A vaccination trial in golden hamsters with UV-irradiated infective larvae of Ancylostoma ceylanicum was attempted. One oral vaccination of hamsters with 100 infective larvae irradiated by means of UV-tube (390 nm) at different time intervals induced the development of resistance. As the time exposure of irradiation was increased, there was a corresponding decrease in the subsequent worm establishment. A high level of protection afforded by larvae irradiated for 15min UV-exposure was recorded giving 99·0% and 95·0% worm reduction against the challenge doses of 100 and 1000 normal larvae respectively. There was no marked difference in worm establishment in hamsters vaccinated either orally or subcutaneously, followed by oral challenge. In the vaccinated hamsters, the manifestations of resistance at 15 min UV-exposure were shown by marked reduction in worm establishment and highly reduced epg in pellets with significantly higher blood haemoglobin levels compared with those given normal larvae as vaccine and challenge controls.

Magnacercous cercariae with heavily pigmented tails and possessing a pair of eyespots and seven pairs of penetration glands, some of which are para vesicular, were found to develop in the prosobranch gastropod, Cerithium coralium collected from a brackish water locality at Bheemunipatnam, A. P. India. The cercariae developed into metacercariae of Galactosomum ussuriense in the viscera of the fish Therapon jarbua. Successive stages in the development of metacercaria from the cercaria were followed. Natural infections with metacercariae were found in T. jarbua, Valamugil cunnesius and Megalops cyprinoides. The definitive host of G. ussuriense in the present area of investigation is still not known. This represents the second account of part of a life-cycle in the genus Galactosomum.

Flubendazole given orally at 50mg kg to mice inoculated with 50, 250 or 500 larvae of Angiostrongylus cantonensis showed almost complete larvicidal effect, irrespective of the worm burden.

The migration and distribution of Ancylostoma caninum larvae in the tissues of chickens, infected orally with 1,000 larvae, were studied. Larval yield at necropsy from different organs after digestion with artificial gastric juice revealed a 62·9% recovery four hours after inoculation, followed by a sharp decline to 5·4% at 72 hours. Larvae were found in the heart within four hours, the lungs within eight hours and the liver within 12 to 18 hours but no larvae were recovered from the spleen, kidney or brain. Migration in the muscles of head, neck, thorax and abdomen was detected at 12 hours and was maximal at 36 hours. The establishment of patent infection in the definitive host was studied by feeding infected chicks to hookworm-free pups (one chick/pup) 48 hours, 7 days and 14 days after infection. The mean worm burden at necropsy was highest (15) in the pups fed with chicks 48 hours after infection and was three and nil in the other groups respectively.

The efficacy of eight anthelmintics against Ancylostoma caninum larvae in the skeletal muscles of mice was evaluated. Levamisole (5 × 40 mg kg), thiabendazole (5 × 400mg kg), oxfendazole (5 × 100mg kg), albendazole (5× 1OOmg kg), flubendazole (5 × 200 mg kg), benacil (5 × 200 mg kg) and phenacizole (5 × 200mg kg) showed marked larvicidal activity (98 to 99%). Sch 18099 did not show larvicidal activity even at 5×400 mg kg.

Mice, CBA/HT6T6 and C57BL/10, were vaccinated with 1 × 350 or 1 × 500 Schistosoma mansoni cercariae or schistosomula attenuated with 20 or 56 krad 60Co irradiation and challenged with 200 cercariae. Protective resistance against homologous strain challenge was compared using the Winches Farm Field Station (WFFS) and Naval Medical Research Institute (NMRI) strains of S. mansoni. Maximal resistance to challenge was obtained in both strains of mice with cercariae or schistosomula of either WFFS or NMRI strain attenuated with 20 krad. Protection using organisms attenuated with 56 krad was significantly lower. Since previous studies with the two parasite strains have shown that the biological effects of irradiation are similar, the difference in the immunogenicity of the 56 krad-irradiated NMRI strain in this study from earlier studies must be due either to different local conditions for irradiation or to adaptation of the NMRI strain to a new laboratory environment. This finding may have important implications for vaccination studies and investigations of the mechanisms of immunity where radiation-attenuated parasites are used.

Pylorus and bile-duct restrictions did not prevent the anteriad migration of Hymenolepis diminuta in rat small intestine after food feeding. However, migration was inhibited when the common bile-duct was occluded. The results indicate that pancreatic secretion is the migratory cue for Hymenolepis diminuta in rats.

