In this study, the advantage of the use of chloroquine (CQ) containing liposomes (lipCQ) over free CQ in the chemotherapy of murine malaria (Plasmodium berghei) was demonstrated. The maximum permissible dose per intraperitoneal injection was 0·8 and 10 mg for CQ and lipCQ, respectively. An increase in therapeutic and prophylactic efficacy of lipCQ in comparison with free CQ at a 0·8 mg CQ dose level was found. It was possible to obtain 100% efficacy (injection at day 5 after infection; parasitaemia 4–8%) with one single intraperitoneal injection of 6 mg lipCQ. Moreover, the ability to increase the doses of CQ per injection after liposome encapsulation allowed successful treatment of infections with CQ-resistant Plasmodium berghei which could not be cured by a 7-day course with the maximum tolerable dose of free CQ of 0·8 mg/mouse/day.

The life cycle and pathogenicity are described of a pure strain of Eimeria isolated from turkey poults in Great Britain and identified as E. meleagrimitis.

There were three schizogony cycles followed by a sexual generation.

The coccidium produced a high mortality and loss of weight in young poults.

An age resistance developed by the time the poults were 8–10 weeks of age.

The pathology of the infection is described.

The ultrastrcuture and development of the protozoan Histomonas meleagridis in the reproductive system of the female nematode, Heterakis gallinarum, have been described. It has been shown that there is a distinct cycle of events in the reproductive system. The stage of Histomonas in the germinal zone of the ovary is extracellular; the protozoan feeds and multiplies here. The histomonads move down the ovary with the oogonia and become intracellular when they penetrate the developing oocytes in the growth zone of the ovary. This is apparently an active penetration of the oocyte by the parasite. Feeding and division of the histomonad occurs in the oocyte and also in the newly formed egg; apparently a gradual reduction in size occurs along the reproductive system. These stages in the parasite are similar to the tissue-inhabiting stages in the bird but are much smaller. There are no mitochondria present.

There is strong circumstantial evidence that the nematode is able to repair damage to the wall of the reproductive system and to the oolemma caused by the protozoan.

I wish to thank Dr E. E. Lund of Beltsville Parasitological Laboratory, Maryland, U.S.A., who very kindly sent me some of his Histomonas-free strain of Heterakis and Dr L. P. Joyner and Mr C. C. Norton of the Central Veterinary Laboratory, Weybridge, for the strain of Heterakis which was found to transmit Histomonas wenrichii. I also wish to thank Mrs B. Fisher, Mr B. Millard and Mr M. Shirley for technical assistance and Mr P. Rogers for assistance with the photography.

Leishmania protozoa are obligate intracellular parasites that reside in the phagolysosome of host macrophages and cause a large spectrum of pathologies to humans known as leishmaniases. The outcome of the disease is highly dependent on the parasite species and on its ascribed virulence factors and the immune status of the host. Characterization of the genome composition of non-pathogenic species could ultimately open new horizons in Leishmania developmental biology and also the disease monitoring. Here, we provide evidence that the lizard non-pathogenic to humans Leishmania tarentolae species expresses an Amastin-like gene, cysteine protease B (CPB), lipophosphoglycan LPG3 and the leishmanolysin GP63, genes well-known for their potential role in the parasite virulence. These genes were expressed at levels comparable to those in L. major and L. infantum both at the level of mRNA and protein. Alignment of the L. tarentolae proteins with their counterparts in the pathogenic species demonstrated that the degree of similarity varied from 59% and 60% for Amastin, 89% for LPG3 and 71% and 68% for CPB, in L. major and L. infantum, respectively. Interestingly, the A2 gene, expressed specifically by the L. donovani complex which promotes visceralization, was absent in L. tarentolae. These findings suggest that the lack of pathogenicity in L. tarentolae is not associated with known virulence genes such as LPG3, CPB, GP63 and Amastin, and that other factors either unique to L. tarentolae or missing from this species may be responsible for the non-pathogenic potential of this lizard parasite.

