A computer-based book on medical helminthology.

A computer assisted book on medical helminthology has been prepared using ZOOM, a teaching computer program, which uses hypermedia technology to link pictures and text. Information on various helminths, including their morphology, life cycle, clinical manifestations, diagnosis, treatment and epidemiology can be easily accessed using three types of link in a non-linear approach. The book consists of five chapters, each contains the latest information on various aspects of helminth parasites. New information can easily be added to each chapter by the user. References can be assessed and updated for each parasite. The book is designed for students of medical schools, health administrators and physicians in developing countries.

The use of primary health care system in the control of schistosomiasis in the Riyadh Region of Saudi Arabia.

The use of well developed and adequately distributed Primary Health Care (PHC) centers for the control of schistosomiasis in the infested areas in the Central Province of Saudi Arabia around the capital city of Riyadh has proven feasible producing satisfactory results. The number of inhabitants examined for schistosomiasis increased from 10688 in 1984 to 106579 in 1988, and the prevalence dropped from 9.3% in 1984 to 0.6% in 1988. Currently the majority of inhabitants of infested villages are examined in the PHC centers once a year and cases are treated. Snail control is also done by centres.

The potential role of various species of intermediate hosts of Schistosoma haematobium in Saudi Arabia.

The potential role of 3 species of Bulinus in the transmission of Schistosoma haematobium in Saudi Arabia was assessed on the basis of their susceptibility to experimental infection, their geographical distribution and numbers, and the type of habitats in which they were found. B. truncatus, distributed mainly in the mid- and south-western regions, showed extremely low susceptibility to strains of S. haematobium from Yemen, Egypt and Sudan. The same species from one area in the north-west was refractory to a strain of the parasite from Yemen. In contrast, B. wrighti was very susceptible to infection but is found only in a few habitats far from human settlements, thus probably playing little part in the transmission of the disease. As B. beccarii is highly susceptible to the infection and is distributed widely, this snail is probably the main intermediate host of schistosomiasis in Saudi Arabia.

Progress achieved in the control of schistosomiasis in Saudi Arabia.

A significant reduction in the prevalence of both intestinal and urinary schistosomiasis has occurred in all emirates (districts) in all 12 foci of the infection distributed in five regions of Saudi Arabia. Infection with Schistosoma mansoni has dropped in foci of the infection in the Central Region (Riyadh and Hail) and in all foci within the western provinces. Reduction has also occurred in the prevalence of S. haematobium in foci of Gizan, the Red Sea coastal areas and parts of Madinah. The disease no longer exists around Riyadh. The overall prevalence in all 12 foci of infection in Saudi Arabia dropped gradually from 11% in 1983 to 1.9% in 1987. At present the infection rates among expatriates are much higher than among Saudis in most foci. The number of emirates which had rates of 10% or more has dropped from 46 in 1983, to nil in 1987, and the number with rates of 5-10% from 25 in 1983 to one in 1987. The overall prevalence is presently between 1 and less than 5% in 73 emirates and less than 1% in 41 emirates. Significant reduction was observed in most villages in each district. Higher infection rates may still be present in a few areas within one or two emirates not surveyed in the last 2-3 years. The potential danger of a resurgence of the disease due to the development of water resources and the presence of a great number of infected expatriates is significant.

Selective primary health care: strategies for control of disease in the developing world. XII. Ascariasis and trichuriasis.

Ascariasis and trichuriasis are the most prevalent and widespread intestinal helminthiases. Transmission of disease occurs by ingestion or inhalation of Ascaris and Trichuris eggs embryonated in the soil. During the migration of Ascaris to the lungs, pneumonic symptoms may develop. The intestinal stage of the parasite can cause severe symptoms and complications when the worm burden is high. High numbers of Trichuris may cause diarrhea. The poor standard of hygiene, the biology of the parasite (which is such that a high number of very resistant eggs are produced), and the habits of the host (such as the use of night soil) are factors causing a high prevalence of infection in many countries in Asia, Africa, South America, and Europe. The mechanism of the transmission of Ascaris varies in different communities. The peak of infection is among children aged four to 14 years. Worm burden is normally low, and only a small segment of the population harbors a high proportion of the worms present in a community. Control of infections due to Ascaris and Trichuris is feasible by a combination of mass chemotherapy with the effective drugs now available, safe disposal of excreta, destruction of the eggs, and health education.

