bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the infection of bulinid snails with Schistosoma mattheei
Authors: Kinoti G. K.
Published: June 2009

In an attempt to determine the mechanisms of resistance to schistosome infection operative in bulinid snails, an histological study was carried out on batches of a refractory strain of Bulinus truncatus and two highly susceptible strains of B. africanus killed at various intervals of time, ranging from 7 h to over 3 months, after exposure to infection with Schistosoma mattheei miracidia.

It was found that only a small fraction (less than 1%) of the miracidia penetrated B. truncatus, and that they penetrated only a few of the snails exposed. Much larger proportions (up to 26%) of the miracidia penetrated B. africanus and they penetrated nearly all the snails exposed.

In the susceptible B. africanus only miracidia which settled in the loose tissues of the head-foot proceeded to develop: those settling in dense tissue failed to develop and degenerated within about 2 days.

A strong infiltration reaction of amoebocytes rapidly destroyed the few miracidia that successfully penetrated B. truncatus. In contrast, B. africanus did not respond to the presence of miracidia in its tissues, nor to mother or to daughter sporocysts before the onset of cercarial shedding: it reacted only to cercariae.

It is concluded (a) that the combination of an effective surface barrier and an active defence mechanism due to amoebocytes were responsible for complete resistance to S. mattheei infection in B. truncatus (b) that successful establishment of S. mattheei infection in B. africanus depended on the failure of the snail to recognize the schistosome miracidia and sporocysts as foreign material.

I am indebted to Professor George S. Nelson for advice and encouragement in this work which was carried out at the London School of Hygiene and Tropical Medicine. I am most grateful to Dr R. J. Pitchford, Dr C. A. Wright and Dr F. Arfaa for providing material for schistosome and snail cultures and to the East African Community and the British Ministry of Overseas Development for financial support.
Immunity toTrichinella spiralisII. Immunity produced by the adult worm in mice
Authors: Denham D. A.
Published: June 2009

It has been shown that the 5th or adult stage ofTrichinella spiralisstimulates strong immunity in mice. This was shown using a transfer technique and irradiated worms. A comparison between the immunity produced by a normal infection and one which has been irradiated is made and explanations offered to explain the fact that less immunity is stimulated by irradiated larvae.

I would like to express my gratitude to H.M. Treasury and to the Agricultural Research Council for financial support during the time that this work was conducted. I would also like to thank Professor W.I.B. Beveridge, within whose department this work was conducted, for the facilities provided. I would also like to record my gratitude to Dr W. C. Campbell for the many stimulating discussions we have had on the subject ofTrichinella.
The effects of parasitism by the daughter sporocyst ofCercaria bucephalopsis haimaenaLacaze-Duthiers, 1854, on the digestive tubules of the cockle,Cardium eduleL.
Authors: James B. L. , Bowers E. A.
Published: June 2009

The effects of parasitism by the daughter sporocyst ofCercaria bucephalopsis haimaenaLacaze-Duthiers, 1854, on the digestive cells ofCardium eduleL. was investigated by comparing histochemically stained cells in healthy and parasitized animals. Two effects were apparent: (a) the branches of the daughter sporocysts compress the walls of the digestive gland ducts and tubules, and cut off the more distal tubule cells from their food supply, inducing starvation autolysis, (b) in digestive tubule cells not so cut off, glucose, glycogen, glycoproteins, phospholipid and proteolipid food storage globules and acid mucopolysaccharide are reduced. Neutral lipids, fatty acids, alkaline phosphatase, acid phosphatase and non-specific esterase are increased and there is also a compensatory increase in the number of food vacuoles. In the visceral haemocoel, in the neighbourhood of the parasite, glucose, fatty acids, neutral lipids and acid mucopolysaccharide are increased and glycogen reduced.

We are grateful to Professor E. W. Knight-Jones, for helpful comments and good working facilities, and to the Science Research Council, for the grant of a research studentships to one of us (E.A.B.).
The histochemistry of the cystogenous gland cells and cyst wall ofParorchis acanthusNicoll, and some details of the morphology and fine structure of the cercaria
Authors: Rees Gwendolen
Published: June 2009

The cyst wall ofParorchis acanthusNicoll, consists of an outer wall of three layers and an inner wall of two layers. The outer wall is hemispherical, complete, attached to the substratum and extends as a flange around the margin. The composition of its three layers differ dorsally and ventrally. Dorsally the layers are: (1) acid mucopolysaccharide and neutral mucopolysaccharide, (2) protein and lipoprotein, (3) acid mucopolysaccharide, neutral mucopolysaccharide and glyco-protein. Ventrally the layers are: (1) acid mucopolysaccharide, protein and lipoprotein, (2) acid mucopolysaccharide. The middle layer in both is secreted by the ventral granular cystogenous glands and the outer and inner layers, dorsally and ventrally, by the dorsal and ventral agranular cystogenous glands respectively.

The inner cyst wall is oval in surface view. It consists of two layers, both of neutral mucopolysaccharide, the outer giving a more pronounced reaction. Both are secreted by the dorsal granular cystogenous glands. The ventral wall is strengthened by a secretion from the plug-forming gland cells and consists of neutral mucopolysaccharide. All the layers of the cyst wall show the same histochemical reactions as the glands which secrete them.

