Associations Between Helminth Infections, Plasmodium falciparum Parasite Carriage and Antibody Responses to Sexual and Asexual Stage Malarial Antigens.

Infections with helminths and Plasmodium spp. overlap in their geographical distribution. It has been postulated that helminth infections may influence malarial transmission by altering Plasmodium falciparum gametocytogenesis. This cross-sectional study assessed the effect of helminth infections on P. falciparum gametocyte carriage and on humoral immune responses to sexual stage antigens in Gabon. Schistosoma haematobium and filarial infections as well as P. falciparum asexual forms and gametocyte carriage were determined. The antibody responses measured were to sexual (Pfs230, Pfs48/45) and asexual P. falciparum antigens (AMA1, MSP1, and GLURP). A total of 287 subjects were included. The prevalence of microscopically detectable P. falciparum asexual parasites was higher in S. haematobium-infected subjects in comparison to their uninfected counterparts (47% versus 26%, P = 0.003), but this was not different when filarial infections were considered. Plasmodium falciparum gametocyte carriage was similar between Schistosoma- or filaria-infected and uninfected subjects. We observed a significant decrease of Pfs48/45 immunoglobulin G titer in S. haematobium-infected subjects (P = 0.037), whereas no difference was seen for Pfs230 antibody titer, nor for antibodies to AMA1, MSP1, or GLURP. Our findings suggest an effect of S. haematobium on antibody responses to some P. falciparum gametocyte antigens that may have consequences for transmission-blocking immunity

Pilot Malacology Surveys for the Intermediate Hosts of Schistosomiasis in Rural and Semi-Urban Areas of the Moyen-Ogooué Province, Gabon

The objective of this pilot malacological survey was to identify the snail intermediate hosts for Schistosoma haematobium in endemic rural and semi-urban areas of Gabon. Snails were collected, morphologically identified, and tested for infection by cercarial shedding. Released cercariae were morphologically identified using low-power light microscopy. A total of six species of snails were collected throughout the study area, with Bulinus truncatus, B. forskalii, and Potadoma spp. being the most predominant species collected. Only the Bulinus species were tested for infection by cercarial shedding, of which only B. truncatus shed cercariae. Some B. truncatus shed mammalian schistosome cercariae, while others shed Gymnocephalus cercariae. Our results indicate that B. truncatus appears to be a potential intermediate host of schistosomiasis in Gabon, where cases of S. haematobium, S. guineensis, and S. intercalatum infection are reported. However, it will be important to further understand the species diversity and transmission dynamics of schistosomes

Schistosoma haematobium infection morbidity, praziquantel effectiveness and reinfection rate among children and young adults in Gabon

Background: Sub-Saharan Africa carries most of the global burden of schistosomiasis. To optimize disease control and reduce morbidity, precise data are needed for control measures adapted to the local epidemiological situation. The objective of this study is to provide baseline information on schistosomiasis dynamics, including praziquantel (PZQ) treatment outcome in children and young adults living in the vicinity of Lambaréné, Gabon. Methods: Eligible volunteers were included into a prospective longitudinal study. Urine filtration technique was used to detect eggs in urine for schistosomiasis diagnosis. Subjects were treated with 60 mg of PZQ once per month for three consecutive months, and the outcome was assessed by cure rate (CR) and egg reduction rate (ERR). Results: A total of 328 volunteers were enrolled in the study with a mean (± SD) age of 12.2 ± 4.7 years-old. The female-to-male ratio was 0.99. Out of 258 participants in total, 45% had schistosomiasis during the survey and 43% presented with heavy infections. The incidences of haematuria and schistosomiasis were 0.11 and 0.17 person-years, respectively. After the first and third dose of PZQ, overall ERR of 93% and 95% were found, respectively; while the CR were 78% and 88%, respectively. Both ERR (100 vs 88%) and CR (90 vs 68%) were higher among females than males after the first dose. The CR increased for both groups after the third dose to 95% and 80%, respectively. After the first PZQ dose, ERR was higher for heavy compared to light infections (94 vs 89%), while the CR was higher for light than for heavy infections (87 vs 59%). After the third PZQ dose, ERR increased only for light infections to 99%, while CR increased to 98% and 75% for light and for heavy infections, respectively. The reinfection rate assessed at a mean of 44.6 weeks post-treatment was 25%. Conclusions: The prevalence of schistosomiasis is moderate in communities living in the vicinity of Lambaréné, where a subpopulation with a high risk of reinfection bears most of the burden of the disease. To improve schistosomiasis control in this scenario, we suggest education of these high-risk groups to seek themselves a one-year PZQ treatment. Trial registration clinicaltrials.gov Identifier NCT 02769103. Registered 11 May 2016, retrospectively registered

