A gelatin-agar bolus, designed and developed for the administration of metacercariae of the liver fluke Fasciola hepatica, was evaluated in adult Holstein Friesian cattle. The metacercariae, enclosed within a gelatin capsule, were placed inside the bolus and delivered to each animal using an oesophageal balling gun. At slaughter, 13 weeks after challenge, an average of 25% of the challenge dose was recovered from each liver. This percentage recovery is similar to that obtained with other known methods. The new bolus, however, offers improved handling qualities. In addition, the bolus also has potential for improving a number of other techniques including those for the administration of other parasites, compounds or chemotherapeutic agents.

Karyometrical analysis of conventional Giemsa-stained mitotic chromosomes of parthenitae of Sphaerostomum bramae (Trematoda: Opecoelidae) was carried out. The karyotype displays a typical ‘plagiorchiid’ pattern with 22 chromosomes in a diploid set including a first pair of large metacentric elements. Chromosomes with medially or submedially located centromeres prevail in the karyotype; only chromosomes 7 and 9 are subtelocentric. With the data now available, close karyological affinity was noted between S. bramae, the representative of the family Opecoelidae, and other karyologically studied species of some families in the order Plagiorchiiformes: Troglotrematidae, Plagiorchiidae, Prosthogonimidae, Lecithodendriidae and Telorchiidae.

Haemoglobins from three different species of trematodes (Gastrothylax crumenifer, Paramphistomum epiclitum and Isoparorchis hypselobagri) and their respective hosts were digested with papain. Peptides so produced were separated on 10–15% SDS-PAGGE. The probability of coincidence of the peptides was analysed statistically. Oxygen affinity curves of trematode haemoglobins were found to be a rectangular hyperbolic. The Hill coefficient values of all the trematode haemoglobins were found to be 1. The P50 values, at 25°C in 0.2M phosphate buffer pH 7.4, ranged from 0.8 to 1.6 mmHg.

Light microscopy was used to study excystation of Echinostoma caproni metacercariae in various media. Optimal excystation was observed in an alkaline trypsin-bile salts medium (TB) at 40 ± 1°C. The percentage of excystation in TB medium declined following either acid pepsin or acid saline pretreatment. Excystation rarely occurred in either trypsin or bile salts alone. Dissolution of the outer cyst occurred in TB medium thus facilitating excystation. Activation of the larva within the inner cyst led to its eventual release through an aperture in the mucoid plug region. Excystation of this species was facilitated by both intrinsic and extrinsic factors. There were considerable differences in excystation events between this species and the related allopatric species, E. trivolvis

Suspensions of embryonated (L2) Toxocara canis and T. cati eggs were maintained under freezing conditions in order to study the impact on their long term viability The eggs had been removed from the uteri of adult Toxocara spp. worms and the suspended in a 0.4% formalin solution before being frozen in 20 ml plastic tubes in the freezer compartment of a domestic refrigerator. Assessment of embryonated egg viability over a period of 34 days was conducted by microscopic examination under a high light intensity Embryonated T. cati eggs were found to exhibit a greater resistance to freezing than those of T. canis. A difference in the size, design of the egg shell or the metabolism of the larval form may have accounted for the observed differences in the percentage viabilities over time between the two species of Toxocara.

The distribution of cobalt in parasitic helminths belonging to the trematodes, cestodes or nematodes was determined by the use of an atomic absorption spectrophotometer. The results of these analyses have demonstrated that growing trematodes (smaller forms) with active oogenesis and spermatogenesis contained more cobalt than older forms (large or very old adults) with empty uteri and large lobulated testes. In cestodes, the neck region of cysticerci and immature proglottids of adults showed more cobalt than the cyst portion of cysticerci and hydatid or mature and gravid proglottids of worms. Similarly, the youngest endogenous daughter cysts of Echinococcus granulosus showed more cobalt in their walls than those of larger forms. The element was found more concentrated in nematode eggs than in adult females, irrespective of species of host.

The structure of the female reproductive tract, and the patterns of oogenesis, fertilization and embryogenesis were examined from two adult female Loa loa (Nematoda: Filarioidea) from Gabon. They were found to be indistinguishable in the two specimens, and almost indistinguishable from the pattern previously described from Dirofilaria immitis, except in chromosome number. Loa loa has 2n=10+X0.

Field study on the biology of Crassicutis cichlasomae Manter, 1936 (Digenea: Homalometridae) was carried out in a small swamp in a limestone factory near Mérida, Yucatán, Mexico. Aquatic snails, Littorina (Littoridinopsis) angulifera, harbouring C. cichlasomae rediae, cercariae and metacercariae, served both as the first and second intermediate hosts. Feeding experiments confirmed the conspecificity of metacercariae from naturally infected snails with adults from naturally infected fish. Gravid C. cichlasomae worms were obtained from experimentally infected fish 19 days post exposure at 22–24°C. Examination of fish from the swamp in Mitza and other localities in the Yucatan Peninsula showed that the cichlids Cichlasoma urophthalmus and C. meeki were definitive hosts of C. cichlasomae. There was no pronounced preference of C. cichlasomae adults for the site of their location in the intestine of the definitive host; a slightly higher proportion (41%) of worms was only found in the anterior third of the gut. The time of miracidium development varied from 18.5 to 27.5 days; different temperature (20.1–35.7°C) or light/darkness regimes influenced only slightly the rate of embryonic development, with shorter development times at higher temperature (34.8–35.7°C) and constant darkness and/or light. With the exception of the sporocyst, all developmental stages are described and figured.

