bluuebunny/crossref_metadata_2025 huggingface dataset:
Genomic cloning of human Echinococcus granulosus DNA: isolation of recombinant plasmids and their use as genetic markers in strain characterization
Authors: Rishi A. K. , McManus D. P.
Published: June 2009

A small, size selected (0·5–5·0Kbp) genomic DNA library has been constructed in the bacterial plasmid pAT153 using DNA extracted from a human isolate (Kenyan origin) of the hydatid disease organism, Echinococcus granulosus. A panel of taeniid cestode DNAs has been used in conjunction with hybridization and restriction-enzyme analysis to identify in the library two recombinant plasmids with Echinococcus-specific inserts and a single recombinant plasmid (coded pEG18) with a DNA fragment unique for E. granulosus. These, and other recombinant plasmids with E. granulosus DNA inserts, have been used in restriction endonuclease, Southern transfer and hybridization analysis to independently and repro-ducibly discriminate between the UK horse and sheep strains of E. granulosus; these probes may well prove of value for characterizing isolates from other endemic areas. The feasibility of using a cloned DNA fragment as the basis of a simple field test for distinguishing eggs of E. granulosus from those of other taeniid cestodes is discussed. The recombinant insert (approximately 2·3 Kbp in size) of pEG18 has a low copy number - estimated at approximately 26 - and it may not be sufficiently sensitive for practical use as a DNA probe in the identification of small numbers of E. granulosus eggs by molecular hybridization.
Functional morphology of the metacercarial cyst of Bucephaloides gracilescens (Trematoda: Bucephalidae)
Authors: Halton D. W. , Johnston B. R.
Published: June 2009

The metacercarial cyst wall of Bucephaloides gracilescens is bilayered. It comprises an inner granular layer of pepsin-resistant carbohydrate and protein material secreted by the parasite, and an outer fibrous and cellular capsule susceptible to pepsin digestion and elaborated by the host. The capsule of cysts from the orbits and nasal regions of the whiting host are substantially thicker than those from the cranial cavity. Cells in the outer portion of the capsule resemble fibrocytes engaged in the synthesis and secretion of collagen; collagen fibres form a loose meshwork in the intercellular space. The cells incorporated [3H]proline in vitro, but not [3H]tyrosine. The cells of the inner portion of the capsule are closely packed and possess pyknotic nuclei; desmosomes and cytofilaments are numerous and probably impart strength and elasticity, respectively, to the cyst wall. Host cells are necrotic at the interface with the inner cyst wall, possibly due to compression or isolation from oxygen and nutrients. Differences in the levels of incorporation of trace-labelled substrates by encysted metacercariae were related to the site of infection and to the thickness and permeability of the cyst wall.
The influence of water temperature and pH on the survival of Fasciola hepatica miracidia
Authors: Smith G. , Grenfell B. T.
Published: June 2009

Experimental studies on the survival of Fasciola hepatica miracidia show no evidence that miracidial mortality varies with the pH of the medium, at least in the range 6·0–8·0. On the other hand, miracidial mortality is shown to vary with both the temperature of the medium and the age of the larvae. The mean expected life-span of the miracidium decreases from about 35 h at 6°C to about 6° h at 25° C. The Gompertz survival function provides a good description of the miracidial survivorship curves over the range of temperatures used, and we describe, a maximum likelihood method of estimating the mean values of the parameters of this function, together with their approximate 95% confidence limits.
Borrelia crocidurae localization and transmission in Ornithodoros erraticus and O. savignyi
Authors: Gaber M. S. , Khalil G. M. , Hoogstraal H. , Aboul-Nasr A. E.
Published: June 2009

Borrelia crocidurae infection rates in different organs of adult Ornithodoros (Pavlovskyella) erraticus and O. (Ornithodoros) savignyi were studied at intervals during a 60-day period following an infective meal. The spirochaetes persisted in tick guts for 1 month, were first observed in other organs 1–7 days post-feeding, and persisted for 20–60 days in different organs. The ovaries, Gene's organ, testes and male accessory glands of only O. erraticus were infected. The infection rates in adult and immature O. erraticus and O. savignyi post-feeding on infected hamsters were 26·7–60·0% and 26·7–80·0%, respectively. Spirochaete trans-stadial transfer from originally infected larval O. erraticus to first-instar nymphs (N1) was 33·3%; to subsequent N2–N5 it was 40·0–60·0%. Infection rates in the resulting adults were 26·7% (males) and 46·7% (females). In O. savignyi, trans-stadial transfer from originally infected N1 to N2 was 26·7% and to subsequent N3–N7 13·3–33·3%; of the resulting males and females, 20·0% were infected. Transovarial transmission from female O. erraticus infected as adults occurred after the second gonotrophic cycle to 33·3–53·3% of the F1 larvae, and to 26·7 and 46·7% of the F1 males and females, respectively. All infected F1 females transmitted the spirochaetes to 26·7–73·3% of the F2 larval progeny after the first gonotrophic cycle. Transovarial transmission was not observed in O. savignyi.
Observations on the ability of repeated, light exposures toSchistosoma mansonicercariae to induce resistance to reinfection in Kenyan baboons (Papio anubis)
Authors: Sturrock R. F. , Cottrell B. J. , Kimani R.
Published: June 2009

