An ultrastructural study of microfilariae of Wuchereria bancrofti was performed after in vitro treatment with diethylcarbamazine. One of the first morphological alterations produced by treatment with 5, 10 or 50 μg/ml of DEC was the loss of microfilarial sheaths. Drastic effects of DEC were only detected when microfilariae were exsheathed. Microfilariae treated with 5, 10 or 50 μg/ml DEC showed severely affected organelles, formation of several vacuoles mainly in the hypodermis, and cytolysis. Some microfilariae showed extreme cellular disorganization with abundance of electron-dense degenerating organelles, numerous large vacuoles, and nuclear condensation. Lamellar bodies probably related to an assembly of endoplasmic reticulum membranes were observed in some damaged microfilariae. Thus, in vitro treatment with concentrations of DEC similar to therapeutic conditions had direct effect by causing a loss of the microfilarial sheath of W. bancrofti with subsequent damage of organelles and apoptosis.

Although ascarid nematodes are important parasites of wild animals of public health concern, few species of ascarids from wild animals have been studied at the molecular level so far. Here, the classification and phylogenetic relationships of roundworms from 21 species of captive wild animals have been studied by sequencing and analysis of parts of the ribosomal 18S and 28S genes and the mitochondrial (mt) 12S gene. Phylogenetic relationships were inferred by 3 methods (NJ/MP/ML) based on the data of single gene sequences and concatenated sequences. Homology analysis indicated that the 18S sequences were conserved among roundworms from all 21 species and that 28S showed interspecies variability. Divergence levels displayed in 12S suggested that 12S appears to be either intra- or interspecifically variable. Evolutionary trees indicated that the ascarids split into 2 families, 4 genera and 7 species, with high bootstrap support for each clade. Combined trees suggested that Baylisascaris ailuri is more closely related to B. transfuga than to B. schroederi. This study provides useful molecular markers for the classification, phylogenetic analysis and epidemiological investigation of roundworms from wild animals.

Adult Haemonchus contortus obtained from freshly killed sheep were incubated in a medium similar to Tyrode's saline containing known amounts of D-[U-14C]glucose. The worms appeared to remain in a healthy condition throughout the incubations which lasted for up to 6 h. All the radioactivity was recovered either within the worms or in the incubation vessel in the form of CO2, excretory products and unmetabolized glucose. An oxygen electrode in the incubation liquid showed that, because of their rapid oxygen consumption, the worms were under anaerobic conditions during all or nearly all of the incubation period, despite the presence of oxygen in the gas phase of the vessel. In terms both of quantity and radioactivity the main excretory products in solution were propan-1-ol, propionate and acetate. Smaller amounts of ethanol, lactate and succinate were excreted. Much radioactivity was associated with the expired CO2. At the end of the incubations glucose other than the initial radioactive glucose was detected indicating that the absorption of glucose by H. contortus is complex and needs further investigation. The present experiments suggest that the rate of absorption depends on the worm's need for nutrients. The results are compared with those found for other parasitic nematodes, particularly Ascaris lumbricoides, Heterakis gallinae and Trichuris vulpis. The importance of CO2 fixation in the utilization of energy from glucose by H. contortus is discussed.

Previous laboratory studies have indicated that tenebrionid beetles infected with Hymenolepis diminuta display behavioural alterations. These are assumed to increase the likelihood of this intermediate host being predated by the Rattus sp. definitive host, and hence provide support for the Manipulation Hypothesis. We tested this hypothesis by both assessing beetle behaviour and predation rates in semi-naturalistic environments. Behavioural assays showed that infected beetles were more often exposed (not concealed under boxes) than uninfected beetles. However, there were no differences in predation rates between infected and uninfected beetles. We discuss this in terms of the historical and evolutionary contexts under which such altered behaviours could evolve and their implications for the Manipulation Hypothesis.

