The analysis of restriction fragment length polymorphisms (RFLPs) was applied to distinguish several kinds of Anisakinae larvae, Anisakis larvae (type I) collected from two different paratenic hosts, Anisakis larvae (type II) and Contracaecum larvae. The patterns of the two different paratenic host-derived DNA of Anisakis larva (I) were exactly the same in hybridized fragments generated by six endonucleases. The quite different patterns in RFLPs of genomic DNA were observed among the Anisakis larva (I), Anisakis larva (II) and Contracaecum larvae. The results suggest that the RFLPs analysis may be useful for distinguishing Anisakinae larvae and clarifying the relationships between Anisakis larvae and their adult worms.

During the intramolluscan larval development of Schistosoma haematobium (Algerian strain) in Bulinus truncatus, two replication processes of daughter sporocysts occur. Replication by direct sporocystogenesis appears more important than sporocystogenesis post cercariogenesis. These mechanisms assure a periodic renewal of the sporocyst stock in the snail host and seem to be synchronized with the development of cercarial generations. The succession of several generations of cercariae is responsible for the alternation of high and low periods of productivity.

The scheme proposed for the intramolluscan development of S. haematobium is compared with those described for S. mansoni and S. bovis and interpreted in terms of demographic strategies adapted to a better exploitation of the snail host.

No significant difference in cercarial production was noted when Biomphalaria glabrata from Brazil were exposed to one or several miracidia of Schistosoma rodhaini from Burundi, even though the dynamics seemed different. The minor differences can be explained by the intramolluscal larval development of this parasite characterized by the production of a high number of daughter sporocysts over a long period.

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.

Crude saline extracts of Trichinella spiralis and T. pseudospiralis infective larvae were studied by Western blot analysis using a monoclonal antibody, named ES/TA2 and produced against T. spiralis larvae. This monoclonal antibody recognized seven major antigenic components in T. spiralis larvae with apparent Mr: 45, 48, 50, 68, 70, 92 and 105 kDa and five in T. pseudospiralis larvae: 38, 50, 70, 72 and 92 kDa. SDS-PAGE of both extracts did not reveal appreciable differences in the range of molecular weights recognized by ES/TA2. These facts show the existence of immunological differences among proteins with apparently identical molecular weights.

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.

An eosinophil chemotactic factor (ECF) was partially purified from plerocercoids of Spirometra erinacei by a combination of anion-exchange chromatography on DE52 and gel filtration on Sephacryl S–200. The molecular weight of ECF was estimated to be 25 000–45 000 by high-pressure liquid chromatography. The ECF was bound with concanavalin A-Sepharose. The ECF was sensitive to periodate oxidation and to heating (56°C, 30 min). On isoelectric focusing, eosinophil chemotactic activity was clearly revealed at pI 4·1. These results suggest that ECF of S. erinacei plerocercoid is an acidic glycoprotein. An intradermal injection of ECF induced eosinophil attractions in the normal guinea pig skin.

The callitrichid primates, Callithrix jacchus jacchus (the marmoset) and Saguinus labiatus (the tamarin) were inoculated with infective larvae of Brugia malayi and B. pahangi. Microfilaraemia at low levels developed in 3 out of 4 C. j. jacchus infected with B. malayi and living or dead adult worms found in all 4. Only one of 4 C. j. jacchus became microfilaraemic (mf + ve) when given B. pahangi and adults were found in two. Of 4 S. labiatus given B. pahangi one became very lightly mf + ve and adults were found in 3. It is concluded that these animals are not suitable hosts for chemotherapeutic experiments.

The technique of allozyme electrophoresis was applied to species of Onchocerca from cattle to increase the number of enzyme loci established and therefore provide a genetic basis for a rational species-level taxonomy. Twenty-three enzyme loci were established and provided unequivocal genetic evidence for the taxonomic validity of Onchocerca gibsoni, O. gutturosa and O. lienalis. Furthermore, the diagnostic enzyme markers detected form the basis for identification of life-cycle stages, individuals and species and population structure analyses.

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 sensitivity and specificity of double immunodiffusion (DID), indirect haemagglutination test (IHA), immunoelectrophoresis (IEP), counterimmunoelectrophoresis (CIEP) and enzyme-linked immunosorbent assay (ELISA) were evaluated and compared using saline extracted of Taenia solium larval scolex and its Sephadex G-200 fractionated 1st and 2nd peak as antigens. Various immunodiagnostic tests gave different results with different antigens. Highest sensitivity (92·5%) was obtained with ELISA using 1st peak antigen and lowest sensitivity was obtained with DID. However, 88·4% and 84·6% sensitivity was obtained with IHA and CIEP respectively using scolex antigen. CIEP gave better results as compared to IEP. Crude antigen gave high sensitivity but less specificity. It was concluded that CIEP can be used as a field test for the anti-mortem diagnosis and ELISA can be employed for laboratory confirmation of T. solium cysticercosis in pigs using frationated 1st peak antigen.

