and dec, as well as other benzimidazoles such as mebendazole, albendazole, levamisole, and thiabendazole, have been conducted. recently, clinical trials assessing the effectiveness of doxycycline to treat m. perstans infection have also been documented. generally, dec is ineffective in the treatment of m. perstans infection. other drugs such as ivermectin and praziquantel have been tried, but are neither reliable nor rapidly effective. mebendazole and thiabendazole have a greater effect than previously described drugs, but are not sufficient for treatment alone. combination treatments with dec and mebendazole have had the most success. in the most recent clinical trials, doxycycline has had success comparable to, if not better than, that of combination treatments. however, because it is a relatively recent discovery, the use of doxycycline is relatively limited to clinical trials. if the patient is asymptomatic, no treatment is necessary. an analysis of the results of various clinical trials for each drug is illustrated below: diethylcarbamazine while diethylcarbamazine (dec) is the most common drug used to treat m. perstans infection, it is often ineffective, especially with the administration of only a single dose. in a 2005 study of 160 patients with symptomatic m. perstans infection in south chad, dec was administered in 200 mg. doses, twice daily for 21 days with a gradual dosage increase in the first three days. the single course of dec lowered microfilarae in 80% of subjects, but did not eliminate the infection or related symptoms. a second course was therefore administered, and was successful in eliminating the microfilarial burden in most cases. no persistent effect of dec on microfilaria was noted on long-term follow up. these results accurately represent the general efficacy of dec in treating m. perstans: two doses are necessary to eliminate the microfilarial burden temporarily, but no persistent effect of dec on microfilariae was shown long-term. furthermore, symptoms are usually not entirely alleviated by dec. it has not been reported to cause adverse side effects in patients with m. perstans infection. ivermectin while ivermectin is considered a first-line agent for the treatment of many filarial diseases (especially onchocerciasis), it has shown little or no efficacy against m. perstans at a dose of 200 μg/kg body weight or at a dose of 600 μg/kg body weight. a 2009 study in uganda evaluated the effects of ivermectin, albendazole, and a combined regimen of both drugs on m. perstans infected individuals: single doses of ivermectin alone had no marked effect on m. perstans microfilaraemias in the 12 months after treatments, with the counts remaining to pretreatment values. this is consistent with the findings of previous studies which have suggested ivermectin, when used alone, has little or no effect on m. perstans microfilaraemias. a reduction of microfilariae in patients has been noted, but it takes a long time to achieve (over 3 yr of administration of ivermectin), and is thus not useful in the short term for symptomatic patients. albendazole single doses of albendazole alone have been consistently reported to have little or no effect on m. perstans microfilaremias in 6 and 12 m after treatment, with counts of microfilaremias remaining close to pretreatment values. more recent studies have shown the drug to be more effective at high doses for prolonged periods of time. no side effects have been reported from recent studies. mebendazole mebendazole, another possible treatment for m. perstans filariasis, has been shown to be effective in significantly reducing microfilariae levels. it has been more effective than both ivermectin and dec—with a greater number of responders, a more significant reduction in microfilariae levels, and the ability to eliminate the infection more efficiently. thiabendazole thiabendazole has been shown to result in a small but significant decrease in microfilariae and in eosinophil count, and symptoms as treatment for symptomatic m. perstans infection. these markers were reduced even further following the administration of the second dose, showing that thiabendazole may be effective in m. perstans infection. in a recent comparative study, thiabendazole at a higher activity than single drug treatments such as ivermectin, dec, and mebendazole, but lower activity than the combined regimen of mebendazole and dec. however, more research may be needed into confirm the correct dosage and true effectiveness of thiabendazole in combating m. perstans infection. praziquantel praziquantel is effective against various helminthic and protozoan infections. the few studies about the use of praziquantel against m. perstans infection do not support its use for treatment of mansonelliasis. doxycycline doxycycline has been shown to decrease the development, embryogenesis, and fertility of worms in species that harbor the intracellular endosymbiont wolbachia. wolbachiae are bacterial endosymbionts of insects and many filarial nematodes, such as onchocerca volvulus, wuchereria bancrofti, and brugia malayi. the dependence of these parasites on their endosymbionts has led to the use of antibiotics directed against the wolbachiae, antibiotics that have been demonstrated to have a profound salutary effect on filarial infections. in 2009, coulibaly et al. conducted an open-label randomized trial of doxycycline, an antibiotic, for mansonella perstans infection. this resulted in a dramatic and sustained decrease in microfilarial levels: they decreased to 23% of pretreatment levels at 6 m after treatment and to 0% of pretreatment levels at 12 m after treatment. in addition, doxycycline has been shown to have macrofilaricidal activity, which is unique among the drugs for filariasis. however, in some areas, such as gabon and uganda, wolbachia endosymbionts have not been detected in the microfilariae of m. perstans. this suggests some geographic isolates of m. perstans may have lost (or gained) the endosymbiont. this presents a controversial argument for the use of doxycycline as treatment of filarial infections. on one hand, doxycycline has been shown to be one of the only successful treatments for m. perstans, and could facilitate the eradication of filarial parasites. however, some scientists argue that the treatment of filariasis with doxycycline may select worms that will have already integrated wolbachia genes into their genome, which could potentially have unforeseen consequences. such lateral gene transfer has occurred in various geographic isolates of b. malayi, in which a fraction of the wolbachia endosybmiont genome is integrated into the chromosome of its nematode host (the parasite). when this integration occurs, wolbachia can no longer be targeted as means for treatment for filariasis. combination regimens combination treatments consisting of dec plus mebendazole, or ivermectin and albendazole, have been shown to result in a highly significant fall in microfilariae. other studies have challenged these findings, suggesting the combination treatment of ivermectin and albendazole does not significantly reduce microfilariae levels more than a single treatment regimen. epidemiology m. perstans is found in tropical africa, central and eastern south america, central america, and the caribbean. the parasite is widespread in many parts of sub-saharan africa. infections have been reported from 33 countries in this region. in certain locations, extremely high proportions of the inhabitants show signs of infection. it often occurs among poor populations living in rural villages. m. perstans is also found in the americas in venezuela, trinidad, guyana, suriname, northern argentina and the amazon basin. this parasite does not occur in asia. it also does not occur in the most northern and southern regions of africa. a recent review of m. perstans in africa states that about 114 million people are infected with this parasite in africa today. public health and prevention strategies the ongoing large-scale programs for control of onchocerciasis and lymphatic filariasis have paid little attention to mansonelliasis. despite the high prevalence of m. perstans in areas of tropical africa, such as uganda, the congo, the republic of cameroon, and gabon, no vector programs have been instituted for any of the mansonelliasis-causing parasites. major reasons for this lack of attention are that m. perstans infections prevail in poor, rural populations and that infection with the parasite has not been linked with a clear and distinct medical picture. much of the information regarding m. perstans has been obtained as a byproduct from studies of other filarial parasites. mansonelliasis can thus be classified as one of the most neglected among the neglected tropical diseases. culicoides midges are small enough to pass through screening or mosquito nets, so these would not be helpful. protection of visitors to endemic areas can be achieved through the use of insect repellents. wikimedia commons has media related to mansonella perstans.