The cytotaxonomy of <i>Simulium damnosum</i> s.l. (Diptera: Simuliidae) from the Thyolo onchocerciasis focus in Malawi and description of a new member of the complex

Vajime, C. G.; Tambala, P. A. J.; Krüger, Andreas; Post, R.J.

doi:10.1080/00034983.2000.11813540

Cited by 10 publications

(39 citation statements)

References 8 publications

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“…The results of the cytotaxonomic investigations in the present study are similar to those of Vajime et al (2000), who reported that S. thyolense and the S. damnosum 'Ketaketa' subcomplex (including the 'unassigned' and 'Mwamphanzi' forms) were present in Thyolo, whereas S. kilibanum was absent. The lengths of the PCR amplicons, from the larvae of known species identity, confirm the molecular diagnostic criteria of Krü ger et al…”

Section: Discussionsupporting

confidence: 91%

“…The 'Ketaketa' cytotype [which appears similar to the 'C2' cytoform described by Procunier and Muro (1993)], the 'Mwamphanzi' cytotype and the 'unassigned' form were all thought to lie within the 'Ketaketa' subcomplex, although the lack of full karyotypes prevented their precise cytotaxonomic relationships within this subcomplex being elucidated (Vajime et al, 2000). The results of the examination of new material from Malawi and Tanzania have revealed a more complicated situation, and at present it is impossible to distinguish different members of the 'Ketaketa' subcomplex with any confidence (A. Krü ger, unpubl.…”

mentioning

confidence: 77%

“…larvae so that their polytene chromosomes could be prepared as described by Krü ger (2003). Chromosome re-arrangements were scored with reference to the published maps, idiograms and descriptions of the relevant East African cytospecies (Dunbar, 1969;Dunbar and Vajime, 1981;Procunier and Muro, 1993;Maegga and Cupp, 1993;Maegga and Cupp, 1994;Krü ger et al, 1998;Vajime et al, 2000). The diagnostic inversions used to identify the species were 2L-AK and 3L-97 for S. thyolense, 1L-3.4C, 2L-67 and 2L-C2 for S. damnosum 'Ketaketa', and, as this species has been designated 'standard' for all cytotaxonomy (Dunbar and Vajime, 1981), the absence of any fixed inversion for S. kilibanum.…”

Section: Methodsmentioning

confidence: 99%

“…Five members of the S. damnosum complex have been described in the focus, on the basis of inversion differences in their larval polytene chromosomes: S. thyolense, S. kilibanum, S. damnosum 'Ketaketa', S. damnosum 'Mwamphanzi', and an as yet 'unassigned' form of the S. damnosum complex (Vajime et al, 2000). The 'Ketaketa' cytotype [which appears similar to the 'C2' cytoform described by Procunier and Muro (1993)], the 'Mwamphanzi' cytotype and the 'unassigned' form were all thought to lie within the 'Ketaketa' subcomplex, although the lack of full karyotypes prevented their precise cytotaxonomic relationships within this subcomplex being elucidated (Vajime et al, 2000).…”

mentioning

confidence: 99%

“…There have been no studies that have directly identified the anthropophilic flies from Thyolo, although S. thyolense appears the most likely vector because its geographical distribution in the district resembles that of the human-biting flies (Vajime et al, 2000). Apart from their chromosomal differences, S. thyolense and S. kilibanum are known to differ in terms of the length of the amplicon produced in PCR based on the gene coding for the internal-transcribedspacer region of their nuclear ribosomal DNA (ITS-1 rDNA).…”

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confidence: 99%

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Incrimination ofSimulium thyolense(Diptera: Simuliidae) as the anthropophilic blackfly in the Thyolo focus of human onchocerciasis in Malawi

Mustapha

Krüger

Tambala

et al. 2005

Annals of Tropical Medicine & Parasitology

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The sibling species of the Simulium damnosum complex that are potential vectors in the foci of human onchocerciasis found in southern Malawi (the southern-most foci in Africa) were identified, using a combination of cytotaxonomic and molecular techniques. Simulium thyolense was found to be the most abundant species within the foci (representing 91% of the larvae collected), whilst S. kilibanum and cytoforms of the 'Ketaketa' subcomplex were the dominant members of the complex found outside of the foci. As all 188 biting female flies collected from the Thyolo, Mwanza and Mulanje foci were identified as S. thyolense, this species is probably the only significant vector of Onchocerca volvulus in the area, and the other Simulium species collected are assumed to be zoophilic. The results confirm the diagnostic value of the size of the amplicon(s) produced in PCR based on the sequences coding for the internal-transcribed-spacer region of the nuclear ribosomal DNA (ITS-1 rDNA), with a characteristic 340bp amplicon for S. thyolense. Chromosomal polymorphisms within S. thyolense indicate some degree of geographical isolation of the 'Thyolo-Mulanje' focus from the Mwanza focus.