Studies on the fine structure of the cercaria have revealed mammalian-type synapses in the neuropile of the central nervous system, rind cells around the ganglia, an elaborate arrangement of muscles in the wall of the oral sucker, the flame cell structure and the structure of the granules contributing to the formation of the cyst wall.
The morphology and life-cycle of Cephalochlamys namaquensis (Cohn, 1906) (Cestoda: Pseudophyllidea) from Xenopus muelleri and X. laevis
Authors: Thurston June P.
Published: June 2009

Some morphological characteristics of Cephalochlamys namaquensis from Xenopus muelleri collected at Kajansi, Kampala, are described.

Specimens of cestodes from other localities in Africa are compared with those from Kajansi in order to assess the reliability of the characters of the proposed genus Pseudocephalochlamys Yamaguti, 1959. Reasons are given for rejecting the genus.

The embryonated, non-operculate egg capsules hatch at once in water. The ciliated coracidium is eaten by cyclopid copepods and the oncosphere rapidly penetrates through the mid-gut wall into the haemocoel. The procercoid develops a cercomer which moves actively during development and which retains the six hooks of the oncosphere. The procercoid develops the scolex, osmoregulatory canals and calcareous corpuscles typical of the adult while within the copepod. It is enclosed within a membrane. The procercoid is infective to Xenopus toads 20 days after being ingested by the copepod. No other intermediate host has been found.

Thermocyclops infrequens Kiefer is the intermediate host at Kajansi, Kampala. The maximum number of C. namaquensis recovered from one toad was 103; usually there are between 1 and 6 per toad. Between 22% and 100% of Xenopus muelleri and X. laevis from different localities are infected with C. namaquensis.

I wish to express by thanks to the Fisheries Officers and fishermen of Kajansi Fish Farm who have willingly caught Xenopus for me whenever required, and also to the many other people who have assisted me in getting specimens with which to work.

I am also indebted to Mr L. Rugema who prepared most of the histological preparations, to Dr J. Green, Westfield College, London, who kindly identified Thermocyclops infrequens, and to Dr G. Rees, University College of Wales, Aberystwyth, who gave me many useful comments during the course of this work.

A research grant from Makerere University College contributed towards the cost of obtaining specimens.
Observations on the maintenance of Trichomonas vaginalis and Trichomonas foetus; the effects of cortisone and agar on enhancement of severity of subcutaneous lesions in mice
Authors: Jeffries L. , Harris Margaret
Published: June 2009

Methods are described for the freezing of trichomonads, suspended in a liverinfusion broth, to – 20 °C and – 70 °C, and storage at these temperatures. After 9 months’ storage at – 70 °C, with dimethyl sulphoxide, six strains of T. vaginalis and three strains of T. foetus were alive; three trichomonas strains frozen earlier were also alive after 13 months. Four of the T. vaginalis strains survived equally well for 6 months at – 70 °C, in the presence of either dimethyl sulphoxide or glycerol.

Although trichomonads may be maintained by subculture in a modified Diamond medium, storage at – 70 °C is more economical and less tedious; – 20 °C is not a satisfactory storage temperature for T. vaginalis or T. foetus, even in the presence of dimethyl sulphoxide or glycerol.

The severity of subcutaneous lesions in mice produced by six freshly isolated strains of T. vaginalis, and two out of three stock culture strains of T. foetus, was enhanced by either the addition of agar to the suspending medium or administration of cortisone to the mice. One strain of T. foetus produced lesions only in the presence of agar, cortisone, on the dose schedule used, being ineffective.

After storage at – 70 °C or cultivation in agar medium for 6 months, the virulence of trichomonads of either species was little affected, and lesions in mice were enhanced by agar in a similar degree to that found originally.

For enhancing the severity of subcutaneous lesions in mice the agar method, involving only one injection, is simpler than the repeated administration of cortisone to infected mice; agar was shown to be more effective than cortisone with small infecting doses of one strain of T. vaginalis quantitatively tested.

The subcutaneous injection of mice with trichomonads suspended in a liver-infusion broth containing 0·06% agar regularly produces lesions of the degree of severity required for the evaluation of compounds for therapeutic activity.

We express our gratitude to Mr S. A. Price for constructive criticism and helpful suggestions during the preparation of the manuscript. Dr S. R. M. Bushby kindly provided details of the dimethyl sulphoxide method and apparatus in use in his laboratory for the low-temperature preservation of tumour cells and trichomonads. For supplying the trichomonas strains we are grateful to Dr L. P. Joyner, Miss M. Moore-Tucker and Mr C. S. Ledwich. We thank Mr W. A. Freeman for advice on the composition of the inoculum medium.
Schistosome vaccines: current progress and future prospects
Authors: Sher A. , James Stephanie L. , Correa-Oliveira R. , Hieny Sara , Pearce E.
Published: June 2009

