Visceral Leishmaniasis In Urban Areas: The Issue Of Cross Reactivity Among Serological Tests

Abstract

INTRODUCTION: Urbanization of Trypanosoma cruzi and Leishmania infantum have increased in Latin America. This has result in an increased risk of infections to a large population. There is mandatory blood screening for T. cruzi infection, but there is none for L. infantum. MANUSCRIPT 1: Evaluation of Leishmania infantum infection in humans using commercial Trypanosoma cruzi assay: the importance of assessing cross-reaction BACKGROUND: L. infantum and T. cruzi share many common epitopes, with cross-reaction between serological assays. OBJECTIVES: To evaluate the sensitivity of a commercial T. cruzi ELISA assay for diagnosing L. infantum infection. METHODS: A total of 573 subjects from an endemic area of visceral leishmaniasis in Brazil were studied. Of those, 350 were symptomatic visceral leishmania patients (Symp VL); 87 were recovered VL individuals (Rec VL), and 96 were healthy household contacts of a VL case (HHC). Leishmania infection was estimated by a commercial T. cruzi (CHAGAS III) assay and soluble Leishmania antigens (SLA) ELISA, PCR and skin delayed type hypersensitivity responses (DTH). RESULTS: The sensitivity of the T. cruzi assay to ascertain Symp VL was 76% and its specificity was 91.7%. There was a positive correlation of both the T. cruzi and SLA ELISA assays with the level of anti-Leishmania antibodies (r=0.487, p<0.0001). The response was higher for Symp VL in both the T. cruzi (OR 39.1; p<0.0001) and the SLA (OR=41.5; p<0.0001) relative to HHC assays. There was an inverse relationship between presence of antibodies and DTH response: 88.2% of people who were DTH positive were T. cruzi negative and 53.9% who were DTH negative were T. cruzi positive (p<0.0001). CONCLUSIONS: The commercial T. cruzi assay (CHAGAS III) is sensitive for detecting L. infantum infection. The positivity of the test correlated with the level of anti-Leishmania antibodies. MANUSCRIPT 2: SEROLOGICAL SURVEY OF LEISHMANIA INFECTION IN BLOOD DONORS FROM AN ENDEMIC AREA OF VISCERAL LEISHMANIASIS IN BRAZIL BACKGROUND. Asymptomatic Leishmania infection has increased in urban areas of Brazil, which could pose a risk of Leishmania transmission through blood transfusion or organ transplantation. OBJECTIVES: To determine the prevalence of Leishmania infantum infections in blood donors of an endemic area for visceral leishmaniasis in Brazil. METHODS. A cross-sectional study was performed, with weekly recruitment of volunteers from February 2014 to January 2015. A total of 1556 participants who were donating blood in Natal, Brazil were recruited. Participants answered a questionnaire related to exposure to Leishmania. Results of their blood screening were analyzed. Blood samples were tested for Leishmania infection using a soluble Leishmania antigens (SLA) ELISA assay. Likelihood Ratio Chi-Square test evaluated the association between categorical variables. Simple and multiple regression models evaluated the effect of covariates and factors on Leishmania response. The results of the SLA ELISA were log transformed and ratio obtained, considering the cutoff value for each plate. RESULTS: A total of 51,463 people donated blood to public blood banks in 2014 and of those, 1554 (3%) were recruited. The majority of donors were males (82.4%) and married (51.8%). The literacy rate was high with 68% of the participants having completed high school. The mean body mass index for males and females were, respectively, 27.96 and 27.99 kg/m2. The seroprevalence of T. cruzi and Leishmania were 0.19% and 2.5%. Leishmania was isolated from one of the samples cultured (600). CONCLUSIONS. There is risk of Leishmania transmission through the blood supply. Close monitoring of blood recipients is warranted, principally in those with some type of immunosuppression. T. cruzi ELISA assay can identify a subgroup of L. infantum contaminated blood, but does not exclude all positive samples.