28 research outputs found

    Retarded Onchocerca volvulus L1 to L3 larval development in the Simulium damnosum vector after anti-wolbachial treatment of the human host

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    <p>Abstract</p> <p>Background</p> <p>The human parasite <it>Onchocerca volvulus </it>harbours <it>Wolbachia </it>endosymbionts essential for worm embryogenesis, larval development and adult survival. In this study, the development of <it>Wolbachia</it>-depleted microfilariae (first stage larvae) to infective third stage larvae (L3) in the insect vector <it>Simulium damnosum </it>was analysed.</p> <p>Methods</p> <p>Infected volunteers in Cameroon were randomly and blindly allocated into doxycycline (200 mg/day for 6 weeks) or placebo treatment groups. After treatment, blackflies were allowed to take a blood meal on the volunteers, captured and dissected for larval counting and DNA extraction for quantitative real-time PCR analysis.</p> <p>Results</p> <p>PCR results showed a clear reduction in <it>Wolbachia </it>DNA after doxycycline treatment in microfilariae from human skin biopsies with > 50% reduction at one month post-treatment, eventually reaching a reduction of > 80%. Larval stages recovered from the insect vector had similar levels of reduction of endosymbiotic bacteria. Larval recoveries were analysed longitudinally after treatment to follow the kinetics of larval development. Beginning at three months post-treatment, significantly fewer L3 were seen in the blackflies that had fed on doxycycline treated volunteers. Concomitant with this, the proportion of second stage larvae (L2) was significantly increased in this group.</p> <p>Conclusions</p> <p>Doxycycline treatment and the resulting decline of <it>Wolbachia </it>endobacteria from the microfilaria resulted in retarded development of larvae in the insect vector. Thus, anti-wolbachial treatment could have an additive effect for interrupting transmission by reducing the number of L3 that can be transmitted by blackflies.</p

    A cross-sectional survey on the prevalence of anaemia and malnutrition in primary school children in the Tiko Health District, Cameroon

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    Introduction:&nbsp;anaemia and malnutrition are common health problems in developing countries with children being the most vulnerable. They have negative impacts on human performance, growth and development, in children, both as cause and consequences of disease. Although annual mass deworming and nutrition supplement strategies have been implemented in the Tiko Health District (THD), no study has been carried out to determine the prevalence of anaemia and malnutrition. The aim of this study was therefore designed to determine the prevalence of anaemia and malnutrition among primary school children aged 5-15 years in the Tiko Health District. Methods:&nbsp;a cross-sectional study was carried out in 10 randomly selected schools in the THD and a total of 400 school children were enrolled in the study. Body weight and height were measured using an electronic weighing scale and stadiometer respectively. Anthropometric indices: Height-for-Age Z scores (HAZ), Weight-for-Age Z scores (WAZ) and Body Mass Index-for-Age Z scores (BMIAZ) were analyzed and compared with WHO Growth Reference Standards using WHO Anthroplus software. Hemoglobin levels were determined using Urit-12 Haemoglobinometer and anaemia defined as Hemoglobin (Hb) &lt; 11g/dl. Data analysis was done using the SPSS software. Results:&nbsp;the overall prevalence of malnutrition was 9.25%, prevalence of stunting 7.5% with 0.8% being severely stunted. The prevalence of wasting was 1% and underweight 0.7%. The overall prevalence of anaemia was 5%. Parents occupation and the absence of toilet were statistically associated with anaemia (P = 0.04 and P = 0.003). Age, floor type, absence of toilet and BMI were significantly associated with malnutrition (P = 0.00, P = 0.01, P = 0.02 and P = 0.003). Conclusion:&nbsp;this study revealed a low prevalence of malnutrition and anaemia which could be attributed to the deworming and nutrition supplement strategies which have been implemented

