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R Garms

Publications and source records attributed to R Garms.

At least 19 recordsLinked to original sources
PubMed2004

Efficiency of Simulium sanctipauli as a vector of Onchocerca volvulus in the forest zone of Ghana.

The role of Simulium sanctipauli Vajime & Dunbar (Diptera: Simuliidae) as a vector of Onchocerca volvulus (Leuckart) (Spirurida: Onchocercidae) in the forest zone of central Ghana was studied in the Upper Denkyira district, where onchocerciasis is hyperendemic. Simulium sanctipauli was found to be a highly efficient vector, with a mean of 377 infective (L3) larvae in the heads of 1000 parous and 122 in the heads of 1000 biting flies. The overall infection rate of 44% of the parous flies with L1, L2 and L3 stages of O. volvulus (identity confirmed by polymerase chain reaction) demonstrates marked anthropophily. Female flies dispersed over a wide area and can transmit onchocerciasis up to at least 10 km away from their breeding sites. Annual community-directed treatments with ivermectin did not have a noticeable effect on the infection rates and parasitic loads of fly populations, which were as high 2 months after as 3 months before the distribution of ivermectin. This failure can be attributed to poor coverage, with treatment taken by only 24.4% of the population of the six study villages.

Animals↗
PubMed2000

Molecular identification and phylogeny of East African Simulium damnosum s.l. and their relationship with west african species of the complex (Diptera: Simuliidae).

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.

Africa↗
PubMed2000

Dispersal range of Simulium neavei in an onchocerciasis focus of western Uganda.

The dispersal range of the vector Simulium neavei Roubaud (Diptera: Simuliidae) was investigated in an onchocerciasis focus in Kabarole district, western Uganda, adjacent to the Itwara Forest Reserve, where the species breeds in phoretic association with the river crab Potamonautes aloysiisabaudiae (Nobili) (Decapoda: Potamonautidae). Biting rates were highest at the edge of the forest, but blood-seeking flies were collected up to a distance of about 4 km from the forest. Entomological data did not agree with the geographical distribution of onchocerciasis, which is hyperendemic in larger distances from the forest. The possible reasons are discussed.

Animals↗
PubMed1999

The Simulium damnosum complex in western Uganda and its role as a vector of Onchocerca volvulus.

The status of onchocerciasis vectors in the former Ruwenzori focus in western Uganda was re-examined some 15 years after control measures against Simulium damnosum s.l. were suspended. The four cytoforms S. kilibanum, 'Sebwe', 'Nkusi' and S. pandanophilum were found. While the nonanthropophilic 'Sebwe' was still widely distributed in rivers north, east and south of the Ruwenzori, the only anthropophilic species and vector, S. kilibanum, had disappeared from most of its former habitats and was now restricted to two limited foci, where high biting densities were encountered. It was still a vector south of the Ruwenzori (Kasese focus), where 15.4% of the parous flies were infected with larval stages of Onchocerca volvulus and 34 infective larvae were found in the heads of 1000 parous flies. In the second focus along the Mahoma and Nsonge rivers, a chromosomally highly polymorphic population of S. kilibanum had replaced the former vector S. neavei, but does not act as a vector. Only 2.3% of the parous females were infected and just 1 infective larva was found in the heads of 1000 parous flies.

Animals↗
PubMed1999

Morphometric characterization of members of the Simulium damnosum Theobald complex (Diptera: Simuliidae) from East and West Africa.

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.

Animals↗
PubMed1998

A new species of the Simulium damnosum complex from Uganda, and comparative morphology of the tarsal claws in females of this complex.

The female, male, pupa and larva of Simulium (Edwardsellum) pandanophilum sp. nov. (Diptera: Simuliidae) from western Uganda are described. Diagnostic features are the shape of the tarsal claws of females and, cytogenetically, new intraspecific inversions on chromosomes I and II. Simulium pandanophilum is assigned to the Simulium damnosum complex. Different tarsal claw shapes of West African members of the S. damnosum complex are also described.

Animals↗
PubMed1997

Reduced prevalence of onchocerciasis in Uganda following either deforestation or vector control with DDT.