Using groups of 4 baboons (Papio anubis), 21·0% of a trickle exposure of 480Schistosoma mansonicercariae/baboon (10/week for 48 weeks) were recovered as adult worms (Group A) compared with 72·6% from a single massive exposure of 2500 cercariae/baboon (Group C). Group B, exposed first to the trickle and then to the massive exposure simultaneously with Groups A and C, yielded a worm recovery of 54% which was slightly but significantly less than Group C. The trickle infection apparently induced a substantial resistance to light re-exposure, but only a partial, although significant, resistance to a massive re-exposure. In Group B, however, there was a marked reduction in the degree of gross pathology, despite high tissue egg production by the mature challenge worms. The parasitological results, in terms of resistance to reinfection by and development of pathology to a trickle infection, are not materially different from those obtained in studies using conventional heavy primary and challenge exposures withS. mansoni. The significance of these findings is discussed in relation to the epidemiology of human schistosomiasis mansoni in which heavy exposures are believed to be the exception rather than the rule.
Activity of quinfamide against natural infections of Entamoeba criceti in hamsters: a new potent agent for intestinal amoebiasis
Authors: Slighter R. G. , Yarinsky A. , Drobeck H. P. , Bailey D. M.
Published: June 2009

A novel tetrahydroquinolinyl ester, quinfamide, administered orally in multiple doses for 3 days had an ED50, of 0·25 mg/kg/day (total dose 0·75 mg/kg) for eradicating Entamoeba criceti in hamsters in several tests. It was significantly more active by direct comparison than 3 commercially available amoebicides and at least as active as 2 other esters of the parent compound, 1-(dichloroacetyl)-1,2,3,4-tetrahydro-6-quinonnol. After administration of a single dose, ED50, calculations for quinfamide averaged 0·9 mg/kg. Quinfamide was considerably more active than the other tetrahydroquinolinols, diloxanide furoate and teclozan, and it was approximately 1·5 times more active than etofamide; a statistical significance between the latter 2 drugs could be demonstrated in one of 4 tests. Administered prophylactically, quinfamide was shown to protect hamsters from re-infection with E. criceti. It also inhibited propagation of E. histolytica in vitro at a concentration of 20 /tg/ml. No adverse effects were noted in rodents after a single dose as high as 10 g/kg. Daily administration to monkeys of doses up to 500 mg/kg for as long as 37 days produced no pharmacological aberrations during or after medication; haematological studies and urine analyses were normal and no gross or microscopical tissue changes attributable to quinfamide were observed. No toxicity was revealed following acute (2 g/kg) and chronic (500 mg/kg/day × 31 days) administration of the drug to dogs and rats, respectively.
Fine structure of the spores of Minchinia chitonis (Lankester, 1885) Labbé, 1896 (Sporozoa: Haplosporida), a parasite of the chiton, Lepidochitona cinereus
Authors: Ball S. J.
Published: June 2009

A morphological study of the fine structure of the spores of Minchinia chitonis, a haplosporidian parasite of the chiton, Lepidochitona cinereus, is described. The spores contained a single nucleus, mitochondria, haplosporosomes, smooth endoplasmic reticulum, ribosomes and a large spherule (presumed Golgi apparatus). The spore wall was discontinuous at the spherule end, forming an opening covered by a lid which rested on a circumscribed flange. The flange of the spore wall and the lid were continuous in only one area which served as a hinge. The entire spore was encapsulated by epispore cytoplasm bounded by a strengthened membrane and extended to form 2 long projections, one at either end.
Interactions of the cysticercoids of Hymenolepis diminuta and Raillietina cesticillus in their intermediate host, Tribolium confusum
Authors: Gordon D. M. , Whitfield P. J.
Published: June 2009

This study was based on the experimental exposure of beetles to homologous and heterologous infections of Hymenolepis diminuta and Raillietina cesticillus. The results demonstrated that, for both species over the range of parasite densities employed, the presence of a primary infection had no effect on the establishment success of an homologous challenge infection. The establishment success of R. cesticillus cysticercoids was not affected by the presence of an H. diminuta infection. The existence of an R. cesticillus infection, however, severely reduced the establishment success of an H. diminuta infection. The reduction in H. diminuta establishment was greatest in R. cesticillus infections less than 10 days old. The plausibility of some of the mechanisms that are potentially responsible for the reduction in H. diminuta establishment success is discussed, as is the possible ecological significance of these results.
Ingestion of erythrocytic stroma by Plasmodium chabaudi trophozoites: ultrastructural study by serial sectioning and 3-dimensional reconstruction
Authors: Slomianny C. , Prensier G. , Charet P.
Published: June 2009

An ultrastructural study of numerous serial sections of Plasmodium chabaudi trophozoites at various growth stages, followed by 3-dimensional reconstruction, allowed us to describe more precisely the internalization process of the erythrocytic stroma, both in space and in time. Two endocytotic processes are apparent. (1) Pinocytosis — as soon as the merozoite has become a young trophozoite (ring stage), small double membrane-bound vesicles can be seen budding off around the whole periphery of the parasite. After the inner membrane of the vesicle has disappeared, the contents alter and a pigment crystal appears. (2) Cytostomal system — this phenomenon coexists with, and eventually replaces, pinocytosis. It consists of invagination of the membrane of the parasitophorous vacuole and of the plasmalemma, through a typical cytostome, in order to form a cytostomal vacuole. This extends into a long tube, the cytostomal tube, which eventually digitates. When the tube reaches its maximal size, the cytostome disappears and the tube remains open to the erythrocytic stroma by a simple aperture. A new cytostome can form elsewhere on the parasite surface and another tube can extend. Two or three such tubes can coexist in a trophozoite although only one cytostome is functional at one time. At the end of the tubes vesicles bud off, the contents of which become modified as described previously. The residual product of haemoglobin degradation is the malarial pigment.
Membrane transport of aromatic amino acids by Hymenolepis diminuta (Cestoda)
Authors: Pappas P. W. , Gamble H. R.
Published: June 2009

