Spatio-temporal analysis of small-area intestinal parasites infections in Ghana

Preliminary Screening for the Anthelmintic Activity of Millettia zechiana Harms and Its Modifying Effect on Albendazole

Helminthic infections affect a greater proportion of the world's population. This study determined the anthelmintic activity of Millettia zechiana and its modifying effect on albendazole. Powdered leaves of M. zechiana were successively extracted with petroleum ether, ethyl acetate, and ethanol. The anthelmintic potential of the M. zechiana leaf extracts and the modifying effects of the extracts on albendazole were determined on Pheretima posthuma. Phytochemical and gas chromatography-mass spectroscopy (GC-MS) analyses were performed to determine the chemical composition of each extract. The plant extracts of M. zechiana had few or all phytoconstituents such as tannins, saponins, flavonoids, glycosides, terpenoids, phytosterols, and alkaloids present. The IC50 obtained for albendazole, petroleum ether, ethyl acetate, and ethanol extracts for paralysis time were 0.936, 1.722, 1.283, and 1.348 mg/mL, respectively. The IC50 obtained for albendazole and the ethanol extract for death time were 4.638 and 4.988 mg/mL. The ethanol extract at 10 and 5 mg/mL caused death in the worms after 152.5 ± 8.66 minutes and 304.8 ± 7.27 minutes of exposure, respectively. Ethanol, ethyl acetate, and petroleum ether extracts of M. zechiana significantly modified the activity of albendazole at concentrations of 2.5 and 1.25 mg/mL (P < 0.0001). The ethanol extract which exhibited the best anthelminthic activity was fractionated through column chromatography, and five (5) fractions were obtained. Fractions 1, 2, 4, and 5 had the best paralytic activities against the worms. Fractions 1 and 2 demonstrated better helminthicidal activity than albendazole, which had an IC50 of 3.915. The GC-MS analysis of the ethanol, ethyl acetate, and petroleum ether extracts showed the presence of 10, 10, and 37 compounds, respectively, with 9-octadecenamide, (Z)-, n-hexadecanoic acid, oleic acid, and some aromatic compounds being the most predominant. The results obtained indicate that M. zechiana leaf extract possesses anthelmintic activity.

Evolution of spatial disease clusters via a Bayesian space-time variability modelling

This study proposes to use exceedance posterior probabilities of a space-time random-effects model to study the temporal dynamics of clusters. The local time trends specified for each area is further smoothed over space. We modelled the common spatial and the space-varying temporal trend using a multivariate Markov Random field to incorporate within-area correlations. We estimate the model parameters within a fully Bayesian framework. The exceedance posterior probabilities are further used to classify the common spatial trend into hot-spots, cold-spots, and neutral-spots. The local time trends are classified into increasing, decreasing, and stable trends. The results is a 3×3 table depicting the time trends within clusters. As a demonstration, we apply the proposed methodology to study the evolution of spatial clustering of intestinal parasite infections in Ghana. We find the methodology presented in this paper applicable and extendable to other or multiple tropical diseases which may have different space-time conceptualizations.

Intestinal Helminth Infections in Ghanaian Children from the Ashanti Region between 2007 and 2008—A Retrospective Cross-Sectional Real-Time PCR-Based Assessment

In spite of ongoing eradication programs, helminth infections are still a medical issue in Ghana. For follow-up assessments on the decline of regional helminth infections, historic baseline prevalence values obtained with standardized diagnostic procedures can be helpful. In this retrospective cross-sectional study, real-time PCR targeting the nematodes Ancylostoma spp. (ITS2), Ascaris lumbricoides (ITS1), Enterobius vermicularis (ITS1), Necator americanus (ITS2), Strongyloides stercoralis (18S rRNA) and Trichuris trichiura (18S rRNA), the trematodes Schistosoma spp. (ITS2) as well as the cestodes Hymenolepis nana (ITS1), Taenia saginata (ITS1) and Taenia solium (ITS1) was applied with 2046 DNA eluates from stool samples of Ghanaian children from the Ashanti region collected between 2007 and 2008 in order to retrospectively define prevalence values. The overall prevalence was low with 3.8% (n = 77) and only 0.1% (n = 2) double infections with helminths were recorded. The three most frequently detected enteric helminth species comprised 2% S. stercoralis (n = 41), 0.8% H. nana (n = 16), and 0.7% N. americanus (n = 14), while only sporadic infection events were recorded for other helminth species comprising 0.1% E. vermicularis (n = 2), 0.1% Schistosoma spp. (n = 2), 0.1% T. saginata (n = 1) and 0.1% T. trichiura (n = 1). A. lumbricoides, Ancylostoma spp. and T. solium were not detected at all. In conclusion, the retrospective assessment suggests a low prevalence of enteric helminth infections in Ghanaian children from the Ashanti Region within the assessment period between 2007 and 2008.

