1. Parasitology

2. Introduction Continue

3. Immunity to parasites Over millions of years of evolutions, parasites become well adapted to their hosts and show marked host specificity. e.g. [ The malarial parasites of birds, rodents or man can each multiply only in their own particular kind of host].

4. There are some exceptions for the host specificity. e.g. Toxoplasma not only able to invade and multiply in all nucleated mammalian cells, but can also infect immature mammalian erythrocytes of birds. The pig ‘s tapeworm can infect man. Continue

5. Host resistance may be controlled by a number of immune response genes. Studies revealed that even in a small community people might vary greatly in their risk of infection through differences in their exposure to the invasive parasites. The development of immunity is a complex process arising from the interactions of many different kinds of cells over a period of time. Continue

6. The effect is often local. Many cell types secreting several different mediators, may be present at the site of immune rejection. Moreover, the processes involved in controlling the multiplication of a parasite within infected individual may differ from those responsible for the ultimate development of resistance to further infection. Continue

7. In some helminthes infections a process called “ Concomitant Immunity ” occurs, whereby an initial infection is not eliminated but established, and the host then acquires resistance to invasion by new worms of the same species. In general, Humoral responses are necessary to eliminate extracellular parasites such as those live in blood or body fluids. Continue

8. For example, antibody, alone or with complement can damage some extracellular parasites, but better when acting with effector cells as macrophages or neutrophils. blocks prevent Thus malarial antibodies against extracellular forms blocks their capacity to invade new cells but cell-mediated response prevent the development of the liver stage within liver cells. Continue

9. The First Line Defense Effector Cells Macrophages Neutrophils Eosinophils Platelets 1 2 3 4

10.  Macrophages:-  Protect against small parasites and also larger one, when stimulated by cytokines. e.g. [ It kills erythrocytic stage of malaria and large larval stage of Schistosoma]. Continue

11.  Neutrophils:-  Can kill large and small parasites. e.g. [ W ith complement it is more destructive to larvae of S. mansoni & T. spiralis than eosinophils]. Continue

12.  Eosinophils:-  Are characteristically associated with worm infections and evolved specifically as a defense against the tissue stage of parasites that are too large to be phagocytosed. Continue

13.  Platelets:-  Can also kill many types of parasites. e.g. [ Larval stage of flukes, toxoplasma and Trypanosome cruzi ]  Their activity enhanced by cytokines. Continue

14.  Praziquantel is very safe, taken as a single or divided dose according to the worm type.  Dose is calculated according to the patient weight.  Praziquantel is swallowed, not chewed; as it is very bitter in taste. Continue