As a consequence of comprehensive transcriptome analysis followed by sequencing and draft assembly of the genome, the emphasis of schistosome research is shifting from the identification of genes to the characterization of their functions and interactions. Developmental biologists have long used whole mount in situ hybridization (WISH) to determine gene expression patterns, as a vital tool for formulating and testing hypotheses about function. This paper describes the application of WISH to the study of gene expression in larval and adult schistosomes. Fixed worms were permeablized by proteinase K treatment for hybridization with digoxygenin-labelled RNA probes, with binding being detected by alkaline phosphatase-coupled anti-digoxygenin antibodies, and BM Purple substrate. Discrete staining patterns for the transcripts of the molecules Sm29, cathepsin L, antigen 10.3 and chorion were observed in the tegument cell bodies, gut epithelium, oesophageal gland and vitelline lobules, respectively, of adult worms. Transcripts of the molecules SGTP4, GP18-22 and cathepsin L were localized to tegument cell bodies and embryonic gut, respectively, of lung schistosomula. We also showed that Fast Red TR fluorescent substrate can refine the pattern of localization permitting use of confocal microscopy. We believe that method of WISH will find broad application, in synergy with other emerging post-genomic techniques, such as RNA interference, to studies focused at increasing our molecular understanding of schistosomes.

The life-cycles of two closely related cephalobaenid pentastomids, Raillietiella gehyrae and Raillietiella frenatus, which utilize geckos as definitive hosts and cockroaches as intermediate hosts, have been investigated in detail. Early development in the fat-body of cockroaches involves 2 moults to an infective, 3rd-stage larva which appears from 42–44 days post-infection. Complete development in geckos involves a further 5 moults in the case of males and 6 for females. Males mature precociously and copulation is a once-in-a-lifetime event which occurs around day 80 post-infection when both sexes are the same size but the uterus of the female is undeveloped. Sperm, stored in the spermathecae, is used to fertilize oocytes which slowly accumulate in the developing saccate uterus. Patency commences when the uterus carries approximately 4000–5500 eggs but only 25–36 % of these contain fully developed primary larvae. Since only mature eggs are deposited, we postulate that the vagina (?) of the female must be equipped with a selective filter that allows through large eggs but retains smaller, immature eggs. Thus the only limit on fecundity is the total number of sperms in the spermathecae and this is precisely the same factor that constrains egg production in the advanced order Porocephalida.

The high energy costs of egg-shell production in many helminths suggests that this structure plays an important role in their biology. The mechanical and chemical resistance of the egg-shell and the barrier it provides to the entry and loss of material are important in the survival of the free-living stages within the egg. The presence of egg filaments may increase the availability of infective stages and the operculum may be important in the infective process.

Two stocks of Trypanosoma congolense were established in culture at 28 °C using trypanosomes from the proboscides of infective Glossina morsitans. Successful primary cultures were initiated by placing an infected tsetse proboscis beside a bovine dermal collagen explant in Eagle's minimum essential medium supplemented with foetal calf serum. The trypanosomes multiplied rapidly in the medium and also gradually formed an adherent layer on the plastic surface of the culture vessel. Three primary cultures produced organisms infective for mice from 14, 20 and 35 days after initiation and thereafter continuously until days 76, 76 and 52 when they were discarded. Four attempts to initiate infective cultures using infected tsetse proboscides in medium without dermal explants were unsuccessful. When trypanosomes from primary cultures were placed in culture medium with proboscides from uninfected tsetse flies, the parasites multiplied, formed an adherent layer in the culture flasks and were seen in the proboscides within 24 h. A line of 1 stock was serially sub-passaged in this way 4 times during a period of 215 days. Infectivity titrations in mice indicated that primary and sub-passaged cultures each contained similar numbers of infective organisms. Another line of the same stock was also sub-passaged 4 times in medium alone over a period of 186 days. These sub-cultures again retained infectivity for mice, but titrations showed a decrease in infective organism production in the 4th sub-culture. Primary and sub-passaged cultures all included a variety of morphologically different developmental forms of T. congolense, closely resembling those described in the labrum and hypopharynx of Glossina by previous workers. Short metacyclic-like trypanosomes and organisms with proteinaceous surface coats were present in infective cultures. Cultures were successfully re-established after cryopreservation at −196 °C and retained the ability to produce infective organisms.

