Mice which have recovered from infections with the avirulent piroplasm Babesia microti are also resistant to challenge with the virulent malaria parasite Plasmodium vinckei. In mice infected with P. vinckei before the peak of the B. microti infection the numbers of malaria parasites in the blood increase until that peak and are then eliminated at the same time as the piroplasms. In mice infected with P. vinckei at or after the peak there is no apparent multiplication and the malaria parasites begin to disappear from the blood immediately. The malaria parasites in doubly infected mice show signs of degeneration similar to those seen in mice pre-treated with Corynebacterium parvum and it is suggested that a common mechanism exists in homologous and heterologous immunity and in immunity following pre-treatment with C. parvum or BCG.

A number of common freshwater molluscs were exposed to Fasciola hepatica miracidia labelled in vivo with radioselenium. Radioactivity was rapidly incorporated in all lymnaeid species tested (L. auricularia, L. columella, L. glabra, L. natalensis, L. palustris, L. pereger, L. stagnalis, L. tomentosa and L. truncatula) whereas no radioactivity could be demonstrated in non-lymnaeid pulmonate species (Aplexa hypnorum, Physa acuta, Physafontinalis, Anisus vortex, Gyraulus albus and Planorbis planorbis) or in the prosobranchs Valvata cristata and Valvata piscinalis. However, the prosobranchs Bithynia leachii, Bithynia tentaculata and Potamopyrgus jenkinsi showed a slow but significant uptake of radioactivity which was presumably explained by uptake of labelled miracidia through a ‘filter-feeding] mechanism. Sphaerium corneum, a true filter-feeder, showed a similar course of uptake of radioactivity.

Eighty-seven of 175 laboratory raised F1 generation brook charr (Salvelinus fontinalis) were resistant to experimental Cryptobia salmositica infection. Susceptibility to the pathogen was not related to age nor to route of infection. Plasma of resistant charr lysed the parasite under in vitro conditions while those of susceptible fish did not. Sperm from 4 susceptible and 4 resistant male charr, from 8 F1 families, were used to fertilize eggs from 2 hatchery raised susceptible charr. Susceptibility of progenies (F2 families) was determined 4 weeks after inoculation of the parasite. All progenies (seven F2 families) of 4 susceptible males were susceptible to experimental infection and their plasma did not lyse the parasite. It was presumed that these susceptible progenies were homozygous recessive (rr), and that the resistant allele was dominant. All progenies (two F2 families) of 1 resistant male (presumed RR) and 2 susceptible females were all resistant to infection and their plasma lysed the parasite. The ratio of resistant to susceptible charr in 6 other F2 families from the other 3 resistant males (presumed Rr) and two susceptible females was about 1:1. The results suggest a single Mendelian locus which determines innate resistance to C. salmositica infection in brook charr and that it is possible to breed Cryptobia-resistant fish.

A morphological study of the fine structure of the spores of Minchinia chitonis, a haplosporidian parasite of the chiton, Lepidochitona cinereus, is described. The spores contained a single nucleus, mitochondria, haplosporosomes, smooth endoplasmic reticulum, ribosomes and a large spherule (presumed Golgi apparatus). The spore wall was discontinuous at the spherule end, forming an opening covered by a lid which rested on a circumscribed flange. The flange of the spore wall and the lid were continuous in only one area which served as a hinge. The entire spore was encapsulated by epispore cytoplasm bounded by a strengthened membrane and extended to form 2 long projections, one at either end.

A consideration of the tick-activity data for South Wales reveals that there are usually two peaks of female activity in this region, one occurring in spring, the other in autumn. On an experimental area, divided into eight plots, on the Margam Moors, Glamorgan, significantly varying population levels are present on the different plots, although the peak of activity on all of them is attained around the same period. The seasonal activity of the nymphal and larval forms in South Wales is essentially comparable to that recorded by Milne (1945a) in the north of England. There is reason to believe that in mid-Wales a single summer peak of tick activity exists.

The engorgement period of female ticks on cattle varies from 7 to 13 days. The tick shows a distinct preference for the hind region of cattle for feeding purposes. The differences in the mean populations of ticks on different breeds of cattle are not statistically significant, at least, on the six breeds tested in 1944 and 1945. In the case of cattle, tick density and fecundity of the female are not correlated with the physiological condition of the host.

