bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological and histochemical observations on oocyte atresia in Centrorhynchus corvi (Acanthocephala)
Authors: Parshad V. R. , Guraya S. S.
Published: June 2009

A morphological and histochemical study has been made of atresia in oocytes in the ovarian balls of an acanthocephalan (Centrorhynchus corvi). Growing oocytes and mature oocytes have been observed to undergo atresia. With the start of atresia, the nuclear and cytoplasmic components are observed to be greatly altered. The atretic oocytes develop abnormal aggregations of cell components, which contain proteins, phospholipids and lipoproteins. It is suggested that the cellular products of degenerating oocytes are gradually absorbed by the supporting syncytium. The atresia of growing oocytes is greater in uninseminated than in inseminated females, which indicates that in the absence of a mating stimulus atresia occurs more frequently.
Genetic resistance to helminths. The influence of breed and haemoglobin type on the response of sheep to re-infection with Haemonchus contortus
Authors: Altaif K. I. , Dargie J. D.
Published: June 2009

The influence of genetic factors on acquired resistance to Haemonchus contortus infections in sheep was investigated. Animals whose primary infections were terminated with an anthelmintic failed to develop any immunity against subsequent challenge as judged by worm numbers. Nevertheless, all were better able to retard the development and reduce the fecundity and haematophagic activities of their parasite populations than animals undergoing primary infections. High levels of resistance, as judged by all these parameters, were observed in most animals when the challenge larvae were superimposed on existing worm populations. The patterns of worm establishment and disease indicated that genetic factors operated in determining resistance, since fewer worms became established and less severe clinical and pathophysiological changes were observed in Scottish Blackface than in Finn Dorset sheep with the same haemoglobin type. Similar advantages were displayed by animals with haemoglobin AA and to a lesser extent those with haemoglobin AB over haemoglobin BB types. The importance of breed was further indicated by the occurrence of ‘self-cure’ in the majority of the Scottish Blackfaces but in only one Finn Dorset. There was no evidence that this reaction was associated with haemoglobin type.
Eimeria maxima: a comparison of two laboratory strains with a fresh isolate
Authors: Norton C. C. , Hein Helen E.
Published: June 2009

Oocysts of the Weybridge and Houghton strains ofEimeria maximaand a fresh field isolate were similar and measured on average 30·9 × 22·4 μm. The Weybridge strain and the field isolate produced similar pathogenic effects in 6-week-old chickens, high doses causing 50–80% mortality and severe weight loss. The Houghton strain was slightly less pathogenic and few birds died but more oocysts were produced. With each strain, a single dose gave complete immunity to a light challenge with the homologous strain. Two or 3 immunizing doses gave complete immunity to a heavy homologous challenge but were not sufficient to protect against heterologous challenge.
Intestinal pathology associated with Trichostrongylus colubriformis infection in sheep: histology
Authors: Barker I. K.
Published: June 2009

Observations were made on the histology of tissues from the first 6–10 m of the small intestine from both sheep infected with Trichostrongylus colubriformis and from uninfected controls. In uninfected animals, and in distal samples from infected lambs, villi were tall and covered by tall columnar epithelium, the intestinal crypts were convoluted and the lamina propria was only moderately cellular.
In tissues with sub-total villus atrophy and a convoluted surface, the superficial epithelium was usually low columnar, often with an indistinct brush border. More severely affected mucosa was flat, with low surface epithelium and protruding crypt openings. The flat surfaces frequently had leaks of eosinophilic material and polymorphonuclear cells between enterocytes, or through erosions in the epithelium. Such defects were smaller and less frequent in mucosa with a convoluted surface. There were increased mitoses in intestinal crypts and a heavy inflammatory cell infiltrate in the lamina propria. Mast cell, globule leucocyte and theliolymphocyte numbers were not increased in infected sheep.
Periodicity in the hatching of digenean eggs: a possible circadian rhythm in the life-cycle ofTransversotrema patialense
Authors: Bundy D. A. P.
Published: June 2009

The temporal distribution of hatching of the embryonated eggs ofTransversotrema patialensehas been examined under different temperature and illumination regimens. Under a DL 12: 12 regimen at 30°C egg hatching exhibited a circadian rhythm with a period of 24 h. Within a diel time-frame hatching was distributed over the final 9 h of the light period with less than 2% of the eggs hatching during the dark period. This pattern was temperature independent over the range 25 to 30°C and persisted under constant illumination. It is suggested that the timing of hatching is under endogenous control and is functionally related to a circadian rhythm of behaviour of the intermediate host mollusc,Melanoides tuberculata.
Observations on the development of the ovarian balls ofMoniliformis(Acanthocephala)
Authors: Asaolu S. O. , Whitfield P. J. , Crompton D. W. T. , Maxwell Lesley
Published: June 2009

Observations have been made on the ultrastructure of objects identified as ovarian balls from femaleMoniliformisafter 1, 3, 5, 7 and 9 days in the rat. Similar objects are present in the body cavity of female cystacanths from cockroaches. The ovarian balls from 1-day-old worms are formed of several cells which are enclosed within a surface coat. During development, the ovarian balls increase in size and cell number and the internal organization appears to become more complex. After 9 days of development in the rat, the surface coat of the ovarian balls can no longer be observed and microvilli are present. It also appears that the supporting syncytium has been formed by this time.
Association between Pelodera strongyloides (Nematoda: Rhabditidae) and wood mice, Apodemus sylvaticus
Authors: Hominick W. M. , Aston Amanda J.
Published: June 2009