This study was performed with Litomosoides sigmodontis, the only filarial species which can develop from the infective larvae to the patent phase in immunocompetent laboratory BALB/c mice. Parasitological features and immune responses were analysed up to 3 months before and after challenge inoculation, by comparing 4 groups of mice: vaccinated challenged, challenged only, vaccinated only, and naive mice. Male larvae were very susceptible to irradiation and only female irradiated larvae survived in vivo. Protection, assessed by a lower recovery rate, was confirmed and was established within the first 2 days of challenge. This early reduction of the recovery rate in vaccinated challenged mice was determined by their immune status prior to the challenge inoculation. This was characterized by high specific IgM and IgG subclass (IgG1, IgG2a and IgG3) levels, high specific IL-5 secretion from spleen cells in vitro and a high density of eosinophils in the subcutaneous connective tissue. Six h after the challenge inoculation, most tissue eosinophils were degranulated in vaccinated challenged mice. Thus, in the protocol of vaccination described, protection appeared mainly to result from the stimulation of a Th2 type response and eosinophils seemed to be the main effectors for the increased killing of infective larvae in vaccinated challenged mice. Two months after challenge inoculation, the percentage of microfilaraemic mice was lower in vaccinated challenged mice as a consequence of this overall reduction in the worm load. In both vaccinated challenged and challenged only groups, the in vitro splenocyte proliferative capacity was reduced in microfilaraemic mice.

The aim of the study was to investigate the longitudinal changes of exsheathment of ovine and bovine 3rd-stage strongylid larvae in an artificial rumen (RUSITEC) and to compare the results with in vivo data obtained from rumen-fistulated sheep. Infective larvae were incubated in nylon mesh bags in the sheep rumen or the RUSITEC apparatus for periods of 1, 6 and 12 h, respectively. The 12 h exsheathment rates in the rumen and the RUSITEC apparatus (in parentheses) were as follows: Haemonchus contortus: 100% (100%), Ostertagia circumcincta: 100% (76%), O. leptospicularis: 100% (100%), O. ostertagi: 53% (59%), Trichostrongylus axei: 100% (100%), T. colubriformis: 37% (36%), Cooperia curticei: 94% (76%), C. oncophora: 95% (89%), Nematodirus filicollis: 0% (N.D.), N. spathiger: 11% (15%), N. battus: 7% (5%), Oesophagostomum venulosum: 17% (9%), Chabertia ovina: 7% (2%), Dictyocaulus filaria: 1% (N.D.). Larvae of Nematodirus spp. and T. colubriformis showed a quick rise of the exsheathment rate 2 h after transfer into the abomasum. These results confirm that exsheathment generally occurs in the part of the gastrointestinal tract immediately anterior to the habitat of the adult parasite. The overall similar course of exsheathment in both systems indicates that the essential stimuli for exsheathment were generated and maintained under in vitro conditions of the artificial rumen. In both systems, the bicarbonate concentration and the pH reflected a similar status of the H2CO3/HCO buffer system, which is known to provide the essential stimuli for larval exsheathment of the abomasal species. These results give evidence that the RUSITEC system represents a valid system for studying the kinetics of exsheathment of strongylid nematodes under in vitro conditions. For 7 of the species investigated the obtained results represent the first data on larval exsheathment in vivo and in vitro.

1. The second ecdyses experimentally produced in 1 in 20 and other watery dilutions of Milton hypochlorite are described. These occur without the detachment of a typical cap. The larva is passively propelled part of the way out through a hole at the anterior tip of the sheath, and completes its emergence by its own movements.

The explanation of this is that the chlorine in the Milton solution alters the chemical composition of the sheath with two results: (a) the permeability of the sheath is altered so that increased internal pressure results, by which the larva is propelled out of the hole at the anterior tip, and (b) the sheath is rendered soluble in the NaOH in the Milton solution so that it is subsequently dissolved. The larva is expelled through a hole at the anterior tip before the whole sheath is dissolved because the sheath gives way here first to the combined effects of the increased internal pressure and the solvent action of the NaOH, this being its weakest point, where the remains of the mouth of the second larva are.

The larva is only rarely propelled completely out by the raised internal pressure, namely, when the hole at the anterior tip is big enough to allow its widest part, at the base of its oesophageal region, to pass; or, alternatively, when the internal pressure is high enough to force this part of it through the hole. Usually it requires the help of its own movements to force this widest part of it through the hole.

