Can he order from Germany?
I use a Neem oil repellent.
Years ago I ordered this due to a massive invasion of red mites and prepared a 10 % solution to bath the chicken in this. Furthermore I cleaned the coop (dry & wet with high pressure cleaner) and sprayed all surfaces with a 2 % solution of Temazad.
http://www.temmen.de/produkte/temazad.htm
Afterwards I had never more problems since then.
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