1
|
Hedtke SM, Post RJ, Feleke SM, Gebretsadik FS, Boakye DA, Krueger A, Grant WN, Wilding CS. Cytotaxonomic characterization and estimation of migration patterns of onchocerciasis vectors (Simulium damnosum sensu lato) in northwestern Ethiopia based on RADSeq data. PLoS Negl Trop Dis 2024; 18:e0011868. [PMID: 38175836 DOI: 10.1371/journal.pntd.0011868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 01/17/2024] [Accepted: 12/17/2023] [Indexed: 01/06/2024] Open
Abstract
BACKGROUND While much progress has been made in the control and elimination of onchocerciasis across Africa, the extent to which vector migration might confound progress towards elimination or result in re-establishment of endemism in areas where transmission has been eliminated remains unclear. In Northern Ethiopia, Metema and Metekel-two foci located near the Sudan border-exhibit continuing transmission. While progress towards elimination has been faster in Metema, there remains a problematic hotspot of transmission. Whether migration from Metekel contributes to this is currently unknown. METHODOLOGY/PRINCIPLE FINDINGS To assess the role of vector migration from Metekel into Metema, we present a population genomics study of 151 adult female vectors using 47,638 RADseq markers and mtDNA CoI sequencing. From additional cytotaxonomy data we identified a new cytoform in Metema, closely related to S. damnosum s.str, here called the Gondar form. RADseq data strongly indicate the existence of two distinctly differentiated clusters within S. damnosum s.l.: one genotypic cluster found only in Metema, and the second found predominantly in Metekel. Because blackflies from both clusters were found in sympatry (in all four collection sites in Metema), but hybrid genotypes were not detected, there may be reproductive barriers preventing interbreeding. The dominant genotype in Metema was not found in Metekel while the dominant genotype in Metekel was found in Metema, indicating that (at the time of sampling) migration is primarily unidirectional, with flies moving from Metekel to Metema. There was strong differentiation between clusters but little genetic differentiation within clusters, suggesting migration and gene flow of flies within the same genetic cluster are sufficient to prevent genetic divergence between sites. CONCLUSIONS/SIGNIFICANCE Our results confirm that Metekel and Metema represent different transmission foci, but also indicate a northward movement of vectors between foci that may have epidemiological importance, although its significance requires further study.
Collapse
Affiliation(s)
- Shannon M Hedtke
- Department of Environment and Genetics, School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, Victoria, Australia
| | - Rory J Post
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
- Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | - Fikre Seife Gebretsadik
- Neglected Tropical Disease Prevention and Control Program, Federal Ministry of Health, Addis Ababa, Ethiopia
| | - Daniel A Boakye
- Parasitology Department, Noguchi Memorial Institute for Medical Research, Accra, Ghana
| | - Andreas Krueger
- Military Hospital Hamburg, Department Tropical Medicine, Hamburg, Germany
| | - Warwick N Grant
- Department of Environment and Genetics, School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, Victoria, Australia
| | - Craig S Wilding
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| |
Collapse
|
2
|
Ahmed A, Elbashir A, Mohamed AA, Alim AA, Mubarak A, Abdelrahman D, Mohammed E, Mohamed NS, Elaagip AH, Zarroug IMA, Mounkaila N, Tahir H. Socioeconomic impacts of elimination of onchocerciasis in Abu-Hamed focus, northern Sudan: lessons after elimination. BMC Res Notes 2020; 13:256. [PMID: 32456708 PMCID: PMC7249366 DOI: 10.1186/s13104-020-05101-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Accepted: 05/20/2020] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVES Onchocerciasis is one of the most devastating neglected tropical diseases and it is mostly prevalent in Africa. The disease has important heavy social and economic burdens on the infected populations including low productivity, unemployment, social isolation, and stigma. A cross-sectional study was implemented using a well-established questionnaire to investigate the socio-economic impacts of Onchocerciasis elimination in Abu-Hamed, River Nile State, Sudan in 2015; 512 participants in ten affected communities were interviewed. RESULTS Our findings revealed that these communities are recovering from the social and economic burden of the diseases. Ninety percent of the research participants reported general satisfaction about elimination of the disease in their community, 48.3% of them attended secondary school or university. Only 0.6% reported unemployment. Also, 25.3% and 24.7% of the participants were workers and farmers respectively. Except about the vector biting and nuisance, the majority of the respondents (90%) had no complain related to the disease after the elimination. Also, 90.5% of the participants reported either stable or increase in their work performance during the last 12 months. About 93.8% of the respondents were engaged in normal daily life activities and involved in happy events like marriage and giving birth during the last 12 months.
