Chagas' disease, caused by Trypanosoma cruzi, affects approximately 20 million people. There are 3 stages in the disease: acute, intermediate and chronic, the diversity and severity of the symptoms range from a mild electrocardiographic alteration to sudden death. We have previously demonstrated that when reinfections were carried out in the acute phase they produce greater cardiac damage. The aim of the present work was to investigate whether T. cruzi reinfected mice present electrocardiographic abnormalities that could be characteristic and only achieved after reinfections. Of the mice reinfected during the acute phase 100% showed abnormalities from days 90 post-infection, with a predominance of auricle ventricle blocks (67–71%). All the mice reinfected during the chronic infection showed electrocardiographic alteration after 30 days post-first reinfection. Of the mice infected, without reinfection, 60% exhibited electrocardiographic dysfunction at 90 days post-infection. Our results demonstrated that when the host was reinfected in the acute phase, more serious electrocardiographic alterations were developed than when the reinfections were carried out in the chronic stage. Sudden death described in some chagasic patients, might be related to some of the findings described here.

Leishmaniasis is considered a parasitic disease that still causes serious consequences for mankind, because it presents a high mortality rate worldwide. Considered multi-hosts, the parasites of the genus Leishmania are able of infecting a wide variety of animal species. The dog was considered the main source of infection of visceral leishmaniasis (VL), in the urban area. However, the role of other animal species in the epidemiological cycle of the disease, such as cattle, remains unclear. Therefore, the aim of the present study was to evaluate the occurrence of Leishmania spp. in 100 bovines (Bos taurus) from an area endemic for canine VL, using blood culture and molecular analysis. By the sequencing analysis, one sample showed 100% similarity with Leishmania infantum. The results provide the first case of L. infantum isolation in one bovine from the periurban areas of Bauru, state of São Paulo, Brazil.

A characteristic structural feature of Toxoplasma gondii and Neospora caninum is the presence of a triple-membrane pellicle, on the zoite stages of their complex life-cycle. Here we report the results of electron microscopic studies which show that the pellicle is made of a typical plasmalemma covered on its cytoplasmic side by a system of flattened vesicles named the inner membrane complex. Using methods described previously for the purification of pellicle and plasmalemma fractions from T. gondii, we have evaluated the same methodology for the preparation of pellicles and plasmalemma from N. caninum. The approach used involved subcellular fractionation and sucrose gradient centrifugation to prepare fractions containing pellicles. Plasmalemma was prepared by extraction of this fraction with a high salt glycerol treatment. Fractions containing membrane structures were identified by electron microscopy, and the proteins and antigens present in them were subsequently studied by SDS-PAGE and Western blotting. Electron microscopy of the pellicle fractions of N. caninum demonstrated preservation of the triple-membrane structure which is identical to that found in T. gondii. SDS-PAGE of the pellicle fractions revealed it contained several major proteins. Analyses revealed that the plasmalemma of N. caninum contained 2 abundant proteins in addition to other much lower abundance antigens detectable by monoclonal antibodies. These studies therefore report, for the first time, a detailed molecular characterization of the pellicle and plasmalemma of N. caninum.

Despite treatment with praziquantel (PZQ) at 40 mg/kg in food, several chimpanzees on Ngamba Island Chimpanzee Sanctuary (NICS) continue to excrete eggs of Schistosoma mansoni. To monitor disease, 8 animals were closely examined under anaesthesia in March 2011 with portable ultrasonography and by rectal snip biopsy. Schistosome genetic diversity had been previously assayed within 4 of these chimpanzees, finding extensive diversity with 27 DNA barcodes encountered, although none was common to all animals. Calcified schistosome eggs were found in the rectal snips from 5 chimpanzees and liver fibrosis was clearly documented, indicative of progressive disease in 6 animals, the latter being surprisingly advanced in a younger chimpanzee. All 8 animals were treated under anaesthesia by oral gavage with PZQ at 60 mg/kg dosing that was well tolerated. These animals were again re-examined in June 2012 using stool and urine sampling. Only 1 chimpanzee appeared to be free from infection and active egg excretion was confirmed in 6 animals. If intestinal schistosomiasis is to be controlled within this setting, a long-term disease management plan is required which should combine active case-detection with an insistent treatment regime with praziquantel for these chimpanzees, exploring perhaps the performance of even higher dosing.

