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PubMed1988

Effect of single-dose ivermectin therapy on human Onchocerca volvulus infection with onchocercal ocular involvement.

Ivermectin has shown promise as a potentially safe and effective microfilaricidal drug for the treatment of onchocerciasis. Several limited studies have shown it to have fewer side effects, especially ocular complications, than the currently available drug, diethylcarbamazine. The detailed ocular findings in 200 moderately to heavily infected Liberians who were enrolled in a safety and dose-finding study are presented. They received either 0, 100, 150, or 200 micrograms/kg of ivermectin and were followed up for 12 months. In clinical studies so far carried out ivermectin in a dose of 100, 150, or 200 micrograms/kg has not been associated with any major adverse reactions nor were there any sight-threatening effects even in the presence of severe ocular disease. Each of these doses significantly reduced the ocular microfilaria load for at least 12 months when compared with either the placebo (p less than 0.05) or pretreatment values (p less than 0.001). However, the 100 and 150 micrograms/kg doses caused fewer minor side effects than the higher dose. These results confirm that ivermectin in a single oral dose may be a safe and effective microfilaricidal drug for the treatment of onchocerciasis and that it appears to be free of major ocular side effects.

Adolescent↗
PubMed1976

Transmission in utero of microfilariae of Onchocerca volvulus.

Skin snips from newborn children and biopsy material from the umbilical cord and placenta of their mothers were examined. Microfilariae of O. volvulus were found in the skin of 2 out of 11 babies and in the umbilical cords of 2 out of 11 babies born to ten mothers infected with O. volvulus in Bawku Hospital, Ghana.

Female↗
PubMed1975

The geographical distribution of Onchocerca volvulus infection in Liberia.

The survey carried out for the assessment of onchocerciasis prevalence in Liberia from 1968 to 1971 covered about 1% of the rural population. From 10.885 persons examined parasitologically, 38% were carriers of microfilariae of O. volvulus in the skin, and an additional 6.8% carried nodules but no mf. One or more onchocercal nodules were prevalent in a total of 27% of the population. Geographic and sex differences were observed as well as several different patterns of increasing age. A description of the geographic distribution patterns is given but evaluation of population clusters classified by overall endemicity is considered more profitable for analyses of parasitological and clinical lesions related to the transmission of the filarial infection. Regional differences of the age-adjusted mf-rates ranging from 0 to 78% prevalence were obtained from the analysis of 121 communities throughout the country. The general onchocerciasis distribution pattern showed the highest endemicity in the western part of the country with a general decline towards hypoendemic condition in the Eastern regions. Exceptions were found in that sizable pockets of high transmission activity seems to exist in Eastern Liberia near the coast and also in Central Liberia.

Adolescent↗
PubMed1975

The Onchocerca volvulus transmission potentials and associated patterns of onchocerciasis at four Cameroon Sudan-savanna villages.

The intensity of O. volvulus infection, and the prevalence of certain eye lesions and of blindness, are compared in 4 hyperendemic Cameroon Sudan-savanna villages. The pattern of the disease is related to the annual transmission potentials to which the communities were exposed, and the results are compared with those obtained previously in forest villages. The prevalence and intensity of O. volvulus infections in S. damnosun were more closely related to the prevalence of positive skin snip than to the mean concentrations of microfilariae in the skin. Owing to the differential dispersal of nulliparous and parous flies in savanna, the annual transmission potentials were related more closely to the numbers of parous flies than to the total fly population. Factors governing the exposure of persons to infective flies are discussed. Seasonal transmission, which was usually light, did not lead to severe onchocerciasis; the more perennial the transmission the heavier was its degree, and the more prevalent were eye lesions and blindness. Annual transmission potentials of about 500, 1750, 1800+ and 2900 were associated with an increase in the mean intensity of infection and in the prevalence of eye lesions, while the onchocerciasis blindness rate in persons over 20 years old rose from nil to 3.3, 9.2 and 10 per cent respectively. Annual transmission potentials of 4400 and 19000 were recorded on the banks of S. damnosum breeding rivers in the area, but no villages were sited at such places and it is probable that no community could survive under such conditions. The bearing of these findings on the anticipated effects of S. damnosum control operations in savanna is discussed.

