Assessment of susceptibility of the poultry red mite Dermanyssus gallinae (Acari: Dermanyssidae) to some acaricides using an adapted filter paper based bioassay.

A previously described bioassay was modified to assess the response of the poultry red mite, an important ectoparasite of fowl, to a selected group of acaricides. The adapted bioassay is simple to use, escape-proof and provides data that can be subjected to probit analysis. The reproducibility of the method was assessed by three tests with alpha-cypermethrin against a reference strain, which produced dose-response lines that did not differ significantly (chi(2)=1.39, 2 d.f., p=0.50), and had a derived common slope of 1.89. In addition, a limited evaluation study enabled assessment of response to commercial formulations of bifenthrin, bifenthrin+malathion and cypermethrin by field populations of the poultry red mite.

A simple pump-assisted method for collecting live, undamaged Psoroptes ovis from sheep using circulating saline.

The availability of large numbers of undamaged sheep scab mites, Psoroptes ovis, would be beneficial for discovery screening and development trials. There are several reported procedures for removing scab mites from sheep but they have limitations. To overcome this, a simple but versatile method employing the use of pumped saline was developed to remove all stages of the P. ovis mite from sheep. The method takes no more than 2 min to remove mites from the selected site with relative ease and is not affected by the condition of the fleece or lesion. The number of mites removed with the new method was 5-10 times more than detected by visual examination. These mites were undamaged and survived off-host for up to 16 days. The robust, portable equipment is easy to use under field conditions, making this method suitable for use as a diagnostic tool for early detection and monitoring of scab mites thus providing opportunities for development of novel alternative control strategies.

Determination of low levels of mite and insect contaminants in food and feedstuffs by a modified flotation method.

Extraneous material was separated from feed and food products by a modified technique in which kerosene is used in a specially designed flotation flask. This technique, although effective for analyzing feed and foods, presented limitations in the analysis of finely powdered materials. Some procedural modifications and an increased in the capacity of the flotation flask from 500 to 750 mL allowed a larger sample weight (20 g) to be analyzed for mites, insect fragments, and rodent hairs, with considerably reduced residue interference. In trials with a variety of products seeded with known numbers of mites, average recovery was 83%. Recoveries of 89% were obtained from flour samples seeded with insect fragments and rodent hairs. A new process of suspending extracted mites in a mixture of industrial methylated spirit (46%) and glycerol (54%) by volume was used to allow rapid and more precise estimates of mite populations in heavily infested samples.

Review of the carriage of zoonotic bacteria by arthropods, with special reference to Salmonella in mites, flies and litter beetles.

This systematic review considers the relationship between arthropods commonly found in and around livestock premises and zoonotic bacteria. The principal focus is upon insects and arachnids on poultry units, where houses, litter and manure provide good conditions for the growth, multiplication and protection of flies, beetles and mites, and where zoonotic pathogens such as Salmonella and Campylobacter are prevalent. Other members of the Enterobacteriaceae and the taxa Clostridium, Helicobacter, Erysipelas and Chlamydiaceae are also discussed. Salmonella is widely distributed in the flies of affected livestock units and is detectable to a lesser degree in beetles and mites. Persistent carriage appears to be common and there is some field and experimental evidence to support arthropod-mediated transmission between poultry flocks, particularly carry-over from one flock to the next. Campylobacter may readily be isolated from arthropods in contact with affected poultry flocks, although carriage is short-lived. There appears to be a role for flies, at least, in the breaching of biosecurity around Campylobacter-negative flocks. The carriage of other zoonotic bacteria by arthropods has been documented, but the duration and significance of such associations remain uncertain in the context of livestock production.

Rapid method for the detection of storage mites in cereals: feasibility of an ELISA based approach.

This paper describes the development of rapid immunodiagnostic tests for the detection of storage mite infestations in cereals and cereal products. The study's first phase (proof of concept) involved the production of a species-specific enzyme-linked immunoassay (ELISA) for the flour mite, Acarus siro (L.), a major pest of stored commodities. The specificity of this new assay was assessed against key stored product contaminants (13 species of mites of which three were predatory, five species of insects and five species of fungi) in the presence and absence of grain. The assay was species-specific (no cross-reactivity to other storage contaminants) and was unaffected by the presence of cereal antigens in the extract. In the study's second phase, species- and genera-specific ELISAs were developed for a range of key storage mite pests: the cosmopolitan food mite (Lepidoglyphus destructor), the grocers' itch mite (Glycyphagus domesticus), the grainstack mite (Tyrophagus longior), mites of the Tyrophagus and Glycyphagus generas, and all storage mites. All tests were demonstrably specific to target species or genera, with no cross-reactions observed to other storage pest contaminants or cereals. The final, validation phase, involved a comparative assessment of the species-specific A. siro and the genus-specific Tyrophagus ELISAs with the flotation technique using laboratory and field samples. Both ELISAs were quantitative (0-30 mites per 10 g wheat) and produced good comparative data with the flotation technique (A. siro r(2)=0.91, Tyrophagus spp. r(2)=0.99).