Pelodera strongyloides larvae were found in the conjunctival sacs of Apodemus sylvaticus and Clethrionomys glareolus and in hair follicles of A. sylvaticus. Those in the eyes were 3rd-stage larvae while most of those in the dermis were early 4th stages. There was no evidence of pathology and sections of the skin showed that the nematodes were well-tolerated by the mice. Nematodes emerged from the skin of freshly killed mice and moulted once to the adult stage in 1–2 days at 15 °C. The stimulus to resume development appeared to be a reduction in temperature rather than presence of bacterial food or reduction in osmotic pressure. Countless generations ensued on nutrient agar provided the nematodes were periodically sub-cultured onto fresh agar. Nematodes from the eyes died in culture. Dauerlarvae of P. strongyloides were produced in exhausted cultures. They resumed development on fresh agar but not in distilled water. About half could be induced to exsheath by a temperature similar to that of mouse skin. A. sylvaticus probably accumulates nematode larvae in the dermis during its life and the nematodes resume development when the host dies.
Taenia saginata (Cestoda) in western Kenya: the reliability of faecal examinations in diagnosis
Authors: Hall Andrew , Latham M. C. , Crompton D. W. T. , Stephenson L. S.
Published: June 2009

The prevalence of Taenia saginata (Cestoda) among 146 predominantly Pokot tribesmen in western Kenya was studied in an attempt to assess the reliability of detecting infections by faecal examinations. Firstly, a single faecal sample was microscopically examined after being processed by a standard ether sedimentation technique. Secondly, all subjects were treated with niclosamide and a purgative and the tapeworms were recovered. In this way the efficiency of diagnosing infections by faecal examinations was estimated. T. saginata eggs were found in the faeces of 68% of the men who were eventually found to be infected. Information was collected by interview from all subjects about whether they were or ever had been infected with tapeworms and about the form of treatment previously sought or taken. Eleven out of 25 men were apparently unaware of their tapeworm infections while no evidence of infection was found among 10 of the 24 reportedly infected men. A change in the pattern of treatment for tapeworms was reported which may have resulted in a recent decline in the prevalence of infection.
New defined and semi-defined media for cultivation of the flagellate Trichomonas vaginalis
Authors: Linstead David
Published: June 2009

Studies on the nutrition and physiology of Trichomonas vaginalis have been hampered by the lack of a defined synthetic medium in which to grow the organism. New synthetic media free of ill-defined supplements and serum which support good growth of T. vaginalis have been developed in this study. The first successful approach to a defined medium resulted from the modification of the tissue-culture medium CMRL 1066. Essential modifications included (1) lowering the redox potential of the medium by adding high levels of ascorbate and (2) modifying the buffer system. Subsequently, CMRL 1066 was replaced by two new media DL7 and DL8 which have greater flexibility in their formulation and permit improved serum-free growth. Serum was replaced by bovine serum albumin and cholesterol, together with either a glyceryl fatty acid ester or a defined mixture of fatty acids. Preliminary nutritional studies using the new media have indicated a requirement for saturated and unsaturated fatty acids and a sterol.
The effect of concurrent infection with Trichinella spiralis on Hymenolepis microstoma in mice
Authors: Howard R. J. , Christie P. R. , Wakelin D. , Wilson M. M. , Behnke J. M.
Published: June 2009

The intestinal changes brought about by rejection of Trichinella spiralis from mice were studied in relation to their effects on a concurrent infection with Hymenolepis microstoma, a cestode not normally rejected from mice. The rejection phase of T. spiralis was associated with a marked stunting of growth of H. microstoma given just before, during, or just after rejection of the nematode. The survival of H. microstoma was affected only when rejection of T. spiralis coincided with the intestinal phase of the cestode: if T. spiralis rejection was timed to occur after the scolex of the cestode had entered the bile duct there was no loss of H. microstoma. It is suggested that the adverse effects on growth and establishment of H. microstoma were due to the non-specific inflammatory component of the host's response to infection with T. spiralis.
An ultrastructural study on the role of Kupffer cells in the process of infection by Plasmodium berghei sporozoites in rats
Authors: Meis J. F. G. M. , Verhave J. P. , Jap P. H. K. , Meuwissen J. H. E. Th.
Published: June 2009

The interactions in vivo between Plasmodium berghei sporozoites and Kupffer cells in rat livers were studied by transmission electron microscopy. By 10 and 15 min after inoculation, sporozoites were both free in the liver sinusoids and inside endocytotic vacuoles of the Kupffer cells. The latter cells were very active in phagocytosing sporozoites, bacteria and red blood cells. The sporozoites retained their integrity inside the endocytotic vacuoles and no signs of lysosomal digestion were observed. Sporozoites seen within endocytotic vacuoles 1 h after inoculation were still morphologically intact, although bristle-coated vesicles fused with the vacuole membrane. Evidence is presented which suggests that Kupffer cells transport sporozoites towards the space of Disse and adjacent hepatocytes. No sporozoites were seen to penetrate an endothelial cell or its narrow fenestrae. It is proposed that Kupffer cell passage, rather than gaps in the sinusoidal lining, represents the normal route that sporozoites take to circumvent the endothelial barrier. The localization of exo-erythrocytic forms was made easier by the use of Brown Norway rats in which many more parasites develop than in the Wistar rats. The distribution pattern of the parasites was found to be mainly around the ‘periportal’ zones of the acini of liver tissue.
Infection of mammalian cells with Theileria species
Authors: Stagg D. A. , Young A. S. , Leitch B. L. , Grootenhuis J. G. , Dolan T. T.
Published: June 2009

