When cercariae of Schistosoma mansoni and of S. japonicum were irradiated with various levels of u.v. light at 254 nm, their development to perfusable worms was reduced to below 1% at about 200 μW min cm−2. Cercariae attenuated with about 300 μW min cm−2 induced partial resistance against an homologous challenge infection in mice. No differences were observed between the two schistosome species when the same treatment was given to the cercariae. Thus the same u.v. dose can confer immunizing ability to cercariae of both S. mansoni and S. japonicum.

Among flatworms with parasitic and commensal modes of existence, parthenogenesis and asexual multiplication appear to be largely confined to the Digenea and Cestoda, the only parasitic platyhelminths that routinely utilize indirect life-cycles. Parthenogenesis is apparently restricted to a minority of adult digeneans and cestodes inhabiting their final hosts, and a survey is made of the particular modes of parthenogenesis (i.e. apomictic, automictic and generative) which are employed by such adults. Asexual (amictic) multiplication, in the form of fissioning, is demonstrated by young adults of the cyclophyllidean cestode, Mesoces-toides corti, but is otherwise not exhibited by adult cestodes or digeneans, other than in the perplexing phenomenon of proglottid formation in polyzoic tapeworms. Secondary multiplication is of ubiquitous occurrence in digenean life-cycles in the form of the proliferation which takes place within sporocysts and rediae (germinal sacs) located in the first intermediate host. The controversy concerning the nature of this multiplication is reconsidered in the context of recent findings which have centred on cellular aspects. On the basis of present evidence germinal sac multiplication should be regarded as an asexual rather than a parthen-ogenetic process. The cestode asexual multiplication which occurs in intermediate hosts is a function of the metacestode stage of development. Metacestode proliferation is only known from about 20 species and 6 families of polyzoic cestodes with approximately half the described instances occurring in the family Taeniidae. The organization of these proliferative metacestodes, findings concerning their totipotent stem cells and the ontogeny of buds and new scolices are all reviewed. Finally, the capacity for population expansion of multiplicative larval digeneans and metacestodes are compared, while the ecological roles and the genetical consequences of both parthenogenesis and amictic multiplication in the two taxa are also examined.

The maintenance of Theileria parva parva infection in an endemic area of Kenya on the shore of Lake Victoria was studied in the field and laboratory. High prevalences of antibodies against T. parva and T. mutans and intra-erythrocytic piroplasms were detected in local zebu (Bos indicus) cattle. The mean infection rate of Theileria parasites in the tick, Rhipicephalus appendiculatus, in field collections was 1·1 %. Most of the infection was attributed to T. parva parva by application of field ticks to susceptible cattle. Five cattle, all about 1·5 years old, were purchased from local owners and transported to the laboratory. All five had oscillating antibody titres against T. parva and T. mutans and had patent theilerial infections during the subsequent 13 months. Uninfected R. appendiculatus nymphs were applied to cattle at 0, 3, 6, 9 and 13 months after transport to Muguga, and 18 out of 23 batches transmitted T. parva parva infection to cattle when 100 resultant R. appendiculatus adults were applied. Infection rates in the tick batches were usually low, with 1 salivary gland acinus infected/tick. Hence, a frequent carrier state of naturally infected cattle has been demonstrated for T. parva parva for the first time, and it is likely that this carrier state is of great importance in maintenance of T. parva parva infection in the field.

1. Cerfontaine's (1896) description of the egg is confirmed. The eggs are not retained on the gills during development.

2. Maturation of the oocyte takes place after egg formation. The haploid number of chromosomes is 9.

3. The onset of embryonic development is related to the time of egg formation or sperm entry. Cleavage is total and slightly unequal, leading to the formation of a morula in which there are no germ layers. The larval gut is formed by epiboly round a mass of yolk which becomes incorporated in mid-body. Larval organs and a partially ciliated epithelium are differentiated in situ.

4. During embryonic development yolk is broken down and absorbed, some being incorporated in the body.

5. Hatching does not seem to result from any special stimulus. Mechanical pressure by the larva forces off the operculum, but secretions may weaken the suture.

