Parasitol Res (1989) 75:655-656 Parasitnlngy Research 9 Springer-Verlag 1989 Anthelmintic activity of praziquantel on RMllietina tetragona in chickens I.E.M. Nurelhuda, E.E. Elowni*, and T. Hassan Faculty of Veterinary Science, University of Khartoum, P.O. Box 32, Khartoum-North, Sudan Abstract. Praziquantel was tested against mature (17-day-old) and immature (7-day-old) Raillietina tetragona in experimentally infected chickens using single oral doses of 10, 7.5, 5, or 2.5 mg/kg body wt. The compound showed potent anticestodal ac- tivity, with 100% efficacy at 10, 7.5, and 5 mg/kg against immature worms and an efficacy of 100%, 97.1%, and 95% against mature worms when giv- en at 10, 5, and 2.5 mg/kg, respectively. Residual worms surviving drug treatment had less biomass than the controls. Praziquantel appears to be well tolerated by chickens, and treated birds showed no clinical reactions at any of the doses tested. Chicken tapeworms often cause serious problems in infected flocks (Elowni 1984). However, no reli- able commercial product is yet available for specif- ic use against these parasites. Praziquantel has been reported to be highly effective against juvenile and adult cestodes of dogs, cats, ruminants, rats, mice, and man (Baldock et al. 1977; Bylund et al. 1977; Thomas and G6nnert 1977, 1978; Thakur et al. 1978). The objective of this study was to test the efficacy of this compound against chicken tape- worms using the fowl cestode Raillietina tetragona as an experimental model. Materials and methods Birds. Fertile White Leghorn eggs were obtained from Kuku Poultry Research Unit in Khartoum and were hatched in an incubator in the Department of Parasitology, University of Khartoum. Birds were raised in the laboratory under conditions preventing accidental infection with tapeworms. They were pro- * Present address and address for reprint requests: Faculty of Veterinary Medicine, A1-Fateh University, P.O. Box 13662, Tri- poli, Libya vided with an authentic grower diet and water ad libitum. Chicks were used when they reached ~8 days of age. Infection. R. tetragona cysticercoids were recovered by the dis- section of wild-caught ants (Pachycondyla sennaarensis). The required number of larvae, suspended in normal physiological saline, were fed in gelatin capsules to chicks previously starved for 5h. Treatment. Praziquantel (Droncit, Bayer AG) tablets were crushed to a fine powder and the required doses were given orally to chicks. The drug dose was calculated according to the mean body weight of birds in the groups to be treated. Experimental design. Praziquantel was tested against both ma- ture (17-day-old) and immature (7-day-old) R. tetragona. The evaluation of the efficacy of this compound was based on the controlled test of Moskey and Harwood (1941). In any particu- lar experiment, birds of the same age that had been exposed to similar levels of infection were used. Treatments were allo- cated at random to these birds, and respective groups were designated as "treated" or "untreated controls." Recovery of worms. Birds were sacrificed 7 or 14 days after treatment, depending on the schedule of experiments (Tables 1 and 2). By this time, any stunted or destrobilated worms surviv- ing drug treatment would be expected to grow sufficiently and could therefore be easily identified at necropsy. The intestine of each bird was slit open longitudinally in a shallow tray con- taining normal saline, and any visible worms were collected. Search for scolices and stunted parasites was made by repeated microscopic examination of intestinal segments incubated at 37~ in normal physiological saline and by examination of the incubation medium. Analysis of results. The total recoveries (number of cysticercoids given to treated birds or untreated controls and recovered as worms, regardless of worm size) were compared by the chi- square test, Yates' correction (Siegel 1956). Differences were considered to be significant when P_<.0.05. To take into account differences in the numbers of birds used in the various experi- ments and to provide a uniform parameter for comparing the efficiency of the drug at various doses, recovery figures were transformed into percentages using a mean index with the for- mula: a-b -- x 100 = % efficacy, a