Lysozyme secretion from macrophages of Schistosoma mansoni-infected mice was time dependent, rising significantly from the 8th week post-infection, the macrophages thereafter exhibiting very high levels (> 90%) of schistosomulicidal activity. Despite the ability of lysozyme to kill schistosomula in vitro, the concentrations required for such killing were several hundred-fold to several thousand-fold higher than those detected in the supernatants from infected-mice macrophages cultured with or without schistosomula. An in vitro lysozyme inhibitor, N, N, N-triacetyl chitobiose, did not abrogate the cytotoxic ability of macrophages from schistosome-infected mice, but an inhibitor of arginine-dependent cytotoxicity, NG-monomethyl arginine, markedly inhibited schistosomulicidal activity. Evidently, concentrations of ambient lysozyme from macrophage cultures are too low to affect schistosomula in culture, while the main schisto-somulicidal pathway in vitro seems to be arginine dependent.

During the course of preliminary studies on the helminth fauna of local freshwater fishes two species of Crepidostomum, obtained from the intestine of brown trout, were identified as C. farionis (Müller) and C. metoecus Braun. Although C.farionis is a common parasite of the fresh-water salmonoid fishes of the Northern Hemisphere, in Ireland it has been recorded only from trout (Salmo trutta). The first Irish specimens were recorded by Southern (1912) as Stephanophiala laureata (Zeder), and came from fish from a stream in Clare Island and from the Owenwee River, Westport. Later, Vickers (1951) found that trout from the River Moyola, Co. Londonderry, and River Ravarnett, Co. Down, were infected with this species. Prior to the present study, C. farionis was the only representative of the genus to have been recorded from the British Isles. C. metoecus is therefore a new record, not only from Ireland, but from the British Isles as well. Elsewhere it is known to occur in Sweden [ = C. suecicum Nybelin, 1933], Austria, and possibly also in Thuringia, where cercariae were found which Nöller (1928) assigned to C. metoecus.

1. Moles were collected from four main areas, Suffolk, Cheshire-Staffordshire, Westmorland-Yorkshire, and south-west Scotland, and examined for the presence of flukes. Three species were found: Itygonimus lorum from all the areas (and in one mole from Oxford); I ocreatus from Suffolk; Omphalometra flexuosa from Suffolk and Cheshire-Staffordshire.

2. The sex of the host has no effect on the incidence of parasitism with flukes.

3. I. lorum is almost exclusively a parasite of the lower half of the intestine, whereas I.ocreatus and O. flexuosa are predominantly parasites of the upper half of the intestine.

4. The commonest number of flukes of any of the three species to find in a mole is one, though two individuals is almost as common a number in the case of I. lorum. Nevertheless, large populations of I. ocreatus or O. flexuosa and moderate numbers of I. lorum are on occasion found in one mole.

5. Premunition does not occur with infestations of I. lorum and probably not with I. ocreatus and O. flexuosa.

6. The distribution of each species even within an area where it occurs is very patchy and local. This is probably bound up with restricted movement of the hosts, whether final or intermediate, and may also be associated with the influence of soil conditions on the intermediate hosts.

7. There appears to be no seasonal variation in the presence of flukes in moles.

8. Simultaneous infestation with more than one species of fluke is rare. It is possible for O. flexuosa to live in company with I. lorum or I. Ocreatus, but the two Itygonimus species were never found together in the same mole.

9. The presence of flukes in a mole has no effect on the rest of the intestinal helminth population of the host.

Diclidophora merlangi was found to consume oxygen under a variety of experimental conditions. The Qo2 of homogenates was 0.415 μl oxygen consumed/mg wet wt/h. Oxygen uptake was reduced in the presence of inhibitors: cyanide 0.1 mM and 5.0 mM, 100%; rotenone 10−6 M, 56%; antimycin A10−6 M, 63 %; malonate 10 mM, 36 %; arsenite 5 mM, 46 %; fluoroacetate 5 mM, 47 %. Worms died after 1 h incubation in 1 mM cyanide. It is suggested that these data provide evidence for the existence of a functional TCA cycle and respiratory chain of the classical pattern in this fluke.