6. The free-swimming larva is gyrodactyloid with a winged haptor bearing four pairs of lateral, one pair of postero-lateral and one pair of median hooks. Four pairs of flame cells are present and one pair of longitudinal, lateral, excretory ducts, which open antero-laterally. The larva swims by ciliary action and does not respond to jarring, light and shade stimuli, or, when vigorous, to the presence of the excised gill of the host. Tired larvae are doubtfully attracted by host gill tissue. Larval haptorial type is thought to be determined phylogenetically rather than as a result of adaptation to the type of host tissue to which the larva attaches itself.

7. The larva attaches itself to the host's gill and sloughs off the ciliated coat. Growth follows with the development of the adult clamps in pairs, starting posteriorly, each pair replacing a pair of lateral, larval hooks. Primordia of the reproductive organs are laid down in the larval stage, but are only finally elaborated when the adult form has been attained. Maturity is not reached at a definite size and the ovary and testes mature simultaneously.

8. Feeding is at least partly on the host's blood.

9. The longest time which may elapse between formation and laying of an egg is about 5 hr. The average time taken for embryonic development is 18·3 days at 14·25° C., but temperature affects the developmental rate. Ciliated larvae survive about 24 hr. in the absence of a host. The second larval stage is reached between 5 and 13 days after hatching, the third larval stage after more than 38 days. The immature stage is thought to be reached within 3 months and the adult stage within 6 months.

10. Reproduction occurs throughout the year. The animal is functionally hermaphrodite at all times once maturity is reached.

11. A certain degree of osmo-regulation is possible in adults, but this does not extend to ciliated larvae.

12. Adults rest along a gill filament on its inner face and do not move about. Larvae are more ready to move.

13. The average number of flukes per host is 2·24. The 1st and 2nd pairs of gills carry three times as many flukes as the 3rd and 4th pairs.

14. The host suffers no apparent harm from the presence of the flukes.

15. Premunition of Gadus virens against Diclidophora denticulata does not occur. Age resistance is probably developed to the extent that larvae cannot establish themselves on older fish and is probably due to mechanical difficulties and changed habits of the host. The ability of this fluke to parasitize species of Gadus does not extend to G. callarias.

16. D. denticulata is recorded for the first time from St Andrews Bay and the Firth of Forth.

Susceptibility to oxygen and properties relative to oxygen metabolism were compared in metronidazole-resistant and susceptible strains of Trichomonas vaginalis. The study involved clinical isolates displaying the aerobic type of resistance, as well as resistant strains developed in vitro, both with aerobic (MR-3) and anaerobic (MR-5, MR-100) resistance. Elevated sensitivity to oxygen of the resistant clinical isolates was observed. Progressive increase of susceptibility to oxygen also accompanied in vitro development of resistance. No correlation was found between the activity of NADH oxidase and aerobic resistance, while the in vitro derivative with fully developed anaerobic resistance (MR-100) showed about 50% decrease of NADH oxidase activity. The superoxide dismutase (SOD) activity was elevated in both resistant clinical isolates and in in vitro-developed resistant strains. The changes in levels of ferredoxin were insufficient to support ferredoxin deficiency as a cause of aerobic metronidazole resistance. Western blot analysis and electron paramagnetic resonance spectroscopy of purified hydrogenosomes showed that ferredoxin is expressed in aerobically resistant strains and has intact iron-sulfur clusters. Down-regulation of ferredoxin was demonstrated only in the late phase of development of the anaerobic resistance (MR-100). The results support a link between aerobic resistance and defective oxygen scavenging. The increased levels of intracellular oxygen, beneficial to resistant parasites when they interact with the drug, may have adverse effects on their fitness as shown by their increased sensitivity to oxidative stress.

