Lyme disease is caused by bacteria of the Borrelia burgdorferi genospecies complex and transmitted by Ixodid ticks. In North America only one pathogenic genospecies occurs, in Europe there are several. According to the dilution effect hypothesis (DEH), formulated in North America, nymphal infection prevalence (NIP) decreases with increasing host diversity since host species differ in transmission potential. We analysed Borrelia infection in nymphs from 94 forest stands in Belgium, which are part of a diversification gradient with a supposedly related increasing host diversity: from pine stands without to oak stands with a shrub layer. We expected changing tree species and forest structure to increase host diversity and decrease NIP. In contrast with the DEH, NIP did not differ between different forest types. Genospecies diversity however, and presumably also host diversity, was higher in oak than in pine stands. Infected nymphs tended to harbour Borrelia afzelii infection more often in pine stands while Borrelia garinii and Borrelia burgdorferi ss. infection appeared to be more prevalent in oak stands. This has important health consequences, since the latter two cause more severe disease manifestations. We show that the DEH must be nuanced for Europe and should consider the response of multiple pathogenic genospecies.

Bats are ancient hosts of Trypanosoma species and their flying ability, longevity and adaptability to distinct environments indicate that they are efficient dispersers of parasites. Bats from Acre state (Amazon Biome) were collected in four expeditions conducted in an urban forest (Parque Zoobotânico) and one relatively more preserved area (Seringal Cahoeira) in Rio Branco and Xapuri municipalities. Trypanosoma sp. infection was detected by hemoculture and fresh blood examination. Isolated parasite species were identified by the similarity of the obtained DNA sequence from 18S rDNA polymerase chain reaction and reference strains. Overall, 367 bats from 23 genera and 32 species were examined. Chiropterofauna composition was specific to each municipality, although Artibeus sp. and Carollia sp. prevailed throughout. Trypanosoma sp. infection was detected in 85 bats (23·2%). The most widely distributed and prevalent genotypes were (in order) Trypanosoma cruzi TcI, T. cruzi marinkellei, Trypanosoma dionisii, T. cruzi TcIV and Trypanosoma rangeli. At least one still-undescribed Trypanosoma species was also detected in this study. The detection of T. cruzi TcI and TcIV (the ones associated with Chagas disease in Amazon biome) demonstrates the putative importance of these mammal hosts in the epidemiology of the disease in the Acre State.

We found that the expression of mitochondrial apoptosis related genes (Bcl-2 associated protein X, BAX; apoptotic protease activating factor 1, Apaf-1; Caspase 9 and serine/threonine protein kinase, PKB) is elevated in Trichinella spiralis-infected muscles during encapsulation. Micro-dissection of the capsule and subsequent reverse transcription polymerase chain reaction (RT-PCR) confirmed that the expressions of these genes are restricted to the nurse cell. Immunocytochemistry revealed that pro-apoptosis factor (BAX, Apaf-1 and Caspase 9) are predominantly expressed in the basophilic cytoplasm (infected muscle cell origin) and anti-apoptosis factor (PKB) in the eosinophilic cytoplasm (satellite cell origin) of the nurse cell. Electron microscopy revealed that the pre-existing mitochondria in the muscle cells became swollen and disappeared immediately after newborn larva invasion, but new mitochondria of smaller size appeared in the cytoplasm. Nuclear fragmentation and condensation were observed in basophilic cytoplasm which is known to die. Together, the results suggest that the infected muscle cells transform but die through the process of apoptosis which is triggered by factors from the newly formed mitochondria. The anti-apoptosis factor may help the eosinophilic cytoplasm with its survival to ensure nurse cell function.

Given the worldwide decline of amphibian populations due to emerging infectious diseases, it is imperative that we identify and address the causative agents. Many of the pathogens recently implicated in amphibian mortality and morbidity have been fungal or members of a poorly understood group of fungus-like protists, the mesomycetozoans. One mesomycetozoan, Amphibiocystidium ranae, is known to infect several European amphibian species and was associated with a recent decline of frogs in Italy. Here we present the first report of an Amphibiocystidium sp. in a North American amphibian, the Eastern red-spotted newt (Notophthalmus viridescens), and characterize it as the new species A. viridescens in the order Dermocystida based on morphological, geographical and phylogenetic evidence. We also describe the widespread and seasonal distribution of this parasite in red-spotted newt populations and provide evidence of mortality due to infection.