Collapse
Affiliation(s)
- Ayman Ahmed
- Institute of Endemic Diseases, University of Khartoum, Khartoum, Sudan
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Anas Elbashir
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Asgad A. Mohamed
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Asha A. Alim
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Asia Mubarak
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Duaa Abdelrahman
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Eilaf Mohammed
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Nouh S. Mohamed
- Department of Parasitology and Medical Entomology, Faculty of Medical Laboratory Sciences, Nile University, Khartoum, Sudan
| | - Arwa H. Elaagip
- Department of Parasitology and Medical Entomology, Faculty of Medical Laboratory Sciences, University of Khartoum, Khartoum, Sudan
| | - Isam M. A. Zarroug
- Onchocerciasis Control/Elimination Programme, National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan
| | - Noma Mounkaila
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| | - Hanan Tahir
- Public and Tropical Health Programmes, University of Medical Sciences and Technology, Khartoum, Sudan
| |
Collapse
|
3
|
Loum D, Katholi CR, Lakwo T, Habomugisha P, Tukahebwa EM, Unnasch TR. Evaluation of Community-Directed Operation of Black Fly Traps for Entomological Surveillance of Onchocerca volvulus Transmission in the Madi-Mid North Focus of Onchocerciasis in Northern Uganda. Am J Trop Med Hyg 2017; 97:1235-1242. [PMID: 29031285 DOI: 10.4269/ajtmh.17-0244] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Entomological measures of transmission are important metrics specified by the World Health Organization to document the suppression and interruption of transmission of Onchocerca volvulus, the causative agent of onchocerciasis. These metrics require testing of large numbers of vector black flies. Black fly collection has relied on human landing collections, which are inefficient and potentially hazardous. As the focus of the international community has shifted from onchocerciasis control to elimination, replacement of human landing collections has become a priority. The Esperanza window trap (EWT) has shown promise as an alternative method for collection of Simulium damnosum s.l., the primary vector of O. volvulus in Africa. Here, we report the results of a community-based trial of the EWT in northern Uganda. Traps operated by residents were compared with human landing collections in two communities over 5 months. Three traps, when operated by a single village resident, collected over four times as many S. damnosum as did the two-men collection team. No significant differences were noted among the bait formulations. The results suggest that EWTs may be effectively operated by community residents and that the trap represents a viable alternative to human landing collections for entomological surveillance of O. volvulus transmission.