Larvae of Hymenolepis diminuta develop in the haemocoele of the beetles Tribolium and Tenebrio, and of the locust Schistocerca gregaria, without being encapsulated by haemocytes. The mechanism of this evasion of the haemocytic defence reaction has been examined using various techniques. Larvae grown in culture and injected into S. gregaria have few or no haemocytes adherent even after 8 h, although latex beads injected at the same time have been thickly encapsulated. This, and results of transplanting cysticercoids and host tissue between different insect species, suggests that the surface of the larvae may bear an inherent similarity to the surface of host tissues and thus escape recognition as ‘not-self’ by the host’s haemocytes.

The prevalence of vector-borne parasites varies greatly across host species, and this heterogeneity has been used to relate infectious disease susceptibility to host species traits. However, a few empirical studies have directly associated vector-borne parasite prevalence with exposure to vectors across hosts. Here, we use DNA sequencing of blood meals to estimate utilization of different avian host species by Culex mosquitoes, and relate utilization by these malaria vectors to avian Plasmodium prevalence. We found that avian host species that are highly utilized as hosts by avian malaria vectors are significantly more likely to have Plasmodium infections. However, the effect was not consistent among individual Plasmodium taxa. Exposure to vector bites may therefore influence the relative number of all avian Plasmodium infections among host species, while other processes, such as parasite competition and host-parasite coevolution, delimit the host distributions of individual Plasmodium species. We demonstrate that links between avian malaria susceptibility and host traits can be conditioned by patterns of exposure to vectors. Linking vector utilization rates to host traits may be a key area of future research to understand mechanisms that produce variation in the prevalence of vector-borne pathogens among host species.

The monogenean ectoparasite, Gyrodactylus salaris Malmberg, 1957, has had a devastating effect on wild Atlantic salmon (Salmo salar) since its introduction to Norway in the mid-1970s. In Lake Pålsbufjorden, southern Norway, upstream of the stretches of the River Numedalslågen with anadromous Atlantic salmon, a resident Arctic charr (Salvelinus alpinus) population has been reported to be infected with G. salaris which is viable in the absence of its normal host, the Atlantic salmon. Currently, there is no record of G. salaris infecting Atlantic salmon in the downstream sections of the River Numedalslågen. We studied experimentally the infectivity and reproductive capacity of G. salaris from Lake Pålsbufjorden on wild and hatchery-reared Atlantic salmon as well as on Arctic charr and rainbow trout (Oncorhynchus mykiss). Arctic charr and rainbow trout were moderately susceptible, whereas the Atlantic salmon stocks from River Numedalslågen and River Drammenselva were innately resistant to only slightly susceptible. Thus, the G. salaris from Arctic charr in Lake Pålsbufjorden is considered non-pathogenic to Atlantic salmon. This is the first observation of variation in host preference among Norwegian G. salaris populations. The observed differences in virulence between G. salaris populations could have important consequences for the international legislation and management of Atlantic salmon.

The number of facilities in which customers make contact with cats before eating and drinking, called ‘cat cafés’, has recently increased in Tokyo, Japan. In a survey to clarify the possibility of zoonotic transmission in Giardia duodenalis, the infection rates of G. duodenalis in 321 stool samples of cats from 16 cat cafés, 31 pet shops, and the Animal Care and Consultation Center of Tokyo were 19·1% (22/115), 1·2% (1/85), and 2·5% (3/121), respectively. In the molecular analysis of 26 G. duodenalis isolates, 6 samples from 2 cat cafés belonged to the zoonotic genotype assemblage A I, and 20 other samples were of assemblage F. Moreover, phylogenetic analysis of glutamate dehydrogenase (GDH) and triosephosphate isomerase (TPI) genes of the 20 assemblage F isolates revealed 2 major lineages. The 6 assemblage A isolates belonged to the same cluster with regard to the GDH gene; however, 2 of the 6 isolates belonged to a different cluster from the other 4 isolates with regard to the TPI gene. Therefore, a risk of transmission from cats to humans is suggested because of the detection of zoonotic Giardia genotypes in cat cafés.