Soluble adult worm antigens (SWAP) of Schistosoma mansoni were fractionated by fast protein liquid chromatography (FPLC) system, using Q-Sepharose anion-exchange resin, in order to characterize antigenic fractions that may elicit cell responses in human schistosomiasis. SWAP fractions were eluted by 20 HIM Tris–HCl solution (pH 9·6) with an increasing gradient of 1 M NaCl. The FPLC system was able to resolve 6 fractions, enumerated I to VI, according to the NaCl gradient. The analysis of each fraction on SDS–PAGE showed that fractions I to IV were constituted by multiple protein bands with Mr ranging from 21 to > 200 kDa. Large amounts of nucleic acids were evidenced in fractions V and VI, as revealed by ethidium bromide staining of agarose electrophoresis gels. Using ELISA, it was shown that sera from chronic schistosomiasis patients contained antibodies that recognized antigens in practically all fractions. Studies were designed to investigate the capacity of these fractions to induce cell proliferation and granuloma formation. It was demonstrated that fraction III stimulated a significant proliferative response of peripheral blood mononuclear cells (PBMC) from chronic schistosomiasis patients. However, fraction III coupled to polyacrylamide beads induced small granuloma formation in vitro, whereas beads coated with fractions I, II and V were able to induce significant granuloma reactions.

A nested (non-random) species composition was observed among the intestinal macroparasite communities of European eels, Anguilla anguilla. Nestedness was observed in 8 out of 10 component community samples from the rivers Thames and Test between April 2000 and October 2001. Parasite component communities consisted of mainly generalist and specialist, but also accidental species, and included acanthocephalans, cestodes, nematodes and digeneans. Nestedness was observed when component population size differed markedly between all or most parasite species, but not when the majority of species present was similarly abundant. Nestedness could not be explained in terms of host weight, log normal distribution of parasite species, or mean intensity of infection. It is proposed that nestedness occurred as a result of a sufficiently graded abundance between parasite species, which was established early in the year by colonization processes.

Agglutination reactions between living trypanosomes and sera of experimentally infected rabbits is described.

Agglutinins in infected rabbits and in hyperimmunized rabbits with dead trypanosomes appeared between 5 and 8 days and reached their maximum within 14 days. They persisted in infected untreated rabbits until death, but in infected rabbits treated with Suramin they persisted for only 3 months. In hyperimmunized rabbits the titre of agglutinins gradually fell and disappeared 4 weeks after the last inoculation.

Agglutinins appear to be species specific; sera of rabbits infected with T. brucei agglutinated homologous and heterologous strains of the T. brucei, but failed to agglutinate heterologous species of trypanosomes. Similar results were obtained with sera of other species of trypanosomes.

Four sera from naturally occurring cases of T. rhodesiense infection in man produced agglutination reactions with titre varying from 1:80 to 1:1280 with T. rhodesiense, but did not agglutinate T. brucei.

In outbred (CFLP) and inbred (NIH) mice, the inflammatory response which is thought to be party responsible for the expulsion of Trichinella spiralis from the mid-region of the small intestine, also seemed to be largely responsible fo rthe simulataneous (i.e. early) expulsion of Trichuris muris from the caecum and large intestine during concurrent primary infections. The intractive explusion operated only when the concurrent infections were timed to produce T. Spiralis expulsion before T. muris expulsion would normally occur and the effect persisted for several days after T. Spiralis has been expelled.

Interactive expulsion wasss depressed during application of the nonsteroid, anti-inflammatory drug indomethacin and by T-cell expulsion of T. spiralis. These results indicate that a T-cell mediated inflammatory response was probably the basis of the interaction.

When the timing of the infections was altered such that the expulsion of T. spiralis there was no reciprocal ecpulsion of the latter. Mice immunized againest one or the other species did not show cross-immunity on heterologus challenge, confirming that the interaction did not involve similar antigens in the two species. The interactive expulsive response is considered as an example of an indirect cross-immunity.