Collapse
Affiliation(s)
- Denis Loum
- Nwoya District Local Government, Nwoya, Uganda
| | - Charles R Katholi
- Department of Biostatistics, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama
| | - Thomson Lakwo
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | | | - Thomas R Unnasch
- Global Health Infectious Disease Research, College of Public Health, University of South Florida, Tampa, Florida
| |
Collapse
|
4
|
Zarroug IMA, Hashim K, ElMubark WA, Shumo ZAI, Salih KAM, ElNojomi NAA, Awad HA, Aziz N, Katabarwa M, Hassan HK, Unnasch TR, Mackenzie CD, Richards F, Higazi TB. The First Confirmed Elimination of an Onchocerciasis Focus in Africa: Abu Hamed, Sudan. Am J Trop Med Hyg 2016; 95:1037-1040. [PMID: 27352878 PMCID: PMC5094213 DOI: 10.4269/ajtmh.16-0274] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 05/16/2016] [Indexed: 11/07/2022] Open
Abstract
Mass treatment with ivermectin for onchocerciasis was stopped in 2012 in Abu Hamed, an isolated focus on the River Nile in northern Sudan. A 3-year posttreatment surveillance (PTS) ensued, at the end of which an evaluation was conducted in 2015 following the current World Health Organization guidelines for verification of onchocerciasis elimination. Vector black flies were collected from sentinel breeding sites and finger-prick bloodspots were collected from children ≤ 10 years of age resident in 35 communities within the focus. Polymerase chain reaction (PCR) screening of 19,191 flies from four sites for the O-150 parasite-specific marker found no flies carrying Onchocerca volvulus larvae (0%, 95% upper confidence limit [UCL] = 0.16), and serological testing of 5,266 children identified only one Ov16 seropositive child (0.019%, 95% UCL = 0.074); whose skin snips were negative when tested by O-150 PCR assay. These results indicate that for the first time in Africa, onchocerciasis elimination has been verified after a successful PTS in Abu Hamed.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | - Hassan K Hassan
- Global Health Infectious Disease Research Program, College of Public Health, University of South Florida, Tampa, Florida
| | - Thomas R Unnasch
- Global Health Infectious Disease Research Program, College of Public Health, University of South Florida, Tampa, Florida
| | | | | | | |
Collapse
|
5
|
Zarroug IMA, Hashim K, Elaagip AH, Samy AM, Frah EA, ElMubarak WA, Mohamed HA, Deran TCM, Aziz N, Higazi TB. Seasonal Variation in Biting Rates of Simulium damnosum sensu lato, Vector of Onchocerca volvulus, in Two Sudanese Foci. PLoS One 2016; 11:e0150309. [PMID: 26943668 PMCID: PMC4778939 DOI: 10.1371/journal.pone.0150309] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Accepted: 02/11/2016] [Indexed: 11/18/2022] Open
Abstract
Background The abundance of onchocerciasis vectors affects the epidemiology of disease in Sudan, therefore, studies of vector dynamics are crucial for onchocerciasis control/elimination programs. This study aims to compare the relative abundance, monthly biting-rates (MBR) and hourly-based distribution of onchocerciasis vectors in Abu-Hamed and Galabat foci. These seasonally-based factors can be used to structure vector control efforts to reduce fly-biting rates as a component of onchocerciasis elimination programs. Methods A cross-sectional study was conducted in four endemic villages in Abu-Hamed and Galabat foci during two non-consecutive years (2007–2008 and 2009–2010). Both adults and aquatic stages of the potential onchocerciasis vector Simulium damnosum sensu lato were collected following standard procedures during wet and dry seasons. Adult flies were collected using human landing capture for 5 days/month. The data was recorded on handheld data collection sheets to calculate the relative abundance, MBR, and hourly-based distribution associated with climatic factors. The data analysis was carried out using ANOVA and Spearman rank correlation tests. Results Data on vector surveillance revealed higher relative abundance of S. damnosum s.l. in Abu- Hamed (39,934 flies) than Galabat (8,202 flies). In Abu-Hamed, vector populations increased in January-April then declined in June-July until they disappeared in August-October. Highest black fly density and MBR were found in March 2007 (N = 9,444, MBR = 58,552.8 bites/person/month), and March 2010 (N = 2,603, MBR = 16,138.6 bites/person/month) while none of flies were collected in August-October (MBR = 0 bites/person/month). In Galabat, vectors increased in September-December, then decreased in February-June. The highest vector density and MBR were recorded in September 2007 (N = 1,138, MBR = 6,828 bites/person/month) and September 2010 (N = 1,163, MBR = 6,978 bites/person/month), whereas, none appeared in collection from April to June. There was a significant difference in mean monthly density of S. damnosum s.l. across the two foci in 2007–2008 (df = 3, F = 3.91, P = 0.011). Minimum temperature showed significant correlation with adult flies counts in four areas sampled; the adult counts were increased in Nady village (rs = 0.799) and were decreased in Kalasecal (rs = - 0.676), Gumaiza (rs = - 0.585), and Hilat Khateir (rs = - 0.496). Maximum temperature showed positive correlation with black fly counts only in Galabat focus. Precipitation was significantly correlated with adult flies counts in Nady village, Abu-Hamed, but no significance was found in the rest of the sampled villages in both foci. Hourly-based distribution of black flies showed a unimodal pattern in Abu-Hamed with one peak (10:00–18:00), while a bimodal pattern with two peaks (07:00–10:00) and (14:00–18:00) was exhibited in Galabat. Conclusion Transmission of onchocerciasis in both foci showed marked differences in seasonality, which may be attributed to ecology, microclimate and proximity of breeding sites to collection sites. The seasonal shifts between the two foci might be related to variations in climate zones. This information on black fly vector seasonality, ecology, distribution and biting activity has obvious implications in monitoring transmission levels to guide the national and regional onchocerciasis elimination programs in Sudan.
Collapse
Affiliation(s)
- Isam M. A. Zarroug
- Onchocerciasis Control/Elimination Programme, National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan
- * E-mail:
| | - Kamal Hashim
- National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan
| | - Arwa H. Elaagip
- Department of Parasitology and Medical Entomology, Faculty of Medical Laboratory Sciences, University of Khartoum, Khartoum, Sudan
| | - Abdallah M. Samy
- Entomology Department, Faculty of Science, Ain Shams University, Abbassia, Cairo, Egypt
| | - Ehab A. Frah
- Biostatistics and Data Analysis Unit, Tropical Medicine Research Institute (TMRI), National Center for Research, Khartoum, Sudan
| | - Wigdan A. ElMubarak
- Onchocerciasis Control/Elimination Programme, National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan
| | - Hanan A. Mohamed
- Onchocerciasis Control/Elimination Programme, National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan
| | - Tong Chor M. Deran
- National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan
| | | | - Tarig B. Higazi
- Department of Biological Sciences, Ohio University, Zanesville, Ohio, United States of America
| |
Collapse
|
6
|
Zarroug IMA, Elaagip AH, Abuelmaali SA, Mohamed HA, ElMubarak WA, Hashim K, Deran TCM, Aziz N, Higazi TB. The impact of Merowe Dam on Simulium hamedense vector of onchocerciasis in Abu Hamed focus - Northern Sudan. Parasit Vectors 2014; 7:168. [PMID: 24708741 PMCID: PMC3976634 DOI: 10.1186/1756-3305-7-168] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 04/01/2014] [Indexed: 11/23/2022] Open
Abstract
Background Abu Hamed, the northernmost onchocerciasis focus in the world, is located along the River Nile banks in the Nubian Desert. Hydroelectric dams can alter activity of black flies and may provide breeding sites for black fly. Merowe Dam, the largest hydropower project in Africa, was built west of Abu Hamed focus in 2009. The impact of the Dam on onchocerciasis and its black fly vectors in Abu Hamed focus was measured in this study. Findings Entomological surveys for aquatic stages and adult Simulium hamedense were conducted before and after the inception of Merowe Dam in 2007/2008 and 2010/2011. There was no black fly breeding or adult activity in the previously known breeding sites upstream of the Merowe Dam with the western most breeding site found in AlSarsaf village near the center of the focus. No adult or aquatic stages of black flies were found downstream of the Dam. Conclusions The artificial lake of the Dam flooded all the breeding sites in the western region of the focus and no aquatic stages and/or adult black fly activity were established in the study area upstream of the Dam. The Dam seems to have positive impact on onchocerciasis and its black fly vectors in Abu Hamed focus. These outcomes of the Merowe Dam might have contributed to the recently declared interruption of onchocerciasis transmission in Abu Hamed focus. Continuous entomological surveys are needed to monitor presence of black fly vectors and its impact on the disease.
