Endosymbiotic bacteria living in plasmodia or worm parasites are required f
or the homoeostasis of their host and should be excellent targets for chemo
therapy of certain parasitic diseases. We show that targeting of Wolbachia
spp bacteria in Onchocerca volvulus filariae by doxycycline leads to steril
ity of adult worms to an extent not seen with drugs used against onchocerci
asis, a reading cause of blindness in African countries.