A Dust-Mite Presentation

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A Dust-Mite Presentation
By Francis Howard
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Background Information

• Mite allergen released as faeces (poo).
• 20-30 faecal pellets/day
• 2-3,000/lifetime

• Mite allergen triggers
• Asthma
• Eczema
• Perennial Rhinitis
• 85 asthmatics allergic to HDM in UK.

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Worldwide prevalence symptoms of Asthma, 13-14yrs
ISAAC (1998)

• UK 15-35
• Australia New Zealand20-30
• Peru 25
• Brazil 15-25
• South Africa 15
• Thailand 15
• India 5-20
• The International Study of Asthma and Allergies
  in Childhood

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Current Control Methods

• Must also kill mites in carpets and soft
  furnishings.
• Current acaricides can trigger asthma attacks.
• Need to test new chemicals in the lab.

• Best method to control mites in beds are special
  bedcovers.
• These do not kill mites.

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Objectives

• To understand how to design a bioassay to test
  potential acaricides against dust mites.
• To test a new compound called ?-cymene, from
  plant oils, against house dust mites.
• To see how effectively the new compound works
  compared with a known acaricide (d-phenothrin)
  and a control (70 ethanol).

Chamber bioassay
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Methods Treating Carpet
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• Cut carpet discs to fit chambers.
• Acaricide solutions were made to the correct
  concentration.
• Acaricide was sprayed onto discs at a rate of
  10ml/m2
• Discs allowed to dry overnight.

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Methods Seeding Chambers

1. Vaseline was smeared around floor of chamber
   (hole for humidity).
2. Filter paper was placed on vaseline (to prevent
   mite escapes).
3. Treated carpet placed on top of filter paper.
4. 100 mg of mite culture was weighed.
5. Dust mites placed on top of carpet and lid sealed
   down with vaseline.

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Methods
Mite

1. After 24 hours, observed 20 different fields of
   the chamber through a binocular microscope at
   x40.
2. Used an acetate grid to ensure that each field
   observed was different.
3. Counted the number of live mites in each field.

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Results 24hr

• Field Ethanol 1 Ethanol 2 d-Phen 1 d-Phen 2
  Cymene 1 Cymene 2
• 1 1 1 0
  0 0 0
• 2 11 0 0
  0 0 0
• 3 5 2 0
  0 0 0
• 4 2 1 0
  0 0 0
• 5 0 0 0
  0 0 0
• 6 21 42 0
  0 0 0
• 7 36 27 0
  0 0 0
• 8 3 9 0
  0 0 0
• 9 2 2 0
  0 1 0
• 10 14 129 0
  0 0 0
• 11 40 58 0
  0 0 0
• 12 4 25 0
  0 1 0
• 13 5 18 0
  0 0 0
• 14 152 66 0
  0 1 0
• 15 15 15 0
  0 0 0
• 16 18 24 0
  0 0 0
• 17 3 5 0
  0 0 0

Total 338 444 0 0 3 0
7 day observations were also made similar
results.
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Conclusion

• The ?-cymene worked against the dust mites and
  killed them equally effectively as d-phenothrin
  in less than 24 hours.
• More replicates required to confirm my
  observations.

I helped MSc students to perform the same tests
(4 replicates/treatment) this week.
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Further Studies

1. Test duration of activity.
2. Whether chemical aggravates asthma attack/skin
   sensitisation.
3. Whether chemical discolours fabrics.

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Overall

• I have enjoyed it very much
• I have had fun
• And most importantly I am very proud of myself,
  as are my family

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People who have helped me achieve this work
experience.

• Mary Cameron
• Carolyn Stephens
• Chris Grundy
• Natalie Armstrong
• Nigel Hill
• Eric Stein
• My Nan for the gene of fast typing
• Ruth Willis (especially for the tea)
• And all of my friends, for their wonderful
  support

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Any Questions?