[Field studies on different control schemes for hookworm infection].

Three different control schemes including selective chemotherapy, a combination of selective chemotherapy and management of fecal disposal and mass treatment with mebendazole-medicated salt were implemented for the control of hookworm infection in Luwo Town and Taiping Village, Wuming County, Guangxi Zhuang Autonomous Region during 1971-1990. Through ten years of selective chemotherapy, the results showed that the hookworm infection rate dropped from 42.6% to 3.9% and the infection intensity from 425.6 eggs per gram faeces to 1.6 eggs per gram faeces. After seven years of selective chemotherapy combined with management of fecal, the hookworm infection rate dropped from 58.7% to 10.9% and the infection intensity from 111.5 eggs per gram faeces to 8.5 eggs per gram faeces. However, 3 years after the termination of the combined treatment, the hookworm infection rate increased to 14.5%. As for the implementation of the third scheme, mebendazole-medicated salt was given at 100 mg daily for 30 consecutive days or at 50 mg daily for 30 consecutive days. Stool examination was made one year after the treatment, the results showed that the infection rate of the inhabitants dropped from 36% and 36% to 2% and 1.3%, respectively, and the infection intensity dropped from 110.3 and 246 eggs per gram faeces to 1.3 and 0.24 eggs per gram faeces. After three years, the infection rate of inhabitants remained under 2% and the infection intensity under 1 egg per gram faeces. It was concluded that mass treatment with mebendazole-medicated salt might be the most practical scheme for the control of hookworm infection.

Evaluation of albendazole, pyrantel, bephenium, pyrantel-praziquantel and pyrantel-bephenium for single-dose mass treatment of necatoriasis.

An effective drug for single-dose mass treatment of necatoriasis was sought by testing three drugs and two drug combinations in Ethiopian immigrants to Israel found to have light infections. The drugs tested sequentially in single-doses were pyrantel pamoate (20 mg kg-1, 81 subjects); bephenium hydroxynaphthoate (2.5-5 g, 65 subjects); combined pyrantel and bephenium (25 subjects); combined pyrantel (20 mg kg-1) and praziquantel (40 mg kg-1) (16 subjects); and albendazole (400 mg, 77 subjects). Follow-up under conditions without likelihood of reinfection was by one stool examination. Cure rates with albendazole, pyrantel-bephenium and pyrantel-praziquantel were 84, 80 and 81% respectively; these rates were significantly higher than the 49% found for bephenium and the 51% for pyrantel (P less than 0.05). Egg reductions in those not cured were pyrantel (22%), bephenium (6%), pyrantel-bephenium (34%), pyrantel-praziquantel (3%) and albendazole (6%). Albendazole was the most promising single drug treatment; unexpected was the high effectiveness of pyrantel-praziquantel in combination.

Response of preadult Necator americanus to some known anthelmintics in hamsters.

Hamsters infected with laboratory-adapted preadult Necator americanus were dosed with 6 reference anthelmintics. Their efficacy was measured in terms of percentage cure of infected animals as well as percentage worm reduction following treatment. Mebendazole and pyrantel were equally effective in this system. Other anthelmintics, including anti-hookworm compound, bephenium hydroxynaphthoate, were less effective. The comparative results revealed that the N. americanus model is sensitive and reliable for identifying and characterizing new anti-parasite preparations.

Hookworm burdens and faecal egg counts: an analysis of the biological basis of variation.

