Consequences of vector behavior in epidemiology of onchocerciasis on the Firestone Rubber Plantation in Liberia.

In the current study, we have assessed the distribution of black fly vectors and the occurrence of onchocerciasis among residents of the Firestone Rubber Plantation (FRP) in Liberia. The degree of endemicity of onchocerciasis on the FRP is correlated with the breeding of Simulium yahense on the Du River and Simulium soubrense on the Farmington River, as well as with the feeding behavior of these black fly vectors. S.

Development of Onchocerca volvulus (Filarioidea: Onchocercidae) in the West African black fly Simulium yahense (Diptera: Simuliidae) in Liberia.

Simulium yahense black flies infected with microfilaria of Onchocerca volvulus were kept in a defined insectary environment in Liberia, West Africa. A daily sample of infected flies was dissected for larvae developing in the thoracic muscles and examined for growth in stadial development. Microfilariae ingested by black flies transformed to the L1 larval stage without molting.

The Johns Hopkins University School of Hygiene and Public Health, Lloyd E. Rozeboom mosquito collection.

The Lloyd E. Rozeboom mosquito collection from the Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD, has been transferred to the National Museum of Natural History, Smithsonian Institution, Washington, DC. This historically and taxonomically important collection has specimens representing 32 genera, 78 subgenera, and 763 species from most mosquito faunal areas of the world.

Brugia malayi microfilariae (Nematoda: Filaridae) enhance the infectivity of Venezuelan equine encephalitis virus to Aedes mosquitoes (Diptera: Culicidae).

We examined the potentially conflicting effects that microfilarial (MF) enhancement of viral infectivity and MF-induced mortality in mosquitoes have on the vectorial capacity of Aedes aegypti (L.), Aedes triseriatus (Say), and Aedes taeniorhynchus (Wiedemann) for Venezuelan equine encephalitis virus (VEE) when mosquitoes feed on gerbils co-infected with Brugia malayi (Buckley). Groups of mosquitoes were fed on gerbils that were either dually infected (VEE plus B.

Ultrastructure of infective larvae (L3) of Onchocerca volvulus (Nematoda: Filarioidea) developed in Simulium yahense in Liberia.

Third-stage infective larvae of Onchocerca volvulus were examined to elucidate the ultrastructure and the interrelations of the stoma, esophagus, intestine, and nervous system. The alimentary canal involves a cuticularized stoma with a triradiate lumen that is continuous with a similar triradiate lumen in the muscular region of the esophagus. The lumen wall may be laterally appressed or opened into a stellate form in the glandular region.

Ophthalmomyiasis interna posterior. Report of a case with optic atrophy.

Purpose: The prognosis for patients with ophthalmomyiasis Interna posterior is variable. In many patients the larva remains in the eye for years without inducing inflammation or loss of vision. Sometimes, however, the migrating larva involves the macula and optic nerve and results in permanent visual loss or even blindness.

Onchocerca volvulus: parasitologic and serologic responses in experimentally infected chimpanzees and mangabey monkeys.

Six chimpanzees (Pan troglodytes) and six mangabey monkeys (Cercocebus atys) were inoculated with Onchocerca volvulus third-stage larvae (L3) of West African origin. Two chimpanzees each received 200, 300, or 400 L3, while three mangabeys each received either 50 or 250 L3. All six chimpanzees became microfilaria positive between 11 and 25 months postinoculation (PI), while two of the six mangabeys were skin-snip positive at 24 and 37 months PI, respectively.

Estimates of population size, dispersal, and longevity of domestic Aedes aegypti aegypti (Diptera: Culicidae) by mark-release-recapture in the village of Shauri Moyo in eastern Kenya.

Estimates of the absolute size of a domestic population of Aedes aegypti aegypti (L.) were made in the Rabai area of Kenya, based on a single release, followed by either single or repeated recaptures. From single recapture within 24 h of release, the size of the female Ae.

Aedes (Gymnometopa) mediovittatus (Diptera: Culicidae) as an experimental vector of Brugia pahangi and B. malayi (Spirurida: Filariidae).

To test the susceptibility of Aedes (Gymnometopa) mediovittatus to infection with Brugia pahangi and Brugia malayi, females originating from the suburbs of San Juan, Puerto Rico, were fed on infected gerbils (Meriones unguiculatus). On average, 39.2% of the Ae.

Diurnal biting activity and transmission of Onchocerca volvulus (Filariata: Onchocercidae) by Simulium yahense (Diptera: Simuliidae) in Liberia.

To determine the influence of meterological factors on the diurnal biting cycle of Simulium yahense Vajime & Dunbar (a member of the Simulium damnosum Theoblad complex), we captured host-seeking females as they landed on the exposed lower legs of humans in the Harbel area of Liberia. Biting activity was greatest during the morning hours and was characterized by a unimodal harmonic curve. Although meteorological conditions had no decisive influence on the unimodal pattern of diurnal biting activity, hourly variation in the number of S.

Induction of protective immunity against larval Onchocerca volvulus in a mouse model.

BALB/cBYJ mice were immunized against larval Onchocerca volvulus by subcutaneous injection of normal, irradiated, or freeze-thaw-killed Onchocerca sp. larvae. The mice received challenge infections of O.

Cryopreservation of infective larvae of Onchocerca volvulus (Filarioidea: Onchocercidae).

Infective larvae (L3) of Onchocerca volvulus were procured in Liberia, West Africa, in the natural black fly vector, Simulium yahense. A cryobiological technique was developed to preserve L3 of O. volvulus that were fully viable after thawing.

