem in the TC Laboratory:

   Dust mites are attracted to the sucrose in TC media and because of
their association with fungi are the major source of fungal
contamination in the laboratory.  If you have several jars contaminated
with fungi, it is most probably caused by dust mites.  Do not think that
the caps will keep them out of the jars, they will not.  The mites
proliferate in a few days growing on the sucrose in the medium, crawl
out of the jars and into new ones.  You often can see the spots of fungi
where the mites have crawled. Another problem is that the mites can
infest the lids causing a fungal growth there.  When you subculture, the
fungal spores are sucked into the jar and you have contamination.
Without proper control, dust mites can contaminate the whole lab, and
you are out of business.  This is a major reason for failure of tissue
culture laboratories.

What are the Sources of Dust Mites in the Laboratory.

   You and your employees are the major source of dust mites in the
Lab.  They travel on your skin, in your clothing, and on your shoes.
Unless you bath and wear fresh clothing every time you enter the lab,
they will travel in with you.  They can also get into the lab through
openings to the outside such as cracks, doors, and windows.  Caulk and
seal thoroughly. Once in the lab they seem to survive there very nicely.

Controlling Dust Mites in the Laboratory:

   A.  What does not work:

       * Para film seals on the lids, they go right though the Para
film and most all tapes, rubber bands, etc.  3M medical tape will work
as will Saran wrap, but application is very time consuming.  Also when
your remove the tape you may cause contamination to get under the lid.
       * HEPE filters.  Air filtration is important to keep the
laboratory clean, so I recommend it.  However, air filtration will not
control dust mites as they are too heavy to get air born and into the
filters.
       * Insecticide impregnated paper on your shelves.
       * Orthene, Diazinon sprays or most insect bombs
       * Wishful thinking.

   B.  What does work:

       * Cleanliness.  No shoes in the lab.  Freshly laundered lab
coats on employees.  No jackets, sweaters or other clothing that is not
frequently laundered.  No rugs on the floor to catch the mites.
Frequent cleaning of all surfaces to remove the mites and dead skin.
       * Isolation.  Put all cultures into heat sealed plastic bags.
If you do not have a clean room, this works.  It is however, labor
intensive.
       * Pyrethrum sprays.  These are effective if the spray leaves an
oily deposit on everything.  Spray at least once a month.  You can use
spray cans such as Raid (natural pyrethrums) or a hand held paint
sprayer (Wagner) to get a fine mist.  Use a respirator during application.
       * Launder all clothing with several drops of Eucalyptus oil.
Also add this oil to your spray mixture.  The lab will stink, but it
does help.
       * Promptly remove all contaminated jars so the new infestations
do not occur.
       * Get professional help from a major pesticide applicator.  They
have very toxic chemicals that are very effective in killing the mites
and they also have growth hormones that help.  This is expensive, but
the pros do know how to get rid of the mites.  The toxic nature of the
chemicals they use just about requires professional application.
       * Good Luck!

Bob Axmear - 208 2nd St Ne - Waukon, Ia 52172
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