Review Article Volume 3 Issue 4- September 2018 Ann Rev Resear Copyright © All rights are reserved by Fábio Pereira Leivas Leite Equine Theileriosis: Review Ana Muñoz Vianna 1,2 , Ana Paula de Souza Stori de Lara 3 , Guilherme Borges Weege 3 , Rodrigo Casquero Cunha 2 and Fábio Pereira Leivas Leite 1,2 * 1 Department of Microbiology and Parasitology, Federal University of Pelotas (UFPel), Brazil 2 Postgraduate Program in Veterinary Medicine, Federal University of Pelotas (UFPel), Brazil 3 Department of Microbiology and Parasitology, Federal University of Pelotas (UFPel), Brazil Submission: June 06, 2018; Published: September 28, 2018 * Corresponding author: Fábio Pereira Leivas Leite, Veterinary Graduate Program Federal University of Pelotas - UFPel, Capão do Leão Campus, Pelotas, RS, Brazil, Tel: ; Email: Introduction Equine piroplasmosis, caused by the intracellular protozoa Theileria equi and Babesia caballi, belonging to the phylum Apicomplexa, is considered the most important horse disease transmitted by ticks [1]. The disease is caused by infection with Theileria equi, formerly Babesia equi [2] and is called equine theileriosis [3,4]. The phylum Apicomplexa includes a large group of organisms, including the order Piroplasmida, comprised of compulsory vertebrate and invertebrate parasites [5]. The organisms have an apical complex containing secretory organelles involved in invasion and the parasite remains within the host [5]. Theileria equi has a wide geographic distribution and infects horses in Europe, Asia, Africa and South and Central America, but is considered endemic in tropical and subtropical [6]. Equine theileriosis stands out as a major cause of both horse illness and of losses to the horse raising industry. Even with improvements in health, piroplasmosis causes losses associated with clinical factors and through international restrictions on the transit of seropositive animals [7,8]. Theileria equi is small, 2-3 mm in length [9], pleomorphic within erythrocytes, and is isolated in pairs or when forming tetrads (Maltese cross). When parasitemia is low, they are barely visible under the microscope and can be easily confused with technical artifacts due to their small size [7]. The parasite is carried by ticks, especially the genera Anocentor, Amblyomma, Rhipicephalus and Haemaphysalis [10]. Rhipicephalus microplus is considered the responsible for infestations in horses when sharing pastures with bovine [11,12]. When taking a blood meal on a host, (an infected equine), the tick vector ingests erythrocytes containing the gametocytes that in its intestines will give rise to the gametes that will fuse to form the zygote. The zygote differentiates to the mobile form ookinete which is transported through the hemolymph to the salivary glands of the tick. Within the salivary glands, sporoblasts, and finally, sporozoites will give rise (MEHLHORN & SCHEIN, 1998.Theileria equi transmission occurs through tick blood meals which contain infective (sporozoite) forms (UILENBERG, 2006). Theileria equi exhibits a biphasic cycle in the mammalian host with an intra-leucocyte development phase followed by an intra- erythrocytes phase (RAMSAY et al., 2013). The intra-leucocyte phase includes infection of B and T lymphocytes, monocytes, and macrophages. However, unlike others theilerias, the pre- erythrocytic stage of T. equi has not been clinically associated with disease, since it is not necessary to complete the lifecycle Ramsay et al. 2013. Approximately 2 days after infection T. equi schizonts begin to infect lymphocytes, and by 15 days merozoites can be viewed through blood smears in erythrocytes. The parasitemia reaches approximately 7% of the erythrocytes, but in immunocompromised animals it can reach 80% [14]. In nature, horses are T. equi reservoirs where transstadial transmission can occur [15]. In transstadial transmission, larvae that feed on infected horses are infected yet maintain sporozoites in their salivary glands. When changing into nymphs, these will then Ann Rev Resear 3(4): ARR.MS.ID.555620 (2018) 00100 Annals of Reviews and Research Abstract Equine theileriosis, caused by the Apicomplexa protozoan Theileria equi, is an intra-erythrocytic parasite disease found in horses, and it is widely distributed throughout the world. Its prevalence and endemicity are linked to the presence of tick vectors and chronic equine carriers. Diagnosis of theileriosis is based on serological methods, including ELISA (Enzyme-Linked Immunosorbent Assay), IFAT (indirect fluorescent antibody), and molecular methods such as PCR (Polymerase Chain Reaction). Theileria equi has merozoite surface proteins, equi merozoite antigens (EMA-1, EMA-2, EMA-3 and EMA-6). These antigens play an important role in pathogenesis and provide as host immune response targets against the parasite. EMA-1 and EMA-2 have been identified as immunodominant antigens and they are expressed on the surface of extra-erythrocyte merozoites. EMA-1 protein has been used in commercial testing of immunodiagnostic; however, EMA-2 is a highly conserved immunogenic protein and a promising target. The aim of this study is to contribute to improving the diagnosis and prevention of equine theileriosis. Keywords: ELISA; Immunodiagnostics; Surface protein and Theileria equi