Unlike in other acanthocephalans, the overian balls of Centrorhynchus corvi are complex and are composed of 24–30 ovarian ball units. Each ovarian ball unit consists of three structural and functional units – the oogonial syncytium, developing oogenetic cells and the supporting syncytium – complementary to the ovarian balls of other acanthocephalans. Three metamorphic stages of the nuclei in the oogonial syncytium are described, depending on the nuclear morphology, chromatin structure and appearance of the nucleolus. Third-stage nuclei bulge out at the periphery of the oogonial syncytium and are surrounded by its cytoplasm and a thin membrane. Ultimately these are separated from the oogonial syncytium to from oogonia containing small amounts of cytoplasmic components derived from the oogonial syncytium. Nuclei of the young oogonia, oognia at the budding stage, and 3rd-stage nuclei of the oogonial syncytium all possess nucleoli and are similar also in their nuclear dimensions and cytochemical affinities. Nuclear resemblances, and cytoplasmic similarities of the oogonia and oogonial syncytium with regard to the presence of lipids, RNA and proteins support the concept of the origin of oogonia from the oogonial syncytium.

The free oogonia divide mitotically in the cellular zone where they undergo a single mitotic division and the resulting oocytes enter the prophase of meiosis. I. The meiotic primary oocytes in contrast to the permeiotic primary oocytes of other acanthoscephalans enter the growth phase which is closely accompanied by the accumulation of various ooplasmic components such as basophilic yolk nucleus which is composed of RNA, proteins, lipoproteins and phospholipids. Histochemical features of the oogonial and supporting syncytium are described.

Samples of approximately five wild rabbits were obtained each week over the 4-year period 1967–70, and their intestines examined for adult tapeworms. Pour species of anoplocephalinae were found, Cittotaenia pectinata, C. denticulata, C. ctenoides and Andrya cuniculi. C. pectinata was found in 29% of the 968 rabbits examined, C. denticulata in 14%, C. ctenoides in 12% and A. cuniculi in 6%. There were 63 double infections, of which 44 involved A. cuniculi, and three triple infections. The most frequent number of worms per infection was one for C. pectinata and A. cuniculi and two for C. denticulata and C. clenoides, although the mean numbers for these species were respectively 7·2, 5·3, 2·7 and 1·8.A. cuniculi, and to a lesser extent C. ctenoides, were very restricted in distribution within the study area, occurring only on the higher, chalk downland (250–550 ft A.S.L.). This finding implies that individual rabbits usually spend their lives within relatively small areas.Considering all the material a seasonal trend in host infection rate was apparent only with C. denticulata, which increased in abundance from July to a peak in September and then declined gradually to a low level, lasting from April to June. Infections, including small specimens of any of the four species, were rare from February to June and it is presumed that infected intermediate hosts were correspondingly rare during this period. Except for C. denticulata, which was found more frequently in male rabbits than females, the sex of the host had no influence on its likelihood of infection. However, except for C. pectinata, the age of the host was important. Thus, C. denticulata and A. cuniculi were significantly more frequent in juveniles than adults whilst the reverse was true for C. ctenoides. Small (‘young’) specimens of C. denticulata and A. cuniculi were more frequent in juvenile than adult rabbits, but the difference was not significant for the other two species. It is concluded that only C. ctenoides survives for more than a year and that this species and C. pectinata are more likely to infect rabbits that are adult than are the other two species.

Although our knowledge of Filariae parasitic in animals is continually increasing, the main source of information concerning this group remains still confined to the important monographs by Molin (1858) and Stossich (1898). Molin's descriptions of worms are, however, often so incomplete that in using them as a basis of classification Diesing failed in his attempt to subdivide the genus Filaria, whilst Stossich's descriptions are scarcely better than those of Molin. Stiles has already pointed out the absence of clear and definite characters for the subgenus Filaria of which Filaria martis Gmelin is the type-species. Before any new division of the genus Filaria is proposed the writer thinks it is advisable to re-investigate the already known species and to re-describe them more carefully, laying special stress on such characters as the structure of the female genital organs and the structure of the microfilariae. The knowledge of Filariae parasitic in animals will be of great help in identification of worms parasitic in man.