The surface morphology of schistosomula extracted from the skin, lungs and hepatic portal system (hps) of mice was investigated from Days 0 to 18 post-infection. Skin schistosomula and newly arrived schistosomula from the hps were of similar dimensions but were morphologically distinct. Lung schistosomula were considerably elongated with an estimated 53% increase in surface area compared to skin schistosomula. The pitted tegument of lung schistosomula was formed into ridges and troughs. These were compressed together in contracted individuals recovered from the hps on Day 10. The annular ridges were cross-linked by longitudinal septae which possibly prevent further elongation of the body. A regression of the spines between the mouth and the ventral sucker was observed in Day 2 skin schistosomula. In lung schistosomula only the spines at the anterior and posterior of the body remained. New spines were formed after the schistosomula reached the hps. It is suggested that the spines in the mid-region of the body are selectively disassembled and that their loss facilitates migration along the lumina of capillaries with the residual spines acting as anterior and posterior anchors. The mouth opening was enlarged in schistosomula from the hps recovered from Day 10 onwards. Skin schistosomula lost the cercarial apical tegumentary ridges between 24 and 48 h after penetration but a spineless protrusible area remained. After arrival in the hps this area became integrated into the anterior surface as the oral sucker developed around the sub-terminal mouth. The cercarial ciliated papillae were lost on penetration. The migrating schistosomulum had few visible sensory papillae but following arrival in the hps new papillae were observed.

New ways of integrating and scaling up control of neglected tropical diseases (including schistosomiasis) are presently underway. In this context consideration of social science perspectives is essential. In this article, we review social science publications of relevance to sustained control of schistosomiasis in Africa including diagnosis and screening, treatment, supply of clean water and improved sanitation, as well as health communication. Studies of community involvement and links between schistosomiasis control programmes and broader health care systems are also explored. Directions for future social science of relevance to sustainable schistosomiasis control are outlined, including ways of ensuring equitable access to health services as well as involvement of endemic communities and local health care systems based on equal partnership.

Echinococcosis is a re-emerging zoonotic disease in Kyrgyzstan, and the incidence of human infection has increased substantially since the collapse of the Soviet Union in 1991. Domestic dogs are hosts of Echinococcus spp. and play an important role in the transmission of these parasites. The demography, ecology and behaviour of dogs are therefore relevant in studying Echinococcus spp. transmission. Dog demographics, roles of dogs, dog movements and faecal environmental contamination were assessed in four rural communities in the Alay Valley, southern Kyrgyzstan. Arecoline purge data revealed for the first time that E. granulosus, E. canadensis and E. multilocularis were present in domestic dogs in the Alay Valley. Surveys revealed that many households had dogs and that dogs played various roles in the communities, as pets, guard dogs or sheep dogs. Almost all dogs were free to roam, and GPS data revealed that many moved outside their communities, thus being able to scavenge offal and consume rodents. Faecal environmental contamination was high, presenting a significant infection risk to the local communities.

The chemical and physical nature of monogenean attachment sclerites has been investigated by chromatography, histochemistry, solubility studies and X-ray diffraction, and these sclerites have been shown to be scleroproteinaceous and not, as the bulk of the literature suggests, chitinous in composition.

Hooks sclerites (i.e. marginal hooks and hamuli), which are the most primitive type of monogenean attachment sclerites and arise early on ontogeny, have been shown to be keratinous; clamp sclerites, accessory bars and the spines arming the pseudohaptors and squamodisks of certain genera which appear to have been acquired later in the phylogeny of the group to supplement the efficiency of the haptoral hooks, contain no cystine sulphur.

While the chemical nature of the non-cystine-containing skeletal structures has not been fully elucidated, clamp substance was found to differ from that of the other scleroproteins with which it was compared, namely sclerotin, vertebrate elastin, reticulin, collagen and keratin. Clamp substance does not appear to be quinonetanned; acid proteins maybe important in the stabilization of this scleroprotein.

Evidence for the occurrence of a variety of S–S bearing scleroproteins throughout the invertebrates has been collated and the problems involved in adequately defining a keratin have been discussed. The implications of the apparent affinity of monogenean hook protein to vertebrate keratins, which in general are intracellular and epidermal derivatives have been considered and some speculations have been made about the possible differences in the development of hook and clamp structures.

