Lymphocyte infectivity and characterization of theileria parva strains isolated from paddocks in Kiambu district

Abstract

East Coast Fever, a disease of cattle that results in death by respiratory failure IS caused by Theileria parva. Due to the widespread occurrence, the characterization of Theileria species and diagnosis of the disease has become increasingly difficult. An attempt was made to study the infectivity and pathogenicity and to characterize various T. parva strains using observations of their clinical signs, parasitological, haematological and post-mortem findings as indicators. The clinical picture was found to be consistent to the findings of previous workers. However, when intra-lymphocytic theilerial parasites grown in vitro were assessed USIng antibodies specific to schizont epitopes, a marked antigenic diversity was noted between and within strains. Monoclonal antibodies were thus useful In characterizing extra- and intra- strain differences in T. pm·va. The Western blot technique further revealed polymorphism 111 the Sizes of the Polymorphic Immunodorminant Molecule (PIM) ranging from 80 - 90 kilodaltons in isolates obtained from the same paddock and also when compared to T. parva Muguga. Two batches of Theileria sporozoites were used for the comparison of the in vitro infectivity and early developmental stages of Theileria infection to peripheral blood mononuclear cells obtained from the same animal. Similarities were noted in the rates and periods of infectivity (3 - 6 days) regardless of the strain and sporozoite dilution. However, they showed different growth and cultural characteristics with T. parva Marikebuni producing grape-like clusters whereas the breakthrough parasite to T. par va Marikebuni immunization resulted in a uniform sheet of single cells in culture.