Masashi Ohbayashi

Prolonged expulsion of adult Trichinella spiralis and eosinophil infiltration in mast cell-deficient W/Wv mice

Eosinophil infiltrations were observed in the intestine and the muscle of both Trichinella spiralis-infected (WBxC57BL/6)F1-W/Wv mice and their littermates, WBB6F1-+/+, +/W, +/Wv, almost to the same extent. W/Wv mice did not show infiltration of subepithelial mast cells and globule leucocytes in response to T. spiralis infection. Increased numbers of these cells were observed in their littermates. Worms in W/Wv mice were retained for longer periods than those in littermates. Also, no difference was noted in the production of specific serum antibodies between W/Wv mice and their littermates, as determined by passive cutaneous anaphylaxis (PCA) for specific IgE and by indirect haemagglutination (IHA). These results suggest a possible participation of SMC, GL and eosinophils in the expulsion of adult T. spiralis.

Growth of a Japanese isolate of Taenia crassiceps in intermediate and definitive hosts.

Higher infection rates were observed in gerbils and voles than in ICR mice after oral inoculation with eggs of a Japanese isolate ofTaenia crassiceps. Asexual reproduction ofT. crassiceps cysticerci was observed in all gerbils and voles infected i.p. with the cysticerci. However, ICR mice and Wistar rats were not suitable for the asexual proliferation ofT. crassiceps. The hooks of cysticerci from mice were smaller than those from gerbils. In experimentally infected puppies, parasite development was noted as follows: strobilation and initial differentiation of the genital primordia on day 7 postinoculation (p.i.), appearance of the testes on day 9, observation of the ovaries on day 10, and development of the lateral branches of the uterus on day 15. The prepatent period was 27–31 days. After day 15 p.i., most of the worms were recovered from the middle third of the small intestine. The number of proglottids shed per day by each strobila was about 1. The number of eggs contained in a gravid segment was about 13000.

The Taxonomic Status of Echinococcus cruzi Brumpt and Joyeux, 1924 (Cestoda: Taeniidae) from an Agouti (Rodentia: Dasyproctidae) in Brazil

Paratype material of Echinococcus cruzi Brumpt and Joyeux, 1924, described from an agouti, Dasyprocta leporina (L.), in Brazil, was compared with Echinococcus oligarthrus (Diesing, 1863), of which the larval stage occurs also in agoutis and other rodents in South America and Central America. Comparisons of the larval cestodes (metacestodes) showed that the rostellar hooks from protoscolices of the two taxa corresponded in form, and their slightly greater lengths in E. cruzi were considered to be of no taxonomic significance. They agreed as well in other morphological characteristics. Echinococcus cruzi was compared also with the other neotropical species, E. vogeli Rausch and Bernstein, 1972, Based on these comparisons and in agreement with the earlier conclusion of Cameron (1926), E. cruzi Brumpt and Joyeux, 1924 is placed in synonymy with E. oligarthrus (Diesing, 1863).

Phenotypic changes in hepatic mast cells accumulating around the metacestodes of Taenia taeniaeformis in rats

Staining properties, kinetics and degranulation of the hepatic mast cells (HMC) accumulating around the metacestodes of Taenia taeniaeformis in the liver of rats were studied. Two different types of HMC, designated as Type I and Type II, could be classified according to histochemical properties and response to compound 48/80. Type I cells resembled mucosal mast cells (MMC), whereas Type II did not. HMC, mostly Type I, were observed from day 14 postinfection (PI), while Type II were seen only from day 28 PI. On day 28 PI, Type II represented a transitional staining pattern between MMC and connective tissue mast cells (CTMC). The ratio of Type II to Type I increased gradually with the course of infection and was about 1 to 1 on day 70 PI. At this time, most of the HMC that constituted Type II as well as CTMC could be stained with berberine sulfate. While the phenotypic change of HMC to CTMC was found in the middle and inner capsular layers, most of the HMC in the outer capsular layer maintained the phenotype of MMC. The present results suggest that hepatic mast cells increased as the MMC phenotype, then showed the heterogeneity in which the transitional form of mast cells emerged followed by the appearance of the CTMC type.

On some anoplocephaline cestodes from pikas, Ochotona spp. (Lagomorpha), in Nepal, with the description of Ectopocephalium abei gen. et sp. n.

