Introgressive Hybridization of Schistosoma haematobium Group Species in Senegal: Species Barrier Break Down between Ruminant and Human Schistosomes

The file attached is the Published/publisher’s pdf version of the article.Copyright: © 2013 Webster et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Praziquantel treatment of school children from single and mixed infection foci of intestinal and urogenital schistosomiasis along the Senegal River Basin: Monitoring treatment success and re-infection patterns.

Following major water development schemes in the 1980s, schistosomiasis has become a serious parasitic disease of children living in the Senegal River Basin. Both urogenital (Schistosoma haematobium) and intestinal (Schistosoma mansoni) schistosomiasis can be highly prevalent in school-aged children, with many individuals infected with both parasites. In order to investigate the transmission and re-infection dynamics of both parasite species, single and mixed infection foci at three villages (Nder and Temeye; S. mansoni and S. haematobium foci and Guia; S. haematobium focus) were studied. In each focus infected children were identified and selected for a 12-month study involving two treatments with praziquantel (40mg/kg) three weeks apart at the beginning of the study and again 6 months into the study. Urine and stool samples were examined for schistosome eggs before and at 6 weeks and 6 months after chemotherapy. Prevalence and intensity of infection were recorded for each child at each time point. Before treatment, in all three villages, the prevalence and intensity of infection was extremely high for both S. mansoni (79-100%) and S. haematobium (81-97%). With the first round of chemotherapy sufficient cure rates (CRs) of both species were achieved in all villages (38-96%) with high egg reduction rates (ERRs) (97-99%). The data show that high and rapid re-infection rates occur, especially for S. mansoni, within a six-month period following treatment. Re-infection must be highly linked to ecological and seasonal factors. The persistence of S. mansoni in Nder could raise concern as levels of infection intensity remain high (geometric mean intensity at baseline 653epg changed to 705epg at 12 months) after four rounds of chemotherapy. This phenomenon could be explained by extremely rapid re-infection dynamics or a sub-optimal efficacy of praziquantel against S. mansoni in this village. High intensities in mixed infections may influence disease epidemiology and control warranting further studies. The disease situation in the SRB must be monitored closely and new treatment regimes should be designed and implemented to control schistosomiasis in the school-age population

Experimental laboratory animal infections.

*<p>Hamsters were used as <i>S. haematobium</i> does not develop well in mice.</p>**<p>Genetic profiles and number of hybrid miracidia resulting from the heterospecific crosses. In total 96 miracidia from each animal cross were genetically analysed.</p><p><i>S. c</i> = <i>S. curassoni</i>, <i>S. b</i> = <i>S. bovis</i>, <i>S. h</i> = <i>S. haematobium</i>, M = male and F = female.</p

Map showing the location of the survey sites across Senegal.

<p>The survey sties are numbered in red. GPS coordinates: 1. Richard Toll = 16°27′40.71″N, 15°41′15.29″W, 2. Nder = 16°15′33.50″N, 15°53′2.13″W, 3. Linguiere = 15°23′34.33″N, 15°6′55.87″W, 4. Barkedji =  =  15°16′38.46″N, 14°51′55.48″W, 5. Tambacounda = 13°46′8.00″N, 13°40′2.00″W, 6. Kolda = 12°53′58.27″N, 14°56′39.37″W. The regions of Senegal are also shown on the map.</p

Genetic Diversity within Schistosoma haematobium: DNA Barcoding Reveals Two Distinct Groups

Webster, Bonnie L. Emery, Aiden M. Webster, Joanne P. Gouvras, Anouk Garba, Amadou Diaw, Oumar Seye, Mohmoudane M. Tchuente, Louis Albert Tchuem Simoonga, Christopher Mwanga, Joseph Lange, Charles Kariuki, Curtis Mohammed, Khalfan A. Stothard, J. Russell Rollinson, DavidBackground - Schistosomiasis in one of the most prevalent parasitic diseases, affecting millions of people and animals in developing countries. Amongst the human-infective species S. haematobium is one of the most widespread causing urogenital schistosomiasis, a major human health problem across Africa, however in terms of research this human pathogen has been severely neglected. Methodology/principal findings - To elucidate the genetic diversity of Schistosoma haematobium, a DNA 'barcoding' study was performed on parasite material collected from 41 localities representing 18 countries across Africa and the Indian Ocean Islands. Surprisingly low sequence variation was found within the mitochondrial cytochrome oxidase subunit I (cox1) and the NADH-dehydrogenase subunit 1 snad1). The 61 haplotypes found within 1978 individual samples split into two distinct groups; one (Group 1) that is predominately made up of parasites from the African mainland and the other (Group 2) that is made up of samples exclusively from the Indian Ocean Islands and the neighbouring African coastal regions. Within Group 1 there was a dominance of one particular haplotype (H1) representing 1574 (80%) of the samples analyzed. Population genetic diversity increased in samples collected from the East African coastal regions and the data suggest that there has been movement of parasites between these areas and the Indian Ocean Islands. Conclusions/significance - The high occurrence of the haplotype (H1) suggests that at some point in the recent evolutionary history of S. haematobium in Africa the population may have passed through a genetic 'bottleneck' followed by a population expansion. This study provides novel and extremely interesting insights into the population genetics of S. haematobium on a large geographic scale, which may have consequence for control and monitoring of urogenital schistosomiasis.Copyright: © 2012 Webster et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article

Neighbour-joining <i>nad</i>1 tree topology supporting the topology of the <i>cox</i>1 tree.

<p>Nodal supports for the 2 groups are marked and details of the samples representing H1, “red dot”, are shown in the sub tree. Each terminal branch is labelled with the individual haplotype codes as detailed in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001882#pntd.0001882.s001" target="_blank">Table S1</a>.</p

Neighbour-joining <i>cox</i>1 tree topology.

<p>Nodal supports for the 2 groups are marked and details of the samples representing H1, “red dot”, are shown in the sub tree. Each terminal branch is labelled with the individual haplotype codes as detailed in <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001882#pntd.0001882.s001" target="_blank">Table S1</a>.</p

Within locality <i>cox</i>1 diversity.

<p><i>n</i> = number of samples sequenced; <i>u</i> = number of unique haplotypes found within the region; <i>h</i> = haplotype diversity ± standard deviation; <b>∏</b> = nucleotide diversity.</p>*<p>Only localities where miracidial populations were collected and the data from Zanzibar <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001882#pntd.0001882-Webster2" target="_blank">[25]</a> were included.</p><p>The Genbank Accession numbers for the <i>cox</i>1 data are JQ397330–JQ397399 and for the <i>nad</i>1 data are JQ595387–595404 (see <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001882#pntd.0001882.s001" target="_blank">Table S1</a>).</p