Aromatic amino acids (phenylalanine, tryptophan and tyrosine) are absorbed by Hymenolepis diminuta through a combination of mediated (non-Na+-sensitive) transport and diffusion. All 3 amino acids are accumulated against an apparent concentration difference during a 30-min incubation of tapeworms in 0·1 mM 3H-labelled amino acid. Inhibitor studies demonstrate that phenylalanine, tryptophan and tyrosine are mutually competitive inhibitors of the uptake of each other, and the uptake of these amino acids is inhibited by aliphatic amino acids but not by basic or dicarboxylic amino acids. The D- and L-isomers of aromatic amino acids are equally effective in inhibiting aromatic amino acid uptake. The data indicate that at least 3 amino acid transport loci are involved in aromatic amino acid transport by H. diminuta.
Inhibition of the growth and reproduction of the porcellanid crab Pachycheles rudis by the bopyrid isopod, Aporobopyrus muguensis
Authors: Van Wyk P. M.
Published: June 2009

A population approach was employed to study the effects of a bopyrid isopod, Aporobopyrus muguensis, on the growth and reproduction of its anomuran host, Pachycheles rudis. Indirect evidence, provided by the size-specific prevalence pattern, and direct evidence, provided by laboratory moult frequencies and moult-stage data, indicated that the frequency of moulting was reduced among parasitized crabs. Moult increments of parasitized crabs were less than those of non-parasitized crabs. Although parasitized female P. rudis were able to reproduce, their fecundity was substantially reduced. Parasitized female hosts appeared to be delayed in their attainment of sexual maturity. Once mature, these crabs produced significantly smaller size-specific clutches than those produced by non-parasitized female crabs. Because fecundity increases with size in P. rudis, the slower growth rates of parasitized female hosts may further limit their fecundity. Potential mechanisms by which A. muguensis limits the growth and reproduction of P. rudis are discussed.
Schistosoma mansoni: an ultrastructural examination of skin migration in the hamster cheek pouch
Authors: Crabtree Jean E. , Wilson R. A.
Published: June 2009

The hamster cheek pouch has been used to investigate the skin migration of schistosomula at the ultrastructural level. Parasites have been observed up to 72 h post-infection. Despite rapidly reaching the epidermal basement membrane schistosomula remain in an epidermal location for at least 40 h post-infection, by which time the acetabular glands and their ducts have been lost and the transformation from cercaria to schistosomulum completed. Entry into the dermis and exit from the skin via the blood vessels is therefore by mechanical means or by lytic secretions emanating from a source other than the acetabular glands. The head gland which persists in the dermal schistosomula is a probable source of such secretions. The observations suggest that the apical area and musculature of the head capsule are important in gaining access to the lumen of blood vessels.
Detection of cholinesterase in the nervous system of the oncomiracidium of a monogenean,Pricea multaeChauhan, 1945
Authors: Venkatanarsaiah J.
Published: June 2009

Cholinesterase activity has been demonstrated histochemically in the nervous system, tegumental and sub-tegumental musculature of the haptor and in the pharyngeal bulb of the oncomiracidium ofPricea multae. The presence of cholinesterase in the nervous system is attributed to neurotransmission and its presence in the tegumental and sub-tegumental musculature of the haptor and pharyngeal bulb is discussed. The nervous system of the oncomiracidium with respect to cholinesterase activity is described and is compared with the nervous system of the oncomiracidium ofProtopolystoma xenopodis.
Rat-dietary fructose and the intestinal distribution and growth of Moniliformis (Acanthocephala)
Authors: Crompton D. W. T. , Keymer Anne , Singhvi A. , Nesheim M. C.
Published: June 2009

The numbers, distribution in the small intestine, sexual development and growth (dry weight) of 5-week-old Moniliformis dubius (Acanthocephala) were investigated experimentally in adult, female CFHB rats fed on theoretically isoenergetic diets containing known amounts of fructose in combination with either maize-oil fatty acids or maize oil and two concentrations of casein. There was no obvious development of M. dubius when there was no fructose in the host's diet. In contrast, estimated consumption by the host of as little as about 2 g of fructose during the 5-week infection period was accompanied by marked sexual dimorphism and weight gain in most of the M. dubius present. The dry weights of M. dubius of both sexes were positively correlated with fructose concentrations ranging from 0 to 2·5 % (w/w) in the diets containing fatty acids. Significant, but not substantial, increases in M. dubius dry weight were observed as the dietary fructose concentration was raised to 12 % (w/w). Similar trends were observed when the fructose was offered to the infected rats with maize oil, but in general, fructose added to the fatty-acid based diets supported most M. dubius growth. Differences in the distribution pattern of the worms in rats fed on the fatty-acid or maize-oil based diets were observed and their possible significance is discussed.
Attempts to induce protective immunity in hamsters against infection by a liver fluke of man (Opisthorchis viverrini)
Authors: Sirisinha S. , Tuti S. , Tawatsin A. , Vichasri S. , Upatham E. S. , Bunnag D.
Published: June 2009

