A comparison was made between 14-day-old populations of Nematodirus battus from single infections and from those which developed concurrently with Haemonchus contortus from the day of infection and from days 5 and 10 after infection. The numbers of Nematodirus fell with decreasing length of exposure to Haemonchus and were negatively correlated with the numbers of Haemonchus. The percentage of the populations of Nematodirus in the adult stage and the mean worm lengths fell with increasing length of development with Haemonchus, the lowest values being found in infections which developed concurrently with the abomasal worm for the full 14 days (days 0–14). Mean Nematodirus worm lengths were negatively related to abomasal pH and Na+ levels in populations which were concurrent with Haemonchus for the last 9 days (days 5–14) and for the full 14 days of development studied. Nematodirus egg capacity also fell with exposure to Haemonchus, but was lower in the worm populations exposed for the last 9 days than in those exposed for 14 days. Egg capacity was related to abomasal electrolyte levels in populations which had developed concurrently with Haemonchus for the last 9 days and for the full 14 days. Significant differences between the population parameters of Nematodirus from the proximal and middle third of the small intestine were only found in the single Nematodirus infections and in those which were concurrent with Haemonchus for the last 4 days (days 10–14). The differences in the populations of Nematodirus were related to the probable changes in alimentary conditions affected by the different periods of concurrent infections of Haemonchus. It was suggested that the alimentary changes may have caused the loss of adult Nematodirus and have influenced the growth, development and reproductive capacity of the intestinal worm by acting upon the fourthand fifth-stage larvae.

Experiments to study the effect of extrinsic factors on the copulation of normal adult Nippostrongylus brasiliensis are described.Worms copulated when in contact with the rat small intestine, whether it was ligatured, maintained inside or outside the peritoneal cavity, slit open or its lumen obstructed, provided that the blood supply remained intact and the temperature was within a few degrees of normal. Copulation did not occur in the colon, pleural cavity, peritoneal cavity, pregnant or non-pregnant uterus of the live rat or under a variety of in vitro conditions.These results indicate the importance of extrinsic factors for successful copulation since all the worms used in the experiments were intrinsically ready for immediate copulation in their normal environment.Worms observed during in vitro experiments were more vigorous and erratic in their movements than worms in their normal environment. The possible significance of this observation is discussed both in the context of in vitro reproduction experiments and in vitro experiments to study the physiology and biochemistry of the worm.

Antigens of three lines of the rodent malaria parasite Plasmodium yoelii have been studied using crossed immunoelectrophoresis. P. y. yoelii line A1 is a mild line which is restricted to reticulocytes. P. y. yoelii line YM and P. y. nigeriensis line D1 are virulent infections which multiply in both immature and mature erythrocytes. One antigen, designated Py-1, was found to differ in its electrophoretic mobility between the lines, being fast (F) in lines A1 and YM and slow (S) in line D1. Antigen Py-1 also varied in quantity among the three lines; greater amounts were detected in parasites inhabiting mature erythrocytes than in those in reticulocytes. These characters were stable during blood and mosquito passage.

The snail Bulinus nasutus 1214 possesses a potent haemagglutinin (end-point titre with human erythrocytes, 2−18) in its cell-free haemolymph which also binds to the miracidia (but not other larvae) of the incompatible parasite Schistosoma margrebowiei. We have purified a protein possessing this haemagglutinating property from the plasma of this snail. The native Mr of this protein was estimated by SDS polyacrylamide gel electrophoresis to be 210 kDa; under denaturing conditions in a 7.5% PAGE gel it ran as a major band of 135 kDa. Proteins of similar Mr were also found in the haemolymph of 16 other Bulinus spp. (the major intermediate hosts of human and veterinary schistosomiasis in Africa) although the plasma of none of these agglutinated human erythrocytes. Nonetheless, Cleveland mapping of the Mr 135 kDa bands from these different Bulinus spp. revealed 4 identical major peptide fragments (30, 28, 19 and 16 kDa) in each, thus demonstrating a similarity in the primary structure of these plasma proteins. Antisera from Balb/C mice immunized with the 135 kDa polypeptide from Bulinus truncatus 1521 cross-reacted in Western blots with the 135 kDa band of other members of the same truncatus/tropicus species complex but not with species from the africanus or forskalii species groups.