The infection dynamics of Cyclops vicinus by the larvae of Bothriocephalus claviceps were studied experimentally. The mean number of procercoids/copepod rose to a plateau of approximately 14 as the density of eggs increased, whilst the number of copepods surviving decreased correspondingly. Copepods exposed to eggs of B. claviceps survived less well than controls, and those exposed to a higher density of eggs survived less well than those to a lower density. The mean number of parasites/copepod and the mortality of copepods were found to increase with the increasing time of exposure to eggs even when egg density was constant. These two parameters were also found to differ between gravid female copepods and unsexed young copepods. Young copepods suffered a higher parasite burden and thus a higher mortality, indicating that there are age or developmental-stage related differences in susceptibility of copepods to infection.

1. Seven species of lungworms are so far known to occur in North American deer of the genus Odocoileus: Dictyocaulus filaria (Rudolphi, 1809) Railliet & Henry, 1907; D. viviparus (Bloch, 1782) Railliet & Henry, 1907; Varestrongylus alpenae (Dikmans, 1935) n.comb.; Pneumostrongylus tenuis n.sp.; Elaphostrongylus odocoilei Hobmaier & Hobmaier, 1934; Protostrongylus coburni Dikmans, 1935; and P. macrotis Dikmans, 1931. Specimens (from deer) of all these species except Dictyocaulus filaria and Protostrongylus coburni have been studied in the course of this work.

2. Two subspecies of Odocoileus virginianus (Boddaert) and two of O. hemionus (Rafinesque) have been reported as hosts for lungworms. These may be listed with their established lungworm parasites as follows:

Common white-tailed or Virginia deer, Odocoileus v. virginianus (Boddaert): Dictyocaulus viviparus, Varestrongylus alpenae—new record, Pneumostrongylus tenuis—new record.

Northern white-tailed deer, Odocoileus v. borealis Miller: Dictyocaulus filaria, D. viviparus, Varestrongylus alpenae, Protostrongylus coburni.

Rocky Mountain mule deer, Odocoileus h. hemionus (Rafinesque): Dictyocaulus viviparus, Protostrongylus macrotis.

Columbian black-tailed deer, Odocoileus h. columbianus (Richardson): Dictyocaulus filaria, D viviparus—new record, Elaphostrongylus odocoilei.

3. A new species, Pneumostrongylus tenuis, is based on a single male lungworm from a bronchiole of Odocoileus v. virginianus. Pneumostrongylus tenuis differs from P. calcaratus Mönnig, 1932, genotype of Pneumostrongylus Mönnig, 1932, in spicular, gubernacular, and bursal characters.

4. Pneumostrongylus alpenae Dikmans, 1935, is transferred to the genus Varestrongylus Bhalerao, 1932, as a result of the study of specimens of Pneumostrongylus alpenae and Varestrongylus pneumonicus Bhalerao, 1932, genotype of Varestrongylus. The former becomes Varestrongylus alpenae (Dikmans, 1935) n.comb. Also placed in this genus are Varestrongylus sagittatus (Mueller, 1890) n.comb. (syn. Strongylus, or Protostrongylus sagittatus) and Varestrongylus capreoli (Stroh & Schmid, 1938) n.comb. (syn. Protostrongylus capreoli).

5. The reports of Protostrongylus coburni from Odocoileus v. virginianus by Goble (1943) were based on larvae and adult lungworms in sections of lung tissue. Subsequent observations by Cheatum (in litt.) strongly indicate that these were actually Varestrongylus alpenae.

6. The structure of the gubernaculum in Protostrongylus macrotis is redescribed, and the conclusion reached that this form may be regarded as an aberrant species of Protostrongylus. Appendages at the distal ends of the gubernacular crura are given the name pedes (sing, pes), and the sclerotized are, found in the bursa of a number of genera of the Protostrongylinae, the name arcus.

