Of 10,362 cattle examined in Bangladesh, 4,368 (42·15%) harboured hydatid cysts. One to three-year-old cattle had the lowest (11·34%) and those over nine years old the highest (93·21%) infections. Organ involvement was as follows: liver 35·18%, lungs 32·02%, spleen 0·80%, heart 0·41%, kidney 0·25%, omentum 0·11% and both liver and lungs 31·20%. Fertile cysts occurred in 8·11%, sterile in 74·91%, calcified in 9·43%, suppurative in 6·04% and undeveloped in 1·51% of animals.

Resistance to challenge infection with Trichostrongylus colubriformis was studied in an outbred strain of guinea-pigs. Resistance was conferred by previous infections of 50 or 100 infective larvae and by intraperitoneal, intramuscular and subcutaneous administration of dialysed transfer factor prepared from guinea-pigs infected with T. colubriformis, by intraperitoneal administration of transfer factor prepared from the blood of sheep infected with T. colubriformis and on one of three occasions using transfer factor prepared from guinea-pigs which had not been infected with T. colubriformis. No significant resistance was transferred by administration of antigen prepared from adult T. colubriformis, or by non-dialysed transfer factor, or by dialysed transfer factor prepared from T. colubriformis-infected guinea-pig tissue which had been stored for several months at −20°C.

Volume 56 no. 1, p. 69

The address for Dr. J. W. Mak should be:

Filariasis Research Division, Institute for Medical Research, Jalan Pahang, Kuala Lumpur 02-14, Malaysia.

This project investigated the influence of the age and sex of the host and the level of infection with Nematospiroides dubius on the establishment and duration of a primary infection in the jird. It was found that 30 to 35% fewer worms matured in jirds than in mice and that this proportion was unaffected by the level of infection or by the sex of the host. In contrast the age of the jird was found to be critically important in determining the number of adult worms recovered 14 days after infection. Thus, maximum susceptibility to infection was observed when jirds were 18 to 22 days old. In older jirds susceptibility declined until 30 days after birth and thereafter, when approximately 70% of the infective larvae matured (relative to the number of worms maturing in mice).

The duration of a primary infection in jirds was similar in both sexes but was influenced by the level of infection and by the age of the host at infection. Heavier infections (500 larvae) lasted about 10 days longer than low level infections, and expulsion of the parasite occurred even when the host was infected with only five larvae. The duration of a primary infection was markedly prolonged in neonatal jirds, faecal egg counts remaining positive for 54 to 56 days after infection of 12-day-old jirds.

These results supply some further baseline data for future work on the biology of N. dubius in the jird and they provide support for the involvement of immunological processes in the termination of primary infections of this parasite in mature jirds.

The protein composition of various developmental stages of Dipetalonema viteae was analysed on polyacrylamide slab gels in the presence of sodium-dodecylsulphate. When the total proteins of adult male and female parasites, microfilariae, eggs, and third-stage larvae were compared, apparent qualitative similarities between mature and immature filariae were observed. However, several stage specific components were also identified.

Metacestodes of Taenia crassiceps were cultured in laboratory rats and mice, washed in glycine/hydrochloric acid (Gly/Hcl) buffer pH 2·4 and phosphate buffered saline (PBS) pH 7·2 and a soluble extract of the metacestodes (SEM) was prepared from larvae washed in both buffers. The SEM and the original washings were examined for host IgG and a common host antigen (CHA). CHA was present in both the SEM and Washings but IgG only in the washings and, in metacestodes from mice only in the Gly/HCl washings). Metacestodes washed in Gly/HCl were not viable.

Metacestodes were also maintained in vitro in a peptide nutrient agar and 0·9% saline at 37°C and a SEM was prepared from these; metacestodes from mice had neither host IgG nor CHA but those from rats had CHA but not IgG. SEM prepared from ‘normal’ metacestodes showed that the CHA consisted of at least two entities, only one having a common identity with the IgG. These results suggest that molecules of both host IgG and a common host antigen are present on the tegument of these parasites.

Mature hens were induced to moult and were subsequently found to be resistant to both primary and secondary infections of Raillietina cesticillus, whereas non-moulting birds that continued to lay were susceptible to primary and secondary infections.

The isoenzymes of acid and alkaline phosphatases and their histochemical localization were studied by polyacrylamide disc gel electrophoresis in four species of trematodes: Gigantocotyle explanatum from the liver and Gastrothylax crumenifer from the rumen of water buffalo (Bubalus bubalis) and Echinostoma malayanum and Fasciolopsis buski from the small intestine of the pig (Sus scrofa). Both acid and alkaline phosphatases were present in the tegument, gastrodermis, suckers, testes, ovary, eggs, vitellaria and uterus but alkaline phosphatase activity was demonstrated only in the parenchyma and excretory ducts. Polyacrylamide gel electrophoresis revealed two to four isoenzymes for both acid and alkaline phosphatase.

