OBJECTIVETo 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).

METHODSThis 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.

RESULTSHighest 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.

CONCLUSIONSUltraviolet 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.

Animals ; Dermatophagoides farinae ; radiation effects ; Dermatophagoides pteronyssinus ; radiation effects ; Female ; Male ; Ovum ; cytology ; pathology ; radiation effects ; Time Factors ; Ultraviolet Rays

Objective To identify different stages of Ixodes granulatus (I. granulatus) based on morphological characters prior to molecular identification which is significant for confirming and identifying the nymphal stages of I. granulatus. Methods A total of 14 individuals of adult, engorged and nymphal ticks collected from three different localities were examined morphologically using taxonomic keys, followed by PCR using cytochrome oxidase subunit I (COI). Clustering analysis based on COI sequences was carried out by constructing neighbor-joining and maximum parsimony tree to clarify the genetic variation and diversity of local I. granulatus. Results Based on external morphological characterizations, nine individuals (64.3%) were successfully identified as I. granulatus, while five individuals were recognized only as Ixodes sp. due to lack of morphological characters visible and development during that stage. Molecular analysis of local I. granulatus using COI gene revealed 93%–94% sequence homology from available sequence in GenBank and was in concordance with the morphological identification. Furthermore, a low intraspecific variation was observed among the species of I. granulatus collected from different localities (0%–3.7%). Conclusions These findings demonstrated for the first time the establishment of COI gene for identifying I. granulatus nymphal tick which is of paramount importance to the control of potential tick-borne infections in Malaysia. Moreover, this study provides evidence that a combination of morphology and molecular data was corroborated as an accurate tool for tick identification.