The American Journal of Tropical Medicine and Hygiene - Volume 83, Issue 3, 2010

A prospective hospital-based study was undertaken to define the incidence of invasive pneumococcal disease (IPD) and circulating serotypes in Laos. Of 10,799 patients with hemocultures and 353 patients with cerebrospinal fluid samples, 0.21% and 5.4%, respectively, were positive for Streptococcus pneumoniae, giving a total of 35 IPD patients. We developed a real-time polymerase chain reaction to detect serotypes represented in the 13-valent pneumococcal vaccine. A blinded evaluation comparing serotype as defined by the Quellung reaction versus the polymerase chain reaction demonstrated 100% concordance. The most frequent serotype (n = 33 patients) was 1 (n = 6), followed by serotypes 5, 6A/B/C, 14, and 23F. Serotypes represented in the 7-valent polysaccharide-protein conjugate vaccine (PCV-7) infected 39% of patients, with 73% coverage for the PCV-10 and PCV-13 vaccines. Although the sample size is small, these data suggest that the PCV-7 vaccine may have relatively low efficacy in Laos. Further studies are urgently needed to guide pneumococcal vaccine policy in Laos.

From April 2005 to April 2006, a phase 2 malaria vaccine trial in Kenya enrolled 400 children aged 12–47 months. Each received mixed supervised and unsupervised artemether-lumefantrine for uncomplicated malaria, using a standard six-dose regimen, by weight. Children were followed for detection of parasitemia and clinical malaria. A median of two negative malaria blood films occurred during every recurrent parasitemia (RP) episode, suggesting reinfection over late recrudescence. Median time to RP after starting artemether-lumefantrine was 37 days (36–38). Of 2,020 evaluable artemether-lumefantrine treatments, there were no RPs in 99% by day 14, 71% by day 28, and 41% by day 42. By World Health Organization standards, 71% of treatment courses had adequate responses. Although recrudescence in some cannot be ruled out, our cohort had a shorter median time to RP compared with other artemether-lumefantrine treatment studies. This underscores patient counseling on completing all treatment doses for optimal protection from RP.

Clinical malaria incidence was determined over 18 months in a cohort of 553 children living in a peri-urban area near Cotonou. Three cross-sectional surveys were also carried out. Malaria incidence showed a marked seasonal distribution with two peaks: the first corresponding to the long rainy season, and the second corresponding to the overflowing of Lake Nokoue. The overall Plasmodium falciparum incidence rate was estimated at 84/1,000 person-months, and its prevalence was estimated at over 40% in the two first surveys and 68.9% in the third survey. Multivariate analysis showed that girls and people living in closed houses had a lower risk of clinical malaria. Bed net use was associated with a lower risk of malaria infection. Conversely, children of families owing a pirogue were at higher risk of clinical malaria. Considering the high pyrethroids resistance, indoor residual spraying with either a carbamate or an organophospate insecticide may have a major impact on the malaria burden.

Parasite dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) are known target enzymes of antifolate drugs used for the treatment and prophylaxis of persons with malaria. We sequenced the Plasmodium vivax dihydrofolate reductase (pvdhfr) and dihydropteroate synthase (pvdhps) genes to examine the prevalence and extent of point mutations in isolates from malaria-endemic countries. Double mutations (S58R and S117N) or quadruple mutations (F57L/I, S58R, T61M, and S117T) in the pvdhfr gene were found in isolates from Thailand (96.4%) and Myanmar (71.4%), but in only one isolate (1.0%) from Korea, where sulfadoxine-pyrimethamine has never been used. The pvdhfr point mutations correlated strongly with the pvdhps point mutations and ranged from single to triple mutations (S382A, A383G, and A553G), among isolates from Thailand, Myanmar, and Korea. These findings suggests that the prevalence of mutations in pvdhfr and pvdhps in P. vivax isolates from different malaria-endemic countries is associated with selection pressure imposed by sulfadoxine-pyrimethamine.

Zambia national survey, administrative, health facility, and special study data were used to assess progress and impact in national malaria control between 2000 and 2008. Zambia malaria financial support expanded from US$9 million in 2003 to US$ ~40 million in 2008. High malaria prevention coverage was achieved and extended to poor and rural areas. Increasing coverage was consistent in time and location with reductions in child (age 6–59 months) parasitemia and severe anemia (53% and 68% reductions, respectively, from 2006 to 2008) and with lower post-neonatal infant and 1–4 years of age child mortality (38% and 36% reductions between 2001/2 and 2007 survey estimates). Zambia has dramatically reduced malaria transmission, disease, and child mortality burden through rapid national scale-up of effective interventions. Sustained progress toward malaria elimination will require maintaining high prevention coverage and further reducing transmission by actively searching for and treating infected people who harbor malaria parasites.

