Dear Dusko Trajkovic: Please tell your European friend the following: Avian
spirochaetosis is caused by a bacterium= Borrelia anserina. It causes great
economic losses due to high mortality and variable morbidity. B. anserina is
exclusively infectious to birds, but a relative to it, B. burgdorferi causes
Lyme's disease in humans and some papers have implicated birds in the spread
of this infection. These bacteria- Spirochaetae- are directly transmitted to
healthy birds by diseased ones, or indirectly through the bites of
blood-sucking insects or contaminated stuffs. You can diagnose this disease
by detecting the bacteria in Giemsa-stained blood smears or tissues
impronta, or else by immunofluorescence or dark-field microscopy.

I hope this information has been useful to you

Agustin Venzano
Vet Histopathologist and Immunopathologist
INTA Castelar, Argentina