Canine leishmaniosis (CanL) is a major veterinary concern and a public health issue. Serological data are essential for disease management. Several antigens used in serological assays have specificity related problems preventing relevant seropositivity values establishment. Herein we report significant seropositivity level disparity in a study cohort with 384 dogs from eight countries, for antigens traditionally used in CanL – soluble promastigote Leishmania antigens (SPLA) and K39 recombinant protein (rK39): 43·8 and 2·9% for SPLA and rK39, respectively. To better understand the reasons for this disparity, CanL-associated serological response was characterized using, for complement serological evaluation, a ubiquitous antigen – soluble Escherichia coli antigens (SECAs). Using cohorts of CanL dogs and dogs without clinical evidences of CanL from non-endemic regions of Portugal, the serological response of CanL animals followed specific trend of seropositivity rK39 > SPLA > SECA absent in non-diseased animals. Using receiver operating characteristic curve analysis, these characteristic trends were converted in ratios, SPLA/SECA, rK39/SECA and rK39/SPLA, that presented high predictive for discriminating the CanL cohort that was potentiated when applied in a scoring system involving positivity to four out of five predictors (rK39, SPLA, SPLA/SECA, rK39/SECA and rK39/SPLA). In fact, this approach discriminated CanL with similar sensitivity/specificity as reference antigens, diminishing seropositivity in European cohort to 1·8%. Ultimately, non-related antigens like SECA and seropositivity ratios between antigens enable different perspectives into serological data focusing on the search of characteristic serological signatures and not simple absolute serology values contributing to comprehensive serological status characterization.

The spread of invasive, non-native species is a key threat to biodiversity. Parasites can play a significant role by influencing their invasive host's survival or behaviour, which can subsequently alter invasion dynamics. The North American signal crayfish (Pacifastacus leniusculus) is a known carrier of Aphanomyces astaci, an oomycete pathogen that is the causative agent of crayfish plague and fatal to European crayfish species, whereas North American species are considered to be largely resistant. There is some evidence, however, that North American species, can also succumb to crayfish plague, though how A. astaci affects such ‘reservoir hosts’ is rarely considered. Here, we tested the impact of A. astaci infection on signal crayfish, by assessing juvenile survival and adult behaviour following exposure to A. astaci zoospores. Juvenile signal crayfish suffered high mortality 4-weeks post-hatching, but not as older juveniles. Furthermore, adult signal crayfish with high-infection levels displayed altered behaviours, being less likely to leave the water, explore terrestrial areas and exhibit escape responses. Overall, we reveal that A. astaci infection affects signal crayfish to a much greater extent than previously considered, which may not only have direct consequences for invasions, but could substantially affect commercially harvested signal crayfish stocks worldwide.

The present study describes Trichuris trichiura infections in a cohort of children over a period of approximately 5 years, and examines the relationships between changes in infection intensity and changes in parasite-specific isotype responses (measured by ELISA). The decrease in mean infection intensity with time was mirrored by time-dependent changes in IgG subclass responses, with IgA and IgE levels remaining relatively constant in the cohort. At the individual level, changes in infection intensity between the initial and final time-points correlated positively and significantly with changes in all isotype levels with the exception of IgA.

The identification of Ixodes frontalis Panzer, 1795, from earlier descriptions presented great difficulty, more particularly as the species is rare. There are two specimens in the British Museum (Natural History), and the description by Schulze (1933) is from a single specimen in the Sofia Museum. The rarity of the species led Schulze to write that ‘Die Art ist in Deutschland seit den Zeiten Panzers nicht mehr wiedergefunden worden’. Senevet (1937), who considers I. frontalis synonymous with I. brunneus Koch, 1844, wrote that the species occurred in St Genies-de-Malgoires in France, but this information was taken from Nuttall, Warburton, Cooper & Robinson (1911).