Experiments were carried out to determine the susceptibility of mammalian cells to infection with different species of Theileria in vitro. Sporozoites of Theileria parva (parva), Theileria parva (lawrencei) and Theileria taurotragi were isolated from Rhipicephalus appendiculatus ticks by grinding infected ticks in medium, filtering the suspension and concentrating by centrifugation. The sporozoites were used in attempts to infect in vitro peripheral blood leucocytes harvested from 16 different mammalian species which included 12 species of Bovidae from 6 different sub-families. The technique was shown to be both sensitive and reproducible. The sporozoites of T. parva (parva) infected and transformed cells from 2 species of the sub-family Bovinae, the two cattle types and African buffalo. Theileria parva (lawrencei) infected and transformed cells from the two cattle types, African buffalo and Defassa waterbuck. Theileria taurotragi sporozoites infected in vitro cells from 11 different species of Bovidae which were members of 6 sub-families; Bovinae, Tragelaphinae, Reduncinae, Alcelaphinae, Antilopinae and Caprinae. Transformed lymphoblastoid cell lines were established from 7 of the species infected. Sporozoite attachment and infection was not observed with non-susceptible bovid host cells, nor were any of the non-bovid leucocytes infected by the parasites. The host range observed in this study corresponded to the known host range in vivo.
Kinetics of proglottid formation, maturation and shedding during development of Hymenolepis nana
Authors: Kumazawa H. , Suzuki N.
Published: June 2009

Growth of Hymenolepis nana in mice is analysed by identifying designated stages of proglottid maturation in the strobila, and by determining the numbers of proglottids between them and the posterior terminus of the worm, as a function of time after cysticercoid infection. The proglottid maturation rate was fairly constant between stage A (onset of the somatic primordium formation) and stage B (first appearance of sperms in the seminal vesicle), but gradually fell after stage B, during pre-patent development of the worm. The actual rate of proglottization during this period coincided well with that estimated from the number of proglottids between stages A and B on an assumption of a certain maturation rate. This procedure is extended to estimate the rates of proglottid formation and shedding during later development. It is deduced that the absolute rate of proglottization increases until day 12, gradually decreasing afterwards, and that from 2300 to 2800 proglottids are shed by day 20, until which from 4000 to 4500 proglottids have passed stage A. It is shown that the proportionate increase of the gravid region in older worms depends not only on a decrease in the rate of proglottization, but also on the prolonged period during which proglottids stay in the strobila.
Eimeria mitis in mixed infections with E. acervulina and E. brunetti in the fowl
Authors: Joyner L. P. , Norton C. C.
Published: June 2009

Eimeria mitis and E. acervulina affect different areas of the intestine. Young chicks received E. mitis with or without E. acervulina in doses ranging from 2 to 128 × 104 oocysts. Mixed infections produced significantly more severe effects on growth than single infections of either species. The ratio of villus height to total mucosal thickness was reduced throughout the intestine in birds which received the mixed infection. E. mitis and E. brunetti affect the same area of the intestine. Single infections of E. brunetti in a range of doses from 1.25 to 20 × 103 oocysts produced a similar reduction in growth. When 20 × 103 oocysts of E. mitis were inoculated simultaneously, the effect on growth was not so severe and the oocyst output of both species was reduced. E. brunetti, superimposed 1, 2 or 3 days after an E. mitis infection, produced no greater effect on growth than E. mitis alone. Similarly, infections of E. mitis, superimposed on E. brunetti had no greater effect on growth than the latter species alone. Oocyst output of E. brunetti in superimposed infections was not reduced but peak output was delayed.
Seasonal occurrence, sex ratio and site preference ofArgulus coregoniThorell (Crustacea: Branchiura) parasitic on cultured freshwater salmonids in Japan
Authors: Shimura S.
Published: June 2009

Analysis of the seasonal occurrence ofArgulus coregonionOncorhynchus masouandSalmo gairdneriindicates that the parasites overwinter as eggs and that there are 1 or 2 generations/year. Larvae which hatch from the overwintered eggs are abundant from May through July. Individuals hatched in May and June attain maturity and lay eggs in August. Larvae of the second generation are abundant in September, and they lay eggs in October–November which overwinter. Hatched larvae from overwintered eggs may mature in July and deposit overwintering eggs in September. The sex ratio ofA. coregoniis about 1:1.A. coregonishows an age-specific site preference onO. masou. Small parasites occur on almost all parts of the skin and fins, with slightly heavier concentrations on and around the pectoral and pelvic fins. Large parasites are found mainly on the skin around these fins.
Sexual processes in the kinetoplastida
Authors: Tait A.
Published: June 2009