The prevalence Angiostrongylus cantonensis, a metastrongylid lungworm of rats, was investigated in three common species of rodents in the Greater Bombay area, namely, Rattus rattus, R. norvegicus and Bandicota bengalensis. In all, 737 R. norvegicus, 100 R. rattus and 100 B. bengalensis were examined and the presence of A. cantonensis infection was noticed in R. norvegicus (1·62%). About 800 slugs (Laevicaulis alte) were examined and were found to harbour third-stage larvae of Angiostrongylus.

A single oral dose of 50 mg/kg of oxamniquine administered to mice with mature infections of Schistosoma mansoni gave rise to a hepatic shift and almost total elimination of the male worms. Regression of the reproductive system and a conspicuous reduction in size took place in the residual females which eventually resembled sexually immature adults. A second dose of oxamniquine had no apparent effect on these females within a period of 28 days following this treatment and it is suggested that this change in reproductive status is the result of discontinued male stimulation.

In a study of the morphology of the posterior ends of O. tricuspis, it could firstly be recognized that not only the adult females but also the LII to LIV possess five cusps. They have apparently been partly overlooked by microscopic examination because of their appearance in different optical planes.

Dactylogyrus legionensis n. sp., a monogenean parasite from the gills of Barbus barbus bocagei from the Esla river (León, NW Spain), is described and its population dynamics discussed. It differs from the closely related species, D. balistae, in the presence of vaginal armour and in the morphology of the copulatory organ. D. legionensis was found on 30·40% of barbel, with a mean intensity of 13·71 and maximum infection levels in autumn-winter. The prevalence and intensity of infection rose significantly with the age and length of the barbel, and were higher in females than in males. D. legionensis showed preference for the second and first gill arches, sector III and the internal zone of each hemibranch.

The habitat specificity of the acanthocephalan Acanthocephalus clavula in the alimentary tract of eels was studied in natural infections and in fish maintained experimentally under different regimes. The parasite exhibited a preference for a particular region (55 to 65%) of the alimentary canal which did not differ in different species of host, but habitat specificity was not very precise as there was considerable variation between individual hosts and A. clavula was capable of surviving and maturing in all regions of the intestine. The mean position of males was slightly anterior to that of females, and the over-all sex ratio was in favour of females. At high levels of infection the range of the parasites was extended and the mean position was significantly more anterior when compared to single worm infections. The parasite remains in the same site throughout the course of an infection: there was no posterior migration and gravid females occurred in the same proportion in all regions of the intestine. The mean position of the parasite did not change when the host was starved, or maintained in 100% sea water or with reduced aeration or at high temperatures. The results were compared with the habitat specificity exhibited by other species of freshwater fish acanthocephalans, and it was concluded that A. clavula was as adaptable and hardy as its present host, the eel.

The migration of infective larvae of Strongyloides ratti has been examined in C57B1/6 mice after percutaneous infection of the anterior abdominal wall. Lateral migration of larvae through the skin and subcutaneous tissues was not seen. Large numbers of larvae were recovered from the muscles between 2 and 24 hours after infection and larvae were seen in the cerebrospinal fluid 24 and 48 hours after infection. Insignificant numbers of larvae were seen in the blood, serosal cavities, liver, spleen, kidneys, brain or nasopharynx. Larvae arrived in the lungs between 24 and 72 hours after infection and worms were first noted in the small intestines at 48 hours. It is concluded that larvae migrate preferentially to the muscles and CSF before passing to the lungs, but the exact mode of travel is uncertain.

The presence of vitelline cells in male Schistosoma mansoni from both mixed and single sex infections in mice is described.

Ultrastructurally these vitelline cells resemble the mature, Stage 4 cells from normal female worms. As yet no developing vitelline cells (Stages 1 to 3) have been found. The cells do not appear to form complete lobules as in the female.

Ascaridoid nematodes occurring in South American mammals are divided into categories based on their possible origin. The affinities are discussed of five species so far known only from the Neotropical Region. Toxocara alienata (Rudolphi, 1819) is reported from Nasua rufa socialis, Procyon cancrivorus, and Tayassus torquatus. The specimens from T. torquatus are described and found most closely to resemble Toxocara mackerrasae from south-east Asian and Australian rodents. Anisakis insignis from Inia geoffrensis is transferred back to Peritrachelius Diesing, 1851, on account of the structure of the lips and spicules. P. insignis is shown to exhibit remarkable convergence of lip structure with Lagochilascaris turgida from Didelphis marsupialis.

Galeiceps longispiculum (Freitas & Lent, 1941) from Pteronura brasiliensis is confirmed as a species distinct from G. cucullus (Linstow, 1899) and G. spinicollis (Baylis, 1923), but G. simiae (Mosgovoy, 1951) is considered to be a synonym of G. spinicollis. An error in the host record of G. spinicollis is corrected from Cercopithecus leucampyx kandti to Lutra maculicollis kivuana. Ascaris dasypodina Baylis, 1922 from armadillos, including Cabassous unicinctus and Tolypeutes matacos, is redescribed and placed in a new genus Bairdascaris. The question is raised as to whether some species in Lagochilascaris, Galeiceps, and Toxocara may have crossed directly by sea from Africa to South America, rather than entering via North America.