Studies on schistosomiasis in Taiz Province, Yemen Arab Republic.

Infection with both urinary and intestinal schistosomiasis is prevalent with patchy distribution in Taiz Province, southwest Yemen Arab Republic. Schistosoma haematobium with a prevalence as high as 90% was found in the western, southern, and northern parts of the province. Among school children the overall prevalence was 37%. Infection rates did not differ significantly among various age and sex groups. Three species of Bulinus--B. beccarii, B. truncatus, and B. wrighti--have been found in the province, B. beccarii having the widest distribution and highest density. S. mansoni was found in most parts of the province. A 100% prevalence was found in some schools. The overall prevalence was 64% among school children and 68% among inhabitants of villages surveyed. Highest prevalence was found in the age group 10-20 years. Hepatosplenomegaly was prevalent among children in highly endemic areas. Biomphalaria pfeifferi, the intermediate host of S. mansoni, was found in most valleys.

Progress in the national schistosomiasis control programme of Iran.

A combination of chemotherapy and mollusciciding has been used in Khuzestan, south-west Iran, since 1966, to try to control urinary schistosomiasis. The total amount of molluscicide used each year varied between 702 and 3505 kg and between 287 and 1320 infected persons were detected and treated annually. The prevalence of infection has gradually declined from 8.3% in 1970 to 0.7% in 1979. Similarly, the incidence of infection among schoolchildren decreased from 3.5% in 1970 to 0.7% in 1979. The proportion of Bulinus-infested habitats also decreased from 10% in 1971 to 2.4% in 1979.

Intestinal parasites among Indochinese refugees and Mexican immigrants resettled in Contra Costa County, California.

Stool examinations of 186 Indochinese refugees and 90 immigrants from Mexico resettled in Contra Costa, County, California, have shown that 60 percent of refugees and 39 percent of immigrants are infected with one or more species of pathogenic protozoa and helminths. The mean prevalences of infections among refugees and immigrants, respectively, were: hookworms, 25 and 2 percent; whipworm, 22 and 12 percent; Ascaris, 20 and 12 percent; Giardia lamblia, 11 and 11 percent; Strongyloides, 9 and 1 percent; and Entamoeba histolytica, 2 and 4 percent. clonorchis sinensis was found in 13 percent of refugees and dwarf tapeworm in 9 percent of immigrants. Rates of infection varied with age and sex. Treatment of these parasitic infections is important and justified because: the prevalence is high; some species are highly pathogenic and directly transmittable; most species have long life spans; and safe broad-spectrum drugs are now available.

Prevalence of intestinal helminths in Khuzestan, Southwest Iran, 1977.

Large scale studies were performed to determine the prevalence of various intestinal helminth infections in urban and rural areas of Khuzestan Province, southwest Iran. A total of 16,361 stool samples from people in 105 villages and 14 small towns were examined by the formalin-ether concentration method. Ascaris, hookworms, Trichostrongylus, Trichuris, and Hymenolepis nana showed the highest prevalence. Hookworms and Trichostrongylus were twice as prevalent in rural than in urban areas; in contrast, H. nana was more prevalent in urban areas while the level of Ascaris infections was not significantly different. The intensity of Ascaris and hookworm infections, as estimated by the number of eggs/g of feces, was higher in rural than in urban areas.

An evaluation of levamisole for treatment of ascariasis.