The commonly held view that the kinetoplastida, and in particular trypanosomes, are asexual is largely derived from the principle that an organism is asexual until proved sexual. If the basis for this view is examined in detail, it largely arises from the lack of morphologically distinguishable gametes, the difficulties encountered in visualizing chromosomes and a few experiments, using drug-resistant stocks, in which no recombination between stocks could be demonstrated. While it is clear that these organisms are able to reproduce asexually, the existence of a sexual cycle was, until recently, an entirely open question. The early work strongly suggests that any sexual process (in the species examined extensively at the morphological level) does not involve classical well-differentiated gametes and so must involve fusion of morphologically very similar cells. These findings taken together with the inability to visualize chromosomes and thereby identify meiosis, mean that classical methods are unable to detect any sexual process even if it did occur. This review examines the evidence provided by the experimental approaches which have been applied recently to the question of kinetoplastid sexuality. These approaches include isoenzyme studies and the analysis of possible genetic exchange by the use of selective markers (e.g. drug resistance). The results which these techniques have produced make it clear that the kinetoplastid protozoans cannot be regarded as a totally asexual group of organisms.
Pattern and paradox in parasite reproduction
Authors: Calow P.
Published: June 2009

Parasites are more fecund than free-living relatives. The traditional explanation of this is that parasites have to compensate for massive mortality in the transmission phase of their life cycles, but there are neo-Darwinian problems with this interpretation. Similarly, parasites invest more resources in reproduction than free-living relatives but often live longer as adults, and yet negative correlations are expected between fecundity and longevity. These patterns and paradoxes are discussed within the context of a general life-cycle theory. The theory is also used to address questions concerning the influence of age-specific mortality on life-cycle patterns, the trade-off between gamete size and numbers, and the relative merits of gametic and non-gametic reproduction. Wherever possible, the theory is related to facts about parasites.
Experimental infections withCooperia oncophora(Railliet, 1918) in calves. Results of single infections with two graded dose levels of larvae
Authors: Borgsteede F. H. M. , Hendriks J.
Published: June 2009

Two experiments were carried out in which calves reared parasite-free were infected with a single dose of 3rd-stage larvae ofCooperia oncophora. In the first experiment the calves received 20000 or 200000 infective larvae and they were autopsied 28 or 56 days after the infection. In the second experiment the doses were the same but the animals were killed 14, 84 or 140 days after infection. If a dose of 20000 was given, clinical signs were never observed, while at a dose level of 200000 the weight gain was less on 56 and 84 days after the infection compared with the low-infected groups or the control animals. After 140 days the differences in weight gain were compensated. Faecal egg output was higher in the 200000 groups only in the first period of patency, thereafter the calves in the 20000 groups produced more. No obvious differences between the two infection levels were observed with regard to the haematological data. In the low-infected groups worm counts were only slightly lower when the results after 28 days were compared with those after 56 days. Also, the worm numbers after 14 days were almost equal to those after 84 days, while at 140 days 1 animal still had the same number, the other one had lost its worm burden. In the high-infected groups the worm loss was much quicker. After 28 days a great part of the population had already been lost. Obviously, at the 200000 level the reaction of the host against the parasite was much stronger. Adult worms were expelled at a higher rate than early 4th-larval stages. In the first experiment worm measurements revealed differences between the length of females, males and spicules of males, these being significantly longer in the low-infected groups. Analysis of the distribution of worms over the small intestine showed that in the low-infected groups worms were mainly restricted to the first 6 metres. In the high-infected groups the worm population was distributed more evenly over the whole small intestine.
Observations on coprophagy and the transmission ofHymenolepis nanainfections in mice
Authors: Ghazal A. M. , Avery R. A.
Published: June 2009

Young, previously uninfected white mice became infected withHymenolepis nanawhen exposed in small cages to parasite eggs which had been sprinkled in suspension onto the floor of their cage, or to faeces from mice with patent infections. The mean daily probabilities of infection for individual eggs under these two conditions were 2·9 × 10−6and 5·4 × 10−6respectively. If the mice were starved for 24 h prior to exposure to faeces, then the mean daily probability of infection increased to 2·6 × 10−4. These differences in transmission are interpreted as being due to differences in the extent of coprophagy; they are not due to any effect of starvation on the hatchability of eggs.
Acquired resistance of black mollies Poecilia latipinna to infection by Ichthyophthirius multifiliis
Authors: McCallum H. I.
Published: June 2009

Changes in the response of black mollies Poecilia latipinna to infection with Ichthyophthirius multifiliis subsequent to single I. multifiliis infections were examined experimentally. Incomplete resistance to infection was established, the degree of which did not depend on the intensity of the initial infection. Resistance was maintained for longer periods, however, by those fish with higher initial levels of infection. Previous experience of infection by their hosts had a significant, though small, effect on the time for which trophozoites remained on the fish. The influence of these results on the population dynamics of the Ichthyophthirius-fish interaction is examined with the aid of simple mathematical models.
In vitro demonstration of in utero larval development in an oviparous parasitic nematode: Haemonchus contortus
Authors: Ayalew Liyew , Pearson Murphy Beverley E.
Published: June 2009

