Treating the infection: Remarkable advances in treating lymphatic filariasis have recently been achieved, but most of these have focussed not on the individual but on the community with infection. Thus, the goal has been to reduce microfilaraemia in a community to levels below which successful transmission of infection will not occur. The once-yearly administration of single doses of either 1 or 2 drugs (selecting among ivermectin, DEC and albendazole) to effect this microfilarial reduction has been reviewed above (see 'Prevention'). Few clinical trials, however, have focussed on optimizing treatment of the individual patient, so there is little new data arguing for or against a change from the earlier recommended treatment regimens of DEC (6 mg/kg per day) for 12 days in bancroftian filariasis and for 6 days in brugian filariasis. It is well known that these regimens are not completely effective in eliminating infection, but no intensive studies to determine optimal regimens using the newly available circulating filarial antigen assay or ultrasonographic localization of adult parasites have yet been carried out. Thus, these earlier regimens repeated at 1-6 monthly intervals if necessary, or even the administration of DEC (6-8 mg/kg per day) for 2 days each month for a year are appropriate regimens for treating lymphatic filariasis. Ivermectin, though very effective in decreasing microfilaraemia appears not to kill adult worms (i.e., be macrofilaricidal) and thus can be expected not to cure infection completely. Albendazole can be macrofilaricidal for W. bancrofti if given daily for 2-3 weeks, but optimization of its usage has not been attempted. Thus, for treating infection in individual patients single or repeated courses of DEC are still recommended. However, since the use of DEC in patients with either onchocerciasis or loiasis can be unsafe, it is important that patients with bancroftian filariasis who live in areas endemic for these other infections be examined for co-infection with these parasites before being treated with DEC.

In treating microfilaraemic patients with either DEC or ivermectin appreciable side-reactions can occur, but their frequency and intensity are directly proportional to the pre-treatment microfilaraemia levels of these patients. While both drugs, at the dosages given, have essentially no side-effects themselves, their rapid killing of the microfilarial parasites releases enough antigen into the system to overwhelm the modulating effects of the host's immune system and to induce a variety of side reactions. These include headaches, fever, myalgia, lymphadenopathy and occasionally rash, itching and other symptoms. Though the most severely affected can also experience postural hypotension, generally these reactions are well managed through the use of anti-pyretics, antihistamines, or, in the most severe instances, steroids. In amicrofilaraemic individuals such side-reactions do not occur. Even in the tropical eosinophilia syndrome where the host is already allergically-responsive to the parasite, since there are no microfilariae in the blood of these individuals, there is no exacerbation of symptoms, but rather a steady improvement over the 2-4 weeks during which DEC is administered.