I was delighted to be able to join with so many friends and colleagues, in writing this short paper to mark the retirement of Donald Lee. There are many outstanding milestones in Donald's career. However, I thought that I could perhaps draw special attention to his long and distinguished association with the British Society for Parasitology (BSP), and the journal, Parasitology. He was President of the BSP between 1978 and 1980 and, in recognition of his service to the Society and contributions to the discipline of parasitology, was elected an Honorary Member in 1980. Donald has also had a long association with Parasitology, as a member of the Editorial Board and as a frequent contributor. His first paper in the journal was published in 1958; it described the occurrence of Syngamus sp. in a fieldfare (Turdus pilaris) that had been accidentally killed. At the time of writing, his most recent publication, but I suspect not his last, was a biochemical study on proteins produced by Nippostrongylus brasiliensis, Nematodims battus and Ascaridia galli (Foster & Lee, 1996). Of course, Donald has published in many other journals and authored several books. However, if one considers only those papers published in Parasitology, they provide a record of intellectual vigour and curiosity that has remained undiminished throughout his career.

Detoxification mechanisms in parasitic helminths have not been extensively studied, despite their obvious relevance to drug development and drug resistance. Differences in detoxification enzymes between the parasite and its host may be exploitable in the design of pro-drugs, whilst selective inhibition of the parasites protective enzymes could increase their sensitivity to drug action and also make them more susceptible to the host's defence mechanisms.

This paper summarizes the work of the Onchocerciasis Control Programme (OCP) in West Africa, a programme which over a 22 year history has reduced the public health problems of blinding onchocerciasis in eleven countries of West Africa through vector control and, more recently, ivermectin distribution. The paper emphasizes the different approaches to control the programme has developed in the different parts of the programme area which have been determined by the epidemiology of the disease (savanna/forest form), the migratory characteristics of the vectors, intensity of the disease before commencement of treatment, the combined impact of vector control and ivermectin and the likelihood of infiltration of infective blackflies from outside the programme area. The programme has constantly monitored the impact of operations on the trends in prevalence, incidence, annual transmission potential, ocular morbidity and species of fly populations, and as a result, has identified areas where special interventions are required until the programme comes to an end in 2002. The paper illustrates the changes in intensity of infection as measured by community microfilarial load and annual transmission potential over the duration of the programme control activities. The paper also defines and justifies the control strategies in different areas and identifies areas for special interventions.

Intestinal helminth parasites are responsible for a significant amount of pathology in both humans and farmed animals, resulting in a reduction in the quality of life, and occasionally lethal infection as well as causing decreases in livestock productivity. The importance of these parasites globally has resulted in efforts to understand the mechanisms of the host–parasite interaction epidemiology, and to develop methods for diagnosis and control.

Immune responses to immunization and infection with Trichinella spiralis and T. britovi were studied in NIH high-responder mice. Overall it was shown that T. britovi was the more immunogenic, immunization and challenge with this species giving greater host-protective immunity. This greater immunogenicity was reflected in higher proliferative responses when mesenteric node lymphocytes (MLNC) from immunized mice were restimulated with T. britovi antigens in vitro and in higher levels of T helper 2 (Th2) lymphocyte-dependent specific IgG1 antibody responses against this species. MLNC from mice immunized against T. britovi released more IL-5 when restimulated in vitro, again suggesting a greater T helper 2 subset response, but after infection the highest levels of IL-5 were recorded from MLNC taken from T. spiralis challenged mice. These data are discussed in relation to current understanding of immunological differences between species and isolates of the genus Trichinella.

Introduction of excretory/secretory (ES) products of both infective-stage and newborn larvae of Trichinella spiralis into cultures of primary rat myocytes elicited morphological and structural changes in the myotubes. They appeared more granular, thinner, and failed to form networks. The most prominent lesion was the formation of ‘nodular’ structures, each bearing an enlarged nucleus, along the myotubes. Each node contained numerous cavities enclosed by an intact sarcolemma. Co-culture of myocytes with newborn larvae also elicited nodular formation but each node contained a large central cavity encircled by smaller ones. An immunocytolocalization study using IFAT and laser confocal microscopy showed the presence of parasitic epitopes inside the nodes. However, ES products from adult worms did not affect the myotubes.

