Peri-urban visceral leishmaniasis (VL) caused by Leishmania chagasi is emerging in a new epidemiologic pattern in Brazilian cities. We studied peri-urban VL in endemic neighborhoods surrounding Natal, Brazil, identified through hospitalized individuals with VL. Clinical and environmental information obtained for 1106 members of 216 families living in endemic neighborhoods enabled us to identify 4 groups: VL: individuals with current or prior symptomatic visceral leishmaniasis (n = 135); DTH+: individuals with positive delayed-type hypersensitivity response with no history of VL (n = 390); Ab +: individuals with negative DTH response and seropositive (n = 21); DTH -: individuals with negative DTH and seronegative (n = 560). The mean +/-SD age of VL was 9.3+/-12.3 y. The gender distribution was nearly equal below age 5, but skewed toward males at higher ages. Acutely infected VL subjects had significantly lower hematocrits, neutrophils, and eosinophils than other categories. AB+ subjects also had lower eosinophil counts than others, a possible immune marker of early infection. VL was not associated with ownership of dogs or other animals, raising the question whether the reservoir differs in peri-urban settings. This new pattern of L. chagasi infection enables us to identify epidemiological and host factors underlying this emerging infectious disease.

Abstract. The sensitivity and specificity of a Leishmania chagasi recombinant K39 (rK39)-based enzyme-linked immunosorbent assay (ELISA) for visceral leishmaniasis (VL) was assessed in Natal, Brazil. Anti-rK39 antibodies were detected in 93.3% of patients with parasitologically confirmed VL (n ‫ס‬ 120) and in 33 others with clinically diagnosed disease. Anti-rK39 antibodies decreased significantly following treatment. The presence of antibodies was inversely correlated with development of a positive leishmanin skin test result. Anti-rK39 antibodies were detected in only 2.9% of asymptomatic subjects with a positive skin test result (n ‫ס‬ 168). They were not detected in healthy controls (n ‫ס‬ 30) or in persons with Chagas' disease (n ‫ס‬ 13) or active tuberculosis (n ‫ס‬ 31). Antibodies were found in only one of 13 patients with cutaneous leishmaniasis. In contrast, an ELISA using total L. chagasi promastigote antigen was sensitive, but not specific. The results indicate that the rK39-based ELISA is a sensitive and specific diagnostic test for symptomatic VL and can differentiate progressive from self-resolving infection.

Visceral leishmaniasis (VL) is endemic in large cities in Brazil, including Natal. We determined the prevalence of asymptomatic human infection with Leishmania infantum chagasi and associated environmental risks around Natal. Infection was detected by Leishmania skin test (LST) and anti-leishmanial antibodies in humans and anti-leishmanial antibodies in dogs. Amongst 345 humans, 24.6% were seropositive, and 38.6% were LST-positive. Prevalence of positive serology was similar in both sexes and across all ages. However, positive LST responses increased with age, suggesting that LST is long-lasting and cumulative. Multinomial logistic analysis showed that LST response varied with location (P = 0.007) and that males were more frequently LST-positive (P = 0.027). Indicators of lower socioeconomic status associated significantly with human infection. Furthermore, there was geographic coincidence of seropositive humans and dogs (r = 0.7926, P = 0.011). These data suggest that dog and human L. i. chagasi infection are intimately interrelated in environmental conditions associated with low income.

Visceral leishmaniasis (VL) caused by Leishmania chagasi is endemic to northeast Brazil. A positive delayed-type hypersensitivity skin test response (DTH þ ) is a marker for acquired resistance to disease, clusters in families and may be genetically controlled. Twenty-three single nucleotide polymorphisms (SNPs) were genotyped in the cytokine 5q23.3-q31.1 region IRF1-IL5-IL13-IL4-IL9-LECT2-TGFBI in 102 families (323 DTH þ ; 190 DTHÀ; 123 VL individuals) from a VL endemic region in northeast Brazil. Data from 20 SNPs were analyzed for association with DTH þ /À status and VL using family-based, stepwise conditional logistic regression analysis. Independent associations were observed between the DTH þ phenotype and markers in separate linkage disequilibrium blocks in LECT2 (OR 2.25; P ¼ 0.005; 95% CI ¼ 1.28-3.97) and TGFBI (OR 1.94; P ¼ 0.003; 95% CI ¼ 1.24-3.03). VL child/parent trios gave no evidence of association, but the DTHÀ phenotype was associated with SNP rs2070874 at IL4 (OR 3.14; P ¼ 0.006; 95% CI ¼ 1.38-7.14), and SNP rs30740 between LECT2 and TGFBI (OR 3.00; P ¼ 0.042; 95% CI ¼ 1.04-8.65). These results indicate several genes in the immune response gene cluster at 5q23.3-q31.1 influence outcomes of L. chagasi infection in this region of Brazil.

No abstract