To comprehend natural host–parasite systems, ecological knowledge of both hosts and parasites is critical. Here I present a view of marine systems based on the snail Ilyanassa obsoleta and its trematodes. This system is reviewed and two others, those of the snails Cerithidea californica and Littorina littorea, are then summarized and compared. Trematodes can profoundly affect the physiology, behaviour and spatial distribution of hosts. Studying these systems is challenging because trematodes are often embedded in host populations in unappreciated ways. Trematode prevalence is variable, but can be high in populations of all three hosts. Conditions under which single- and multiple-species infections can accumulate are considered. Adaptive relations between species are likely the most important and potentials for adaptation of parasites to hosts, hosts to parasites, and parasites to other parasites are also considered. Even if colonization rate is low, a snail population can develop high trematode prevalence, if infections persist long and the host is long-lived and abundant. Trematodes must be adapted to use their snail hosts. However, both I. obsoleta and L. littorea possess highly dispersed planktonic larvae and trematode prevalence is variable among snail populations. Host adaptation to specific infections, or even to trematodes in general, is unlikely because routine exposure to trematodes is improbable. Crawl-away juveniles of C. californica make adaptation to trematodes in that system a possibility. Trematode species in all three systems are not likely adapted to each other. Multiple-species infections are rare and definitive hosts scatter parasite eggs among snail populations with variable prevalences. Routine co-occurrence of trematodes in snails is thus unlikely. Adaptations of these larval trematodes to inhabit the snail host must, then, be the basis for what happens when they do co-occur.

Head lice prevalence varies greatly between and within countries, and more knowledge is needed to approach causes of this variation. In the present study, we investigated head lice prevalence among elementary school students and their households in relation to individual and household characteristics as well as spatial variables. The investigation included households from 5 geographically separated municipalities. Present infestations among household members as well as previous infestations in the household were reported in a questionnaire. In elementary school students prevalence was low (1·63%), but more than one-third of the households (36·43%) had previously experienced pediculosis. Prevalence was higher in elementary school students than in other household members, and highest in third-grade children. Prevalence was also influenced by the school attended, which suggested that interactions between children in the same school are important for head lice transmission. Previous occurrence of head lice in homes also increased the risk of present infestation. Prevalence of previous infestations was higher in households with more children and in more densely populated municipalities, indicating that the density of hosts or groups of hosts influences transmission rates. These results demonstrate that information of hosts’ spatial distribution as well as household and individual characteristics is needed to better understand head lice population dynamics.

The hatching of Hymenolepis diminuta eggs and penetration of the emergent hexacanths in adult and larval Tenebrio molitor beetles had been described. Hatching was shown to be a two-stage process involving rupture of the eggshell by the insect's mandibles and digestion of the remaining egg-layers in the midgut lumen. Penetration of hatched embryos was examined by histological methods that demonstrated the rate of migration and the route taken by hexacanths entering the haemocoel of adult beetles. Differences in the arrangement of the midgut tissues in adult and larval T. molitor were detected and shown to account for the failure of hexacanths to complete migration in the larvae. The role of the embryonic hooks and penetration gland secretions during hatching and penetration has also been discussed.

I should like to thank Professor T. R. E. Southwood for providing generous research facilities, Dr June Mahon for her advice and encouragement, and in particular, Dr W. Mordue for his continuous interest and many useful criticisms. This work was conducted during the tenure of a Science Research Council Studentship at Imperial College of Science and Technology, London, S.W. 7.

Seven cDN A clones of Schistosoma mansoni containing the C-terminal part of the deduced sequence of a mucin-like protein have been identified. The protein contains 28% threonines, 20% serines, and has a pi of 3middot;4. On Northern blots of RNA of adult worms, the cDNA clones detect 2 transcripts of 1middot;65 and 4middot;2 kb which are expressed only in female worms. The tissue of gene expression, as revealed by in situ hybridization, is the epithelium surrounding the female reproduction duct proximal to its entrance into the ootype. Accumulation of N-glycosylation sites suggests that the protein, like other mucins, might form a protective layer, coating the lining of the duct. Regarding its acidic pi, we hypothesize a role in preventing premature egg-shell formation. This is the first female-specifically transcribed sequence, hitherto known in S. mansonithat is not expressed in the vitellaria.