The development of acquired resistance in opisthorchiasis was studied in hamsters experimentally infected with Opisthorchis viverrini. The induction of protective immunity was attempted by first exposing adult female golden Syrian hamsters to 1,2 or 3 doses of infective metacercariae obtained from naturally infected cyprinoid fishes and then reinfecting them with 80 metacercariae. In other experiments, animals that were infected with 50 metacercariae were treated with praziquantel prior to being rechallenged in order to eliminate the flukes that had developed from the first infection. The effect of long-term chronic infections was also studied. Faecal egg counts were determined at weekly intervals from 4–5 weeks onwards. The animals were killed 2–3 months after the last infection for worm recovery, and terminal faecal egg output/g faeces/worm was calculated. The data showed that prior infection of animals with O. viverrini did not induce significant protective immunity against reinfection by the same parasite. Lack of protection was also noted in animals reinfected several times with small doses of metacercariae. However, under certain circumstances, prior infection could result in a significant reduction in the faecal egg output due to subsequent infection.
Relation of red cell membrane properties to invasion byPlasmodium falciparum
Authors: Dluzewski A. R. , Rangachari k. , Wilson R. J. M. , Gratzer W. B.
Published: June 2009

The effects of changes in red cell membrane properties on invasion byPlasmodium falciparumhave been studied by varying the cholesterol content and the intracellular concentration of polyamines. Increased cholesterol content is known to cause large reductions in the internal fluidity of the phospholipid bilayer and a change in its preferred direction of bending, but does not cause changes in gross mechanical rigidity. Polyamines, on the other hand, are thought to increase the cohesion of the membrane cytoskeleton and impede translational diffusion of transmembrane particles, as well as increase trie mechanical rigidity of the membrane. Cells with membranes augmented by 50% in cholesterol show no reduction in their susceptibility to parasitic invasion, whereas an increase in cytosolic polyamine (especially spermine) concentration leads to strong inhibition of invasion. In neither case is the development of the intracellular parasite affected. We conclude that it is the macroscopic, rather than the microscopic rheoelastic properties of the membrane that influence the invasion process. Depletion of membrane cholesterol leads to a substantial reduction in parasitaemia; it is suggested that this is linked to the reduced phosphorus incorporation into spectrin in these cells. Polyamines may exert a significant effect at physiological concentrations and the possibility must be considered that the elevated polyamine levels found in red cells in sickle cell disease may account for the protection againstP. falciparum.
Serological differentiation of the potato-cyst nematodes Globodera pallida and G. rostochiensis: partial purification of species-specific proteins
Authors: Schots A. , Bakker J. , Gommers F. J. , Bouwman-Smits L. , Egberts E.
Published: June 2009

Two major groups of heat-stable proteins have been purified by heat denaturation from homogenates of eggs of the potato-cyst nematodes Globodera rostochiensis and G. pallida. SDS-polyacrylamide gel electrophoresis of protein homogenates from 6 G. rostochiensis populations and 7 G. pallida populations revealed 2 bands specific for G. rostochiensis and 3 bands specific for G. pallida. Two-dimensional electrophoresis showed that the 2 bands specific for G. rostochiensis consisted of 2 polypeptides differing slightly in isoelectric point, as did one of the bands specific for G. pallida. Conventional antisera made against protein homogenates of either Globodera species showed a complete cross-reaction with the species-specific proteins. The perspectives of the differences in protein composition between G. rostochiensis and G. pallida, established in this study, for a quantitative differentiation of mixed field populations of the two Globodera species, involving monoclonal antibodies, are discussed.
Variation in class-specific humoral immune responses of different mouse strains to microfilariae ofDipetalonema viteae
Authors: Almond N. M. , Worms M. J. , Harnett W. , Parkhouse R. M. E.
Published: June 2009

The class-specific antibody responses of 3 strains of mice (C57/Bl10, BALB/C and CBA/N) known to vary in their ability to control the microfilaraemia which follows the subcutaneous transplantation of adult femaleDipetalonema viteaehas been investigated. The 3 mouse strains showed significant variation (a) in total levels of immunoglobulins and (b) in ability to recognize individual radio-isotope-labelled antigens as measured by coprecipitation. Within each mouse strain it was noted that antigens could vary with respect to the nature of the isotype of the antibody response which they elicited. Furthermore, by comparing results obtained from class-specific coprecipitation with surface ELISA it was found that a similar variation between responses to individual epitopes was also likely. No differences were observed in the humoral response of the 3 mouse strains which could explain the known resistance of the C57/B110 strain; reasons for this are discussed.
Interspecific characterization of several taeniid cestodes by isoenzyme analysis using isoelectric focusing in agarose
Authors: Allsopp B. A. , Jones A. , Allsopp M. T. E. P. , Newton S. D. , Macpherson C. N. L.
Published: June 2009

Taenia cestodes were obtained from 5 different definitive host species in Kenya and 175 different samples were examined by classical morphological methods and by isoenzyme analysis using isoelectric focusing in agarose. Gels were stained for 17 different enzymes and 3 of these were used in the construction of isoenzyme profiles. The samples fell into 25 zymodemes, and no zymodeme contained more than 1 species of Taenia, indicating that isoenzyme analysis can reliably be used for the identification of species of this genus.
Factors affecting the establishment of the caecal threadwormTrichostrongylus tenuisin red grouse (Lagopus lagopus scoticus)
Authors: Shaw J. L. , Moss R.
Published: June 2009

