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Thomas R Unnasch - One of the best experts on this subject based on the ideXlab platform.

  • Molecular Identification of Onchocerca spp. Larvae in Simulium damnosum sensu lato Collected in Northern Uganda.
    The American journal of tropical medicine and hygiene, 2017
    Co-Authors: Guilherme G. Verocai, Hassan K. Hassan, Thomson Lakwo, Peace Habomugisha, Moses N. Katabarwa, Stephen Begumisa, Philbert Clouds, James Katamanywa, Christine Nahabwe, Thomas R Unnasch
    Abstract:

    Previous studies have demonstrated that the presence of larvae of other filarial species in Simulium damnosum sensu lato can distort estimates of transmission potential for Onchocerca volvulus in West Africa. However, studies conducted in foci of onchocerciasis in West Central Uganda indicated that larvae other than O. volvulus were not common in vectors collected there. Recent data collected in Northern Uganda revealed a striking discordance between estimates of the prevalence of flies carrying O. volvulus infective larvae obtained from molecular pool screening and dissection methods. To resolve this discrepancy, sequences from three mitochondrially encoded genes were analyzed from the larvae collected by dissection. All larvae analyzed were Onchocerca ochengi v. Siisa, a parasite of cattle, or Onchocerca ramachandrini, a parasite of warthogs. These results suggest that nonhuman parasite larvae are common in vectors in Northern Uganda, underscoring the necessity for molecular identification methods to accurately estimate O. volvulus transmission.

  • Mitochondrial alleles of Simulium damnosum sensu lato infected with Onchocerca volvulus
    International Journal for Parasitology, 1995
    Co-Authors: Jianming Tang, Christian Back, Thomas R Unnasch
    Abstract:

    Abstract Onchocerca volvulus infected Simulium damnosum s.l. were analysed by directed heteroduplex analysis. Of 73 infected flies, 68 produced heteroduplex products identical to those previously identified. All 6 major sibling species, except S. leonense, were present in this group. In the 5 remaining flies, 2 new heteroduplex patterns were noted. Molecular phylogenetic analysis of these samples suggested that they belonged to the S. squamosum/S. yahense subcomplex. The ability to reliably genotype adult flies will permit studies of the vectorial capacity of the sibling species of S. damnosum s.l. for the blinding and non-blinding strains of O. volvulus.

  • The Simulium damnosum species complex: phylogenetic analysis and molecular identification based upon mitochondrially encoded gene sequences
    Insect molecular biology, 1995
    Co-Authors: Jianming Tang, Christian Back, Laurent Toe, Peter A. Zimmerman, K. P. Pruess, Thomas R Unnasch
    Abstract:

    The DNA sequence of portions of the 16s rRNA and the NADH dehydrogenase subunit 4 (ND4) genes were used to determine phylogenetic relationships in the Simulium damnosum s.l. species complex. Results suggested that at least two major clades existed in the S. damnosum species complex, and that members of the S. damnosum s.l. species complex were not closely related to North American Simulium species. The sequence variability of the ND4 gene was exploited to develop a method to distinguish the sibling species of the S. damnosum s.l. species complex, based on directed heteroduplex analysis of PCR products derived from the ND4 gene. This method was capable of classifying the six sibling species into at least five groups.

Robert Cheke - One of the best experts on this subject based on the ideXlab platform.

  • Onchocerciasis transmission in Ghana: the human blood index of sibling species of the Simulium damnosum complex.
    Parasites & vectors, 2016
    Co-Authors: Poppy Lamberton, Daniel A. Boakye, Robert Cheke, Martin Walker, Peter Winskill, J. Crainey, Mike Osei-atweneboana, IĂąaki Tirados, Michael D. Wilson, Anthony Tetteh-kumah
    Abstract:

    Background Vector-biting behaviour is important for vector-borne disease (VBD) epidemiology. The proportion of blood meals taken on humans (the human blood index, HBI), is a component of the biting rate per vector on humans in VBD transmission models. Humans are the definitive host of Onchocerca volvulus, but the simuliid vectors feed on a range of animals and HBI is a key indicator of the potential for human onchocerciasis transmission. Ghana has a diversity of Simulium damnosum complex members, which are likely to vary in their HBIs, an important consideration for parameterization of onchocerciasis control and elimination models.

