Lymphatic and tissue filariasis

Abstract

The range and burden of neglected tropical diseases, many of which are helminth-derived, remains enormous. Infections are rampant in poor districts and although efforts have been implemented over the years, there remains insufficient networks for disease control. In India, experts are encouraging the government to develop a functional public health infrastructure to manage diseases. India has 553 million people at risk for lymphatic filariasis (LF), one of the chronic filarial nematode infections that causes severe morbidity in humans. During coevolution, filariae have developed tactics to modulate the host's immune system so that they can persist for many years. Therefore, most individuals remain asymptomatic and mansonellosis and loiasis are primarily thought of as nuisance infections. Nevertheless, pathology can develop into elephantiasis during LF and Onchocerca volvulus infections can lead to vision loss or skin pathology. Many filarial species require the endosymbiotic Wolbachia bacteria for development and maturation. Indeed, targeting Wolbachia via antibiotic therapy has provided an alternative therapeutic approach which, in contrast to drugs currently employed in mass drug administration programs, is highly macrofilaricidal. This chapter provides an overview about filarial agents drawing upon both their similarities and differences with regards to host immune reactions, ensuing pathologies and how infections alter response to vaccines and other diseases. All of these aspects have to be considered when implementing therapy, especially when adverse side effects may occur. These effects are synopsized in the final section alongside current success stories in terms of elimination and future strategies to control these public health problems.