Contrary to the prevalent opinion that monogenean sclerites are ‘cuticularizations’, evidence has been presented that these structures are in fact deeply seated and unlikely to be derivations of a superficial cuticle.

The chemical differences elucidated between the median and lateral sclerites of the chimaericolid adhesive organ have encouraged speculation on the evolution of the different types of attachment organ throughout the polyopisthocotylineans.

Outside the Monogenea, studies on the sulphur content of digenean spines and stylets and on the larval hooklets of the ‘cestodarians’ Gyrocotyle, Amphilina and Archigetes, and of eucestodes, have helped to substantiate the view that the cestodes and monogeneans are more closely related to each other than either of these groups is related to the digeneans.

I wish to thank the Director and staff of the Plymouth Laboratory and in particular Mr J. E. Green, for invaluable assistance. I am also indebted to Dr R. W. H. Small for his guidance on X-ray diffraction technique, to Dr J. Morris of the M.R.C. Skin Unit for his advice on the chromatography and to Dr J. Llewellyn for his interest and helpful criticism throughout.

Through the courtesy of Dr Hans Gadow I have had the opportunity of examining a number of skins of five species of Apteryx in the collection of the Cambridge University Museum. From these I have collected at least three species of Mallophaga, which I find to belong to the genus Rallicola. These are described below, with some discussion of the genus to which they belong, and of the significance of the occurrence of that genus upon Apteryx, from which no Mallophaga have previously been recorded.

A comparison was made between the early events (a sexual stages) in the life-cycle of Eimeria tenella in specifically immunized and control chickens. Particular attention was paid to the quantitative aspects and to the transport of sporozoites within intra-epithelial lymphocytes (IEL) from the enterocytes of the surface epithelium to the enterocytes of the crypts. There was a moderate decrease in the number of parasites initially seen in the mucosa of the immune birds, suggesting that some of the effects of immunity are exerted before penetration of the surface enterocytes, but the reduction in the numbers of developing parasites was more marked. This latter effect was due, at least partly, to failure of transfer of sporozoites from IELs to crypt enterocytes. These findings are discussed in relation to the efficacy of the immunity induced.

In total 1502 faecal samples were collected from a population of European badgers (Meles meles) between 1992 and 1995 at Wytham Woods, Oxfordshire, UK. Two coccidia species, Eimeria melis and Isospora melis, were identified. Cubs showed a marked seasonal pattern of infection with E. melis, with infection occurring at significantly higher intensity and prevalence than in adults. There was preliminary evidence to suggest that infantile coccidiosis in badgers may be associated with impaired growth and increased mortality.

Fourteen 9-month-old zebu calves were immunized with 10000 irradiated Schistosoma bovis schistosomula given in 1–3 intramuscular or subcutaneous doses, and 4 more calves were immunized with 10000 irradiated cercariae administered percutaneously in a single dose. Eight weeks after the beginning of the experiment these calves, together with four non-immunized controls were challenged percutaneously with 10000 normal S. bovis cercariae/calf. Comparative clinical, parasitological, pathological and pathophysiological observations subsequently revealed significant differences between the vaccinated and non-vaccinated calves. The vaccinated calves showed significantly higher growth rates, and a superior body composition as indicated by their lower total body water content. The beneficial effects of vaccination were also shown by significantly lower faecal egg outputs in the vaccinated calves and by their lower tissue egg and adult worm counts. The reduced tissue egg counts were also reflected in the milder histopathological changes seen in the vaccinated calves. The vaccinated calves had significantly higher packed cell and circulating red blood cell volumes than the challenged controls, longer red blood cell half lives, and somewhat lower blood volumes and rates of red blood cell synthesis. No untoward clinical effects that could be attributed to vaccination were recorded. These results indicate that zebu cattle can be effectively protected against S. bovis by vaccination with irradiated organisms. We are now evaluating this type of vaccine in a field trial in an enzootic area in the Sudan.