Levamisole (Decaris, Belgium) was tested in Iran, Brazil, and in Mississippi and Louisiana for its efficacy as a single-dose oral treatment for Ascaris infections. Subjects were children ages 2 to 15 years, and numbers treated with levamisole and comparative anthelmintics are as follows: 453 with levamisole; 461 with piperazine citrate; 17 with pyrantel pamoate; and 19 with a placebo. Cure rates and total reduction in mean egg counts observed were 92% and 98% respectively for levamisole and 66% and 90% for piperazine. Sixteen of 17 treated with pyrantel pamoate were cured. In none of the drugs were there notable side reactions, but in all four studies side effects were more frequent with piperazine than with levamisole. Levamisole was found to be a well-tolerated, highly effective single-dose ascaricide. It should prove to be particularly useful for mass chemotherapy in Ascaris control programs.

Epidemiology and mass-treatment of ascariasis in six rural communities in central Iran.

In six villages near Isfahan in central Iran 1,455 persons were examined for intestinal parasites. Those with Ascaris infection were treated with pyrantel pamoate in a single dose of 10 mg/kg body weight and all stools passed during 48 hours after treatment were collected in plastic pans and screened for worms which were then sexed and measured. Ascaris infection rates, 87--95% in the six villages before treatment, were reduced to 1--8% (average 5%) and the mean number of eggs in the feces was reduced from 19/mg to less than 1/mg. All age groups and both sexes were about equally infected, and the average number of worms expelled by treatment ranged from 16 per infected person below 5 years of age to 31 per person 20--39 years of age. Mature and immature worms together were expelled from persons treated at all seasons, indicating that worms were acquired and lost continuously throughout the year. Fecal examination at 2, 4, 6, and 12 months after treatment showed that the prevalence at 12 months had returned to the original level (87% vs. 91%) but the average intensity as reflected in egg-counts had not (10 vs. 19/mg feces). The findings confirm the necessity of repeated treatment at 2- to 3-month intervals.

Evaluation of the effect of different methods of control of soil-transmitted helminths in Khuzestan, southwest Iran.

Three methods of control of soil-transmitted helminths, namely, sanitation, mass-treatment, and sanitation plus mass-treatment, were tried in 15 villages in Khuzestan, southwest Iran. Stool samples from the inhabitants of each village were examined both quantitatively and qualitatively just before starting each control method and again about 4 years later, except for the inhabitants of one village whose stools were re-examined 7 months after moving to a new settlement. Sanitation measures consisted of one latrine for each family and the provision of a sanitary water supply in each village. The drugs piperazine and bephenium hydroxynapthoate were administered alternately every 3 months. The reduction in rates of infection with Ascaris, hookworm, and Trichostrongylus spp., respectively, for the above mentioned methods were as follows: sanitation alone, 28%, 4% and 30%; mass-treatment alone, 84%, 73%, and 31%; sanitation plus mass-treatment, 79%, 69%, and 30% and in the newly constructed village, 76%, 21%, and 38%. In a control group corresponding reductions were 19%, 11%, and 31%. The percentage of egg reduction in persons still infected with these three parasites was, respectively, as follows: mass-treatment plus sanitation, 88%, 88%, and 53%; mass-treatment alone, 90%, 87%, and 37%; sanitation alone, 60%, 26%, and 0.6%; in the newly constructed village, 87%, 78%, and 39%; and in the control group, 29% increased 12%, and 24.5%. The significance of these findings is discussed.

Comparative studies on the evaluation of the effect of new anthelminthics on various intestinal helminthiasis in Iran. Effects of anthelminthics on intestinal helminthiasis.

