The cercaria and sporocyst of Bucephaloides gracilescens are described from Abra alba (Wood). Observations were made on the behaviour of the cercaria and the mechanism of release from the first intermediate host. The metacercaria was obtained experimentally for the first time using Ciliata mustela (L.), a species of Gadidae from rock pools, as second intermediate host. It has not previously been recorded from this fish. Unsuccessful attempts were made to infect species of fishes from three other families, namely, Bothidae, Pleuronectidae and Gobiidae, confirming the high degree of host specificity of the metacercaria to Gadidae. The metacercaria, its development and effect on the host are briefly discussed. It was linked with the adult on the basis of comparative morphology and ecology of the hosts.

Nucleoside triphosphate diphosphohydrolases (NTPDases, GDA1_CD39 protein superfamily) play a diverse range of roles in a number of eukaryotic organisms. In humans NTPDases function in regulating the inflammatory and immune responses, control of vascular haemostasis and purine salvage. In yeast NTPDases are thought to function primarily in the Golgi, crucially involved in nucleotide sugar transport into the Golgi apparatus and subsequent protein glycosylation. Although rare in bacteria, in Legionella pneumophila secreted NTPDases function as virulence factors. In the last 2 decades it has become clear that a large number of parasites encode putative NTPDases, and the functions of a number of these have been investigated. In this review, the available evidence for NTPDases in parasites and the role of these NTPDases is summarized and discussed. Furthermore, the processes by which NTPDases could function in pathogenesis, purine salvage, thromboregulation, inflammation and glycoconjugate formation are considered, and the data supporting such putative roles reviewed. Potential future research directions to further clarify the role and importance of NTPDases in parasites are proposed. An attempt is also made to clarify the nomenclature used in the parasite field for the GDA1_CD39 protein superfamily, and a uniform system suggested.

In non-permanent parasites the separation from the host should take place in suitable habitats that allow the continuation of their life cycle. Furthermore, detachment strategies determine the parasites' dispersal capability, a characteristic on which epidemiological dynamics and the evolution of host specificity centre. In this study we experimentally investigate in the laboratory how 2 congeneric tick species, with contrasting habitat requirements, time detachment from one of their current songbird hosts (Parus major). Ixodes arboricola is a nidicolous tick, infesting bats and birds breeding or roosting in tree holes. Ixodes ricinus is a non-nidicolous generalist that parasitizes mammals, birds and even reptiles. We experimentally infested full-grown great tits, P. major, and found that I. arboricola detaches during the night, the moment when P. major sleeps in tree holes. In contrast, I. ricinus detaches during the day, the moment when birds are most active. In addition we found that all I. ricinus immatures left the birds within 5.5 days, while in I. arboricola the detachment time was long (up to 20 days) and highly variable. We discuss these findings with respect to their implications on the ticks' dispersal capability and host specificity.

Chagas disease and sleeping sickness are neglected tropical diseases closely related to poverty, for which the development of plant-derived treatments has not been a promising prospect. Thus, we systematicaly review the preclinical in vivo evidence on the applicability of plant-based products in the treatment of Trypanosoma cruzi and Trypanosoma brucei infections. Characteristics such as disease models, treatments, toxicological safety and methodological bias were analysed. We recovered 66 full text articles from 16 countries investigating 91 plant species. The disease models and treatments were highly variable. Most studies used native (n = 36, 54·54%) or exotic (n = 30, 45·46%) plants with ethnodirected indication (n = 45, 68·18%) for trypanosomiasis treatment. Complete phytochemical screening and toxicity assays were reported in only 15 (22·73%) and 32 (48·49%) studies, respectively. The currently available preclinical evidence is at high risk of bias. The absence of or incomplete characterization of animal models, treatment protocols, and phytochemical/toxicity analyses impaired the internal validity of the individual studies. Contradictory results of a same plant species compromise the external validity of the evidence, making it difficult determine the effectiveness, safety and biotechnological potential of plant-derived products in the development of new anti-infective agents to treat T. cruzi and T. brucei infections.

Avian malaria is a vector transmitted disease caused by Plasmodium and recent studies suggest that variation in its prevalence across avian hosts is correlated with a variety of ecological traits. Here we examine the relationship between prevalence and diversity of Plasmodium lineages in southeastern Amazonia and: (1) host ecological traits (nest location, nest type, flocking behaviour and diet); (2) density and diversity of avian hosts; (3) abundance and diversity of mosquitoes; and (4) season. We used molecular methods to detect Plasmodium in blood samples from 675 individual birds of 120 species. Based on cytochrome b sequences, we recovered 89 lineages of Plasmodium from 136 infected individuals sampled across seven localities. Plasmodium prevalence was homogeneous over time (dry season and flooding season) and space, but heterogeneous among 51 avian host species. Variation in prevalence among bird species was not explained by avian ecological traits, density of avian hosts, or mosquito abundance. However, Plasmodium lineage diversity was positively correlated with mosquito abundance. Interestingly, our results suggest that avian host traits are less important determinants of Plasmodium prevalence and diversity in southeastern Amazonia than in other regions in which they have been investigated.