The species Echinococcus granulosus is made up of several genotypic strain groups, whose taxonomical classification is still undetermined. Genotypes in the cervid-wolf life-cycle are poorly known, especially in Europe. In this study, 33 Echinococcus isolates from cervids from Finland and Sweden were characterized using mitochondrial ND1 gene sequencing. In addition, phylogenetic analysis of E. granulosus strains using the mitochondrial ATP6, ND1, ND3 and CO1 genes was performed using maximum likelihood, neighbour-joining and maximum parsimony methods. The Finnish and Swedish cervid isolates were found to represent the genotype G10. In the phylogenetic analyses, the camel (G6), pig (G7), cervid (G8) and Fennoscandian cervid (G10) strains clustered in a well-supported monophyletic group. This group differed clearly from the common sheep (G1) and horse (G4, ‘E. equinus’) strains, but was closely related to the cattle strain (G5, ‘E. ortleppi’). Our results support the previous studies suggesting that the genotypes G6-10 should be separated from the species E. granulosus sensu stricto. However, additional morphological studies are needed, and the relationship to the cattle strain (‘E. ortleppi’) should be thoroughly evaluated before a final decision of the taxonomical status of the G6-10 group can be made.

Intermittent preventive treatment of infants (IPTi) with sulphadoxine pyrimethamine (SP) is recommended as an additional malaria control intervention in high transmission areas of sub-Saharan Africa, provided its protective efficacy is not compromised by SP resistance. A significant obstacle in implementing SP-IPTi, is in establishing the degree of resistance in an area. Since SP monotherapy is discontinued, no contemporary measures of in vivo efficacy can be made, so the World Health Organisation has recommended a cut-off based upon molecular markers, stating that SP-IPTi should not be implemented when the prevalence of the dhps 540E mutation among infections exceeds 50%. We created a geo-referenced database of SP resistance markers in Africa from published literature. By selecting surveys of malaria infected blood samples conducted since 2004 we have mapped the contemporary prevalence of dhps 540E. Additional maps are freely available in interactive form at http://www.drugresistancemaps.org/ipti/. Eight countries in East Africa are classified as unsuitable for SP-IPTi when data are considered at a national level. Fourteen countries in Central and West Africa were classified as suitable while seven countries had no available contemporary data to guide policy. There are clear deficiencies in molecular surveillance data coverage. We discuss requirements for ongoing surveillance of SP resistance markers in support of the use of SP-IPTi.

Reports of Calicophoron daubneyi infecting livestock in Europe have increased substantially over the past decade; however, there has not been an estimate of its farm level prevalence and associated risk factors in the UK. Here, the prevalence of C. daubneyi across 100 participating Welsh farms was recorded, with climate, environmental and management factors attained for each farm and used to create logistic regression models explaining its prevalence. Sixty-one per cent of farms studied were positive for C. daubneyi, with herd-level prevalence for cattle (59%) significantly higher compared with flock-level prevalence for sheep (42%, P = 0·029). Co-infection between C. daubneyi and Fasciola hepatica was observed on 46% of farms; however, a significant negative correlation was recorded in the intensity of infection between each parasite within cattle herds (rho = −0·358, P = 0·007). Final models showed sunshine hours, herd size, treatment regularity against F. hepatica, the presence of streams and bog habitats, and Ollerenshaw index values as significant positive predictors for C. daubneyi (P < 0·05). The results raise intriguing questions regarding C. daubneyi epidemiology, potential competition with F. hepatica and the role of climate change in C. daubneyi establishment and its future within the UK.

Experiments were carried out to investigate the effects of Ascaris suum infection on the growth, food intake, nitrogen and fat utilization and intestinal function of young pigs receiving diets low in protein. An infection procedure was developed which provided relatively uniform and heavy infections in pigs under study. Ascaris-infected pigs showed statistically significant reduction in growth rate and food intake compared to uninfected controls. The reduction in growth rate was observed after the A. suum were mature and eggs were observed in the faeces of pigs. The degree of growth retardation was significantly correlated with worm burden. Infected pigs showed no consistent reduction in nitrogen and total solids digestibility compared to controls but fat digestion was reduced. The infected pigs showed reduced nitrogen retention compared to uninfected controls. Ascaris-infected pigs had heavier intestinal tracts with increased size of the tunica muscularis. Lactase activity in mucosa from infected pigs was significantly lower than in controls, whereas no consistent effect was observed in mucosal sucrase and maltase activity. When Ascaris-infected pigs were given an oral lactose load, blood glucose levels rose less than in control pigs, suggesting that the infection resulted in impaired lactose tolerance.

