Abstract
Theileriosis is a blood piroplasmic disease that adversely affects the livestock industry, especially in tropical and sub-tropical countries. It is caused by haemoprotozoan of the Theileria genus, transmitted by hard ticks and which possesses a complex life cycle. The clinical course of the disease ranges from benign to lethal, but subclinical infections can occur depending on the infecting Theileria species. The main clinical and clinicopathological manifestations of acute disease include fever, lymphadenopathy, anorexia and severe loss of condition, conjunctivitis, and pale mucous membranes that are associated with Theileria-induced immune-mediated haemolytic anaemia and/or non-regenerative anaemia. Additionally, jaundice, increases in hepatic enzymes, and variable leukocyte count changes are seen. Theileria annulata and Theileria parva induce an incomplete transformation of lymphoid and myeloid cell lineages, and these cells possess certain phenotypes of cancer cells. Pathogenic genotypes of Theileria orientalis have been recently associated with severe production losses in Southeast Asia and some parts of Europe. The infection and treatment method (ITM) is currently used in the control and prevention of T. parva infection, and recombinant vaccines are still under evaluation. The use of gene gun immunization against T. parva infection has been recently evaluated. This review, therefore, provides an overview of the clinicopathological and immunopathological profiles of Theileria-infected cattle and focus on DNA vaccines consisting of plasmid DNA with genes of interest, molecular adjuvants, and chitosan as the most promising next-generation vaccine against bovine theileriosis.
Highlights
Animal Science Research Centre, Malaysian Agricultural Research and Development Institute, Department of Veterinary Pre-clinical sciences, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Research Centre for Ruminant Diseases, Faculty of Veterinary Medicine, Universiti Putra Malaysia, Tel.: +60-11-352-01215 (O.A.A.); +60-19-284-6897 (H.H.)
T. parva infections in cattle are characterized by a shorter course of the disease, a low number of Theileria schizont-infected cells, very low piroplasm parasitaemia when compared to East Coast fever [26] and buffalo-derived T. parva is not transmissible from infected cattle [29]
Theileria annulata caused a regenerative anaemia with significant decreases in the red blood cells (RBCs) count, packed cell volume (PCV), haemoglobin (Hgb) concentration, mean corpuscolar haemoglobin concentration (MCHC) with increased mean corpuscular volume (MCV), and marked reticulocytosis in infected Holstein cattle [71]
Summary
Bovine theileriosis is an important tick-borne disease of domesticated cattle in tropical and subtropical countries, caused by several Theileria species belonging to the phylum Apicomplexa [1]. Schizont-infected cells are seldom found in the circulating blood and are not important in the pathogenesis of benign forms of bovine theileriosis but play a major role in the pathogenesis of diseases caused by the so called schizont-transforming species [15,21]. The cattle-adapted T. parva, which causes East Coast fever, is an economically important Theileria species that affects cattle in Sub-Saharan Africa. This haemoprotozoan represents a subpopulation of T. parva that has adapted to maintenance in cattle. T. parva infections in cattle are characterized by a shorter course of the disease, a low number of Theileria schizont-infected cells, very low piroplasm parasitaemia when compared to East Coast fever [26] and buffalo-derived T. parva is not transmissible from infected cattle [29]. The names of diseases caused by pathogenic species are reported in brackets
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