SHORT COMMUNICATION Experiments to produce cysts in cultures of Histomonas meleagridis—the agent of histomonosis in poultry Emma Zaragatzki & Heinz Mehlhorn & Fathy Abdel-Ghaffar & Khaled A. S. Rasheid & Elvira Grabensteiner & Michael Hess Received: 28 December 2009 / Accepted: 15 January 2010 / Published online: 4 February 2010 # Springer-Verlag 2010 Abstract Experiments were done with cultured trophozoite stages of different clonal strains (Histomonas meleagridis/ Turkey/Austria/2922-C6/04 and H. meleagridis/Chicken/ Hungary/5009-C2/05) of H. meleagridis in order to induce a cyst formation as it is known in other intestinal parasites. It was shown that the best multiplication of H. meleagridis occurred at 40°C in a full medium 199, when fetal calf serum and rice starch had been added. Under these conditions, numerous amoebic stages (8–12 μm in diame- ter) without and a few with flagellum were seen showing regular reproduction rates. When the conditions of culture were experimentally changed—and thus became worse— by decreasing the temperature, by deprivation of the medium from fetal calf serum and/or rice starch, and by changing the osmolarity, the pH, or the MgCl 2 concentra- tion, many of the amoebic stages (containing starch granules) were destroyed, and several had obtained a spherical shape. If the culture conditions became even worse, smaller spherical stages occurred, which had only diameters of 4–7 μm and which appeared more condensed. Both spherical stages did not contain starch granules. All the previously seen stages disappeared constantly. Since a similar decrease of the optimal living conditions also occurs when intestinal or cloacal feces are deposited outside from the bird’ s body, the results obtained here may underline the interpretation that some of the formerly amoebic stages are able to become large spherical stages and later small spherical stages. The large spherical stage would be some type of precysts while the smaller ones would represent true cysts. Introduction Histomonosis is known to since long threaten the farm culture of many species of birds (McDougald 2005). Although the vegetative stage of the parasite Histomonas meleagridis is known since more than 90 years, its transmission from bird to bird is still under discussion since Tyzzer (1919). Some authors describe a transmission via enclosure of the vegetative stages inside worm eggs (Graybill and Smith 1920; Norton et al. 1999); others believed in the contact of the bird’ s anus with warm feces and or close body contacts, known as cloacal drinking (Tyzzer and Collier 1925; McDougald 2005). Several previous papers collected hints that transmission of H. meleagridis may occur via cysts as it is the case in many protozoans such as Acanthamoeba, which form cysts under bad conditions (Mehlhorn 2008). The papers of Hess et al. (2006a, b), Mielewczik et al. (2008), and Munsch et al. (2008) described stages which might be cysts that could survive the passage of the stomach after oral uptake. Thus, the present study was done to examine whether a cyst E. Zaragatzki : H. Mehlhorn (*) Department of Parasitology, Heinrich Heine University, 40225 Düsseldorf, Germany e-mail: mehlhorn@uni-duesseldorf.de F. Abdel-Ghaffar Department of Zoology, Cairo University, Giza, Egypt K. A. S. Rasheid Department of Zoology, Center of Excellence, College of Science, King Saud University, Riyadh, Saudi Arabia E. Grabensteiner : M. Hess Clinic for Avian, Reptile, and Fish Medicine, University of Veterinary Medicine, Vienna, Austria Parasitol Res (2010) 106:1005–1007 DOI 10.1007/s00436-010-1776-3