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Section: Discussionsupporting

confidence: 91%

mentioning

confidence: 77%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Incrimination ofSimulium thyolense(Diptera: Simuliidae) as the anthropophilic blackfly in the Thyolo focus of human onchocerciasis in Malawi

Mustapha

Krüger

Tambala

et al. 2005

Annals of Tropical Medicine & Parasitology

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The blackfly vectors and transmission of Onchocerca volvulus in Mahenge, south eastern Tanzania

et al. 2018

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The Mahenge Mountains onchocerciasis focus in south eastern Tanzania was historically one of the most heavily infected areas in the country. The vectors of Onchocerca volvulus are mainly Simulium damnosum complex blackflies, but a species of the Simulium neavei group may also contribute to transmission in some areas. The only detailed studies of parasite transmission in Mahenge were conducted in the late 1960s. The taxonomy of the S. damnosum complex has since been revised and onchocerciasis control through annual community directed treatment with ivermectin (CDTI) commenced in 1997. This study aimed to provide a cytogenetic and molecular update of the S. damnosum complex cytoforms present in Mahenge, and to evaluate the current status of O. volvulus transmission by blackflies following 19 years of annual CDTI. Rivers were surveyed to identify sites of S. damnosum s.l. breeding among the eastern slopes of the mountains, and human landing collections of adult female blackflies were made close to breeding sites. Identification of S. damnosum complex cytoforms was by cytotaxonomy of late-instar larvae and ITS1 amplicon size polymorphisms of larvae and adults. Adult blackflies were pool screened for O. volvulus infection using a triplex real-time PCR. The cytoforms 'Nkusi', Simulium kilibanum and 'Turiani' were found breeding in perennial rivers. 'Nkusi' and S. kilibanum were collected on human bait at 7/7 catch sites and possessed ITS1 profiles most closely resembling the molecular forms 'Nkusi J' and S. kilibanum 'T'. Whereas 'Turiani' was present in rivers, it was not collected on human bait and appears to be zoophilic. Simulium nyasalandicum was collected in low numbers on human bait at 3/7 catch sites. In total, 12,452 S. damnosum s.l. were pool screened and O. volvulus infection was detected in 97/104 pools of bodies and 51/104 pools of heads. The estimated percentage of S. damnosum s.l. carrying infective L3 stage parasites was 0.57% (95% CI 0.43%-0.74%). Onchocerca volvulus transmission by S. damnosum s.l. is continuing in the Mahenge Mountains after 19 years of annual CDTI. Infection rates appear similar to those reported in the 1960s, but a more detailed study is required to fully understand the epidemiological significance of the ongoing transmission. These results provide further evidence that annual CDTI may be insufficient to eliminate the parasite in formerly hyperendemic foci.

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Cytotaxonomy of Simulium soderense sp. nov. and a redescription of the ‘Kulfo’ form (Dunbar, 1969) of Simulium damnosum s.l. (Diptera: Simuliidae) as Simulium kulfoense sp. nov. in Ethiopia

Hadis

Wilson

Cobblah

et al. 2008

JTI

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The cytotaxonomy of Simulium damnosum s.l. (Diptera: Simuliidae) from the Thyolo onchocerciasis focus in Malawi and description of a new member of the complex

Cited by 10 publications

References 8 publications

Incrimination ofSimulium thyolense(Diptera: Simuliidae) as the anthropophilic blackfly in the Thyolo focus of human onchocerciasis in Malawi

Incrimination ofSimulium thyolense(Diptera: Simuliidae) as the anthropophilic blackfly in the Thyolo focus of human onchocerciasis in Malawi

The blackfly vectors and transmission of Onchocerca volvulus in Mahenge, south eastern Tanzania

Cytotaxonomy of Simulium soderense sp. nov. and a redescription of the ‘Kulfo’ form (Dunbar, 1969) of Simulium damnosum s.l. (Diptera: Simuliidae) as Simulium kulfoense sp. nov. in Ethiopia

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