We compare, contrast, and evaluate methods to quantify genetic markers of antimalarial drug resistance. Frequency estimates should be reported along with crude prevalence. There are four main potential methods to estimate frequencies in blood samples: simple counting of single nucleotide polymorphisms (SNPs) and haplotypes in samples with multiplicity of infection (MOI) = 1; SNP counting in samples with MOI ≤ 2; SNP and haplotypes counting in samples with unambiguous genotypes; statistical inference using SNP and MOI data from all samples. Large differences between the methods became apparent when analyzing field data with high MOI. Simple counting dramatically reduced sample size and estimate precision, and we show that analysis of unambiguous samples is biased, leaving maximum likelihood or similar statistical inference as the only practical option. It is essential to account for genotyping missing minor clones; ignoring this phenomenon resulted in a 2-fold underestimation of SNPs and haplotypes present at low frequencies.

The diagnosis of malaria in biological fluids other than blood using non-invasive, rapid diagnostic techniques provides a valuable approach in case management and epidemiological studies of malaria. Rapid detection of Plasmodium falciparum lactate dehydrogenase (pLDH) in saliva samples from 130 of 144 children with microscopically confirmed P. falciparum infection was evaluated using Optimal-IT dipsticks. Genotyping of parasites was also performed in saliva and blood samples from a cohort of patients by polymerase chain reaction (PCR). The sensitivity of the dipstick in whole-blood, whole-saliva, or supernatant of spun saliva samples was 97.2%, 77.9%, and 48.4%, respectively. The sensitivity of the dipstick in whole-saliva samples was significantly higher than in supernatant of spun saliva samples (P < 0.0005). Mutant T76 allele was detectable in 60% and 57% of blood and saliva samples, respectively. This finding shows rapid detection of pLDH in patient saliva.

A prospective study was carried out in a cohort of 355 persons in a leishmaniasis-endemic village of the Patna District in Bihar, India, to determine the prevalence of asymptomatic persons and rate of progression to symptomatic visceral leishmaniasis (VL) cases. At baseline screening, 50 persons were positive for leishmaniasis by any of the three tests (rK39 strip test, direct agglutination test, and polymerase chain reaction) used. Point prevalence of asymptomatic VL was 110 per 1,000 persons and the rate of progression to symptomatic cases was 17.85 per 1,000 person-months. The incidence rate ratio of progression to symptomatic case was 3.36 (95% confidence interval [CI] = 0.75–15.01, P = 0.09) among case-contacts of VL compared with neighbors. High prevalence of asymptomatic persons and clinical VL cases and high density of Phlebotomus argentipes sand flies can lead to transmission of VL in VL-endemic areas.

This study analyzed the effectiveness of active case detection (ACD) for new visceral leishmaniasis (VL) cases. ACD detection was carried out using house to house screening in Bangladesh and India and by neighborhood screening around index cases in Nepal. The percent increase of new VL cases through ACD compared to PCD was 6.7–17.1% in India; 38.8% in Nepal; and 60% in Bangladesh. The screening effort was high in India and Bangladesh (house to house screening) compared to Nepal (index case screening). The additional cost per new VL case detected varied: $50 to $106 in India; $172 in Bangladesh; $262 in Nepal depending on the type of screening staff, transport and training costs. The estimated annual VL incidence in the ACD arm ranged from 315–383 in India; 109 in Bangladesh, and 43 per 100,000 in Nepal. The additional effort and cost rises as disease incidence declines or PCD improves.

Immunity to saliva of Phlebotomus papatasi protects against Leishmania major infection as determined by co-inoculation of parasites with salivary gland homogenates (SGHs) of this vector. These results were obtained with long-term colonized female P. papatasi. We investigated the effect of pre-immunization with SGH of long-term colonized P. papatasi against L. major infection co-inoculated with SGH of wild-caught P. papatasi. Our results showed that pre-exposure to SGH of long-term, colonized P. papatasi do not confer protection against infection with L. major co-inoculated with SGH of wild-caught P. papatasi. These preliminary results strongly suggest that the effectiveness of a vector saliva-based vaccine derived from colonized sand fly populations may be affected by inconsistent immune response after natural exposure.

Studies evaluating radiologic aspects, local complications, and structural alterations of the paranasal sinus in patients with mucosal leishmaniasis (ML) are lacking. The aim of this study was to analyze alterations of the paranasal sinuses in patients with ML by using computed tomography (CT) scans. This prospective study evaluated 26 patients in Brazil with ML from December 2008 through June 2009. All patients underwent CT scans of the paranasal sinuses. Paranasal thickening was observed in 25 patients (96%). Nasal perforation was observed in 17 patients (65%). Those patients who received re-treatment showed more abnormalities on CT scan than cured patients (P < 0.05). Complications of ML are not limited to the nasal mucosa but extend to the paranasal sinuses. Mucosal thickening, opacified air cells, bony remodeling, and bony thickening caused by inflammatory osteitis of the sinus cavity walls are CT findings suggestive of chronic sinusitis.