The life-cycle of Haemonchus contortus, a pathogenic stomach nematode of sheep, is typical of those of the other members of the superfamily Trichostrongyloides, all of which require a period of development outside the definitive host. Classically, gravid H. contortus, known as strictly oviparous, releases her eggs into the abomasal lumen. The eggs are passed out in the faeces in which they hatch into the 1st-stage larvae and then develop into the infective 3rd-stage larvae. We have developed a method to study the fate of eggs within gravid worms. Using this procedure, we have shown that H. contortus may also exhibit viviparity with apparently normal development from the egg to the 4th larval stage taking place within the gravid female maintained in vitro. On the basis of these observations we speculate that viviparity might occur in vivo with consequent autoinfections; if so, this might explain some puzzling clinical and epidemiological features of haemonchosis, as well as the incomplete efficacy of current control measures.
Studies on the life-cycle ofHimasthla militaris(Trematoda: Echinostomatidae): influence of temperature and salinity on the life-span of the miracidium and the infection of the first intermediate host,Hydrobia ventrosa
Authors: Vanoverschelde R.
Published: June 2009

The influence of temperature and salinity on miracidial longevity and miracidial infectivity of the digenean,Himasthla militaris, has been examined. At 14, 25 and 30 °C the half-life of the miracidia was 1200, 630 and 420 min respectively, and infection of the first intermediate host,Hydrobia ventrosa, only occurred at 25 and 30 °C, for both temperatures 52% became infected. In the range 2·1 to 34‰ (2·1, 4·2, 8·5, 17 and 34‰) the miracidia had a minimal and maximal half-life of 60 and 630 min in water with a salinity of 2·1 and 17‰ respectively, while the infection of the snail host was possible only in water with a salinity of 8·5 and 17‰.
Proteinases ofLeishmania mexicanaand other flagellate protozoa
Authors: Coombs G. H.
Published: June 2009

The amastigote form of the human pathogenLeishmania mexicanacontains high proteinase activity, some 20 times greater than that in the promastigote form and macrophages and appreciably higher than the activity in other flagellate protozoa. The main amastigote enzymes are soluble, whereas those of the promastigote are particulate, and have inhibitor sensitivities characteristic of cysteine proteinases. The very high soluble proteinase activity ofL. mexicanaamastigotes may be a primary factor in the survival and growth of this mammalian stage in its potentially degradative intracellular habitat.
The dynamics of infection of Tribolium confusum by Hymenolepis diminuta: the influence of exposure time and host density
Authors: Keymer Anne
Published: June 2009

Survival of Hymenolepis diminuta eggs (as measured by their infectivity to the intermediate host) was found to be age-dependent with an expected value of 11 days when the eggs were retained within the faecal pellet at 10 °C. The expected life-span of eggs under experimental conditions (i.e. extracted from faecal material and placed on filter paper at 30 °C) was estimated as 33 min. The mean parasite burden of populations of Tribolium exposed to known densities of H. diminuta eggs was found to rise to a plateau with increasing exposure time. The experimental results provided a method of estimating the instantaneous rate of parasite transmission: a value of 0·0004/egg/min/host/13 cm2 was obtained. The mean parasite burden of populations of T. confusum exposed to known densities of H. diminuta eggs was found to decrease exponentially with increasing host density. A second estimate of the instantaneous rate of parasite transmission of 0·004/egg/min/host/13 cm2 was obtained from the experimental results. No differences in susceptibility to infection between 2-week-old male and female beetles were found. A marked decrease, however, was apparent with increasing beetle age up to 14 weeks post-eclosion.
Schistosoma mansoni: a histological study of migration in the laboratory mouse
Authors: Wheater P.R. , Wilson R. A.
Published: June 2009

Quantitative histological methods were applied in a study of the migratory route of schistosomula within the definitive mammal host. The observations are consistent with an entirely intravascular mode of migration in the direction of blood flow. They do not support a trans-diaphragm route. Schistosomula can be identified in low numbers in systemic organs, in the left side of the heart and in the venous compartment of the pulmonary circulation. They were not observed penetrating the diaphragm or the capsule of the liver. No histopathological evidence was found to suggest that the tissue responses of previously unexposed hosts affect migrating schistosomula at any stage during migration. These non-specific tissue responses were marked only in the skin phase of migration.
Lerbek, a synergistic mixture of methyl benzoquate and clopidol for the prevention of chicken coccidiosis
Authors: Ryley John F.
Published: June 2009

Methyl benzoquate at 20 ppm or clopidol at 250 ppm in the diet show true coccidiostatic activity in infections with Eimeria tenella in the chick. Lerbek, a synergistic mixture yielding 8·35 ppm methyl benzoquate and 100 ppm clopidol, produced a partially coccidiocidal effect; relapses following restricted periods of medication were less severe, and suppression of parasite development following delayed medication was quicker and more effective than with either component of the mixture used alone.
Structure and function of the intestinal-cloacal junction of the nematodeHeterakis gallinarum
Authors: Lee D. L.
Published: June 2009

The ultrastructure of the intestinal-cloacal junction of the male nematodeHeterakis gallinarumis described. A sphincter muscle seals the lumen of the alimentary tract at this point by squeezing on the posterior cells of the intestine. These posterior cells of the intestine are unusual in that they contain numerous microtubules, and are very different from the other cells of the intestine. Electron-dense granules lie at the base of these cells where they abut on to the portion of the sphincter muscle which contains the myofilaments. It is suggested that a build-up of pressure in the intestinal lumen, brought about by the pumping action of the pharynx and/or contraction of the muscle network around the intestine, is the most probable means of opening the sphincter at defecation. On the other hand, the structure of the posterior cells of the intestine suggests that they may act as a stretch receptor which communicates with the sphincter muscle by means of a pharmacologically active substance held in the electron-dense granules which lie in the basal region of these cells.
The mode of action of suramin on the filarial worm Brugia pahangi
Authors: Howells R. E. , Mendis A. M. , Bray P. G.
Published: June 2009