To determine the prevalence of onchocerciasis in western Uganda following deforestation and vector control, three foci were re-examined 20 years after previous surveys. In the Ruteete focus Simulium neavei had apparently disappeared and the prevalence of onchocerciasis declined in adults from about 70% in 1971 to a standardised prevalence of 12% in 1992. An increase of population density together with extended deforestation was assumed as cause of this strong reduction. In Bugoye, a S. damnosum s.l. focus, the standardised prevalence of microfilaria carriers declined from 62% in 1972 to 4.7% in 1992. Entomological data indicated the absence of man biting blackflies in the nineties. It can be suggested that the vector control using DDT performed during the seventies had lead to a change of the species composition from anthropophilic to non-anthropophilic S. damnosum s.l. In the focus Kicheche environmental changes were insignificant, deforestation was not progressive and S. neavei was abundant. Here the standardised prevalence of microfilaria carriers was still high (61%).

Adolescent↗
PubMed1997

PCR and DNA hybridization indicate the absence of animal filariae from vectors of Onchocerca volvulus in Uganda.

In order to identify Onchocerca volvulus larvae from vectors, DNA of filaria larvae from dissected blackflies was isolated, and a 150-bp long tandemly repeated DNA sequence (0-150), which occurs in many Onchocerca species, was amplified using polymerase chain reaction (PCR). Subsequently, the PCR product was blotted onto a nylon membrane and hybridized with DNA probes specific for O. volvulus or Onchocerca ochengi. Filaria larvae from 395 infected Simulium neavei were examined and 259 samples produced detectable PCR products. Among these samples, 239 (92%) reacted with an O. volvulus-specific oligonucleotide. A sample of 69 PCR products was tested using an O. ochengi DNA probe, but all failed to hybridize. Filaria larvae from 64 infected Simulium damnosum, presumably of the cytotypes "Nyamagasani" and "Nkusi" were studied and 0-150 was amplified from 38 samples. From these samples, 35 (92%) hybridized specifically with an O. volvulus probe but none with the O. ochengi-specific DNA sequence. Nonamplified samples were obtained mainly from blackflies that contained only 1 or 2 filaria larvae, and therefore, an insufficient DNA extraction was assumed. It can be concluded that few, if any, filaria species of animal origin were transmitted by S. neavei and S. damnosum s.l. in Kabarole and Kasese districts in Uganda.

Animals↗
PubMed1992

The vectorial efficiency of Simulium yahense populations in south-eastern Ghana.

Adult female Simulium yahense were identified amongst catches of S. damnosum s. 1. caught at Tsatsadu Falls and Wegbe in south-eastern Ghana. Dissections of stained flies to assess the species' role as a vector of onchocerciasis in the region revealed as many as 357 L3 per 1000 biting flies in a sample from Wegbe. When the data from the two sites were combined 154 L3 per 1000 biting flies and 315 L3 per 1000 parous flies were recorded. The values for wet season samples were about 12% higher than those for the dry season. The results are discussed in relation to other studies of S. yahense populations and regarding the species' recent spread in Ghana and Togo.

Animals↗
PubMed1991

A temporary focus of savanna species of the Simulium damnosum complex in the forest zone of Liberia.

Savanna species of the Simulium damnosum complex, the major vectors of the blinding savanna type of onchocerciasis, were considered to be rare in Liberia, until the dry season of 1988. In 1988 they became a serious nuisance, biting people at the Bong iron ore mine within the rain forest zone. S. damnosum s.str. and S. sirbanum were found breeding, in association with S. adersi a non man-biting savanna species, in a stream emerging from the mine's tailings pond. The local forest species were extremely rare in this stream. The water of the stream was characterized by an increased hardness and higher temperatures in comparison with those of natural watercourses in the area. The mass occurrence of flies was probably related to expansions of the tailings ponds, when rich nutrition was provided for the blackfly larvae by the decaying forests submerged by the rising water levels. The phenomenon did not recur in 1989 when only a few savanna flies were caught, and none were seen in the dry season of 1990. Although it is not known why the artificial environment of the tailings ponds was so attractive for the savanna species the events clearly demonstrated that savanna flies seasonally invading the area, possibly aided by the northeasterly harmattan winds, can become established in the rain forest zone if suitable conditions are met. No infections with Onchocerca volvulus were found in more than 1000 flies caught by vector collectors but, after experimental infection with the local forest strain, a few parasites developed to the infective stage. As yet there is no evidence that the occurrence of savanna flies in the rain forest zone of Liberia was of epidemiological significance.

Animals↗
PubMed1988

The relationship between innate susceptibility to Onchocerca, and haemolymph attenuation of microfilarial motility in vitro using British and west African blackflies.

