Wolbachia
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Wolbachia is a type of inherited bacterium that infects arthropod species, including a high proportion of all insects. It is one of the world's most common parasitic microbes and the most common reproductive parasite in the biosphere.
[edit] Association with disease
Outside of Insecta, Wolbachia infects a variety of isopod species, spiders, mites, and many species of filarial nematodes (a type of parasitic worm), including those causing Onchocerciasis ("River Blindness") and Elephantiasis in humans as well as heart worms in dogs. Not only are these disease-causing filarial infected with Wolbachia, but Wolbachia seem to play an inordinate role in these diseases. A large part of the pathogenicity of filarial nematodes is due to host immune response toward their Wolbachia. Elimination of Wolbachia from filarial nematodes generally makes them either dead or sterile.<ref name="MedMicrobiolImmunol2003-Hoerauf">Hoerauf A, Mand S, Fischer K, Kruppa T, Marfo-Debrekyei Y, Debrah AY, Pfarr KM, Adjei O, Buttner DW (2003). "Doxycycline as a novel strategy against bancroftian filariasis-depletion of Wolbachia endosymbionts from Wuchereria bancrofti and stop of microfilaria production". Med Microbiol Immunol (Berl) 192 (4): 211-6. PMID 12684759.</ref> Consequently, current strategies for control of filarial nematode diseases include elimination of Wolbachia via the simple doxycycline antibiotic rather than far more toxic anti-nematode medications.<ref name="Lancet2005-Taylor">Taylor MJ, Makunde WH, McGarry HF, Turner JD, Mand S, Hoerauf A (2005). "Macrofilaricidal activity after doxycycline treatment of Wuchereria bancrofti: a double-blind, randomised placebo-controlled trial". Lancet 365 (9477): 2116-21. PMID 15964448.</ref><ref name="JYI2005-Outland">Outland, Katrina. "New Treatment for Elephantitis: Antibiotics", The Journal of Young Investigators, 2005 Volume 13.</ref>
Within arthropods, Wolbachia is notable for significantly altering the reproductive capabilities of its hosts. These bacteria can infect many different types of organs, but are most notable for the infections of the testes and ovaries of their hosts.
Wolbachia are known to cause four different phenotypes: male killing (death of infected males), feminization (infected males develop as females), parthenogenesis (reproduction of infected females without males) and cytoplasmic incompatibility (the inability of Wolbachia-infected males to successfully reproduce with uninfected females or females infected with another Wolbachia type).
Wolbachia are present in mature eggs, but not mature sperm. It is only infected females that pass the infection on to their offspring. It is thought that the phenotypes caused by Wolbachia, especially cytoplasmic incompatibility have been important in promoting speciation.
The bacteria was first identified in 1924 by Hertig and Wolbach in Culex pipiens, a species of mosquito. (Hertig and Wolbach, 1924).
More than 16% of insect species in Panama carry this bacteria.
The genomes of Wolbachia from Drosophila flies and Brugia nematodes have been sequenced, and genome sequencing projects for several other Wolbachia strains are in progress.