The prevalence and relative density of the monogenean Paradiplozoon homoion, were monitored over one year in populations of roach, Rutilus rutilus, captured in a thermally raised artificial lake located outside a nuclear power station and in a nearby reference locality. Recruitment of P. homoion started earlier in the warmer lake. A temporal shift of the life-cycle was thus observed but there were no differences between the total prevalence or the total relative density of the parasite in the two areas. Since there is no evidence of parasite-induced host mortality, or for the development of protective immunity, the main regulatory process in the heated area are most likely an increased mortality due to reduced thermal tolerance of the adult parasite.

The importance of larval viability in relation to the success of recovery techniques and to the interpretation of histological and migration studies was tested using mice infected with Toxocara pteropodis, T. canis and T. cati. Little difference was found in total numbers of viable larvae recovered from tissues incubated for 18 hours in 0·85% saline, 2% trypsin or 1% pepsin, but the rates of larval egress did vary. The recovery of dead larvae by digestion techniques was much lower. Larvae migrated in tissues undergoing fixation, which influenced histological findings. Larvae of T. canis did not undergo significant peritoneal migration in acutely-infected mice, but did penetrate their intestinal walls in large numbers within 4 hours of death. The implications of these findings in experimental studies are discussed.

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.

Adult males and females of Trichuris globulosa, an intestinal nematode parasite of goats, were studied for their lipid composition, capability of incorporation of (Na)-1-14C-acetate into different lipid classes and the activity of certain key enzymes of lipid metabolism. The parasite possesses a large variety of lipids including certain complex lipids. These are phosphatidylcholine (PC), diphosphatidylglycerol (cardiolipin), lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), phosphatidylserine (PS), phosphatidylinositol (PI), plasmalogens (choline+ethanolamine), mono-, di- and triacylglycerols, free and esterified cholesterol, non-esterified fatty acids (NEFA), gangliosides, cerebrosides (glycosyl ceramide) and sulphuric acid esters of cerebrosides (sulphatides). The females contain more lipids than males, particularly the acylglycerols and phospholipids, possibly to meet the energy requirement and structural entities for the daily production of large numbers of eggs. Incorporation studies of labelled substrate, sodium-1-14C acetate demonstrate that the adult female has extremely active mechanisms for biosynthesizing these lipids. Most of the labels are found in PC, PE, SM, acylglycerols, NEFA, gangliosides, cerebrosides and sulphatides. Cholesterol, although a minor component of the parasitic lipids, incorporates large amount of label and also undergoes fast turnover. Kinetic analysis of the incorporation by measuring the rate constant (k) and half life (t½) reveals that gangliosides are the fastest biosynthesizing and turning over lipids, although they constitute only 0·1% of the total lipids. The presence of important enzymes of lipid biosynthesis, glucose-6-phosphate dehydrogenase, malate dehydrogenase and hydroxymethyl glutaryl-CoA reductase and an enzyme of lipid ester hydrolysis, triacylglycerol lipase, is also established in T. globulosa. Michaelis-Menten kinetic characteristics of the parasitic enzymes (Km, Vmax, v and the first order rate constant, k) are comparable with those of rat liver homogenates.

The effect of intestinal flora on the establishment, development and pathogenicity of Ascaris suum larvae in piglets (Large White breed) was investigated. The infected piglets with Ascaris and Escherichia coli showed signs of pneumonia, cough with respiratory difficulties initially even though these moderated with time. They lost appetite and showed signs of unthriftiness with loss of weight. The packed cell volume was normal but the differential leucocyte counts of the pigs infected with Ascaris larvae and bacteria had high neutrophils, unlike the very high lymphocyte count observed in piglets with ascarids only. The piglets had generalized serous atrophy of body fat. The pericardial and perirenal fats were gelatinous. There was a firm and nodular grey and red hepatization with abscess pockets in the intermediate and anterior one third of the diaphragmatic lobes of the lungs. The liver contained greyish-white and depressed focus immediately dorsal to the area of attachment to the gall bladder with multifocal areas. There was no significant gross lesion in the control animals. Cultural and microscopic examinations of some internal organs of the infected animals showed that bacteria were carried to the lungs by the migrating Ascaris larvae. The combined synergistic effect of Ascaris larvae and E. coli was also investigated and it was concluded that the two agents (A. suum larvae and E. coli) worked together synergistically.

The effect of fatty acids was studied on the developmental direction of Strongyloides ratti first-stage larvae (L1). The proportion of third-stage infective larvae increased markedly when L1 were cultured in faeces with added fatty acids such as palmitic (C16), stearic (C18), oleic (C18:1) and linoleic (C18:2) acids. Unsaturated fatty acids were more effective than saturated ones. Moreover, the proportion of infective larvae increased with quantity of linoleic acid but the triacylglycerols of any fatty acid had no effect. These results suggest that these free fatty acids cause physiological changes that determine the developmental course of L1 of S. ratti in nature.