Many protease genes have previously been shown to be involved in parasitism and in the development of Steinernema carpocapsae, including a gene predicted to encode an aspartic protease, Sc-ASP110, which was cloned and was analysed in this study. A cDNA encoding Sc-ASP110 was cloned based on an expressed sequence tag (EST) fragment from our EST library. The full-length cDNA of Sc-ASP110 consists of 1112 nucleotides with a catalytic aspartic domain (aa18–337). The putative 341 amino acid residues have a calculated molecular mass of 37·1 kDa and a theoretical pI of 4·7. BLASTp analysis of the Sc-ASP110 amino acid sequence showed 45–77% amino acid sequence identity to parasitic and non-parasitic nematode aspartic proteases. An expression analysis showed that the sc-asp110 gene was upregulated during the late parasitic stage, L4, and 24 h after induction of in vitro nematodes. A sequence comparison revealed that Sc-ASP110 was a member of an aspartic protease family; additionally, a phylogenetic analysis indicated that Sc-ASP110 was clustered with the closely related nematode Steinernema feltiae. In situ hybridization showed that sc-asp110 was expressed in the body walls of dorsal cells. The upregulated Sc-ASP110 expression revealed that this protease could play a role in the late parasitic process. In this study, we have cloned and analysed the gene transcript of Sc-ASP110 in S. carpocapsae.

Previous work has highlighted increased opportunities for the transmission of Syngamus trachea within pheasant release pens, due in part to high levels of environmental contamination around communal areas. Despite this, the distribution of adult worms within their definitive hosts is not significantly different from predicted distributions under Taylor's power law. Therefore, density-dependent processes are probably acting to regulate S. trachea population dynamics. Patterns of nematode fecundity were investigated in a semi-naturally occurring population of ring-necked pheasants (Phasianus colchicus) and a wild population of carrion crows (Corvus carone). Worm length was a reliable indicator of nematode fecundity, and a negative association between mean worm length and mean worm burden was identified within both the species. The stunting of worms at greater parasite densities was present in both immunologically naïve and previously exposed pheasants, so is unlikely to be a function of age-dependent acquired immunity. Interestingly, the effect of parasite crowding in the crow population explained more of the variation in mean worm length, apparently driven by a greater mean worm burden when compared with pheasants. The findings of the present study suggest that fecundity is a function of parasite density, i.e. parasite-mediated competition and not host-mediated heterogeneities in immunocompetence.

The Trematode herein described was obtained from the gills of Trigla hirundo Day, popularly called the Yellow Gurnard, Latchet or Tub, one of the most common species of the Gurnard family found on the west coast of Ireland.

Numerous males and females collected from a Blue Duiker (Cephalophus (Guebei) monticola) at Ngome Forest, Mt Ngwibi, Natal, by Mr J. Tustin.

The foundation of an Institute for Research in Parasitology in Cambridge is an achievement worthy of being recorded in some detail since it affords a recognition of the value of a branch of biological science that cannot but gratify all who have gained an insight into the deep significance of the many problems which parasitology presents when viewed from the standpoint of pure science.

Environmental toxicants are pervasive in nature, but sub-lethal effects on non-target organisms and their parasites are often overlooked. Particularly, studies on terrestrial hosts and their parasites exposed to agricultural toxicants are lacking. Here, we studied the effect of sequence and timing of sub-lethal exposures of the pyrethroid insecticide alpha-cypermethrin on parasite establishment using the tapeworm Hymenolepis diminuta and its intermediate insect host Tenebrio molitor as a model system. We exposed T. molitor to alpha-cypermethrin (LD20) before and after experimental H. diminuta infection and measured the establishment success of larval tapeworms. Also, we conducted in vitro studies quantifying the direct effect of the insecticide on parasite viability. Our results showed that there was no direct lethal effect of alpha-cypermethrin on H. diminuta cysticercoids at relevant concentrations (LD10 to LD90 of the intermediate host). However, we observed a significantly increased establishment of H. diminuta in beetles exposed to alpha-cypermethrin (LD20) after parasite infection. In contrast, parasite establishment was significantly lower in beetles exposed to the insecticide before parasite infection. Thus, our results indicate that environmental toxicants potentially impact host-parasite interactions in terrestrial systems, but that the outcome is context-dependent by enhancing or reducing parasite establishment depending on timing and sequence of exposure.