In South Wales, the populations of ticks on sheep are significantly lower than those on cattle, even where both hosts are pastured on the same ground for similar periods. The seasonal activity of female ticks on horses follows the same general trend as that noted on cattle.

Considerable diversity has been found in the reproductive behaviour of benedeniine (capsalid) monogenean parasites. Mating has been observed in Benedenia sp. 1 from the gills of Lutjanus carponatatus; externally attached spermatophores are not involved and parasites indulge in mutual cross-insemination with intromission. In contrast, there is evidence of spermatophore involvement in Benedenia sp. 2 from the fins of Lethrinus miniatus; mating was not observed but an individual was found carrying an external ovoid spermatophore attached by a stalk lodged in the vagina. In specimens of Benedeniella macrocolpa and B. posterocolpa, in which the male reproductive system was functional and the female system not fully developed, the everted cirrus was seen to be lodged in the parasite's own uterus, with, in some individuals, the tip of the cirrus inside the ootype. This is the first time that the copulatory organ has been observed inside the female reproductive tract of the same individual, not just in benedeniines but in monogeneans in general, and is also the first demonstration that monogeneans are capable of self-insemination via the uterine route.

A pleomorphic neoplasm (PN) is described from sections of Onchocerca volvulus worms in nodules excised from Cameroonian patients. PN is confined to older, non-fecund, female worms, and those classed as moribund/dead. It is mainly composed of small, roundish, basophilic cells of diverse sizes, often forming a ‘rosette’ pattern around amorphous eosinophilic centres. The cells have a high nuclear/cytoplasmic ratio and up to 2–3 mitoses/high-power field; some become grossly enlarged, highly polymorphic and contain large, irregular blocks of chromatin. The eukaryotic PN cells first appear posteriorly in the pseudocoelom, probably from ovarian cells; they spread anteriorly, invading or compressing the uteri. Ivermectin treatment increased the prevalence PN from 3.7% of 1422 female worms in 637 patients before treatment to 17.5% of 1134 worms in 511 patients after 3 years treatment. Ivermectin at 400–800 μg/kg annually, or at 150 μg/kg or 400–800 μg/kg 3-monthly, over 3 years, did not increase the PN prevalence significantly, as compared with standard doses of 150 μg/kg annually. In other small series of African patients, PN prevalence increased in worms 2, 4, 6 and 10 months after ivermectin treatment; but there was no increase after treatment with amocarzine, albendazole or diethylcarbamazine and suramin. PN may partly account for the increased macrofilaricidal action of ivermectin on female O. volvulus in patients treated for 3 years at 3-monthly intervals.

There is increasing support for the presence of viruses and virus-like particles inside protozoan cells. This study describes viral-like RNA molecules that have been detected in two species of Eimeria that infect the chicken. The RNA molecule identified in E. maxima has been characterized: subcellular fractionation studies have shown that the RNA is present in the cytoplasm, probably as an abundant ribonucleoprotein that is insensitive to RNAse A treatment. Electron microscopy has demonstrated that this RNA molecule is double stranded. In addition, all E. maxima strains examined so far contain this RNA molecule.

Various treatments are found to be moderately effective in managing Demodex-related diseases except tea tree oil (TTO) and terpinen-4-ol (T4O), which showed superior miticidal and anti-inflammatory effects in numerous clinical studies. Their possible effects include lowering mite counts, relieving Demodex-related symptoms, and modulating the immune system. This review summarizes the current clinical topical and oral treatments in human demodicosis, their possible mechanisms of action, side-effects and resistance in treating this condition. TTO (especially T4O) is found to be the most effective followed by metronidazole, ivermectin and permethrin in managing the disease. This is because TTO has anti-parasitic, anti-bacterial, anti-fungal, anti-inflammatory and wound-healing effects. Furthermore, nanoTTO can even release its contents into fungus and Pseudomonas biofilms. Combinations of different treatments are occasionally needed for refractory cases, especially for individuals with underlying genetic predisposal or are immuno-compromised. Although the current treatments show efficacy in controlling the Demodex mite population and the related symptoms, further research needs to be focused on the efficacy and drug delivery technology in order to develop alternative treatments with better side-effects profiles, less toxicity, lower risk of resistance and are more cost-effective.