Populations of Ostertagia ostertagi established from fresh larvae and from larvae stored at 4 °C for up to 12 weeks contained about 10% inhibited early 4th-stage larvae. This value rose to 21% after 16 weeks, due to an increase in numbers of inhibited larvae while adult numbers remained unchanged. Storage at 15 °C had no effect. In the case of larvae stored at 4 °C for 8 weeks, increasing the larval dose to 90000 had no significant effect on the proportion of the dose which was inhibited. The response to low temperature storage was much weaker than in previously reported studies on British populations, which accords with our earlier conclusion that low temperature cannot be the effective stimulus for inhibition in Australia.

In this in vitro study we investigated whether previously described in vivo plasma-associated effects, that occurred in the period shortly after penetration of Trichobilharzia ocellata into the snail host Lymnaea stagnalis (1.5–72 h post-exposure; p.e.) were direct and/or indirect effects of parasite-derived factor(s). It was investigated whether the effect is mediated by the central nervous system (CNS) of the host. Phagocytic activity of the haemocytes was taken as a parameter for the activity of internal defence of the host. A number of preliminary experiments were performed. When the supernatant of in vitro cultured parasites (33 h; corresponding with their developmental stage in vivo when plasma-associated activation was found) was applied directly to monolayers of haemocytes, it appeared to enhance their phagocytic activity. No direct effect, however, was found with a supernatant of parasites cultured for a longer period of time (72 h; when, in vivo, a plasma-associated suppression was found). In this case, indirect suppression was detected: the parasites appeared to have released a factor that induced the CNS of the host to release material suppressing the activity of the internal defence system of the host. To date the nature of this factor is unknown.

The erythrocytic stages of Plasmodium falciparum from Aotus trivirgatus were grown in Mill Hill medium. Significant invasion of erythrocytes was obtained by a subculture technique. This invasion, by parasites grown in Aotus erythrocytes, was greater when human erythrocytes were added to the cultures than when parasites were allowed to invade Aotus erythrocytes. This difference appeared to be a function of the properties of the erythrocyte and was not serum dependent.

The cyclooctadepsipeptide PF1022A derived from the fungus, Mycelia sterilia, is characterized by a broad spectrum of activity against different parasitic gastrointestinal nematodes of livestock. In the present work the anthelmintic activity of PF1022A against Heligmosomoides bakeri, a widely used laboratory model was studied. Albendazole, ivermectin and levamisole served as reference. In vitro, PF1022A showed low activity on embryonation but significantly inhibited egg hatch (10 and 100 μg/ml), whereas albendazole (10 and 100 μg/ml) revealed statistically significant inhibitions of both embryonation and egg hatch. PF1022A (1–100 μg/ml) completely inhibited larval movement at most examination points. Comparable significant anthelmintic activity on the larval stages of H. bakeri was observed with levamisole (48–100%), while slightly lower activities were observed with ivermectin (20–92%) and albendazole (0–87%) at 1–100 μg/ml. PF1022A and levamisole significantly inhibited motility and egg release of adult worms, while albendazole and ivermectin failed to demonstrate activity. Significant worm burden reductions were achieved with PF1022A, levamisole and ivermectin in vivo. For example, at 0·125 mg/kg PF1022A a worm burden reduction of 91·8% was observed. The use of drug combinations did not further enhance the in vitro and in vivo activity of PF1022A. In conclusion, further investigations are warranted with PF1022A, as the drug is characterized by significant larvicidal and nematocidal activity in vitro and in vivo.

The two subjects considered in this paper are of practical importance to those interested in research of the kind carried out at the Human Trypanosomiasis Research Institute, Uganda. Their discussion would seriously encumber a report on experimental work and would distract the reader's attention from the main theme. The subjects are therefore dealt with separately, since they bear on all work, past and present, carried out at the Institute.

A two-colour flow cytometry technique was used to assess killing of Giardia muris trophozoites by rabbit anti-trophozoite antibodies and complement. Binding of rabbit antibody to trophozoites and killing of trophozoites were documented by flow cytometry, after incubating the organisms with fluorescein-conjugated anti-rabbit IgG and propidium iodide (PI). Percentages of PI+ (dead) trophozoites ranged from >80%, after incubation with rabbit antiserum and complement, to <30%, after incubation with complement alone. The assay technique may be applicable to studies aimed at determining whether intestinal antibodies from Giardia-infected mammals can kill Giardia trophozoites.

