Effects of tetracycline on the filarial worms Brugia pahangi and Dirofilaria immitis and their bacterial endosymbionts Wolbachia

Wolbachia endosymbiotic bacteria have been shown to be widespread among fil arial worms and could thus play some role in the biology of these nematodes . Indeed, tetracycline has been shown to inhibit both the development of ad ult worms from third-stage larvae and the development of the microfilaraemi a in jirds infected with Brugia pahangi. The possibility that these effects are related to the bacteriostatic activity of tetracycline on Wolbachia sy mbionts should be considered. Here we show that tetracycline treatment is v ery effective in blocking embryo development in two filarial nematodes, B. pahangi and Dirofilaria immitis. Embryo degeneration was documented by TEM, while the inhibition of the transovarial transmission of Wolbachia was doc umented by PCR. Phylogenetic analysis on the ssrDNA sequence of the Wolbach ia of B. pahangi confirms that the phylogeny of the bacterial endosymbionts is consistent with that of the host worms. The possibility that tetracycli ne inhibition of embryo development in B. pahangi and D. immitis is determi ned by cytoplasmic incompatibility is discussed. (C) 1999 Australian Societ y for Parasitology. Published by Elsevier Science Ltd. All rights reserved.