    Predicted distribution and burden of podoconiosis in Cameroon

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    Introduction: Understanding the number of cases of podoconiosis, its geographical distribution and the population at risk are crucial to estimating the burden of this disease in endemic countries. We assessed each of these using nationwide data on podoconiosis prevalence in Cameroon. Methods: We analysed data arising from two cross-sectional surveys in Cameroon. The dataset was combined with a suite of environmental and climate data and analysed within a robust statistical framework, which included machine learning-based approaches and geostatistical modelling. The environmental limits, spatial variation of predicted prevalence, population at risk and number of cases of podoconiosis were each estimated. Results: A total of 214,729 records of individuals screened for podoconiosis were gathered from 748 communities in all 10 regions of Cameroon. Of these screened individuals, 882 (0.41%; 95%CI 0.38-0.44) were living with podoconiosis. High environmental suitability for podoconiosis was predicted in three regions of Cameroon (Adamawa, North West and North). The national population living in areas environmentally suitable for podoconiosis was estimated at 5.2 (95% Confidence Interval [CI]: 4.7-5.8) million, which corresponds to 22.3% of Cameroon’s population in 2015. Countrywide, in 2015, the number of adults estimated to be suffering from podoconiosis was 41,556 (95% CI, 1,170- 240,993). Four regions (Central, Littoral, North and North West) contributed 61.2% of the cases. Conclusion: In Cameroon, podoconiosis is more widely distributed geographically than was initially expected. The number of cases and the population at risk are considerable. Expanding morbidity management and follow up of cases is of utmost necessity. Promotion of footwear use and regular foot hygiene should be at the forefront of any intervention plan

    The preparatory phase for ground larviciding implementation for onchocerciasis control in the Meme River Basin in South West Cameroon: the COUNTDOWN Consortium alternative strategy implementation trial

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    Background: Onchocerciasis control using ivermectin alone has been achieved in some endemic savannah zones of Africa. In the forest regions, the co-endemicity with Loa loa has led to severe adverse events (SAEs) resulting in poor adherence of community members to ivermectin mass drug administration (MDA). This may jeopardize achieving the interruption of transmission of onchocerciasis. Therefore, to accelerate the elimination of onchocerciasis in L. loa co-endemic zones, alternative treatment strategies (ATS) including ground larviciding may be necessary. This study aimed at identifying Simulium breeding sites, cytospecies, transmission profile, susceptibility of Simulium larvae to insecticide (temephos) and identification of some non-target aquatic fauna prior to the implementation of the COUNTDOWN consortium ground larviciding alternative strategy in the Meme River Basin in South West Cameroon. Methods: A topographic map and entomological survey were used to determine breeding sites. Larvae and adults were identified using standard identification keys. Susceptibility tests were carried out on collected larvae by exposing them to decreasing concentrations of temephos and assessing survival rates while the cytospecies were identified using cytotaxonomy. Various entomological indicators were assessed from dissected flies. Fishing was used as proxy to traps to assess some aquatic fauna at different sites. Results: Twenty-two breeding sites were prospected in the Meme River Basin with eight productive for larvae. A concentration of 0.5–0.1 mg/l temephos induced 100% larval mortality. As the concentration of temephos decreased from 0.05 to 0.0025 mg/l, mortality of larvae also decreased from 98.7 to 12%. Nine cytospecies were observed in the Meme River Basin; 13,633 flies were collected and 4033 dissected. A total of 1455 flies were parous (36.1%), 224 flies were infected (5.5%), and 64 were infective (1.6%). Aquatic fauna observed included Cyprinus spp., Clarias spp., crabs, tadpoles, beetles and larvae of damsel fly. Conclusions: Onchocerciasis is being actively transmitted within the Meme River Basin. Simulium larvae are susceptible to temephos, and nine cytospecies are present. Non-target fauna observed included fishes, frogs, crabs and insects. Besides treatment with ivermectin, vector control through ground larviciding may be a complementary strategy to accelerate onchocerciasis elimination in the study area

    Impact of repeated mass ivermectin administration using a community directed approach on L. loa infection in Chrysops silacea of the rain forest and forest savanna of Cameroon