Maintaining Psoroptes ovis (Acari: Psoroptidae) off-host in the laboratory.

Feeding and maintaining sheep scab mites off-host is an important step towards achieving a safer, environmentally-friendly means of controlling sheep scab disease. The test arena developed by Thind and Muggleton (Exp Appl Acarol 22:543-552, 1998) has been adapted for feeding and maintaining Psoroptes ovis off-host. The test arenas are simple to construct and use, and escape-proof to all stages of mites. The performance of the test arenas was assessed by determining the survival of the scab mites at 33 and 36 degrees C and >95% r.h. on different diets. With this test arena the best reported mean survival of 10.3 days was achieved with both females and nymphs at a temperature of 33 degrees C on a diet of sheep serum; the mean maximum survival of females at these conditions was 18.8 days, which is at least a threefold improvement on previous reports. With further development it may be possible to adapt the test arena for assessing both slow and fast acting agents for controlling sheep scab.

Laboratory studies on the use of two new arenas to evaluate the impact of the predatory mites Blattisocius tarsalis and Cheyletus eruditus on residual populations of the stored product mite Acarus siro.

Residual populations of storage mites sheltering in crevices and cracks escape conventional control treatments and are implicated in the infestation of newly harvested grain. In a series of 24 h laboratory tests, the performance of solitary adults of two predatory mite species, Cheyletus eruditus (Schrank) and Blattisocius tarsalis (Berlese), were assessed for controlling small numbers of the flour mite Acarus siro (L.). Tests were carried out in the presence or absence of prey refuges or grain debris to afford shelter to the flour mites. While C. eruditus had a significant effect on the motile stages of A. siro, in contrast B. tarsalis had a significant effect on the eggs. The maximum percentage of motile stages of A. siro eaten by C. eruditus was 82%, whereas the minimum percentage of A. siro eggs eaten by B. tarsalis was 99%. While the performance of C. eruditus in predating on motile stages of the flour mite was hindered by the presence of the prey refuge (38% eaten) and grain debris (25% eaten), the performance of B. tarsalis in predating on flour mite eggs was unaffected (100% eaten in presence of prey refuge or grain debris). In prolonged exposures (36 days) the performance of 2, 4 or 8 adult predators, either a single species or a combination of both, was assessed for their ability to control a population of the flour mite developing up to F(2) from an initial inoculum of 80 females and 20 males, allowed to oviposit for 72 h in the absence of predatory mites. The maximum reduction in prey population of 80% was achieved with eight B. tarsalis. Combining the two predatory species did not enhance the reduction of A. siro population.

A new versatile and robust mite trap for detection and monitoring of storage mites in the cereal and allied industries.

Storage mites are important primary pests but present methods for trapping them are either rudimentary or have several limitations. These prevent effective early detection or reliable monitoring of mites in the food, animal feed and associated industries. The BT Trap is the first trap designed specifically for the detection and monitoring of mite infestation. This trap is made up of a mixed food base lure held in a robust adjustable housing. It is user friendly, requires an exposure period of only 4 days and can be used in a dusty environment. The performance of the BT Trap was evaluated in the laboratory and the mean minimal capture rate of mites was 62%. In a comparative field trial, this trap detected significantly more mites than the bait bag or the fishmeal trap. The trap's performance was also assessed in four different types of premises. These were premises engaged in the production of cereal based dry pet food, specialist animal feed, traditional cheese, and in the finished cereal section of a large transit storage warehouse. A total of 17 genera or species of storage and predatory mites was detected in these four premises, with at least seven species detected in each of these premises. This study confirms that the BT Trap was able to function under the rigours of use in the field. It has demonstrated its potential as a useful tool for early detection and monitoring of mites in production premises. It also provided information that was vital for improving existing mite control measures and in implementing effective management strategies.

Assessment of monitoring methods for early detection of three species of storage mite in bulk oilseed rape.

Two types of trap, the BT Trap and PC(TM) pitfall cone trap, were evaluated against the most widely used method of sampling and sieving for their ability to detect low numbers of storage mites (Acarus siro, Tyrophagus longior and Lepidoglyphus destructor) in bulk oilseed rape, under UK maritime conditions. In addition, a synthetic lure (2-nonanone) was incorporated into the two types of trap to assess whether its presence improved trapping performance. The BT traps and PC traps were significantly more effective in detecting low numbers of mites of all species compared with sampling and sieving. The PC trap with synthetic lure was the most effective method. As the PC trap is already widely used for monitoring insects in cereal bulks in the UK, extending its application to include oilseed rape, and to detect mites, would be a logical and cost effective extension of its use.

Modified flotation technique for quantitative determination of mite populations in feedstuffs.