Studies with both the light and electron microscope on the bladder wall of Cysticercus longicollis have revealed details of its structure and shown that it contains structures comparable with those of adult cestodes. The structure of the everted scolex of the fully developed cysticercus has also been studied. Development of the scolex and rostellum has been briefly considered and is similar to that of C. fasciolaris and C. pisiformis. The importance of the tegument in both bladder wall and scolex is emphasised.

The rostellar hooks appear first as small cones to which a base is added after some growth has occurred. Mature and immature hooks probably contain keratin. Results of histochemical tests on this and other parts of the cysticercus have been given.

Thanks are due to Dr L. G. Goodwin, Director of the Nuffield Institute of Comparative Medicine, London Zoo, for allowing the author to use the EM 6 B and photographic facilities. Dr J. Mahon of Imperial College, London, kindly read the script, gave advice on it and provided photomicrographic facilities. The author is grateful to the Principal and Governors of West Ham College of Technology for general and financial support of the project.

One stock of each of Leishmania mexicana mexicana and L. m. amazonesis together with two stocks of L. braziliensis panamensis and L. b. braziliensis were tested for infectivity in inbred mouse strains Balb/c and CBA/H. The infectivity was compared with hamsters and the outbred CD1 mice. Balb/c mice were more susceptible than hamsters to L. mexicaba and L. braziliensis panamensis. Balb/c mice were not susceptible to L. b. braziliensis. CBA/H mice showed a low susceptibility to infection while CD1 mice showed an intermediate response

In order to replicate efficiently within the host, viruses have evolved multiple strategies to evade the host's immune system. In many cases viruses have actually hijacked various components of the host's immune system to ensure their own survival. One such strategy is the expression of virus encoded cytokines and cytokine receptors. Members of the poxvirus and herpesvirus families have been particularly successful with this strategy. The study of virus survival strategies provides important information regarding both virus biology as well as information about the immune system itself.

Plasmodium knowlesi a simian malaria parasite is currently affecting humans in Southeast Asia. Malaysia has reported the most number of cases and P. knowlesi is the predominant species occurring in humans. The vectors of P. knowlesi belong to the Leucosphyrus group of Anopheles mosquitoes. These are generally described as forest-dwelling mosquitoes. With deforestation and changes in land-use, some species have become predominant in farms and villages. However, knowledge on the distribution of these vectors in the country is sparse. From a public health point of view it is important to know the vectors, so that risk factors towards knowlesi malaria can be identified and control measures instituted where possible. Here, we review what is known about the knowlesi malaria vectors and ascertain the gaps in knowledge, so that future studies could concentrate on this paucity of data in-order to address this zoonotic problem.

Adult Onchocerca volvulus worms obtained by enzyme digestion from nodules of infected Mexicans were radio-isotope labelled by the chloramine-T or Bolton–Hunter methods. No antigenic determinants were detected in extracts of worms labelled by the chloramine-T method but 3 antigens were detected in extracts of the Bolton–Hunter labelled worms. Two were present in such small amounts that it was impractical to investigate them further, but a major component of mol. wt 20 kDa was purified by gel filtration and used in a serological survey of inhabitants of villages in Southern Mexico. Using the 20 kDa antigen, which is superficially located on both sexes of O. volvulus, sera from both non-endemic and endemic regions were analysed by radio-immunoprecipitation of this antigen. In Southern Mexico, the average sensitivity of the test was 92%, and the specificity 98%. Whilst the 20 kDa antigen did not detect antibodies in the sera of Trinidadians infected with Wuncheria bancrofti or Mansonella ozzardi, this antigen detected high levels of antibodies in Indians exposed to W. bancrofti.

Upon infection with a pathogen, eukaryotic cells can undergo programmed cell death as an ultimate response. Therefore, modulation of apoptosis is often a prerequisite to establish a host-pathogen relationship. Some pathogens kill macrophages by inducing apoptosis and thus overcome the microbicidal arsenal of the phagocyte. Apoptotic macrophages, on the other hand, can elicit an inflammation by secretion of proinflammatory cytokines. Shigella flexneri, the aetiological agent of bacillary dysentery, induces apoptosis in macrophages which, in agony, specifically release mature interleukin-1β (IL-1β). This cytokine attracts neutrophils (PMN) to the site of infection resulting in the massive colonic inflammation characteristic of bacillary dysentery. Shigellosis represents a paradigm of a proinflammatory apoptosis in a bacterial infection. The molecular link between apoptosis and inflammation is interleukin-1β converting enzyme (ICE) which is activated during macrophage apoptosis and binds to IpaB, a secreted Shigella protein.

