Low prevalence of Leishmania donovani infection among the blood donors in kala-azar endemic areas of Bangladesh.

BACKGROUND: Visceral leishmaniasis (VL) is a major public health problem in Bangladesh with the highest disease burden in the Mymensingh District. The disease is transmitted by sand fly bites, but it may also be transmitted through blood transfusions. No information is available about the prevalence of Leishmania infection among blood donors in Bangladesh; therefore we aimed to investigate this question. METHODS: The study was carried out in the Blood Transfusion Department of Mymensingh Medical College Hospital. One thousand one hundred and ninety five adult healthy blood donors attending in this department were enrolled in the study from August 2010 to April 2011. After obtaining written consent, socio-demographic data and a detailed health history were collected. The medical officer in the unit performed a complete physical examination to exclude any acute or chronic diseases, which was followed by sero-diagnosis for exposure to Leishmania by rK39 strip test using finger prick blood. Blood donors with a positive rK39 strip test underwent a PCR test for detection of leishmania DNA in their peripheral blood buffy coat. RESULTS: Eighty two percent of enrolled blood donors were male (n=985) and 18% (n=210) were female. The mean age of blood donors was 27 years (SD, 7.95 years). The majority of donors were literate and had mid-to-higher socioeconomic condition reflected by household conditions reported by the subject. Only 2.6% had a family member with VL in the past. Three blood donors were positive for leishmania infection by rK39 strip test (0.3%, 95%CI, 0.05%-0.73%). None of these 3 had active leishmania infection as demonstrated by PCR analysis. During six months of follow up, neither rK39 positive (n=3) nor rK39 negative (n=1192) donors developed VL. CONCLUSION: The prevalence of Leishmania donovani infection among blood donors attending the Blood Transfusion Department of Mymensingh Medical College Hospital was very low. Therefore the chance for transmission of VL through blood transfusion is negligible. We believe that the National VL Elimination Program does not need set up routine screening for Leishmania donovani infection in blood transfusion departments located in VL endemic areas of Bangladesh.

Peripheral blood buffy coat smear: a promising tool for diagnosis of visceral leishmaniasis.

Confirmative diagnosis of visceral leishmaniasis (VL) is still a challenge at the primary health care facilities in most of the rural areas of endemicity in the Indian subcontinent. Conventional methods for parasitological confirmation are risky and require skilled personnel, and hence they are unavailable to the poor people in the regions of endemicity. Buffy coat smear microscopy, as a minimally invasive, simple alternative for the parasitological diagnosis of VL, was evaluated in this prospective study. One hundred twelve VL patients were enrolled in this study. The buffy coat was separated from peripheral blood of all enrolled subjects using Histopaque-1119 solution. Leishman-stained buffy coat smears were examined for Leishmania donovani bodies, and buffy coat was also utilized for detection of parasite DNA by Leishmania nested PCR (LnPCR) for all cases. Concomitant splenic smears could be examined for L. donovani bodies in 66 cases, and the parasite load was graded on a scale of 1+ to 6+ for L. donovani-positive smears. All splenic smear-positive cases were also found to be positive by LnPCR. Of 112 enrolled VL cases, 103 (92%) were found to be positive for L. donovani bodies in buffy coat smear microscopy, which is promising as a confirmative diagnosis tool. We have also found a significant association of the buffy coat smear positivity with parasitic burden in the spleen smear. In this preliminary observation in Bangladesh, buffy coat smear microscopy has been found to be very simple, minimally invasive, and risk-free method of parasitological diagnosis of VL with a good diagnostic accuracy and potential for field use.

Comparison of PCR-based diagnoses for visceral leishmaniasis in Bangladesh.

The diagnosis of visceral leishmaniasis (VL) is performed using multiple methods encompassing parasitological, serological and nucleic acid-based diagnostic tools, each method with its own unique advantages and disadvantages. Conventional parasitological methods are risky for the patient and require skilled personnel to collect specimens from spleen or bone marrow, and hence they are not generally available in impoverished areas. Polymerase chain reaction (PCR) has been validated as an excellent alternative to microscopy in terms of sensitivity and specificity. Here, we evaluate four different PCR assays targeting ITS1, ITS2, mini-exon and small subunit-rRNA (SSUrRNA) using DNA extracted from peripheral blood buffy coat in order to avoid more invasive processes. A total of 61 VL patients and 75 non-VL infected control individuals were enrolled. The VL patients were confirmed to be positive for Leishmania amastigotes in splenic smears by microscopy. Sensitivities of the PCR targeting ITS1, ITS2, SSUrRNA and mini-exon were 96.7%, 91.8%, 88.5% and 34.4%, respectively, while the specificity was 98.7% for all methods. Nested PCR for ITS1 resulted in 100% sensitivity. The efficacy of each PCR was evaluated with various Leishmania amastigote parasite loads in each spleen smear, graded from 1+ to 5+. The PCR targeting ITS1 showed 100% sensitivity for the detection of Leishmania donovani in all samples from grades ≥3, ≥4, and ≥5, respectively. The restriction fragment length polymorphism observed in ITS1 amplicons digested by HaeIII classified the parasite into L. donovani complex. The ITS1 PCR was found to be equal to conventional, but very invasive and risky parasitological diagnoses and superior to other PCR based methods in sensitivity and examination of genetic heterogeneity. We recommend the PCR targeting ITS1 using peripheral blood buffy coat DNA as an alternate, less invasive diagnostic choice for the confirmation of L. donovani infection.

Diagnostic accuracy of loop-mediated isothermal amplification (LAMP) for detection of Leishmania DNA in buffy coat from visceral leishmaniasis patients.

BACKGROUND: Visceral leishmaniasis (VL) remains as one of the most neglected tropical diseases with over 60% of the world's total VL cases occurring in the Indian subcontinent. Due to the invasive risky procedure and technical expertise required in the classical parasitological diagnosis, the goal of the VL experts has been to develop noninvasive procedure(s) applicable in the field settings. Several serological and molecular biological approaches have been developed over the last decades, but only a few are applicable in field settings that can be performed with relative ease. Recently, loop-mediated isothermal amplification (LAMP) has emerged as a novel nucleic acid amplification method for diagnosis of VL. In this study, we have evaluated the LAMP assay using buffy coat DNA samples from VL patients in Bangladesh and compared its performance with leishmania nested PCR (Ln-PCR), an established molecular method with very high diagnostic indices. METHODS: Seventy five (75) parasitologically confirmed VL patients by spleen smear microcopy and 101 controls (endemic healthy controls -25, non-endemic healthy control-26, Tuberculosis-25 and other diseases-25) were enrolled in this study. LAMP assay was carried out using a set of four primers targeting L. donovani kinetoplast minicircle DNA under isothermal (62 °C) conditions in a heat block. For Ln-PCR, we used primers targeting the parasite's small-subunit rRNA region. RESULTS: LAMP assay was found to be positive in 68 of 75 confirmed VL cases, and revealed its diagnostic sensitivity of 90.7% (95.84-81.14, 95% CI), whereas all controls were negative by LAMP assay, indicating a specificity of 100% (100-95.43, 95% CI). The Ln-PCR yielded a sensitivity of 96% (98.96-87.97, 95% CI) and a specificity of 100% (100-95.43, 95% CI). CONCLUSION: High diagnostic sensitivity and excellent specificity were observed in this first report of LAMP diagnostic evaluation from Bangladesh. Considering its many fold advantages over conventional PCR and potential to be used as a simple and rapid test in the VL endemic areas of the Indian subcontinent, our findings are encouraging, but further evaluation of LAMP is needed.