These studies address current controversies over the site(s) of challenge attrition in the murine irradiated vaccine model of immunity to Schistosoma mansoni. Two possibilities have been investigated. Firstly, that the site of death of the radiation-attenuated schistosomes used to vaccinate the mice may vary in different laboratories and secondly, that the skin sites selected for presentation of the immunizing and challenge parasites may influence the final site at which immunity is effected (i.e. ear/abdomen vs tail/tail). The migration of radiolabelled cercariae exposed to 0, 20 or 50 krad of gamma irradiation from the NIMR 60Cobalt source was examined in CBA/Ca mice by squashed organ autoradiography. Unirradiated parasites all migrated from the skin to the lungs, and 65% moved on to the liver. Migration of parasites attenuated by exposure to 20 krad of gamma irradiation was delayed, but 76% finally reached the lungs; only 1% was recruited to the liver. The majority of 50 krad attenuated parasites died in the skin, with only 4% accomplishing migration to the pulmonary vasculature. The major site of death (and by implication of antigenic stimulation) of the 20 krad attenuated NIMR strain S. mansoni used routinely for vaccination purposes in our laboratory, is thus the lungs, a finding that does not explain the fact that immunity is mediated primarily in the skin in our model system. Site elimination experiments and squashed organ autoradiography showed conclusively that, irrespective of the skin sites chosen for presentation of the immunizing and challenge population of worms, NIMR challenge parasites are killed predominantly in the skin of vaccinated CBA/Ca mice. Moreover, qualitative and quantitative histological examination of the challenged tail skin of vaccinated mice revealed that inflammatory reactions comprising mononuclear cells and eosinophils develop in this site and function to trap and eliminate challenge larvae, despite a reported reduction in antigen presenting cells in this region.

Enzyme electrophoresis was conducted on 10 Schistosoma mattheei adult worm samples, comprising 270 individuals, collected from cattle in the Eastern Transvaal Lowveld. Glucose-6-phosphate dehydrogenase (G6PDH) was studied in all the samples and phosphoglucomutase (PGM) and malate dehydrogenase (MDH) in five populations each. Only one population was polymorphic for G6PDH. In this population, in addition to the allele found in all the other samples, a second allele occurred with a similar Rf value to S. haematobium. The two alleles were in Hardy-Weinberg equilibrium. MDH-1 exhibited two alleles. However, these alleles were not in equilibrium. In certain populations, heterozygotes occurred together with homozygotes of one of the alleles only. PGM was monomorphic in all the populations studied.

The structure of the male reproductive system of Schistosoma margrebowiei as viewed by light, scanning and transmission electron microscopy is described. The cirrus tube opens at the genital pore without the presence of a cirrus and is spongy and leaf-like. The structure of the germinal and non-germinal cells of the testes are described. The spermatozoon consists of a head, without an acrosome, and a flagellum with a 9+0 arrangement of microtubles in the axial filament. A large mass of mitochondria is situated in the anterior end of the head and cortically arranged longitudinally running microtubles are present. The apical region of the epithelial cells of the vas deferens extends into the lumen of the duct forming convoluted lamellae. This arrangement, together with the presence of dense bodies within the cells, suggests that these cells have a secretory function.

The pattern of transmission of human schistosomiasis was studied in Amagunze Village, eastern Nigeria, during 1986–1987. The prevalence of Schistosoma haematobium in 119 schoolboys aged 5–12 years was 79%. The geometric mean of intensity of infection was 49 eggs/10 ml urine and the frequency of visible haematuria was 25·2%. No S. mansoni infections were demonstrated. A marked seasonality in population density of Bulinus truncatus, B. forskalii and Biomphalaria pfeifferi was demonstrated with reduced densities during the late rainy and early dry seasons. Schistosoma sp. infected B. truncatus were found in the late dry and early rainy seasons in 2 out of 7 major human water contact sites studied. Seasonality and focality of transmission of S. haematobium and its high endemicity in the area were thus demonstrated.