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    Loiasis is an endemic filarial infection in the rainforest zone of West and Central Africa. Repeated annual community-directed treatment with ivermectin (CDTI) delivered for several years to control onchocerciasis has been shown to reduce the prevalence and intensity of Loiasis in some co-endemic areas. However, the impact of these multiple rounds of CDTI on entomological indicators of loiasis transmission is not known, and was therefore assessed in this study in areas with contrasting histories of CDTI. The study was conducted in the East, North-west and South-west 1 CDTI project sites of Cameroon. Two communities per CDTI project were selected for fly collection and dissection. Ivermectin treatment coverage was documented in these areas, and this was correlated to infection and infective rates. A total of 7029 female were collected from 6 communities of the 3 CDTI projects (East, North-west, and South-west 1) and from 2 communities in a non-CDTI district (East). biting densities and parous rates were significantly reduced in the North-west and South-west sites post-CDTI, while in the East, biting densities were similar in non-CDTI and CDTI sites, with higher parous rates observed in the non-CDTI site. Infection and infective rates in the East non-CDTI site were 4.4% and 1.8% respectively, as compared to 3.3% and 1.3% in the CDTI site after 10 ivermectin rounds (there were no baseline data for the latter). In the North-west site, significant reductions in infection and infective rates from 10.2% and 4.2% respectively, to 3.5% and 1.2 (after 9 rounds of ivermectin treatment), were recorded following CDTI. In the South-west, infection rate significantly increased from 1.74% to 2.8% and infective rate remained statistically unchanged after 14 rounds of CDTI (0.45% - 0.40%). Similar trends in Mean Head L3 were observed except in the East site where this indicator was similar in both CDTI and control sites. Only in the North-west site did monthly transmission potentials decrease significantly. This study demonstrated that the impact of repeated annual treatment with ivermectin for the control of onchocerciasis using community directed delivery approach on the entomological indicators of loiasis varies with bioecological zones. Community directed treatment with ivermectin induced a significant reduction in the entomological indicators of loiasis in the North-West project site which lies in forest savanna area. A non-significant decrease was observed in the East project site and in contrast, a significant increase was observed in the South-West 1 project site which both lies in the rainforest zones. [Abstract copyright: © 2024 Published by Elsevier Ltd on behalf of World Federation of Parasitologists.

    The Mbam drainage system and onchocerciasis transmission post ivermectin mass drug administration (MDA) campaign, Cameroon

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    Background The impact of large scale Mass Drug Adminstration (MDA) of ivermectin on active onchocerciasis transmission by Simulium damnosum, which transmits the parasite O. volvulus is of great importance for onchocerciasis control programmes. We investigated in the Mbam river system area, the impact of MDA of ivermectin on entomological indices and also verify if there are river system factors that could have favoured the transmission of onchocerciasis in this area and contribute to the persistence of disease. We compared three independent techniques to detect Onchocerca larvae in blackflies and also analyzed the river system within 9 months post-MDA of ivermectin. Method Simulium flies were captured before and after 1, 3, 6 and 9months of ivermectin-MDA. The biting rate was determined and 41% of the flies dissected while the rest were grouped into pools of 100 flies for DNA extraction. The extracted DNA was then subjected to O-150 LAMP and real-time PCR for the detection of infection by Onchocerca species using pool screening. The river system was analysed and the water discharge compared between rainy and dry seasons. Principal findings We used human landing collection method (previously called human bait) to collect 22,274 adult female Simulium flies from Mbam River System. Of this number, 9,134 were dissected while 129 pools constituted for molecular screening. Overall biting and parous rates of 1113 flies/man/day and 24.7%, respectively, were observed. All diagnostic techniques detected similar rates of O. volvulus infection (P = 0.9252) and infectivity (P = 0.4825) at all monitoring time points. Onchocerca ochengi larvae were only detected in 2 of the 129 pools. Analysis of the river drainage revealed two hydroelectric dams constructed on the tributaries of the Mbam river were the key contributing factor to the high-water discharge during both rainy and dry seasons. Conclusion Results from fly dissection (Microscopy), real-time PCR and LAMP revealed the same trends pre- and post-MDA. The infection rate with animal Onchocerca sp was exceptionally low. The dense river system generate important breeding sites that govern the abundance of Simulium during both dry and rainy seasons
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