Prevalence of the poultry red mite (Dermanyssus gallinae) in England.

THE poultry red mite Dermanyssus gallinae feeds on resting birds, mainly during the night, and can cause anaemia, decreased egg production and, in extreme cases, death (Kirkwood 1967, 1968, Hoglund and others 1995). It has been implicated as a possible vector of various poultry diseases, such as Salmonella species and eastern equine encephalomyelitis virus (Nordenfors and others 1999). D gallinae poses a potential risk to workers within the poultry house because it will bite human beings (Chauve 1998). Red mites spend most of their life cycle away from the host, hiding in cracks and crevices within the poultry house. Populations of red mites can build up rapidly because their life cycle can be completed in less than a week. Female mites are ready to oviposit within 24 hours of their first blood meal, and all stages are haematophagous (Kettle 1995), making the mite an important pathogen of chickens. Control methods generally involve treating the premises rather than individual birds, and include the use of acaricides (organophosphates, synthetic pyrethroids and carbamates), management procedures and absorptive dessicant dust such as silica (Kirkwood 1967, Zemen and Zelezny 1985, Abo-Taka 1990, Fletcher and Axtell 1991, Nordenfors 2000). Chemical failure attributed to resistance in mites has been reported to dichlorodiphenyltrichloroethane (DDT), organophosphates and pyrethroids (Zemen and Zelezny 1985, Beugnet and others 1997, Chauve 1998). The control methods currently used rely on combination products containing both permethrin and pyriproxyphen. This short communication describes a study to obtain information on the prevalence and perceived importance of red mites, the control measures being used and the effectiveness of such measures. Questionnaires were distributed to poultry producers in England via seven veterinary surgeries, and further questionnaires were published in the December 2002 issue of Poultry World magazine and the December 6, 2002 issue of UKEPRA News. Poultry producers and keepers were asked about the stocking density of their birds, the type of housing used and the cleaning procedures used after the last flock depletion. Further questions related to the importance, control and current status of red mites within their poultry units. All participants were asked whether they would be prepared to send in samples of litter containing red mites for in vitro testing (Coles and Stafford 1999), and those who responded positively were provided with sample bags and prepaid envelopes. Upon receipt, samples were examined under a compound microscope to confirm the identity of the mites (Soulsby 1982). Samples of mites provided by the poultry units and fully susceptible, laboratory-reared mites from Hannover, Germany, were exposed for two hours to acaricide-impregnated Whatman filter papers sealed in 3·5 x 5·5 cm ‘tea bags’ (J. R. Compton), using a similar testing procedure to that described by Coles and Stafford (1999) for Psoroptes ovis. A total of 43 questionnaires was returned, of which 58 per cent were for layers (representing a total of 570,600 birds), 30 per cent were for parent birds (which covered a total of 980,300 birds) and 12 per cent were for fancy fowl (2000 Veterinary Record (2005) 157, 233-235