This study examines the effects of host age and sex on the frequency distribution of Brugia malayi infections in the human host. Microfilarial (mf) counts for a large data base on the epidemiology of brugian filariasis in Shertallai, Kerala, South India are analysed. Frequency distributions of microfilarial counts partitioned by age are successfully described by zero-truncated negative binomial distributions, fitted by maximum likelihood. This analysis provides estimates of the proportion of mf-positive individuals who are identified as negative due to sampling errors, allowing the construction of corrected mf age–prevalence curves, which indicate that the observed prevalence may under-estimate the true figures by between 18 and 47%. There is no evidence from these results for a decrease in the degree of over-dispersion of parasite frequency distributions with host age, such as might be produced by the acquired immunity to infection. This departure from the pattern in bancroftian filariasis (where there is evidence of such decreases in over-dispersion; Das et al. 1990) is discussed in terms of the long history of filariasis control (and consequently low infection prevalence) in Shertallai.

Small subunit (SSU) rDNA has been sequenced from a microsporidium, identified as a member of the genus Bacillidium obtained from an oligochaete. The length of the amplified PCR product was 1386 bp which is currently the longest microsporidium SSU sequence known. Phylogenetic analysis using 28 microsporidia SSU sequences, using 3 different tree-building methods indicated that Bacillidium sp. may be one of the earliest branches on the microsporidia tree. However, bootstrapping failed to give a high score (more than 50%) for the position of Bacillidium sp. The branch leading to Bacillidium sp. was long, indicating that this species is not closely related to any of the other microsporidia so far studied by means of rDNA.

Infectivity of Trichinella pseudospiralis in Chinese hamsters was greater than that of Trichinella spiralis. Concurrent infection with these two species of parasite was accompanied by an increase in infectivity of T. spiralis. The infectivity of T. pseudospiralis, but not that of T. spiralis, was significantly influenced by host age. Regardless of host age, T. pseudospiralis was more infective for the Chinese hamster than was T. spiralis. Early during infection, enteritis (myeloperoxidase activity) in hamsters infected with T. pseudospiralis alone was significantly less than that seen in animals infected with T. spiralis alone or with both species concurrently. Myositis in hamsters infected with T. pseudospiralis alone was significantly less on days 14, 17 and 25 post-infection (p.i.) than that observed in concurrently infected or T. spiralis-infected animals. On days 11 and 14 p.i. inflammation in diaphragm muscle from concurrently infected hamsters was significantly less than that seen in animals infected with T. spiralis alone. Muscle histology supported these chemical data on myositis. Suppression of the host inflammatory response against early muscle-stage larvae of T. pseudospiralis underlies the greater infectivity of this parasite for the Chinese hamster.

Small spines of maximum size 0.28 μm × 0.5 μm have been found all over the shells of the eggs of Schistosoma mansoni and S. haematobium. The small spines on S. haematobium eggs are less pointed than those on S. mansoni eggs. They consist of inner and outer parts made up of subunits, and they are continuous with the main part of the shell underneath. S. mansoni eggs still within the blood vessels of the gut have extracellular material between the spines and there is cell debris over them. The scanning electron microscope shows the increased surface area of the egg shell due to the small spines.

I wish to thank many people for their help with this work and in particular Dr F. Hawking, Dr S. R. Smithers and Mrs. L. Ebden.

Apophallus brevis metacercariae localize in parasite-produced cysts mainly in the myotomes of Perca flavescens. The host response induced by this parasite is very intense and leads to the formation of an elaborate host-formed capsule of material which is very similar if not identical to host bone. This capsule is pierced by two canals situated at opposite poles in the cyst and enables the parasite to escape from this host capsule on being ingested by a definitive host. Successive layers of melanocytes and connective tissue, containing lipid droplets, are also present around the bony capsule. Histochemically this bony capsule and the fish bone are virtually identical but there are slight organizational differences in the capsule tissues compared to the fish bone. It is postulated that the formation and arrangement of the capsule may be influenced by the parasite and may not therefore be a defensive development by the host.