The role of macrophages or eosinophils on the expression of sex difference in the susceptibility to a primary Brugia pahangi infection in C57BL/6 mice was investigated by using a macrophage blockade technique (carbon treatment) or a histamine type 1 (H1) receptor antagonist (promethazine). Carbon treatment remarkably inhibited macrophage exudation, reduced the resistance of female mice, and completely abolished sex difference in the susceptibility to B. pahangi infection. Although promethazine treatment inhibited eosinophil exudation, it caused only a little increase (not significant) in the recovery rate of worms. These results suggest that macrophages have more important role(s) than do eosinophils on the expression of sex difference in the susceptibility to a primary B. pahangi infection in C57BL/6 mice.

Infective larvae of Onchocerca lienalis and O.volvulus implanted subcutaneously within micropore chambers into laboratory hosts moulted to the fourth stage (L4) and underwent limited development and growth. Similar recoveries of O. lienalis L4 larvae in the range of 33–66% were obtained from chambers implanted into CBA and BALB/c strains of mice, jirds, and the natural bovine host. A relatively constant proportion of larvae survived up to 24 days post implantation and thereafter recoveries declined, although some worms were still alive after 96 days. Recoveries of O. volvulus L4 larvae from chambers given to normal or T-cell deprived mice were equivalent to one another and to those obtained with O. lienalis. Moulting of O. lienalis in chambers was observed on days 3 and 5, in close accordance with the timing of the third moult in cattle following systemic infection. Moulting of O. volvulus occurred between days 3–6. Morphological changes in developing larvae included a small but significant increase in length, a transient increase in width, and early development of the spicular primordia and genital tube. L4 larvae of O. lienalis, but not those of O. volvulus, exhibited 3 distinct caudal papillae not present on infective larvae.

Domestic chicks experimentally infected with Echinostoma caproni for 2 weeks showed a dilated ileum, unkempt feathers, watery diarrhoea, and weight loss. The ileum from infected and control chicks was fixed in 10% neutral buffered formalin, and prepared as 10 μm paraffin sections stained in haematoxylin and eosin, Papanicolau, periodic acid-Schiff, picro-ponceau, and alcian blue. The infected ileum showed atrophic villi, hypertrophied circular musculature with collagen-like fibres and haemorrhagic zones. The brush borders of epithelial cells and goblet cells were absent in the mucosa of the infected ileum. Worms in contact with host mucosa showed tissue plugs in the suckers. The cephalic spines of worms abraded the host mucosa.

An echinostome cercaria (? Cercaria spinifera La Valette, 1855) with 37 collar spines and paraoesophageal glands has been recorded for the first time in Britain from the gastropod Planorbarius corneus. The cercariae penetrate into and encyst in planarians. Observations made on cercariae during penetration indicate that the paraoesophageal glands are used to enter the body of the planarian and that the so-called penetration glands have some other function. Gastropod molluscs may also serve as second intermediate hosts, but there is evidence to indicate that anatomically similar cercariae from different host individuals vary in their second intermediate host preferences.

Comparative ultrastructural studies have been made of newly excysted metacercariae and worms recovered from abnormal (rats) and normal definitive hosts (dogs). Worms from rats survived for prolonged periods without any growth or development in muscles of the host. They appeared to resemble metacercariae in general features, although ultrastructural observations revealed differences in the composition of tegumental granules and the development of the excretory bladder and caeca. Worms from dogs showed well-developed morphology in association with active energy metabolism and biosynthesis.

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3–4 times the weight in control animals by weeks 3–7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3–4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.

A case is presented of infection by Oesophagostomum, a nematode worm, producing a cutaneous nodule in man. Of the 70 individual cases reported in man it is believed that this is the first in which the worm has produced a lesion outside the gastro-intestinal tract and without evidence of bowel infection. This finding suggests either that the worm is able to achieve direct skin penetration or that it can be disseminated from the bowel via the bloodstream or the lymphatics. The pathology caused by Oesophagostomum and the possible modes of infection are discussed in relation to studies in animals, particularly simians and cattle.

Hydatid fluid collected from the lungs and livers of sheep and humans was analysed for protein and lipid composition. There were no marked differences in the composition of these parameters and the major lipids were triglycerides and diglycerides. The phospholipids, which formed the minor fraction, were mainly phosphatidyl choline and phosphatidyl inositol. Cholesterol present was in the free form.