Parasitic castration is a strategy used by parasites to minimize damage to the host by consuming its reproductive system, which results in the morphological alteration of the host. We determined that the forewing shape and density of the antennal sensilla of field-collected adult male mantids (Hierodula formosana), infected by horsehair worms (Chordodes formosanus) was partially feminized (intersexuality), and both male and female mantids infected by horsehair worms exhibited allometric changes in their wings and walking legs. In addition, the testes of most infected male adults disappeared or reduced in size, whereas the number of ovarioles in infected female adults was unaffected. The infection mainly influenced the structures related to host reproduction and locomotion, suggesting unbalanced energy exploitation and the reduction of parasitic virulence. In addition, the intersexuality of infected male adults indicated that sexual differentiation in insects, which researchers have considered to be an autonomous process, was influenced by the infection. The similarity of the antennae of infected male adults with those of last-instar female nymphs suggested that parasitic juvenilization may cause such feminization, but the mechanism of parasitic influence on insect sex characteristics should be studied further.

Populations of generalist species often comprise of smaller sub-sets of relatively specialized individuals whose niches comprise small sub-sets of the overall population niche. Here, the role of parasite infections in trophic niche specialization was tested using five wild fish populations infected with the non-native parasite Ergasilus briani, a copepod parasite with a direct lifecycle that infects the gill tissues of fish hosts. Infected and uninfected fishes were sampled from the same habitats during sampling events. Prevalence in the host populations ranged between 16 and 67%, with parasite abundances of up to 66 parasites per fish. Although pathological impacts included hyperplasia and localized haemorrhaging of gill tissues, there were no significant differences in the length, weight and condition of infected and uninfected fishes. Stable isotope analyses (δ13C, δ15N) revealed that the trophic niche of infected fishes, measured as standard ellipse area (i.e. the isotopic niche), was consistently and significantly smaller compared with uninfected conspecifics. These niches of infected fishes always sat within that of uninfected fish, suggesting trophic specialization in hosts. These results suggested trophic specialization is a potentially important non-lethal consequence of parasite infection that results from impaired functional traits of the host.

Paramphistomosis, caused by Calicophoron daubneyi, is an emerging infection of ruminants throughout Western Europe. Despite its prevalence, many questions remain regarding the basic biology of this parasite and how it interacts with its host. Consequently, there is a need to develop methods to study C. daubneyi in vitro to improve our understanding of rumen fluke biology. Towards this, we aimed to identify a suitable protocol for in vitro excystment of C. daubneyi metacercariae. Six methods that have been used to excyst metacercariae from a number of trematode species were tested with C. daubneyi metacercariae. Three of these achieved an average of >50% excystment whilst one method, which included an acid-pepsin treatment, incubation in reducing conditions and an alkaline/bile salt solution to activate the larvae, consistently gave >80% excystment. The latter protocol also showed no detrimental effect on the motility of newly excysted juvenile (NEJ) parasites when observed for up to 24 h in RPMI 1640 medium post-excystment. The successful production of C. daubneyi NEJs in vitro is a significant step forward, and will enable the discovery of infective stage-specific parasite antigens and facilitate drug screening trials, to aid the development of much needed diagnostic and therapeutic options for paramphistomosis.

Ascarid parasites infect a variety of hosts and regular anthelmintic treatment is recommended for all species. Parascaris spp. is the only ascarid species with widespread anthelmintic resistance, which allows for the study of resistance mechanisms. The purpose of this study was to establish an in vitro drug exposure protocol for adult anthelmintic-naïve Parascaris spp. and report a preliminary transcriptomic analysis in response to drug exposure. Live worms were harvested from foal necropsies and maintained in RPMI-1640 at 37 °C. Serial dilutions of oxibendazole (OBZ) and ivermectin (IVM) were prepared for in vitro drug exposure, and worm viability was monitored over time. In a second drug trial, worms were used for transcriptomic analysis. The final drug concentrations employed were OBZ at 40.1 μm (10 μg mL−1) and IVM at 1.1 μm (1 μg mL−1) for 24 and 3 h, respectively. The RNA-seq analysis revealed numerous differentially expressed genes, with some being potentially related to drug detoxification and regulatory mechanisms. This report provides a method for in vitro drug exposure and the phenotypic responses for Parascaris spp., which could be extrapolated to other ascarid parasites. Finally, it also provides preliminary transcriptomic data following drug exposure as a reference point for future studies of Parascaris spp.