Epidemiology of Schistosomiasis and Soil-Transmitted Helminth Coinfections among Schoolchildren Living in Lambaréné, Gabon

Schistosomiasis is a parasitic infection highly prevalent in Central Africa where it is co-endemic with many other parasitic infections, including soil-transmitted helminths (STHs). For its optimal control, there is a need of descriptive epidemiological data for each endemic region. The objective of the present study was to determine the epidemiological situation around schistosomiasis in Lambaréné, Gabon. A cross-sectional study was conducted among schoolchildren. One urine sample per day was collected on three consecutive days for the diagnosis of schistosomiasis using a urine filtration technique. One stool sample was collected for the detection of Schistosoma spp. and STH spp. eggs using the Kato–Katz technique, and for larvae, using the coproculture technique. A total of 614 schoolchildren were included in the analysis. The overall prevalence of schistosomiasis and STH infections was 26% (159/614) and 15% (70/473), respectively. Human–freshwater contact was the main risk factor for schistosomiasis in the area (relative risk (RR) = 2.96 [2.20–4.00], P < 0.001). Hematuria (RR = 5.53 [4.30–7.10], P < 0.001) and proteinuria (RR = 2.12 [1.63–2.75], P < 0.001) as well as infection with Trichuris trichiura (RR = 1.86 [1.33–2.61], P = 0.002) and Ascaris lumbricoides (RR = 1.96 [1.19–3.21], P = 0.039) were associated with an increased risk of schistosomiasis. Trichuris trichiura was the highest prevalent STH species in the area. Our study reports a moderate prevalence for schistosomiasis with human–water contact as the main risk factor, whereas the prevalence of STH infections appears to be low. Our results stress the need for the implementation of WHO recommendations for schistosomiasis control

Association of low birth weight and polyparasitic infection during pregnancy in Lambaréné, Gabon

OBJECTIVE: To report the prevalence of polyparasitism during pregnancy in the Lambaréné region of Gabon and its association with newborn birth weight. METHOD: Pregnant women in their third trimester were recruited in a prospective study between November 2011 and March 2015. Parasite infection status was assessed microscopically in stool, urine and blood samples. Maternal demographic and obstetrical characteristics and newborns anthropometric data were collected. Multivariable logistic regression was used to assess the association between low birth weight and polyparasitism. RESULTS: 678 of 927 pregnant women were included for analysis with mean age (SD) of 25 (6.8) years. The analysis showed that 69% (468/678) were infected with at least one parasite (Plasmodium spp., Schistosoma spp., soil-transmitted helminths, filarial infections). This comprised of 38% with monoparasitism and 31% polyparasitism. The proportion of newborn babies with a weight below 2500 g (LBW) in our study was 21% (142/678). Compared to pregnant women without infection, women with monoparasitic infection had adjusted Odds Ratio confidence interval 95% CI (aOR [95%CI]) of 1.6 [0.95-2.73], those with two parasites had aOR 95%CI of 2.63 [1.51-4.62], and those with more than two parasites had aOR of 5.08 [2.5-10.38] for delivering a newborn with low birth weight. CONCLUSION: In Lambaréné, an endemic area for multiple parasite infections, there is a high prevalence of polyparasitism in pregnant women. Polyparasitism is associated with low birth weight. Therefore, there is an urgent need for active screening and treatment of parasite infections in pregnant women to assess the potential public health benefit of such interventions