No article involving the nematode cuticle can ignore the work of Donald Lee. Since the publication of his book Physiology of nematodes (Lee, 1965), he has provided us with an extensive knowledge of the structure, composition, maintenance and growth of a variety of nematode cuticles and has undoubtedly contributed a great deal to our understanding of this unique and diverse structure.

Ecological changes in the Senegal River Basin (SRB) resulting from the construction of a barrage at Diama, Senegal on the Senegal River to prevent the intrusion of sea water into the river, and a dam at Manantali, Mali on the Bafing River to control the flow of water and to generate electricity, have been responsible for changes in the epidemiology of human schistosomiasis. The introduction of Schistosoma mansoni into the Lower and Middle Valleys of the SRB and subsequent spread of the parasite in the human population is recorded with regard to prevalence and intensity. New foci of S. haematobium are described. The reduction in salinity and change from an acidic to an alkaline environment in the water are beneficial to both the fecundity and growth of freshwater snails and transmission of the parasite. The creation of new irrigation canals and expansion of the rice fields have provided new habitats for intermediate hosts to colonize. The evidence for praziquantel resistance/tolerance by populations of S. mansoni and the possibilities of the development, production and testing of a vaccine against human schistosomiasis are discussed. Future studies will monitor the spread of human urinary and mesenteric schistosomiasis in the SRB, will evaluate further the presence of praziquantel resistance/tolerance in S. mansoni, will examine the heavily infected human population for pathological symptoms and determine the most appropriate methods to control this severe outbreak of human schistosomiasis.

Old lambs (8 months of age) infected with 50,000 L3 of Nematodirus battus had larvae developing normally in their tissues on day 4 post-infection (P.I.), but by day 8 P.I. there were only 4105 ± 1044 worms left in the alimentary tract. Some of these worms contained crystals in their intestine. Eight-month-old lambs treated with dexamethasone and infected with 50,000 L3 of N. battus contained a mean worm burden of 7878 ± 1262 on 18 days P.I. Untreated 8-month-old lambs similarly infected were virtually worm free by day 18 P.I. Peripheral eosinophilia became elevated in the untreated lambs over the course of infection and, at post-mortem, the tissue mast cell and eosinophil counts were much higher than in the dexamethasone treated group. Although the phenomenon of age resistance is thought to have a strong immunological component, there may also be other physiological factors, resulting in fewer nematodes and lower fecundity of the worms.

The subchronic effect of cadmium on selected immunological parameters was studied in guinea pigs with experimental ascariasis. Cadmium chloride given orally for 28 days caused a considerable suppression of T- and B- cells in the lymphoid organs of intoxicated animals, of the metabolic activity of their peritoneal macrophages and a moderate decline in the level of complement CH50 and AH50 from day 1 to day 28 of the experiment, in comparison with the initial value. After a subsequent infection of the subchronically intoxicated guinea pigs the values for both the cell populations and the macrophage metabolic activity remained considerably suppressed, compared with infected control animals. The phagocytic and metabolic activity of macrophages as well as the CH50 and AH50 level, however, increased conspicuously for a short time after application of heavy metal and after infection but it did not reach the level of the infected group. The level of specific circulating antibodies was not affected by intoxication. Compared with the controls, the mean intensity of infection with Ascaris larvae migrating in the lungs of intoxicated animals increased by 20%. The results have established the negative effect of cadmium on the immunological parameters of the cellular immunity and humoral immunity studied and the impairment of the organism's response to the antigenic stimulus after an A. suum infection.

A rapid and reliable method based on immuno-affinity chromatography and preparative high pressure liquid chromatography was used for extraction and purification of cAMP from the two trematode species Gastrothylax crumenifer and Explanatum explanatum. The purified cAMP was quantified by electrospray tandem mass spectrometry in an amount of 44 and 83 picomole/g fresh weight of Gastrothylax crumenifer and Explanatum explanatum respectively.