Cell cycle progression is a question of fundamental biological interest. The coordinated duplication and segregation of all cellular structures and organelles is however an extremely complex process, and one which remains only partially understood even in the most intensively researched model organisms. Trypanosomes are in an unusual position in this respect – they are both outstanding model systems for fundamental questions in eukaryotic cell biology, and pathogens that are the causative agents of three of the neglected tropical diseases. As a failure to successfully complete cell division will be deleterious or lethal, analysis of the cell division cycle is of relevance both to basic biology and drug design efforts. Cell division cycle analysis is however experimentally challenging, as the analysis of phenotypes associated with it remains hypothesis-driven and therefore biased. Current methods of analysis are extremely labour-intensive, and cell synchronization remains difficult and unreliable. Consequently, there exists a need – both in basic and applied trypanosome biology – for a global, unbiased, standardized and high-throughput analysis of cell division cycle progression. In this review, the requirements – both practical and computational – for such a system are considered and compared with existing techniques for cell cycle analysis.

Infection experiments with Sarcoptes of cattle conducted upon a horse, two sheep, two rabbits, two rats, a cat and a man gave negative results. Active stages of the mite kept damp in the refrigerator lived 11 days, at room-temperature they lived 7 days, at 37° C. they lived 3 days, these being maximum periods observed. Eggs kept 5 days and over in the refrigerator subsequently failed to hatch when warmed; when kept at room-temperature they lived 16 days and hatched on being warmed; at 37°C. they survived 7 days.

Infection experiments with Psoroptes of cattle conducted upon one heifer gave negative results.

Chorioptes of cattle kept at room-temperature and protected from light survived 29 days.

Mathematical modelling provides an effective way to challenge conventional wisdom about parasite evolution and investigate why parasites ‘do what they do’ within the host. Models can reveal when intuition cannot explain observed patterns, when more complicated biology must be considered, and when experimental and statistical methods are likely to mislead. We describe how models of within-host infection dynamics can refine experimental design, and focus on the case study of malaria to highlight how integration between models and data can guide understanding of parasite fitness in three areas: (1) the adaptive significance of chronic infections; (2) the potential for tradeoffs between virulence and transmission; and (3) the implications of within-vector dynamics. We emphasize that models are often useful when they highlight unexpected patterns in parasite evolution, revealing instead why intuition yields the wrong answer and what combination of theory and data are needed to advance understanding.

Non-random assemblages have been described as a common pattern of flea co-occurrence across mainland host species. However, to date, patterns of flea co-occurrence on islands are unknown. The present work investigates, on one hand, whether the decrease in the number of species on islands affects the pattern of flea co-occurrence, and on the other hand, how the cost of higher flea burdens affects host body mass. The study was carried out in the Canary Islands (Spain) using null models to analyse flea co-occurrence on Rattus rattus and Mus musculus. Results supported aggregation of flea species in Mus but not in Rattus, probably due to the relationship between abundance and both prevalence and intensity of infection of the main flea species parasitizing Mus. In addition, heavy individuals of both rodent species showed the highest flea burdens as well as higher species richness, probably due to the continued accumulation of fleas throughout life and/or immunological resistance mechanisms. Whatever the mechanisms involved, it is clear that co-occurrence and high parasite intensities do not imply a detrimental biological cost for the rodents of the Canary Islands.

Protein deficiency impairs local and systemic immune responses to Heligmosomoides bakeri infection but little is known about their individual and interactive impacts on tissue architecture of maternal lymphoid (thymus, spleen) and visceral (small intestine, kidney, liver, pancreas) organs during the demanding period of lactation. Using a 2×2 factorial design, pregnant CD1 mice were fed a 24% protein sufficient (PS) or a 6% protein deficient (PD) isoenergetic diet beginning on day 14 of pregnancy and were infected with 100 H. bakeri larvae four times or exposed to four sham infections. On day 20 of lactation, maternal organs were examined histologically and serum analytes were assayed as indicators of organ function. The absence of villus atrophy in response to infection was associated with increased crypt depth and infiltration of mast cells and eosinophils but only in lactating dams fed adequate protein. Infection-induced lobular liver inflammation was reduced in PD dams, however, abnormalities in the kidney caused by protein deficiency were absent in infected dams. Bilirubin and creatinine were highest in PD infected mice. Infection-induced splenomegaly was not due to an increase in the lymphoid compartment of the spleen. During lactation, infection and protein deficiency have interactive effects on extra-intestinal pathologies.