Theileria mutans (Aitong) isolated from cattle exposed in the Narok District of Kenya and blood-passaged through cattle 8 times, appeared to have lost its original pathogenicity for cattle. It was demonstrated that the parasite was trans-stadially transmissible by the tick Amblyomma variegatum but not by Rhipicephalus appendiculatus. Four tick–bovine passages were made using A. variegatum, and infective parasites were also harvested from A. variegatum nymphs which had been fed for 5 days on rabbits. Blood containing piroplasms, or lymphoid cells infected with schizonts taken from cattle, at the 2nd tick–bovine passage were shown to be infective on inoculation.

The course of the T. mutans infections in the cattle was studied. In tick-induced infections macroschizonts occurred transiently, persisting longest in circulating lymphoid cells. Microschizonts were rarely detected. The macroschizonts were morphologically distinct from those of other Theileria species described from East Africa.

In tick-induced infections, the piroplasm parasitaemia increased rapidly and there was evidence of restored pathogenicity of the parasite since high piroplasm parasitaemias were associated with a marked anaemia.

In vitro excretory/secretory products of 4-week (immature) and 8- week-old (mature) Fasciola hepatica parasites, derived from rats, were injected together with adjuvant into naive rats and mice. Resistance to infection was assessed in rats by counting adults in the bile ducts at 9 weeks, or in mice by recording deaths after oral challenge with a high dose of viable metacercariae. Exposure of rats to excretory/secretory products of immature F. hepatica conferred a significant degree of resistance which was comparable to the level of resistance induced following oral administration of a low number of metacercariae. No protection against infection was seen in rats injected with excretory/secretory products from mature, bile duct-derived worms. In mice, no obvious mouse strain variation in susceptibility to first infection existed and hypothymic nude mice were as susceptible to infection as intact mice. As determined by protection against death, vaccination with excretory/secretory products derived from immature P. hepatica was without effect in mice. It is concluded that ‘host protective antigens’, at least for rats, were present in the excretory/secretory products of immature F. hepatica larvae.

Dactylogyrus (Monogenea) species were studied on the gills of roach (Rutilus rutilus) from a total of 293 fish in 3 interconnected lakes in Central Finland. One of the lakes is eutrophic and polluted by a paper and pulp mill, one is eutrophic and one is oligotrophic. Nine Dactylogyrus species were found. The structure of the monogenean communities was analysed at the component and infracommunity level and the Dactylogyrus fauna of the lakes was compared. Although it was found that the component communities tended to be very similar there were also differences. The abundance and diversity were highest in the polluted lake; the infracommunities of this lake were considerably more often dominated by Dactylogyrus micracanthus and the similarities between the infracommunities were higher within the lakes than between the lakes. It is suggested that these differences are due to the differing water quality of the lakes. The nature of the monogenean community, its possible interactivity, is also discussed.

Members of the phylum Microspora are a group of unusual, obligate intracellular eukaryotic parasites that infect a wide range of hosts. However, there are a limited number of microsporidial infections reported in avian hosts, and no parasite species has been defined as an avian pathogen. A microsporidian organism was recovered from the droppings of a clinically normal peach-faced lovebird (Agapornis roseicollis) and established in in vitro culture. Intermittent parasite spore shedding was documented over a 2-month period using calcofluor M2R staining of cloacal swabs. The organism was identified as Encephalitozoon hellem based on protein and antigenic profiles and molecular sequencing of the small subunit and internal transcribed spacer regions of the ribosomal RNA gene.

1. In an alkaline inorganic solution containing borate, no bacterial disintegration of tissues occurs in a week.

2. Survival is prolonged by adding sugars to this solution, but not by the addition of bile salt or peptone. Monosaccharides are more effective than disaccharides, and both may enter the worm through its body wall.

3. The effect of variations in certain physicochemical conditions was studied. Wide ranges of osmotic pressure, of the K/Naratio, and of the Ca/Na ratio, have little effect on the worms. The optimum pH is c. 8.4, and t h e optimum temperature c. 36° C. Approximately anaerobic conditions decrease the survival time.

4. The effect of various bactericides, bacteriostatics and anthelmintics upon the worm were investigated in a preliminary manner. Many bactericides are toxic, certain anthelmintics are not. Survival is prolonged by 1/5000 trypan blue.

5. A satisfactory medium for large-scale ‘culturing’ is: NaCl 150 mM., KC1 10 mM., CaCl2 1 mM., borax 6 mM., glucose 30 mM. (pH 8.6). In this the worms survive for c. 60 hr. at a temperature of 36° C.

