Open AccessA prospective cohort study of Cutaneous Leishmaniasis due to Leishmania major: Dynamics of the Leishmanin skin test and its predictive value for protection against infection and disease
Author(s) -
Jihène Bettaieb,
A. Toumi,
Wissem Ghawar,
Sadok Chlif,
Mariem Nouira,
Nabil Belhaj-Hamida,
Alya Gharbi,
Nissaf Bouafif ép Ben Alaya,
Dhafer Laouini,
Hechmi Louzir,
Koussay Dellagi,
Afif Ben Salah
Publication year - 2020
Publication title -
plos neglected tropical diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.99
H-Index - 135
eISSN - 1935-2735
pISSN - 1935-2727
DOI - 10.1371/journal.pntd.0008550
Subject(s) - incidence (geometry) , medicine , prospective cohort study , leishmaniasis , disease , population , cutaneous leishmaniasis , cohort study , immunology , confounding , cohort , demography , environmental health , physics , sociology , optics
Background Leishmanin Skin Test (LST) is considered as a useful indicator of past infection by Leishmania parasites. However, the temporal dynamics of a positive LST under different epidemiologic scenarios and whether it relates to the protection against the recurrence of an overt disease are not fully documented. Methodology/Principal findings We report here on a population based prospective study conducted on 2686 individuals living in two foci located in Central Tunisia, to assess over a one-year epidemiologic season, the incidence of Leishmania ( L .) major infection and disease and changes in LST reactivity. The two foci were both endemic for Cutaneous Leishmaniasis (CL) due to L . major , but contrasted in their history for this disease (ie: an old focus versus a recent focus). We found that most infections occurred in the new focus (290/1000; 95% CI: 265–315 person-years) with an incidence rate of CL lesions 2.4 times higher than in the old focus. Likewise, the rates of LST reactivity reversion and loss, in the new focus, were 99/1000[38–116] person-years and 14/1000[8–21] person-years, respectively. Loss of LST reactivity was not noticed in the old focus. Interestingly, the incidence rates of symptomatic infection did not differ significantly according to the LST status at enrolment (negative versus positive) between the combined foci and the new one. Conclusions/Significance Our findings confirm LST as a good tool for assessing L . major cryptic infection. However, the instability of the LST positivity in new foci should be considered as an important confounder of the outcome of this infection when developing a research protocol for vaccine trial.