The resistance of captive reared red grouse toTrichostrongylus tenuiswas measured as the proportion of ingested infective 3rd-stage larvae which failed to develop to adult worms. Individual grouse showed wide, repeatable variations in resistance. Seasonal variations may also have occurred. Red grouse acquired little or no effective immunity to reinfection after challenge with a single dose of infective larvae. In trickle-dosed grouse, however, adult worms weakly inhibited the establishment of incoming larvae in an intensity-dependent fashion. Despite this, the proportion of larvae established in trickle infections was similar to that in single-dose challenges.
Properties of phenol oxidase inFasciola gigantica
Authors: Nellaiappan K. , Devasundari A. Fatima , Dhandayuthapani S.
Published: June 2009

Phenol oxidase ofFasciola giganticaexists both as the soluble form as well as the membrane-bound form. The membrane-bound enzyme is considered to be a tyrosinase type because it is capable of oxidizing mono- and diphenol and is inefficient in oxidizing paraphenols. The soluble enzyme is a laccase type showing more affinity to various diphenols and paraphenols. Membrane-bound enzyme exists as isoenzymes, showing 3 fractions, of which the slow-moving fraction is capable of oxidizing both 4-methyl catechol and catechol, whereas the two remaining fractions are specific to 4-methyl catechol only. Soluble enzyme exists as a single homogeneous form showing affinity to both mono- and diphenols. Inhibition of the enzyme by potassium iodide and mercuric chloride indicates the active tyrosyl and SH groups of the enzyme. Inhibition of the enzyme by sodium diethyl dithiocarbamate and phenyl thiourea indicates that copper is the prosthetic group of the enzyme.
Repair ofHymenolepis diminutaafter complement-mediated damage
Authors: Andreassen J. , Hoole D.
Published: June 2009

Seven and 56-day-oldHymenolepis diminutawere exposed to complement by incubation in 50% normal rat serum (NRS) in modified Hanks' saline. Ultrastructural studies revealed that the scolex/neck region remained relatively intact whilst in the strobila region microthrix denudation and loss of distal cytoplasm were observed. When complement-mediated damaged worms were incubated in vitro in 50% heat-inactivated normal rat serum (hiNRS) plus M199 or implanted into the duodenum of NMRI mice repair occurred, although destrobilated parasites were only foundin vivo. The regions undergoing repair contained tegumental protrusions, vesicles, large electron-lucent areas and large quantities of lipid. Microtriches were formed parallel to the parasite surface and were raised into a perpendicular position. It is suggested that the regenerative process exhibited after complement-mediated damage does not mimic totally the embryological development of the surface layer.
Intra-uterine larval development of the polystomatid monogeneans, Pseudodiplorchis americanus and Neodiplorchis scaphiopodis
Authors: Cable J. , Tinsley R. C.
Published: June 2009

Larvae of the monogeneans Pseudodiplorchis americanus and Neodiplorchis scaphiopodis develop within egg capsules retained in the uterus of the parent parasite. This study reveals adaptations for the storage and nutrition of infective stages which have no known precedent amongst other platyhelminths. The vitelline system is greatly reduced and appears to contribute little to embryo nutrition. An electron-dense ‘shell’ which encloses the newly formed embryos is subsequently replaced by a thin flexible sac composed of concentric layers of membranes which are derived from the uterus wall. Further membranes are added to this multi-laminate structure as the encapsulated embryos pass along the uterus, and this enables the sac to expand continuously as the larva inside it grows. The capsule lining extends into fine cytoplasmic processes which ‘plumb in’ to the larval tegument between ciliated cells. These connexions are packed with glycogen and appear to perform a placenta-like function. The unique adaptations correlate with the demands of the life-cycle. Large numbers of oncomiracidia (up to 300) can be packed, in membranous sacs, within the storage capacity of the uterus; direct transfer of nutrients from parent to offspring enables resources to be supplied over an extended period; and infective larvae can be maintained in readiness for an unpredictable opportunity for transmission.
Community control of Ascaris lumbricoides in rural Oyo State, Nigeria: mass, targeted and selective treatment with levamisole
Authors: Asaolu S. O. , Holland C. V. , Crompton D. W. T.
Published: June 2009

A study to compare effects of mass, targeted and selective chemotherapy with levamisole (Ketrax) as an action for the control of Ascaris lumbricoides was carried out in three communities in rural Oyo State, Nigeria. Selective treatment was applied in one village by treating the most heavily infected 20% of the inhabitants, targeted treatment in the second village involved children aged 2–15 years, while mass treatment was offered to all inhabitants excluding infants under 1 year and pregnant women in the third village. Recommended doses of levamisole were given in the villages, as described above, at 3-monthly intervals during a period of 1 year. Prevalence and intensity (epg) of A. lumbricoides infection were determined immediately before and 3 months after the period of intervention using a modified Kato-Katz technique. In the selective treatment village, no significant differences were found between the pre- and post-treatment egg counts (mean(±S.D.) epg 6776±10791 versus 4259±10909 respectively) of A. lumbricoides in the total population. In the targeted treatment village, significant differences were recorded in pre- and post-treatment egg counts for the total population (9057 ± 15 797 versus 2579±6529) among the children alone (10935±20094 versus 992±3175) and among the untreated adults (7742±9782 versus 4561±8798). In the mass treatment village, significant differences in pre- and post-treatment egg count values were also recorded (11 907±17220 versus 1489±5165). The intensity of Trichuris trichiura and hookworm infections among the villagers before and after intervention were not observed to have changed significantly regardless of selective, targeted or mass treatment.
Cloning of a repetitive DNA from the rickettsia-like organisms of tsetse flies (Glossina spp.)
Authors: Welburn S. C. , Gibson W. C.
Published: June 2009

