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A review of the progress made in recent years on research and understanding of immunity in insect vectors of human and animal diseases

Published online by Cambridge University Press:  19 September 2011

Godwin P. Kaaya
Affiliation:
The International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya
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Abstract

Different modes of immune reactions of insect vectors of human and animal diseases to nematode and protozoan parasites, fungi, bacteria, viruses and to other biological materials e.g. xenografts are discussed in this paper. Since most of the insect vectors of diseases are adult dipterans with low numbers of circulating haemocytes, their mode of defence against metazoan parasites and fungal pathogens is primarily by means of humoral encapsulation, with little haemocyte participation. Although earlier workers reported that humoral capsules in dipterans were formed without direct participation by haemocytes, this paper reveals increasing evidence of cellular involvement in the formation of humoral capsules, both at the initial and terminal stages of the encapsulation process. The role of phenoloxidase system in non-self recognition and in the process of melanization of haemolymph and capsules formed around parasites and fungal pathogens is also discussed. Immune defence of insect vectors against bacterial invasion by means of haemocytic reactions e.g. phagocytosis and nodule formation and by synthesis and release of humoral antibacterial factors e.g. lysozyme, attacins and cecropins is described and compared with similar reactions reported to occur in other insects. The role of lectins in defence of insect vectors against the parasites they transmit e.g. sandflies against Leishmania, blackflies against Onchocerca and tsetse against Trypanosomes is discussed and the possible mechanisms by which some parasites evade recognition and attack by the vector immune systems are also briefly discussed.

Résumé

Les différents modes de réactions immunisées des insectes vecteurs de maladies humaines et animates centre les nématodes et les protozoaires parasites, les champignons les bactéries, les viruses et autres matériels biologiques par exemple xenogratis sont discutés dans cette publication. Comme plus d' insectes vecteurs de maladies sont des diptères adultes ayant un nombre inférieur d'hemocytes, leur mode de défense centre les métazoaires parasites et les champignons pathogènes est principalement par moyen d'encapsulation humorale, avec une moindre participation d'hemocyte. Bien que des recherches antérieures ont montré que les capsules humorales chez les diptères étaient formées sans participation directe d'hemocytes, cette publication révèle une évidence accrue sur la participation cellulaire dans la formation des capsules humorales, au niveau initial et final du processus d'encapsulation. Le rôle du système phenoloxidase dans le processus de melanisation d'hémolymphe et les capsules formées autour des parasites et des champignons pathogènes est aussi discuté. La défense immunisée des insectes vecteurs centre l'invasion bactérienne par moyen de réactions hémocytaire par exemple la phagocy tose et la formation de nodules et par la synthèse et la liberation des éléments antibactériens humoraux par example lysosomes, attacines et cecropines est décrite et comparée aux réaction apparues chez d'autres insectes. Le rôle de lectines dans la défense des insectes vecteurs contre les parasites qu'ils transmettent par exemple les phlébotomes contre Leishmania, les slmulies contre l'Onchocerca et les mouches tsé-tsé contre Trypanosoma est discuté. Les mecanismes possibles par lesquels certains parasites échappent d'être reconnues et attaqués par les systèmes vecteurs ‘immunises’ sont aussi brièvement discutés.

Type
Reviews: A Ten Year Perspective of Insect Science 1980–1989
Copyright
Copyright © ICIPE 1989

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