Results are reported of enzyme analyses, following isoelectric focusing (IEF) in polyacrylamide gels, of Plerocercoids of the pseudophyllidean cestodes Ligula intestinalis and Schistocephalus solidus. No polymorphic variants were detectable for the enzymes lactate dehydrogenase (LDH), malate dehydrogenase(MDH), glucose phosphate isomerase (GPI) or phosphoglucomutase (PGM) in 34 individuals of S. solidus. Similarly, no variants were observed in LDH, MDH or GPI of 159 individuals of L. intestinalis collected from four cyprinid fish species from several locations in southern England. In contrast, PGM of L. intestinalis is Polymorphic. The enzyme appears to be controlled by three loci and one of these loci, designated PGM-2, is Polymorphic with three recognizable phenotypes. The polymorphism is not related to the species orgeographical origin of infected fish and it does not reflect strain variation in L. intestinalis. Instead, it is typical of a genetic polymorphism under the control of two co-dominant alleles. Such a balanced polymorphism requires that cross-fertilization must occur, at least transiently, in L. intestinalis. The work indicates that enzymes can be used as markers in future genetic studies with cestodes, and that the combination of IEF and zymogram analysis represents an important method for the detection of cross-fertilization in these worms.

The spontaneous expulsion of low-level Echinostoma revolutum infections was markedly impaired in mice harbouring 4-week-old Schistosoma mansoni infections at the time of infection with the echinostome.

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The model of Onchocerca lienalis microfilariae (mff) injected into CBA and T.O. strains of mice has been used to examine immunity to skin-dwelling microfilariae following exposure to a range of species oF nelmmms Mice which had received a primary infection with O. cervicalis mff were significantly resistant to challenge with O. lienalis mfT(58% reduction relative to challenge controls). Immunization with the uterine contents (eggs and mff) of O. lienalis, O. gutturosa or O. volvulus conferred equivalent levels of protection agains challenge with O. lienalis mff (66 to 75%). Similar results were obtained with immunizations in mice that employed either fresh or freeze-killed eggs of O. gutturosa. Significant reductions in the recoveries of O. lienalis mff were also demonstrated following the intraperitoneal implantation of adult male worms of O. gutturosa (30 to 52%), the adults of either sex of Dipetalonema viteae (60%), or after infection witn Trichinella spiralis (27 to 81%). Infections with the trematode, Schistosoma mansoni, had a negligible effect on mff recoveries. It is concluded that partial resistance in mice to Onchocerca mff may be stimulated by factors, yet to be determined, that are neither stage nor species-specific.

The proteins of homogenized adult Opisthorchis viverrini were separated by polyacrylamide gel electro-Phoresis and isoelectric focusing in the presence of detergents. By far the most abundant component(s) had a Mr of 18,000 to 19,000, represented about 47% of the total parasite protein, and did not separate in isotypes.

Five adult ewes and five lambs were repeatedly immunized with weekly doses of 10,000 irradiated Haemonchus contortus L3 before challenge with 100,000 and 10,000 normal larvae respectively. Two groups of non-immunized ewes and lambs were similarly challenged and one animal from each of the four groups killed on days 3,5,7,10 and 24 post-challenge. The cellular changes in the abomasal mucosa were less marked in the non-immunized groups than in the immunized animals and appeared later in the lambs than in the ewes. Thus, in the immunized ewes increases in the numbers of mast cells and eosinophils were evident within five days of challenge whereas similar changes appeared later in the immunized lambs. Also marked lymphoid aggregates at the base of the mucosa and in the submucosa were detected only in the immunized ewes. However, both immunized and non-immunized ewes showed rises in the numbers of IgA plasma cells after challenge which were not evident in either group of Iambs.

Adult worms of a filarial parasite have been found during a survey of cattle at Wau Municipal Abbatoir, Bahr El Ghazal Province, Sudan. Two intact male worms were recovered but no females have been encountered as yet. Both worms were found within intradermal tissues at the umbilicus, and came from separate animals of the longhorned variety of indigenous Zebu cattle, Bos indicus. They were unencapsulated in the tissues from which they were isolated by dissection, fixed in 10% (v/v) formal saline and examined by phase microscopy. Dimensions were calculated from camera lucida drawings and are given as mean values for the two specimens.