  • Additional file 2: of Onchocerciasis transmission in Ghana: the human blood index of sibling species of the Simulium damnosum complex
    2016
    Co-Authors: Poppy Lamberton, Robert Cheke, Martin Walker, Peter Winskill, J. Crainey, Daniel Boakye, Mike Osei-atweneboana, IĂąaki Tirados, Michael Wilson, Anthony Tetteh-kumah
    Abstract:

    Rainfall data for study years and informal validation of EPIONCHO using the value of HBI estimated for the savannah members of the Simulium damnosum (s.l.) complex. (DOC 94 kb

  • Inverse density dependence of parity rates in the onchocerciasis vector Simulium damnosum s.l.
    Medical and veterinary entomology, 2015
    Co-Authors: Robert Cheke, Stephen Young, Rolf Garms
    Abstract:

    A correlation between parity rates and an index of adult numbers of Simulium damnosum s.l. (Diptera: Simuliidae) indicates an association, but does not prove causality or show the direction of any causal relationship. The question of whether adult numbers affect parity rates or vice versa is reminiscent of the age-old query of which of the chicken and the egg came first. A method for resolving such issues based on analyses of pairs of time series was proposed by Granger in 1969. When Granger's method was applied to monthly numbers of adult female S. damnosum s.l. caught attempting to bite humans at Asubende, Ghana, and their parity rates, a significant relationship (P = 0.005) emerged, clearly showing that parity rates were dependent on adult numbers. Implications of this inverse density dependence and the results of analyses of other similar time series are presented and discussed.

  • The thermal constant of the onchocerciasis vector Simulium damnosum s.l. in West Africa
    Medical and veterinary entomology, 2011
    Co-Authors: Robert Cheke
    Abstract:

    The minimum water temperature for development (t0) and the thermal constant (K) for the development of immature stages of Simulium damnosum s.l. (Diptera: Simuliidae) in West Africa were estimated as 20.1 ◦C and 93 day-degrees, respectively, based on analyses of published data on development rates of eggs, larvae and pupae at different water temperatures (24.0 ◦C and 31.5 ◦C). Thus, at a constant water temperature of 30.0 ◦C (approximately 10 ◦C above t0), adult flies would emerge about 9 days after oviposition. Analysis of a dataset probably restricted to S. damnosum s.s., but for which the temperature for the egg stage varied, revealed a much lower t0 (16.3 ◦C) and a much higher K (181 day-degrees), suggesting that the insects’ thermal relations may be cytoform-specific. The results will aid control decisions and predictions of possible effects of climate change on sizes and geographic distributions of populations of onchocerciasis vectors in West Africa.

  • Assessment of rDNA IGS as a molecular marker in the Simulium damnosum complex.
    Medical and veterinary entomology, 2002
    Co-Authors: Ramiro Morales-hojas, Robert Cheke, Rory J. Post, Wilson
    Abstract:

    For five cytospecies of the Simulium damnosum Theobald complex of blackflies (Diptera: Simuliidae) from West Africa, both ends of the intergenic spacer region (IGS) of the rDNA have been sequenced with the aim of developing specific molecular markers. No specific differences in these two regions were detected between Simulium sanctipauli V. & D., Simulium sirbanum V. & D., Simulium soubrense V. & D., Simulium squamosum Enderlein and Simulium yahense V. & D., except in the number of A subrepeats at the 5' end of the IGS (two in S. squamosum and four or five in the others) and in position 310 of the 3' end (a C in S. squamosum and a G in the others). However, genetic distances within and between species overlapped. These DNA sequences had no strong phylogenetic signal, and the trees obtained were mostly unresolved. Although most sequences from S. squamosum clustered together, a few of them were more similar to those in other cytospecies. These results could be explained either by hybridization with genetic introgression or by ancestral polymorphism and recent speciation.