7. The fact that crura have not been described for the gubernaculum of Elaphostrongylus cervi Cameron, 1931, genotype of Elaphostrongylus Cameron, 1931, whereas E. odocoilei Hobmaier & Hobmaier, 1934, possesses them must be regarded as a possibly significant difference between the two species; but it is suggested that E. cervi may be found to have these structures. Therefore E. odocoilei is left in Elaphostrongylus.

Multidimensionality in parasite-induced phenotypic alterations (PIPA) has been observed in a large number of host–parasite associations, particularly in parasites with complex life cycles. However, it is still unclear whether such a syndrome is due to the successive activation of independent PIPAs, or results from the synchronous disruption of a single mechanism. The aim of the present study was to investigate the onset and progression of two PIPAs (a behavioural alteration: reversion of geotaxis, and castration) occurring in the crustacean amphipod Gammarus pulex infected with the acanthocephalan Polymorphus minutus, at different parasite developmental stages. Modifications of geotaxis in hosts differed according to the parasite developmental stage. Whereas the cystacanth stage induced a negative geotaxis (exposing the gammarid to predation by birds, the definitive hosts), the acanthella stage, not yet infective for the definitive host, induced a stronger positive geotaxis (presumably protecting gammarids from bird predation). In contrast, castration was almost total at the acanthella stage, with no significant variation in the intensity according to parasite maturation. Finally, no significant correlation was found between the intensity of behavioural changes and the intensity of castration. We discuss our results in relation with current views on the evolution of multidimensionality in PIPA.

Chagasic cardiopathy has become one of the most frequent causes of heart failure and sudden death, as well as one of the most common causes of cardio-embolic stroke in Latin America. The myocyte response to oxidative stress involves the progression of cellular changes, primarily targeting the mitochondria and modifying therefore the energy supply. In this paper we analysed the effect of the infection of mice with 2 different strains of Trypanosoma cruzi (Tulahuen and SGO Z12) in the chronic indeterminate stage (75 days post-infection), upon the structure and function of cardiac mitochondria. The structural results showed that 83% of the mitochondria from the Tulahuen-infected mice presented an increase in their matrix and 91% of the mitochondria from the SGO Z12-infected group showed a reduction in their diameter (P < 0·05). When the Krebs cycle and mitochondrial respiratory chain functionality was analysed through the measurement of the citrate synthase and complexes I to IV activity, it showed that their activity was altered in all cases in a similar manner in both infected groups. In this paper we have demonstrated that the chronic indeterminate phase is not ‘silent’ and that cardiac mitochondria are clearly involved in the genesis and progression to the chronic chagasic cardiopathy when different factors alter the host-parasite equilibrium.

FhCaBP2 is a Fasciola hepatica protein which belongs to a family of helminth calcium-binding proteins which combine an N-terminal domain containing two EF-hand motifs and a C-terminal dynein light chain-like (DLC-like) domain. Its predicted structure showed two globular domains joined by a flexible linker. Recombinant FhCaBP2 interacted reversibly with calcium and manganese ions, but not with magnesium, barium, strontium, copper (II), colbalt (II), iron (II), nickel, lead or potassium ions. Cadmium (II) ions appeared to bind non-site-specifically and destabilize the protein. Interaction with either calcium or magnesium ions results in a conformational change in which the protein's surface becomes more hydrophobic. The EF-hand domain alone was able to interact with calcium and manganese ions; the DLC-like domain was not. Alteration of a residue (Asp-58 to Ala) in the second EF-hand motif in this domain abolished ion-binding activity. This suggests that the second EF-hand is the one responsible for ion-binding. FhCaBP2 homodimerizes and the extent of dimerization was not affected by calcium ions or by the aspartate to alanine substitution in the second EF-hand. The isolated EF-hand and DLC-like domains are both capable of homodimerization. FhCaBP2 interacted with the calmodulin antagonists trifluoperazine, chlorpromazine, thiamylal and W7. Interestingly, while chlorpromazine and thiamylal interacted with the EF-hand domain (as expected), trifluoperazine and W7 bound to the DLC-like domain. Overall, FhCaBP2 has distinct biochemical properties compared with other members of this protein family from Fasciola hepatica, a fact which supports the hypothesis that these proteins have different physiological roles.