BALB/c mice were characterized as more resistant to infection with Heligmosomoides polygyrus (Nematoda) than C57BL/6 mice based on lower establishment and survival during a primary infection and stronger protection induced by an immunizing regime. It was hypothesized, therefore, that C57BL/6 mice would be more heavily infected than BALB/c mice when they lived together as a single population in a large indoor arena where transmission occurred through contact between the mice and damp peat trays where parasite eggs developed into larvae. Fifty female mice (including 5 infected mice) of each strain were placed in a 3.2 x 0.8 m arena. Net egg production and numbers of larvae acquired by sentinel mice of each strain were monitored every two weeks. The experiment was replicated twice. The results did not support the hypothesis. No difference was detected between strains of mice in the number of larvae acquired by sentinel mice during 24 h exposure periods, or in the numbers of worms present after 12 or 23 weeks. Net egg production was also comparable between strains. A hypothesis that the unexpected similarity of infection in the two strains was related to differences in rates of contact with the peat trays was not supported by preliminary data on mouse behaviour that revealed equal frequency of contact with peat trays between strains. A second hypothesis that continuous exposure to larvae led to similar infection levels in the two strains (in contrast to the controlled characterization experiments) was also unsupported. Mice were infected weekly with 10, 50 or 100 larvae for 5 or 10 weeks. Net egg production and numbers of worms were consistently higher in C57BL/6 than BALB/c mice. At this time it is not clear why infection in the two strains was virtually identical in the large arenas but clearly distinct in all controlled infection experiments.

Leishmania (Viannia) braziliensis is a protozoan that causes mucocutaneous leishmaniasis, which is an infectious disease that affects more than 12 million people worldwide. The available treatment is limited, has side-effects or is inefficient. In a search for alternative compounds of natural origin, we tested the microbicidal activity of Piper aduncum essential oil (PaEO) on this parasite. Our data showed that PaEO had an inhibitory effect on the growth of L. braziliensis promastigotes with an IC50/24 h=77·9 µg mL−1. The main constituent (nerolidol: 25·22%) presented a similar inhibitory effect (IC50/24 h = 74·3 µg mL−1). Ultrastructural observation of nerolidol-treated parasites by scanning and transmission electron microscopies revealed cell shrinkage and morphological alterations in the mitochondrion, nuclear chromatin and flagellar pocket. Flow cytometry analysis showed a reduction in the cell size, loss of mitochondrial membrane potential, phosphatidylserine exposure and DNA degradation, which when associated with the morphological changes indicated that nerolidol induced incidental cell death in the L. braziliensis promastigotes. The results presented here indicate that nerolidol derivatives are promising compounds for further evaluation against Leishmania parasites.

The genetic differences between praziquantel-resistant (R) and susceptible (S) strains of Schistosoma mansoni (Fallon & Doenhoff, 1994) were explored using RAPD and by cloning differentially expressed mRNAs by subtractive PCR. No differences between the 2 strains were detectable by RAPD using 41 different primers indicating that no major genomic rearrangements were present. Subtractive PCR generated a number of fragments, 1 of which was shown to correspond to an over-expressed mRNA in the R strain and to encode a fragment of the subunit 1 of cytochrome-c oxidase (SCOX1). In the absence of a complete sequence for this gene, we used EST sequences to compile a consensus sequence for the 904 bp at the 3′ end that enabled us to choose primers for semi-quantitative RT–PCR. This technique showed that SCOX1 was indeed over-expressed about 5 to 10-fold in the R strain whereas the genes encoding the 28 kDa glutathione S-transferase, glutathione peroxidase, NADH dehydrogenase subunit 5 and the ATP-binding cassette family protein SMDR2 were not. In contrast, cytochrome-c oxidase enzyme activity was 4-fold lower in the R strain than in the S strain.

Genetic analysis of Trypanosoma spp. depends on the detection of variation between strains. We have used the amplified fragment length polymorphism (AFLP) technique to develop a convenient and reliable method for genetic characterization of Trypanosome (sub)species. AFLP accesses multiple independent sites within the genome and would allow a better definition of the relatedness of different Trypanosome (sub)species. Nine isolates (3 from each T. brucei subspecies) were tested with 40 AFLP primer combinations to identify the most appropriate pairs of restriction endonucleases and selective primers. Primers based on the recognition sequences of EcoRI and BglII were chosen and used to analyse 31 T. brucei isolates. Similarity levels calculated with the Pearson correlation coefficient ranged from 15 to 98%, and clusters were determined using the unweighted pair-group method using arithmetic averages (UPGMA). At the intraspecific level, AFLP fingerprints were grouped by numerical analysis in 2 main clusters, allowing a clear separation of T. b. gambiense (cluster I) from T. b. brucei and T. b. rhodesiense isolates (cluster II). Interspecies evaluation of this customized approach produced heterogeneous AFLP patterns, with unique genetic markers, except for T. evansi and T. equiperdum, which showed identical patterns and clustered together.