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PubMed1985

Human macrophages and T-lymphocyte subsets infiltrating nodules of Onchocerca volvulus.

The nature of the lymphoid infiltrate in nodules of Onchocerca volvulus was assessed using monoclonal antibodies to lymphoid cell surface markers. Although B cells were generally absent, T cells were present, but in variable amounts. The ratio of T4+ (helper phenotype) to T8+ (suppressor-cytotoxic phenotype) was usually in the normal peripheral blood range of about 3, although ratios ranging from 1 to 10 were seen in selected areas of the onchocercoma. The possibility of immunosuppression through dominance of T4+, Leu-8+ cells (suppressor-inducer phenotype) within the T4+ population was also excluded. The T cells did not tend to concentrate in close proximity to the parasite, and there was no general bias in favour of the T suppressor cell phenotype (T8) within the infiltrate. Macrophages and dendritic cells were consistently observed and consisted of three defined cell types in approximately equal proportions: normal, unactivated macrophages (HLA-DR-, acid phosphatase positive), activated macrophages (HLA-DR+, acid phosphatase positive) and cells of dendritic morphology (HLA-DR+, acid phosphatase negative). These results are discussed in relation to immune suppression in filariasis.

Antibodies, Monoclonal↗
PubMed1968

The intake and transmissibility of Onchocerca volvulus microfilariae by Simulium damnosum fed on patients treated with Diethylcarbamazine, suramin or Mel W.

The best hope for the control of transmission of Onchocerca volvulus over much of Africa lies in combining larvicidal measures directed against the Simulium vectors with chemotherapeutic measures designed to reduce the reservoir of transmissible microfilariae in man.There are few drugs effective against O. volvulus. Diethylcarbamazine kills the microfilariae but has virtually no effect on the adult worms. Suramin kills adult worms and many, but not all, of the microfilariae. Mel W kills adult worms but has little or no action on microfilariae. All these drugs suffer at present from disadvantages of toxicity, which tend to limit their use on a mass scale in the field. Nevertheless, before they, or indeed any new drugs with similar actions on the parasites, can be used intelligently for the control of onchocerciasis transmission, it is necessary to have accurate quantitative information on the effect that each of them has on the microfilarial population available for intake by Simulium, as well as on their actions on the developmental potential of those microfilariae ingested by the flies.The present paper describes the effects of treatment with various courses of diethylcarbamazine, suramin or Mel W on the numbers of microfilariae ingested by groups of S. damnosum and on the numbers of infective larvae developing therefrom.

Arsenicals↗
PubMed1970

The effects of drugs on Onchocerca volvulus. 4. Trials of melarsonyl potassium.

The effects of the arsenical drug melarsonyl potassium on Onchocerca volvulus were investigated in patients in Cameroon infected with the Cameroon forest and Sudan savanna strains of the parasite. Two intramuscular dosage schedules were tested: the first comprised 4 consecutive daily doses of 200 mg repeated once after a 10-14 day interval, i.e., 2 (4x200 mg). The second was a single dose schedule at 7.1 mg/kg-10 mg/kg, with a maximum of 500 mg.In most trials the drug had no immediate action on microfilarial concentrations. Only after the 2(4x200 mg) melarsonyl course against the Sudan savanna strain was a slight microfilaricidal action detected.The 2(4x200 mg) course of melarsonyl apparently killed or sterilized most or all of the adult female worms in the patients tested, leaving the residual population of microfilariae to decline gradually, from natural mortality, over the ensuing 2 years. These residual microfilariae could be killed with diethylcarbamazine.Single doses of melarsonyl at 7.1 mg/kg-10 mg/kg were somewhat less effective in killing or sterilizing adult worms, but it is suggested that if doses at the higher end of this range were to be repeated annually patients could be rendered free from microfilariae by the end of 3 years.It is emphasized that the risks of arsenical encephalopathy should at present preclude the use of melarsonyl potassium in the treatment of onchocerciasis, but that if this danger could be avoided the drug might prove to be of considerable use for mass therapy in control campaigns.

Adolescent↗
PubMed1980

Studies on Bancroftian filariasis in Liberia, West Africa. IV. Notes on side effects observed during a diethylcarbamazine treatment campaign in a rural area endemic for Wuchereria bancrofti and Onchocerca volvulus.

464 persons of whom 189 proved to be infected with microfilariae of Wuchereria bancrofti and/or Onchocerca volvulus were examined for adverse reactions due to diethylcarbamazine, which was administered during a filariasis control campaign. Persons older than 20 years of age were significantly more affected than younger persons and men showed distinctly more side effects than women. The most frequent complaints were skin reactions followed by gastrointestinal complications. The significantly highest rate of adverse reactions was observed in persons being infected with microfilariae of O. volvulus, whereas no significant difference was registered between side effect rates of bancroftian microfilaria carriers and non-infected persons. It is concluded that in areas where both filarial species are endemic, infections with O. volvulus are a limiting factor for the control of bancroftian filariasis by means of mass treatment with diethylcarbamazine.

Adolescent↗
PubMed1978

Survey for infection with Onchocerca cervicalis in horses in eastern United States.

This survey was performed to study the prevalence of infection with Onchocerca cervicalis in horses in the eastern United States. In the course of the survey, 121 horses, 1 mule and 1 donkey were examined. Microfilariae were recovered from 74 (61%) of the horses examined. All infected horses showed microfilariae of O cervicalis in the umbilical sample, 62 (84%) were infected in the eyelid and, in 36 (49%), microfilariae had invaded the eye. The mule was unifected and the donkey was infected with O cervicalis.

Animals↗
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↗