2. Neither chlorine, oxygen, nor caustic soda alone can cause ecdyses, although the latter may dissolve the sheaths of larvae kept long in cultures or exposed long upon pastures, so that a chemical change in their sheaths has occurred similar to that just described. Caustic soda may then also so weaken and thin the sheaths that larvae, if they are active enough, may break their way out.

Neither carbonic nor hydrochloric acids, nor solutions of sodium chloride, could alone cause ecdyses; nor could solutions of sodium carbonate, although these acted upon “older” larvae in much the same way as solutions of caustic soda, which they must contain.

3. Larvae, however, whether they were recently mature or had been long kept in cultures, showed, when they were treated with chlorine water or with hypochlorite solutions acidified with excess of either HCl or acetic acids, effects which indicated that the conclusion described in (a) above was correct. They never exsheathed, but their sheaths were blistered and thinned and frequently distended also, with the exception of the cap which is detached at the ecdysis; this was usually neither blistered, thinned nor distended. This distension was especially marked when these larvae were transferred, after this treatment with chlorine, to solutions hypotonic to them. In hypertonic solutions, on the other hand, the larvae were shrunken. This perhaps explains why larvae are often shrunken away from their sheaths in old cultures from which much evaporation has occurred or when they have been exposed upon pastures.

Their sheaths were, moreover, rendered soluble in 0·4 or 0·8 per cent. NaOH by this treatment with chlorine, so that treatment with chlorine, followed by immersion in weak NaOH, will exsheath the larvae, whether they are active or not, by dissolving off their sheaths. This probably explains why larvae exposed on pastures or kept long in cultures, exsheath sometimes in alkaline media such as artificial pancreatic juice, or in the saliva of sheep.

4. Observation of ecdyses that occurred at 38° C. in about 8 days in mixtures of 0·5 per cent. solutions of HCl and 0·5 per cent. NaOH or in 0·5 per cent. HCl followed by 0·5 or 0·8 per cent. NaOH, showed that these always occurred by the detachment of a typical cap, and that the process was essentially the same as that described above. An alteration of the permeability of the sheath occurred by which the pressure inside it was increased, so that the sheath was often distended. The sheath was at the same time rendered soluble in NaOH.

The cap which was detached at the ecdysis resisted, however, this distension, perhaps because it had a slightly different chemical composition, so that tension existed at the base of this more rigid cap, between it and the more flexible and elastic part of the sheath behind it. The tension at this point was further observed to be increased by specific rotatory movements of the oral end of the larva, which incidentally also determined the length of the cap, and by movements of the more flexible and elastic part of the sheath behind the cap, by which it could be repeatedly rolled up on to the cap and back again, as rubber tubing may be rolled up on to a tap. All these movements, especially when they acted upon a distended sheath, ruptured first the inner layer of the sheath at the base of the cap, and then the much stronger outer layer.

The larva then emerged by its own movements; or sometimes it was propelled out passively part of the way by the release of the high internal pressure.

Both the rotatory movements of the oral end of the larva before the detachment of the cap, and the bending and swimming movements of the whole larva by which it extricates itself from the sheath after the cap has been detached, are essential to successful and normal ecdyses. The rotatory movements of the oral end are probably most effective when the oral tip of the sheath is fixed against some resistant object, as skin-penetrating larvae may, for example, fix it against the skin. This fixation of the oral end is not, however, necessary, because most of the ecdyses here recorded occurred in this way in drops quite free of any solid or semi-solid matter.

5. Some experiments are briefly described which indicate that mechanical damage to the sheaths, or friction applied to them, cannot be more than secondary factors which influence only the ecdyses of so-called “older” larvae, whose sheaths are already chemically altered by climatic factors or long life in cultures, with results similar to those which follow treatment with chlorine.

6. It is suggested that factors similar to those indicated above may be present in the stomach and duodenum of the host and may govern any second ecdyses that occur in these situations; and that changes in the sheaths, similar to those produced by chlorine in the experiments here described, may be produced outside the body of the host, by climatic factors, so that the sheaths become soluble in the saliva or other alkaline digestive juices.

7. All attempts failed to induce the third ecdysis of larvae exsheathed and sterilised by 1 in 20 dilutions of Milton with water, and kept in sterile media until they were ready for this ecdysis. These larvae also, like the infective larvae, were susceptible to changes in the tonicity of the media in which they were kept, so that their sheaths could be alternately distended or collapsed upon them, and the larvae themselves could be shrunken or restored to normal by alterations in the concentration of the media. These third (or first parasitic) larvae showed a remarkable power of resistance to such treatment and seemed to be more resistant to it than infective larvae are.

