The symbiotic relationship between filarial parasitic nematodes and their Wolbachia endosymbionts - A resource for a new generation of control measures

Filarial parasites are responsible for millions of human infections each year, mostly in developing parts of the world. International programs supported largely by the World Health Organization have worked to control the impact of onchocerciasis and lymphatic filariasis using mass administration of single or combination drugs for long periods of time in eligible populations. The success of these programs is now being hampered by the probability of programmatic failure in the event of emerging drug resistance. Additional research is critically needed to develop a new generation of tools for the control and treatment of these infections. These would include drugs that target adult worms and vaccines, with the goal to overcome potential resistance to the currently available drugs and complement present control measures. The majority of human filarial parasites carry intracellular symbiotic bacteria, Wolbachia, that appear to be essential for development and reproduction of the parasite. The recent availability of genomic data for both filaria and Wolbachia provides insight into essential aspects of the symbiotic relationship between the endosymbiont and its nematode host. We present an overview of how this knowledge opens up avenues in the identification of new targets for the control of these parasitic infections.