Parasitology(Helminthology)

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  • Topic: Immune system, Loa loa filariasis, Filariasis
  • Pages : 7 (2186 words )
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  • Published : February 1, 2013
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TABLE OF CONTENTS PAGES INTRODUCTION……………………………………………………………………………. 2 LIFE CYCLE OF Loa loa ……………………………………………………………...4 PATHOLOGY of Loa loa …………………………………………………………………… 6 IMMUNE RESPONSE AND MOLECULAR BIOLOGY OF Loa loa………………... 9 CONCLUSION………………………………………………………………………………...11 REFERENCES

TERM PAPER TOPIC: PATHOLOGY , IMMUNE RESONSE AND MOLECULAR BIOLOGY OF Loa loa . INTRODUCTION Loa loa is a filarial parasite transmitted by tabanid female flies of the genus Chrysops (C silacea and C dimidiate). The incidence of infection within endemic region of the central and west African rain forest is high with 20-40% of the population being microfilaraemic , and about twice as many habouring adult worms without showing patent microfilaraemia (Dupont et al.,2007). The adult worms actively migrate through subcutaneous tissues at rates of up to 1cm/ min. Female Loa loa measures 50- 70mm in length and 0.5mm in diameter, while the males measures 30 -35mm in length and 0.4mm in diameter. The microfilariae forms, measures 290-300µm by 6-8µm in size. During infection the microfilariae forms are released into the blood stream, where they become numerous between 10a m and 2pm(diurnal periodicity). Moreso, the presence of the sheath and three or more terminal nuclei distinguish the microfilariae of L. loa from other blood –borne microfilariae. ( Strickland, 2000) Transmission is by day –biting female tabanid flies, which pick up the microfilaria of L loa during blood meals . The injested microfilariae lose their sheath , penetrate the gut wall of the tabanid female fly, and migrate to the cells of the fat body , where they molt twice . The infective filariform larvae (L3)develop in 10 to 12 days and moves to the proboscis. When new host is biting by the female tabanid fly, the infective filariform larvae are injected and develop into adult worms over the course of 6- 12months .( John and Wayne, 2005) L loa infection ( Loiasis) is quite broad , ranging from asymptomatic infection to life threatening complication, which includes meningoencephalitis ,renal failure and endomyocardial fibrosis.

Thus , L loa infection often induces a mild to moderate pathology with patients presenting with pruritis, localized angioedema (Calabar swelling), arthralgia or ocular problems caused by conjunctival migration of adult worms. Also, fibrotic or inflammatory reactions around adult worm may cause hydrocele or intestinal blockage. (Strickland, 2000) The level of microfilariaemia is a critical parameter in the transmission of disease(Piessens and Partono ,2007). Immunity may be seen as a control measure of microfilariaemia, killing of adult worm or a resistance to infection that operates against the infective L3 stage. However, studies of the host immune response mechanisms implicated in the control of microfilaraemia , in the amicrofilaraemic ( Mf- ) individual have shown evidence of antibody- dependent cell cytotoxicity, not only for Loa loa infection, but also for other filariasis. Thus, the circulating anti- sheath antibodies is present in sera of amicrofilaraemic (Mf- ) Loa loa infected individual and absent in heavily infected (Mf+)microfilaraemic individual ( Pinder et al ., 1990) Many studies on molecular biology, concerning cellular immune responses induced by filariae infections and their implication in protection and control of microfilaraemia have been carried out. Although , no studies have been published on the...
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