Drug resistance is now a severe and increasing problem in trypanosomes, but molecular details of mechanisms of resistance are only beginning to unveil. There is urgent need to clearly elucidate the different mechanisms of drug resistance in trypanosomes in order to circumvent existing resistance problems and avoid emergence of resistance to the next generation drugs. In this study, we cloned and characterized a novel gene, TeDR40, whose expression is associated with resistance to berenil in Trypanosoma evansi. Expression analysis showed that the gene was at least 1000-fold upregulated in resistant parasites and the encoded protein appeared to have a ubiquitous cellular localization. To investigate the association of TeDR40 with berenil-resistance, we genetically modified wild-type berenil-sensitive T. evansi for inducible over-expression of the TeDR40 gene. Induction of over-expression of TeDR40 in T. evansi led to decreased (P<0·01) sensitivity to berenil. Our findings indicate a possible correlation between over-expression of a novel gene, TeDR40, and reduced sensitivity to berenil in an in vitro-cultured clonal line of T. evansi.

The glycogen stores of adult Schistosoma mansoni worms could be labelled by incubation of the worms, after an initial reduction of their glycogen content, in the presence of [6-14C]glucose. Subsequent breakdown of the labelled glycogen by the parasite revealed that glycogen was degraded to lactate and carbon dioxide. The degradation of glycogen, as compared to that of glucose, resulted in slightly different ratios of these two end-products. This indicates that glycogen breakdown did not replace glucose breakdown to the same extent in all cells and that Krebs-cycle activity was not uniformly distributed throughout the cells of this parasite. Both fructose and mannose could replace glucose as an energy source and the rate of glycogen synthesis from either of these two carbohydrates was higher than from glucose. No indications for glyconeogenesis from C3-units were found. Glycogen metabolism of S. mansoni was not influenced by hormones of the mammalian host. It is regulated by the external glucose concentration and by the level of the endogenous glycogen stores. Studies on paired and unpaired worms showed that no interaction between male and female was necessary for the synthesis of glycogen by female worms.

The metacestode of Echinococcus multilocularis is the etiological agent of alveolar echinococcosis. The metacestode stage used for research is maintained in rodents by serial passages. In order to determine whether cryopreservation of E. multilocularis metacestodes would be suitable for long-term maintenance and replace serial passages, isolates of different geographic origin were cryopreserved in 1984–1986. The aim of the current study was to test the viability of cryopreserved isolates following long-term cryopreservation (up to 35 years) and to determine the phylogenetic clades these isolates belonged to. Cryopreserved isolates were tested for viability in vitro and in vivo in gerbils. In vitro results of 5 isolates indicated protoscolex survival in 13 of 17 experiments (76%) and metacestode survival in 5 of 12 (42%) in vivo experiments. In vivo results showed ‘abortive lesions’ in 13 of the 36 animals, 15 were negative and 8 harboured proliferating metacestode tissue containing protoscoleces. Genetic analysis confirmed the isolates belonged to European, Asian and North-American clades. In conclusion, the results of the current study indicate that metacestodes of E. multilocularis are able to survive long-term cryopreservation. Therefore, cryopreservation is a suitable method for long-term storage of E. multilocularis metacestode isolates and reduces the number of experimental animals.