8. Further investigations of the second ecdyses by biophysical methods may bring all the ecdyses of parasitic nematodes under experimental control and so make possible the artificial cultivation of the adult parasites. They may also suggest methods of altering the permeability of the cuticle of adult nematodes, so that anthelmintics may be found which will penetrate this more readily and at the same time will not be toxic to the host.

Four species of Eimeria from fowls were able to develop in chicken embryos following the inoculation of sporozoites. Three species (E. brunetti, E. mivati and E. tenella) were able to complete the whole of their endogenous cycle in embryos. E. necatrix developed to late schizogony, E. acervulina and E. maxima did not develop.

The life-cycles appeared to be delayed, and in the case of E. tenella embryo mortality was associated with heavy parasitism of the chorioallantoic membranes. Oocysts recovered from urate deposits in the allantoic cavity sporulated normally and induced infections in chickens.

Attempts to infect turkey and quail embryos with E. tenella or chicken and turkey embryos with E. stiedae were unsuccessful.

The implications of the findings are discussed.

I wish to thank Dr C. Horton-Smith for his encouragement and guidance with this work; Dr M. E. Rose for help in the preparation of the manuscript and Mr B. J. Millard for careful technical assistance.

In this study, cDNA microarray analysis of a closely related species, Leishmania major, was used as a screening tool to compare antimonial-resistant and susceptible clinical isolates of Leishmania donovani in order to to identify candidate genes on the basis of antimony resistance. Clinically confirmed resistant isolate 39 and sensitive isolate 2001 were used in this study. Many differentially regulated genes were identified whose expression levels differ in sodium antimony gluconate (SAG)-treated patients. Interestingly, genes on the array, showing changes in expression of over 2-fold revealed the identity of ABC transporters, which are known determinants of drug resistance in laboratory mutants. The functionality of the transporters was validated by flow cytometry which, being biologically informative, provides direct clues to gene function. The results suggest that isolate 39 could have developed resistance by an increased multidrug resistance protein (MRP)-like pump. This study provides preliminary clues to the role of a thiol-dependent efflux system in antimonial resistant clinical isolates of Leishmania donovani.

A guinea-pig immunoglobulin-G linked agarose column was used to detect the immunoglobulin-G binding proteins (IGBP) in the ixodid ticks, Rhipicephalus appendiculatus, Amblyomma variegatum and Ixodes hexagonus. IGBPs were found in salivary gland extract (SGE) of the unfed ticks of all 3 species. The sizes of the IGBPs, as determined by SDS–polyacrylamide gel electrophoresis, differed between species. In R. appendiculatus 2 IGBP bands were detected in haemolymph collected from unfed females and males, and an additional 78 kDa IGBP was detected in haemolymph samples of male and female ticks that had fed for 6 days. Although there was no difference in the IGBP profile of SGE derived from unfed male and female R. appendiculatus, 2 new IGBPs were detected in the SGE of the male ticks after they had fed for 6 days. The possible function of IGBP in ticks is discussed.

Blood examination by microhaematocrit and haemoculture of 459 snakes belonging to 37 species revealed 2·4% trypanosome prevalence in species of Viperidae (Crotalus durissus and Bothrops jararaca) and Colubridae (Pseudoboa nigra). Trypanosome cultures from C. durissus and P. nigra were behaviourally and morphologically indistinguishable. In addition, the growth and morphological features of a trypanosome from the sand fly Viannamyia tuberculata were similar to those of snake isolates. Cross-infection experiments revealed a lack of host restriction, as snakes of 3 species were infected with the trypanosome from C. durissus. Phylogeny based on ribosomal sequences revealed that snake trypanosomes clustered together with the sand fly trypanosome, forming a new phylogenetic lineage within Trypanosoma closest to a clade of lizard trypanosomes transmitted by sand flies†. The clade of trypanosomes from snakes and lizards suggests an association between the evolutionary histories of these trypanosomes and their squamate hosts. Moreover, data strongly indicated that these trypanosomes are transmitted by sand flies. The flaws of the current taxonomy of snake trypanosomes are discussed, and the need for molecular parameters to be adopted is emphasized. To our knowledge, this is the first molecular phylogenetic study of snake trypanosomes.

