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Editorial response: Treatment of cystic echinococcosis--improving but still limited.

Despite efforts to educate persons at risk and the success of control programs in a few countries, cystic echinococcosis, or hydatid disease, caused by the larval form of the cestode Echinococcus granulosus, still constitutes a substantial health problem in most livestock-raising areas of the world [1]. In the United States and Canada, locally acquired cases of cystic echinococcosis are rare; in contrast, imported infections are diagnosed widely, most commonly in immigrants from Middle Eastern countries and, to a lesser extent, from South America and Europe [2]. Cystic echinococcosis is characterized by a slowly growing, fluid-filled cystic lesion (hydatid cyst) in the liver, lungs, or other organs; infection may be asymptomatic until cysts cause noticeable mass effect, and then signs and symptoms vary according to location, cyst size, and number. Until recently, surgery was the only option for treatment of echinococcal cysts; however, surgery has been associated with frequent recurrence and high rates of intra- and postoperative morbidity and mortality. Operative mortality in the first operation varies from 0.5% to 4% but increases with repeated interventions and under conditions of inexperience or inadequate facilities [3, 4]. In the past 20 years, benzimidazole compounds have been shown to have echinococcidal activity, and results of internationally coordinated clinical experiences document that approximately one-third of patients treated with albendazole or mebendazole have been cured of their disease (complete and permanent disappearance of cysts) and even higher proportions (30%‐50%) have responded with significant regression of cyst size and alleviation of symptoms [5‐ 8]. In this issue of Clinical Infectious Diseases, Franchi et al. [9] of the University of Rome report on the long-term follow-up of patients after treatment with albendazole or mebendazole; their findings further reveal the benefits and limitations of chemotherapy. Among 448 patients with 882 evaluable cysts, 74% of cysts showed degenerative changes on ultrasound or CT imaging after the patients received 3- to 6-months of continuous daily treatment with albendazole or mebendazole. Confirming previously reported experience [6, 7], these authors found that the efficacy of albendazole (82%) was superior to that of mebendazole (56%), presumably because of the former compound’s superior pharmacokinetic profile that favors intestinal absorption and penetration into the cyst(s). Continued follow-up of the patients after cessation of treatment revealed progressive degeneration in 22% of the altered cysts; however, 25% showed evidence of regeneration, including increase in size or fluid volume, exogenous vesiculation, or reattachment of the membrane to the cyst wall. The rate of “relapse” was similar for patients treated with either albendazole or mebendazole but was more frequent for cysts with daughter cysts than for primary cysts, for cysts of the liver than for those in the lungs, and for cysts in patients ,30 years of age than in those older; these different responses are presumably related to differences in permeabilities of the cyst membranes in these different types of cases, permitting greater or lesser diffusion of the drug into the cyst. More than three-fourths of relapses were noted within 2 years after the end of treatment and, very importantly, .90% of these cysts regressed on further treatment. Side effects during chemotherapy were minimal and in all patients were reversible without discontinuing treatment: ;20% of patients showed transitory abdominal pain, headaches, alopecia, or elevated serum transaminases. Although not ideal, these findings support the view that chemotherapy alone offers a safe and effective alternative to surgery for the management of cystic echinococcosis in most locations. Future advances in chemotherapy may be achieved by using drugs with higher echinococcidal activity [10].