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Age, acquired immunity and the risk of visceral leishmaniasis: a prospective study in Iran

Published online by Cambridge University Press:  01 September 1999

C. R. DAVIES  and
A. S. MAZLOUMI GAVGANI
C. R. DAVIES
Affiliation:
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT
A. S. MAZLOUMI GAVGANI
Affiliation:
Department of Medical Parasitology, University of Tabriz Medical Sciences, P.O. Box 51745-347, Tabriz, Iran
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Abstract

In order to investigate the phenomenon of age-related immunity to visceral leishmaniasis, a 1 year prospective survey was carried out on 5671 people in a Leishmania infantum focus in north-west Iran. The average incidence rate of infection since 1985 was 2·8%/year with all ages equally at risk. One in 13 infections in children led to visceral leishmaniasis (VL), and this ratio decreased significantly with age. Seroprevalence also dropped rapidly with age, suggesting that the same process may affect both clinical outcome and the humoral immune responses. Cell-mediated immunity was associated with a reduction in the seroconversion rate and an increase in the serorecovery rate. Even amongst people with no detectable cell-mediated immunity to Leishmania, the seroconversion rate decreased and the serorecovery rate increased with age. All current VL patients had a negative leishmanin skin test response. Hence, adults may develop protection against L. infantum through 2 processes, 1 dependent and 1 independent of acquired cell-mediated immunity.

Keywords

Leishmania infantumvisceral leishmaniasisacquired immunity
Type
Research Article
Information
Parasitology , Volume 119 , Issue 3 , September 1999 , pp. 247 - 257
Copyright
1999 Cambridge University Press

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