Life-cycle of the parasite

Neumann, S., Ziv, E., Lantner, F. and Schechter, I. (1 993) Regulation of Hsp70 gene expression during the life cycle of the parasitic helminth Schistosoma mansoni. European Journal of Biochemistry 21 2, 589-596. 

The effectiveness of a drug treatment is related to the particular species of infecting plasmodium and the stage of its life cycle. A summary of the life cycle of the parasite and the sites of therapeutic interventions are presented in Figure 35.4. 

A pathogenic disease depends on the life cycle of the parasite. The environment greatly affects this cycle. Temperature and moisture are especially important. They affect the activity of the parasite, the ease with which a plant becomes diseased, and the way the disease develops. 

After fertilization the female worms migrate under the skin and produce a dermal blister which causes irritation. When the patient scratches the skin or the blisters come in contact with water, they burst liberating numerous motile rhabditi-form larvae which are soon engulfed by the C /clops thus the life cycle of the parasite is completed. 

The gastrointestinal tract is the most common seat for a variety of round-worms in domestic and wild animals. The high prevalence of gastrointestinal nema-todiasis is due to the simpler life cycle of the parasite with no intermediates host and easy access of eggs and larvae to the grazing animals. 

There is strong evidence for the involvement of host (i.e. Human) cell kinases in the facilitation of the life cycle of the parasite. This is not surprising the parasite has evolved and adapted to its complicated life cycle and has presumably made use of the most efficient mechanism to drive its own proliferation, evade the host immune system, and preserve and protect those cells it has elected to grow within. Two recent studies have underscored this notion, and presented a number of host candidate kinases. The first study makes use of a collection of human kinome-related siRNAs to test their potential for reducing the proliferation of malaria parasites in human hepatocytes.41 Five host cell kinases were identified as being required for... 

At present, there are two streams of drug discovery activity that could lead to the successful development of a kinase inhibitor as a drug for Plasmodium Malaria, namely in vitro screening activities around validated kinase targets and deconvolution of key targets revealed from the screening of various Malaria Boxes on various stages of the life cycle of the parasite. 

Besides, it also helps in rendering the parasite incapable of sporulating in the mosquito whereby the life-cycle of the parasite is disrupted squarely. 

The possibility of immunisation against malaria [1, 20, 216, 217] is not strictly within the context of this review of chemotherapy, but it deserves mention because of the potential value in the eventual conquest of the disease just as in other communicable diseases. Immunity to plasmodia shares many features in common with other microbiological infections but, owing to the complicated life cycles of the parasites, the problem is not a simple reaction of the host to a single stage of the parasite, and the factors involved in resistance to plasmodial infection are multiple and varied. Moreover, sterile immunity is frequently not achieved, relatively small numbers of organisms may continue to survive in the immune host, and splenectomy during this state of premunition may lead to recrudescences of infection. 

Classification of antimalarial drugs in relation to the different stages of the life-cycle of the parasite. From L. J. Bruce-Chwatt, Bull. Wld. Hlth. Org. 27, 287 (1962) [32 33]... 

This report will detail current knowledge of the role of IgE in mediating immunity to helminth parasites. Because IgE responses to helminth infections differ based on chronicity of infection, the life cycle of the parasite, and the parasite s location within the host, it is difficult to apply data from one parasite to those of another, particularly in theorizing about the potential effects of anti-IgE therapy. The report will focus, in particular, on schistosomiasis and strongyloidiasis, for which most observational and experimental data have been accumulated to support a protective role for IgE. The latter infection is of particular relevance because of its unusual capacity to replicate within the human host, so-called auto-infection. Although most of the discussion will rely on data from human studies, much of this information is incomplete, and, where appropriate, observations from experimental animal models will be included. 

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