<i>Schistosoma haematobium</i> effects on <i>Plasmodium falciparum</i> infection modified by soil-transmitted helminths in school-age children living in rural areas of Gabon

<div><p>Background</p><p>Malaria burden remains high in the sub-Saharan region where helminths are prevalent and where children are often infected with both types of parasites. Although the effect of helminths on malaria infection is evident, the impact of these co-infections is not clearly elucidated yet and the scarce findings are conflicting. In this study, we investigated the effect of schistosomiasis, considering soil-transmitted helminths (STH), on prevalence and incidence of <i>Plasmodium falciparum</i> infection.</p><p>Methodology</p><p>This longitudinal survey was conducted in school-age children living in two rural communities in the vicinity of Lambaréné, Gabon. Thick blood smear light microscopy, urine filtration and the Kato-Katz technique were performed to detect malaria parasites, <i>S</i>. <i>haematobium</i> eggs and, STH eggs, respectively. <i>P</i>. <i>falciparum</i> carriage was assessed at inclusion, and incidence of malaria and time to the first malaria event were recorded in correlation with Schistosoma carriage status. Stratified multivariate analysis using generalized linear model was used to assess the risk of plasmodium infection considering interaction with STH, and survival analysis to assess time to malaria.</p><p>Main findings</p><p>The overall prevalence on subject enrolment was 30%, 23% and 9% for <i>S</i>. <i>haematobium</i>, <i>P</i>. <i>falciparum</i> infections and co-infection with both parasites, respectively. Our results showed that schistosomiasis in children tends to increase the risk of plasmodium infection but a combined effect with <i>Trichuris trichiura</i> or hookworm infection clearly increase the risk (aOR = 3.9 [_95%CI: 1.7–9.2]). The incidence of malaria over time was 0.51[_95%CI: 0.45–0.57] per person-year and was higher in the Schistosoma-infected group compared to the non-infected group (0.61 <i>vs</i> 0.43, <i>p</i> = 0.02), with a significant delay of time-to first-malaria event only in children aged from 6 to 10-years-old infected with <i>Schistosoma haematobium</i>.</p><p>Conclusions</p><p>Our results suggest that STH enhance the risk for <i>P</i>. <i>falciparum</i> infection in schistosomiasis-positive children, and when infected, that schistosomiasis enhances susceptibility to developing malaria in young children but not in older children.</p></div

Potential risk factors including <i>S</i>. <i>haematobium</i> infection associated with <i>P</i>. <i>falciparum</i> infection among the 739 participants seen at baseline.

<p>Potential risk factors including <i>S</i>. <i>haematobium</i> infection associated with <i>P</i>. <i>falciparum</i> infection among the 739 participants seen at baseline.</p

Distribution of <i>P</i>. <i>falciparum</i> and <i>S</i>. <i>haematobium</i> infections among the 739 participants seen at baseline.

<p>Distribution of <i>P</i>. <i>falciparum</i> and <i>S</i>. <i>haematobium</i> infections among the 739 participants seen at baseline.</p

Depicts estimates of time to malaria after 52 weeks of follow-up.

<p>Depicted in the vertical axis the proportion of children who did not experience malaria and in the horizontal axis, the follow-up time in months. In red, children in <i>S</i>. <i>haematobium</i> non-infected group and in blue children in <i>S</i>. <i>haematobium</i> infected group. 2A) Kaplan Meier curve for time-to-first malaria case for overall study population. 2B) Kaplan Meier curve for time-to-first malaria case for children aged from 6 to 10 years old. 2C) Kaplan Meier curve for time-to-first malaria case for children aged from 11 to 16 years old.</p

Characteristics of study groups considered for longitudinal analysis regarding Schistosoma status (N = 586).

<p>Characteristics of study groups considered for longitudinal analysis regarding Schistosoma status (N = 586).</p