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 remain insufficient networks for disease control. It is estimated that more than 200 million people are infected with filarial nematodes. 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 lymphatic filariasis (LF) and Onchocerca volvulus infections can lead to vision loss or skin pathology. Due to this severe pathology, the WHO road map for neglected tropical diseases 2021–2030 declared to target the elimination of transmission for onchocerciasis and elimination as public health problem for LF in 80% of the endemic countries by 2030. Most 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, i.e., kills the adult filariae. This chapter provides an overview about filarial agents drawing upon both their similarities and differences with regard 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.