Vaccination against human schistosomes in laboratory hosts is now a reality. A number of different parasite molecules have been shown to confer partial protective immunity against challenge infection withSchistosoma mansoniorSchistosoma japonicumin rodent or primate hosts. These antigens are unusually diverse in their structure and stage specificity. Interestingly, although all of the vaccine molecules characterized are situated in the tegument, their exposure on the parasite surface, in most instances, is transient and/or non-essential. The properties of four of these immunogens, glutathione-S-transferase (P26,28), paramyosin (Sm97), GP38, and GP18 are discussed. Despite the identification and recombinant synthesis of several promising protective antigens, vaccination of humans against schistosomiasis remains in the realm of fantasy. At the technical level, a major problem is the failure of any of the current vaccine immunogens and immunization protocols to induce levels of resistance sufficient for significant reduction of human infection or disease. Once this important hurdle is passed, human immunization trials should be attempted as the potential beneficial impact of a vaccine against schistosomiasis remains enormous.
Amphimermis bogongae sp.nov. and Hexamermis cavicola sp.nov. from the Australian bogong moth, Agrotis infusa (Boisd.), with a review of the genus Amphimermis Kaburaki & Imamura, 1932 (Nematoda: Mermithidae)
Authors: Welch H. E.
Published: June 2009

Common (1952, 1954) found a mermithid that parasitized the bogong moth, Agrotis infusa (Boisd.) during its resting period on the walls of caves in Australia. Nematode material that he collected was given to Dr J. B. Goodey, Rothamsted Experimental Station, Harpenden, Herts, England, who found it to contain two species. This material subsequently was given to me, and on examination each species was found to be undescribed. A description of each follows with a suggested life cycle and some remarks on the unusual parasitism of adult insects by the mermithids. This material permitted a re-examination of the taxonomy of the genus Amphimermis Kaburaki & Imamura, 1932.
Hyperplasia of the bile duct in fascioliasis and its relation to the problem of nutrition in the liver-fluke, Fasciola hepatica L.
Authors: Dawes Ben
Published: June 2009

Histological investigations of the bile ducts of various hosts of F. hepatica during the early stages of infection, when the flukes are burrowing in the liver and have not yet reached the bile ducts, indicate that subtle changes are brought about, probably by chemical agencies and as a result of the inflammatory process, in the bile ducts of the hosts. The transitory appearance of minute cytoplasmic blebs at the free margins of the epithelial cells seems to inaugurate an intense hyperplasia of the epithelium with tubular ingrowths and adenomatous development of glandular tissue, and an associated fibrosis which produces a thick underlying layer of dense fibrous tissue. At the time of entry of the flukes into the biliary system the hyperplastic epithelium is intact, but soon the spines and suckers of the flukes abrade the superficial cells until this part of the duct is completely denuded. It is suggested that as a result of the inflammatory reaction, the fluke has been provided with a ‘pasture’ of hyperplastic epithelium and connective tissue on which it may continue to browse for considerable periods without necessarily affecting the host adversely. Tissue debris is found in the contents of the bile duct and similar homogenized materials occur in the caecal contents of the fluke. Previous researches have shown that the fluke will feed on various tissues, and it is suggested that this tissue-feeding habit persists during its life in the bile duct. These results agree with the findings of Müller (1923) but are at variance with the results obtained by other investigators, as is shown in discussion. The hyperplasia of the bile duct is not characteristic of fascioliasis, occurring also in clonorchiasis, opisthorchiasis and dicrocoeliasis, and in these and possibly other instances it is probably intimately connected with the nutrition of the flukes concerned.
Blood parasites of wild voles,Microtus agrestis, in England
Authors: Baker J. R. , Chitty Dennis , Phipps Ellen
Published: June 2009

1. Thirty-six of 70Microtus agrestiscaptured near Oxford, England, between January and July, 1961, were infected with blood parasites—9 withTrypanosoma microtiLaveran & Pettit, 1909, 18 withBabesia microtia(França, 1912) and 19 withGrahamella microtiLavier, 1921: some had more than one species.

2. Morphologically indistinguishable parasites were found in 6 of 20Clethrionomys glareolus(Babesiain 3,Trypanosomain 2, andGrahamellain 1) and 2 of 4Apodemus sylvaticus(Grahamellaonly).Hepatozoonsp. indet. was found in oneC. glareolus.

3. It is probable that the proportion ofM. agrestiswith patent infections ofG. microtiincreased, and possibly that due toT. microtifell, during February–April, 1961.

4.M. agrestisoften have very enlarged spleens and it appeared thatB. microtia(sometimes associated withT. microti) was commoner in the animals with the largest spleens.
B-chromosomes: germ-line parasites which induce changes in host recombination
Authors: Bell G. , Burt A.
Published: June 2009

