Storage mites in flour samples in Wellington, New Zealand.

Stored grains and seeds have been known to be prone to contamination by mites for well over 100 years [1], but it was not until 1993 that the fi rst documented case of anaphylaxis to mite-contaminated fl our was reported [2]. To our knowledge, no studies on mite contamination of fl our samples have been reported from New Zealand, although storage mites have been previously observed in a fl our sample [3] and Tyroglyphid mites have been found in stored products [4]. The objective of our pilot study was to determine the incidence of mite contamination of store-bought and domestic fl ourbased products. We purchased 23 fl our-based products from stores and supermarkets and obtained 54 samples of fl our-based products from domestic homes. We recorded brand, type of product, purchase date, time since the product had been opened, and method of storage. The fl our types are shown in the Table. Ethical approval was obtained from the Central Districts Ethical Committee. Each fl our sample was transferred to a large container and thoroughly mixed. Six subsamples were then taken by spatula from different areas of the sample and examined under a dissecting microscope. Live mites were removed with a fi ne probe and mounted on microscope slides in Brun’s medium. Mites were identifi ed with the aid of a compound microscope using the keys of Hughes [5] and Fan and Zhang [6]. None of the store or supermarket samples had evidence of live mites. Four of the 54 domestic samples contained live mites, corresponding to an incidence of 7.4%. All 4 contaminated flour samples had been stored in kitchen cupboards for longer than 1 month. The mite species identifi ed were • Thyreophagus and Tyrophagus species from a wholemeal fl our sample stored in a plastic container. We were unable to identify these at species level as no repeat sample could be obtained. aChapati, Bajri, Atta, Urid. Table. Types of Flour Samples Collected