bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of resistance toSchistosoma mansoniin mice by chemotherapy: migration of schistosomula in primary and challenge infections
Authors: Mastin Avis J. , Wilson R. A. , Bickle Q. D.
Published: June 2009

The fate of75Se-labelled schistosomula in mice treated at 24 h post-infection with either Ro 11–3128 or oxamniquine, compared to untreated controls, was followed by compressed organ autoradiography. No difference in the total percentage of schistosomula detected as foci was found between the three groups at each sampling time. However, the distribution of schistosomula was altered. In oxamniquine-treated mice there was a delayed migration from the skin relative to controls and fewer parasites in total appeared to reach the lungs. In Ro 11–3128 treated mice very few parasites left the skin. Ro 11–3128 treatment induces resistance to challenge whereas oxamniquine does not. The fate of challenge schistosomula in previously infected Ro 11–3128 treated mice was also compared to that in control mice. There was evidence for delayed or reduced migration from the skin of Ro 11–3128 treated mice. Significant death of challenge parasites occurred in the lungs, or post-lung sites in both control and treated mice. It was not possible to conclude that any of the late attrition was immune-dependent in the treated mice and the results appeared to indicate that a significant fraction of parasite death occurred at the skin stage.
Host specificity in eimerian coccidia: development ofEimeria vermiformisof the mouse,Mus musculus, inRattus norvegicus
Authors: Rose M. Elaine , Millard B. J.
Published: June 2009

The ability ofEimeria vermiformis, a coccidium which normally parasitizes the mouse, to develop in rats was investigated. The Rowett strain (Lac: RNU) rats were euthymic (rnu/+), treated or untreated with cortisone acetate, and athymic (rnu/rnu).E. vermiformiscompleted its development only inrnu/rnurats, which passed small numbers of oocysts capable of sporulating and infecting C57BL/6 mice. In thernu/+ rats, irrespective of cortisone treatment, development appeared to terminate with the completion of the asexual (schizogonic) stages since no gametocytes were recognized in the tissues and no oocysts were detected in the faeces. The findings are discussed with reference to the factors which govern host specificity.
Isolation ofTheileria parasitesfrom African buffalo (Syncerus caffer) and characterization with anti-schizont monoclonal antibodies
Authors: Conrad P. A. , Stagg D. A. , Grootenhuis J. G. , Irvin A. D. , Newson J. , Njamunggeh R. E. G. , Rossiter P. B. , Young A. S.
Published: June 2009

Antigenic differences between intra-lymphocytic theilerial parasites isolated from the blood of 18 African buffalo and grownin vitrowere assessed with anti-schizont monoclonal antibodies (mAbs). There was marked antigenic diversity both between isolates from different buffalo and between isolates taken at different times from the same buffalo. Many of the isolates from both wild and captive buffalo appeared to consist of mixed parasite populations. Some isolates were found by limiting dilution cloning and mAb testing to contain at least 3 or 4 distinct populations ofTheileria. Once cloned,Theileria-infected lymphoblastoid cell lines retained their mAb profiles during prolongedin vitrocultivation and, when recloned, the subclones had the same mAb profile as their parent clone. The implications of these results for further studies on buffalo-derived theilerial parasites are discussed.
American Leishmania spp: Formycin B treatment of cutaneous leishmaniasis in mice
Authors: Rojas Tamara , Avila J. L.
Published: June 2009

Using foot-pad infection of female C57BL/6, DBA/2J and NMRI-IVIC mice as an animal model for American cutaneous leishmaniasis (ACL), we evaluated the inhibitory effect of Formycin B (FoB) on the infection produced by 7 different Leishmania isolates. When treatment was initiated some days, or even some weeks, after infection a significant leishmanistatic effect was detected on mice infected with all Leishmania isolates, which reached 30–55 weeks for some isolates. The optimal dose schedule was 1·25 mg/kg body weight/day, injected intraperitoneally for 20 consecutive days. Significant differences in the sensitivity of various Leishmania spp. to FoB were found, either in vivo, or in vitro where a high [3H]FoB incorporation rate was found only for certain Leishmania isolates. The low toxicity of this drug and the sensitivity of the 7 Leishmania isolates tested suggest that FoB could be useful in the treatment of ACL.
ClinicalTrypanosoma rangeliinfection as a complication of Chagas‘ disease
Authors: Guhl F. , Hudson L. , Marinkelle C. J. , Jaramillo C. A. , Bridge D.
Published: June 2009