1. Liver lesions were easily induced in hamsters with two strains of E. histolytica but not with six others.

2. Serial liver passage increased the invasiveness to the rat's caecum of one strain which had become attenuated by in vitro cultivation.

3. The invasiveness of one of the liver passage substrains was lost a second time after cultivation in vitro and a second series of liver passages restored some degree of virulence.

4. Serial liver passage did not increase the invasiveness of two avirulent strains.

5. The ease of production of amoebic liver lesions in hamsters is not correlated with invasiveness in the rat's caecum.

A protein phosphatase exclusively dependent upon micromolar amounts of Ca2+ and calmodulin has been identified and partially purified from Leishmania spp. Complete obliteration of its activity is observed in the presence of calmodulin antagonists such as trifluoperazine, fluphenazine and calmidazolium. Relative insensitivity to okadaic acid and lack of activation in the absence of Ca2+ and calmodulin distinguishes this enzyme from PP1, PP2A and PP2C-type protein phosphatases. Cross-reactivity of the enzyme was observed with antibodies that recognize both the A and B chains of calcineurin, a PP2B type Ca2+ and calmodulin-dependent phosphatase from brain. FK506, an immunosuppresive drug that inhibits the enzyme from other sources inhibited the enzyme only in the presence of exogenous FK binding protein, whereas Cyclosporin A inhibited the enzyme in crude preparations. Taken together these results reveal the presence of a Ca2+ and calmodulin-dependent phosphatase from Leishmania. This is the first report of the presence of a PP2B-type protein phosphatase from a pathogenic protozoa.

There has been a recent shift in the literature on mosquito/Plasmodium interactions with an increasingly large number of theoretical and experimental studies focusing on their population biology and evolutionary processes. Ecological immunology of mosquito-malaria interactions – the study of the mechanisms and function of mosquito immune responses to Plasmodium in their ecological and evolutionary context – is particularly important for our understanding of malaria transmission and how to control it. Indeed, describing the processes that create and maintain variation in mosquito immune responses and parasite virulence in natural populations may be as important to this endeavor as describing the immune responses themselves. For historical reasons, Ecological Immunology still largely relies on studies based on non-natural model systems. There are many reasons why current research should favour studies conducted closer to the field and more realistic experimental systems whenever possible. As a result, a number of researchers have raised concerns over the use of artificial host-parasite associations to generate inferences about population-level processes. Here I discuss and review several lines of evidence that, I believe, best illustrate and summarize the limitations of inferences generated using non-natural model systems.

Parasites are more fecund than free-living relatives. The traditional explanation of this is that parasites have to compensate for massive mortality in the transmission phase of their life cycles, but there are neo-Darwinian problems with this interpretation. Similarly, parasites invest more resources in reproduction than free-living relatives but often live longer as adults, and yet negative correlations are expected between fecundity and longevity. These patterns and paradoxes are discussed within the context of a general life-cycle theory. The theory is also used to address questions concerning the influence of age-specific mortality on life-cycle patterns, the trade-off between gamete size and numbers, and the relative merits of gametic and non-gametic reproduction. Wherever possible, the theory is related to facts about parasites.

Female Tenebrio molitor infected with metacestodes of Hymenolepis diminuta exhibit elevated concentrations of female-specific proteins in their haemolymph and the origin of these has been investigated. Following a 4 h in vitro incubation with [14C]leucine, fat bodies from non-infected females secreted 13 times more protein than those from females 12 days post-infection. A comparison of the uptake in vivo of radio-isotope labelled amino acids by ovaries from non-infected and infected beetles of various ages revealed no differences; however, a 51·5% decrease in protein sequestration was detected in females 12 days post-infection. Electrophoresis of homogenates of radio-isotope labelled ovaries demonstrated that the majority of label was associated with vitellin sub-units. It is suggested that the decrease in vitellogenin sequestration associated with infection results in an increase in the haemolymph concentration of these proteins despite a concomitant reduction in their secretion by fat bodies. Both fat body synthesis and ovarian sequestration are under juvenile hormone control and it is proposed that metacestodes of H. diminuta may cause a reduction in the concentration of this hormone in the intermediate host.

