Effects of relative humidity on development, fecundity and survival of three storage mites

Influence of storage conditions on the infestation of Tyrophagus putrescentiae and prevalence of mite hypersensitivity in Taiwan

Sensitization to mites is a considerable factor in the development of allergic diseases. Because of its abundance, Tyrophagus putrescentiae (Tp) is the predominant storage mite found in home storage rooms, kitchens, and bakeries. Patients allergic to mites might exhibit a severely hypersensitive reaction upon ingesting Tp-contaminated food. The objective of this study was to investigate the rates of Tp contamination in commercial storage products from various areas, storage conditions, and environments in Taiwan. A specific antibody against Tyr p 3, the allergen on Tp, could be used as an indicator to monitor the contamination condition in storage foods. The microscopic mite examination, allergen detection by ELISA and cultured mite chemotaxis were used to evaluate the prevalence of T. putrescentiae contamination. Moreover, the IgE responses of patients allergic to mites were examined. We found that pet food and mushrooms were commonly contaminated with Tp, and this was validated through Tyr p 3 concentration and chemotaxis experiments. Tp contamination rates decreased significantly when samples were sealed and stored at a low temperature (<  4 °C), low relative humidity (RH < 60%), or for longer periods at a low temperature. The results of the clinical study indicated that the mites that elicited major positive IgE responses in allergic subjects were Dermatophagoides pteronyssinus and D. farinae. Thus, people who are sensitized to D. pteronyssinus or D. farinae might be at risk of a second anaphylactic reaction due to cross-reactivity upon ingestion of Tp-contaminated food. Accordingly, Tp contamination can be prevented by keeping food packages sealed and stored at a low temperature. This prevents the severe allergic reaction caused by the inadvertent ingestion of contaminated food-borne Tp.

Risk of exposure of a selected rural population in South Poland to allergenic mites. Part II: acarofauna of farm buildings

Exposure to mite allergens, especially from storage and dust mites, has been recognized as a risk factor for sensitization and allergy symptoms that could develop into asthma. The aim of this study was to investigate the occurrence of mites in debris and litter from selected farm buildings of the Małopolskie province, South Poland, with particular reference to allergenic and/or parasitic species as a potential risk factor of diseases among farmers. Sixty samples of various materials (organic dust, litter, debris and residues) from farm buildings (cowsheds, barns, chaff-cutter buildings, pigsties and poultry houses) were subjected to acarological examination. The samples were collected in Lachowice and Kurów (Suski district, Małopolskie). A total of 16,719 mites were isolated including specimens from the cohort Astigmatina (27 species) which comprised species considered as allergenic (e.g., Acarus siro complex, Tyrophagus putrescentiae, Lepidoglyphus destructor, Glycyphagus domesticus, Chortoglyphus arcuatus and Gymnoglyphus longior). Species of the families Acaridae (A. siro, A. farris and A. immobilis), Glycyphagidae (G. domesticus, L. destructor and L. michaeli) and Chortoglyphidae (C. arcuatus) have been found as numerically dominant among astigmatid mites. The majority of mites were found in cowsheds (approx. 32%) and in pigsties (25.9%). The remaining mites were found in barns (19.6%), chaff-cutter buildings (13.9%) and poultry houses (8.8%). The results suggest that the allergenic mites may constitute an occupational hazard for agricultural workers in all farming environments examined.

Mite Control and Sensory Evaluations of Dry-Cured Hams with Food-Grade Coatings

The ham mite, Tyrophagus putrescentiae (Schrank; Sarcoptiformes: Acaridae), is the predominant pest of dry-cured pork during aging. This research was conducted 1) to determine the minimal concentrations of propylene glycol necessary for food grade coatings to control mites; and 2) to determine if sensory differences could be detected in hams that were treated with food grade coatings in commercial facilities using difference from control sensory tests. Ham cubes coated with either xanthan gum + 15% propylene glycol or propylene glycol alginate + carrageenan + 7.5% propylene glycol were the lowest propylene glycol concentrations that were effective (P < 0.05) at controlling mite infestations under laboratory conditions. Whole hams from commercial plants that were dipped with coatings were slightly different (P < 0.05) from the non-dipped control hams with respect to flavor, texture and moistness in the first trial. However, hams sprayed with coatings, a lower-cost application than dipping, did not cause sensory differences (P > 0.05) when compared to the control with respect to flavor, texture, moistness, and weight loss in trial 2. This research indicated that dry-cured ham processors could potentially spray these coatings on dry-cured hams during aging to control mite infestations in their plants without negatively impacting the sensory quality of the hams.