Spermatogenesis and the structure of the spermatozoon of the frog intestinal fluke, Ganeo tigrinum has been examined by electron microscopy. Each testis is covered by a tunica consisting of sustentacular cells and fibrous material. Internally the testis is lined by undifferentiated spermatogonial cells, with cytoplasm rich in free ribosomes. The arrangement of the diverse spermatogonic cell populations is similar to those studied in other digeneans. During spermatogenesis the elongation and spiralling of nuclear materials occurs synchronously in the late spermatid stage. The G. tigrinum spermatozoon appears to be biflagellate due to the presence of two filaments. Between the two filaments is an elongated nucleus; these elements fuse to form the monopartite shaft of the sperm. The spermatozoon of G. tigrinum is characterized by the presence of an unusually long nucleus that even surpasses the length of the mitochondrion. At almost half the length of the spermatozoon there is sharp rotation between first axial filament, mitochondrion and the nucleus. Both the axial filaments show 9+1 arrangement of axonemal units throughout the spermatozoon.

The random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) technique was applied to two closely-related echinostome species, Echinostoma trivolvis and E. caproni, to demonstrate interspecffic polymorphisms of genomic DNA. Band patterns generated using five individual primers showed that these two echinostomes were genetically distinct, although they share genomic DNA to some extent.

Isolates from eight gastrointestinal nematode species parasitic in sheep, cattle and deer were maintained in sheep, to provide eggs in similar faecal environments and to compare temperature and moisture requirements for their development. Faecal cultures were processed at different temperatures (for four species) and moisture contents (for eight species). At 60% of faecal moisture content (FMC), maximal rates of development (expressed as L3/100 hatchable eggs estimated by an extraction technique from the faeves) were observed at 20, 23 and 28°C respectively for Ostertagia leptospicularis, O. ostertagi, Teladorsagia circumcinctaand Trichostrongylus colunriformis. For the eight species, the curves of development rates as functions of FMC were Gaussian, without modification between 18 and 28°C. Optimal developments were when the FMC ranged from 57 to 68%; low development of 1L3/100eggs were observed when the FMC ranged from 85 to 95% and from 25 to 55%. The main differences between species were in the ability of the eggs of Teladorsagia circumcincta, Trichostrongylus colubriformis, T. vitrinusand Chabertia ovina to develop at lower FMC than Haemonchus contortus, O. ostertagi, O. legptospicularis and Cooperia oncophora.

The in vitro cultivation technique of Echinococcus granulosus protoscoleces usually states the necessity of a biphasic medium with a solid protein substrate for strobilar development to take place; otherwise, in a monophasic medium, protoscoleces follow a vesicular development. However, in some monocphasic cultures, the development of several strobilate individuals (in different quantities and stages of development, depending on the culture) were observed. The only known diference form cultures made previously and snice, where the development was vesicular, was the batch of foetal calf serum used in the constitution of the liquid medium, and this is presumed to be the cause of this unexpected strobilar development.

Larval Echinococcus multilocularis was found in Clethrionomys rex in Hokkaido, Japan. C. rex is a new host record for E. multilocularis. The cysts were filled with numerous protoscoleces suggesting a potential role of this vole in a natural cycle of transmission.

The life history of Grysoma indica n.sp., a psilostome trematode, obtained experimentally in ducklings, after feeding with metacercariae occurring in the snail Thiara tuberculata, is elucidated. Natural infections with cercariae were found in T. tuberculata, collected from a freshwater stream at Visakhapatnam, India. Metacercarial cysts were found in the same and other species of snails in the locality. The new species differs from other species of the genus in the sucker proportions, position of the testes and distribution of the vitelline follicles.

Eleven artificial infections of oribatid mites of the genusScheloribates with Moniezia expansa eggs were made. The percentage of surviving mites in the infected groups was lower (62 to 82%) than in the uninfected control group (90%). None of oribatids with cysticercoids in their body cavity contained mite eggs. The established prevalence and average cysticercoid number in surviving mites were 50.00 to 95.12% and 1.3 to 2.8 respectively.

The outer cysts (Oc) of Fasciola gigantica metacercariae (Mc) were separated in an aqueous two-phase system composed of polyethylene glycol and dextran in distilled water. A large number of separated Mc without Oc were recovered in the bottom layer rich in dextran in the system. Ten separated Mc in the layer were used to inoculate the mouse with a syringe and juveniles were recovered from the animals on the 14th day. When the number of juveniles recovered was compared with that from the mice infected orally with the same number of Mc, there was a significant difference between them (P <0.05). The former method is easier than the latter for inoculation.

Infection of Salamandra salamandra larvae (Amphibia: Urodela) with the fish acanthocephalan Pomphorhynchus laevis was detected in a fish-free mountain brook. Gammarus fossarum was found to be the intermediate host. The parasites were probably inadvertently introduced through fish breeding practices. Evidence was obtained that Pomphorhynchus laevis persists, at least for several months, in postmetamorphic fire salamanders.

The infectivity of the eggs of Asian Taenia sp. for humans is not known. Using baboons (Papio hamadryas) as a model to extrapolate the findings, three animals were exposed per os with 1000, 10,000 and 50,000 infective eggs of theAsian Taenia sp. The serological, biochemical, haematological and parasitological (based on necropsy) results show that baboons are refractory to the infection. It is concluded that the Asian taeniid eggs may fail to develop in man.

A simple procedure of gel-filtration was used to purify microfilariae of the cattle parasite, Setaria digitata from its eggs. The eggs of S. digitata were also isolated from the female worms by picking out the uterine canal. Gel-filtration gave a recovery of 70% for microfilariae.