Occurrence of Leishmania infantum parasitemia in asymptomatic blood donors living in an area of endemicity in southern France

Abstract

Visceral leishmaniosis (VL) due to Leishmania infantum (L. chagasi) is a lethal disease if untreated, but asymptomatic L. infantum infections have been reported previously. A better understanding of parasite transmission, dissemination, and survival in the human host is needed. The purpose of this study was to assess whether L. infantum circulated in peripheral blood of subjects with no history of VL. Sera from 565 blood donors were screened by Western blotting to detect Leishmania-specific antibodies and identify individuals with probable past exposure to Leishmania. Seropositivity was found in 76 donors whose buffy coats were examined by PCR and direct culture. The parasite minicircle kinetoplast DNA was amplified from blood samples of nine donors. Promastigotes were detected by culture in blood samples from nine donors. Only two donors were PCR and culture positive. These results indicate that L. infantum circulates intermittently and at low density in the blood of healthy seropositive individuals, who thus appear to be asymptomatic carriers. Implications for the safety of blood transfusion are discussed.

FIG. 1

L. infantum seropositivity and presence in blood samples of 16 asymptomatic blood donors with no history of VL. Parasite-positive donors were identified among 76 L. infantum-seropositive individuals whose Western blots revealed characteristic 14- and/or 18-kDa bands (arrows). The profile of a VL patient (lane VLp) is shown. The presence of Leishmania was indicated either by parasite kDNA amplification (Fig. 2) or by direct culture, as described in Materials and Methods. Blood samples drawn during the Leishmania-transmitting sandflies’ active period (May to October) are indicated.

FIG. 2

PCR amplifications with primers RV1 and RV2 (A and B) and 13A and 13B (C). Lanes 6, 7, 8, and 10 correspond to donors mentioned in the legend for Fig. 1, and lane SpD corresponds to a Leishmania-seropositive donor who was PCR and culture negative. Lanes W and T, two negative controls of PCR runs (distilled water and DNA from a Leishmania-seronegative donor); lanes M, DNA molecular size markers (pUCBM21 cleaved by HpaII and DraI plus HindIII). Upper arrows, PICs constructed with primers RV1 and RV2 (A and B) and 13A and 13B (C) as described in Materials and Methods; lower arrows, Leishmania-specific amplicons.