The effect of pyrantel pamoate, levamisole, mebendazole, thiabendazole and bephenium hydroxynaphthoate on various intestinal helminths were evaluated among the inhabitants of four villages in the Dezful area southwest of Iran. A total number of 328 persons, all infected simultaneously with Ascaris and hookworm (Ancylostoma duodenale) and 49.2% with Trichostrongylus spp., were randomly divided into six groups. One group was kept as the control and the other five were each treated with one compound. Follow-up examinations showed that all of the drugs used were highly effective on Ascaris, and the differences in the cure rate were not statistically significant except for bephenium hydroxynaphthoate which showed a lower cure rate. For hookworm, cure rates of 100, 90, and 85% were observed with levamisole, pyrantel pamoate and bephenium hydroxynaphthoate, respectively. Cure rates observed with mebendazole and thiabendazole were 35 and 51%, respectively. For Trichostrongylus, the highest cure rate was achieved with levamisole, followed by thiabendazole and mebendazole. While the percentage of people showing side-effects was rather low for all drugs, thiabendazole and bephenium hydroxynaphthoate produced a higher, and levamisole a lower, percentage of side effects.

Studies on schistosomiasis in Saudi Arabia.

During studies on schistosomiasis in Saudi Arabia, urine and stool samples from inhabitants of various areas (mostly rural) were examined, and 97 aquatic habitats in 46 localities were searched for snails. The results indicate the occurrence of both urinary and intestinal schistosomiasis in most parts of the country, with a patchy distribution and varying infection rates. The snail intermediate host of Schistosoma mansoni was found to be Biomphalaria arabica. For S. haematobium three species of snails, namely, Bulinus truncatus and B. beccarii in the west and B. reticulatus wrighti in the northeast, may transmit the infection; the susceptibility of the two former species has been confirmed in the laboratory. The limitation in the size of snail habitats--which consist of wells, small canals, cisterns, small swamps, interrupted streams, and ponds--creates a special type of transmission which can be defined as "oasis transmission," making control of the disease both simple and practical.

Present status of trichostrongyliasis in Iran.

Infection with species of Trichostrongylus is common among man and animals in most parts of Iran, and human infections with T. orientalis, T. colubriformis, T. vitrinus, T. axei, T. capricola, T. probolurus, T. skrjabini, and a possibly new, unnamed species have been reported. All are found in Isfahan, central Iran, where the overall prevalence is 67% and the predominant species are T. orientalis and T. colubriformis. Among 737 nomads migrating from the central parts to the south, 86% were found to be infected with one or more of five species (in order of frequency): T. colubriformis, T. orientalis, T. axei, T. capricola, and T. vitrinus. In Khuzestan, southwest Iran, human infections with T. orientalis, T. colubriformis, T. axei, and T. vitrinus with an overall prevalence of 71% have been reported. In the northern parts, along the Caspian Sea, the rate is 7% and the species found, in order of frequency, are T. colubriformis, T. axei, T. vitrinus, and T. orientalis. Trichostrongylus infections are also found in the northwest but are rarely seen in the northeast. In most areas females are more frequently and more heavily infected than are males. All species found in man, except the new, unnamed species, are also found in sheep, goats, cattle, and camels; the number of species found and the order of their frequency differ in various animals and in different areas. Infection in other mammals, such as hares (T. retortaeformis and T. orientalis) and porcupines (T. orientalis), has also been reported.

Studies on schistosomiasis in Somalia.

A survey was made on the prevalence and intensity of schistosomiasis in 14 localities in 4 areas in Somalia has revealed the presence of urinary bilharziasis among the inhabitants of all these localities, this being much higher in the two areas where water development has been accomplished. The mean prevalence of infection was found to be 27.2% and 58.1% in the two areas where water development has only been planned, while it was 58.7% and 75.6% in the two areas where the extension of irrigation was achieved years ago. Snails were collected from the habitats visited and these were identified. The role of Bulinus abyssinicus in the transmission of infection was proven.

Human infection with Trichostrongylus capricola in Iran.

In addition to the six species of Trichostrongylus already reported from man, T.capricola has been found among the population of a nomadic tribe and the inhabitants of three villages in Isfahan Province in the central part of Iran. The prevalance of infection with this species among 40 nomads treated was 22.5% with an average of 5 worms per infection. Among 30 villagers who were treated, 4 (13.3%) passed this species with an average of 2.5 worms per infection. T.capricola was also found in all of 10 sheep and 10 goats examined in each of the two areas.