Onchocerciasis

Automated retinal imaging and trend analysis - a tool for health monitoring

Most current diagnostic devices are expensive, require trained specialists to operate and gather static images with sparse data points. This leads to preventable diseases going undetected until late stage, resulting in greatly narrowed treatment options. This is especially true for retinal imaging. Future solutions are low cost, portable, self-administered by the patient, and capable of providing multiple data points, population analysis, and trending. This enables preventative interventions through mass accessibility, constant monitoring, and predictive modeling.

The potential of ivermectin to control the malaria vector Anopheles farauti

We investigated mortality in Anopheles farauti mosquitoes, a major coastal malaria vector in the south-west Pacific, fed on a volunteer who had taken a 250 micrograms/kg dose of ivermectin. High mortality was recorded in mosquitoes feeding during the first week after treatment of the volunteer, for instance 100-80% failed to survive 3 days. A long-term residual effect of ivermectin in the blood was indicated by a small but significantly higher mortality in mosquitoes fed 6 weeks after ivermectin was taken. These effects were included in malaria transmission models that incorporated host choice and host-induced mortality parameters. For the zoophilic An. farauti, ivermectin treatment of animals resulted in a greater reduction in malaria than ivermectin treatment of humans alone, whereas for an anthropophilic vector, treatment of humans was more important. This suggests that ivermectin treatment of animals could have an important role in malaria control where An. farauti is the vector. Improvement in the health of humans and domestic animals through control of parasitic worms and mites might encourage community participation in strategies involving ivermectin.

Prevalence of blindness and low vision of people over 30 years in the Wenchi district, Ghana, in relation to eye care programmes

A population based survey on the prevalence of major blinding disorders was conducted in the Wenchi district in central Ghana between March and May 1991. In 10 villages, 1425 people of 30 years and older were screened, using the WHO eye examination record. The prevalence of bilateral blindness above 30 years proved to be 1.7% (best acuity < 3/60): the prevalence of low vision above 30 years was 2.0% (best visual acuity 6/18 to 3/60). The causes of blindness were determined as cataract (62.5%), onchocerciasis (12.5%), corneal opacity (non-trachomatous) (8.2%), refraction anomalies (4.2%), phthisis bulbi (4.2%), optic atrophy (4.2%), and vascular retinopathy (4.2%). In the Wenchi district, 1.0% of the population over the age of 30 years was found to need a cataract extraction because of blindness of both eyes. Another potential 1.0% needs a cataract extraction because of low vision. A minor second study (n = 149) was undertaken in the same district, but in a village in an area near the Black Volta river in which onchocerciasis is endemic. The prevalence of blindness (8.1%) and low vision (3.4%) caused by onchocerciasis and cataract both proved to be higher. The survey provided the basis for a preventive and curative eye care programme.

Blindness in the tropics

Blindness is a major problem in most developing countries. It occurs at ten times the rate seen in the developed countries and in over 80% of cases is either preventable or curable. The four main causes are cataract, trachoma, onchocerciasis and xerophthalmia. Cataract, which is responsible for half the blindness, can be effectively cured with modern cataract surgery. Trachomatous blindness follows frequent episodes of reinfection, which can be prevented by simple hygienic measures. Onchocerciasis can be halted by the simple administration of a once-a-year dose of ivermectin, a drug which is currently being provided at no cost to all those with this infection. Vitamin A deficiency, which causes xerophthalmia, can be prevented by vitamin A distribution programs or dietary education. The challenge is to deliver these interventions effectively in the areas of need.

Quantal release of Ca2+ from intracellular stores by InsP3: tests of the concept of control of Ca2+ release by intraluminal Ca2+

A possible mechanism for the generation of 'quantal' release of intracellular Ca2+ by InsP3 (Muallem et al., J. biol. Chem. 264, 205-212 (1989)) has been put forward in which intraluminal Ca2+ levels modulate InsP3 receptor structure (Irvine, FEBS Lett. 263, 5-9 (1990)). Here we have modelled such a steady-state mechanism, with an InsP3-sensitive store plus an InsP3-insensitive one, to test its ability to mimic published data. We have also performed experiments on InsP3-stimulated rat liver microsomes to test whether the model is consistent with one-way Ca2+ fluxes at a steady state. The model can simulate quantal release, in that InsP3 produces a release of part of the stored Ca2+ which is initially rapid relative to the one-way flux. In the original form of the model, in which InsP3-modulated Ca2+ binding to the intraluminal site opens the Ca2+ channel, the range of InsP3 concentrations needed to release Ca2+ is greater than that observed. When the model is changed so that Ca2(+)-modulated InsP3 binding opens the channels, the effective InsP3 range is shortened, but the quantal release effect is reduced. Other published data on one-way fluxes, and our own data on microsomes, can be simulated when leakage from the InsP3-insensitive store is adjusted to fit the observations; these data therefore do not test the existence of a steady state in the InsP3-sensitive store. We conclude that sensitivity of Ca2+ release to intraluminal Ca2+ provides a steady-state explanation of most, but not all, current quantal release observations.(ABSTRACT TRUNCATED AT 250 WORDS)

Points of action in the campaign against blindness in developing countries

This article provides a survey of the problems of prevention of blindness in developing countries. The World Health Organization estimates that 31 million people are blind and 15 million people partially-sighted. The main cause of blindness is cataract. Other causes are trachoma, glaucoma, xerophthalmia, river blindness, corneal scars and leprosy. Prevention or treatment of these causes is possible in more than 80% of cases. The number of blind persons, however, is still increasing due to the increase in population and the immense shortage of all kinds of ophthalmological equipment and personnel. An effective strategy for the prevention of blindness in developing countries should focus on: more cheap cataract operations, increasing teaching facilities for ophthalmic personnel, integration of ophthalmic care into the general health system and the promotion of blindness prevention in political organizations.

2,5-Di-(tert-butyl)-1,4-benzohydroquinone mobilizes inositol 1,4,5-trisphosphate-sensitive and -insensitive Ca2+ stores

In permeabilized rat hepatocytes a maximal concentration (25 microM) of 2,5-di-(tert-butyl)-1,4-benzohydroquineone (tBuBHQ) mobilized 70% of sequestere Ca2+ and a half-maximal effect was produced by 1.7 microM tBuBHQ. Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) stimulated release of about 40% of the intracellular Ca2+ stores. Combined applications of a range of tBuBHQ concentrations with a maximal concentration of Ins(1,4,5)P3 demonstrated that tBuBHQ has slight selectivity for the Ca2+ transport process of the Ins(1,4,5)P3-sensitive stores. We conclude that the Ins(1,4,5)P3-sensitive stores are a subset of those sensitive to tBuBHQ and that the latter is therefore unlikely to prove useful as a tool to discriminate Ins(1,4,5)P3-sensitive and -insensitive Ca2+ stores though it may provide opportunities to design more selective agents.