Laboratory studies on a group of 20 patients from the Rio Negro Valley, Colombia selected for detailed study showed that 14 gave antibody reactions on immunoassay consistent withTrypanosoma cruziorT. rangeliinfections. Four were diagnosed as havingT. rangeliinfection, 4 had mixed infections and 6 were infected withT. cruzialone. Immunoprecipitation analysis showed that sera fromT. crwzi-infected patients recognized a similar range of trypomastigote-derived polypeptides as sera from patients in Brazil, and all of the Colombian sera reacted with the 160 kiloDalton (kDa) polypeptide associated with active infection. Although sera from patients withT. rangeliinfection alone gave a positive immunofluorescence or ELISA reaction withT. rangeli, they failed to bind to parasite polypeptides by either immunoprecipitation or Western blotting. Intriguingly, sera from patients with mixed infections consistently gave a stronger, but qualitatively similar, binding reaction in immunoprecipitation and Western blotting compared to sera from patients infected withT. cruzialone.
Resistance toOnchocerca lienalismicrofilariae in mice conferred by egg antigens of homologous and heterologousOnchocercaspecies
Authors: Carlow C. K. S. , Bianco A. E.
Published: June 2009

Embryonic stages of variousOnchocercaspecies have been used to stimulate resistance in CBA mice to challenge injections with the microfilariae ofOnchocerca lienalis. Comparable levels of resistance to challenge (29–37% reductions) were conferred by living, freeze-killed, or sonicated organisms administered with Freunds‘ Complete Adjuvant (FCA). Antigens extracted in saline, or with the detergent sodium deoxycholate, were also protective. Adjuvants enhanced the protective effect, particularly FCA (78% reduction), Freunds‘ Incomplete Adjuvant (74% reduction), aluminium hydroxide (70% reduction) andBordetella pertussis(70% reduction). Detergent extracts prepared from intact embryos withn-octyl glucoside also stimulated significant levels of protection against microfilarial challenge when given with FCA (37–45% reductions). Levels of resistance induced by immunizations with intact organisms were greatest following subcutaneous (s.c.) injection over the neck or by intramuscular inoculation. Soluble extracts were also particially effective given by s.c. inguinal or intraperitoneal injection. A time-interval of greater than 3 weeks between the completion of immunization and challenge was required for the expression of immunity. Cross-protection against challenge withO. lienalismicrofilariae was also afforded to mice by immunization with intact embryos or detergent extracts ofOnchocerca gutturosa(45 and 34% reductions),Onchocerca gibsoni(66 and 47% reductions) orOnchocerca volvulus(58 and 41% reductions). It is concluded that the embryonic stages of both human and animal parasites provide a source of cross-protective antigens of value in studies on resistance toOnchocercamicrofilariae in experimental hosts.
The electrophysiology of the somatic muscle cells ofAscaris suumandAscaridia galli
Authors: Wann K. T.
Published: June 2009

The electrophysiological properties of the bag region of the somatic muscle cells ofAscaris suumandAscaridia galliwere studied using intracellular techniques. ForAscarismuscle cells, the mean resting membrane potentials at 20 and 37°C were −29·9 and −33·8 mV respectively, and the average input conductance was 2·12 μS. For the muscle cells ofA. gallisimilar values were obtained. For example, the mean input conductance of these cells was 2·84 μS at 20°C. HealthyAscarismuscle cells at near physiological temperatures show both spontaneous depolarizing and hyperpolarizing activity and, in cells close to the nerve cords, rhythmic large amplitude (approximately 30 mV) action potentials are observed. Such action potentials, which are very sensitive to temperature variations, originate in the muscle cells. In contrast the muscle cells ofAscaridiaare quiescent. The rhythmic action potentials ofAscarisare resistant to tetrodotoxin (TTX) (≤ 10−6M), verapamil (10−4M) and cinnarizine (10−4M), but are blocked irreversibly by 22, 23 dihydroavermectin B1a(10−7to 5 × 10−6M). GABA, and the GABAAreceptor agonists, muscimol and isoguvacine, hyperpolarize and increase the input conductance of bothAscarisandAscaridiamuscle cells. The antagonists+bicuculline and picrotoxin were not effective in modulating the spontaneous hyper polarizations ofAscarismuscle cells, and picrotoxin (10−4M) was not effective in altering the response to GABA (5 × 10−6M). The significance of the results is discussed briefly.
Interaction of epimastigote and trypomastigote forms ofTrypanosoma cruziwith chicken macrophagesin vitro
Authors: de Meirelles M. N. L. , de Araujo Jorge T. C. , de Souza W.
Published: June 2009