The mode of action of suramin upon Brugia pahangi has been investigated in vivo and in vitro. The drug was without effect on the glycolytic activity of worms in vitro at 2 × 10−4 M. The lack of effect was correlated with the failure of [14C]suramin to penetrate the worms in vitro. Suramin bound to the surface of worms in vitro presumably by virtue of its polyanionic nature. B. pahangi adults ingested [14C]suramin in vivo but no reduction in the rate of lactate production, of glucose utilization or in the rates of uptake of [14C]glucose, [14C]leucine or [14C]adenosine was observed in worms recovered from jirds between weeks 1 and 5 following 4 daily doses of suramin at 50 mg/kg given intraperitoneally. Worm death occurred between weeks 5 and 7 but this delayed drug effect was not the result of a progressive accumulation of suramin in the worms. Ultrastructural changes were observed in the intestinal epithelium of worms from suramin-treated jirds and parallel observations on worms exposed to Trypan blue in vivo suggest that both polyanionic compounds are restricted to the intestinal lumen of the worms. The evidence presented is consistent with the concept that, in B. pahangi, suramin acts at the surface of the intestinal epithelium and not by primarily inhibiting glucose catabolism or inhibiting phagosome and lysosome fusion as previously demonstrated for bloodstream trypanosomes and mammalian macrophages, respectively
Studies on the pathology of an avian trypanosome (T. bouffardi) infection in experimentally infected canaries
Authors: Molyneux D. H. , Cooper J. E. , Smith W. J.
Published: June 2009

Experimental infections of canaries with an avian trypanosome, Trypanosoma bouffardi, isolated from West Africa demonstrated that these infections can cause pathological changes in tissues. Enlargement of the spleen coincided with peak parasitaemia but no other gross changes were observed. Histopathological examination of infected and control birds revealed focal myocarditis and lymphoid hyperplasia, in infected birds, which are consistent with trypanosome infection. Avian trypanosome infections are not usually regarded as pathogenic but our results suggest that pathological changes occur which are similar to those observed in mammals infected with salivarian trypanosomes
The enzymes of purine salvage inTrypanosoma cruzi, Trypanosoma bruceiandLeishmania mexicana
Authors: Davies Mary J. , Ross A. M. , Gutteridge W. E.
Published: June 2009

We have previously shown the presence of various purine salvage enzymes inTrypanosoma cruzi, including phosphoribosyltransferase, aminohydrolase, kinase, phosphorylase and hydrolase activities. We now report that a similar situation occurs inLeishmania mexicana amazonensisandTrypanosoma brucei brucei. In all three organisms we found higher levels of activity for the phosphoribosyltransferase enzymes than for the nucleoside kinases, suggesting a preference for the salvage of purine bases rather than nucleosides. Similarly, absence of inosine phosphorylase activity suggests that only one route for the salvage of hypoxanthine is available to the three organisms. The most striking difference was that whereasT. cruziandT. bruceipossessed adenosine aminohydrolase activity, this was not detected inL. mexicana; instead adenine amino-hydrolase activity was found. The overall similarity, as judged by the distribution of enzyme activities, of purine salvage in these three members of the kinetoplastida suggest a broad spectrum of activity for any inhibitor acting in this area; the plethora of alternative salvage pathways, however, suggests that in no case would such inhibition be cidal.
The co-occurrence of three species of Diorchis Clerc, 1903 (Cestoda: Hymenolepididae) in the European coot, Fulica atra L.
Authors: Pojmańska Teresa
Published: June 2009

The relationship between intensity and site of infection of Diorchis brevis, D. inflata and D. ransomi in Fulica atra from central Poland has been analysed; of 173 adult birds 152 (87·9%) were infected with one or more of these three species. From (1) the incidence of the three species (D. brevis, 59·5%; D. inflata, 69·9%; D. ransomi, 61·3%), (2) the high total incidence and high total intensity of infection (118·2 worms/bird) in hosts harbouring the three species concurrently and (3) the frequent co-occurrence of all three species in the same site in the host gut, it is concluded that there are no antagonistic interactions among these species. There are, however, some inter-dependencies between the number of parasites and the site occupied by particular species. In heavy infections there was a tendency to specific segregation and extension of the site of each species. This suggests the existence of inter- and intra-specific competition at higher densities of infection, regulating the spatial distribution of these parasites in the host gut.
The survival of desiccation by the free-living stages ofTrichostrongylus colubriformis(Nematoda: Trichostrongylidae)
Authors: Wharton D. A.
Published: June 2009