Collapse
Affiliation(s)
- Isam M A Zarroug
- Onchocerciasis Control/Elimination Programme, National Programme for Prevention of Blindness (NPPB), Federal Ministry of Health, Khartoum, Sudan.
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Adeleke MA, Mafiana CF, Sam-Wobo SO, Akinwale OP, Olatunde GO, Sanfo SM, Adjami A, Toè L. Molecular characterisation of theSimulium damnosumcomplex (Diptera: Simuliidae) found along the Osun River system, in south–western Nigeria. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2013; 104:679-83. [DOI: 10.1179/136485910x12851868780225] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
8
|
Higazi TB, Zarroug IMA, Mohamed HA, Elmubark WA, Deran TCM, Aziz N, Katabarwa M, Hassan HK, Unnasch TR, Mackenzie CD, Richards F, Hashim K. Interruption of Onchocerca volvulus transmission in the Abu Hamed focus, Sudan. Am J Trop Med Hyg 2013; 89:51-7. [PMID: 23690554 PMCID: PMC3748488 DOI: 10.4269/ajtmh.13-0112] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 04/09/2013] [Indexed: 11/07/2022] Open
Abstract
Abu Hamed, Sudan, the northernmost location of onchocerciasis in the world, began community-directed treatment with ivermectin (CDTI) in 1998, with annual treatments enhanced to semiannual in 2007. We assessed the status of the parasite transmission in 2011 entomologically, parasitologically, and serologically. O-150 pool screening showed no parasite DNA in 17,537 black flies collected in 2011 (95% confidence interval upper limit [95% CI UL] = 0.023). Skin microfilariae, nodules, and signs of skin disease were absent in 536 individuals in seven local communities. Similarly, no evidence of Onchocerca volvulus Ov16 antibodies was found in 6,756 school children ≤ 10 years (95% CI UL = 0.03%). Because this assessment of the focus meets the 2001 World Health Organization (WHO) criteria for interrupted transmission, treatment was halted in 2012, and a post-treatment surveillance period was initiated in anticipation of declaration of disease elimination in this area. We provide the first evidence in East Africa that long-term CDTI alone can interrupt transmission of onchocerciasis.
Collapse
Affiliation(s)
- Tarig B Higazi
- Department of Biological Sciences, Ohio University, Zanesville, OH, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Higazi TB, Zarroug IMA, Mohamed HA, Elmubark WA, Mohamed WA, Deran TCM, Aziz N, Katabarwa M, Hassan HK, Unnasch TR, Mackenzie CD, Richards F. Polymerase chain reaction pool screening used to compare prevalence of infective black flies in two onchocerciasis foci in northern Sudan. Am J Trop Med Hyg 2011; 84:753-6. [PMID: 21540385 DOI: 10.4269/ajtmh.2011.11-0009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Onchocerciasis remains an important debilitating disease in many areas of Africa, including Sudan. The status of infection transmission in 2007 was assessed in the vectors of two disease foci in Sudan: Abu Hamed in northern Sudan, which has received at least 10 years of annual treatment and Galabat focus in eastern Sudan, where only minor, largely undocumented treatment activity has occurred. Assessment of more than 30,000 black flies for Onchocerca volvulus infectious stage L3 larvae by using an O-150 polymerase chain reaction protocol showed that black fly infectivity rates were 0.84 (95% confidence interval = 0.0497-1.88) per 10,000 flies for Abu Hamed and 6.9 (95% confidence interval = 1.1-16.4) infective flies per 10,000 for Galabat. These results provide entomologic evidence for suppressed Onchocerca volvulus transmission in the Abu Hamed focus and a moderate transmission rate of the parasite in the Galabat focus.