Modifications are described to a previously published technique for quantitative determination of mite populations in animal feedingstuffs. In the modified method, the oil phase is kerosene instead of a mixture of kerosene and tetralin (1 + 1), and aqueous industrial methylated spirit is substituted for aqueous ethanol in the aqueous phase. Emulsion formation at the interface is considerably reduced by incorporating a pre-extraction stage. Examination of mites on the filter paper is made easier and quicker by staining them with Phloxin B. Trials carried out with known numbers of mites in samples of dairy feed concentrates indicate mean recoveries of 84-96% throughout the range tested. The results show that the accuracy of the technique is not affected by the level of infestation.

A laboratory evaluation of a regulated airflow through wheat at four combinations of temperature and humidity on the productivity of three species of stored product mites.

Aeration is a promising alternative to the use of pesticides for the control of storage insects by cooling bulk grain, but its effectiveness against mite pests is neither fully understood nor optimised. For this reason, the productivity of three species of storage mites, Acarus siro, Lepidoglyphus destructor and Tyrophagus longior, was studied in a laboratory-based experiment at four combinations of temperature and humidity (10 degrees C and 70% RH, 10 degrees C and 80% RH, 20 degrees C and 70% RH, 20 degrees C and 80% RH) with and without an airflow (at 10 m3/h/tonne, equalling 2.5 1/s/tonne, in tubes containing 15 g of grain). This is the first time that a study has examined the three principal components of aeration separately from each other. The effect of these factors was different for each species. For A. siro, temperature was the most important factor, while airflow and humidity were of similar but lesser importance. For T. longior, temperature was more important than humidity, while the reverse was true for L. destructor. For these two species, airflow was the least important factor. The airflow decreased the productivity of L. destructor and T. longior but increased the productivity of A. siro. This increase in productivity confirms that, in practice, prevention of mite infestations, in particular A. siro, will require storage of grain at low temperature, relative humidity and moisture content.

The occurrence of mites in cereal-based foods destined for human consumption and possible consequences of infestation.

Seven categories of cereal-based food products purchased at food retail outlets in UK were examined for the presence of mites by analysing 20 g samples using a flotation method. Mites were found in 21% of 571 samples, which were examined soon after purchase, and in 38% of 421 samples, derived from the 571 samples which were examined after 6 weeks of storage in volunteers' homes. Most of the samples where mites were detected had fewer than five mites. However, a few samples contained more than 20 mites with a maximum of 428 mites detected in a single sample. Sixteen families, genera or species of mites were recovered. The most common species were Acarus siro. Tyrophagus putrescentiae, Lepidoglyphus destructor and Glycyphagus domesticus. The level of contamination was broadly similar for each of the seven categories of products examined. It is likely that infestation occurs at every stage of food processing and storage. This is the first study of its kind and there is no reason to believe that results from similar studies carried out in other temperate countries would be markedly different. Increase in the percentage of contaminated samples following storage in a domestic situation suggests that the domestic environment is an important factor in developing infestation. The implications of mite contamination on food quality and on human health are briefly discussed.

Flotation technique for quantitative determination of mite populations in powdered and compacted foodstuffs.

Samples are preheated in 25% aqueous ethanol at 65 degrees C for 5 min. A specially designed flotation flask and solvent mixture of kerosene-tetralin (1+1) is used to form an interface with 25% aqueous ethanol. Mites, insects, and insect fragments are separated from vegetative material by an overflow method. Trials incorporating a known number of mites in samples of pigmeal indicate that at an infestation level of 1000 mites/kg the method always recovered 70% of the population and at 2000 mites/kg, 75%. The method permits collection of mite specimens for microscopic examination as well as allowing differentiation between live and long-dead insects. It does not use highly volatile solvents or corrosive acids. The apparatus has been successfully tested for quantitatively determining mite populations in flour, dried skimmed milk, animal feedstuffs, soya meal, wheat, rape seed, dates, and house dust. It has also been used to estimate insect contamination in packaged dates.

Pirimiphos-methyl resistance in two stored product mites, Acarus siro and Acarus farris, as detected by impregnated paper bioassay and esterase activity assays.

The response to pirimiphos-methyl, in one strain of Acarus farris and two strains of Acarus siro, was assessed using an impregnated filter paper bioassay and by the selection of adults following exposure to pirimiphos-methyl. It was concluded that one of the strains of A. siro was resistant to pirimiphos-methyl and that a major resistance mechanism was involved. The second strain of A. siro gave a response similar to that of a laboratory strain unexposed to organophosphates and was considered to be susceptible. The A. farris strain responded to selection at the ED50 but not at the ED99, and it was concluded that a minor resistance mechanism is present in this strain. Assays of esterase activity were used to attempt to identify the biochemical mechanisms involved in the resistance detected by the bioassays. The A. farris and susceptible A. siro strains showed similar levels of esterase activity but the esterase activity of the resistant A. siro strain was significantly greater. An increase in esterase activity followed selection of both the A. farris strain and the resistant A. siro strain. An acetylcholinesterase assay showed no significant difference between the susceptible and pirimiphos-methyl selected strains of A. siro. The results suggest that esterases are involved in the resistance to pirimiphos-methyl found in A. siro and A. farris but that in A. siro, at least, other mechanisms may also be present.