Survival and development of larval Onchocerca volvulus in diffusion chambers implanted in primate and rodent hosts.

Third-stage larvae (L3) of Onchocerca volvulus were implanted in diffusion chambers in chimpanzees, mangabey monkeys, rhesus monkeys, squirrel monkeys, and inbred strains of mice, jirds, and rats for 3-63 days. At different times during the experimental period, larvae were recovered and assessed for their viability and development. Survival and growth rates were equal regardless of whether the implanted larvae were fresh or cryopreserved.

Duration of larval development of Simulium yahense (Diptera: Simuliidae) under natural conditions.

The duration of Simulium yahense Vajime & Dunbar larval development on a dam spillway in Harbel, Liberia, was observed to make accurate decisions regarding the frequency of larvicide treatments against this onchocerciasis vector. Larval development required a minimum of 10-12 d from eclosion to first pupation. Initial larvicidal treatment for S.

Onchocerciasis in the forest-savannah mosaic region of Sierra Leone. Prevalence, intensity of infection, and endemicity levels.

The present study was carried out between December 1986 and January 1988. A series of 3,048 individuals (46% males and 54% females) were examined in 56 villages; onchocercal dermatitis and lymphadenitis were seen. The crude prevalence of nodules and of microfilariae amounted to 14% and 43%, respectively.

Effect of mass treatment of a human population with ivermectin on transmission of Onchocerca volvulus by Simulium yahense in Liberia, West Africa.

The impact of mass treatment with ivermectin on the intensity of Onchocerca volvulus transmission by the black fly (Simulium yahense) was evaluated on the Liberian Agricultural Company rubber plantation in Liberia, West Africa. The adult pre-treatment prevalence of onchocerciasis was greater than 80%, and the average intensity of infection was 5.35 mf/mg of skin.

Ivermectin prophylaxis against experimental Onchocerca volvulus infection in chimpanzees.

Ivermectin was tested for possible prophylactic action against the third and fourth larval stages (L3 and L4) of Onchocerca volvulus inoculated into chimpanzees. The infective larvae (L3) were obtained from laboratory-raised black flies. Eighteen chimpanzees were inoculated, each with approximately 250 L3.

Large scale production of the vertebrate infective stage (L3) of Onchocerca volvulus (Filarioidea: Onchocercidae).

Laboratory-derived Simulium yahense and S. sanctipauli females were used to produce large numbers of Onchocerca volvulus infective stage larvae (L3) for use in assessing the possible chemoprophylactic potential of ivermectin in the chimpanzee model. Engorgement rates and subsequent post-prandial survival were correlated with the time at which adult flies were offered a carbohydrate source following emergence and the age of flies that fed on microfiladermic volunteers.

Population relationships of Simulium yahense and Simulium sanctipauli in the Firestone Rubber Plantation at Harbel, Liberia.

Comparative genetic differences for the phosphoglucomutase and trehalase loci were surveyed in larval and adult blackfly populations of the onchocerciasis vectors Simulium yahense Vajime and Dunbar, and S.sanctipauli Vajime and Dunbar. Genotype frequencies for each stage and all populations were at Hardy-Weinberg equilibrium, indicating that S.

The effect of Brugia pahangi infection on survival of susceptible and refractory species of the Aedes scutellaris complex.

Life table statistics were used to examine the survival functions of filarial susceptible and refractory species of the Aedes scutellaris (Walker) group of mosquitoes, following infection with high and moderate doses of Brugia pahangi (Buckley & Edeson). Survivorship curves and hazard function curves were generated, and the median survival times and the proportions of mosquitoes surviving beyond the extrinsic incubation period of the parasite were determined. In the susceptible populations of Aedes polynesiensis Marks, Ae.

Quantitative studies of onchocerciasis transmission by Simulium yahense and Simulium sanctipauli in the Firestone Rubber Plantation at Harbel, Liberia.

Black fly vectors of onchocerciasis from three ecologically different Simuliid breeding habitats in the Firestone Rubber Plantation at Harbel, Liberia, were surveyed by human-biting collections conducted at weekly intervals over a 13-month period. Black flies were identified morphologically and the monthly and seasonal contribution of different vector species to the transmission of Onchocerca volvulus at each site was determined. Simulium yahense was identified as the predominant vector species at each site.

Dispersal and other population parameters of Aedes aegypti in an African village and their possible significance in epidemiology of vector-borne diseases.

Dispersal of Aedes aegypti aegypti adults within Shauri Moyo, an African village in the Rabai area north of Mombasa, Kenya, was studied using the mark-release-recapture method. A total of 920 mosquitoes were captured and uniquely marked, of which 828 (90%) were released and 332 (40%) recaptured. A great majority of mosquitoes were recaptured once, but some individuals were recaptured up to 10 times.

Identification of larval and adult Simulium yahense and Simulium sanctipauli based on species-specific enzyme markers and their distribution at different breeding habitats in Central Liberia.

Human-biting adults and late instar larvae of the Simulium damnosum complex from four ecologically different simuliid breeding habitats in the Firestone Rubber Plantation at Harbel, Liberia, were identified morphologically and the monthly species composition of each site was recorded. Samples of the predominant species found at each site were assayed electrophoretically for species-specific variants of phosphoglucomutase (PGM) and trehalase (TRE). Enzyme identifications of flies and larvae were compared with morphological identifications to determine the accuracy of field identifications relying upon morphological characters.