The object of this paper is to suggest that there may be an unexpected connexion between parasites and the evolution of sex, using for illustration an unfamiliar type of parasite, the selfish chromosome. The major intellectual challenge of sexuality is to an environment which is continually getting worse. The elegant solution given by the Red Queen theory (Levin, 1975; Hamilton, 1980; Bell, 1982; Bell & Maynard Smith, 1988) is that the relevant aspect of the environment is provided by antagonists—pathogens, predators and competitors—which, because they can respond adaptively so as to negate any improvement that has been made, provide a constant stimulus for continued evolution. Sexuality and recombination are favoured because some of the new combinations of genes which they create are resistant to the current population of antagonists. In other respects, sex and recombination are probably highly disadvantageous: outcrossed sex is expensive because it halves the rate of transmission of genes, while recombination breaks up successful combinations of genes. It is only in certain circumstances that the necessity for continual counter-adaptation will overcome these disadvantages: in particular, the damage (reduction in fitness) caused by an antagonist must be substantial, and the amount of damage must depend on a genetic interaction between the antagonistic species. These requirements are often satisfied by host—parasite systems, where both the ecological and genetic interactions between the antagonists may be very severe and highly specific (see reviews by Day, 1974 and Burdon, 1987). It is possible, therefore, that sex and recombination are maintained in natural populations largely through the dynamics of the coevolution of hosts and their parasites. This is certainly compatible with the major ecological patterns shown by sexual systems, with outcrossed sex being more common in the sea than in freshwater, more common at low than at high latitudes, and generally more common in stable, complex, climax environments where interactions between species are expected to be more frequent and intense (Bell, 1982). However, there is as yet no evidence which conclusively supports a direct causal link between the incidence of parasitism and the rate of recombination. In particular, it has never been demonstrated that a particular parasite has the effect of eliciting, directly or indirectly, a greater rate of genetic recombination in its host. We suggest that such a parasite exists; both the parasite and its effects are well known, but have never been interpreted in the context of the evolution of recombination through host—parasite coevolution. It is in many respects a rather unusual parasite. We shall argue thatB-chromosomes represent highly evolved parasitic DNA, transmitted through the germ line and often eliciting greater rates of recombination in the host genome.
Two new species of Ardeicola Clay, 1935 (Mallophaga, Ischnocera), from African ibises
Authors: Hajela K. P. , Tandan B. K.
Published: June 2009

Two new species of Ardeicola Clay, 1925 (Mallophaga, Ischnocera), A. keniensis and A. africanus, ectoparasites of African ibises, Lampribis olivacea akleyorum and L. rara respectively, are described. These species are closely related to each other, and the characters which distinguish them have been enumerated.

We are most grateful to Dr Theresa Clay, Department of Entomology, British Museum (Natural History), for the loan of material and for reading the typescript.
Introduction to neuropeptides: perspectives for the parasitologist
Authors: O'Shea M.
Published: June 2009

At the cellular and molecular levels, the small and simpler nervous systems of invertebrates do not differ fundamentally from the larger more complex ones of vertebrates. It seems therefore that the special properties of the human brain arise more from the fact that it has ten trillion cellular components than from any unusual properties of the components themselves. By studying invertebrates we can gain insight into what basic functions are performed by the cells and molecules of the nervous system and this will contribute to a more fundamental understanding of what goes on in a system in which the same functions are performed by uncountable numbers of neurones. Invertebrate studies are also important for an entirely different reason; they are interesting and important in their own right. Moreover, a relatively small number of invertebrates are pests; either parasites, vectors of serious parasitic diseases or pests of our agricultural production. It is no accident that most of the methods that are used to control such organisms act on their nervous system. That is because the nervous system is a complex chemical machine which works through a great variety of chemical interactions between a wide diversity of receptors and ligands. Many currently used control methods work because they disrupt these interactions. For this reason I would imagine that the new generation of compounds developed to control invertebrates will depend for their activity on interactions with the nervous system. Since most of the chemical effectors (transmitters, modulators and hormones) in the nervous system are peptides, a number of these newly developed approaches will depend upon a fundamental knowledge of peptidergic systems in parasites. This essay is about peptidergic systems and indicates how we might exploit their vulner-ability to interference.
Sequence differences between histones of procyclicTrypanosoma brucei bruceiand higher eukaryotes
Authors: Bender K. , Betschart B. , Schaller J. , Kämpfer U. , Hecker H.
Published: June 2009

Four histones, a, b, c, d from procyclicTrypanosoma brucei brucei, which show similarities with the amino acid composition of the core histones H3, H2A, H2B and H4, were isolated and cleaved with Endoproteinase Glu-C. The fragments were separated by FPLC reversed phase chromatography and a subset of the fragments (a5, a9, b6, c8, d3, d9, d11) was subjected to sequence analysis. A 54–71% identity was found in the sequences of the fragment c8 and the C-terminal half of H2B and of three fragments of protein d covering the N-terminal half as well as the C-terminal region of H4. The amino acid sequence of the fragment a9 showed a 57 and 54% identity with H3 sequences ofSaccharomyces cerevisiaeandXenopus laevis. Neither the a5 nor the b6 sequence could be aligned with histone sequences of other eukaryotes. The significant differences of 21–48% between theT. b. brucei, histone sequences and those of calf thymus histones, which are more pronounced than the differences ofTetrahymena pyriformisand the higher eukaryote, resulted partially from replacements of amino acids with different properties and indicate specific patterns of histone–histone and/or histone–DNA contact sites in the nucleosome ofT. b. brucei. These differences, together with the lack of a functional histone H1, may be sufficient to explain the lack of a salt-dependent formation of the nucleosome filament into the 30 nm fibre, which reflects alternative methods of organizing and processing the genetic information in the nucleus of the protozoan parasite and which may be of chemotherapeutic significance.
The isolation of viable coccidial sporozoites
Authors: Jackson A. R. B.
Published: June 2009

A method is described by which viable sporozoites of the sheep parasite,Eimeria arloingi, may be obtained in sterile solution and free of any extraneous vegetable matter. Faeces are washed through metal sieves and the oocysts separated by a gravity floatation technique. The oocysts are sterilized and floated free of any remaining faecal debris in a solution of sodium hypochlorite. Sporulation is induced by constant aeration in water. Excystation is effected by incubating firstly under an atmosphere of carbon dioxide and secondly in a solution of trypsin and sheep bile.