The survival of the free-living stages ofTrichostrongylus colubriformisunder defined conditions of temperature and relative humidity was investigated. The survival of embryonated eggs was poor at 0, 33 and 54·5 % relative humidity (rel. hum.) at 20 °C but hatching occurred from a proportion of eggs even after exposure for 104 days to 76 and 98% rel. hum. at 20 °C. Second-stage larvae were desiccation-susceptible and were killed within 6 h even at 98% rel. hum. and 20 °C. Infective larvae, dried separately or in clumps, survived prolonged exposure to desiccation at 33–98% rel. hum. and 20 °C with 50% survival times of 58–164 days. Clump formation did not enhance survival in this range. Infective larvae also survived exposure to vacuum desiccation with 50% survival times of 8·8 h in clumps and 4·5 h when dried separately. The infective larva thus readily survives desiccation and may prove a useful model for the study of anhydrobiosis.
The anti-neoplastic effect of trichinellosis in a syngeneic murine model
Authors: Pocock Dorothy , Meerovitch Eugene
Published: June 2009

C57B1/6 male mice with chronic trichinellosis, and age-matched uninfected control mice, were inoculated with B16 melanoma cells. Tumour development was inhibited in the infected animals. In the infected tumour-bearing mice, the tumour induction intervals were longer and the tumour size was subsequently smaller than in the control mice. Moreover, when the number of tumour cells in the inoculum was less than that required to produce 100% tumour incidence in the uninfected mice (<1 × 104 cells), significantly more of the mice with an infection of 2 months duration remained tumour-free. These results were significant at the P<0·05 level.
Latent Haemobartonella muris infection: its transmission and decline in an inbred, ectoparasite-free strain of Wistar rat
Authors: Bartlett Roberta , Pease Phyllis
Published: June 2009

Ectoparasite-free, SPF Italian Wistar rats were consistently found to carry a latent infection with Haemobartonella muris, activable by splen ectomy. In an inbred line this diminished and eventually ceased in six generations. Experimental infection from wild rats demonstrated that this was not apparently due to immunity.
Environmental sodium regulates cutaneous sugar transport in a digenean fluke
Authors: Uglem G. L.
Published: June 2009

Glucose uptake was examined in adult specimens of Proterometra macrostoma (Trematoda: Digenea) recovered from the stomach (endoparasites) and gills (ectoparasites) of longear sunfish, Lepomis megalotis. The endoparasitic forms transported glucose directly through the external body surface by Na+-independent, facilitated diffusion, but the ectoparasites absorbed glucose by free diffusion alone. To determine how this transport function is regulated, cercariae were incubated in solutions having Na+ concentrations normally found in fish gut (50 mM) and in fresh water (0·5 mM). Glucose transport capacity was retained in 50 mM Na+, but disappeared in worms incubated for 1–3 days in 0·5 min Na+. Returning worms from the latter solution to one containing 50 mM Na+ fully restored glucose transport within a day. By contrast, incubation up to 5 days in 0·5 mM Na+ had no effect on glucose transport in endoparasitic adults of P. macrostoma and cercariae of P. edneyi. Thus, cutaneous sugar transport function in the migrating larva of P. macrostoma is subject to indirect regulation by environmental Na+.
The induction of species-specific immunity against Schistosoma japonicum by exposure of rats to ultra-violet attenuated cercariae
Authors: Moloney N. A. , Webbe G. , Hinchcliffe P.
Published: June 2009

Single percutaneous immunizations of Fischer rats with 1000 ultra-violet attenuated Schistosoma japonicum cercariae induced 52–88% resistance to challenge 4 weeks later. Increasing this to 3 immunizations induced 90% resistance to challenge, and this level of protection remained undiminished for up to 40 weeks after vaccination. Rats vaccinated with gamma-irradiated S. mansoni cercariae were resistant to challenge with S. mansoni but not S. japonicum. Similarly rats vaccinated with u.v.-attenuated S. japonicum cercariae were not resistant to heterologous challenge. Thus irradiated vaccines are species-specific in both permissive and non-permissive hosts.
Biochemical and ultrastructural investigation of the effect of Stelazine (trifluoperazine) onHymenolepis diminuta(Cestoda)
Authors: Hipkiss Jayne B. , Skinner A. , Branford White C. J.
Published: June 2009

The effects of the phenothiazine, Stelazine, onHymenolepis diminutawere investigated. The cestode was incubated for 10 min at 37 °C with 1 mM trifluoperazine, in the presence and absence of Ca2+. Assay of brush border enzymes showed that drug treatment lowered the activities of alkaline phosphatase, Ca2+-ATP'ase, 5′-nucleotidase and type 1 phosphodiesterase. This occurred in parallel with a significant reduction in tegumental protein. Under these conditions gross changes in ultrastructural appearance and cellular organization were observed. There was a lack of ordered microtriches and the distal cytoplasm was absent. Glycogen granules were scattered throughout the cytoplasm within the subtegumental layer. The connective tissue also appeared to be in some disarray. The effects of Stelazine appeared to be dependent on time and were significantly increased when Ca2+was included in the incubation medium. Incubation with the less hydrophobic phenothiazine trifluoperazine sulphoxide had minimal effect on the integrity of the cestode. The results reported here support the premise that certain phenothiazines may be considered as potential cestocidal agents.
Occurrence and biochemical characteristics of cestode lymphocyte mitogens
Authors: Judson D. G. , Dixon J. B. , Skerritt G. C.
Published: June 2009

The cestodes Echinococcus granulosus, Taenia multiceps, T. pisiformis, T. hydatigena, Hymenolepis diminuta, Moniezia expansa and Anoplocephala perfoliata all produced substances that stimulated thymidine incorporation by whole blood lymphocyte cultures. This mitogenic activity was demonstrated in metacestode cyst fluids, live protoscoleces and scoleces, parasite culture supernatants, and extracts of adult parasites. T. multiceps metacestode cyst fluid mitogen adhered to, but would not pass through, cellulose dialysis tubing. This adherence was reduced or prevented by D-glucose and by proteins. The mitogen was weakly anionic. With Sephadex G75 gel filtration, its elution volume was greatly decreased when the elution buffer contained 0·5 M D-glucose. Mitogenic activity was protease resistant and could be separated by gel filtration from all the cyst fluid proteins.
Population dynamics in echinococcosis and cysticercosis: evaluation of the biological parameters of Taenia hydatigena and T. ovis and comparison with those of Echinococcus granulosus
Authors: Gemmell M. A. , Lawson J. R. , Roberts M. G.
Published: June 2009

An evaluation has been made of the biological and epidemiological parameters that determine the basic reproductive rates of Taenia hydatigena and T. ovis. These host-parasite systems are characterized by (i) no overcrowding in either host; (ii) no parasite-induced mortality of either host; (iii) no density-dependent constraint in the definitive host, but a strong, rapidly mobilized, short-acting immunity in the intermediate host and (iv) egg production which, in the natural environment, is high enough to prevent superinfection. It is considered that tapeworms with these characteristics are more stable to fluctuations in environmental conditions and to control measures such as dog dosing, than species which have a low egg production and infectivity such as Echinococcus granulosus. Reciprocal immunity exists between T. hydatigena and T. ovis in sheep. Exposure to T. hydatigena suppresses infection by T. ovis, but not by E. granulosus. This has important epidemiological consequences where these parasites co-exist.
Population dynamics in echinococcosis and cysticercosis: mathematical model of the life-cycles of Taenia hydatigena and T. ovis
Authors: Roberts M. G. , Lawson J. R. , Gemmell M. A.
Published: June 2009

It is shown that under the conditions that prevailed in New Zealand in the late 1950s, Taenia hydatigena was hyperendemic, the life-cycle being regulated by a density-dependent constraint in the form of acquired immunity, and T. ovis was rare. The control measures that caused Echinococcus granulosus, which was endemic at the time, to decline towards extinction reduced T. hydatigena and T. ovis to endemic status only. A non-linear integrodifferential equation model, which was previously linearized to describe the life-cycle of E. granulosus in dogs and sheep in New Zealand, is used to describe the life-cycles of T. hydatigena and T. ovis. The model is then used to compare and contrast the population dynamics of these three species. The model is used to demonstrate that the endemic steady state is structurally unstable, and may be asymptotically unstable to small perturbations. It is also shown that despite the lower infection pressure experienced by the intermediate host in the endemic state, the numbers of larvae in sheep may be higher than in the hyperendemic state. Finally it is shown that the partial success of the control measures against T. hydatigena may have caused an increase in the numbers and prevalence of T. ovis larvae in sheep due to the reciprocal immunity between the two species.
Hymenolepis diminuta: the role of the tail in determining the position of the worm in the intestine of the rat
Authors: Hopkins C. A. , Allen L. M.
Published: June 2009

One-worm infections ofHymenolepis diminutain rats had their strobila severed surgically, in the neck region, on day 14 of an infection. The scolex and remaining strobila survived but were recovered from a more posterior region of the intestine where small worms are attached during development. The movement to the new region was usually not complete in 24 h, but was complete by 72 h, and probably by 48 h. The operation, involving laparotomy and an incision in the duodenal wall which avoided severing the strobila, had no effect on the position of the worm but did depress the growth of the worm during the ensuing 24 h. It is suggested that (1) the preferred site forH. diminutais 30–50 % down the small intestine, (2) the worm monitors information about its position from all over its strobila and (3) as the worm grows, its position is determined by balancing the input of adverse information from its tail and head ends. The slowness with which surgically shortened worms return to the preferred site may be due either to delay in the worm ‘realising’ it has no tail, or to the location stimuli in the intestine being disturbed for 24 h by the operation.
Pseudechetus fimbriatus gen. et sp.nov., a caligid copepod from Kerala coastal waters
Authors: Prabha C. , Krishna Pillai N.
Published: June 2009

Pseudechetus fimbriatus gen. et sp.nov. from the throat of a carangid is described. The new genus has the closest resemblance to Parechetus Pillai from which it differs in the presence of 4 processes instead of 2 on the genital segment and a pair of processes on the abdomen instead of wings. The sternal fork carries accessory tines anteriorly making it a double structure.
An enzyme-linked immunosorbent assay (ELISA) for detection of antibodies toEncephalitozoon cuniculiand its use in determination of infections in man
Authors: Hollister Wafaa S. , Canning Elizabeth U.
Published: June 2009

An enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies toEncephalitozoon cuniculiin man, using spores derived from tissue culture as antigen. Negligible cross-reactions were found with other microsporidia of vertebrate or of invertebrate origin and there was no cross-reaction withToxoplasma gondii, using ELISA, immunoperoxidase or immunofluorescence staining. A high prevalence of antibodies toE. cuniculiwas found in patients suffering from schistosomiasis, malaria and neurological and psychiatric disorders, but not in healthy individuals.