To clarify the taxonomy of trichomonads associated with human respiratory diseases, we examined a collection of axenic trichomonad strains isolated from the oral cavity and bronchi of patients from pulmonary diseases clinics in Tallin, Estonia. The oral and bronchial strains were compared mutually as well as with a reference strain of Trichomonas tenax, a common inhabitant of the human oral cavity, and other trichomonad species from humans and animals. Unexpectedly, the morphological studies, as well as DNA sequencing of ITS1-5.8S rRNA-ITS2 regions revealed that the Estonian strains belong to the genus Tetratrichomonas, with a high similarity to the avian species Tetratrichomonas gallinarum. None of the strains belonged to Trichomonas tenax. DNA fingerprinting using the RAPD method separated Estonian strains into 2 distinct groups: ‘bronchial’ consisting of 5 and 2 strains isolated from bronchi and ‘oral’ cavity, respectively, and oral consisting of 3 oral strains. Consistent differences between ‘bronchial’ and ‘oral’ groups were confirmed by analysis of ITS1-5.8S rRNA-ITS2 sequences. Our results have revealed novel trichomonad species of the human oral cavity and bronchi.

A population of three-spined sticklebacks, Gasterosteus aculealus, from a pond in Somerset was sampled about every three weeks for 19 months, a total of 1863 fish being collected. Three species of parasites were found in the fish: Schistocephalus solidus, Diplostomum gasterostei and Echinorhynchus clavula.

Seasonal changes in the incidence and intensity of the three parasitic infections are described. In general the infections increased in summer and autumn and decreased in winter and spring, although in Schistocephalus the differences in the level of infection between the two years were greater than between seasons.

The largest increases in the Schistocephalus and Echinorhynchus infections occurred in August and September and in the Diplostomum infection in May and June. These increases could be related to the feeding activity of the sticklebacks and to the abundance and level of infection of the Cyclops, Asellus and Limnaea pereger populations.

Reduction in the sizes of the infections was by predation and death of heavily infected fish in the case of Schistocephalus and Diplostomum and mainly by death of individual worms in Echinorhynchus.

These mechanisms are shown to be adapted to the life cycles of the parasites.

I am most grateful to Dr H. D. Crofton for his help and encouragement during this investigation and to Dr R. A. Avery for useful discussions and advice. This work was supported by a Science Research Council research studentship and a NATO studentship.

The Iberian lynx (Lynx pardinus) is the most endangered felid in the world. Only about 160 individuals remain in 2 separate metapopulations in Southern Spain (Sierra Morena and Doñana). We obtained blood samples of 20 lynxes captured from 2004 to 2006, and determined the prevalence of infection and genetic diversity of Cytauxzoon spp. using 18S rRNA PCR and sequence analysis. Prevalence of infection was 15% (3 of 20). Cytauxzoon sp. was only detected in Sierra Morena. For phylogenetic analysis, we used the sequences reported in the present study and those characterized in different domestic and wild felids and ticks from North and South America, Asia and Europe. Three different Cytauxzoon sp. sequences were obtained. They were closely related to that obtained from a Spanish cat, but diverged in up to 1·0% with respect to the only previously reported sequence from an Iberian lynx. Conversely, the latter sequence clustered together with C. manul sequences obtained from Pallas cats (Otocolobus manul) in Mongolia. Our analysis yields a separate cluster of C. felis sequences from cats, wild felids and ticks in the United States and Brazil. These results suggest that at least 2 different Cytauxzoon spp. may be present in Iberian lynx. The apparent absence in one of the areas, together with the possibility of fatal cytauxzoonosis in lynxes makes necessary disease risks to be taken into account in management conservation strategies, such as translocations and re-introductions.