B. T. A. Maegga - One of the best experts on this subject based on the ideXlab platform.

  • Susceptibility of Simulium damnosum complex larvae to temephos in the Tukuyu onchocerciasis focus, southwest Tanzania
    2015
    Co-Authors: A. K. Kalinga, C. N. Mweya, T. Barro, B. T. A. Maegga
    Abstract:

    Abstract: Tukuyu onchocerciasis focus was earmarked for vector control using insecticide against larval stages. Susceptibility tests of mature larvae of Simulium damnosum s.l. vectors to temephos insecticide were carried out before and after two years of insecticide treatment of rivers within Tukuyu onchocerciasis focus, south-western Tanzania. The tests were done in 1999/2000 and 2004 using WHO standard methods. Mature larvae were exposed to 9 concentrations of temephos active ingredient, from the weakest 0.00975mg/litre to the strongest of 2.5mg/l. Each test concentration and control was run in duplicates of 25 larvae each, set for three hours in a cool temperature. After incubation, test solution was discarded and larval condition checked. Numbers of larvae in each category were recorded and used to determine mortality rate for each concentration as well as for the L

  • Revision of the Ketaketa subcomplex of blackflies of the Simulium damnosum complex
    Medical and veterinary entomology, 2006
    Co-Authors: A. Krueger, M. Mustapha, Akili K. Kalinga, P. A. J. Tambala, Rory J. Post, B. T. A. Maegga
    Abstract:

    A revision of the taxonomy of the Ketaketa subcomplex of the Simulium damnosum Theobald complex (Diptera: Simuliidae) is presented including new material from Tanzania, Malawi and South Africa. The cytotaxonomy, morphology and molecular identity of known and new taxa are described. The Ketaketa subcomplex is cytotaxonomically defined by the paracentric inversion 1L-7. We recognize three sibling species, namely Simulium latipollex (Enderlein), Simulium plumbeum Krueger, sp.n. and Simulium kipengere Krueger, sp.n., the latter comprising three cytoforms: 'Typical', 'Linthipe' and 'Mombo'. The cytoforms 'Mwamphanzi', 'Ketaketa' and 'Hammerkopi' are synonymized with S. plumbeum. Identification keys are provided on the basis of chromosomal and morphological characters. In view of their potential role as vectors of human onchocerciasis (river blindness) we also discuss the possible medical importance of the different cytoforms and their geographical distribution.

  • Descriptions of members of the Simulium damnosum complex (Diptera: Simuliidae) from southern Africa, Ethiopia and Tanzania.
    Annals of tropical medicine and parasitology, 2005
    Co-Authors: A. Krüger, M. Car, B. T. A. Maegga
    Abstract:

    This paper presents cytotaxonomic details of five populations of the Simulium damnosum complex from South Africa, Swaziland and Ethiopia. The 'Nkusi SW' and 'Pienaars' forms are newly designated members of the complex from South Africa, but the taxonomic rank of an isolate indistinguishable chromosomally from the 'Nkusi' cytoform remains unclear. From Ethiopia two cytoforms were identified, one of which shares two diagnostic chromosome inversions with the cytoform 'Kisiwani' from Tanzania. The second form belongs to S. kaffaense, and is the suspected local vector of Onchocerca volvulus. In addition, a re-analysis of the cytoform 'Kibwezi' from north-eastern Tanzania provided further insights into its population subdivision, and its genetic and morphological characteristics. Cytotaxonomic similarities between 'Kibwezi', S. mengense and S. pandanophilum, along with their biogeography, indicate a relict status of each of these taxa.

  • Cytotaxonomy of the Simulium damnosum complex and description of new cytotypes in the Tukuyu focus, southwest Tanzania.
    Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenar, 1994
    Co-Authors: B. T. A. Maegga, E. W. Cupp
    Abstract:

    Larvae of Simulium damnosum complex collected from rivers draining Tukuyu onchocerciasis focus were chromosomally examined. Of the 970 larvae analysed, 910 were identified as Kiwira form, a newly described cytotype found in all S. damnosum larval habitats in the Tukuyu area, while 51 were classified as a new subpopulation, tentatively named as Kasyabone form. The F1 larval progeny obtained from wild caught human biting S. damnosum and reared in the laboratory were chromosomally examined. 509 F1 larvae from 70 females blood fed on human volunteers were identified as Kiwira form. As the main human-biting member of the complex in the Tukuyu area, and because some of the wild caught females had developing filarial larvae indistinguishable from those of Onchocerca volvulus, Kiwira form is thus incriminated as the local vector of onchocerciasis. These observations are discussed with respect to previous literature.

