W.I. Morrison

Bio: W.I. Morrison is an academic researcher. The author has contributed to research in topics: Trypanosomiasis & Theileria. The author has an hindex of 4, co-authored 4 publications receiving 133 citations.

Transformation of Leukocytes by Theileria parva and T. annulata

Abstract: Theileria parva and T. annulata provide intriguing models for the study of parasite-host interactions. Both parasites possess the unique property of being able to transform the cells they infect; T. parva transforms T and B cells, whereas T. annulata affects B cells and monocytes/macrophages. Parasitized cells do not require antigenic stimulation or exogenous growth factors and acquire the ability to proliferate continuously. In vivo, parasitized cells undergo clonal expansion and infiltrate both lymphoid and non-lymphoid tissues of the infected host. Theileria-induced transformation is entirely reversible and is accompanied by the expression of a wide range of different lymphokines and cytokines, some of which may contribute to proliferation or may enhance spread and survival of the parasitized cell in the host. The presence of the parasite in the host-cell cytoplasm modulates the state of activation of a number of signal transduction pathways. This, in turn, leads to the activation of transcription factors, including nuclear factor-kappa B, which appear to be essential for the survival of Theileria-transformed T cells.

An enzyme-linked immunosorbent assay for detection of Theileria parva antibodies in cattle using a recombinant polymorphic immunodominant molecule

Abstract: Field and experimental bovine infection sera were used in immunoblots of sporozoite and schizont lysates of Theileria parva to identify candidate diagnostic antigens. Four parasite antigens of Mr 67,000 (p67), 85,000 (the polymorphic immunodominant molecule, PIM), 104,000 (p104), and 150,000 (p150) were selected for a more detailed analysis. The p67 and p104 antigens were present only in the sporozoite lysates, whereas PIM and p150 were found in both sporozoite and schizont lysates. The four antigens were expressed as recombinant fusion proteins and were compared with each other in an enzyme-linked immunosorbent assay (ELISA) and in the whole-schizont-based indirect fluorescent antibody test (IFAT) in terms of their ability to detect antibodies in sera of experimentally infected cattle. The PIM-based ELISA provided a higher degree of sensitivity and specificity than did the ELISA using the other three recombinant antigens or the IFAT. Further evaluation of the PIM-ELISA using experimental sera derived from cattle infected with different hemoparasites and field sera from endemic and nonendemic T. parva areas showed that the assay had a sensitivity of > 99% and a specificity of between 94% and 98%.

Trypanotolerance, an option for sustainable livestock production in areas at risk from trypanosomosis

Abstract: Trypanosomosis is one of the major constraints on animal production in areas of Africa which have the greatest potential for significant increases in domestic livestock populations and livestock productivity. While the eradication of trypanosomosis from the entire continent is an unrealistic goal, considerable effort has been invested in the control of this disease through the use of trypanocidal drugs, management of the vector and exploitation of the genetic resistance exhibited by indigenous breeds. There is little hope that a conventional, anti-infection vaccine will be produced in the near future. Drug resistance is developing faster than generally thought. The control of the tsetse fly has been attempted over many decades. The decreasing efficacy of available trypanocidal drugs and the difficulties of sustaining tsetse control increase the imperative need to enhance trypanotolerance through selective breeding, either within breeds or through cross-breeding. Trypanotolerance has been defined as the relative capacity of an animal to control the development of the parasites and to limit their pathological effects, the most prominent of which is anaemia. A major constraint on selection for trypanotolerance in cattle, for both within-breed and cross-breeding programmes, has been the absence of practical reliable markers of resistance or susceptibility. Distinct humoral immune response to trypanosome infection is the major feature of bovine trypanotolerance. The role that these responses play in the control of infection or disease is being addressed by ongoing research, but remains a matter of speculation at present. Results in recent years have shown that packed cell volume (PCV) in particular and parasitaemia, the two principal indicators of trypanotolerance, are strongly correlated to animal performance. However, although direct effects of trypanosome infections on PCV and growth are obvious, more sensitive diagnostic methods for reflecting parasite control are required so that individual animals can be categorised reliably for their parasite control capability. One key finding is the major contribution made by each of the indicators evaluated to the overall trypanotolerance variance. Preliminary genetic parameters for PCV provide evidence that trypanotolerance is not only a breed characteristic but is also a heritable trait within the N'Dama population; this brings new opportunities for improved productivity through selection for trypanotolerance. More reliable estimation of genetic parameters of the indicators may well show that these parameters must be handled simultaneously for optimal progress. This would require diagnostics for assessing parasite control capability that identify trypanosome species more accurately, especially in mixed infections. A major advantage of trypanotolerant livestock, particularly N'Dama cattle, is the resistance or adaptation of this breed to many of the important pathogenes which prevail in the sub-humid and humid tropics. Research on practical indicators of resistance to these conditions will be required to establish relevant integrated strategies based on disease-resistant livestock. Selective breeding will require the integration of the traits that farmers hold important for their production systems.