*Corresponding author email: kokothogola2008@gmail.com Symbiosis Group Symbiosis Group Symbiosis www.symbiosisonline.org www.symbiosisonlinepublishing.com ISSN Online: 2381-2907 Effects of Anticoccidial Drugs on Gross and Histopathological Lesions Caused by Experimental Rabbit Coccidiosis Kennedy O Ogolla 1* , Paul O Okumu 1 , Peter K Gathumbi 1 and Robert M Waruiru 1 1 Department of Veterinary Pathology, Microbiology and Parasitology, University of Nairobi, P.O. Box 29053-00625, Kangemi, Nairobi, Kenya. SOJ Veterinary Sciences Open Access Research Article Abstract Effects of commonly used anticoccidial drugs in treating lesions caused by intestinal and hepatic coccidiosis have not been described for anticoccidial-drugs used in Kenya. The objective of this study was to describe the effects of four anticoccidial drugs on gross and histopathological lesions caused by artificially-induced mixed Eimeria infection with inoculant dose of E. flavescens (20%), E. perforans (21%), E. intestinalis (9%), E. coecicola (4.2%), E. media (11.2%), E. piriformis (10.6%), E. stidae (16%), and E. Magna (8%). In a controlled laboratory trial, 60 weaner rabbits were randomly allocated to treatment groups A, B, C, D, E and F. Each group had 10 rabbits. Groups A and C served as uninfected-untreated and infected- untreated control groups, respectively. Groups B, D, E and F were experimentally infected and treated with amprolium, diclazuril, sulfachloropyrazine, and trimethoprim-sulfamethoxazole, respectively. On day 30 post treatment, 3 rabbits from each treatment group were selected randomly and humanely euthanized for gross and microscopic lesion examination. Diclazuril and sulfachloropyrazine treatment groups had significantly minimal to no macroscopic and microscopic lesions. This was consistent with a high efficacy of the drugs in reversing intestinal and hepatic lesions of coccidiosis in rabbits. Rabbits from amprolium, trimethoprim-sulfamethoxazole and infected-untreated control groups presented with severe intestinal and hepatic gross lesions characterized by extensive hepatomegaly, numerous raised hepatic multinodular lesions and marked congestion of the intestines that indicated mild to no effect of the drugs in reversing hepatic and intestinal lesions. Microscopic lesions in rabbits treated with amprolium and trimethoprim-sulfamethoxazole had marked desquamation of intestinal and bile duct epithelium, distended and thickened bile duct, numerous coccidian parasites at different stages of development in duct epithelium and mature oocysts in the intestinal and bile duct lumens; as was in positive control group. Additionally, rabbits from the three treatment groups recorded higher intestinal and hepatic histological lesion scores. Keywords: Amprolium; Diclazuril; macroscopic; pathology; rabbits; Sulfachloropyrazine. Received: 8 June, 2018; Accepted: 22 June, 2018; Published: 27 June, 2018 *Corresponding author: Kennedy O. Ogolla, University of Nairobi, PO Box 29053-00625, Kangemi, Nairobi, Kenya, Tel: +254710143604.Email address: kokothogola2008@gmail.com Introduction Rabbit coccidiosis is a protozoan infection caused by Eimeria spp. parasites [1]. Two forms of coccidiosis affect rabbits resulting in mild to severe macroscopic (gross) and microscopic (histopathologic) lesions [2]. One form is hepatic coccidiosis caused by Eimeria stiedae that targets the liver resulting in high morbidity and mortality depending on infective dose [1]. The other form is intestinal coccidiosis caused by several Eimeria species which have varied pathogenicity and target sites along the intestinal tract [1]. Most pathogenic of these are E. intestinalis and E. flavescens; E. magna, E. media, E. irresidua, E. perforans, E. piriformis, E. exigua and E. vejdovskyi have moderate to mild pathogenicity [3]. Mixed infection by both forms are common with weaner rabbits being most susceptible to the infection [4, 5]. Transmission of both forms of coccidiosis is mainly by fecal- oral route through consumption of feed and water contaminated by sporulated oocysts [6]. Most cases of hepatic coccidiosis present with gross and histological lesions characterized by hepatomegaly, raised multinodular lesions on the liver surface, distended gallbladder, dilated biliary tree, distended bile duct, atrophy of biliary epithelium, hepatocyte necrosis among others [7-14]. Gross and microscopic intestinal lesions of intestinal coccidiosis have been described in numerous studies [1, 11, 14, 15]. Several anticoccidial drugs are available for preventing and treating these lesions [16]. Diclazuril, a derivative of benzeneacetonitrile, is indicated for prophylactic and curative use in rabbits at 5ppm and 10ppm, respectively [17]. It acts by blocking the excretion of oocysts which interrupts the life cycle of Eimeria spp. [18]. Similarly, sulphonamides such as sulfadiazine, sulfamethazine, sulfamerazine and sulfaquinoxaline have been used in treatment and prevention of rabbit coccidiosis for decades [19]. Other anticoccidial drugs that have been widely used on clinical coccidiosis under various dosages with varied efficacies include amprolium, salinomycin, maduramycin, monensin, clopidol, narasin, robenidine and lasalocid [16]. Most coccidiostats are rarely effective against coccidiosis once rabbits present with clinical signs [1]. Consequently, they are effective when administered on day of exposure to the oocyst [20]. Majority of coccidiostats inhibit metabolic pathways of merozoites, meronts and sporozoites thus interrupting completion of the life cycle [16]. Efficacious therapeutic anticoccidials are able to either