Biomedical subjects

R Garms

Publications and source records attributed to R Garms.

53 records · Page 3Linked to original sources

PubMed1977

Lethal damage to Simulium metallicum following high intakes of Onchocerca volvulus microfilariae in Guatemala.

High intakes of microfilariae of a Guatemalan strain of Onchocerca volvulus by Simulium metallicum proved lethal to a considerable proportion of the flies within 24 hours of taking an infecting blood-meal. The gross histopathological changes resulting from infection were compared in groups of moribund and of apparently healthy flies during this period. The marked morbidity of the flies could be related to certain events occurring in the alimentary tract and haemocoele of the fly soon after ingestion of the parasitized blood. The rapid death of the flies may be ascribed to one or more of the following reasons: (i) reverse migration of numerous microfilariae from the expanded- to the tubular-part of the mid-gut, where they cause serious injury and disintegration of the gut epithelium; (ii) abrasive damage to the stomach epithelial cells by the invading microfilariae with occasional release of the gut contents into the haemocoele; (iii) interruption of the formation of the peritrophic membrane, particularly at its anterior and posterior ends, with subsequent failure of the flies to digest the blood in the stomach; (iv) passage of large amounts of parasitized blood from the stomach backwards into the hind-gut, leading to its mechanical obstruction and (v) invasion and injury of various organs of the fly, among them the ventral nerve-cord, brain, optic nerve, eye, halteres, fat-body and flight musculature by excessive numbers of microfilariae.

Animals↗

PubMed1975

Observations on filarial infections and parous rates of anthropophilic blackflies in Guatemala, with reference to the transmission of Onchocerca volvulus.

In Guatemala, in areas of different onchocerciasis endemicity and outside the endemic zone, the main anthropophilic blackfly species Simulium ochraceum, S. metallicum, S. callidum and S. gonzalezi were examined for infections with Onchocerca volvulus, other filariae, and non-filarial parasites. Third stage larvae, indistinguishable from those of O. volvulus were found only in 3 females of S. ochraceum out of 3,513 examined. In S. metallicum, 2 females out of 3,121 dissected harboured infective larvae of another filaria species, morphologically different from O. volvulus. Thoracic infections were encountered in all four Simulium species. Only in S. ochraceum was there a correlation between the infection rates in the human and in the fly populations. In the endemic zone, up to 15% of the parous flies were infected, against none in the non-endemic area. Parous S. metallicum showed low over-all infection rates of 0.6 to 2.6%, and had infections also outside the endemic zone, but these could not have been of human origin. Non-filarial infections, including fungi of the ovaries, ciliates, mermithids, nematodes, were commonly observed in Guatemalan blackflies. Parous rates were 40% in S. ochraceum, 23% in S. metallicum, 39% in S. callidum, and 49% in S. gonzalezi. The size of the follicular relics showed a daily cycle in S. ochraceum. They were usually large in flies biting man in the afternoon, but small in flies biting in the morning. This suggests that the flies found a new host the same day, or the morning after they had deposited their eggs.

Animals↗

PubMed1975

The fate and migration of microfilariae of a Guatemalan strain of Onchocerca volvulus in Simulium ochraceum and S. metallicum, and the role of the buccopharyngeal armature in the destruction of microfilariae.

The migration and fate of microfilariae of a Guatemalan strain of Onchocerca volvulus in Simulium ochraceum and S. metallicum was studied. The anatomical distribution of microfilariae at various times after ingestion was recorded from a study of histological sections of the flies. S. ochraceum showed higher microfilarial intakes than S. metallicum which is probably attributed to an inherent difference in their ability to ingest. The migration of microfilariae out of the mid-gut took place essentially through the expanded part (the stomach). Despite the high microfilarial intakes by S. ochraceum, only a few microfilariae were able to migrate successfully into the thorax (2.6%) whereas in S. metallicum showing a low microfilarial intake, a higher rate of migration was noted (74.5%). The main bulk of microfilariae ingested by S. ochraceum died and disintegrated in the stomach. This was due to the presence of a well-developed cibarial armature in the buccopharyngeal apparatus of S. ochraceum in contrast to S. metallicum where such an armature is lacking. Microfilariae were severely damaged by the cibarial teeth while en route to the stomach. They rapidly underwent profound changes in morphology and staining properties and were often surrounded by clusters of the phagocytic leucocytes in the blood mass. In some flies, microfilariae, apparently damaged, were still entangled in the cibarial teeth 5 minutes to 3 hours after taking a blood-meal.

Animals↗

PubMed1975

On the ecology and distribution of the species of the simulium damnosum complex in different bioclimatic zones of Liberia and Guinea.

A chromosomal identification of Simulium damnosum material collected in Liberia and Guinea revealed five species of this complex. S. yahense Vajime and Dunbar: Widely distributed in the rain forest zone (Liberia, Southern Guinea) and in the Fouta Djallon mountains. Breeding places typically in small watercourses, shaded streams and narrow rivers. S. sanctipauli Vajime and Dunbar: Restricted to the rain forest zone. Breeding confined to large rivers. S. soubrense Vajime and Dunbar: Breeding established in large and medium rivers under high forest (Liberia) and in the Guinea savanna (head waters of the Niger and its southern tributaries). S. damnosum Theobald: Distributed in the forest zone and Guinea savanna. Breeding in rivers and irrigation systems. S. sirbanum Vajime and Dunbar: Confined to the Northern Guinea savanna. Breeding in rivers and irrigation plants, occasionally in streams arising from lakes. Larvae of S. yahense and S. sanctipauli could be separated by morphological characters. The associations with other blackfly species are discussed.

Animals↗

PubMed1974