The hypothesis that intestinal helminth communities in freshwater brown trout are dissimilar in composition and structure to those in the European eel was tested by an analysis of component communities from 72 localities and of infracommunities from 34 localities in the British Isles and Norway. Derived indices were then compared with published data from eels. Composition of helminth communities differed considerably between the two hosts as a group of 4 species occurred commonly in trout and so gave greater predictability to the community composition. These 4 species were trout specialists and in 97% of the localities a trout specialist dominated the community rather than a generalist acanthocephalan as is typical for eels. By contrast all measures of community structure and indices of richness and diversity indicated that helminth communities in trout were isolationist in character, species poor and exhibited low diversity at both component and infracommunity levels. All values of indices for trout helminth communities were strikingly similar to those obtained from eels. Evidence of interspecific interactions within the trout helminth communities and a limit of 4 to infracommunity species richness further enhanced the similarities and suggested a common determinant of community structure. The hypothesis was thus supported in respect of species composition but refuted in respect of community structure.

The in vivo effects of a single, subcurative dose (200 mg/kg body wt of mouse) of praziquantel on the structure of the tegument and subtegumental tissues of juvenile (21-, 26- and 30-day-old) and adult Schistosoma mansoni are described. In juvenile worms praziquantel caused only moderate damage to both the tegument and subtegumental tissues although the degree of drug-induced damage was related to both the sex of the worms and to the developmental status of each individual worm. In general, male worms exhibited more extensive and longer lasting surface damage than females. However, the level and extent of the changes increased as the worms became more developmentally advanced with adult worms showing extensive damage to the tegument and vacuolization and disruption of the subtegumental tissues. The possible correlation between the stage-dependent changes in susceptibility to praziquantel and age-related changes, particularly in the phospholipid composition of the outer tegumental membrane is discussed.

The complete sequence of the 18S small subunit (SSU) ribosomal DNA of Hammondia hammondi and Sarcocystis mucosa was obtained and compared to SSU rDNA sequences of Neospora caninum, Toxoplasma gondii, Besnoitia besnoiti, 2 species of Frenkelia, 3 species of Isospora, and 13 species of Sarcocystis. Analyses showed that H. hammondi and T. gondii are monophyletic and that these taxa shared a common ancestor with N. caninum and B. besnoiti. The weight of evidence shows that S. mucosa, S. neurona, and Frenkelia species form a clade thereby supporting the conclusion that Sarcocystis is paraphyletic.

Haemosporidian parasites belonging to Haemoproteus cause avian diseases, however, vectors remain unidentified for the majority of described species. We used the laboratory-reared biting midges Culicoides nubeculosus to determine if the sporogonic development of three widespread Haemoproteus parasites completes in this insect. The midges were reared and fed on one common blackbird, white wagtail and thrush nightingale naturally infected with Haemoproteus minutus, Haemoproteus motacillae and Haemoproteus attenuatus, respectively. The engorged females were dissected in order to follow their sporogonic development. Microscopic examination was used to identify sporogonic stages. Bayesian phylogeny based on partial cytochrome b gene was constructed in order to determine phylogenetic relationships among Culicoides species-transmitted haemoproteids. All three parasites completed sporogony. Phylogenetic analysis placed Culicoides species transmitted haemoproteids in one well-supported clade, proving that such analysis readily indicates groups of dipteran insects transmitting avian haemoproteids. Available data show that 11 species of Culicoides have been proved to support complete sporogony of 18 species of avian haemoproteids. The majority of Culicoides species can act as vectors for many Haemoproteus parasites, indicating the low specificity of these parasites to biting midges, whose are globally distributed. This calls for control of haemoproteid infections during geographical translocation of infected birds.