Chicken macrophages, obtained by cultivation of blood monocytes, were infected with epimastigote and bloodstream trypomastigotes of the Y and the CL strains ofTrypanosoma cruzi. The percentage of infected cells and the mean number of parasites per cell were determined after 2, 6, 12 and 24 h of parasite–cell contact. After 6 h of contact about 80% and 40% of the macrophages were infected by trypomastigotes of the Y and CL strains respectively. After longer periods of contact almost all macrophages were infected by Y trypomastigotes while only about 60% were infected by those of the CL strain. After 2 h of contact almost all macrophages were infected by CL epimastigotes while only about 50% were infected by Y epimastigotes. After 6 h of contact almost all macrophages were infected by epimastigotes of both strains. These results are discussed taking into consideration differences between parasites of the two strains and between the two developmental stages of theT. cruzilife-cycle.
The use of enzyme electrophoresis for the identification of the species of Eimeria present in field isolates of coccidia
Authors: Chapman H. D.
Published: June 2009

The electrophoretic mobility of glucose phosphate isomerase (GPI) has been used to identify Eimeria acervulina, E. praecox and E. mivati in isolates of coccidia from commercial sites in the United Kingdom. Mixtures of two or three species gave separate bands upon electrophoresis and each species could be identified provided that it formed at least 10–20% of the total number of oocysts present in a sample of 8 × 106 oocysts. The principal forms of GPI corresponded to the GPI of E. acervulina (H), E. praecox (H) and E. mivati (W) and were found in 38, 34 and 8 isolates respectively of the 46 examined. Three further variants of GPI are described.
Infection dynamics of Ichthyophthirius multifiliis
Authors: McCallum H. I.
Published: June 2009

The dynamics of infection of the fish host Poecilia latipinna by free-swimming tomites of the ciliate Ichthyophthirius multifiliis and the age-dependent survival of these infective stages are examined experimentally. Simple deterministic models are developed to aid the analysis of experimental results. Under defined laboratory conditions it is found that virtually all recently emerged infective stages successfully locate a host and that there appear to be no density-dependent constraints on parasite establishment on naive hosts. The overall reproductive success of the parasite is therefore shown to be determined by the proportion of infective stages encountering a host that are able to develop to form adult parasites. Variability between hosts in proportional establishment is postulated as the generating mechanism of the high observed heterogeneity in parasite burden/host. A model is described which predicts a simple relationship between mean parasite burden and variance in burden/host.
Ixodes ricinus L.: mast cells, basophils and eosinophils in the sequence of cellular events in the skin of infested or re-infested rabbits
Authors: Brossard M. , Fivaz V.
Published: June 2009

Some information on acquired resistance of rabbits againstIxodes ricinusticks has been obtained by comparing tissue changes and cellular infiltration during 2 successive infestations, with particular emphasis on the cells involved in immediate type hypersensitivity reactions: mast cells, basophils and eosinophils. More degranulated mast cells were observed in tick lesions 2 h after the beginning of re-infestation than in the first infestation and more degranulated basophils were present on the 5th day of re-infestation. Numerous eosinophils infiltrated the dermis, especially on the 5th day of the second infestation.
Intraerythrocytic schizogony ofTheileria annulata
Authors: Conrad P. A. , Kelly B. G. , Brown C. G. D.
Published: June 2009

The intraerythrocytic multiplication of two strains ofTheileria annulatawas studied with parasites maintained in stationary cultures and in the blood of infected cattle. In cultures established with blood from infected cattle 20–60% of singleT. annulatapiroplasms divided into quadruplet forms by day 6in vitro. Transmission electron microscopic studies ofT. annulatain culture showed that piroplasms possess intracytoplasmic food vacuoles and cytostomes during a pre-division trophozoite stage. The onset of intraerythrocytic multi plication was marked by the appearance of rhoptries and electron-dense plaques beneath the parasite's plasmalemmal membrane. The plaques developed into short segments of subplasmalemmal double membranes which were closely associated with the rhoptries. It was concluded that multiplication ofT. annulatain erythrocytes occurred by schizogony, as nuclear division preceded cytoplasmic division and the final separation of merozoites. The four merozoites produced by intraerythrocytic schizogony had the same ultrastructural features as theT. annulatamerozoites produced by intralymphocytic schizogony. Clusters of four merozoites, identical to those observed in stationary cultures, were also seen in the erythrocytes of persistently infected cattle and appeared to represent the most significant dividing forms ofT. annulata in vivo.
The potential role of blowflies in the transmission of taeniid tapeworm eggs
Authors: Lawson J. R. , Gemmell M. A.
Published: June 2009

In laboratory studies with 3 species of Calliphora more than half were shown to ingest eggs of Taenia hydatigena from the surface of clog faeces with a maximum of over 5000 eggs in 1 fly. Most eggs were voided within 48 h and between 38 and 48% of these eggs had lost their embryophores. In field studies carried out in the South Island of New Zealand, traps baited with dog faeces captured the following blowfly species in decreasing order of abundance: Hybopygia varia, Calliphora quadrimaculata, C. hortona and C. stygia. Peak numbers were trapped in January, February and March. