bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the immunity of sheep toOesophagostomum columbianum: effects of low-protein diet on resistance to infection and cellular reactions in the gut
Authors: Dobson Colin , Bawden Richard J.
Published: June 2009

AdultOesophagostomum columbianumpopulations were larger in sheep fed low-protein diets than in adequately fed animals. Diet did not influence the numbers of larva which became established in sheep. Sheep fed high-protein diets eliminated more worms and were more immunologically competent than poorly fed animals. More encapsulated larvae, showing arrested development, were found in adequately fed sheep than in those fed low-protein diets. AdultO. columbianumproduced eggs at an earlier time after infection in poorly fed sheep than worms in well fed sheep. More eggs/female worm were produced in sheep on a low-protein diet compared with the number of eggs produced in well fed hosts over the last week of the infection. The effects of immunity on the behaviour of the worm in both host diet groups is discussed.

There was a greater cellular proliferation in the intestines of infected adequately fed sheep than in infected animals on low-protein diets. These changes were most pronounced in the large intestine where the adult parasites were found. The macrophage-lymphocyte series of cells underwent hyperplasia in well fed animals but these changes were reduced, particularly among the plasma cells, in sheep fed low-protein diets. Increased mucin and mast cell counts were observed in sheep on high-protein, but not in hosts on low-protein diets: the intestinal populations of eosinophil and globule leucocytes were also reduced in poorly fed sheep.

The relationship of these various cellular reactions and their effect on the protective immunity of sheep toO. columbianumis discussed. It was concluded that the increased susceptibility of protein deprived sheep toO. columbianuminfections was associated with malfunctions of the innate immunity of the gut, involving decreased peristalsis and failure of the mucin cell response, and with reduction of the adaptive immune response which was reflected by impoverished lymphocyte and plasma cell reactions, and possibly with poor cooperation between sensitized lymphocytes, antibodies and the mast cell-granulocyte effector mechanisms in protective immunity.
A comparative study of the glandular and excretory systems of the oncomiracidia of the monogenean skin parasitesEntobdella hippoglossi, E. diademaandE. soleae
Authors: Kearn Graham C.
Published: June 2009

A comparison of the oncomiracidia of the monogenean skin parasitesEntobdella hippoglossifrom the halibut (Hippoglossus hippoglossus), E. diademafrom the sting ray (Dasyatis pastinaca) andE. soleaefrom the skin of the common sole (Solea solea) has revealed the presence of ‘body gland cells’, all of which have openings on the ventral or lateral surfaces of the larvae. In all three species there are two pairs of glands lying in the posterior region of the body proper with long ducts extending into the haptor and opening on its ventral surface. In addition to these two pairs of glands there are seven other pairs of body glands inE. hippoglossi, six pairs inE. diademaand two pairs inE. soleae.InE. soleaeall the ‘body gland cells’ are poorly developed in the oncomiracidium and are more conspicuous in post-oncomiracidia. The fate of the ‘body gland cells’ during post-oncomiracidial development has been studied inE. soleae, and their possible functions are discussed. The glands in the head region (anterior median, posterior median and lateral head glands) are similar in all three species. Gland cells associated with the alimentary system are less easy to observe but differences between the three species appear to be small.

In the oncomiracidia of all three species the number of flame cells and their distribution are the same, but the oncomiracidia ofE. hippoglossiandE. diademahave loops in the excretory ducts anterior to the bladder and the bladders ofE. diademacontain refringent bodies.

The oncomiracidial eyes ofE. hippoglossiandE. soleaehave lenses but the lenses are greatly reduced in the oncomiracidia ofE. diadema.In the three larvae there are small but characteristic differences in the shapes of the accessory sclerites.

The oncomiracidium ofE. hippoglossihas not previously been described.
The ultrastructure of the tegument of the daughter sporocyst of Microphallus similis (Jäg., 1900) (Digenea: Microphallidae)
Authors: Popiel Irene , James B. L.
Published: June 2009

In the fully formed daughter sporocyst of Microphallus similis (Jäg.) the tegument is divided into a wide, outer cellular epithelium and a narrow, inner electron-dense anucleated microvillous syncytium. The narrow subtegument consists of circular and longitudinal muscle, nervous, synthesizing and germinal cells. It is suggested that during development of the tegument, an undifferentiated nucleated syncytium becomes divided by the formation of membranes between the nuclei and between the narrow, inner electron-dense microvillous and the outer cellular regions. The outer nucleated region of the tegument is homologous to the nucleated investing syncytium which surrounds redial and cercarial embryos and which is shed later in development. The retention of the nucleated region in some daughter sporocysts is, therefore, an example of paedogenesis.
Uptake of [14C]oxamniquine by Schistosoma mansoni
Authors: Woolhouse N. M. , Kaye B.
Published: June 2009

The uptake and retention of drug-related material by Schistosoma mansoni was studied in the mouse host following a single oral or intramuscular does (50 mg/kg) of [14C]oxamniquine. Male worms took up more labelled material than did female worms but the amount in each particular sex of worm was found to be similar after both routes of administration. Exposure of worms was therefore independent of the route of administration. Six days after drug administration, at the time of an hepatic shift, significantly more drug-related material* was present in male worms than in female worms. Examination of worms recovered from mice 4 h after treatment showed that metabolites of oxamniquine constituted 70–90% of the drug-related material present in the worms. Both sexes of worms were able to take up matebolites of oxamniquine win vitro.
Euzetrema knoepffleri: evidence for a synchronous cycle of the gastrodermal activity and an ‘apocrine–like’ release of the residues of digestion
Authors: Fournier Annie
Published: June 2009

Euzetrema knoepffleri (Monogenea, Monopisthocotylea), an endoparasite of Euproctus montanus (Amphibia, Urodela), has a partially haematophagous diet, resembling that of the Polyopisthocotylea. In spite of this, the ultrastructural characteristics of the gastrodermis are typical of Monopisthocotylea. As in the Monogenea already described, digestion is intracellular with a lysosomal process, but two original features are evident. First, there is a cyclic activity of all the digestive cells during digestion with a synchronization of events, which enables two characteristic stages to be distinguished. Secondly, the elimination of the waste is similar to an ‘apocrine’ process, in which the apical portion of cytoplasm filled with residual bodies or the entire cell is released into the caecal lumen.
Humoral encapsulation in Diptera (Insecta): comparative studiesin vitro
Authors: Vey A. , Götz P.
Published: June 2009

The humoral encapsulation reaction of larvae ofChironomushas been reproduced and studiedin vitro. This reaction is activated by entomogenous fungi and certain foreign bodies as well as by nematodes. The different stages of encapsulation and the duration of the process have been determined. In the larvae of a given species of Chironomidae encapsulation does not vary with age or sex. In contrast, the duration of the process differs according to the species of Chironomidae and is modified by temperature or by parasitism of the host by Mermithidae.

The capsules contain melanin. Their formation is prevented by glutathion, an inhibitor of phenoloxidase.

The humoral type of encapsulation also occursin vitroin the haemolymph of larvae of the nematocera families, Culicidae and Chaoboridae. However, the reaction of these insects differs in the amount, distribution and pigmentation of the capsular material.

The results demonstrate similarities between humoral and cellular encapsulation.
The structure of the egg-shell of Aspiculuris tetraptera Schulz (Nematoda: Oxyuroidea)
Authors: Wharton D. A.
Published: June 2009

The egg of Aspiculuris tetraptera is an ellipsoid measuring 93 × 40 µm. The shell consists of 5 layers: the external uterine layer, internal uterine layer, vitelline layer, chitinous layer and the lipid layer. This nomenclature is based upon the formation and histochemistry of the shell layers. The internal uterine layer contains a system of interconnecting spaces, partly filled by uterine secretion, which open to the exterior of the egg via breaks in the external uterine layer. The surface of the egg is covered by a system of interconnecting grooves. Freeze-etching reveals that the internal uterine layer is open to the exterior via pores, which open into the grooves. Rod-shaped particles are also revealed in the external uterine layer. The operculum of the egg consists of a modification of the uterine and chitinous layers of the shell.
Studies on the mode of action of beclotiamine on Eimeria tenella
Authors: Matsuzawa Toshiaki
Published: June 2009

The thiamine antagonist beclotiamine showed anticoccidial activity against Eimeria tenella, although metabolites and related substances were inactive. Oocyst production in experiments employing unilateral caecal ligation suggested that the drug reached parasitized cells by downward movement through the intestinal lumen, rather than by absorption and systemic transport. In chickens given 100 p.p.m. beclotiamine in the feed over a period of 7 days, duodenal drug concentrations of approximately 5·8 p.p.m. were achieved and maintained, while concentrations in the caeca were lower, but gradually increased to 1·2 p.p.m. Caecal levels were slow to fall following drug withdrawal, whereas duodenal levels showed an immediate decrease. [3H]thiamine absorption from the caeca of normal chicks or of chicks infected with E. tenella was inhibited by oral administration of beclotiamine. Pyrithiamine showed slight anticoccidial activity at 30 p.p.m. as did 2,4-dinitrophenol (2,4-DNP) at 100 p.p.m. A combination of 40 p.p.m. beclotiamine and 200 p.p.m. 2,4-DNP was quite effective although weight gains were not as good as with 120 p.p.m. beclotiamine alone.
Neuromuscular physiology of Grillotia erinaceus metacestodes (Cestoda: Trypanorhyncha) in vitro
Authors: Ward S. M. , Allen J. M. , McKerr G.
Published: June 2009

Isometric tension recordings and the single sucrose-gap technique were used to record mechanical and electrical activity from Grillotia erinaceus metacestodes in vitro. Both complete preparations and those cut longitudinally (to allow access of the bathing medium to the region of the somatic muscle) showed spontaneous contractions of frequency ≃ 1/min in Hanks’ Balanced Salt Solution (HBSS) at 13 °C. Changing the pH, temperature or osmolarity of the HBSS did not improve the activity but rather abolished it at extremes of these variables, so confirming the adequacy of the experimental environment for further work. The neurotoxin tetrodotoxin (TTX; 3 × 10−6 M) failed to abolish or modify these spontaneous contractions although excitatory and inhibitory responses to 5-hydroxytryptamine (5-HT) and acetylcholine (ACh) respectively were demonstrated. Electrical recordings showed that spontaneous contractions were mediated by slow membrane depolarizations upon which spike-like potentials were often superimposed. 5-HT was shown to mediate its excitatory effect via membrane depolarization and an increase in the frequency of both slow depolarization and spikes. In contrast, inhibition by ACh was accompanied by membrane hyperpolarization and loss of all regenerative electrical activity. Electric field stimulation of the preparation using a range of stimulus parameters failed to demonstrate a functional motor innervation to the somatic muscle.
Action of praziquantel on Grillotia erinaceus metacestodes (Cestoda: Trypanorhyncha) in vitro
Authors: Ward S. M. , Allen J. M. , McKeer G.
Published: June 2009

Isometric tension recordings and the single sucrose-gap technique were used to record mechanical and electrical activity of somatic muscle from G. erinaceus metacestodes in vitro. Praziquantel (≥ 10−6 M) raised baseline tension and largely abolished spontaneous fluctuations in tension. The effect of the drug was critically dependent on the presence and availability of calcium in the bathing medium. In calcium-free solution or in the presence of manganese or lanthanum (10 mm) praziquantel failed to induce a rise in baseline tension. Electrical recordings of somatic muscle activity showed the action of praziquantel to be accompanied by membrane depolarization and loss of slow depolarizations and spikes. Tegumental membrane potential, as measured by microelectrodes, was not affected by the drug. These results suggest that in vitro praziquantel causes contraction of the somatic muscle of G. erinaceus by membrane depolarization and influx of extracellular calcium.
Genetic control of liability to infection withNematospiroides dubiusin mice: selection of refractory and liable populations of mice
Authors: Brindley P. J. , Dobson C.
Published: June 2009

Quackenbush strain and wildMus musculuswere assayed for their liability to primary infection with 100 LaNematospiroides dubiususing an experimentally derived selection index. Refractory and liable colonies of mice were established over 5 generations. Liability toN. dubiusinfection was found likely to be controlled by several genes; the heritability (h2) of this trait was estimated at 0·45. Positive linear correlation was found between the number of parasite eggs voided and the number of adultN. dubiusrecovered, negative correlation between the pre-patent period of infection in days and the number of parasite eggs voided and positive correlation in 2 of 5 generations between live mouse body weight and the number of adultN. dubiusrecovered. Further, positive correlation was found between the liability of female mice toN. dubiusand their progeny litter size number. The genetic mechanisms controlling the liability trait and the possible evolutionary significance of these results are discussed.
An improved technique for the cryopreservation of Onchocerca microfilariae
Authors: Ham P. J. , Townson S. , James E. R. , Bianco A. E.
Published: June 2009

Experiments describe the use of ethanediol to store Onchocerca microfilariae in liquid nitrogen. The technique involves a 2-stage incubation of the parasites at 37 °C and 0 °C in ethanediol, before rapid cooling to − 196 °C. Viability has been assessed by motility, by migration in a proxy host and by development to the infective stage in the insect vector. A total of 71–79% of the cryopreserved microfilariae was shown to be viable compared to unfrozen controls. The technique is simple, inexpensive and very effective when compared to previous cryopreservation procedures for microfilariae and should be particularly suited for use under field conditions.
The initial stages of infection of cattle cells with Theileria parva sporozoites in vitro
Authors: Stagg D. A. , Dolan T. T. , Leitch B. L. , Young A. S.
Published: June 2009

Large numbers of Theileria parva sporozoites were separated from Rhipicephalus appendiculatus adult ticks by filtration and were then concentrated by centrifugation. The sporozoites were incubated at 37 °C with leucocytes from 6 cattle of Bos indicus and B. taurus types. Giemsastained smears and living preparations under interference contrast microscopy were used to follow the course of the infection of the leucocytes with sporozoites. Sporozoites were seen to attach rapidly to about 25% the leucocytes which they penetrated. After penetration by the sporozoites the morphology of the cells changed to show an increase in cytoplasm and an enlargement of the Golgi apparatus, with which the parasite appeared to become associated. The early intracellular or preschizont stages resembled Babesia parasites. From day 3, the parasite showed the typical morphology of the macroschizont of T. parva. Multiple infections were frequent and up to 8 schizonts were observed arranged around the Golgi apparatus. Multiply infected cells did not survive in culture but some of the cells infected with a single parasite divided to produce 2 infected daughter cells and infected lymphoblastoid cell lines were established in all 21 attempts.
Response of hypersensitized guinea pigs to the feeding ofAmblyomma americanumticks
Authors: Brown S. J. , Knapp F. W.
Published: June 2009

Guinea pigs acquired resistance to the feeding of immatureAmblyomma americanumticks after a single infestation. The initial larval and nymphal feedings resulted in cumulative mortalities of 27·2 and 28·9%, respectively. The second and third larval infestations yielded cumulative mortalities of 50·5 and 52·4%, compared to 18·9 and 24·4% cumulative mortality from controls. Second and third nymphal feedings resulted in 75·7 and 73·4%, and ticks from controls exhibited 36·6 and 34·7% cumulative mortality. The development of host resistance adversely affected tick feeding and resulted in abnormally coloured ticks and a protracted moulting period with a marked decrease in moulting ability. Histological examination of tick feeding sites on guinea pigs challenged twice revealed greater cavity and lesion sizes in hosts fed upon by nymphs than larvae. The primary cell type within these feeding sites were basophils at 12 h post-attachment, but by 72 h post-attachment eosinophils were dominant. The upper epidermal layer adjacent to both larval and nymphal feeding ticks had accumulations of basophils with a few eosinophils. Lymphocytes may have been involved in the resistance response because local lymph nodes in resistant hosts were much larger than in uninfested and singly infested hosts. Some of these nodes had secondary germinal centres.
Trypanosoma (Schizotrypanum) assiutis sp.nov. from the house mouse Mus musculus, with a comparative study on Trypanosoma (Schizotrypanum) vespertilionis of the Egyptian bat Vesperugo kuhli
Authors: Fahmy M. A. M. , Abedl-Rahman A. M. , Khalifa R.
Published: June 2009

On examination of a house mouse (Mus musculus) trapped in Rifa village (Assiut Governorate), a Trypanosoma cruzi-like trypanosome was encountered which differed from the cruzi-like trypanosomes of local bats. It appeared to be a hitherto unknown species for which the name Trypanosoma (Schizotrypanum) assiutis sp.nov. is suggested.
The measurement ofAscaris suumprotein by radioimmunoassay in sera from patients with helminthiasis and with gastrointestinal diseases
Authors: Tanaka K. , Kawamura H. , Tohgi N. , TsujI M. , Miyachi Y. , Miyoshi A.
Published: June 2009

In this study, we have developed a reliable radioimmunoassay (RIA) forAscaris suumprotein (Asp) and have measured the serum concentration of Asp in control subjects and in patients with helminthiasis and a variety of gastrointestinal diseases. The cross-reactivities of Asp antibody with other helminth worm antigens were also measured by RIA.Ascaris lumbricoidescontained approximately the same amount of Asp antigenic substance as didAscaris suum. Toxocara canishad a high concentration of a substance partially cross-reactive with Asp. Small amounts of substance cross-reacting with Asp were also exhibited by Anisakis larvae,Schistosoma japonicumandTaenia saginata. However, no cross-reactivities ofFasciola hepaticaandParagonimus westermaniwith Asp were observed in this study. Almost all the serum levels of Asp from normal control subjects were below the sensitivity of this RIA (10 ng/ml). High concentrations of Asp were observed in sera from patients with ascariasis (64.5±18.8 ng/ml: mean ± S.E.), anisakiasis (75.2±28.0 ng/ml), toxocariasis (78.4±31.3 ng/ml) and schistosomiasis japonica (14.3±3.4 ng/ml). Asp levels in sera from patients with other helminthiasis were not significantly high. From these findings, it was suggested that RIA for Asp may not be specific for diagnosis of ascariasis, but might be a suitable screening method for patients with some kinds of helminthiasis. Interestingly, high concentrations of Asp were also observed in sera from patients with ulcerative colitis (24.8±2.5 ng/ml) and Crohn's disease (19.8±5.2 ng/ml), but Asp levels from 7 other gastrointestinal diseases seemed not to be significantly high. These findings remain unexplained but may derive from cross-reactivities between helminthic and gut mucosal antigens.
In vitro feeding of Dermacentor andersoni (Stiles): effects of histamine and other mediators
Authors: Paine S. H. , Kemp D. H. , Allen J. R.
Published: June 2009

Female Dermacentor andersoni were induced to feed on defibrinated bovine blood through fixed mouse skin membranes. Their feeding behaviour was recorded electronically, the tick being incorporated into the circuit and acting as a variable resistor during the periods of sucking, salivation and rest. Recordings of the feeding behaviour of these ticks were similar to those of ticks feeding on rabbits. Known concentrations of histamine, serotonin, dopamine, prostaglandin E1 and prostaglandin F2α were added singly or in combination to the feeding medium of ticks attached to the mouse skin membrane. Addition of both histamine and serotonin was followed by a significant reduction in the amplitude or recordings associated with sucking and salivation. The concentration of mediators producing this effect was less than 10 mM, a concentration comparable to that of histamine found locally in the skin of tick-resistant guinea-pigs. Comparisons are made between the effects produced by these mediators in ticks and the effects of serotonin and other amines known to produce modulation of complex behaviour patterns in other invertebrates.
Patterns of sexual reproduction among parasitic platyhelminths
Authors: Nollen P. M.
Published: June 2009

Previous studies on the spermatogenesis and oogenesis of digeneans, monogeneans and cestodes are reviewed, including those in which isotopic labelling techniques have been utilized in order to determine the temporal duration of spermatogenic development stages. Similar labelling experiments have also provided information on the development and movement of oocytes in the female reproductive tract as well as indicating patterns of cell division and development in vitelline glands. The literature relating to the inseminative behaviour of parasitic platyhelminths is considered from a number of viewpoints including the patterns of cross-and self-insemination that occur in hermaphroditic digeneans, the mating behaviour of dioecious schistosomes, spermatophore production and insemination among monogeneans and the inseminative behaviour of polyzoic cestodes. The implications of selfing among parasitic platyhelminths are considered with respect to possible genetically deleterious consequences. In addition, consideration is given to the mechanisms underlying the fact that some species require cross-insemination or at least the presence of another worm in order to undergo normal growth and sexual development. Finally, experimental studies are reviewed which shed light on the strength of the barriers against hybridization that exist between well-defined species of parasitic platyhelminths.
Plasmodium gallinaceum and subsequent Eimeria acervulina infections in chickens are not synergistic
Authors: Williams R. B.
Published: June 2009

Twenty-three years ago, the first and only report of synergism between malarial and coccidial infections in chickens was published. In view of the potential commercial importance of this possible parasitic interaction in some parts of the world, and the lack of further supporting publications, this disease complex has now been reconsidered. An experiment on Plasmodium gallinaceum and Eimeria acervulina revealed no interaction of any kind between these species and a re-examination, with statistical analysis, of the raw data on which the original publication was based shows that no evidence of synergism between malarial and coccidial infections in chickens has so far been produced.
The induction of specific immunity againstSchistosoma japonicumby exposure of mice to ultraviolet attenuated cercariae
Authors: Moloney N. A. , Bickle Q. D. , Webbe G.
Published: June 2009

Mice can be partially protected againstSchistosoma japonicumby prior exposure to ultraviolet (UV)-attenuated infections which fail to survive to the adult stage and produce no overt pathology in the host. Optimum resistance was induced by parasites exposed to 40 seconds of UV, significantly lower levels of resistance being stimulated by both shorter and longer exposures. No consistent relationship between the degree of resistance induced and the number of irradiated cercariae given could be demonstrated and equivocal results were obtained when comparing the efficacy of single and multiple vaccinations. Vaccinations with UV-attenuated cercariae given intraperitoneally (i.p.) were as efficacious as those given percutaneously but mice were as or more resistant to challenges given by the i.p. route, the possible reasons are discussed. There was no observed delay in the migration of the challenge, vaccinated mice being as resistant when perfused 6 or 3·5 weeks after challenge. Vaccination was species specific since mice exposed to either UV-attenuatedS. japonicumcercariae or gamma-attenuatedS. mansonicercariae were resistant to homologous but not heterologous challenge.
Possible evidence for mortality induced by the parasite Apatemon gracilis in a population of brook sticklebacks (Culaea inconstans)
Authors: Gordon D. M. , Rau M. E.
Published: June 2009

Regular samples made on the 1978 cohort of brook sticklebacks (Culaea inconstans) from a swamp in Ile Perrot, Quebec, Canada were examined for Apatemon gracilis metacercariae. The prevalence of the parasite rapidly reached 100% in the fish population. The mean parasite burden increased from zero to a plateau of about 44 parasites/fish. Over-dispersion of the frequency distribution of parasites in the fish host, as measured by variance to mean ratios, increased to a peak and then decreased significantly while the mean parasite burden remained constant. The effects of parasite burden on the survival of the stickleback host are discussed, as well as the validity of the use of changes in over-dispersion for demonstrating parasite-induced mortality.
The structure and formation of the egg-shell of Syphacia obvelata Rudolphi (Nematoda: Oxyurida)
Authors: Wharton D. A.
Published: June 2009

The egg of Syphacia obvelata is a flattened elipsoid. The egg-shell consists of 5 layers: external uterine layer, internal uterine layer, vitelline layer, chitinous layer and lipid layer. An operculum is present at one pole of the egg. The opercular groove consists of a break in the uterine layers and the modification of the chitinous layer by the deposition of lipoprotein material. On the curved side of the egg the uterine layers are modified to form alternate ridges and depressions. Discrete spaces are present in the internal uterine layer between the ridges. These are open to the exterior via pores in the external uterine layer. The structure of the uterine layers is quite different on the flattened side of the egg. The morphology of the reproductive system and the formation of the egg-shell is described. It is suggested that the complex structure of the uterine layers of oxyurids forms by a self-assembly process.
The migration and development of Filaroides hirthi larvae in dogs
Authors: Georgi Jay R. , Fahnestock Glenn R. , Bohm Marguerite F. K. , Adsit Jane C.
Published: June 2009

The development of Filaroides hirthi has been shown to proceed through all 5 stages in the lungs of experimental dogs and the attendant morphological changes are described and illustrated. These observations are interpreted as proof that the unhatched larva of F. hirthi is the 1st stage and that the 1st stage is infective. Moults occurred at approximately 1, 2, 6 and 9 days after infection in the lung tissue. Larvae also developed in vitro to the doubly ensheathed 3rd stage which is the stage achieved by heteroxenous metastrongyloids in their molluscan intermediate hosts. The arrival of 1st-stage larvae in the lungs as early as 6h after oral administration and the anatomical distribution of larvae during the first 24 h indicates that larvae are transported from the alimentary tract to the lungs by way of the hepatic portal circulation, the mesenteric lymphatic drainage, or both. First-stage larvae and eggs containing 1st-stage larvae, when injected into the jugular vein, developed into adult F. hirthi lung- worms in the usual 5 week pre-patent period. This was interpreted as demonstrating that the canine alimentary canal, although undoubtedly the normal portal of entry, is not a site of reactions indispensable to the activation or development of the larvae. Eggs containing 1st-stage larvae, when introduced by jugular and portal venous and mesenteric lymphatic routes, yielded equivalent numbers of adult lungworms indicating that neither the hepatic capillary bed nor the mesenteric lymph nodes presented quantitatively significant impediments to their passage. The question is raised whether the mesenteric lymphatics really are the exclusive migration pathways of certain other species of metastrongyloid larvae. The suggestion is made that conventional studies based on the anatomical/time distribution of larvae be supplemented by intravascular experiments like those described in this report, to provide an independent line of evidence.
Parasites inBulinus senegalensis(Mollusca: Planorbidae)and their detection
Authors: Wright C. A. , Rollinson D. , Goll P. H.
Published: June 2009

Isoelectric focusing studies on enzyme variation between populations of the snailBulinus senegalensisrevealed that parasitic infections in the snails contributed additional bands of enzyme activity, particularly in the glucose phosphate isomerase (GPI) and malate dehydrogenase (MDH) systems. The patterns due to the parasite enzymes were, in most cases, clearly distinct from those of the host and different from each other. Parasites encountered includedSchistosoma haematobium,S. bovis,Paramphistomum microbothrium, another amphistome probably belonging to the group which infect amphibians,Echinostoma revolutum, another echinostome (probablyEchinoparyphiumsp.), strigeids, xiphidiocercariae (these were resolved into 3 distinct types by the enzyme data) and ciliate protozoa. The 7 host populations which were examined showed marked differences in both the prevalence and variety of their parasitic infections and these variations were tentatively related to environmental differences in their respective habitats and to the nature of human contact patterns. Seasonal changes in the parasite fauna were also noted and some of the implications of the parasite load on the host population are briefly mentioned.
The attachment of cercariae of an ectoparasitic digenean,Transversotrema patialensis, to the fish host: behavioural and ultrastructural aspects
Authors: Whitfield P. J. , Anderson R. M. , Moloney N. A.
Published: June 2009

The behaviour which enables the cercariae of the ectoparasitic digenean,Transversotrema patialensis, to establish themselves on the surface of their fish hosts has been described experimentally using anaesthetized fish. Specialized regions of the cercarial tail, the arm processes, seem to be adapted for both specific recognition of, and rapid attachment to, the outer surface of a fish. Each arm process bears an array of nine ciliary sensory structures, the mammiform receptors, which have been tentatively identified as contact chemoreceptor organs involved in host recognition. Also present on each arm is an adhesive pad that mediates the initial attachment to the host. It is a differentiated region of the distal cytoplasm of the epidermal syncytium which invests the whole arm process. The cytoplasm of the pad region contains membrane-bounded adhesive granules, the contents of which are released during activation of the pad.
Intracellular digestion and cellular defecation in a monogenean, Diclidophora merlangi
Authors: Halton D. W.
Published: June 2009

The ultrastructural and cytochemical changes accompanying intracellular digestion and cellular defecation in the haematin cell of Diclidophora merlangi have been described. Blood proteins of the host-fish are sequestered by endocytosis and degraded within an interconnecting network of channels that form an integral, but changing, part of the cell. The digestive enzymes involved originate in the granular endoplasmic reticulum and are packaged in the Golgi apparatus and transferred to the channels in Golgi vesicles. The rate of haemoglobin absorption and the activity of the Golgi, as judged by vesicle counts and staining intensities for thiamine pyrophosphatase activity, are stimulated by the introduction of host protein into the gut lumen. The haematin residues of digestion are extruded periodically into the lumen by exocytosis involving membrane fusion. The process is a continuous one and, in worms starved of food, can result in the complete evacuation of pigment from the cell. It is suggested that a lysosomal system operates in the digestive cycle of the haematin cell.
Chairman's opening remarks
Authors: Soulsby E. J. L.
Published: June 2009

When I graduated as a Veterinary Surgeon some 36 years ago, the number of effective anti parasitic components available for clinical use were remarkably few. Many natural products were still in use (extract of male fern, arecoline, oil of chenopodium, kamala, nicotine, derris and the like) many difficult to formulate and to administer, some requiring overnight fasting before use and purgation after use. The compounds of remarkable promise at that time were phenothiazine for nematodes in farm animals, carbon tetrachloride for liver fluke in sheep and cattle, the sulpha durgs for coccidia and two wonder drugs for the arthropods, DDT and BHC.
Trypanosoma cruzi: separation of broad and slender trypomastigotes using a continuous hypaque gradient
Authors: Schmatz D. M. , Boltz R. C. , Murray P. K.
Published: June 2009

Trypanosoma cruzitrypomastigotes occur as a mixture of morphologically distinct forms in natural and experimental infections. We have been able to separate mixed populations into slender and broad forms using a continuous gradient composed of 12·5–25·0% hypaque in culture media. Previously, comparisons could only be made by using various strains of T. cruzi which show a predominance of either form. This separation procedure gave recoveries of 88–98% and had no effect on the viability of the parasites. Infectivity studies showed that slender forms were much more infectious to cultured muscle cells than were broad forms. However, studies with macrophages from CFW mice showed both forms to be equally capable of infection. It is concluded that the mechanism by which each form infects host cells is different; slender forms being capable of infecting both by penetration and by phagocytosis, while broad forms are only capable of infecting through phagocytosis.
Miracidia infective for snails derived from eggs laid by adult Schistosoma mansoni in vitro
Authors: Newport G. R. , Weller T. H.
Published: June 2009

Various biological mixtures commonly used as microbiological nutrients were added to a chemically defined medium, containing 0·2% (w/v) albumin, in order to assess their ability to support maturation of eggs deposited by adult Schistosoma mansoni in vitro. Of the supplements tested, only lactalbumin hydrolysate and casein hydrolysate stimulated egg deposition and subsequent egg development in vitro. Upon addition of foetal calf serum, further stimulation was noted only in casein hydrolysate-containing media. The addition of mouse red blood cells did not significantly improve the system. Some miracidia which hatched from eggs derived from casein hydrolysate-fortified cultures displayed normal behavioural characteristics, penetrated susceptible snails and established patent infections. These results provide an experimental system for exploring the nutritional requirements of developing miracidia, and the physiological determinants that influence miracidial penetrative capacity and subsequent ability to develop in a susceptible intermediate host.
Eimeria tenella in chickens: development of resistance to quinolone anticoccidial drugs
Authors: Chapman H. D.
Published: June 2009

The development of drug resistance by the present Houghton strain of Eimeria tenella to the quinolones, methyl benzoquate and buquinolate, was found to take place after a single experimental passage. The development of resistance was independent of drug selection pressure and showed cross resistance to other quinolones, but not to amprolium and robenidine. When the Weybridge, Beltsville and Elberfeld strains of E. tenella were compared under similar laboratory conditions, the Weybridge and Elberfeld strains developed resistance to methyl benzoquate after 6 passages and the Beltsville after 5. Studies on the response of the Houghton strain to methyl benzoquate and buquinolate revealed that the drugs did not completely control the infection as measured by weight gain and that oocyst production was not suppressed. These observations indicate that the strain had already acquired some resistance to these drugs. This was confirmed by examining the resistance to methyl benzoquate of a culture of the Houghton strain of E. tenella which had been stored frozen in liquid nitrogen since 1969. This showed full sensitivity to the drug and developed resistance after 8 passages. This suggests that drug tolerance has been acquired by the Houghton strain since 1969.

Oocyst lines were established from the Houghton strain by infecting single birds with approximately 10 oocysts. Eleven of these lines were found to be sensitive to methyl benzoquate, and nine to give rise to resistant parasites. It is concluded that the Houghton strain is contaminated by a small number of resistant oocysts which can be eliminated from a culture by dilution of the challenge inoculum. One of these Houghton oocyst lines, sensitive to methyl benzoquate, developed resistance after 8 serial passages.
The fine structure of the developing macrogamete of Eimeria maxima
Authors: Pittilo R. M. , Ball S. J.
Published: June 2009

The fine structure of the developing macrogamete of Eimeria maxima was studied from chicks killed at intervals from 138 to 147 h after inoculation. The macrogamete developed within a parasitophorous vacuole. Lying within this vacuole and extending for some distance around the periphery of the macrogamete were intravacuolar tubules, grouped in certain areas, and in some cases they were seen to make direct connexions with the cytoplasm of the parasite. During development, electron-pale vesicles were pinched off externally from the surface of the macrogamete. There appeared to be 2 forms of wall-forming bodies of the Type I during development, one form being less osmiophilic than the other. Other organelles present, such as wall-forming bodies of Type II, granular endoplasmic reticulum, mitochondria, canaliculi, lipid inclusions and intravacuolar folds, were similar in structure to those of other Eimeria species.
Isoenzyme characterization of trypanosomes of the subgenusHerpetosoma
Authors: Mohamed H. A. , Molyneux D. H. , Scott C. M.
Published: June 2009

Isoenzyme analysis was used to characterize 6 species of trypanosomes of the subgenusHerpetosomausing 13 different enzyme systems. The species studied wereTrypanosoma lewisi, T. musculi, T. grosi, T. microti, T. evotomysandT. nabiasiwhich cannot be distinguished on morphological grounds. Extracts for thin-layer starch-gel electrophoresis were prepared from cultures of insect forms in either Schneider'sDrosophilaor Grace's insect tissue culture media with foetal calf serum or a nutrient agar medium. Extracts ofT. lewisiandT. musculibloodstream forms were also run for comparison. All parasites gave distinct patterns which enabled them to be differentiated on one or more enzyme systems. Two types of computer analysis were used to group the parasites; using these techniques the murine parasitesT. lewisi, T. musculiandT. grosifell into one broad group, andT. microtiandT. evotomysof microtine rodents formed another. These findings are in accord with earlier observations on the behavioural characteristics of these parasites in their mammalian host and their vector (fleas). The clear differences observed provide the basis for the application of other biochemical and immunological techniques for differentiation within this subgenus of trypanosomes.
Fasciola hepatica: attempts to induce protection against infection in rats and mice by injection of excretory/secretory products of immature worms
Authors: Rajasekariah G. R. , Mitchell G. F. , Chapman C. B. , Montague P. E.
Published: June 2009

In vitroexcretory/secretory products of 4-week (immature) and 8- week-old (mature)Fasciola hepaticaparasites, derived from rats, were injected together with adjuvant into naive rats and mice. Resistance to infection was assessed in rats by counting adults in the bile ducts at 9 weeks, or in mice by recording deaths after oral challenge with a high dose of viable metacercariae. Exposure of rats to excretory/secretory products of immatureF. hepaticaconferred a significant degree of resistance which was comparable to the level of resistance induced following oral administration of a low number of metacercariae. No protection against infection was seen in rats injected with excretory/secretory products from mature, bile duct-derived worms. In mice, no obvious mouse strain variation in susceptibility to first infection existed and hypothymic nude mice were as susceptible to infection as intact mice. As determined by protection against death, vaccination with excretory/secretory products derived from immatureP. hepaticawas without effect in mice. It is concluded that ‘host protective antigens’, at least for rats, were present in the excretory/secretory products of immatureF. hepaticalarvae.
Helminth parasites of Jamaican anoles (Reptilia: Iguanidae): variation in prevalence and intensity with host age and sex in a population of Anolis lineatopus
Authors: Vogel P. , Bundy D. A. P.
Published: June 2009

The Jamaican iguanid lizard Anolis lineatopus is the host of 4 species of helminth parasite: an acanthocephalan (Centrorhynchus spinosus), a digenean (Mesocoelium danforthi), and 2 nematodes (Cyrtosumum scelopori and Thelandros (?cubensis). Prevalance of C. spinosus was unrelated to host age but was considerably higher in males (43%) than in females (10%). The intensity increased with host age: (range: 1–23, median: 3). Prevalence of C. scelopori increased with host age in both sexes: juveniles (<3 months) were uninfected while infection occurred in almost all lizards older than 9 months. Intensity was higher in males (range: 1–403, median: 158) than in females (range: 1–297, median: 86). The infection patterns of C. spinosus and C. scelopori differed significantly from each other and were not consistent with a simplistic direct relationship between time of exposure and infection prevalence. Acanthocephalan and digenean infections occurred at low prevalence and intensity although prevalence in older, larger lizards tended to be higher than in younger, smaller ones.
Cytochemical studies on nuclear DNA of four eucoccidian parasites,Isospora (Toxoplasma) gondii, Eimeria tenella, Sarcocystis cruziandPlasmodium berghei
Authors: Cornelissen A. W. C. A. , Overdulve J. P. , Ploeg M. Van Der
Published: June 2009

Feulgen-pararosaniline(SO2) staining was performed on stages in the life-cycle ofIsospora (Toxoplasma) gondii, Eimeria tenella, Sarcocystis cruziandPlasmodium berghei. The fluorescence emission of the stained DNA in nuclei of these stages was examined and compared with absorption microscopy measurements at 560 nm (green light) of the same specimens. Accurate identification of single cells, and especially discrimination between young schizonts and young gamonts was difficult after Feulgen staining. To overcome this problem preparations were first stained with Giemsa and the cells of interest precisely located with the aid of an England finder. The same preparations were then hydrolysed and stained with Feulgen—pararosaniline(SO2), after which the previously identified cells were investigated. The DNA distribution after Feulgen staining corresponded with the shape of nuclei after Giemsa staining. DNA was present in all investigated stages of the four parasites, including macrogamonts ofI. (T.) gondiiandE. tenellaand peripheral blood gamonts ofP. berghei. Macrogamonts could be recognized, even at a stage at which they can hardly be differentiated from young schizonts in Giemsa-stained preparations, by their typical distribution pattern of Feulgen fluorescence. Feulgen fluorescence was more granular and confined to the peripheral region of the nucleus, leaving a distinct nucleolus unstained. The horseshoe-shaped nuclei typical of macrogamonts could also be observed in some second generation merozoites ofE. tenella, indicating that these merozoites are already sexually differentiated. The relationship between the present cytochemical observations and the ultrastructure of the four investigated parasites is discussed.
The anaerobic end-products of helminths
Authors: Barrett J.
Published: June 2009

Parasitic helminths belong to 3 separate phyla and there is always the danger of over-generalization. The various routes of anaerobic carbohydrate breakdown in parasitic helminth differ in their efficiencies and in their power output. The choice of end-product represents a compromise between these two conflicting forces. In addition, anaerobic pathways must satisfy the redox requirements of the tissues and provide a source of intermediates for synthetic reactions. Other considerations include the metabolic cost of excretion and the effect of end-products on protein structure and function. The different end-products may fulfil additional functions such as pH control, nitrogenous excretion, osmotic regulation, intracellular signalling and the suppression of host responses.

A complicating factor in parasitic helminths is the existence of strains with different biochemical characteristics, including marked variation in end-product formation. The various tissues of the same parasite can also produce different end-products and the pattern of end-product formation is influenced by a variety of extrinsic and intrinsic factors such as age, sex, length of incubation, pO2 and availability of substrates. The catabolic pathways of helminths thus show considerable functional adaptation.

There is, as yet, no satisfactory explanation as to why helminths do not make the maximum use of any oxygen available to them; and the contribution of oxidative processes to the overall energy balance of parasites probably varies from species to species.

The catabolic pathways of adult helminths are derived from the anaerobic pathways present in their free-living relatives. Two main trends are evident, homolactic fermentation and carbon dioxide fixation, the latter involving a partial reverse tricarboxylic acid cycle. In general, homolactic fermentation is found in blood and tissue parasites, carbon dioxide fixation in gut parasites. These two types of metabolism are, of course, in no way absolute, most homolactic fermentors fix carbon dioxide to a certain extent and many parasites which fix carbon dioxide also produce lactate. Parasitic helminths possess a wide range of different catabolic pathways, superimposed upon which is a high degree of functional plasticity.
Density-dependent mechanisms in the regulation ofFasciola hepaticapopulations in sheep
Authors: Smith Gary
Published: June 2009

Populations ofFasciola hepaticainfecting sheep are regulated by at least 3 density-dependent processes. Parasite deaths due to parasite-induced primary host mortality, fluke fecundity and asexual multiplication in the intermediate snail host,Lymnaea truncatula, vary according to the intensity of infection. Empirical and theoretical evidence is used to assess theextentto which each of these processes in turn affects parasite population numbers.