Subcellular antigen localization in Toxoplasma gondii was studied by immunoelectron microscopy using sera obtained from congenital toxoplasmosis neonates or the mother. IgG and IgM antibodies bound specifically to the dense granules and rhoptries, but little bound to the cytoplasm of the organism or its tegmentum. The results indicate the importance of dense granules and rhoptries as a storage site for the antigens, which would be released and stimulate antibody production in human toxoplasmosis.

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Effects of deoxyspergualine (DSG), an immunosuppressive agent and polyamine synthesis inhibitor, on the rodent malarial protozoa Plasmodium berghei development was studied in vivo. DSG at doses of 5mg/kg body weight (b.w.) was injected intraperitonealy into mice (Balb/c) that had been infected with P. berghei (ANKA strain). DSG injection showed to be effective in reducing the percentage of parasitemia and spleen weight and in prolonging the survival days of infected mice. These findings in this study suggest the possibility that DSG could be developed as a candidate for anti-malarial drugs.

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We have developed a mathematical model to estimate the degree of transmission of Plasmodium falciparum malaria, that is adjusted to an endemic region in Vanuatu, eastern Melanesia, incorporating the factor concerning the loss of immunity in human hosts. Applying this model, we have carried out simulations for more than fifty situations. Our model is based on Dietz et al. (DMT) model which contains epidemiological factors related to malaria transmission. By using field data from an epidemiological study in Vanuatu, we have determined epidemiological parameters and improved the model. Also our model can treat situations with variable vectorial capacity value. The simulations carried out show that it is important to decrease vectorial capacity by taking anti-malarial measures in order to reduce the prevalence of malaria. One or two operations of mass drug administration will reduce Plasmodium falciparum prevalence drastically, but intense reinfection will raise infection rate again within a few years. However, the resurgence of malaria will not occur for a long time if mass drug administration accompanied with possible reduction of vectorial capacity by vector control such as insecticide impregnated bed nets and others.

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The positive rate of house-dogs for Dirofilaria immitis microfilariae decreased in 27 years from 1968 to 1994 in northern and southern parts of Nagasaki City. It was examined whether or not the increase of indoor-kept dogs contributed greatly to the reduction in positive rate of house-dogs in the city. Positive rate of dogs was generally lower in indoor-kept dogs than in outdoor-kept dogs. From the lower positive rate of indoor-kept dogs, D. immitis infection is considered to have occurred mainly in outdoor-kept dogs. Positive rate was high from 1968 to 1983 when rate of indoor-kept dogs was low and thereafter positive rate gradually decreased though the rate of indoor-kept dogs was not greatly changed. From this, increase of indoor-kept dogs may be a factor causing the decrease of positive rate in all examined dogs from 1968 to 1983, but the reduction of positive rate thereafter is considered to be due to decrease of positive rate in outdoor-kept dogs.

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Mefloquine is a quinoline compound closely related to quinine and is characterized by its long half-life and excellent clinical efficacy against chloroquine-resistant falciparum malaria. Even recently, the cure rate for falciparum malaria after its use is over 90% in many parts of the world such as most of African countries. However, it is reported to be less effective in Thai-Cambodian or Thai-Burmese border. The higher dose of mefloquine, e.g. 25mg/kg, is required in these areas, but even so unsatisfactory results often ensue. In these areas, mefloquine is used combined with other antimalarials such as qinghaosu derivatives or tetracyclines showing better results. Reported adverse reactions after the therapeutic use of mefloquine include dizziness, nausea, vomiting, diarrhea, headache and so on. With regards to dizziness, however, various figures of its occurrence are reported, probably due to its subjective nature. In addition to the above symptoms, we have to be extemely cautious about the severe neuropsychiatric reactions caused by mefloquine that are reported to occur in one out of 215 cases.
We analyzed the data on 27-28 patients with falciparum malaria who were treated in our hospital with 750-1, 500mg of mefloquine. All but one case were successfully treated without later recrudescence. About one third of the cases experienced undesirable symptoms attributable to the medication, however, most of them were slight and did not require medical intervention. It is likely that mefloquine could be a first-choice drug for uncomplicated falciparum malaria in Japanese as well as in other people.

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