Although widely used, the term repellency needs to be employed with care when applied to ticks and other periodic or permanent ectoparasites. Repellency has classically been used to describe the effects of a substance that causes a flying arthropod to make oriented movements away from its source. However, for crawling arthropods such as ticks, the term commonly subsumes a range of effects that include arthropod irritation and consequent avoiding or leaving the host, failing to attach, to bite, or to feed. The objective of the present article is to highlight the need for clarity, to propose consensus descriptions and methods for the evaluation of various effects on ticks caused by chemical substances.

Three groups of lambs, aged 3, 5 and 6 months respectively, were infected daily with 5000 infective larvae of Trichostrongylus colubriformis for periods of 15–20 weeks. Some of the lambs also received a single challenge infection at the end of week 16. The course of the infections was monitored by means of faecal egg counts, measurement of live-weight gains and regular post mortem worm counts.

There was an initial rapid increase in egg counts soon after patency, which was followed by an exponential fall in the counts in most lambs. This fall seemed to precede the expulsion of worms by a few weeks and was associated with reduced fecundity in the female worms. Furthermore, although the trend of the egg counts of some lambs suggested that a self-cure reaction had taken place, in a number of these lambs the low faecal egg counts did not reflect the size of their worm burden.

Heavy worm burdens were usually associated with clinical symptoms of trichostrongylosis, including anorexia, diarrhoea and loss of weight. As the lambs developed resistance to reinfection and expelled their worm burden a rapid clinical recovery occurred, except in a few lambs which appeared to have suffered irreversible damage from the earlier heavy worm burden.

The worm burden in most lambs appeared to be cumulative during the first 4–8 weeks before they developed a strong resistance to reinfection. There was considerable loss of the adult worm burden by 8–15 weeks after initial infection and some evidence of stunting in the remaining parasites.

The immunological control of T. colubriformis infections in these lambs was achieved by means of the development of resistance to reinfection, inhibition of the ovulation of the female worms, stunting of adult worms and expulsion of adult worms by resistant lambs. These may be separate immune phenomena requiring different thresholds of parasitic material in individual animals, depending on their age, the rate and duration of infection and their innate ability to develop resistance to the parasite.

The structural relationship between cells of the parenchyma and those of the alimentary and excretory systems, and tegument are described.

Junctional complexes are formed in areas of close cell apposition. They occur laterally on invaginations of parenchymal processes which are embedded in the epithelial cells of the alimentary and excretory systems, and on flat plaques between parenchymal cells and the tegument.

The ultrastructure of the complexes has been resolved and a three-dimensional interpretation is put forward. It is suggested that the complex is a type of desmosome.

The findings reported here add support to the suggestion made in a previous paper that the parenchyma may function as a transport system in this fluke.

We wish to acknowledge grants from the Wellcome Trust and the S.R.C. for the purchase of an Akashi TRS 50 and an A.E.I. EM 6B electron-microscope respectively. This research and that reported in a previous paper were carried out while one of us (S.S.E.G.) was in receipt of a Training Studentship Grant from the Wellcome Trust.

We also wish to thank Mr W. Ferguson and Mr A. Lyness for photographic and technical assistance.

One of the major threats to biodiversity involves biological invasions with direct consequences on the stability of ecosystems. In this context, the role of parasites is not negligible as it may enhance the success of invaders. The red-eared slider, Trachemys scripta elegans, has been globally considered among the worst invasive species. Since its introduction through the pet trade, T. s. elegans is now widespread and represents a threat for indigenous species. Because T. s. elegans coexists with Emys orbicularis and Mauremys leprosa in Europe, it has been suggested it may compete with the native turtle species and transmit pathogens. We examined parasite transfer from American captive to the two native species that co-exist in artificial pools of a Turtle Farm in France. As model parasite species we used platyhelminth worms of the family Polystomatidae (Monogenea) because polystomes have been described from American turtles in their native range. Phylogenetic relationships among polystomes parasitizing chelonian host species that are geographically widespread show patterns of diversification more complex than expected. Using DNA barcoding to identify species from adult and/or polystome eggs, several cases of host switching from exotic to indigenous individuals were illustrated, corroborating that parasite transmission is important when considering the pet trade and in reintroduction programmes to reinforce wild populations of indigenous species.