“Piroplasmosis,” or “biliary fever” in horses, has hitherto been regarded as a disease due to a distinctive parasite, Piroplasma equi Laveran. We propose to show that there are two specifically distinct parasites concerned in the production of biliary fever, and that consequently two distinct diseases have hitherto been confused under this name and under the name of piroplasmosis.

Blastocrithidia familiaris were found to be parasitic in the midgut, ileum and rectum of Lygaeus pandurus. The host—parasite relationship is described. Attachment of parasites in the midgut and ileum occurs by interdigitation of expanded flagella over and between the microvilli. No attachment to microvilli was observed where extracellular membranes form well-organized layers which lie parallel to the gut wall and completely separate the microvilli border from the lumen. The extracellular membranes originate from delamination of the outer unit membrane of microvilli which consists of a double plasma membrane. The function of the extracellular membrane layers and their possible role as a peritrophic membrane in preventing parasite attachment is discussed in relation to previous studies on midgut cells in Hemiptera with a similar apical coat on midgut microvilli. In the rectum, parasites attach to the cuticle of the gland cells and not to the rest of the rectal wall. Attachment to the cuticle occurs by the formation of hemidesmosomes. A comparison of the relationship of B. familiaris and its host to previous ultrastructural studies of associations between kinetoplastid flagellates and their respective hosts is discussed.

Sera from swine, rabbit, and dog, that had never been exposed to Toxoplasma gondii, demonstrated significant killing of T. gondii tachyzoites in vitro, while cat serum did not. Swine and rabbit sera contained natural IgM antibody against the tachyzoites, and the classical complement pathway was activated by the binding of natural IgM antibody to the tachyzoites, leading to lysis. Anti-T. gondii antibodies, induced in swine or cat infected with T. gondii, had no killing effect by themselves but killed the tachyzoites in the presence of swine complement. However, the anti-T. gondii antibodies of swine or cat demonstrated a very low killing effect in the presence of cat complement. This suggests that T. gondii tachyzoites have an evasion mechanism to prevent lysis which is specific for cat complement.

Changes in host phenotype are often attributed to manipulation that enables parasites to complete trophic transmission cycles. We characterized changes in host phenotype in a colonial host–endoparasite system that lacks trophic transmission (the freshwater bryozoan Fredericella sultana and myxozoan parasite Tetracapsuloides bryosalmonae). We show that parasitism exerts opposing phenotypic effects at the colony and module levels. Thus, overt infection (the development of infectious spores in the host body cavity) was linked to a reduction in colony size and growth rate, while colony modules exhibited a form of gigantism. Larger modules may support larger parasite sacs and increase metabolite availability to the parasite. Host metabolic rates were lower in overtly infected relative to uninfected hosts that were not investing in propagule production. This suggests a role for direct resource competition and active parasite manipulation (castration) in driving the expression of the infected phenotype. The malformed offspring (statoblasts) of infected colonies had greatly reduced hatching success. Coupled with the severe reduction in statoblast production this suggests that vertical transmission is rare in overtly infected modules. We show that although the parasite can occasionally infect statoblasts during overt infections, no infections were detected in the surviving mature offspring, suggesting that during overt infections, horizontal transmission incurs a trade-off with vertical transmission.