Collapse
Affiliation(s)
- Tarig B Higazi
- Department of Biological Sciences, Ohio University, 1425 Newark Road, Zanesville, OH 43701, USA.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Good species behaving badly: Non-monophyly of black fly sibling species in the Simulium arcticum complex (Diptera: Simuliidae). Mol Phylogenet Evol 2010; 57:245-57. [DOI: 10.1016/j.ympev.2010.06.024] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 05/14/2010] [Accepted: 06/25/2010] [Indexed: 11/21/2022]
|
11
|
Adler PH, Cheke RA, Post RJ. Evolution, epidemiology, and population genetics of black flies (Diptera: Simuliidae). INFECTION GENETICS AND EVOLUTION 2010; 10:846-65. [DOI: 10.1016/j.meegid.2010.07.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2010] [Revised: 07/02/2010] [Accepted: 07/02/2010] [Indexed: 10/19/2022]
|
12
|
Phylogenetic relationships among the black fly species (Diptera: Simuliidae) of Thailand based on multiple gene sequences. Genetica 2010; 138:633-48. [DOI: 10.1007/s10709-010-9437-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2009] [Accepted: 01/13/2010] [Indexed: 11/26/2022]
|
13
|
Post RJ, Mustapha M, Krueger A. Taxonomy and inventory of the cytospecies and cytotypes of the Simulium damnosum complex (Diptera: Simuliidae) in relation to onchocerciasis. Trop Med Int Health 2008; 12:1342-53. [PMID: 18045261 DOI: 10.1111/j.1365-3156.2007.01921.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We provide an inventory of all named cytoforms of the Simulium damnosum complex (including those which are now considered invalid), along with all inversions that have been recorded (including synonyms and homonyms). There are 55 valid and distinct cytoforms known from the S. damnosum complex making it the largest sibling species complex of any vectors, and probably of any insect or other animal. All cytoforms are listed along with their fixed and diagnostic inversions and country distribution. There are 183 inversions known from the complex as a whole, of which 49% are fixed and/or diagnostic between cytoforms, and the fixed/diagnostic inversions seem to occur disproportionately on chromosome arm 2L.
Collapse
Affiliation(s)
- R J Post
- The Natural History Museum London and London School of Hygiene & Tropical Medicine, UK.
| | | | | |
Collapse
|
14
|
Rodríguez-Pérez MA, Núñez-González CA, Lizarazo-Ortega C, Sánchez-Varela A, Wooten MC, Unnasch TR. Analysis of genetic variation in ribosomal DNA internal transcribed spacer and the NADH dehydrogenase subunit 4 mitochondrial genes of the onchocerciasis vector Simulium ochraceum. JOURNAL OF MEDICAL ENTOMOLOGY 2006; 43:701-6. [PMID: 16892627 DOI: 10.1603/0022-2585(2006)43[701:aogvir]2.0.co;2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Onchocerciasis is a serious disease vectored by black flies in the genus Simulium that are infected with the filarial parasite Onchocerca volvulus. In the Americas, black flies of the Simulium ochraceum s.l. species complex are important vectors of this parasite. Cytological studies have suggested that this species complex consists of at least three cytotypes that inhabit distinct habitats. In this study, the NADH dehydrogenase subunit four (ND4) and internal transcribed spacer (ITS) of the ribosomal RNA gene cluster were used to explore the degree of genetic diversity among S. ochraceum s.l. populations found in the three O. volvulus foci in Mexico. Both sequence regions were found to exhibit intra- and interpopulation variation. Four different ND4 alleles were found among the populations examined. Similarly, variation was noted in the ITS domain sequences within and among populations. Variation within the ITS sequence was primarily confined to a complex microsatellite locus. Four ITS length variants were observed, two of which were only seen in flies collected from the onchocerciasis focus in northern Chiapas. These data suggest that the ND4 and ITS sequences may prove to be useful markers for exploring interactions within and among the S. ochraceum s.l. populations in Mexico.