I wish to thank Professor H. R. Carne for encouragement and advice, and Mr R. F. Jones for skilful technical assistance.
Coccidia in wild populations of the red kangaroo, Megaleia rufa (Desmarest), and the grey kangaroo, Macropus canguru (Müller)
Authors: Mykytowycz R.
Published: June 2009

The incidence and prevalence of coccidia have been studied in populations of free-living red kangaroos, Megaleia rufa, and grey kangaroos, Macropus canguru, in four geographically distinct areas in Australia.

Two new species of Eimeria—E. wilcanniensis and E. toganmainensis—are described from M. rufa, and five—E. cunnamullensis, E. gungahlinensis, E. purchasei, E. kogoni, and E. hestermani—from M. canguru.

The incidence of coccidia ranged from 6 to 14% in populations of M. rufa and from 26 to 70% in M. canguru. The susceptibility of the animals to coccidia was analysed in relation to the tibia length. Red kangaroos with tibia approximately 360 mm. long and corresponding to an age of about 12 months were found to be most susceptible. No clinical cases of coccidiosis were seen in the field.

Special thanks are due to the owners or managers of the properties on which the kangaroos were sampled; to members of the staff of the Regional Pastoral Laboratory ‘Gilruth Plains’ for their assistance in sampling, and to Messrs E. R. Hesterman, C. Kogon, and D. Purchase, who assisted in the field and the laboratory. Three species of Eimeria have been named after them in acknowledgement of their work. Messrs B. V. Fennessy and J. H. Calaby of this Division kindly read the manuscript.

I wish to thank Dr G. B. Sharman for his permission to work with captive kangaroos in Canberra, and Mr E. Slater who took the photographs.
The helminth parasites of some small mammal communities. I. The parasites and their hosts
Authors: Sharpe G. I.
Published: June 2009

1. A method of trapping small mammals has been described andApodemus sylvaticus, Clethrionomys glareolus, Microtus agrestisandSorex araneuswere captured. The method of trapping has been discussed.

2. A survey of the endoparasites found in the four host species has been produced. The two more common hosts and four of their parasites have been chosen for more detailed study.

3. The infection levels of the parasites in the two hosts have been calculated and compared with other published data.

This work was carried out during the tenure of a Department of Scientific and Industrial Research Studentship. My thanks are due to Dr H. D. Crofton for his very helpful supervision and criticism and to Professor J. E. Harris, F.R.S., in whose department this work was done, for the facilities provided.
The laboratory rearing of Amblyomma sparsum Neumann, 1899
Authors: Walker Jane B. , Parsons B. T.
Published: June 2009

The successful rearing of Amblyomma sparsum, using rabbits as larval and nymphal hosts and either sheep or tortoise for feeding adults, is described and details of the duration of the various stages are given. The life cycle of this tick is compared with that of A. variegatum and A. nuttalli.

The authors are grateful to the Director of the Coryndon Memorial Museum, Nairobi, for the loan of a Leopard Tortoise, and to the Directors of the East African Veterinary Research Organization and of the Veterinary Services, Kenya, for permission to publish this note.
Maximum local helminth parasite community richness in British freshwater fish: a test of the colonization time hypothesis
Authors: Guégan J.-F. , Kennedy C. R.
Published: June 2009

The investigation of Price & Clancy (1983), which demonstrated a significant positive correlation between total helminth species number per host species and geographical range of freshwater fish host species in Britain, was re-examined using a different measure of parasite species richness. Re-calculation of the correlations between the two parameters after controlling for the effect of the composition of the list of fish by excluding, on biological and distributional grounds, 2 species of agnathans and 7 species of introduced teleosts, and for the effect of sampling effort by using helminth richness in the richest component community of each fish species rather than check-list data, reveals no significant relationship between helminth species richness and host range. Habitat and an omnivorous host diet now appear more significant determinants of helminth richness than the accumulation of parasites by predation. The findings provide little support for the interpretation of the relationship between helminth species richness and host range in terms of island biogeographic theory, but do support an alternative explanation in terms of the colonization time hypothesis, i.e. that helminth species richness is related to the time since the fish host arrived in Britain.
Common and rare trout parasites in a small landscape system
Authors: Hartvigsen R. , Halvorsen O.
Published: June 2009

Brown trout (Salmo trutta) from four lakes within an area of approximately 40 km2 were found to harbour nine helminth species. Crepidostomum metoecus could be classified as core species, while Crepidostomum farionis had an intermediate position. All the others could be classified as satellite species. Salmon (Salmo salar) fingerlings were grown to smolts in an earthpond over the summer. The fingerlings became infected with Crepidostomum spp. which may indicate a superior colonization ability in the core species. The results support the ‘rescue effect hypothesis’ rather than the ‘carrying capacity hypothesis’.
Detection ofEchinococcus multilocularisDNA in fox faeces using DNA amplification
Authors: Bretagne S. , Guillou J. P. , Morand M. , Houin R.
Published: June 2009