Forms of Trypanosoma brucei isolated from lymph nodes of cyclically or intravenously infected rats, at different stages of infection, were morphologically compared with the corresponding bloodstream forms. Unlike the pleomorphic bloodstream trypanosome population, the lymph node trypanosome population was essentially monomorphic and resembled the slender forms of the bloodstream. Values for the morphometric parameters indicated a position between the slender and the stumpy forms. The number of trypanosomes/ml of blood showed the well-known periodic fluctuations while the number of trypanosomes/g of lymph node remained fairly constant. Serology revealed that lymph node trypanosome populations differed antigenically from the trypanosome populations isolated simultaneously from the bloodstream.

A major question in the study of any parasitic disease is the relationship between infection and clinical disease. The public health importance of lymphatic filariasis has generated a large body of research in this area, both in laboratory studies (Ottesen, 1984,1989; Maizels & Lawrence, 1991) and in the field (Hayashi, 1962; Hairston & Jachowski, 1968; Denham & McGreevy, 1977; Vanamail et al. 1989 b; Bundy, Grenfell & Rajagopalan, 1991; Srividya et al. 1991 b). Despite this, there is still no conclusive explanation for the apparently complex relationship between infection and clinical disease observed in human communities. At least part of the problem may lie in the current impossibility of measuring adult worm burden in vivo (Pichon et al. 1980; Denham & Fletcher, 1987; Das et al. 1990; Grenfell et al. 1990). Although there has recently been significant progress in the development of immuno logical markers for infection status in humans (Ottesen, 1989; Day et al. 1991 a), microfilaraemia is still the most reliable measure of current infection in the field. Studies in endemic areas indicate that, far from there being any simple direct relationship between microfilaraemia and disease status, it is possible to find some individuals with microfilariae in their blood but no disease, and indeed with all other combinations of infection and disease status (Hairston & de-Meillon, 1968; Hairston & Jachowski, 1968; Beaver, 1970; Bryan & Southgate, 1976; Denham & McGreevy, 1977; Pani et al. 1991). Furthermore, the proportions of people in different categories are often observed to vary between endemic areas (Denham & McGreevy, 1977; Day et al. 1991 a).

The adhesive organ of Apatemon gracilis minor Yamaguti, 1933, consists of two lobes lying in a cup-shaped fore-body. The cytoplasmic tegument covering the apposing faces of the lobes is different from that covering their outer surfaces. The covering of the outer surface corresponds to the general tegument present on the rest of the body, whereas that on the inner surfaces is finely pitted and in certain regions is elevated to form a coarse reticulum. This specialized surface is covered externally by a plasma membrane and is in continuity with nucleated cell bodies lying below the basement layer. The cell bodies contain large quantities of granular endoplasmic reticulum as well as several Golgi complexes and numerous mitochondria. Masses of secretion bodies are present and these also occur in the extensions to the external tegument as well as within the external tegument of the lobes. When the parasite is attached the inner faces of the lobes come into contact with the vascular lamina propria of the host. The possible biological role of this specialized host–parasite interface is discussed and it is suggested that this surface specialization may form a morphological basis for the ‘placental’ function suggested for the adhesive organ by earlier workers.

The author wishes to acknowledge the research grant provided by the S.R.C. for the purchase of a vacuum coating unit and an AEI EM 6 electron microscope. The progress of this study was greatly facilitated by the excellent assistance of Mr T. Davies and Miss C. Green. The Stereoscan micrographs are published by permission of the Cambridge Instrument Company.

The spontaneous activity of the somatic muscle of the amphibian lung fluke, Haplometra cylindracea has been recorded in vitro, using an isometric force transducer system. Normal movement consisted of a continuous series of regular contractions which were maintained for over 4 h. Acetylcholine (ACh) inhibited motility and at a concentration of 1 χ 10–3 M induced a flaccid paralysis. A similar response occurred with the cholinomimetic drugs, carbachol and nicotine, although in these instances the inhibition was less easily reversed by washing with frog Ringer. The inhibitory effect of ACh was blocked by d-tubocurarine but not by atropine.