We investigated the timing of seasonal activity of the seabird tick Ixodes uriae by examining engorgement rates of off-host ticks and the prevalence of infested common guillemots (Uria aalge) and kittiwakes (Rissa tridactyla) on the Isle of May, Scotland. More than 99% of I. uriae fed during the period late April to early August which coincided with the seabird breeding season. No ticks fed in the autumn and winter, and none over-wintered in the engorged state. Peak tick feeding activity was during the hosts' incubation period in May and early June, when over 70% of birds were parasitized. Few ticks were active when guillemot chicks were being brooded, or during the early part of kittiwake chick-rearing. Adult female tick feeding peaked in the first week of June, while nymphal and larval activity peaked in the third week of May. Adult female ticks fed later than nymphs on guillemots and larvae on both guillemots and kittiwakes; however, there was considerable temporal overlap in the feeding periods of the 3 stages on both hosts. All larvae and nymphs fed in May and early June, but up to 18% of adult females remained unengorged at this time, and probably deferred feeding by 1 year. A small proportion of individuals which fed as larvae in May appeared to feed again as nymphs in July of the same season, thereby shortening their life-cycle by 1 year. The duration of the life-cycle of I. uriae on the Isle of May is typically 3 years but varies from 2 to 4 years. Ticks feeding on guillemots did so significantly earlier than those feeding on kittiwakes, possibly because guillemots start breeding earlier in the year. Breeding of both guillemots and kittiwakes was later in 1994 than in 1993. This delayed the activity of all tick stages on kittiwakes and adult female ticks on guillemots, but did not affect the timing of activity of nymphs or larvae feeding on guillemots.

The hydrolytic, reductive and oxidative enzyme systems involved in the phase I biotrans formation of xenobiotic compounds have been investigated in Hymenolepis diminuta. Adult H. diminuta are able to carry out a range of hydrolytic and reductive reactions, but in common with other helminths oxidative detoxification reactions were absent (oxidative demethylation, aniline hydroxylation, nitrobenzene hydroxylation, biphenyl hydroxylation). These oxidative reactions were readily demonstrated in rat liver. Extracts of H. diminuta hydrolysed nitrophenylphosphates and inorganic pyrophosphate, but not arylsulphates, nor could epoxide hydratase activity be detected. N-Deacetylase activity was present. However, O-deacetylase activity could not be demonstrated, although butyrate and palmitate, but not benzoate, esters were hydrolysed. H. diminuta was capable of hydrolysing a range of a-and β-glycosides, but not β-glucuronides. Extracts of H. diminuta reduced azo-compounds, aldehydes and disulphides, but ketones and aromatic nitro-compounds were not reduced. The phase I detoxification systems of H. diminuta differ considerably from those of its rat host; the results also suggest that, within the cestodes, there may be considerable species variation in detoxification reactions.

The transmission of Ascaris suum was studied in outdoor reared pigs. From May to June 2001, 6 farrowing paddocks were naturally contaminated with A. suum using experimentally infected seeder pigs. Early July, 1 sow farrowed on each paddock. One piglet per litter was slaughtered every second week starting at week 3 post-partum (p.p.) for registration of liver white spots and recovery of A. suum from the lungs and the small intestine. The last pigs were slaughtered at week 19 p.p. Faeces was examined for parasite eggs and blood was analysed for A. suum-specific antibodies. Weaning took place at week 7 p.p. by removing the sow. Paddock infection levels were estimated by regular examination of soil samples and in late June and late November using parasite naïve tracer pigs. Paddock contamination was high but eggs developed slowly resulting in a low initial transmission to the experimental pigs. By week 5 p.p. transmission had increased and the numbers of infective eggs in the soil increased during the study. The results indicate a continuous uptake of infective eggs, but visceral larval migration was reduced with time, probably due to the development of a pre-hepatic barrier. Nevertheless, a rather large population of adult worms remained in the pigs throughout the study, and it may primarily have been eggs ingested in the early infection phase that gave rise to the patent infections. It is suggested that neonatal exposure may result in increased persistence and size of adult worm burden and that the higher ‘life-time worm burden’ may be of significant economic importance.