In order to identifyEchinococcus multilocularisDNA in fox faeces for epidemiological purposes, we have developed a new method to prepare DNA suitable for PCR amplification. DNA isolation from fox excrement was performed according to a novel procedure involving lysis in KOH, phenol–chloroform extraction and a purification step on a matrix (Prep-A-Gene®). The target sequence for amplification was theE. multilocularisU1 snRNA gene. PCR products were indistinguishable for 32 differentE. multilocularisisolates and no signal was observed after ethidium bromide staining with DNAs from other tapeworm species, includingE. granulosus.The sensitivity of amplification was monitored by the addition ofE. multilocularisDNA or eggs to faeces free ofE. multilocularisand was estimated to be 1 egg per 4 g of faeces. PCR products were blotted onto nylon membranes and hybridized with an internal oligonucleotide probe in order to confirm the results. Twenty nine faecal samples from foxes shot in Franche-Comté (East France) were tested. Out of 10 samples from foxes in which noE. multilocularisadult worms could be observed after necropsy, 7 were PCR positive, showing that the PCR test is more sensitive than microscopical examination. Out of 19 samples from foxes harbouringE. multilocularisadult worms, 18 were PCR positive. The remaining PCR-negative sample could be due either to the misidentification of the species of adult worm (E. granulosusandE. multilocularis), or to DNA variation between different isolates ofE. multilocularis. Further work in the field should be initiated in order to confirm these results.
Infection and disease in lymphatic filariasis: an epidemiological approach
Authors: Grenfell B. T. , Michael E.
Published: June 2009

A major question in the study of any parasitic disease is the relationship between infection and clinical disease. The public health importance of lymphatic filariasis has generated a large body of research in this area, both in laboratory studies (Ottesen, 1984,1989; Maizels & Lawrence, 1991) and in the field (Hayashi, 1962; Hairston & Jachowski, 1968; Denham & McGreevy, 1977; Vanamail et al. 1989 b; Bundy, Grenfell & Rajagopalan, 1991; Srividya et al. 1991 b). Despite this, there is still no conclusive explanation for the apparently complex relationship between infection and clinical disease observed in human communities. At least part of the problem may lie in the current impossibility of measuring adult worm burden in vivo (Pichon et al. 1980; Denham & Fletcher, 1987; Das et al. 1990; Grenfell et al. 1990). Although there has recently been significant progress in the development of immuno logical markers for infection status in humans (Ottesen, 1989; Day et al. 1991 a), microfilaraemia is still the most reliable measure of current infection in the field. Studies in endemic areas indicate that, far from there being any simple direct relationship between microfilaraemia and disease status, it is possible to find some individuals with microfilariae in their blood but no disease, and indeed with all other combinations of infection and disease status (Hairston & de-Meillon, 1968; Hairston & Jachowski, 1968; Beaver, 1970; Bryan & Southgate, 1976; Denham & McGreevy, 1977; Pani et al. 1991). Furthermore, the proportions of people in different categories are often observed to vary between endemic areas (Denham & McGreevy, 1977; Day et al. 1991 a).
Malaria: drug use and the immune response
Authors: Targett G. A. T.
Published: June 2009

Malaria is a controllable disease, yet the resources required - human, technical and financial - are massive, and are currently beyond the vast majority of the 96 countries where the disease is endemic. The control measures most widely applied are vector control through spraying or use of insecticide-impregnated bednets, and chemotherapy. The biological problems to add to the resource issues are well known; increasing resistance of anopheline mosquitoes to the most widely used insecticides, and the progressive development of drug resistance in the parasite populations, especiallyPlasmodium falciparum.
Pathways to the impairment of human nutritional status by gastrointestinal pathogens
Authors: Solomons N. W.
Published: June 2009

Gastrointestinal pathogens are of three varieties, those that can, and often do, take the life of the host, those that infect transiently and rarely are life-threatening, and those (parasites) that establish a relatively prolonged residence or colonization of the host's alimentary tract. In the case of the second form, if infections are recurrent, both catabolic effects during the episode and failure to digest foods and/or absorb nutrients result. Similarly, catabolic wastage through activation of the acute phase response, and interference with the host's acquisition of nutrients by maldigestion, malabsorption, intestinal losses and competition with the parasite burden can impair growth and nutrition with helminthic infections. Growth and nutrition with respect to all of the macronutrients and virtually all of the micronutrients have been documented to be adversely affected by gastrointestinal pathogens. For its burgeoning importance as a worldwide health problem, both with the HIV virus as a direct intestinal pathogen and with the opportunistic gut infections occurring in the immunocompromised host, AIDS represents the emerging context of the impairment of nutritional status by intestinal pathogens.
Malarial parasites and antioxidant nutrients
Authors: Levander O. A. , Ager A. L.
Published: June 2009