Adults of Pseudodiplorchis americanus occur in the host's urinary bladder, the typical habitat of polystomatid monogeneans in amphibians. However, larvae which invade the respiratory tract via the nostrils then migrate to the bladder through the stomach and intestine, a route which is without precedent amongst monogeneans. Parasite transmission is correlated with the spawning of the desert toad Scaphiopus couchii (June/July in Arizona, USA) and the gut migration, which takes as little as 5 min, occurs after 26 days post-infection (p.i.). Migration occurs during the host's feeding season, and therefore the parasites normally encounter maximum digestive activity along their path. Worms transferred experimentally from respiratory tract to the digestive fluids in the gut are killed within 60 s. However, natural migration is stimulated by an unidentified host factor which triggers protective adaptations, enabling parasite survival for up to 4 h in these lethal conditions. Without this essential stimulus, migration may be delayed for over 1 year and juveniles remaining in the respiratory tract undergo no development beyond that reached at 4 weeks p.i. Rapid reproductive development is resumed immediately after migration, leading to maturation around 1 month later and progressive accumulation of embryos in utero in preparation for transmission during the next summer's rains.

Proteins of the piroplasms of Theileria sergenti, T. buffeli and T. orientalis were analysed by two-dimensional polyacrylamide gel electrophoresis. Protein spot patterns of T. buffeli and T. orientalis were identical except for a few minor proteins, whereas spot patterns of two T. sergenti stocks were differentiated from those of T. buffeli and T. orientalis by a characteristic set of proteins including a major protein of molecular weight 33–34 kDa. This result indicates that Japanese T. sergenti can be phenotypically distinguishable from European and Australia Theileria species; T. orientalis and T. buffeli.

In vitro studies of the behaviour of the trypanosomatid flagellates Trypanosoma brucei and Leishmania hertigi in the presence of cell-free haemolymph of locusts, Schistocerca gregaria and cockroaches, Periplaneta americana revealed the presence of parasite agglutinins. The range of normal values of agglutination titres was 2−4 to 2−13. Physico-chemical treatment of haemolymph indicated that these agglutinins are protein or glycoprotein in nature and are only partially affected by heat treatment below 65°C, at which temperature incubation of haemolymph for 30 min abrogated all agglutination. Agglutination was not dependent on the presence of Ca2+ or Mg2+. Prior infection of locusts and cockroaches with T. brucei and L. hertigi significantly increased agglutinin titres between Days 4 and 6 in cockroaches (P < 0·05) and from Days 2 to 4 when L. hertigi was inoculated into locusts. The induced differences in titres observed in locusts infected with T. brucei were not significant. Lysozyme levels were significantly increased after inoculation of T. brucei into cockroaches compared with placebo-inoculated and uninoculated controls. L. hertigi inoculation produced significant increases in lysozyme levels compared with controls between Days 1 and 7 in locusts and 3 to 6 in cockroaches. These studies indicate that, at least in easily manipulated model systems, induced responses to intrahaemocoelic inoculation to trypanosomes and Leishmania can occur. As far as we are aware this is the first report of an induced response of an insect to such important parasites. The possibility that induced responses in natural vectors to these parasites occurs requires investigation.

Bartonella infection was explored in wild animals from Israel. Golden jackals (Canis aureus), red foxes (Vulpes vulpes), rock hyraxes (Procavia capensis), southern white-breasted hedgehogs (Erinaceus concolor), social voles (Microtus socialis), Tristram's jirds (Meriones tristrami), Cairo spiny mice (Acomys cahirinus), house mice (Mus musculus) and Indian crested porcupines (Hystrix indica) were sampled and screened by molecular and isolation methods. Bartonella-DNA was detected in 46 animals: 9/70 (13%) golden jackals, 2/11 (18%) red foxes, 3/35 (9%) rock hyraxes, 1/3 (33%) southern white-breasted hedgehogs, 5/57 (9%) Cairo spiny mice, 25/43 (58%) Tristram's jirds and 1/6 (16%) house mice. Bartonella rochalimae and B. rochalimae-like were widespread among jackals, foxes, hyraxes and jirds. This report represents the first detection of this zoonotic Bartonella sp. in rock hyraxes and golden jackals. Moreover, DNA of Bartonella vinsonii subsp. berkhoffii, Bartonella acomydis, Candidatus Bartonella merieuxii and other uncharacterized genotypes were identified. Three different Bartonella strains were isolated from Tristram's jirds, and several genotypes were molecularly detected from these animals. Furthermore, this study reports the first detection of Bartonella infection in a southern hedgehog. Our study indicates that infection with zoonotic and other Bartonella species is widespread among wild animals and stresses their potential threat to public health.