  • Chromosomal diagnostic criteria for some members of Simulium damnosum complex in east Africa.
    Tropical medicine and parasitology : official organ of Deutsche Tropenmedizinische Gesellschaft and of Deutsche Gesellschaft fur Technische Zusammenar, 1993
    Co-Authors: B. T. A. Maegga, E. W. Cupp
    Abstract:

    Identification of Simulium damnosum s.l. vectors of onchocerciasis demands adequate knowledge of the chromosomal features that distinguish human-biting members from nonanthropophilic forms. In this study, 955 S. damnosum larvae collected from various geographical locations in Tanzania were chromosomally analyzed. 358 larvae from small mountain streams in the northeast and central regions of Tanzania, were identified as mainly Nyamagasani and Sanje forms, with only one Kiwira form. 378 larvae from plain and lowland rivers, also in the northeast and central regions, were identified as Nkusi, Kisiwani and Kibwezi forms. Chromosomal examination of 219 larvae from the southern highlands zone revealed the presence of Kiwira and Nyamagasani forms

Daniel A. Boakye - One of the best experts on this subject based on the ideXlab platform.

  • Notes on distribution of Simulium damnosum s. l. along Atbara River in Galabat sub-focus, eastern Sudan
    BMC infectious diseases, 2019
    Co-Authors: Isam M. A. Zarroug, Oa Surakat, Arwa H. Elaagip, Suhaib G. Gumaa, Altayeb K. Ali, Ayman Ahmed, Hanaa Adli Siam, Deena M. Abdelgadir, Olatunwa J. Olamiju, Daniel A. Boakye
    Abstract:

    Background Onchocerciasis is caused by a nematode worm Onchocerca volvulus, which is transmitted in Sudan by black fly vectors of the Simulium damnosum sensu lato species complex. In Sudan, the disease is found in four foci where fast flowing rivers provide suitable breeding sites for the Simulium vector flies. The construction of dams and irrigation schemes for agricultural purposes has affected black fly breeding and distribution, such as in Merowe Dam in Abu-Hamed focus, where the perennially flowing water downstream of the Dam created new vector breeding sites, thereby, changing the pattern of disease transmission and creating public health problems. Based on this situation, this study was carried out to measure the effect of the Upper Atbara and Setit Dam complex on the distribution of Simulium damnosum s.l. breeding sites and on disease elimination in the Galabat sub-focus in eastern Sudan.

  • Notes on distribution of Simulium damnosum s. l. along Atbara River in Galabat sub-focus, eastern Sudan
    BMC Infectious Diseases, 2019
    Co-Authors: Isam M. A. Zarroug, Arwa H. Elaagip, Suhaib G. Gumaa, Altayeb K. Ali, Ayman Ahmed, Hanaa Adli Siam, Deena M. Abdelgadir, Olatunwa J. Olamiju, Olabanji A. Surakat, Daniel A. Boakye
    Abstract:

    Background Onchocerciasis is caused by a nematode worm Onchocerca volvulus , which is transmitted in Sudan by black fly vectors of the Simulium damnosum sensu lato species complex. In Sudan, the disease is found in four foci where fast flowing rivers provide suitable breeding sites for the Simulium vector flies. The construction of dams and irrigation schemes for agricultural purposes has affected black fly breeding and distribution, such as in Merowe Dam in Abu-Hamed focus, where the perennially flowing water downstream of the Dam created new vector breeding sites, thereby, changing the pattern of disease transmission and creating public health problems. Based on this situation, this study was carried out to measure the effect of the Upper Atbara and Setit Dam complex on the distribution of Simulium damnosum s.l. breeding sites and on disease elimination in the Galabat sub-focus in eastern Sudan. Methods Aquatic stages of Simulium were collected between October and November 2009, prior to the construction of the dam complex, and again in 2013 and 2015 while the dam complex construction was ongoing. Results A total of 40 breeding sites were identified at the beginning of the study. After the construction of the dam complex in 2015, seventeen previously mapped breeding sites were inaccessible as they had been flooded by the dam complex’s lake when reach its maximum size. Three species were obtained from different locations: S. damnosum s.l. , S. griseicolle , and S. adersi . Conclusions This study has shown a link between the construction of the dam complex and a reduction in the breeding sites of black fly vectors. This reduction has limited the Galabat sub-focus to a small area at the upper Atbara River which become the end of the focus. To sustain the success achieved in onchocerciasis control in the Galabat sub-focus, disease control and its vector control should be strengthened in the area cross-boarding Sudan and Ethiopia.