Susceptibility to oxidative stress is a well-established feature of the malarial parasite. Pharmacologists have taken advantage of this property to design highly effective pro-oxidant antimalarial drugs. Less well appreciated is the fact that nutritional manipulation of host oxidative stress status by dietary means can have a profound effect on the growth of the parasite. In particular, rapid induction of vitamin E deficiency in mice by feeding highly unsaturated fatty acids (fish oil) strongly suppresses plasmodial growth. Likewise, the status of other antioxidant nutrients (e.g., riboflavin or vitamin C) may also influence the course of malarial infection under certain conditions. A combined nutritional pharmacology approach may offer some promise in controlling malaria.
Trans-sialidase, SAPA amino acid repeats and the relationship betweenTrypanosoma cruziand the mammalian host
Authors: Frasch A. C. C.
Published: June 2009

During invasion of multicellular organisms, protozoan parasites expose functional molecules that become targets for the host immune response. Recent research onTrypanosoma cruzi, the agent of Chagas' disease, suggests a new model of how the parasite might deal with this problem. Several antigens ofT. cruzihave tandemly repeated amino acid motifs in molecules with as yet unknown functions. In two cases, these repeats are in molecules with a defined structure or function. Both proteins are implicated in the invasion of host-cells by the parasite. One of these is the core protein of a putative mucin-like glycoprotein that has Thr/Pro–rich repeats which, by themselves, might define the structure of a highlyO-glycosylated molecule. The other protein is SAPA/trans-sialidase/neuraminidase, a molecule able to transfer sialic acid, that has so far only been described in trypanosomes. The amino acid repeats present in SAPA/trans-sialidase/neuraminidase are unrelated to the enzymic activity and constitute an immunodominant C–terminal domain. The N–terminal domain of SAPA/trans-sialidase/neuraminidase controls the enzymic activity since a recombinant molecule lacking the repeats conserves trans-sialidase activity. That both domains are functionally independent is also indicated by experiments that show that antibodies directed against the amino acid repeats are unable to inhibit trans-sialidase activity. A large number of proteins having trans-sialidase related sequences but lacking enzymic activity are also present in the surface membrane of the parasite. The immunodominant SAPA/trans-sialidase/neuraminidase repeats, together with the complex network of cross-reacting epitopes present in related but enzymically inactive proteins might contribute to the delay in mounting an effective antibody response. However, antibodies neutralizing trans-sialidase activity are generated later during the infection. These antibody specificities are directed to the enzymic domain of the molecule and might contribute to the control of parasite dissemination after the early period of the infection.
The gull-tapeworm, Diphyllobothrium dendriticum and neuropeptide F: an immunocytochemical study
Authors: Gustafsson M. K. S. , Halton D. W. , Maule A. G. , Reuter M. , Shaw C.
Published: June 2009

Neuropeptide F (Moniezia expansa) immunoreactivity (NPF-IR) has been detected in the nervous system of plerocercoid and adult stages of the gull-tapeworm Diphyllobothrium dendriticum, using immunocytochemical methodology. The application of the antiserum for this authentic flatworm neuropeptide to whole-mounts and frozen sections of the worm has resulted in new information about its neuroanatomy. Thus, at regular intervals, transverse nerves extend from the main nerve cords laterally, joining the longitudinal lateral minor cords in the cortical parenchyma. In the adult worm, the transverse nerves are located at the posterior border of each proglottis. The medullary parenchyma lacks NPF-IR. The NPF-immunoreactive cell bodies are bi- to multipolar and preferentially located in the peripheral nervous system, in close association with the holdfast musculature of the scolex and the extensive body musculature. NPF-IR was observed in the innervation to the muscular ducts of the reproductive system. The pattern of NPF-IR was compared with that recorded for RFamide- and 5-HT-IR and double-immunostaining has revealed separate populations of serotoninergic and peptidergic neurones.
Changes in parasite aggregation with age: a discrete infection model
Authors: Quinnell R. J. , Grafen A. , Woolhouse M. E. J.
Published: June 2009

We present a discrete time model for age-related changes in the mean and variance of the number of helminth parasites per host. We assess the degree of aggregation as the negative binomial parameter,k, and use the model to examine the influence of various factors on changes in aggregation with host age: discrete versus continuous infection; the degree of predisposition to infection; infection rate; parasite survival rate; and the variance in exposure to infective stages. The model can produce both increases and decreases inkwith host age. However, with parameter values typical of many human helminth infections, a monotonic increase ink(decrease in aggregation) with age is predicted. With an age-dependent infection rate, convex relationships betweenkand age are possible. These predictions are consistent with data from field studies, but differ from those of previous models which have suggested thatkis independent of host age in the absence of density dependence in parasite population dynamics. Differences between the models, and some difficulties in the interpretation of field data, are discussed.
The effect of the sulphoxide metabolite of triclabendazole (‘Fasinex’) on the tegument of mature and immature stages of the liver fluke, Fasciola hepatica
Authors: Stitt A. W. , Fairweather I.
Published: June 2009