Application of quantitative methods to the study of leishmaniasis epidemiology has allowed Dye (1992) to pinpoint important biological parameters which, if they could be accurately measured in the field, would contribute most to our knowledge of the spread of disease and key targets for control. Three areas in which laboratory-based research could impact most on leishmaniasis epidemiology were highlighted by Dye (1992): (i) the development of accurate diagnostic tools which can distinguish between current and past infection; (ii) to determine the underlying molecular/genetic basis to virulence polymorphisms in the parasite and study these in the context of field epidemiological studies; and (iii) to provide the molecular tools to measure genetic variation in resistance to infection in humans and in reservoir hosts of disease. This paper describes current progress in attaining these goals, highlighting first the work on isolation and field application of genomic and kDNA probes for species-specific diagnosis, and the development of PCR-based assays which can be performed under field conditions. At a more preliminary stage, studies are described in which variability in the major molecular determinants of virulence (lipophosphoglycan, GP63, and members of the HSP7O family of stress proteins) identified through studies of laboratory models of infection, is being measured in primary field isolates of Leishmania peruviana. To complete the picture, current progress in identifying and cloning the genes which control host resistance to leishmanial infection is described, along with field studies of multicase families of human disease in which linkage analysis using marker genes from the chromosomal regions bearing these genes can be used to find evidence for their role in determining disease phenotypes in man. The leishmaniasis epidemiology will be all down to the DNA. projected view from these studies is that the future of leishmaniasis epidemiology will be all down to the DNA.

Infection of the central nervous system by Taenia solium cysticerci is the cause of human neurocysticercosis, a major neurological infection in the Third World and an emerging infectious disease in the United States. We previously isolated a cysteine proteinase from cysticerci of Taenia crassiceps and demonstrated that it degrades human IgG in vitro. We have now isolated a 48 kDa thiol-dependent proteinase from T. solium. The T. solium enzyme also degrades human IgG, but does not significantly degrade albumin. IgG degradation was inhibited by cysteine proteinase inhibitors, but not significantly by inhibitors of aspartic, serine, or metalloproteinases. The peptide substrate specificity and pH optimum resemble cathepsin L. The Km for the peptide substrate Z-Phe-Arg-AFC was calculated to be 7·0×10−6M, the Kcat was 1·98×105 s−1, and the Kcat/Km 2·84×109M−1 s−1, a value which is within the diffusion control limit for highly catalytic enzymes. We propose that immunoglobulin degradation by the T. solium cysteine proteinase may play a key role in the host-parasite interface and could be employed as a target for chemotherapy.

The size and fecundity of parasitic nematodes are constrained by the host immune response. For the parasitic nematode of rats, Strongyloides ratti, parasitic females infecting immunized rats are smaller and less fecund than those infecting naïve rats. Here, we investigated whether these constraints on size and fecundity are life-long. This was done by comparison of worms from different immunization and immunosuppression regimes. It was found that the per capita fecundity of parasitic females of S. ratti is fully reversed, but that their size is only partially reversed, if previously immunized hosts are subsequently immunosuppressed, suggesting that fecundity is not subject to life-long constraints. The host immune response also resulted in allometric changes in the parasitic females. The significance of these results with respect to the growth and control of nematode fecundity are discussed.

Neurocysticercosis (NCC) occurs following brain infection by larvae of the cestode Taenia solium. It is the leading cause of preventable epilepsy worldwide and therefore constitutes a critical health challenge with significant global relevance. Despite this, much is still unknown about many key pathogenic aspects of the disease, including how cerebral infection with T. solium results in the development of seizures. Over the past century, valuable mechanistic insights have been generated using both clinical studies and animal models. In this review, we critically assess model systems for investigating disease processes in NCC. We explore the respective strengths and weaknesses of each model and summarize how they have contributed to current knowledge of the disease. We call for the continued development of animal models of NCC, with a focus on novel strategies for understanding this debilitating but often neglected disorder.