Isao Tada

Karyotypes of Brugia pahangi and Brugia malayi (Nematoda: Filarioidea)

Using air-dried preparations of the testis and ovary, karyotypes were analyzed and compared to each other in two species of filarial parasites, Brugia pahangi and B. malayi. Both species had a diploid number of 10 chromosomes and were karyotypically very similar. C-banding analyses disclosed that the sex-determining mechanism of these species was of the XY-XX type, where the X chromosome was the largest, and the Y chromosome was of medium-size.

The vectoral role of several blackfly species (Diptera: Simuliidae) in relation to human onchocerciasis in the Sierra Parima and Upper Orinoco regions of Venezuela

Experimental and natural infections with Onchocerca volvulus were studied in several anthropophilic blackfly species present in the endemic area of the Upper Orinoco region of Venezuela. When fed on four different Yanomami volunteers in the Sierra Parima, the total infection rate was 31.4% for Simulium guianense in comparison with 7.5% for S. limbatum. The proportion of ingested microfilariae that entered the thorax during the first 24 hours and completed development to the infective stage was also much lower in the latter than in the former species. There was no larval development of O. volvulus in S. antillarum, but one female harboured in its head six infective larvae of a zoonotic filaria. When S. oyapokense s.l. was fed on an infected volunteer in the Upper Orinoco most flies ingested few microfilariae, and further development reached only the L1 stage. Natural infection and infectivity rates for S. guianense in two localities of the Sierra Parima were 0.2-4.0% and 1.3-10.2%, respectively, more than 50% of the L3 larvae being in the head. The corresponding data for S. oyapockense s.l. in the Upper Orinoco were 0.1-0.5%, although the only L3 larva found did not correspond to O. volvulus. It is suggested that S. guianense is the main vector of onchocerciasis in the Sierra Parima and that S. limbatum could play a secondary role. Simulium oyapockense s.l. replaces them in the Upper Orinoco and may maintain a degree of transmission, but its epidemiological importance remains to be assessed.

The effect of fatty acids on the developmental direction of Strongyloides ratti first-stage larvae

The effect of fatty acids was studied on the developmental direction of Strongyloides ratti first-stage larvae (L1). The proportion of third-stage infective larvae increased markedly when L1 were cultured in faeces with added fatty acids such as palmitic (C16), stearic (C18), oleic (C18:1) and linoleic (C18:2) acids. Unsaturated fatty acids were more effective than saturated ones. Moreover, the proportion of infective larvae increased with quantity of linoleic acid but the triacylglycerols of any fatty acid had no effect. These results suggest that these free fatty acids cause physiological changes that determine the developmental course of L1 of S. ratti in nature.

EFFECTS OF PREINTESTINAL LARVAL ANTIGENIC STIMULI ON THE GENERATION OF INTESTINAL IMMUNITY IN STRONGYLOIDES RATTI INFECTION IN RATS

Generation of intestinal immunity by antigenic stimulation with preintestinal, tissue-migrating larvae was investigated in the Strongyloides ratti-rat model. The results of daily fecal egg counts showed that the intestinal immunity against adult worms could be partially generated by priming with preintestinal migrating larvae. A further study demonstrated that this partial reduction of daily fecal egg count was mainly the result of inhibitory effects on the fecundity of the parasitic females, although the expulsion of the parasite from the gut could be advanced by several days. After tertiary immunization with preintestinal larvae, no significant potentiation in the protection was observed when compared with the rats treated by primary immunization alone.

IgE response inStrongyloides ratti-infected rats with special reference to the life cycle of the parasite

Parasite-specific IgE antibody response was examined inStrongyloides ratti-infected rats. The results showed that the parasite-specific IgE antibody response was generated after a primary infection. However, repeated infections rather depressed the level of parasite-specific IgE antibody in the serum. Immunization limited to specific stages of the parasite revealed that stimulation of parasite-specific IgE antibody was related to the intestinal adult stage. On the other hand, depression of IgE titers was related to the tissue-migrating larval stage. The capacity of the each stage of the parasite to induce specific IgE response may be related to the variable results of the IgE responses in human strongyloidiasis.

Effects of anti-IgE monoclonal antibody on a primary infection of Strongyloides ratti in mice.