Collapse
Affiliation(s)
- Mario A Rodríguez-Pérez
- Centro de Biotecnología Genómica, Instituto Politécnico Nacional, Blvd. del Maestro Esq. Elías Pińa, Col. Narciso Mendoza, 88710, Reynosa, Tamaulipas, México
| | | | | | | | | | | |
Collapse
|
15
|
Charalambous M, Lowell S, Arzube M, Lowry CA. Isolation by distance and a chromosomal cline in the Cayapa cytospecies of Simulium exiguum, the vector of human onchocerciasis in Ecuador. Genetica 2005; 124:41-59. [PMID: 16011002 DOI: 10.1007/s10709-004-5491-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The population genetic structure of the Cayapa cytospecies of Simulium exiguum, the vector of onchocerciasis, was analysed using allozyme frequency and chromosomal inversion polymorphism data from 6 and 15 populations respectively, collected in Ecuador. Eight allozyme loci were scored. No unique allozyme markers were found enabling us to identify biting adults of the vector from the non-vector Bucay cytotype. Mannose-phosphate isomerase (Mpi) contributed largely to the significant heterogeneity in gene frequency among populations of the Cayapa cytospecies and also to the overall population structuring (F(ST) = 0.015 +/- 0.014) which fitted the isolation by distance model. However, heterozygote deficits were recorded for Mpi in four of the six populations, which could indicate that selection is acting at this locus but this hypothesis will require further convincing evidence. Furthermore the significant population structuring of allozymes was not evident when Mpi was omitted from the analysis. All inversion polymorphisms (IIS-B, IIS-F, IIL-A and IIL-B) were in Hardy-Weinberg equilibrium, showed significant heterogeneity between populations and revealed the occurrence of an altitudinal cline in inversion IIS-B frequency. The inversion polymorphisms revealed a significant degree of population structuring (F(ST) = 0.083 +/- 0.027), which can be explained by the isolation by distance model. A UPGMA cluster analysis revealed the relatively remote, high altitude Rio Mira populations to be the most genetically distinct.
Collapse
Affiliation(s)
- M Charalambous
- Department of Biological Sciences, Imperial College London, Silwood Park, Ascot, Berkshire SL5 7PY, UK.
| | | | | | | |
Collapse
|
16
|
Higazi TB, Katholi CR, Mahmoud BM, Baraka OZ, Mukhtar MM, Qubati YA, Unnasch TR. Onchocerca volvulus: genetic diversity of parasite isolates from Sudan. Exp Parasitol 2001; 97:24-34. [PMID: 11207111 DOI: 10.1006/expr.2000.4589] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Onchocerciasis in Sudan exists in three distinct foci which exhibit differing clinical presentations. Previous studies have demonstrated that a tandemly repeated Onchocerca sequence family with a unit repeat length of 150 bp (the O-150 family) is a useful marker for deducing relationships among different O. volvulus populations. In the current study, the O-150 repeat families of O. volvulus from Sudan were analyzed and compared to each other and to those of parasites from West Africa. Similar to West African and American O. volvulus, the O-150 families of the Sudanese parasites could be divided into clusters within which little or no intracluster variation was evident, suggesting that the O-150 family in these parasites was subject to the forces of concerted evolution. Statistical analysis of the O-150 families from the different Sudanese parasite isolates, employing a nested algorithm based on an analysis of variance, revealed that O. volvulus endemic to the northern focus at Abu Hamed were significantly different from all other O. volvulus populations examined to date. In contrast, parasites from the southern and eastern foci of Sudan were indistinguishable from those endemic to the West African savanna. The significance of these data are discussed in light of knowledge of the biogeography and biology of transmission of O. volvulus in Africa.
Collapse
Affiliation(s)
- T B Higazi
- Division of Geographic Medicine, BBRB 203, University of Alabama at Birmingham, 35294, USA
| | | | | | | | | | | | | |
Collapse
|