Three DNA fragments from the genome of the rickettsia-like organism (RLO) symbiotic in tsetse flies (Glossina spp.) have been cloned. One of these fragments represents a family of highly conserved repeats, which occurs in RLO from all species of tsetse examined and has been amplified in the original RLO culture from which the DNA is cloned. This fragment serves as a highly sensitive and specific probe for the detection of RLO in tsetse midguts. As few as 30 organisms were unequivocally identified by dot blot hybridization of homogenized midgut preparations. Since the presence of RLO within tsetse midguts is associated with susceptibility to trypanosome infection, this technique provides a rapid and reliable method of assessing the potential susceptibility of a tsetse population to Trypanosoma brucei s.l. and T. congolense infections.
Strongyloides ratti: studies of cutaneous reactions elicited in naive and sensitized rats and of changes in surface antigenicity of skin-penetrating larvae
Authors: McHugh T.D. , Jenkins T. , McLaren Diane J.
Published: June 2009

This study provides the first quantitative assessment of the cutaneous reaction elicited in naive and sensitized rats by invading larvae of Strongyloides ratti. Parasites were identified in skin samples harvested from both naive and sensitized rats between 0·5 and 8 h following percutaneous infection, but were no longer visible at the site of invasion at 24 h. Mast cells, neutrophils, eosinophils and mononuclear cells recruited into the dermis in response to invading larvae were recorded and quantified. Cellular infiltrates were observed as early as 1 h post-invasion in naive/challenged skin, where total cell numbers were up to 3 times greater than in naive control tissue. Peak numbers of all cell types were recorded from 3 to 8 h in both naive/challenged and sensitized/challenged hosts. Interestingly, the reaction in sensitized/challenged rats was neither enhanced nor accelerated, a feature perhaps attributable to lack of recognition of parasite antigens by the host. This possibility was investigated by immunofluorescent labelling, which clearly demonstrated changes in the surface antigen profile of the parasite following penetration of the host skin both in vitro and in vivo. It is proposed that these changes in surface antigenicity constitute an evasive stratagem used by the parasite to deter the host from mounting a potentially lethal inflammatory response.
Echinococcus granulosus: a comparison of free amino acid concentration in hydatid fluid from primary and secondary cysts and host plasma
Authors: Hurd Hilary
Published: June 2009

A total of 28 components were detected in the free amino acid (FAA) pool of hydatid fluid from primary and secondary equine cysts, secondary ovine cysts and host plasma. Examination of data from equine cysts revealed that the majority of FAAs were present in significantly greater concentrations in secondary cysts, glycine being over 30 times more concentrated. Values for total carbohydrates and glucose did not, however, differ significantly and total protein content was greater in primary cysts. Comparison of the (FAA) pool of secondary equine and ovine cysts revealed strain variation. It was demonstrated that most FAAs were more concentrated in hydatid fluid than in the corresponding host plasma, many concentration ratios exceeding 10. The possible contribution that mediated amino acid transport across the cyst wall and parasite amino acid metabolism makes to the composition of the FAA pool was discussed. No significant plasma aminoacidaemia was associated with infection.
Comparison of different chemotherapy strategies against Schistosoma mansoni in Machakos District, Kenya: effects on human infection and morbidity
Authors: Butterworth A. E. , Sturrock R. F. , Ouma J. H. , Mbugua G. G. , Fulford A. J. C. , Kariuki H. C. , Koech D.
Published: June 2009

A comparison was made of the long-term impact of different methods of administration of chemotherapy (oxamniquine, 30 mg/kg in divided doses; or praziquantel, 40 mg/kg) on prevalence and intensity of Schistosoma mansoni infection in four areas in Kangundo Location, Machakos District, Kenya. In Area A, treatment was offered in October 1983 and again in April 1985 to all infected individuals. In Area H, treatment was offered in April 1985 to individuals excreting ≥ 100 eggs per gram (epg) of faeces. In Area H, treatment was offered in April 1985 to all infected school children, within the framework of the primary schools. In the witness area, Area W, treatment was given in April 1985, for ethical reasons, to a small number of individuals excreting ≥ 800 epg. Prevalence and intensities of infection were subsequently monitored at yearly intervals for three complete post-treatment years. In the Area S schools, clinical examination was also carried out at yearly intervals. Treatment of all infected individuals on two occasions (Area A) was the most effective and long-lasting way of reducing prevalence and intensity of infection. In this area, however, some earlier interventions had been carried out and pre-treatment intensities were lower than in the other areas. Treatment only of infected schoolchildren (Area S) also had a marked and prolonged effect, comparable to or better than treatment of individuals with heavy infections (Area H). Treatment of infected schoolchildren also caused a persistent reduction in the prevalence of hepatomegaly, and there was suggestive evidence from intensities of infection in community stool surveys (but not from incidence rates) of an effect on transmission. In all study areas, reinfection was most rapid and most intense among children. These findings are discussed in the light of theoretical considerations and of results from other studies, both on schistosomiasis and on intestinal helminths. We conclude that, in areas of low morbidity such as Kangundo, chemotherapy of schoolchildren only, at intervals of up to 3 years, is a satisfactory way of producing a long-term reduction in both intensity of infection and morbidity.
Covariance in parasite burdens: the effect of predisposition to infection
Authors: McCallum H. I.
Published: June 2009