Many helminth infections induce profound changes in the immune response of the host. Enhancement of IgE production is one of the characteristic features observed during and after the course of infections. In Strongyloides ratti infection, IgE antibodies have been detected in mice (Dawkins et al. 1982) and in rats (Korenaga et al. 1986). Furthermore, we have shown that multiple infections with infective larvae of S. ratti depress parasitespecific IgE antibody production in rats (Korenaga et al. 1986). Intestinal mast cells have been suggested to be one of the effectors involved in the process of adult worm rejection from the small intestine of mice (Nawa et al. 1985). An involvement of IgE antibodies, however, has not been confirmed in protective immunity in murine strongyloidiasis. In the present study we examined a possible protective role of IgE in mice infected with S. ratti. To clarify this, we used IgE-depleted BALB/c mice, which were injected intraperitoneally with 5 30 gg purified rat antimouse IgE monoclonal antibody (6HD5, IgG2a) twice a week, beginning on the day of their birth. Ageand sex-matched normal mice served as controls. In all experiments, 5-7 mice in each group were infected with 1,000 L3 of S. ratti maintained in our laboratory. Methods for the cultured and inoculation of larvae have previously been described (Tada et al. 1979). For monitoring of fecal larval output, fresh feces were collected individually, weighed, and suspended in 10times their weight of water. Fecal samples (50 gl) were examined under a microscope. Soluble antigen was prepared from the infective larvae according to the methods of Dawkins et al. (1982). Parasite-specific IgE antibody was determined by passive cutaneous anaphylaxis (PCA; Watanabe and Ovary 1977). As a challenge, 2.8 mg L3 antigen was given intravenously with 1 ml 1% Evans blue solution at 24 h after the intradermal injection of serum samples. Blue spots measuring >_ 5 mm in diameter indicated a positive reaction. An enzyme-linked immunosorbent assay (ELISA;

Chromosomes of Onchocerca volvulus (Spirurida:Onchocercidae): A comparative study between Nigeria and Guatemala

Chromosomes of Nigerian Onchocerca volvulus were compared with those of Guatemalan O. volvulus. Both parasites had basically the same chromosomal construct (2n = 8, XY type). Autosomes consisted of a pair of large and two smaller pairs. Sex chromosomes were made up of medium sized X chromosome and very small Y chromosome. It was not possible to infer the position of the centromeres.

THE FIRST CASE OF A HUMAN INFECTED WITH AN ACANTHOCEPHALAN PARASITE, BOLBOSOMA SP.

A rare instance of human infection with an acanthocephalan is reported. A species of Bolbosoma, class Palaeacanthocephala, was found at laparotomy in a 51-yr-old Japanese fisherman who complained of acute abdominal pain. The parasite probably was acquired by eating raw fish (sashimi), perhaps bluefin tuna. Infections of humans with Acanthocephala are rare. Most of the reported infections have been with Moniliformis and Macracanthorhynchus (class Archiacanthocephala). Only a few reports of infection of humans by other classes are avail- able (Golvan, 1969; Schmidt, 1971). This paper reports the finding of an acanthocephalan para- site, Bolbosoma sp., in a Japanese man admitted to a hospital for acute abdominal pain. CASE REPORT

Basic Studies on Filaria and Filariasis

Although Japanese parasitologists and physicians have published many papers on the epidemiology, clinical signs and symptoms, treatment, and control of filariasis, they also conducted basic research on filaria or filariasis using materials obtained from patients and animal models. This basic research includes morphology, immunology, physiology and pharmacology. Recently, most papers are written in English and published in peer-reviewed international journals. However, decades ago, scientific papers were usually written in Japanese and published in local journals. Therefore, there are many valuable papers that have been hidden from foreign eyes. In this review article, the authors shed light on these hidden papers published years ago. The research subjects reviewed in this article are: (i) periodicity of microfilariae, (ii) immunology, (iii) mode of action of diethylcarbamazine, (iv) parasite-intermediate host relationship, and (v) others.

Effects of various treatments on the chemokinetic behavior of third-stage larvae of Strongyloides ratti on a sodium chloride gradient.

Abstract In observations of the movements of the infective third-stage larvae of a rodent parasitic nematode, Strongyloides ratti, on a sodium chloride gradient set up on agarose plates, two types of chemokinetic behavior were seen: a unidirectional avoidance movement on initial placement of the larvae in unfavorable environmental conditions and a random dispersal movement on their placement within an area of favorable conditions. Track patterns were straight in the avoidance movement but included multiple changes of direction and loops in the dispersal movement. In the present study we examined the interventional activity of treatment with various enzymes, lectins, and chemicals by analyzing the unidirectional avoidance movements of the larvae. We observed that β-glucosidase, hyaluronidase, β-galactosidase, trypsin, protease, lipase, phospholipase C, soybean agglutinin, wheat germ agglutinin, and spermidine exerted inhibitory actions on those movements, which may be guided by the chemosensory function of this nematode.