Detection of Leishmania infantum cryptic infection in asymptomatic blood donors living in an endemic area (Eivissa, Balearic Islands, Spain) by different diagnostic methods

Abstract

The extent of cryptic leishmaniasis in blood donors from a Spanish endemic area, (Eivissa Island) was studied using various immunological and parasitological methods. Sera from 656 blood donors were analysed: 16 (2.4%) were positive by ELISA and 50 (7.6%) by Western blot. Peripheral blood mononuclear cells (PBMC) and buffy coat (BC) samples, were analyzed by culture and nested-PCR. DNA of L. infantum was amplified in 27 (22.1%) of 122 PBMC. Parasites were isolated in 3 (4.5%) of 67 BC cultures and the strains were identified as L. infantum zymodeme MON-28. No parasites were isolated in PBMC culture. After 12 months, a second blood sample was obtained from 18 blood donors who were positive by nested-PCR in the first extraction; nine of them remained positive. Delayed type hypersensitivity (DTH) tests on 15/67 donors (22.3%) were positive. Comparison of results obtained by ELISA, WB and DTH; ELISA, WB and nested-PCR and nested-PCR and BC culture showed a significant association (Pearson test, P < 0.05). L. infantum zyodeme MON-28 was identified in three strains isolated from asymptomatic donors, which suggests a low virulence capacity of these strains. The detection of Leishmania DNA in a high number of asymptomatic subjects supports the need to monitor it in blood donors endemic areas.

Serological screening for Leishmania infantum in asymptomatic blood donors living in an endemic area (Sicily, Italy)

“…DiVerent reports documented parasitemia in asymptomatic L. infantum-seropositive blood donors [12,13]. Several hypotheses may be proposed to explain our diVerent results: (i) the screened sample is not wide enough although it is similar to that studied by other authors in the Mediterranean area [12,13]; (ii) the antibody titer may be so low that the tests used are not able to detect it; the global sensitivity of the tests used is reported to range from 95% to 100% in an immunocompetent host [19,20], but asymptomatic subjects show a low humoral immunoresponse so that their antibody levels are under the cut-oV; (iii) ELISA and IFAT are rapid and not very expensive techniques, but they are less sensitive than western blotting, which may give positive results even if classical serological tests are negative [13].…”

“…Parasite circulation in the peripheral blood has been reported in asymptomatic Leishmania donovani and Leishmania tropica infection [6][7][8], in cured Leishmania brasiliensis infection [9][10][11] and in asymptomatic blood donors L. infantumseropositive in an area of southern France and of Balearic Islands [12,13].…”

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“…There are also indications that global warming is changing the geographical distribution of vectors which could lead to transmission in hitherto non endemic regions (Kuhn 1999, Peterson & Shaw 2003. evidence indicating that parasites persist for life (le Fichoux et al 1999, Riera et al 2004 and that due to some breakdown in the immune system disease may result at a later date (Walton et al 1973). Sand fly biting rates may vary from extremely sporadic to almost constant depending on the region and the habits of the individual can also be important risk factors (Caldas et al 2002).…”

ELISA and western blotting for the detection of Hsp70 and Hsp83 antigens of Leishmania donovani

“…Although various serologic techniques can detect active leishmaniasis when a high level of specific antibodies is present, they do not distinguish between various phases of the disease when levels of antibodies are at or near the cut-off level. Western blot analysis of whole parasite antigens is considered to be sensitive when low serum antibody titers are present (Riera et al 2004). Western blotting is not preferred in case of cutaneous leishmaniasis because antileishmanial antibodies are present in low titers.…”