This paper provides the first detailed description of a Tetracapsuloides species, Tetracapsuloides vermiformis n. sp., with vermiform stages in the bryozoan host, Fredericella sultana, and its experimental transmission from F. sultana to Cyprinus carpio. The suitability of morphological, biological and 18S rDNA sequence data for discrimination between malacosporean species is reviewed and recommendations are given for future descriptions. Presently, malacosporean species cannot be differentiated morphologically due to their cryptic nature and the lack of differential characters of spores and spore-forming stages in both hosts. We examined biological, morphological and molecular characters for the present description and for revising malacosporean taxonomy in general. As a result, Buddenbrockia plumatellae was split into two species, with its sac-like stages being ascribed to Buddenbrockia bryozoides n. comb. In addition to ribosomal DNA sequences multiple biological features rather than morphological characters are considered essential tools to improve malacosporean taxonomy in the future according to our analysis of the limited traits presently available.

Oases are semi-natural woodlots surrounded by an inhospitable desert environment. This insular-like habitat system is known to support a mixture of sedentary and migratory bird species originating from different areas. However, little is known about the interactions between these birds and parasites. In this study, we investigated the diversity, prevalence and host specificity of avian haemosporidian parasites in southern Tunisian oases in two sedentary and common bird species, the laughing dove Spilopelia senegalensis and hybrid sparrow Passer domesticus × hispaniolensis, in six sites that differ regarding vegetation structure and distance to the coast. Two new Haemoproteus lineages, related to other Haemoproteus transmitted by biting midges, were detected in doves. With regard to sparrows, all detected parasites have previously been reported in other sparrow populations, except for one new Haemoproteus lineage. Our results also showed that densely vegetated sites were characterized by the higher prevalence of Plasmodium but a lower prevalence of Haemoproteus compared with less-vegetated sites. This is the first study aiming to explore avian parasites in the oasis habitat. Gathering data on a larger sample of oases with different sizes and isolation levels will be the next step to better understand factors shaping the transmission dynamics of avian parasites in such ecosystems.

Ethylene glycol bis (β-aminoethylether)-N,N,N,N-tetraacetic acid (EGTA) is a chelating agent capable of binding to positively-charged metal ions, including a calcium-ion (Ca2+). Here, we demonstrated the inhibitory effect of the chemical on the in vitro asexual growth of the equine protozoan parasites, Babesia caballi and Babesia equi. The growth of both B. caballi and B. equi was significantly inhibited in the presence of EGTA (IC50=1·27 and 2·25 mM, respectively). Under microscopical observation, increased percentages of extracellular merozoites in the total parasites were detected in both of the cultures treated with high concentrations of EGTA. In contrast, further addition of Ca2+ to the EGTA-treated cultures prevented the parasites from clearing and the percentages of extracellular merozoites from increasing. As for B. caballi, an invasion test using high-voltage pulsing proved that EGTA has an inhibitory effect to their erythrocyte invasion. These results suggest that Ca2+ is involved in erythrocyte invasion by equine Babesia parasites.

Microbial parasites adapted to thrive at mammalian mucosal surfaces have evolved multiple times from phylogenetically distant lineages into various extracellular and intracellular life styles. Their symbiotic relationships can range from commensalism to parasitism and more recently some host–parasites interactions are thought to have evolved into mutualistic associations too. It is increasingly appreciated that this diversity of symbiotic outcomes is the product of a complex network of parasites–microbiota–host interactions. Refinement and broader use of DNA based detection techniques are providing increasing evidence of how common some mucosal microbial parasites are and their host range, with some species being able to swap hosts, including from farm and pet animals to humans. A selection of examples will illustrate the zoonotic potential for a number of microbial parasites and how some species can be either disruptive or beneficial nodes in the complex networks of host–microbe interactions disrupting or maintaining mucosal homoeostasis. It will be argued that mucosal microbial parasitic diversity will represent an important resource to help us dissect through comparative studies the role of host–microbe interactions in both human health and disease.