Leishmania parasites are able to survive in the macrophage, one of the most hostile environments of the vertebrate host. The present study investigated how Leishmania infection influences these host cell defence mechanisms. Macrophages were infected with antimony-susceptible and -resistant Leishmania strains. Free radical production in Leishmania-infected macrophages was measured by electron paramagnetic resonance. Apoptosis was detected with fluorescence microscopy using Annexin-V FITC labelling and with Western blotting to detect caspase-3 cleavage. Independent of their drug susceptibility profile or species background, all studied Leishmania strains induced a similar increase in free radical production in macrophages. O2●− production was significantly elevated during phagocytosis of the stationary phase promastigotes. Conversely, NO levels increased later in the infection and none of the strains induced capsase-3 cleavage. Leishmania donovani infection led to phosphatidylserine externalization only in RAW 264.7 cells. After an initial burst of O2●− during phagocytosis of promastigotes, amastigotes protect themselves by decreasing the O2●− production to the basal level. An increased NO production was observed 6 h after infection. Finally, induction of cell death is probably not essential in the survival of the parasite within the macrophage.

Cysts of Blastocystis ratti were produced in vitro by culturing the parasite in Iscove's modified Dulbecco's medium (IMDM) with increasing concentrations of horse serum. Yields up to 3×106 cysts/ml of culture medium were obtained after 72 h. Encystation efficiency was time, strain and inoculum size dependent. A viability of >70% was determined by flow cytometry employing fluorescein diacetate and propidium iodide staining. The presence of chitin as a cyst wall component was demonstrated by Calcofluor White M2R staining with which cystic stages showed blue fluorescence. The changes in morphology during excystation were examined by transmission electron microscopy. The cyst enlarged in size and some vacuoles appeared within the condensed cytoplasm. The vacuoles were full of inclusions and small glycogen aggregates. Coalescence of the vacuoles led to central body formation. Glycogen deposits were prominent throughout the excystation process. Some cysts divided by binary fission before the completion of the excystation.

Allelic variation in 6 microsatellite markers was compared between frozen Schistosoma mansoni eggs and laboratory-passaged worms originating from the same 5 fecal samples obtained from Brazilian residents. Based on allelic richness values, the number of alleles detected per locus did not differ between egg and worm DNA templates. However, our ability to score loci differed between these DNA templates, with worms providing more scored loci per individual than eggs. Differences also existed between the worms and eggs in the identity of the specific alleles that were detected. Additionally, we observed a reduction in homozygous genotypes among laboratory-passaged worms relative to the eggs. Allelic diversity curves were calculated by genotyping all worms from a representative host sample to determine the relationship between the number of alleles detected at a locus and the number of worms genotyped. Curves for the 5 residents' worm infrapopulations for each of the loci were very similar. The equation y=19·55×ln(x)+9·992 explained the association between sampling effort (x) and number of alleles detected (y) with an R2 of 0·775. In conclusion, egg DNA templates and allelic diversity curves can benefit efforts to discern the sociological, ecological and evolutionary forces impacting the genetic diversity and disease epidemiology of human schistosomes.

Due to the low informative value of available morphological characters, cytogenetic and molecular methods, based on rDNA sequencing, were used to characterize adult and larval stages of Phyllodistomum spp. Species studied have 18 chromosomes with comparable absolute and relative lengths. Conventional Giemsa staining and karyometric analysis revealed clear differences in chromosome morphology of larval Phyllodistomum spp. infecting two bivalve host species, Sphaerium corneum and Pisidium amnicum. However, karyotypes of adult P. folium from three-spined sticklebacks and larval stages from S. corneum appear almost identical both with respect to the relative lengths and centromeric indices of the corresponding chromosome pairs. The entire internal transcribed spacer (ITS) region (ITS-1, 5.8S and ITS-2) and the D1-D3 region of 28S gene were sequenced and compared. Again, sufficient differences were observed between larval Phyllodistomum spp., while adult P. folium and larvae from S. corneum showed a high level of similarity. So, both cytogenetic and molecular data support the suggestion that they represent developmental stages of the same species. The results were compared with published data obtained by cytogenetic and molecular studies on the other Phyllodistomum species. Differences revealed in karyotype and rDNA sequences leads to the conclusion that the cercariaeum of P. folium sensu Sinitsin, 1905 could not be regarded as the larva of adult P. folium from three-spined stickleback.