The abundance and diversity of parasites vary among different populations of host species. In some host-parasite associations, much of the variation seems to depend on the identity of the host species, whereas in other cases it is better explained by local environmental conditions. The few parasite taxa investigated to date make it difficult to discern any general pattern governing large-scale variation in abundance or diversity. Here, we test whether the abundance and diversity of gamasid mites parasitic on small mammals across different regions of the Palaearctic are determined mainly by host identity or by parameters of the abiotic environment. Using data from 42 host species from 26 distinct regions, we found that mite abundances on different populations of the same host species were more similar to each other than expected by chance, and varied significantly among host species, with half of the variance among samples explained by differences between host species. A similar but less pronounced pattern was observed for mite diversity, measured both as species richness and as the taxonomic distinctness of mite species within an assemblage. Strong environmental effects were also observed, with local temperature and precipitation correlating with mite abundance and species richness, respectively, across populations of the same host species, for many of the host species examined. These results are compared to those obtained for other groups of parasites, notably fleas, and discussed in light of attempts to find general rules governing the geographical variation in the abundance and diversity of parasite assemblages.

We examine the evolution of microparasites in response to the immune system of vertebrate hosts. We first describe a simple model for an acute infection. This model suggests that the within-host dynamics of the microparasite will be a ‘race’ between parasite multiplication and a clonally expanding response by the host immune system, resulting either in immune-mediated clearance or host death. In this very simple model, in which there is only a single parasite and host genotype, maximum transmission is obtained by parasites with intermediate rates of growth (and virulence). We examine how these predictions depend on key assumptions about the parasite and the host, and consider how this model may be expanded to incorporate the effect of additional complexities such as host–parasite co-evolution, host polymorphism, and multiple infections.

Host immune responses have been shown to enhance the efficacy of several schistosomicidal drugs. The evidence derives mainly from experiments on Schistosoma mansoni infections in the mouse with their immune status variously modulated; this review emphasises praziquantel (PZQ), which is now the main drug used for treatment of human schistosomiasis. Electron microscopy and indirect immunofluorescence indicate that PZQ disrupts the integrity of the surface membranes of S. mansoni, particularly those covering the dorsal tubercles of adult male worms, and this causes antigens which are the targets of antibody attack to be revealed. We review the evidence that two S. mansoni antigens in particular are implicated in the immune-dependent action of PZQ: a 200 kDa glycoprotein and a 27 kDa antigen with non-specific esterase activity.

The aim of this study was to investigate the effects of grazing different bioactive forages on acquired immunity against Teladorsagia circumcinta infection. The development of immunity was assessed by following the response of trickle-infected lambs grazing chicory (Cichorium intybus; IC), sulla (Hedysarum coronarium; IS) or grass/clover (Lolium perenne/Trifolium repens; IGC), to a single challenge infection. Parasite-naive lambs, grazing grass/clover, were also challenged with the single infection dose providing the uninfected control (UGC) group. Trickle infection significantly reduced worm establishment, inhibited larval development and increased mucosal mast cell (MMC) and globule leucocyte (GL) cells. Grazing treatment (chicory, sulla or grass/clover) significantly affected adult worm (P<0·05), late-L4 (P<0·01) and mid-L4 (P<0·01) larval-stage recoveries of the trickle-infected lambs, with IGC group always carrying higher worm burdens than either IC or IS lambs. MMC and GL cells of trickle-infected lambs were positively correlated with the proportion of early-L4 worms recovered and negatively correlated with both the proportion of adult worms recovered and the total worm establishment, suggesting that the observed effects were due to an enhanced immune response. The results suggest elevated immune responses against T. circumcincta infections in growing lambs grazing on either sulla or chicory compared to those grazing on grass/clover, probably due to differences in forage nutritional values.

Little is known regarding the diversity, distribution or host-parasite associations of Trypanosoma spp. in Australian wildlife. Here we report on an investigation based on divergence of the 18S rRNA gene of trypanosomes isolated from a range of hosts and varied geographical locations. A total of 371 individuals representing 19 species of native animals from 14 different locations were screened. In total, 32 individuals from 9 different species tested positive for the parasite. Phylogenetic analysis revealed considerable parasite diversity with no clear geographical distribution and no evidence of host specificity. In general, it appears that Australian Trypanosoma spp. are widespread, with several genotypes appearing in multiple host species and in varied locations including both mainland areas and offshore islands. Some host species were found to be susceptible to multiple genotypes, but no individuals were infected with more than a single isolate.