The extent of sequence diversity among the genes encoding 10 antigens (Tp1–10) known to be recognized by CD8+ T lymphocytes from cattle immune to Theileria parva was analysed. The sequences were derived from parasites in 23 buffalo-derived cell lines, three cattle-derived isolates and one cloned cell line obtained from a buffalo-derived stabilate. The results revealed substantial variation among the antigens through sequence diversity. The greatest nucleotide and amino acid diversity were observed in Tp1, Tp2 and Tp9. Tp5 and Tp7 showed the least amount of allelic diversity, and Tp5, Tp6 and Tp7 had the lowest levels of protein diversity. Tp6 was the most conserved protein; only a single non-synonymous substitution was found in all obtained sequences. The ratio of non-synonymous: synonymous substitutions varied from 0.84 (Tp1) to 0.04 (Tp6). Apart from Tp2 and Tp9, we observed no variation in the other defined CD8+ T cell epitopes (Tp4, 5, 7 and 8), indicating that epitope variation is not a universal feature of T. parva antigens. In addition to providing markers that can be used to examine the diversity in T. parva populations, the results highlight the potential for using conserved antigens to develop vaccines that provide broad protection against T. parva.

Evolutionary pressures exerted by parasites on the immune system, and vice versa, are surveyed from a speculative viewpoint. New information is presented about the possible channelling of suppression by MHC Class II genes in the mouse, where a novel pattern of dominant unresponsiveness mediated by H-2Ab is described. In addition, the hypothesis is advanced that phosphatidyl–inositol anchorage on the surface of parasites may represent a novel evasion mechanism, in which the spread of the immune response by epitope linkage is inhibited by host phospholipase.

This study investigated why the susceptible or resistance phenotype to the nematode Heligmosomoides polygyrus was lost when susceptible (C57BL/6) and resistant (Balb/c) strains of mice were housed together in indoor arenas with continuous transmission of the parasite larvae present in peat trays (Scott, 1991). First, both strains expressed their normal phenotype when given a controlled challenge while living in arenas, and when experimentally infected with only 5 parasite larvae. To test whether chronic exposure to peat altered the resistance phenotype, mice were given a challenge infection while living on peat. C57BL/6 mice living on peat had higher egg production and higher worm numbers than Balb/c mice, except at 2 months post-challenge. Finally, natural transmission rates were increased in arena experiments through either regular replacement of arena mice with naïve mice or direct introduction of additional larvae. A transient difference in infection levels between strains was detected in response to a modest increase in transmission whereas a 10-fold increase in transmission allowed C57BL/6 mice to exhibit the typical profile of high egg production and elevated worm numbers. These data indicate that C57BL/6 mice are less able to regulate parasite numbers at high transmission rates compared with lower transmission rates.

Cysteine peptidases of protozoa have been implicated in a variety of biological events, and the expression of these enzymes is modulated in response to distinct stimuli, including environmental changes and differentiation. In the present work, we have examined the expression of cysteine peptidases from Herpetomonas samuelpessoai grown at distinct temperatures and during dimethylsulfoxide (DMSO)-elicited differentiation. We demonstrated that a 45 kDa cysteine peptidase had its activity reduced during the parasite growth at 37°C in comparison to 26°C, and when cultured up to 72 h in the presence of DMSO. The modulation in the 45 kDa cysteine peptidase expression is connected to the differentiation process, since both temperature and DMSO are able to trigger the promastigote to paramastigote transformation in H. samuelpessoai. The possible immunological similarity of H. samuelpessoai proteins with well-known cysteine peptidases produced by trypanosomatid pathogens, including cruzipain (Trypanosoma cruzi) and cysteine peptidase b (cpb) from Leishmania mexicana, was also investigated, as well as with calpain molecules. The protein cellular lysate of H. samuelpessoai reacted with antibodies raised against cpb of L. mexicana and calpain of Drosophila melanogaster; however, no reaction was observed against cruzipain. The 35 kDa cpb-like protein had its expression diminished in DMSO-treated parasites, while the 80 kDa calpain-like molecule was enhanced and an additional 30 kDa calpain-related polypeptide was exclusively observed in these cells. Fluorescence microscopy and flow cytometry analyses corroborated these data. The results described above add H. samuelpessoai to the list of parasites whose differentiation seems to be correlated with cysteine peptidase expression.