Monitoring Tyrophagus putrescentiae (Acari: Acaridae) With Traps in Dry-Cured Ham Aging Rooms

Methyl bromide is the most effective fumigant for controlling the mold (or ham) mite, Tyrophagus putrescentiae (Schrank) (Acari: Acaridae), the most significant pest of dry-cured ham. However, methyl bromide is being phased out of use. Therefore, integrated pest management (IPM) methods should be developed to help control mites in dry-cured ham plants. The foundation of a successful IPM program is an effective monitoring program that provides information on pest presence and abundance over time. By using food-baited traps fabricated from disposable petri dishes and a dog food-based bait, mite activity over time and space was monitored in five dry-cured ham aging rooms from three commercial processing facilities that differed in their fumigation frequencies. Weekly sampling of the mite was conducted from June 2012 to September 2013. There were significant differences in the average weekly trap captures in all facilities, especially before and after fumigation, with the majority of mites in traps prior to fumigation. Mite numbers had a pattern of sharp decline after fumigation, followed by a steady increase until the next fumigation. Average trap captures varied due to trap location over the study period at all study sites, indicating that traps could be used to identify specific locations within an aging room where mite infestation of hams was more likely to occur. These findings can inform facility managers of mite population changes that can be used as one factor toward making pest management decisions and assessing the impact of fumigation or other pest mitigation actions.

Variability in Population Density of House Dust Mites of Bitlis and Muş, Turkey

This study was conducted to investigate the relationship between the number of house dust mites/g dust and different physical and environmental variables. A total of 1,040 house dust samples were collected from houses in Bitlis and Muş Provinces, Turkey, between May 2010 and February 2012. Overall, 751 (72.2%) of dust samples were mite positive. The number of mites/g dust varied between 20 and 1,840 in mite-positive houses. A significant correlation was detected between mean number of mites and altitude of houses, frequency of monthly vacuum cleaning, number of individuals in the household, and relative humidity. No association was found between the number of mites and temperature, type of heating, existence of allergic diseases, age and structure of houses. A maximum number of mites were detected in summer and a minimum number was detected in autumn.

Dry Dog Food Integrity and Mite Strain Influence the Density-Dependent Growth of the Stored-Product Mite Tyrophagus putrescentiae (Acari: Acaridida)

The infestation of foodstuffs by mites is connected to health risks and economic losses. The cosmopolitan stored-product mite Tyrophagus putrescentiae (Schrank, 1781) is an emerging and predominant pest of dry dog food. In this study, the influences on mite population growth of 1) the different dry dog food kernels present in the package; 2) the integrity of the dry dog food kernel, whether intact or crushed; 3) the initial population density of 10 or 100 specimens; and 4) the four mite strains used were investigated under laboratory conditions. The population growth tests were performed for 28 d at 85% relative humidity and 25°C. The intrinsic growth rates of the mites were compared. The population growth was higher on the brown and green kernels than on the red and white kernels. The kernel integrity affected the population growth, and the integrity effect was highly influenced by the initial mite population density. The mites showed density-dependent growth in three of the four mite strains tested. The initial population density changed the population growth ranking among the mite strains, thereby indicating strain-specific density-dependent growth. The results of this study have important implications for predictive models of stored-product mite populations in dry dog food. One practical recommendation is that the growth of mites should be considered with regard to the mite strains and according to the strain-specific density dependent growth. Next, the integrity of the kernels should be maintained because disrupted or crushed kernels promote increases in mite populations.

Mite species inhabiting commercial bumblebee (Bombus terrestris) nests in Polish greenhouses

Nests of social insects are usually inhabited by various mite species that feed on pollen, other micro-arthropods or are parasitic. Well-known negative effects of worldwide economic importance are caused by mites parasitizing honeybee colonies. Lately, attention has focused on the endoparasitic mite Locustacarus buchneri that has been found in commercial bumblebees. However, little is known of other mites associated with commercial bumblebee nests. Transportation of commercial bumblebee colonies with unwanted residents may introduce foreign mite species to new localities. In this study, we assessed the prevalence and species composition of mites associated with commercial bumblebee nests and determined if the mites are foreign species for Poland and for Europe. The study was conducted on 37 commercial bumblebee nests from two companies (Dutch and Israeli), originating from two greenhouses in southern Poland, and on 20 commercial bumblebee colonies obtained directly from suppliers. The species composition and abundance of mites inhabiting commercial bumblebee nests were determined. Seven mite species from three families were found in nests after greenhouse exploitation. The predominant mite species was Tyrophagus putrescentiae (Acaridae) that was a 100-fold more numerous than representatives of the family Laelapidae (Hypoaspis marginepilosa, H. hyatti, H. bombicolens). Representatives of Parasitidae (Parasitellus fucorum, P. crinitus, P. ignotus) were least numerous. All identified mite species are common throughout Europe, foreign species were not found. Mites were not detected in nests obtained directly from suppliers. We conclude that probably bumblebee nests are invaded by local mite species during greenhouse exploitation.

