ORIGINAL PAPER Giardia lamblia: a report of drug effects under cell differentiation Moema A. Hausen & Richard Pereira de Oliveira & Ana Paula Rocha Gadelha & Loraine Campanati & Jorge José de Carvalho & Laís de Carvalho & Helene Santos Barbosa Received: 13 March 2009 / Accepted: 24 April 2009 / Published online: 12 May 2009 # Springer-Verlag 2009 Abstract The Giardia lamblia life cycle is characterized by two phases during which two major cell differentiation processes take place: encystation and excystation. During encystation, the trophozoites transform into cysts, the resis- tance form. Once ingested by a susceptible host, the cysts are stimulated to excyst in the stomach, and the excysted trophozoites adhere to the epithelium of the upper small intestine. Our work analyses the effects of four benzimidazole derivatives during Giardia differentiation into cysts and evaluates the excystation efficiency of water resistant cysts. Albendazole (AB) showed the most significant results by inhibiting encystation about 30% and a decreasing rate of excystation efficiency. The ultrastructural organization of the cyst adhesive disk was notably affected by AB treatment. Although other benzimidazoles showed some effect on encystation, they were not able to inhibit the excystation process. It is known that the benzimidazoles affect the cytoskeleton of many organisms but how it interferes in Giardia differentiation processes is our main focus. The importance of studying Giardia's differentiation under drug action is reinforced by the following arguments: (1) Cysts eliminated by hosts undergoing treatment could still be potentially infective; (2) once the host has been treated, it would be desirable that the shedding of cysts into the environment is avoided; (3) the prevention of Giardia dissemination is a question of extreme importance mainly in underdeveloped countries, where poor sanitary conditions are related to high rates of giardiasis. This report concerns the importance of keeping the environment free from infective cysts and on Giardia’ s drug resistance and differentiating abilities. Introduction Giardiasis is one of the most commonly found enteric parasitic infections in clinical laboratories; diagnosis is made mainly through the observation of Giardia lamblia cysts in stools samples. The ability of the protozoan G. lamblia to undergo differentiation in response to signals from the host is the key to its pathogenesis (Reiner et al. 2003). The life cycle of G. lamblia includes two morpho- Parasitol Res (2009) 105:789–796 DOI 10.1007/s00436-009-1463-4 M. A. Hausen : R. P. de Oliveira : A. P. R. Gadelha Laboratório de Microscopia e Processamento de Imagens, Departamento de Histologia e Embriologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, Av. Prof. Manoel de Abreu, 444, 3° andar, Rio de Janeiro, RJ, 20550-170, Brazil L. Campanati Laboratório de Morfogênese Celular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, CCS, Bloco F-024, Rio de Janeiro, RJ, Brazil J. J. de Carvalho Laboratório de Microscopia Eletrônica, Departamento de Histologia e Embriologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, Av. Prof. Manoel de Abreu, 444, 3° andar, Rio de Janeiro, RJ, 20550-170, Brazil L. de Carvalho Laboratório de Cultura de Células, Departamento de Histologia e Embriologia, Instituto de Biologia, Universidade do Estado do Rio de Janeiro, Av. Prof. Manoel de Abreu, 444, 3° andar, Rio de Janeiro, RJ, 20550-170, Brazil H. S. Barbosa (*) Laboratório de Biologia Estrutural, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil 4365, Rio de Janeiro, RJ, 21045-900, Brazil e-mail: helene@ioc.fiocruz.br