The equilibrium, of vulvar phenotypes in Haemonchus contortus cayugensis was changed by infecting lambs with either a selected strain of smooth or of linguiform worms. Subsequently the lambs grazed the same pasture and observations were made on changes in worm populations in the lambs, and on pasture it appeared that the seasonal change in the relative frequencies of A and B linguiform worms was related to density-dependent factors in the host. In the spring, when lambs first become infected, the worm population is small and the majority of linguiform worms are A-type. As the season progresses the density of the parasite population increases. Once the population becomes crowded selection begins to favour the B-type females. The effects of crowding on linguiform A females can be seen as a positive correlation between the percentage of linguiform A and their weight. Population density also affected the survival of A-type worms since there was a negative correlation of percentage A-type on total worm numbers. There was a similar negative correlation between percentage A-type and total worm numbers in both the continuously infected and tracer lambs.

Population density did not affect the proportion of smooth worms. However, smooth worms increased in the tracers from, approximately 10% at the beginning of the experiment to 55% at its conclusion 18 weeks later. The latter percentage is almost within range of the local subspecies, which has 60% or more smooth worms. It appears therefore that the proportion of smooth to linguiform worms is a stable equilibrium maintained by natural selection.

Echinoparyphium hydromyos sp.nov. with forty-five collar spines is described from the Australian water rat, Hydromys chrysogaster Geoffr.

The cercaria occurs naturally in Plananisus isingi (Cotton & Godfrey), and all stages in the life-history have been demonstrated experimentally.

Encystation occurs in the kidneys of tadpoles.

The adult is most closely related to Echinoparyphium recurvatum (Linstow). It differs from this in its greater number of eggs and in its life-history. E. recurvatum occurs predominantly in birds, and is rarely found naturally in mammals. E. hydromyos has been found only in a mammal.

Cercaria echinoparyphii hydromyos is compared with C. clelandae Johnston and Angel; it differs from the latter in the ‘compound’ nature of the excretory granules. The adult of C. clelandae has not been demonstrated in spite of a number of experiments to determine it.

Type material has been deposited in the South Australian Museum.

I wish to acknowledge the help given by my colleague, Patricia M. Thomas, in field work and in other ways, and by Mr Ian Smith, of this department, in the experimental work on life-history studies.

Plasma etching has been used to strip away the cortical layers of the cuticle of adult Nippostrongylus brasiliensis to reveal the struts, with their supporting fibres, which are found in the fluid-filled middle layer of the cuticle, and the basal fibre layers. The etched specimens were studied by means of scanning electron microscopy. The results support earlier work, obtained by transmission electron microscopy, on the cuticle of this nematode. Plasma etching has been shown to have potential in studying the structure of nematodes.

1. No resistance to paludrine or to sulphadiazine was obtained after treating latent infections of Plasmodium gallinaceum in chickens with twice daily doses of 20 mg./20 g. of sulphadiazine over periods of 171, 178 and 190 days.

2. No resistance to paludrine was obtained after treating a latent infection of P. relictum in a canary over a period of 1 year with doses of paludrine increasing from 0·05 mg./20 g. once daily to 1·0 mg./ 20 g. twice daily.

3. It is considered that if drug-resistance arises by mutation and selection, then resistance should arise more readily when a large number of rapidly multiplying parasites is treated with a drug than when the population treated is small, with a low reproduction rate, i.e. the failure to obtain resistant strains of malaria by prolonged treatment of latent infections with large amounts of drug, lends support to the theory of the origin of resistant strains of malaria by the selection of resistant mutants.

During its life-cycle, the cestode Schistocephalus solidus is parasitic in both an ectotherm (Gasterosteus aculeatus) and an endotherm (Gallus domesticus) host, and so provides an excellent model with which to study temperature adaptation in parasites. A mitochondrial fraction was prepared from the adults and plerocercoids of S. solidus and from their respective hosts; the activities of the mitochondrial adenosine triphosphatase (ATPase) were then measured over the temperature range 1–45 °C. The plerocercoids of S. solidus show evidence of immediate temperature compensation; this would provide a mechanism for withstanding the abrupt temperature change experienced during infection of the final host. Analysis of the Michaelis constant data suggests that variation of Km, a with temperature may be a major factor in this immediate temperature compensation. In response to acclimation at 5 and 19°C, plerocercoid ATPase showed inverse or paradoxical rate compensation, as did the enzyme from the fish host. Acclimation at the two temperatures had no effect on the Q10 or on the linearity of the Arrhenius plots for the plerocercoid mitochondrial ATPase and only a small effect on the Km a. Acclimation of the fish host again had only a small effect on the Km, a of the fish mitochondrial ATPase but, in contrast to the plerocercoid, there was also a significant effect on the Q10 and the Arrhenius plots. Adult S. solidus ATPase showed partial rate compensation and had a biphasic Arrhenius plot, suggesting that after infection there had been a change in the enzyme or its micro-environment. In terms of the effect of temperature on the Q10 amd Km, a and in the biphasic nature of the Arrhenius plot, the mitochondrial ATPase of adult S. solidus showed similarities with the enzyme from its bird host.

Pathogens are increasingly implicated in amphibian declines but less is known about parasites and the role they play. We focused on a genus of nematodes (Rhabdias) that is widespread in amphibians and examined their genetic diversity, abundance (prevalence and intensity), and impact in a common toad (Rhinella horribilis) in Panama. Our molecular data show that toads were infected by at least four lineages of Rhabdias, most likely Rhabdias pseudosphaerocephala, and multiple lineages were present in the same geographic locality, the same host and even the same lung. Mean prevalence of infection per site was 63% and mean intensity of infection was 31 worms. There was a significant effect of host size on infection status in the wild: larger toads were more likely to be infected than were smaller conspecifics. Our experimental infections showed that toadlets that were penetrated by many infective Rhabdias larvae grew less than those who were penetrated by few larvae. Exposure to Rhabdias reduced toadlet locomotor performance (both sustained speed and endurance) but did not influence toadlet survival. The effects of Rhabdias infection on their host appear to be primarily sublethal, however, dose-dependent reduction in growth and an overall impaired locomotor performance still represents a significant reduction in host fitness.

This study furthers understanding of cestode infections in a marine environment through time and space by following seasonal fluctuations in infection parameters of three cestode species (Gilquinia squali, Trilocularia gracilis and Phyllobothrium squali) parasitizing spiny dogfish (Squalus acanthias) in the northwest Atlantic and comparing them to work previously published from the northeast Atlantic on T. gracilis. For each cestode species, host size, season and presence of the other cestode species were analysed using generalized linear models to determine if they were good predictors of prevalence and intensity. Infection parameters differed across season for the three cestode species. However, within T. gracilis seasonal trends were found to be remarkably similar on both sides of the Atlantic, differing only in a somewhat delayed decline in prevalence in the northwest Atlantic. The differences seen in infection measures across cestode species likely reflect the unique life history strategies of different parasite species. While general trends appear to be maintained across disparate localities, variation seen is likely due to differences in accessibility to intermediate hosts and host diet across sites. The knowledge gained from understanding cestode infections in the vast ocean environment allows us to speculate about the factors driving fluctuations in parasite infections in elasmobranchs.

Two new species are described from New Guinea pythons, i.e. Ophidascaris niuginiensis and O. papuanus. The former was from Chondropython viridis and Liasis albertisi, the latter from L. amethistinus. Development of O. niuginiensis in mice involved a primary stage in the liver, a secondary stage in the mesenteric blood vessels and a tertiary stage in the skin, where growth occurred to a length of 50 mm or more. Initial growth, up to 10 mm, of O. papuanus occurred in the liver and body cavity of mice; a secondary growth phase occurred in the body cavity of the python host.

During the course of a primary infection of Nippostrongylus brasiliensis in protein-malnourished rats, plasma concentrations of corticosterone were found to decrease from 0.89±0.03 at the start of the infection to 0.28±0.08μmol/l, 9 days post-infection (p.i.). Similarly, adreno-corticotrophic hormone levels were also observed to fall from 62.09±12.06 to 20.54±1.81 by 5 days p.i. and to 35.12±16.61 nmol/l by 9 days p.i. However, no significant changes were seen in the dry weight of the adrenal glands other than those expected in relation to changes in body weight. Concentrations of both plasma tri-iodothyronine and thyroxine were also severely depleted over the same period from 5.33±0.34 to 1.09±0.42 and 104.43±10.4 to 34.12±8.95 nmol/l respectively. This was considered not to be due to any change in the capacity of the plasma to bind these hormones. Results for insulin were highly variable, but overall were lower from protein-malnourished rats than results documented for well-nourished rats and a reduction from 18.07±3.17 to 6.08±2.18μunits/ml, 9 days p.i. was observed. The results are discussed in relation to the role of these hormones in protein metabolism in a protein-malnourished animal.