Use of vapor pressure deficit to predict humidity and temperature effects on the mortality of mold mites, Tyrophagus putrescentiae

The mold mite, Tyrophagus putrescentiae (Shrank), frequently infests a variety of stored food products in ideal, but rather limited conditions. Major factors limiting survival of this mite are the temperature and humidity imposed on T. putrescentiae as it develops within and disperses among sites. However, since relative humidity is dependent upon air temperature, determining survivability in a habitat can be difficult in the presence of structural temperature variations. Vapor pressure deficit (VPD) provides a method of combining both relative humidity and temperature into a single number that can be used to determine conditions detrimental to mite survival. This study utilized a bioassay format to measure mortality of T. putrescentiae when exposed to a range of seven temperatures (5-35 degrees C), 10 relative humidities (0-100% RH), 17 exposure times (0.5-240 h), with and without food. With these combinations of temperature and RH, mortality curves (mortality versus time) that displayed a sigmoidal relationship were used to calculate LT(50) and LT(90) estimates. These mortality estimates were then regressed on their associated VPD and the resulting regressions (LT(50) and LT(90)) were significant at P < 0.0001, and provided acceptable R(2) values >or=0.83, regardless of whether food was present or not. At room temperature, threshold of VPD for T. putrescentiae development was below 8.2 mbar, this estimate being initially calculated from published values. For mites exposed to drier conditions, above 8.2 mbar, survival time was curtailed dependant on the magnitude of VPD. As the VPD exceeded 12 mbar, mites experienced substantial (>90%) mortality within 58 (33, 101) h; and further increasing VPD decreased the time of exposure to achieve mortality. This study demonstrates that making subtle changes in humidity or temperature to reach a target VPD may provide control of mite outbreaks and reduce areas inhabitable for T. putrescentiae.

Reproduction, longevity and life table parameters of Tyrophagus neiswanderi (Acari: Acaridae) at constant temperatures

The astigmatid mite Tyrophagus neiswanderi Johnston and Bruce is mainly considered a pest of ornamental and horticultural crops. However, this mite has been found infesting Cabrales cheese in Spain, though its population density is low compared to Acarus farris, the prevalent species of astigmatid mite encountered in Cabrales cheese maturing caves. One of the factors that might be influencing this differential abundance is temperature. In the present study the effect of temperature on reproductive parameters and longevity of T. neiswanderi was examined at six constant temperatures, ranging from 10 to 31 degrees C, and a relative humidity of 90 +/- 5%. Preoviposition period, fecundity and daily fecundity were adversely affected by extreme temperatures while the oviposition period increased as temperature was reduced. Male and female longevity increased as temperature decreased, but males showed significantly greater longevity than females. Additionally, this difference was greater as temperature decreased. The effect of temperature on the intrinsic rate of natural increase of T. neiswanderi populations was described by the non-linear Lactin model. The optimum temperature for development was predicted at 26.6 degrees C. At this temperature, the population doubling time is 2.8 days. The lower and upper thresholds for T. neiswanderi populations were calculated at 7.4 and 31.7 degrees C, respectively. According to these results, the influence of temperature on the low population density of this mite found in Cabrales maturing caves compared with A. farris is discussed.

Evaluation of low humidity treatments to control Acarus farris (Acari: Acaridae) in Cabrales cheese

Laboratory experiments were conducted to establish the best combination of relative humidity (r.h.) and time of exposure to be applied on Cabrales cheeses infested with Acarus farris. Laboratory assays revealed that less than 30 h were required to obtain 90% mortality of mites at 50% and 60% r.h. Males were more susceptible than females to low relative humidity, since their lethal period values (LP) were lower than those obtained for females at the same relative humidity. Moreover, the response within sexes to low moisture treatments changed as exposure time increased, since the LP50 obtained for each sex at 50 and 60% r.h. were statistically different whereas the LP90 showed no significant differences within sexes. Accordingly, two modifications of the traditional maturing process were established to assess the efficacy of low moisture treatments to control A. farris on infested cheeses. The first modification consisted of one single exposure of 48 h at 50% r.h. and the second one consisted of two exposures of 48 h at 50% r.h. separated by a time interval of 15 days. No significant differences in final population density were observed for both low moisture treatments compared to control cheeses. Therefore, low humidity treatments are not effective to control A. farris in Cabrales cheese, despite the good results obtained in laboratory assays.