The structure of the head and especially of the mouth-parts of these economically very important flies has been studied by many observers. The first very brief remarks on the proboscis were made by Wiedemann (1830), in his original description of the genus Glossina. He pointed out that the proboscis is almost as long as the thorax, and setiform and triangular in its basal part, the palps almost as long as the proboscis and horizontal. In the same year, Robineau-Desvoidy (1830) described another species of tsetse-fly, Glossina palpalis, but under the generic name Nemorphina, which became a synonym of Glossina. In his diagnosis of the genus, he gave an even shorter description of the proboscis which he believed was not adapted for sucking blood.

Three species of filarial worms, Wuchereria bancrofti, Brugia malayi and Brugia timori, are the causative agents of lymphatic filariasis in man, defined by the characteristic tropism of adult worms of each species for the afferent lymphatics. Reproductive activity leads to the release of large numbers of microfilariae, which circulate in the vascular system, and upon ingestion by an appropriate mosquito vector, develop through to infective third-stage larvae (L3) within 10–14 days. After a subsequent bloodmeal, the infective larvae enter the definitive host via the wound and mature to the adult stage over several months, involving two moults, during which the entire nematode exoskeleton (cuticle) is replaced.

Over the last decade, One Health has attracted considerable attention from researchers and policymakers. The concept argues that the fields of human, animal and environmental health ought to be more closely integrated. Amid a flurry of conferences, projects and publications, there has been substantial debate over what exactly One Health is and should be. This review summarizes the main trends in this emerging discussion, highlighting the fault lines between different perspectives on One Health. Some have shown that One Health's call to synthesize knowledge from different disciplines can lead to better interventions. Others, however, argue that One Health's challenge to existing practice must go further, and set out a vision that foregrounds the social and economic drivers of disease. Meanwhile, recent examples of One Health in practice highlight the potential but also the challenges of institutionalizing cooperation. We also discuss the promise and pitfalls of using complexity theory to tackle multifaceted problems, and consider how the One Health concept has been brought to bear on other issues, such as emerging new technologies. Ultimately, One Health is an important and worthwhile goal, and requires a debate that clarifies both the competing uses and the political nature of the project.

The performance of 4 serological tests for the diagnosis of Chagas disease was evaluated in Santander, Colombia, a region still presenting active transmission. Serum samples from 638 individuals were submitted to an enzyme immunoassay test (EIA), using total lysate of a local Trypanosoma cruzi strain and 52·5% were positive (335/638). A subset of this group (94 positive individuals and 90 seronegatives) was randomly selected for further serological confirmation. Three additional tests were used – indirect immunofluorescence (IIF) and 2 distinct enzyme-linked immunosorbent assays using total lysate of the Y strain (EIA BM) and a mixture of 2 recombinant antigens (EIA RA). Seventy-nine patients were seropositive in all tests (84·0% – 79/94). The number of positive sera with the IIF, EIA RA and EIA BM was 84/94 (89·4%), 80/94 (85·1%) and 79/94 (84·0%), respectively. In 15 out of the 94 EIA seropositive patients (16·0%), 10 individuals were negative in all 3 tests (10·6% – 10/94). One was negative in the EIA BM and positive in the other two tests (1·1% – 1/94) and 4 patients were positive, solely, in the IIF assay (4·3% – 4/94). Relative to the 90 EIA negative individuals, 89 were confirmed in all other tests (98·9% – 89/90). One individual, although seronegative in the IIF, was positive in both confirmatory EIA tests (1·1% – 1/90). In addition, 120 blood specimens were submitted to PCR amplification. This group consisted of 79 confirmed seropositive cases, 16 individuals with discordant serological results and 25 validated seronegative individuals. The PCR was able to detect the presence of parasite DNA in 67 out of the 79 seropositive patients (84·8%), in 8 individuals with discordant serology (50·0%) and in only one seronegative individual (4·0%). The results pointed to the necessity for performing more than one serological test, preferentially with antigens from autochthonous strains, to achieve a reliable diagnosis of Chagas disease in Colombia.