Recently the phenomenon of predisposition to helminth infection has been reported in a number of studies: those individuals which are heavily infected before treatment with an anthelmintic tend also to acquire heavy parasite burdens following a period of reinfection. This correlation between parasite burdens in initial and reinfections is generated by differences between hosts in their exposure to infective stages and in their susceptibility to infection. Inter-host differences in these factors also generate the aggregated or over-dispersed parasite distributions that are usually observed. This paper uses probability theory to predict the correlation between initial and reinfection parasite burdens assuming that those inter-host differences which generate over-dispersion remain constant for a given individual between initial and reinfection periods. The predicted correlation is considerably greater than is observed in most published data sets. Over-dispersion is thus generated by variability between hosts which has components that remain constant between initial and reinfection and also components which vary between infection periods. The model is modified to account for those two sources of variability, and the result applied to published data to determine the contributions made by short and long-term factors to the observed distributions.
Genetic heterogeneity withinEchinococcus granulosus: isolates from different hosts and geographical areas characterized with DNA probes
Authors: McManus D. P. , Rishi A. K.
Published: June 2009

A segment of the ribosomal RNA gene ofSchistosoma mansoniand a DNA fragment specific toEchinococcus granulosus, cloned in plasmids, have been used as DNA probes to assess the extent of genetic variability withinE. granulosusand some distinct strains have been identified. The DNA analysis, involving restriction endonuclease digestion and Southern blot hybridization with the probes, did not demonstrate any significant genetic variation within the U.K. horse/dog or sheep/dog strains but confirmed the distinctiveness of the two strains shown in previous studies. The sheep/dog strain was shown to be cosmopolitan in its distribution and fertile bovine material originating from the United Kingdom, Kenya, Spain and India conformed to this strain by DNA hybridization. In contrast, cattle isolates from Holland produced markedly different DNA hybridization banding profiles indicating that cattle can harbour more than one strain ofE. granulosus. Similarly, it was shown that goats can harbour two different strains ofE. granulosus, the sheep/dog strain and a form which infects camels. The strain ofE. granulosusinfecting equines in Spain and Ireland is genetically identical to that infecting horses in the United Kingdom. There is also a different strain infecting pigs in Poland and Yugoslavia. This pig/dog strain appears to be very similar genetically to the forms ofE. granulosuswhich use camels and goats as intermediate hosts and is similar, though not identical, to the variant infecting Dutch cattle. It has been shown thatE. granulosusmaterial, fixed for a prolonged period in ethanol, or lyophilized, is amenable to DNA analysis and that it is possible to characterize the DNA of a single adult worm.
Eimeriaspecies infecting wood mice (genusApodemus) and the transfer of two species toMus musculus
Authors: Nowell F. , Higgs S.
Published: June 2009

Characteristics of four species ofEimeriaisolated fromApodemus sylvaticusare described. From oocyst morphology, three are identified asE. apionodes, E. hungaryensisandE. uptoni, the fourth being unnamed. Cloning demonstrated that oocysts ofE. hungaryensiswere polymorphic. Previous literature relating to the taxonomy is discussed and discrepancies outlined. Species isolated fromA. sylvaticuswere not transmissible toClethrionomys glareolus, but bothE. hungaryensisandE. apionodeshave been passaged through immunosuppressed laboratory mice, the former species more than 16 times. In bothA. sylvaticusand immunosuppressed laboratory mice, endogenous development ofE. hungaryensisoccurred mainly in enterocytes near the tips of the villi in the first half of the small intestine, with a few parasites in the rest of the small intestine and into the large intestine. The pre-patent period was 2 days in both hosts but oocyst output was higher in the natural hosts.E. apionodesparasitized enterocytes on the sides or at the base of the villi, mainly in the last 90% of the small intestine with a few parasites in the large intestine. The pre-patent period was 7 days. Parasites, probablyE. hungaryensisandE. apionodes, were also isolated fromA. flavicollis.
Cultivation of Blastocrithidia triatomae (Trypanosomatidae) on a cell line of its host Triatoma infestans (Reduviidae)
Authors: Reduth Dagmar , Schaub G. A. , Pudney Mary
Published: June 2009

Blastocrithidia triatomae parasitizes vectors of Chagas' disease and is very difficult to cultivate in conventional media. However, co-cultivation with a cell line of its host Triatoma infestans (TI-32; in Schneider's Drosophila medium supplemented with 20% foetal calf serum and 10% tryptose phosphate broth) led to vigorous growth at 24 or 28 °C without an adaptation phase. More than 60 primary cultures were initiated successfully without any failures. Subcultures could be started immediately at weekly intervals. The doubling time was similar in both the primary cultures (41 h) and the 33rd subculture (39 h). The importance of the reduviid cells for B. triatomae became clear after removal of the insect cells, when multiplication of epimastigotes stopped and mainly cysts were formed. Cysts produced in vitro were infective for reduviids. Scanning electron microscopy showed that B. triatomae attached to the host cells, inserted its flagellum into them and destroyed them.
Availability of caecal habitat as a density-dependent limit on survivorship ofLeptorhynchoides thecatusin green sunfish,Lepomis cyanellus
Authors: Ewald Julie A. , Nickol B. B.
Published: June 2009