Trypanosoma cruzi, the causative agent of Chagas disease, is widespread in the southern United States. In addition to detection in numerous wildlife host species, cases have been diagnosed in domestic dogs and humans. In the current investigation, groups of laboratory mice [Crl:CD1 (ICR)] were inoculated with one of 18 United States T. cruzi isolates obtained from a wide host range to elucidate their infectivity, pathogenicity, and virulence. In addition, laboratory rats (SD strain) were inoculated with four isolates. Mice and rats were susceptible to infection with all strains, but no morbidity or mortality was noted, which indicates that these T. cruzi isolates from the United States had low virulence for laboratory mice and rats.

A cross-sectional study was carried out on 241 primary schoolchildren in Pahang, Malaysia to update their vitamin A status and to investigate the association of poor vitamin A status with their health and socioeconomic factors. All children were screened for intestinal parasitic infections. Blood samples were collected and vitamin A status was assessed. Socioeconomic data were collected by using pre-tested questionnaires. The results showed that 66 (27.4%) children had low serum retinol levels (< 0.70 μmol/L). Giardiasis and severe ascariasis were significantly associated with low serum retinol levels (P = 0.004 and P = 0.018, respectively). Logistic regression confirmed the significant association of giardiasis with low serum retinol (odds ratio = 2.7, 95% confidence interval = 1.3–5.5). In conclusion, vitamin A deficiency is still a public health problem in rural Malaysia. Vitamin A supplementation and treatment of intestinal parasitic infections should be distributed periodically to these children to improve their health and nutritional status.

We determined the seroprevalence of Toxoplasma gondii and associated risk factors among 963 pregnant women attending an obstetric hospital in Fortaleza, Brazil. Seroprevalences of IgG and IgM against T. gondii were 68.6% (95% confidence interval [CI] = 65.6–71.6%) and 0.5% (95% CI = 0.06–1.0%), respectively. Seroprevalence of IgG was high in women less than 25 years of age (91.7%) and in low-income women (odds Ratio [OR] = 1.40, 95% CI = 1.02–1.90). Multivariate regression analysis showed that consumption of homemade water ice (adjusted OR = 1.49, 95% CI = 1.09–2.04), vegetables washed with untreated water (adjusted OR = 1.43, 95% CI = 1.05–1.94), consumption of chicken (adjusted OR = 1.49, 95% CI = 1.12–2.0), and dog ownership (adjusted OR= 1.46, 95% CI = 1.07–1.98) were factors associated with IgG seropositivity. Young women in northeastern Brazil living under poor socioeconomic conditions are at highest risk for acquiring infection with T. gondii. Oocyst contamination of water and soil must be addressed in future prevention strategies.

We evaluated the effect of annual ivermectin (IV) distribution for onchocerciasis on the prevalence of soil transmitted helminth (STH) infections in school-aged (SAC) and preschool-aged (PAC) children by comparing children in villages that had received treatment for 13 years to those from socioeconomically similar villages in untreated areas. We enrolled 1,031 SAC and 211 PAC for Kato Katz examinations. Treated areas had a lower prevalence of Ascaris (SAC: 3% versus 12%, P < 0.0001; PAC: 3% versus 10%, P < 0.051) and Trichuris (SAC: 6% versus 10%, P = 0.012; PAC: 1% versus 8%, P = 0.019), but not hookworm (SAC: 38% versus 42%, P = 0.20; PAC: 21% versus 27%, P = 0.30). The prevalence of Ascaris or Trichuris in treated areas was below the WHO threshold for mass antihelminthic treatment (MDA), but not for hookworm. We conclude that benzimidazole MDA in IV treatment areas is indicated to effectively control hookworm.

Polymerase chain reaction (PCR) with the specific primer set amplifying 28S ribosomal DNA (rDNA) of Schistosoma japonicum was able to detect genomic DNA of S. japonicum, but not S. mansoni, at 100 fg. This procedure enabled us to detect the DNA from a single miracidium and a snail infected with one miracidium at just 1 day after infection. We compared these results with those from loop-mediated isothermal amplification (LAMP) targeting 28S rDNA and found similar results. The LAMP could amplify the specific DNA from a group of 100 normal snails mixed with one infected snail A PCR screening of infected snails from endemic regions in Anhui Province revealed schistosomal DNA even in snails found negative by microscopy. PCR and LAMP show promise for monitoring the early infection rate in snails, and they may be useful for predicting the risk of infection in the endemic places.

Knowledge of the molecular mechanisms used by Necator americanus larvae to penetrate the human skin and the vasculature would aid the development of effective vaccines against this important pathogen. In this work, the impact of N. americanus exsheathing fluid (EF) and excretory/secretory products (ES) on the endothelial barrier was examined using human umbilical vein endothelial cells (HUVEC). Cellular responses were assessed by investigating molecular changes at cell–cell junctions and by determining levels of secreted IL-6, IL-8, and vascular endothelial growth factor (VEGF) in the culture medium. It would appear that a repertoire of larval proteases caused a dose-related increase in endothelial permeability as characterized by a decrease in monolayer resistance with increased permeation of tracer-albumin. These barrier changes were associated with disruption of junctional vascular endothelial cadherin (VE-cadherin) and F-actin and an increase in endothelial secretion of IL-6 and IL-8. Our data suggest that larval proteases play an important role in negotiating the endothelium.