Field trial of a vaccine against New World cutaneous leishmaniasis in an at-risk child population: safety, immunogenicity, and efficacy during the first 12 months of follow-up

The safety, immunogenicity, and efficacy of a vaccine against cutaneous leishmaniasis in rural Ecuadorian children was assessed in a randomized, controlled, double-blinded study. Vaccine group subjects received 2 intradermal doses of a whole, killed promastigote vaccine cocktail plus bacille Calmette-Guérin (BCG) adjuvant. Control subjects got 2 doses of BCG only. The subjects who received both vaccination doses, 438 in the vaccine group (79.3%) and 406 in the control group (83.4%), were followed for 12 months. No serious adverse side effects were identified in either group. Significantly more vaccine group subjects than controls converted to a positive Montenegro skin test (85.1% vs. 20.1%; chi2 = 279; P < .001). The incidence of cutaneous leishmaniasis was significantly reduced in the vaccine compared with the control group (2.1% vs. 7.6%; chi2 = 8.95; P < .003). The protective efficacy of the vaccine was 72.9% (95% confidence interval = 36.1%-88.5%).

The epidemiology of cutaneous leishmaniasis in subtropical Ecuador

An epidemiologic survey (n = 466) was conducted in an area of subtropical rainforest in north-west Ecuador with the following objectives: (1) to determine the prevalence of cutaneous leishmaniasis (CL), (2) to identify the Leishmania species causing human disease, (3) to investigate the major clinical manifestations of leishmaniasis, (4) to study cellular and humoral immune response indicators associated with disease status and (5) to identify risk factors for CL. Fourteen percent of subjects had parasitologically confirmed CL; 33% had evidence of prior disease. However, 17.2% of subjects with a negative CL clinical history presented with a positive Montenegro skin test (MST), indicating the possibility of subclinical infection. The species isolated from subject lesions were L. guyanensis (63%), L. panamensis (33%), and L. brazilensis (4%). Mean specific anti-Leishmania IgG and IgM OD serum levels were highest in subjects diagnosed with current CL, followed by those with prior CL, and were lowest in healthy subjects, respectively (0.56 +/- 0.27 vs 0.33 +/- 0.2 vs 0.22 +/- 0.14; F-ratio = 74; P < 0.00001) and (665 +/- 270 vs 481 +/- 220 vs 301 +/- 128.5; F-ratio = 37; P < 0.00001). Likewise, subjects with present CL had measurably higher MST reactions (13 +/- 6.7 mm) than those with prior CL (10.9 +/- 7.8 mm) or healthy individuals (2.4 +/- 2.5 mm; F-ratio = 106; P < 0.00001). Serum concentrations of IgG were predicted by lesion number (t = 2.5; P = 0.018), size (t = 3.7; P = 0.0006), and duration (t = 3.5; P = 0.0013). Furthermore, the MST induration size increased as a function of lesion number (t = 3.0; P = 0.005) and size (t = 3.4; P = 0.022). Subject age and sex did not predict serum IgG or IgM concentrations or MST reactions in the 3 disease groups. Although no sex differences were found with respect to clinical characteristics, children < or = 12 years of age were almost 3 times more likely to have CL lesions or scars located on the face and head area compared to adults (OR = 2.75; 95% CI = 1.4-5.6, P = 0.004). The risk factors associated with disease included age under 5 years (AOR = 1.5; 95% CI = 0.48-2.35), male gender in adults (AOR = 2.8; 95% CI = 1.1-7.8), and wood and/or cane exterior house walls (AOR = 1.8; 95% CI = 1.4-2.5). In contrast, electric home lighting was associated with decreased risk (AOR = 0.7; 95% CI = 0.4-2.3). The results suggest that it may be possible to modify a portion of the risk of CL by making changes in the housing environment which may help to reduce the amount of human-vector contact.

Nutritional status and cutaneous leishmaniasis in rural Ecuadorian children

The relationship between nutritional status and cutaneous leishmaniasis (CL) was evaluated in 230 children living in a rural subtropical rainforest in Northwest Ecuador. One-third of the subjects had evidence of either current (13 per cent) or past CL infection (21 per cent). Subjects with current (4.71 +/- 0.44 mg) or previous disease (4.29 +/- 0.35 mg) had lower mean daily dietary iron intakes than non-infected children (5.45 +/- 0.2 mg; chi 2 = 0.048), but not energy, protein, or other micronutrients. The low dietary iron intake data was corroborated by the reduced mean haemoglobin values observed in children with current (11.7 +/- 0.3 mg/dL) or past infection (11.3 +/- 0.2 mg/dL) compared to non-infected subjects (12.7 +/- 0.15 mg/dL; F-ratio = 17.0, P < 0.0001). Mean hematocrit values were also lower in the two infected groups (37.4 +/- 0.9 per cent and 37.4 +/- 0.6 per cent v. 39.5 +/- 0.5 per cent; F-ratio = 4.23, P = 0.0175). Furthermore, they were more likely to suffer from iron-deficiency anaemia than their non-infected counterparts (chi 2 = 4.64, P = 0.03). However, the children with active disease accounted for most of the excess risk for anemia (Fisher's exact test P = 0.009; OR = 10.0, exact 95 per cent CI = 1.37-111.8). Finally, growth stunting (< -2SD height-for-age) was more common in subjects with current (54 per cent) or past infection (51 per cent) compared to those without CL history (31 per cent; chi 2 = 8.03, P = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)