title: Effect of germicidal UV-C light(254 nm) on eggs and adult of house dustmites, Dermatophagoides pteronyssinus and Dermatophagoides farinae (Astigmata: Pyroglyhidae).
abstract: OBJECTIVE
  To examined the immediate and 24 hours post- irradiation germicidal effects of UV-C lamp on eggs and adults of house dust mites Dermatophagoides pteronyssinus (D. pteronyssinus) and Dermatophagoides farinae (D. farinae).
  
  
  METHODS
  This study investigated the immediate and 24 hours post irradiation mortalities of adult mites exposed to UV-C at different exposure times (5 mins, 10 mins, 15 mins, 20 mins, 30 mins and 60 mins) and distances (10 cm, 25 cm, 35 cm, 45 cm and 55 cm). Fresh eggs of the 2 dust mites were also irradiated at 10, 35 and 55 cm for 0.5, 1, 2, 3, and 5 minutes, and observed daily post- irradiation for up to 7 days.
  
  
  RESULTS
  Highest immediate mortality of 100% occurred with direct irradiation at 10 cm distance from UV-C lamp and for 60 mins, for both species of mites. The post 24 hours mean mortality rates were (58.4±17.4)% for D. pteronyssinus and (27.7±9.7)% for D. farinae when irradiated for 1 hour at 55 cm distance under UV-C lamp. When mites were irradiated in the presence of culture media, the highest mortality rates were lower compared to the direct irradiation; at 10 cm distance and 60 mins exposure, the mean mortality was (74.0±6.8)% for D. pteronyssinus and (70.3±6.7)% for D. farinae. Egg hatchability for both species of mites was also notably reduced by greater than 50% following irradiation.
  
  
  CONCLUSIONS
  Ultraviolet C irradiation is lethal to an array of organisms by damaging their nucleic acids (DNA and RNA). This study demonstrates the increasing mite mortalities with increasing exposure times and decreasing distances.
authors.affiliation: Acarology Unit, Infectious Disease Research Centre, Institute for Medical Research, Jalan Pahang, 50588 Kuala Lumpur, Malaysia.
authors.forename: Ernieenor Faraliana Che
authors.initials: EF
authors.lastname: Lah
authors.forename: Raja Noor Azreen Raja
authors.initials: RN
authors.lastname: Musa
authors.forename: Ho Tze
authors.initials: HT
authors.lastname: Ming
mesh_terms: D000818:Animals; D040001:Dermatophagoides farinae / Q000528:radiation effects*; D040002:Dermatophagoides pteronyssinus / Q000528:radiation effects*; D005260:Female; D008297:Male; D010063:Ovum / Q000166:cytology / Q000473:pathology / Q000528:radiation effects*; D013997:Time Factors; D014466:Ultraviolet Rays
keywords: Dermatophagoides farina; Dermatophagoides pteronyssinus; Mortality; Physical control; UV-irradiation