Animals↗
PubMedDate not supplied

[Entomology of onchocerciasis in Soconusco, Chiapas, México. VII. Quantitative variations in the transmission of Onchocerca volvulus (Nematoda: Filaroiidea) according to human activity space].

In this research we tried to demonstrate differences in transmission intensities of onchocerciasis by Simulium ochraceum in the community of Golondrinas, Municipality of Acacoyagua in the Soconusco area of the state of Chiapas. Adult females of this species were captured in the center of the villages, the coffee plantation, and the corn bean planted plots, during 7 to 10 consecutive days of the months of June, August, November and December of 1983, and January, March, and May of 1984. Captures were made from 7:00 to 11:00 h, by two persons (a human bait and a collector) in each of the mentioned areas. Variations in densities of S. ochraceum were not statistically significant among the different areas, although there was a predominance in the center of the villages during all the time periods. There was not a statistical significance in the number of oviparous females, although again the center of 50 villages showed the highest percentages (43.5%), as compared to the coffee plantation (37.8%), and the corn-bean plots (33.8%). Regarding the ratio infection: infectivity, only the infective mosquitoes with L3 showed a statistical significance in the three types of areas, being highest in the center of the villages. Transmission potentials were: center of the village 28.5 L3/human/period; coffee plantation, 73 L3/human/period; corn-bean plot, 5.8 L3/human/period. We discuss the possibility that the differences in densities among the various areas might depend on the variations of the breeding sites, mobility or permanence of the individuals during the hours of greater activity of S. ochraceum, and the wind and light local conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMedDate not supplied

[Problems in the investigation of the control of Onchocerca volvulus in Mexico].

The treatment and control of onchocerciasis in Mexico has been supported only on the administration of diethylcarbamazine and the removal of adult worms, which are in the onchocercomata. These actions seems to have diminished the prevalence and incidence of blindness in those individuals who are affected by this parasitosis. However, there has not been an important impact on onchocerciasis transmission. The objective of this paper is to critically analyze and discuss subjects related to diagnosis, treatment and control of onchocerciasis transmission in Mexico. Chemical vector control has been successfully achieved in other world regions; however, in Mexico, it has not been fully accepted as part of the integral onchocerciasis control due to several causes. Moreover, there has been few scientific research activities toward the search of new options for vector control. Recently, results of research on ivermectin (a microfilaricide agent) have indicated that this drug is effective and safe for the treatment of onchocerciasis. Additionally, it has been reported that ivermectin has an effect on the onchocerciasis transmission. However, there are several unanswered questions about the efficacy of ivermectin in stopping onchocerciasis transmission. In this report, the main efforts carried out in Mexico against onchocerciasis are analysed and problems related with diagnosis, treatment and control are also discussed. Some parameters for the correct evaluation of onchocerciasis control, with entomological emphasis, are proposed.

Entomology↗
PubMed1986

Geographical distribution of the prevalence of nodules of Onchocerca volvulus in Guatemala over the last four decades.

In Guatemala a national nodulectomy campaign has been carried out since 1935 in three operational areas, namely the Eastern, Central and Western endemic zones. The prevalence of nodules was calculated in each 1 km grid square in these zones in each decade and plotted on mesh maps. A total of nine foci of high endemicity, three in each operational area, was found in the decade 1940-49. Nodule prevalence was concentric in each endemic focus; high in the centre and gradually falling towards periphery. The foci were found mainly on Tertiary or Quaternary-Tertiary volcanic rocks in the Eastern and Central zones, or on non-carbonate sedimentary rocks in the Western zone. Nodule carriers were found at altitudes from 220 to 2200 m above sea level. The altitude of the foci of high endemicity varied, being low in the Eastern zone, medium in the Central zone and high in the Western zone. The nodule prevalence declined from the decade 1940-49 to the decade 1970-79 in most of the grid squares. The Santa Rosa focus in the Eastern zone virtually disappeared before 1970. The extent of endemic area having a nodule prevalence of 1% or higher decreased from 2384 km2 in the decade 1940-49 to 1424 km2 in the decade 1970-79. The area recommended for vector control operation against Simulium ochraceum was estimated at 803 km2.

Altitude↗