Distribution ofLeptorhynchoides thecatus(Acanthocephala: Rhadinorhynchidae) among the pyloric caeca and the relationship between site and rate of maturation were studied in laboratory infectons of 10, 25 and 40 cystacanths fed to green sunfish,Lepomis cyanellus. After 1 week fish fed at each intensity had significantly different numbers of worms. By the 3rd week post-infection, parasites disappeared from the anterior portion of the intestine. At this time the mean numbers of worms recovered from 25 and 40-cystacanth infections were not significantly different. At the end of the 1st week, the area where caeca join the alimentary tract (between caecal area) and caeca numbered 6 and 7 contained significantly more worms than the other sites. By the 3rd week post-infection only caecum 7 contained significantly more worms, and at 5 weeks there was no significant difference between the number of worms present in any caecum or the between caecal area. Initially worms in the more intense infections matured more slowly, but by the 3rd week post-infection there was no significant difference in the states of maturity. The rate of maturation was not related to the site occupied.
Ingestion of host blood by the monogenean Pseudodiplorchis americanus: a quantitative analysis
Authors: Tocque K. , Tinsley R. C.
Published: June 2009

Pseudodiplorchis americanus infects the urinary bladder of a desert toad and feeds exclusively on blood, producing the iron-rich waste product haematin. The host, Scaphiopus couchii, retains dilute urine within the urinary bladder as a water store throughout hibernation and parasite waste will therefore not be eliminated. This study utilized atomic absorption spectrophotometry to quantify the iron within the urinary bladders of infected and uninfected toads after different periods of hibernation. During the first 4 months hibernation, no detectable iron, above that of the controls, was found in the urine and bladder tissue of infected animals, but after 5–6 months hibernation there was a small but not significant increase. The iron contained within most individual parasites was greater than that detected in the urine and bladder tissue of the host, and the total iron in each parasite infrapopulation was 3–83 times greater than the urinary bladder iron. This suggests that the parasites do not regurgitate their gut contents during host hibernation. The amount of iron in individual parasites increased with time after migration to the bladder and this was used to estimate the amount of blood ingested by P. americanus. At a controlled temperature of 25 °C, the estimated rate of ingestion increased from 0·33 μl blood/parasite/week by worms 2 weeks post-migration to a maximum of around 1·6 μl by worms 5 months post-migration. The rate of blood ingestion by older worms was also calculated as a function of the hibernation period (since this did not correspond to worm age) assuming complete gut evacuation at the start of hibernation. This provided maximum estimates of ingestion rate of 1·9–5·3 μl blood/parasite/week.
In vitro release of the anti-gonadotropic hormone, schistosomin, from the central nervous system of Lymnaea stagnalis is induced with a methanolic extract of cercariae of Trichobilharzia ocellata
Authors: Schallig H. D. F. H. , Sassen M. J. M. , De Jong-Brink M.
Published: June 2009

Infection with digenetic trematodes causes an inhibition or complete cessation of fecundity in their intermediate hosts, freshwater snails. It has been demonstrated in the host–parasite combination Lymnaea stagnalis–Trichobilharzia ocellata that the action of the female gonadotropic hormones upon their target organs is inhibited by the peptide schistosomin. Schistosomin is produced in the central nervous system of the snail and released upon parasitic infection. In order to study the in vitro release of schistosomin, a bioassay was developed. Central nervous systems were incubated with either an acetic acid or a methanolic extract of larval stages of Trichobilharzia ocellata (miracidia, mother sporocysts, cercariae). The incubation media were chromatographed using HPLC and released schistosomin (-like material) was tested for bioactivity in the calfluxin bioassay. The in vitro release of schistosomin was only induced with a methanolic extract of cercariae. The nature of the cercarial factor is discussed.
Immunosuppression by larvae ofMoniliformis moniliformis(Acanthocephala) in their cockroach host (Periplaneta Americana)
Authors: Lackie Ann M. , Holt Rohan
Published: June 2009

The results of 4 different assays for haemocytic immune responsiveness in the cockroach,Periplaneta americana, have shown that the presence of larvae ofMoniliformis moniliformiswithin the haemocoele depresses the insect's immune reactivity. Thus, the proportion of haemocytes that phagocytose fluorescent latex beadsin vivo, the proportion of haemocytes that can be stimulatedin vitroby theβ1,3-glucan, laminarin, to produce phenoloxidase, and the number of haemocytic aggregates producedin vivoin response to zymosan stimulation, are significantly depressed compared with control, unparasitized cockroaches. Also, when cockroaches are injected intra-haemocoelically with hatched oncospheres of the tapeworm,Hymenolepis diminuta, a higher prevalence and intensity of tapeworm larvae are found in insects already parasitized byM. moniliformis. All of these assays show that depression rather than total suppression of the immune response occurs; in the wild, this may be sufficient to ensure that the cockroach does not succumb to unrelated infections during the long developmental period of the parasite.