The direct effects of phytohormones (auxin and kinetin) and root diffusates on the surface lipophilicity of the plant parasitic nematodes Globodera rostochiensis and Meloidogyne incognita were investigated. The fluorescent lipid probe AF18 (5-N-(octodecanoyl) aminofluorescein) was used to detect surface changes. Root diffusates increased AF18 uptake by G. rostochiensis while it had no effect on M. incognita. Kinetin and auxin decreased AF18 uptake in G. rostochiensis, while they had the opposite effect on M. incognita. Auxin/kinetin ratio was also found to be important in triggering the surface changes, especially at high concentrations. Whether plant nematodes have auxin and/or kinetin binding proteins is discussed as well as the mechanism behind the surface lipophilicity changes due to root diffusates and phytohormones.

The in vitro effects of 4 arylimidamides (DB811, DB786, DB750 and DB766) against the proliferative tachyzoite stage of the apicomplexan parasite Besnoitia besnoiti were investigated. These four compounds had been shown earlier to exhibit in vitro activities in the nanomolar range against the related apicomplexans Neospora caninum and Toxoplasma gondii. Real-time-PCR was used to assess B. besnoiti intracellular proliferation in vitro. Preliminary assessment by light microscopy identified DB811 and DB750 as the most promising compounds, while DB786 and DB766 were much less effective. Three-day-growth assays and quantitative real-time PCR was used for IC50 determination of DB811 (0·079 μM) and DB750 (0·56 μM). Complete growth inhibition was observed at 1·6 μM for DB 811 and 1·7 μM for DB750. However, when infected cultures were treated for 14 days, proliferation of parasites occurred again in cultures treated with DB750 from day 4 onwards, while the proliferation of DB811-treated tachyzoites remained inhibited. Electron microscopy of B. besnoiti-infected fibroblast cultures fixed and processed at different time-points following the initiation of drug treatments revealed that DB811 exerted a much higher degree of ultrastructural alterations compared to DB750. These results show that arylimidamides such as DB811 could potentially become an important addition to the anti-parasitic arsenal for food animal production, especially in cattle.

Few studies have focussed on the health and immunity of triploid Atlantic salmon and therefore much is still unknown about their response to commercially significant pathogens. This is important if triploid stocks are to be considered for full-scale commercial production. This study aimed to investigate and compare the response of triploid and diploid Atlantic salmon to an experimental challenge with Neoparamoeba perurans, causative agent of amoebic gill disease (AGD). This disease is economically significant for the aquaculture industry. The results indicated that ploidy had no significant effect on gross gill score or gill filaments affected, while infection and time had significant effects. Ploidy, infection and time did not affect complement or anti-protease activities. Ploidy had a significant effect on lysozyme activity at 21 days post-infection (while infection and time did not), although activity was within the ranges previously recorded for salmonids. Stock did not significantly affect any of the parameters measured. Based on the study results, it can be suggested that ploidy does not affect the manifestation or severity of AGD pathology or the serum innate immune response. Additionally, the serum immune response of diploid and triploid Atlantic salmon may not be significantly affected by amoebic gill disease.

The immune response to leishmaniasis is complex, and the result of infection depends on both the genetic composition of the Leishmania species and the immunity of the host. Clinical and experimental evidence suggest that the activation of B cells leads to exacerbation of visceral leishmaniasis. However, the role of B-1 cells (a subtype of B lymphocytes) in the pathogenesis of experimental visceral leishmaniasis has not yet been elucidated. In this study, we investigated the importance of B-1 cells in experimental infection with Leishmania. (L.) chagasi. Our results showed that BALB/XID mice (X-linked immunodeficient mice which are genetically deficient in B-1 cells) infected with L. (L.) chagasi for 45 days had a significant reduction in parasite load in the spleen when compared with control mice. Cytokine analysis showed that the BALB/XID mice had lower amounts of IL-10 in their sera compared with control group. In addition, the transfer of B-1 cells from wild type mice into IL-10KO animals led to an increase in susceptibility to L. (L.) chagasi infection in the IL-10KO mice, suggesting that the IL-10 produced by these cells is important in experimental infection. Our results suggest that B-1 cells may play an important role in susceptibility to L. (L.) chagasi.