Effects of high and low temperatures on development time and mortality of house dust mite eggs

Abstract

Hatching of Dermatophagoides pteronyssinus eggs was investigated when exposed to temperatures ranging from -70 to +70°C, at varying degrees of humidity (dry and wet heat, direct sunlight) and lengths of time (seven intervals, ranging from 0.5 to 5 h). Exposure to cold was induced using a domestic refrigerator at 4°C, its freezing compartment at -10°C and a deep freezer at -20, -40 and -70°C. For each time interval, there were three slides containing 30 eggs per slide, except for sunlight (five sets of slides). After treatment, all experimental groups were kept on an open work bench for 15 days of observation at ambient room temperature (ca. 22°C) and ca. 75% relative humidity. Control groups with 10 eggs per slide, in triplicate, followed a similar protocol. An egg was considered hatched if an emerging larva was detected from a cracked shell. Results indicated that at 40°C for both dry and wet heat, approximately 80% of all eggs survived. At direct sunlight and dry heat at 50°C, the thermal death point (TDP) occurred at 3 and 5 h, respectively. At 60 and 70°C both wet and dry heat, TDP occurred almost instantaneously. Under cold conditions, only the deep freezer at -70°C was effective in preventing hatching. It may be concluded that exposure to direct sunlight for 3 h, dry/wet heat of 60 and 70°C for a minimum of 30 min, and -70°C prevent egg hatching. This study may have relevance for mite control procedures.

A contemporary look at allergic conjunctivitis

“…There is controversy regarding the temperature at which the bedding should be washed for optimal removal of antigens, as mites are likely removed through a combination of drowning and scalding. Certain societies, for example the British Society of Allergy and Clinical Immunology (BSACI), recommend a minimal temperature of 60 °C as this temperature has been shown to kill mite eggs most efficiently [42,43]. Other bodies such as the American Academy of Allergy, Asthma and Immunology (AAAAI) do not recommend a specific cut-off because high temperature water poses a scalding hazard [41].…”

House Dust Mite Allergy Under Changing Environments

“…Since HDM species have different preferences for temperature,56 it could be anticipated that climate change can exert their selection in some places. Temperature is known to affect hatching of HDM eggs57 and HDM allergen production 58. It is possible that climate change might affect mite metabolism and that new allergens may become very relevant as sensitizing sources.…”

International consensus (ICON) on: clinical consequences of mite hypersensitivity, a global problem

“…Mites and their eggs survive poorly when exposed to hot water and clothes dryers but survive during short periods of freezing conditions. The exposure to direct sunlight is an often forgotten factor in the destruction of dust mites [222]. …”

“…There may be some mite death due to desiccation in the dry environment of a household freezer. But, dust mite eggs have been shown to resist freezing at temperatures above −70° Celsius [222]. And, freezing is not effective in removing dust mite allergen from reservoirs because dust mite allergen is stable at low temperatures for extended periods of time [239].…”