Different types of proteoglycans (PGs) from adult worms of Schistosoma haematobium, were sequentially extracted using chaotropic agents under associative conditions (0.5 M GnCl), dissociative conditions (4 M GnCl) and detergents (Triton X-100 and SDS). The extracts were designated Fl, F2, F3 and F4, respectively. The highest amount of uronic acid and carbohydrate was detected in the associative extract (Fl) while the highest amount of protein was detected in the SDS extract (F4). Agarose polyacrylamide gel electrophoresis (A-PAGE) indicated the presence of a different PG in each extract with different electrophoretic mobilities. Agarose gel electrophoresis of glycosaminoglycan (GAG) separated from GnCl, associative and dissociative extracts, and the residue suggested the presence of dermatan sulphate in the two extracts and the residue, in addition to a GAG-like material found in the associative extract only. This glycosaminoglycan showed resistance to digestion with all mucopolysaccharidases and nitrous acid treatment. Gel filtration chromatography of associative extract on Sepharose CL-6B indicated the presence of three main uronic acid peaks (P1, P2 and P3). Chondroitin sulphate was the main GAG that could be detected in peak one (P1). Peak two (P2) contains carbohydrate and uronic acid but has no protein or absorbance at 280 nm. P2 has two types of GAGs: dermatan sulphate and a GAG-like material. The role of this PG in helping the adult schistosomes in evading immobilization by the host blood clotting cascade is discussed. Antibodies to peak one and peak two were detected in hamster sera infected with S. haematobium and S. mansoni using the ELISA test. The specificity of peak two was found to be evident in its low cross-reactivity (18.9%) when confronted with S. mansoni infected sera.

Field investigations were carried out over a 4-year period in three farms of the Haute-Vienne department (France) in order to determine the prevalence of Fasciola hepatica infection in the annual generations of Lymnaea truncatula. Infection rates found in March were significantly lower than those recorded in July or in September (0.8% to 2.2% compared to 5.7% to 13.5% and 4.4% to 9.3%, respectively). They were always lower in overwintering snails than in other snail generations (summer generation in 1989,1990 and 1991; spring and summer generations in 1992). Experimental infections of L. truncatula by F. hepatica were performed to evaluate the characteristics of Fasciola infection with reference to snail generation and snail activity. Survival of summer generation snails at day 30 postexposure was significantly lower in snails collected in September than in those collected in May and June. In the winter generation of L. truncatula, snail survival was significantly higher in snails collected from December to March than in those from November. The prevalence of infection was significantly lower in snails collected in September (summer generation) than in those collected from December to March (winter generation). The duration of the prepatent period was significantly delayed in snails collected from January to March (a mean of 54.2 to 58.2 days instead of 43.1 to 49 days in the other groups), whereas that of the patent period was significantly shorter (5 to 9.3 days instead of 18.3 to 40.3 days, respectively). In snails collected from January to March, the number of metacercariae was significantly lower than that found from other snail groups (a mean of 21.5 to 42 metacercariae instead of 72.8 to 151.4 cysts, respectively). Fasciola infections of L. truncatula originating from spring and summer generations were more efficient than those from the winter generation of snails.

This study compares the metacercariae of a ‘pygmaeus’ microphallid discovered in Littorina saxatilis from the coast of Northern Ireland with the metacercariae of Microphallus piriformes and M. pygmaeus from the same species of gastropod mollusc from Arctic Russia. Light and scanning electron microscopy were used to provide morphometric and surface details for descriptions of the organisms concerned. Comparison and statistical analysis of the results established that the species from Northern Ireland was M. piriformes and not M. pygmaeus as had previously been assumed. It dearly indicates the need for critical assessment of the accuracy of literature dealing with the occurrence of ‘M. pygmaeus’ in both intermediate and final hosts.

Studies on human and murine isolates of Schistosoma mansoni, from Richard-Toll, Senegal, were carried out by isoelectric focusing in polyacrylamide gels. Seven enzyme systems; lactate dehydrogenase (LDH), malate dehydrogenase (MDH), glucose-6-phosphate dehydrogenase (G6PD), acid phosphatase (AcP), hexokinase (HK), glucose phosphate isomerase (GPI), and phosphoglucomutase (PGM), were used to compare the two isolates. All systems tested, apart from LDH, were found to be polymorphic for both isolates. Interestingly, one phenotype is more frequent than the remainder. The results show that there is no significant genetic variation between the S. mansoni isolates from man and the rodents, Arvicanthis niloticus and Mastomys huberti.