A total of 579 wild female flies belonging to eight species of Simulium were collected on human baits, in relation to the transmission of a human zoonotic onchocerciasis found in Oita, Japan. Simulium bidentatum was the most dominant species. Natural infections with filarial larvae were found in 11 of 449 S. bidentatum (or 6.5% of the parous flies) and in 1 of 23 S. aokii (or 10% of the parous flies). All the infected flies had 1-4 either first-, second-or early third-stage larvae in the thorax. Examination of third-stage larvae shows that S. bidentatum is infected with at least two species of Onchocerca. Our result represents the first record of natural Onchocerca infections in Japanese Simuliidae, and also suggests the possibility of S. bidentatum as the potential vector of zoonotic Onchocerca spp. to humans.

View full abstract

The changes in the intensity of Schistosoma haematobium infection, incidence and conversion/reversion ratio in a community were observed over a period of 1.5 years. The intensity of infection was judged by two indices : egg counts per 10 ml of urine and egg counts per hour. During the study period, 4 urine examinations were conducted at 6-month intervals. Subjects were included in the analysis of the changes in the intensity of infection in a community if they took all 4 urine examinations and were positive for eggs. The changes in the intensity of S. haematobium infection differed considerably according to the indices used. The changes in the intensity of infection were compared with the changes in the level of transmission expressed by incidence and conversion/reversion ratio or with the changes in the urine volume. The changes in the intensity of infection expressed by egg counts per hour closely paralleled the changes in both incidence and conversion/reversion ratio in a community, regardless of urine volume. By contrast, when the intensity of infection was expressed by egg counts per 10 ml of urine, it did not correlate with the changes in the level of transmission, and was negatively related to the changes in urine volume. These results suggest that egg counts per hour is a reliable index that accurately reflects the changes in the intensity of S. haematobium infection in a community.

View full abstract

Water contact observation and urine examination were carried out on a population in an endemic area of Schistosoma haematobium infection, Mwachinga, Kwale district, Kenya. The change in the mean level of water contact with age and the age-prevalence or age-intensity distribution of S. haematobium infection showed similar trends, but not a direct quantitative relationship. Therefore, a mathematical model was applied in the attempt to analyze the relationship between the intensity of S. haematobium infection and the level of water contact. The worm burden, number of paired worms and proportion of hosts with paired worms were estimated from the level of water contact, annual incidence, and the proposed life-span of S. haematobium by using an immigration-death model on the basis of simple assumptions. These estimated values were compared with the observed prevalence and intensity of infection. The results showed a linear correlation between observed data and estimated values. We conclude that the characteristic shape of the age-egg output curve for S. haematobium in the community is satisfactorily explained solely in terms of the change in water contact with age.

View full abstract

A mass blood examination was carried out in a coastal village of Perupuk, Asahan Regency, North Sumatra, Indonesia in August 1982. The parasite rate in all ages revealed remarkably high (44%). This was caused by an explosive outbreak of Plasmodium falciparum malaria. The parasite rate in young children (0-9 years) was very high around 60% whereas low less than 20% in adult (over 34 years). This indicates a possibility of outbreak of malaria mostly in children posing public health subject in a village of tropical rural area. Gametocyte carriers of P. falciparum were detected only in the age group less than 25 years. The high parasite density of P. falciparum with both asexual form (more than 1, 000 ring forms/mm³) and gametocyte (more than 100 gametocytes/mm³) was detected only in the age group less than 12 years. Falciparum malaria of high intensity repeatedly occurs mostly in younger age group in Anopheles sundaicus breeding coastal area in north Sumatra. A possible control method aiming at gametocyte carrier of young age group is discussed.

View full abstract

In order to analyze the cellular mechanism of immunosuppression during acute infection by Ascaris suum, cytokine and natural killer activities in A. suum infected mice were investigated.
Ten days after infection with 10³ or 10⁴ embryonated A. suum eggs, Concanavalin A induced interleukin 2 (IL-2) production by splenocytes were reduced. At the same time, NK activity of splenocytes and the levels of serum interferon induced by Poly I. Poly C were also reduced. On the other hand, culture supernatants of peritoneal adherent cells from A. suum infected mice showed significantly high interleukin 1 activity which reached peak level on day 15 following lipopolysaccharide stimulation. Increase in the number of macrophages in the peritoneal cavity were also observed in this period. Furthermore, the culture supernatants of peritoneal adherent cells from 10-days A. suum infected mice exhibited a suppressive effect on both IL-2 production by normal splenocytes and IL-2 activity assayed using CTLL-2 cells. Dialysis and molecular filtration studies indicated that the factor with molecular weight below 10, 000 related to the suppressive effect. But there was no significant increase of prostaglandin E₂ in the culture supernatants.
These results suggest that activated macrophages may play an important part in the immunosuppression by producing a soluble suppressive factor during acute infection by A. suum.