The effects of the novel benzimidazole, triclabendazole (TCBZ) (‘Fasinex’, Ciba-Geigy), in its active sulphoxide metabolite form (TCBZ-SX), on the tegumental ultrastructure of Fasciola hepatica were determined in vitro by transmission electron microscopy (TEM), using both intact flukes and tissue-slice material. At a concentration of 15 µ/ml, the tegument of the whole adult fluke showed ultrastructural changes only after prolonged time-periods, with vacuolation at the base of the syncytium and accumulation of T2 secretory bodies in the tegumental cells. At a concentration of 50 µ/ml, with both whole flukes and tissue-slices, the tegument appeared extremely abnormal with accumulation of secretory bodies towards the base of the syncytium. With longer incubation times, the tegument was completely sloughed away and the tegumental cells became synthetically inactive. The tegument of the 3-week-old juvenile became progressively convoluted at the apex, while in the basal regions there was severe vacuolation. In the tegumental cells, there were accumulations of T1 secretory bodies. These results confirm TCBZ as a potent fasciolicide, being very effective in disrupting the fluke tegument. They may go some way to explain the mode of action of this important fasciolicide.
Characterization of the effector mechanisms of a transmission-blocking antibody upon differentiation ofPlasmodium bergheigametocytes into ookinetesin vitro
Authors: Ranawaka G. R. R. , Alejo-Blanco A. R. , Sinden R. E.
Published: June 2009

The transmission-blocking monoclonal antibody 13.1, which recognizes the ookinete surface antigen Pbs21 ofPlasmodium berghei, and an IgG2a isotype control antibody 26.37 were purified by caprylic acid and ammonium sulphate precipitation. Fab fragments were prepared by papain digestion. IgG but not Fab from antibody 13.1 reduced ookinete formation byP. bergheiin culture by as much as 94% at a concentration of 100 μg/ml. There was little difference in antibody efficacy in the range 6·25–400 μg/ml in this assay. The parasite was most sensitive to antibody activity in the first 6–9 h of culture, i.e. the gamete/zygote and early retort stages. Peripheral blood leucocytes (PBL) were essential to achieve maximal inhibition by mAb 13.1 (activity was abrogated totally if PBL were removed). Together the data suggest that one of the mechanisms of action of this antibody is antibody-mediated PBL killing. Phagocytosis of parasites was noted in these experiments in all cultures. We have not attempted in this study to distinguish between Fc-mediated opsonization, as opposed to antibody-dependent cellular cytotoxicity.
Density-dependent regulation of the growth of the hookworms Necator americanus and Ancylostoma ceylanicum
Authors: Norozian-Amiri S. M. B. , Behnke J. M.
Published: June 2009

Laboratory bred DSN hamsters were exposed to varying doses of infective larvae of Ancylostoma ceylanicum (orally) or Necator americanus (percutaneously) and were autopsied at times which corresponded to a period immediately before cessation of growth of worms or soon afterwards. A total of 829 (404 male and 425 female) A. ceylanicum and 1582 (781 male and 801 female) N. americanus were measured. At worm burdens of fewer than 100, the length of A. ceylanicum appeared to increase with infection intensity and no evidence was found that growth was retarded under crowded conditions. In an experiment comparing directly low (mean worm burden = 22) and heavy infections (mean worm burden = 180) significant negative associations between both weight and width, and worm burden were detected, but length again increased with worm burden. In contrast, 5 experiments with N. americanus indicated negative relationships between measures of worm size (length, width, wet and dry weight) and worm burden. It was concluded that N. americanus is subject to regulation by density-dependent processes within the host while A. ceylanicum is not sensitive to the same degree.
The effects of Onchocerca lienalis infection on vitellogenesis in the British blackfly, Simulium ornatum
Authors: Renshaw M. , Hurd H.
Published: June 2009

We have previously described the major yolk protein, vitellin, in the British blackfly Simulium ornatum Meigen. Here we demonstrate that vitellogenin, synthesized in the fat body and secreted into the haemolymph, is composed of subunits with the same approximate molecular weight as vitellin, namely 200 and 68 kDa. Simulium ornatum is the natural vector for the cattle filarial nematode Onchocerca lienalis Stiles, which induces host fecundity depletion. A significant reduction in ovarian vitellin content was associated with infection by intrathoracic injection of 20 O. lienalis microfilariae immediately after blood-feeding. Fat body synthesis of vitellogenin was significantly reduced as early as 8 h post-infection in comparison with sham-injected flies. When total haemolymph protein from infected and sham injected flies was compared, titres were significantly depressed 6 h post-infection. However, later in the infection, titres were elevated by 30%, the major component being vitellogenin. The injection of dead microfilariae had no effect. An infection burden of a single parasite caused a significant reduction in ovarian protein content in comparison with shams, but no further significant decrease was observed as the parasite burden was increased from 5 to 20. Possible mechanisms underlying the disturbance of Simulium reproductive physiology are proposed.
Responses of the fish ectoparasite Salmincola edwardsii (Copepoda) to stimulation, and their implication for host-finding
Authors: Poulin R. , Curtis M. A. , Rau M. E.
Published: June 2009

The short-lived infective copepodid stages of the copepod Salmincola edwardsii, ectoparasitic on brook trout, Salvelinus fontinalis, are under strong selective pressure to evolve efficient host-finding mechanisms. In laboratory experiments, we quantified the effects of visual and mechanical stimulation on the activity of the copepodids. We found that shadows passing above the copepodids and shock waves passing through the water generated marked increases in the rate and length of upward swimming bursts, which resulted in more time spent suspended in the water column and greater distances travelled. However, we found no strong evidence for a relationship between the magnitude of the copepodids' response and the intensity of stimulation. Although these responses are not host-specific, they allow the parasites to conserve their limited energy stores by increasing their host-finding activity only when potential hosts are nearby.