Environmental influence on <em>Triatoma vitticeps</em> occurrence and <em>Trypanosoma cruzi</em> infection in the Atlantic Forest of south-eastern Brazil

Trypanosoma cruzi requires a triatomine insect vector for its life cycle, which can be complex in different enzootic scenarios, one of which is the unique transmission network in the Atlantic Forest of south-eastern Brazil. In Espírito Santo (ES) State, highly infected Triatoma vitticeps are frequently reported invading domiciles. However, triatomines were not found colonizing residences and mammals in the surrounding areas did not present T. cruzi infection. To date, the biotic and abiotic variables that modulate T. vitticeps occurrence and T. cruzi infection in ES State are still unknown. The aim of this study was to identify the environmental variables that modulate their occurrence. Local thematic maps were generated for two response variables: T. vitticeps occurrence and T. cruzi infection. The following explanatory variables were tested: climate (temperature, relative air humidity and rainfall), altitude elevation, mammalian species richness as well as soil and vegetation types. Spatiotemporal distribution patterns and correlation levels between response and explanatory variables were assessed through spatial statistics and map algebra modelling. The central and southern mesoregions presented higher T. vitticeps and T. cruzi distributions and can be considered transmission hotspots. The explanatory variables that can explain these phenomena were relative air humidity, average temperature, soil type, altitude elevation and mammalian species richness. Algebra map modelling demonstrated that central and southern mesoregions presented the environmental conditions needed for T. vitticeps occurrence and T. cruzi infection. The consideration of environmental variables is essential for understanding the T. cruzi transmission cycle. Cartographic and statistical methodologies used in parasitology have been demonstrated to be reliable and enlightening tools that should be incorporated routinely to expand the understanding of vector-borne parasite transmission.

Asymptomatic Intestinal Parasitic Infestations among Children Under Five Years in Selected Communities in the Ho Municipality, Ghana

Background

The study investigated intestinal parasitic infestations (IPIs) and possible risk factors associated with asymptomatic children under five (5) years in five (5) selected communities in the Ho Municipality.

Methods

The study design was cross- sectional, with a simple random sampling technique involving 150 asymptomatic children under 5 years from 5 selected communities (Klave, Hoe, Freetown, Dave and Godokpe) in the Ho Municipality. A questionnaire was used to obtain socio-demographics and other relevant parameters. Direct wet preparation, formol-ether concentration and Modified ZN staining techniques were used for the identification of intestinal parasites from participants' stool samples. The Fisher's exact test and binary logistic regression analysis were used to determine the difference in IPIs proportions and assess the risk factors associated with IPIs respectively.

Results

The overall IPIs cases was 14% (21/150). Cryptosporidium spp was most predominant [5.3% (8/150)], followed by Entamoeba spp [3.3% (5/150)], Cyclospora cayetenensis [2.7% (4/150)], Ascaris lumbricoides [1.3% (2/150)], Giardia lamblia [0.7% (1/150)] and Strongyloides stercoralis [0.7% (1/150)]. Children in rural communities (23.4%) recorded significantly higher case rate compared to those in urban communities (9.8%0), (p=0.04). Lower educational attainment of mother [OR=0.55, 95% CI (0.37 – 0.83), p-value = 0.015] and residence in rural communities [OR = 0.53, 95% CI (0.33–0.88)], p-value = 0.025] were significantly associated with IPIs.

Conclusion

Asymptomatic IPIs are quite prevalent among children under 5 years in the Ho Municipality. The study thus recommends active sensitization programs for parents/guardians on preventive measures and school health programs should be instituted in rural communities.

Poisson-Gamma Mixture Spatially Varying Coefficient Modeling of Small-Area Intestinal Parasites Infection

Understanding the spatially varying effects of demographic factors on the spatio-temporal variation of intestinal parasites infections is important for public health intervention and monitoring. This paper presents a hierarchical Bayesian spatially varying coefficient model to evaluate the effects demographic factors on intestinal parasites morbidities in Ghana. The modeling relied on morbidity data collected by the District Health Information Management Systems. We developed Poisson and Poisson-gamma spatially varying coefficient models. We used the demographic factors, unsafe drinking water, unsafe toilet, and unsafe liquid waste disposal as model covariates. The models were fitted using the integrated nested Laplace approximations (INLA). The overall risk of intestinal parasites infection was estimated to be 10.9 per 100 people with a wide spatial variation in the district-specific posterior risk estimates. Substantial spatial variation of increasing multiplicative effects of unsafe drinking water, unsafe toilet, and unsafe liquid waste disposal occurs on the variation of intestinal parasites risk. The structured residual spatial variation widely dominates the unstructured component, suggesting that the unaccounted-for risk factors are spatially continuous in nature. The study concludes that both the spatial distribution of the posterior risk and the associated exceedance probability maps are essential for monitoring and control of intestinal parasites.