View full abstract

This study was undertaken to prepare monoclonal antibodies which recognized the tegumental antigens of newly excysted metacercaria (NEM) and adult flukes of Paragonimus ohirai. From splenic cells of mice immunized with either the Triton X-100 extract of adult fluke surface or NEM sonicate, monoclonal antibodies were produced by ELISA screening followed by trial immunostaining of fluke sections. We prepared a monoclonal antibody (AS-Mab) recognizing the tegumental antigen of the adult fluke and a monoclonal antibody (MS-Mab) for the NEM tegumental antigen. AS-Mab also bound to the tegument of 1-week-old juveniles but not to that of NEM. MS-Mab bound the tegument from the metacercaria to adult stages, but the degree of immunostaining appeared to decrease with maturation of the flukes. By the double immunodiffusion technique, the two monoclonal antibodies formed crossing precipitin lines against a mixture of the adult surface antigen extract and the NEM antigen extract. MS-Mab and AS-Mab gave precipitin line against the incubation fluid from NEM and adult flukes, respectively.

View full abstract

The present study was designed to evaluate the intradermal skin test (ST) and the ELISA as diagnostic tools in the screening for Ecuadorian cutaneous and mucocutaneous leishmaniasis. The antigen for skin testing was prepared from ruptured promastigotes of Leishmania braziliensis. The ST and ELISA positive rates among 72 subjects with active dermal lesions were 81.8% (36/44) and 81.3% (52/64), respectively, while parasites were observed in 31 (44.9%) of 69 subjects presenting active lesions. In the parasites positive cases, all subjects proved to be positive for the two tests except for one in ST and two in ELISA. In 35 healed cases, the ST and ELISA positive rates were 86.2% (25/29) and 72.4% (21/29), respectively. On the other hand, the positive rate in subjects without clinical signs was only 3.8% in ST and 8.2% in ELISA. An epidemiological survey in Selva Alegre, Esmeraldas, revealed that among 115 inhabitants 38 were positive for the clinical signs, 10 active and 28 healed cases. Of these subjects 33 (86.8%) showed positive reactions against ST and/or ELISA. Based on the results obtained, therefore, we concluded that the present skin testing antigen and ELISA were very useful for the screening of leishmaniasis in the endemic areas of Ecuador.

View full abstract

Seroepidemiological studies on ascariasis and toxoplasmosis were conducted in a Brazilian Japanese settlement, Tomé-Açu, in August, 1988. The specific IgE antibodies against Ascaris antigen were assayed and 99 individuals out of 221 inhabitants in the area were found positive (44.8%), while only 4 out of 182 blood donors in Gunma University Hospital, Japan, were positive (2.2%). The poor general sanitary conditions such as water supply or sewerage system in Tomé-Açu may be the cause of the high positive rate of anti-ascaris antibody. The specific IgG antibodies against Toxoplasma were assayed, 164 out of 218 were positive in Tomé-Açu (75.2%), while 65 out of 400 were positive in Gunma University Hospital (16.3%). The results of the questionnaire showed that 77.6% of the inhabitants in Tomé-Açu kept cats in their houses. Very few of them answered the custom of taking under-cooked meat. The role of cats was assumed to be attributable to the high prevalence rate of Toxoplasma infection.

View full abstract

A 25 year-old Japanese man (musician) had been in Middle-Africa for the concert-tour from 14 January to 20 February 1989. On 21 February after homecoming to Japan, a lesion with a severe pain was found in the right abdomen. He expelled a white larval worm (1.5 cm in length) from this lesion by pressure of his fingers. This larval worm taken out from the lesion was identified as the third-stage larva of Cordylobia anthropophaga (Blanchard, 1893), by their pair of toothed, spade-like oral hooklets and by several pairs of posteriorly directed fleshy processes arising from the twelve abdominal segments, as well as by the character of the posterior spiracles, which lack a distinct chitinous rim.
The disease caused by the larva of C. anthropophaga is a familiar form of myiasis in Africa. This fly lays its eggs on dry sand polluted with the excrement of animals, or clothing. The hatched larva invade the skin of human and animals. This patient may be contacted with a larva of this fly in Africa

View full abstract