Three species of anoplocephaline cestodes, Anoplocephalinae gen. et sp. indet., Schizorchis cf. altaica Gvozdev, 1951, and Ectopocephalium abei gen. et sp. n., are reported from pikas, Ochotona roylei (Ogilby) and 0. macrotis (Giinther), from central Nepal. The taxonomic status of Schizorchis esarsi Lovekar et al., 1972, and of Schizorchodes dipodomi Bienek and Grundmann, 1972, is discussed, with the conclusion that both species belong in the subfamily Linstowiinae, near the genus Atriotaenia Sandground, 1926. Ectopocephalium gen. n. is distinguished from other genera in the subfamily Anoplocephalinae by the modified anterior portion of the strobila, which is embedded in the tissue of the sacculus rotundus (lower ileum) of the host, and by the arrangement of the genital organs. The attachment of E. abei and the consequent tissue response are described, and the zoogeography of cestodes in pikas is briefly discussed. During March-July 1968, a biological survey of Nepal was undertaken by an expedition from the University of Hokkaido, with support of the Hokkaido University Himalayan Committee. The objectives included an investigation of the small mammals of the region, under the direction of Dr. Hisashi Abe, of Hokkaido University, who kindly made available to us a large series of preserved carcasses for parasitological examination. Information concerning the taxonomy and ecology of these mammals has been published by Abe (1971). Among the preserved materials was a series of pikas, Ochotona spp., from which we obtained anoplocephaline cestodes representing three species. One of these exhibited a combination of characters that was unlike any within the genera recognized in the subfamily Anoplocephalinae. The results of the study of these cestodes are reported in the present

Hybridization Studies of Angiostrongylus siamensis Ohbayashi, Kamiya and Bhaibulaya, 1979 and A. costaricensis Morera and Cespedes, 1971

Hybridization has been studied in Angiostrongylus spp. parasitic in the pulmonary arteries. Bhaibulaya (1974, Int. J. Parasit. 4: 567-573) crossed A. cantonensis with A. mackerrasae, and Cross and Bhaibulaya (1974, Southeast Asian J. trop. Med. Pub. Hlth 5: 374-378) crossed A. cantonensis with A. malaysiensis, confirming the validity of A. cantonensis, A. mackerrasae and A. malaysiensis. We have reported that A. siamensis are present in the mesenteric arteries of rodents from Thailand (Ohbayashi et al., 1979, Jap. J. Vet. Res. 27: 5-10). The life cycle of A. siamensis is presumed to have a wide host range in murid rodents (Kamiya et al., 1980, Jap. J. Vet. Res. 28: 114-121). Furthermore, a suspected accidental case of A. siamensis in a crab-eating monkey has been reported (Oku et al., 1983, Jap. J. Vet. Res. 31: 71-75). A. siamensis is very similar to A. costaricensis in its development and migration route within mice as a final host (Kudo et al., 1983, Jap. J. Vet. Res. 31: 151-163). An aquatic snail, Biomphalaria glabrata, can serve as an experimental intermediate host of this parasite (Katakura et al., 1981, Jap. J. Parasit. 30: 23-30). A. costaricensis is also parasitic in the mesenteric arteries of rodents in the Americas (Ubelaker and Hall, 1979, J. Parasit. 65: 307), and causes human abdominal angiostrongylosis. A. siamensis and A. costaricensis are suspected to be closely related taxonomically. Their validity as species have been determined by experimental hybridization. The A. siamensis used in this study were originally obtained from Rattus sabanus in Thailand, and has been maintained in our laboratory since 1978 by using B. glabrata as an intermediate host, and the following laboratory animals as definitive hosts: mice, rats, cotton rats (Sigmodon hispidus) and jirds (Meriones unguiculatus). The A. costaricensis used in this study were provided by Professor Pedro Morera, The University of Costa Rica, San Jose, Costa Rica, and have been maintained in snails and laboratory mammals similar to A. siamensis. The C3H/He mice used in these studies were obtained from the CLEA Breeding Laboratory, Kawasaki, Japan. The jirds and snails, B. glabrata, were supplied by the animal laboratory of the Department of Parasitology, Faculty of Veterinary Medicine, Hokkaido University, Japan. Third-stage larvae of A. siamensis and A. costaricensis were obtained from B. glabrata, which had been infected with first-stage larvae for 35 days, after conventional digestion with HCI and pepsin for about 1 hr. One third-stage larva of each species was inoculated via stomach tube into each of 35 mice. Thirty-six days PI, the mice were killed and the heart, aorta and mesenteric and iliac arteries were examined for adult worms, and the intestines were examined for evidence of eggs and first-stage larvae. The first-stage F1 hybrid larvae obtained from the intestines of some of the mice were used to infect B. glabrata. Twenty third-stage larvae recovered from the snails 7 wk PI were presented orally to each of 6 jirds and 13 mice. The infected jirds and mice were killed and examined for adult worms, eggs and first-stage larvae. Adult worms were fixed in 10% formalin and cleared in lactophenol until examined, and the firstand third-stage larvae were killed by heat and measured. The results of inoculation with a single thirdstage larva of each species are given in Table I. Among the 35 inoculated mice, 15 mice were found to be infected with 1 parasite, and 4 mice with 2 parasites of the same sex. Thirteen mice were uninfected. Two mice harbored A. siamensis 6 and A. costaricensis 2 and 1 mouse harbored A. siamensis 2 and A. costaricensis 6. As the mouse was dead when examined live firststage larvae could not be obtained. The F1 hybrids reported here are hybrids between A. siamensis 6 and A. costaricensis Y. Eggs were found in the intestinal wall of the mice which harbored