  • Onchocerciasis transmission in Ghana: the human blood index of sibling species of the Simulium damnosum complex.
    Parasites & vectors, 2016
    Co-Authors: Poppy Lamberton, Daniel A. Boakye, Robert Cheke, Martin Walker, Peter Winskill, J. Crainey, Mike Osei-atweneboana, IĂąaki Tirados, Michael D. Wilson, Anthony Tetteh-kumah
    Abstract:

    Background Vector-biting behaviour is important for vector-borne disease (VBD) epidemiology. The proportion of blood meals taken on humans (the human blood index, HBI), is a component of the biting rate per vector on humans in VBD transmission models. Humans are the definitive host of Onchocerca volvulus, but the simuliid vectors feed on a range of animals and HBI is a key indicator of the potential for human onchocerciasis transmission. Ghana has a diversity of Simulium damnosum complex members, which are likely to vary in their HBIs, an important consideration for parameterization of onchocerciasis control and elimination models.

  • Evidence of Multiple Mating and Hybridization in Simulium damnosum s.l. (Diptera: Simuliidae) in Nature
    Journal of medical entomology, 2000
    Co-Authors: Daniel A. Boakye, C. Back, P. M. Brakefield
    Abstract:

    Beakers with aeration were used to rear individual (single) egg batches of Simulium damnosum (Theobald) s.l. to larvae and adults. Chromosomal analysis of the progeny of individual females indicated that multiple mating occurred within the S. damnosum complex and that hybridization occurred between S. damnosum s.s. and S. sirbanum (Vajime & Dunbar) in nature. These results indicate that possibly more extensive hybridization may be taking place in some areas of the Onchocerciasis Control Program than previously reported. Dramatic changes in the rates of hybridization among members of the S. damnosum complex possibly may lead to the formation of new cytotypes.

R. Garms - One of the best experts on this subject based on the ideXlab platform.

  • Molecular identification and phylogeny of East African Simulium damnosum s.l. and their relationship with west african species of the complex (Diptera: Simuliidae).
    Insect molecular biology, 2000
    Co-Authors: A. Krüger, A. Gelhaus, R. Garms
    Abstract:

    The phylogenetic relationships of East and West African members of the Simulium damnosum complex were studied by sequence analyses of the mitochondrial 16s ribosomal RNA (rRNA) gene. Results suggest that: (i) the S. damnosum complex is divided into an East and a West African clade, and (ii) S. pandanophilum and the cytoform ‘Kiwira’ form an East African subbranch distinct from the ‘Sanje’ group. In contrast to former assumptions from cytogenetic analyses, our molecular data do not support a direct relationship between the East African S. kilibanum and the West African S. squamosum. Length differences of the rDNA internal transcribed spacer 1 (ITS-1) turned out to be useful to distinguish between cytoforms.

  • Morphometric characterization of members of the Simulium damnosum Theobald complex (Diptera: Simuliidae) from East and West Africa.
    Annals of tropical medicine and parasitology, 1999
    Co-Authors: Andreas Krüger, R. Garms
    Abstract:

    Morphometric multivariate analyses were carried out in order to separate the females of the closely related anthropophilic and non-anthropophilic members of the Simulium damnosum s.l. complex occurring in western Uganda. Simulium kilibanum (= ‘Nyamagasani’), ‘Nkusi’, ‘Sebwe’ and S. pandanophilum were compared with the West African S. damnosum subcomplex, S. soubrense and S. yahense to correlate the results with those of previous studies. Simulium pandanophilum could be clearly discriminated. However, only 72%–88% of identifications among the closely related S. kilibanum, ‘Sebwe’ and ‘Nkusi’, which all belong to the ‘Sanje’ subcomplex, were correct. The two forest species S. soubrense and S. yahense slightly overlapped but were distinct from all others.