The effect of haemolymph from individual flies of differing species of Simulium were compared in their ability to attenuate Onchocerca microfilariae in vitro. Small maintenance systems, each of 3-4 microliters total volume, were set up in Terasaki plates. Three British species of greatly differing susceptibilities to Onchocerca lienalis (Simulium ornatum, S. equinum and S. vernum) were compared in their effect on O. lienalis. Three forms of the S. damnosum complex from Liberia (S. yahense and 2 geographical variants of S. soubrense) were similarly compared in their effects on O. volvulus microfilariae. The more refractory species in both sets of experiments were found to significantly reduce the in vitro motility of the microfilariae more than the susceptible species. It is proposed that this innate variation in in vitro attenuation, may be caused be humoral haemolymph proteins. Such an assay, perhaps in a modified form could be used in predicting vector susceptibility. It could also be used to analyse mechanisms responsible for variation in susceptibility, of different S. damnosum complex members, to the geographical forms of O. volvulus.

Africa, Western↗
PubMed1988

Simulium (Edwardsellum) rasyani n.sp., the Yemen species of the Simulium damnosum complex.

The examination of the polytene chromosomes of the Yemen representative of the Simulium damnosum complex revealed hitherto unknown arrangements distinct enough to justify the description of this form as the new species Simulium (Edwardsellum) rasyani. The newly recognized inversion II L-60.65 was always present and found to be homozygous in 62% and heterozygous in 38% of the 106 larvae which were examined. A short description is given of the morphology of the females, males, larvae and pupae. Populations from the five permanent Wadis Kabir, Rasyan, Al Barh, Zabid, and Surdud were genetically and morphologically very uniform.

Animals↗
PubMed1987

The Beffa form of Simulium soubrense of the S. damnosum complex in Togo and Benin.

The Beffa form of Simulium soubrense Vajime & Dunbar, a member of the S. sanctipauli sub-complex of the S. damnosum complex, was found breeding throughout rivers in the Togo-Benin Gap, as far north as 9 degrees 30'N. Its distribution changed with the season. In southern Togo there were seasonal fluctuations in the relative abundancies of the Beffa form and of S. damnosum/S.sirbanum. There was considerable temporal and regional variation in the frequencies of different colour morphs of adult flies. The flies in Benin tended to be darker. Infections with Onchocerca volvulus (Leuckart) appeared to be independent of the host's colour morph category. Larger flies harboured significantly more first stage Onchocerca larvae but no significant relations with fly size were found for second and third stage larvae.

Animals↗
PubMed1987

Geographical distribution of Glossina palpalis gambiensis and G.p.palpalis in Liberia.

The two subspecies of Glossina palpalis (Robineau-Desvoidy) occurring in Liberia could be reliably separated morphometrically by measuring the width of the terminal dilatations of the male inferior claspers. Subspecies differentiation of female flies was less conclusive. Identification of flies from fifty-four sites revealed that most of Liberia lies in the belt of Glossina palpalis palpalis. However, pure and substantial populations of G.p.gambiensis Vanderplank occur north of 8 degrees 20'N in the north-west of Liberia.

Animals↗
PubMed1987

Infection rates and parasitic loads of Onchocerca volvulus, and other filariae, in Simulium sanctipauli s.l. and S. yahense in a rain-forest area of Liberia.

Simulium sanctipauli s.l. and S. yahense are common and widespread in the rain-forest zone of Liberia, but differ with regard to their biting densities and contribution to the transmission of Onchocerca volvulus. Although, in a study area on the St. Pauli River, S. sanctipauli s.l. (presumably S. soubrense in the sense of Post) was the predominant ma-biting species (74.3% of 30,855 females examined), S. yahense was shown to be the important vector. While 1000 biting females of S. yahense carried 96 3rd stage larvae indistinguishable from O. volvulus, only 14 were found per 1000 females of S. sanctipauli s.l. Of the parous females (3135 S. sanctipauli s.l./1621 S. yahense) 23.8/39.9% harboured 1st and/or 2nd stage filarial larvae and 1.9/9.4% 3rd stage larvae of O. volvulus. Animal filariae of unknown origin, indicative of zoophily, were very common in S. sanctipauli s.l. (13.8%) but practically absent from S. yahense (0.5%). In spite of its poorer vectorial performance S. sanctipauli s.l. cannot be neglected as a vector because it may occur in high biting densities and contribute considerably to the transmission, in particular in the vicinity of the St. Paul River. The interplay of two vector species, which develop in different types of water-courses explains the overall high endemicity of onchocerciasis in the study area.

Animals↗