Malaria remains a major public health problem in most of the almost 100 countries or territories in which it is still endemic. It has been estimated that the number of new clinical cases is on the order of 100 million annually (WHO, 1987). While in many of the endemic countries the epidemiological situation has remained static, in others it has worsened and there have been a number of countries in which a serious recrudesence has occurred within the last few years, among them Sri Lanka and Brazil. There are many different reasons for this complex situation and some of them will be touched upon below, following a general review of the current epidemiological situation.

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Females of seven sand fly species caught on man in several leishmaniasis-endemic foci in Ecuador were examined to assess the value of the accessory gland secretions as an indicator of parity. It was found that parous females could be distinguished from nullipars by the presence of granular secretions in the accessory glands in Lutzomyia ayacuchensis, probable vector of Leishmania in the Andean highlands of southern Ecuador. Examination of the female accessory glands was not a reliable method for determining parity in six other sand fly species caught in lowland areas, including Lu. trapidoi, Lu. hartmanni, and Lu. gomezi, three proven vectors of Leishmania, since glanular secretions were found in both parous and nulliparous females.

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The mosquito fish (Gambusia affinis) that was transferred to Tokushima City, Tokushima Prefecture in 1969 was studied in relation to the control of mosquitoes. A number of the fish were collected at several ponds and ditches where the fish had increased in number and were repeatedly released into swamps, sewers, fallow rice fields, etc. They were established in 7 places in 1970, 36 in 1971, 76 in 1972 and 104 in 1973. In 27 of those places, both the medaka (Oryzias latipes) and mosquito larvae co-existed, but after the establishment of Gambusia in these places, no mosquito larvae were found. The population density of Oryzias became low and that of Gambusia increased. The water areas with high densities of Gambusia were still or had an inflow of household waste water causing eutrophy. When Gambusia and Oryzias were found together in a water area, the total number of fish was as large as 400-500 per 1 m². The result from laboratory observations demonstrated that Gambusia prey on more mosquito larvae than Oryzias. If Gambusia were raised together with Oryzias in the same water tank, Gambusia attacked and eventually exterminated Oryzias. The feeding habits of Gambusia and Oryzias depend on the availability of food in the environment and are highly variable. It was shown that both species are involved in the competition for space and food in connection with their ecological niche. The above results indicated that Gambusia is more suitable for the control of mosquito larvae than Oryzias. In fact, it was observed that Gambusia became more predominant and more expansive in its habitat in the water areas examined.

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An insect growth regulator, S-31183, 2- [1-methyl-2- (4-phenoxyphenoxy) ethoxy] pyridine, was applied into 2 slow running streams to evaluate its efficacy against malaria vectors from the beginning of February to the end of April 1987. The evaluation of the efficacy was based on bioassay with the waters sampled from the streams and on the parity of the mosquitoes collected from the study site. The application of S-31183 induced almost 100% inhibition of emergence of Anopheles maculatus and An. minimus, 24 hr after application. The emergence was inhibited by averages of 80% in An. minimus and 56.7% in An. maculatus, in the end of the 4th week. Likewise, the nulliparous rates also decreased till the end of the 8th week.

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A helminthological study of stool and urine samples collected from 1, 037 people from four rural communities in Gumau District of Bauchi State, Nigeria was carried out using formo-ether concentration and direct centrifugation methods respective ly. The study is the first parasitological survey to be carried out in the district. Thirty-nine per cent of examined persons were infected. Ova of Ascaris lumbricoides, Schis-tosoma haematobium, Schistosoma mansoni and Trichuris trichiura were most common. Hookworm, tapeworm and Strongyloides stercoralis were also encountered, 17.9% and 10. 8% of examined persons had S. haematobium and S. mansoni infections respectively. Water demand index (number of persons per well) for each community was calculated as a ratio of the total population to the number of safe water sources available in that community. A significant relationship was found between water demand index and S. haematobium (r = 0.95) on one hand, and S. mansoni (r = 0.88) on the other (P < 0.01). Such relationship was not found in soil borne helminth infections. A similarly significant association was found between distance from river and prevalence of S. haematobium (r = 0.94) on one hand and S. mansoni (r = 0.95) on the other (P < 0.01) but not found in soil-borne helminth infections. These findings seem to suggest that water demand index may be an important factor in the epidemiology of Schistosome infections in rural communities. Water demand index may also be a useful field technique for estimating and comparing the rates of water associated helminth infections in rural communities with comparable environmental conditions.

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Simulium (Ectemnaspis) pautense sp. n. was described based on female, male, pupal and larval specimens collected in small streams of Andean region in Ecuador. This new species is close to S. (E.) gabaldoni Ramírez Pérez from Venezuela by having the 6-filamented pupal gills, but differs in the female from the latter species by lacking denticles in the cibarium and by the coloration of the legs.

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The successful treatment of Diphyllobothrium latum, Taenia saginata and Diplogonopolus grandis infections with Gastrografin is herein reported. Eleven subjects (8 cases of D. latum, 2 of T. saginata and one of D. grandis infection) found to have tapeworm infection based on the history of discharge of gravid segments and/or positivity for tapeworm egg were first pretreated with barium enema procedure and were treated with 300 to 500 ml Gastrografin by duodenal manipulation. All cases who indicated the presence of the tapeworm as a radiolucent shadows were completely treated with Gastrografin. All tapeworms with scolex expelled were actively moving in the saline. The time of treatment (from 15 to 30 min) was shorter than that of other medical treatments. No side effects were observed. In the present study, the treatment with Gastrografin was found to be a satisfactory anthelmintic method against D. latum, T. saginata and D. grandis infection.

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Clinical and parasitological survey on onchocerciasis was carried out in the Jarawa Valley area of Nigeria. A total of 1, 821 inhabitants from six villages were examined and 908 (49.9%) were positive for microfilaria of Onchocerca volvulus. Onchocercal infection increased with age, reaching the highest level in adults over 40 years old. Pruritus was the most frequent lesion, followed by skin depigmentaion, visual impairment, nodule, hanging groin and elephantiasis. Leopard skin occurred in various parts of the body including areas not exposed to blackfly-bites. Lymphatic manifestation, hanging groin and elephantiasis, occurred mostly in old male subjects. The adult had the highest prevalence of nodules mainly in the pelvic regions. Skin biopsies taken from the iliac crest gave the highest frequency of positive skin snip.

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