The relationships between various measures of faecal egg output and hookworm burdens were investigated in 84 villagers from West Bengal with mixed Necator americanus and Ancylostoma duodenale infections. The pattern of day to day variability in egg counts from individuals can be characterized by the linear relationship between the logarithms of the variances and means. Egg output is shown to be non-periodic in long runs of day-to-day records. The distribution of worm numbers per host is well described by the negative binomial probability model, and the relationship between per capita egg output and worm burden is non-linear where egg output declines as parasite burden rises. Density-dependent effects on fecundity are shown to act at comparatively low worm burdens in relation to the range of observed parasite loads. Egg output measures are shown to be qualitative as opposed to quantitative measures of worm burdens as a consequence of inherent sampling heterogeneity and variability induced by biological processes, such as density-dependent depression of parasite fecundity. The analyses suggest that it is possible, on the basis of egg counts, to discriminate between individuals with low and high hookworm burdens. The intrinsic per capita fecundities of the two species of hookworms are shown to be similar, but density-dependent constraints on egg production by N. americanus appear to be more severe than those acting on A. duodenale. This observation may help explain why A. duodenale appears to produce larger numbers of eggs per unit of time than N. americanus. The regulatory role of density-dependent fecundity and aggregated distributions of worm numbers per person are discussed in relation to the over-all transmission dynamics of hookworm parasites.

Use of common salt fortified with iron in the control and prevention of anemia--a collaborative study. Report of the Working Group on Fortification of Salt with Iron.

The efficacy of salt fortified with iron (FePO4 and NaHSO4) to control anemia was investigated by large scale field trials in three rural areas and one urban area located in different parts of India, each covering a total population of 4000 to 6000. Hb levels were determined before the introduction of the fortified salt and at six monthly intervals thereafter. Iron-fortified salt was acceptable to the population and its consumption for a period of 12 to 18 months was without any untoward effects. At the end of 12 to 18 months of consumption of iron-fortified salt, a significant improvement in the Hb-levels and a significant reduction in the incidence of anemia was observed in all the test areas. In one of the rural areas tested, there was a high incidence of hookworm infestation and iron-fortified salt showed a significant impact on Hb levels even in this area. Deworming concomitant with distribution of iron-fortified salt was shown to have only a marginal additional benefit.

Controlled comparative study of the efficacy of pyrantel pamoate and a combined regimen of piperazine citrate and bephenium hydroxynaphthoate in the treatment of intestinal nemathelminthiases.

Pyrantel pamoate at a dose of 10 mg/kg body weight daily for 2 or 3 days was found to be more effective against Ascaris than both a regimen of bephenium hydroxynaphthoate (2.5 g base) and piperazine citrate (2-3 g) given daily for 2 days and a placebo-treated control group. The cure rates for pyrantel were about 95% compared to 90 and 20% for the other two groups respectively. None of the drug schedules was effective against the Trichuris. The bephenium/piperazine regimen was superior to both the 2-day and 3-day courses of pyrantel pamoate against the hookworm with aggregate cure rates of 58-60% for pyrantel pamoate and 68-85% for bephenium/piperazine. The results were better than those reported earlier in the series when a single dose of pyrantel pamoate (10 mg/kg of body weight) was used. Pyrantel pamoate was well tolerated and the drug merits further studies at higher doses, particularly against the hookworm.

Efficacy of seven anthelmintics against Ancylostoma ceylanicum in the golden hamster, Mesocricetus auratus.

In an experimental patent infection of Ancylostoma ceylanicum in golden hamsters the efficacy of seven anthelmintics was tested; bephenium hydroxynaphthoate, tetramisole, tetrachlorethylene, phenylene 1,4-diisothiocyanate, thiabendazole, parbendazole and mebendazole were studied. Mebendazole was the most effective, with parbendazole, phenylene 1,4-diisothiocyanate, thiabendazole and bephenium hydroxynaphthoate also satisfactory. Tetrachlorethylene and tetramisole were the least effective in our screen.

Comparative single/dose treatment of hookworm and roundworm infections with levamisole, pyrantel and bephenium*.

One-hundred and forty-five farmers aged 7-45 years who were infected with Ancylostoma duodenale and/or ascaris were treated with a single dose of levamisole, pyrantel, or bephenium. The percentage cure rates were ascaris 100 per cent ahd hookworm 93 per cent for levamisole; ascaris 90 per cent and hookworm 78 per cent for pyrantel; and ascaris 73 per cent and hookworm 81 per cent for bephenium. The 3 drugs were well tolerated. The opinions and assertions contained herein are the private ones of the authors and are not to be construed as official or as reflecting the views of the Department of the Navy or The Egyptian Ministry of Healty.