We suggest a new mechanism for the maintenance of specificity of the association between the entomopathogenic nematode Steinernema scapterisci and its symbiotic bacteria. We evaluated the development and reproduction of infective and non-infective juvenile S. scapterisci in monoxenic combinations with its symbiotic bacteria, Xenorhabdus sp. ‘S’ and with the bacterial symbiont of Steinernema carpocapsae and Steinernema riobravis. Although development of non-infective stages occurred on all Xenorhabdus spp., the development of infective juveniles to the 4th stage (‘dauer’ recovery) was significantly delayed and reduced with X. nematophilus and Xenorhabdus sp. ‘R’, the bacterial symbionts of S. carpocapsae and S. riobravis, respectively. ‘Dauer’ recovery improved significantly when the cultures of X. nematophilus and Xenorhabdus sp. ‘R’ were supplemented with cell-free filtrates from Xenorhabdus sp. ‘S’. The infective juvenile S. scapterisci produced in all 3 cultures were virulent to Galleria mellonella larvae, confirming successful retention of Xenorhabdus from other steinernematids in their intestine. In fact, S. scapterisci infective juveniles containing X. nematophilus or Xenorhabdus sp. ‘R’ were more virulent to G. mellonella than those containing their natural symbiont, Xenorhabdus sp. ‘S’. We believe that this is the first demonstration of the symbiont-specific exit of infective juveniles from the ‘dauer’ phase which represents the finest level of specificity of bacteria–nematode association. This is also the first report of successful isolation of the natural symbiont of S. scapterisci.

This study was conducted to investigate the level of cardiac and oxidative stress markers in camels infected with Trypanosoma evansi and to explore the diagnostic and prognostic value of cardiac troponin I (cTnI) and creatine kinase-myocardial band (CK-MB) in response to infection. Seventy four dromedary camels with clinical and laboratory evidence of trypanosomosis and 20 healthy controls were included in this study. Serum cTnI, CK-MB, CK, malondialdehyde (MDA) and super oxide dismutase (SOD) were measured. The values of cTnI, CK-MB, CK and MDA were significantly higher, whereas SOD level was lower in T. evansi infected camel. Successfully treated camels (n = 43) had lower levels of cTnI, CK-MB, CK and MDA, but higher level of SOD compared to camels with treatment failure. Both cTnI and CK-MB showed high degree of accuracy in predicting treatment outcome (success vs failure). The area under the curve for cTnI and CK-MB was 0·98 and 0·93, respectively. However, cTnI showed better sensitivity and specificity than CK-MB (Se = 96·8% vs 83·9% and Sp = 100% vs 88·5%, respectively). These results suggest that cTnI and CK-MB could be used as diagnostic and prognostic biomarkers in camels infected with T. evansi.

Clinical data on the use of artesunate combined with mefloquine in a variety of treatment regimens and parasite loads in Thailand were modelled on the basis of experimentally determined pharmacokinetic data. The model assumed no pharmacodynamic interaction between artesunate and mefloquine, but that the parasites were already resistant to mefloquine. Predictions of the model accorded well with the data. In particular, in accordance with clinical observations, the model showed that monotherapy with either drug failed to cure at moderate parasitaemia, yet such patients could be treated effectively with the combination of 3 days of artesunate + mefloquine. For high levels of parasitaemia, 5 days of artesunate+mefloquine were needed. Simulations were also performed for situations of lower resistance to mefloquine and for the immune human populations found in Africa. The importance of mathematical modelling of combination therapy is borne out by this study and suggests its wider application for other drug combinations.

Primers and DNA probes designed for use in the specific detection of the paramyxean parasites Marteilia sydneyi and Marteilia refringens were tested for their potential to cross-react with closely related species in Polymerase Chain Reaction (PCR) and in situ hybridization. PCR primers and a DNA probe designed within the ITS1 rRNA of M. sydneyi were specific for M. sydneyi when compared with related species of Marteilia and Marteilioides. PCR primers designed within the 18S rRNA of M. refringens were specific in the detection of this species in PCR while a DNA probe (named Smart 2) designed on the same gene cross-reacted with M. sydneyi in tissue sections of Saccostrea glomerata as well as Marteilioides sp. infecting Striostrea mytiloides. Though not species specific, the Smart 2 probe provided a stronger signal in detection of all stages of M. sydneyi than the ITS1 probe. The ITS probe is proposed for use as a confirmatory diagnostic tool for M. sydneyi.

Understanding how individual parasite traits contribute to overall fitness, and how they are modulated by both external and host environment, is crucial for predicting disease outcome. Fungal (chytrid) parasites of phytoplankton are important yet poorly studied pathogens with the potential to modulate the abundance and composition of phytoplankton communities and to drive their evolution. Here, we studied life-history traits of a chytrid parasite infecting the planktonic, bloom-forming cyanobacterium Planktothrix spp. under host genotype and thermal variation. When expressing parasite fitness in terms of transmission success, disease outcome was largely modulated by temperature alone. Yet, a closer examination of individual parasite traits linked to different infection phases, such as (i) the establishment of the infection (i.e. intensity of infection) and (ii) the exploitation of host resources (i.e. size of reproductive structures and propagules), revealed differential host genotype and temperature × host genotype modulation, respectively. This illustrates how parasite fitness results from the interplay of individual parasite traits that are differentially controlled by host and external environment, and stresses the importance of combining multiple traits to gain insights into underlying infection mechanisms.

This study examines polymorphisms in 2 genes (pfmdr1 and cg2), which have been associated with resistance to chloroquine in Plasmodium falciparum, to determine their value as predictors of resistance status. Among field samples from children in Zaria, northern Nigeria, the Tyr-86 polymorphism in pfmdr1 and Ala-281 and the Dd2κ repeat of cg2, were significantly associated. In 8 samples classified resistant by the micro-in vitro test, or, where this failed, by in vivo trial, 7 showed the cg2 Dd2 type κ repeat, and 6 of these had both the Ala-281 allele and the pfmdr1 Tyr-86 allele. In 26 chloroquine-sensitive samples, none had this combination of 3 polymorphisms (P = 0·00002). This indicates 75% sensitivity and 100% specificity in detection of resistance and shows a positive predictive value for resistant infections of 100%. The negative predictive value, because of sensitivity less than 100%, would depend on the prevalence of resistance. Where prevalence of resistance is approx. 21% as in Zaria, the negative predictive value would be 94%, while in Gabon, with a prevalence of ca 73% it would be 60%. The use of (cg2: Ala-281, Dd2κ. pfmdr1: Tyr-86) genotype detection as a predictive epidemiological tool to examine the distribution of chloroquine-resistance in parts of Africa is therefore possible. The sensitivity of detection of resistant strains still requires improvement.

Heliciculture is an excellent alternative to obtain edible snails but its viability is seriously threatened by pathogens. A parasitological survey was conducted in 3 mixed system-based heliciculture farms in Galicia (NW Spain), with the species Tetrahymena rostrata, Tetrahymena limacis, Tetratrichomonas limacis, Cryptobia helicogenae, Brachylaima aspersae (metacercariae and sporocysts), Alloionema appendiculatum, Nemhelix bakeri, and Riccardoella limacum being commonly found infecting Helix aspersa aspersa (petit-gris) snails. With the exception of C. helicogenae, N. bakeri, and B. aspersae sporocysts, all species were also detected in Helix aspersa maxima (gros-gris) snails, although generally with lower parameters. Most monoxenous infections, and consequently multiple parasitism, exhibited a rising trend during the first 2 months of intensive mating, with tendencies being slowed down or even reversed during the third month as a result of accumulated mortality and a sampling-derived reduction in host density. No parasites were vertically transmitted and infections were initially acquired from invading gastropod and micromammal reservoirs during fattening. Finally, artificial hibernation reduced significantly the prevalence of most species. These results confirm the importance of parasites in heliciculture and emphasize the need to prevent the entry of wild reservoirs into the farms and to rapidly remove the carcasses of dead snails from the reproduction units and fattening pens.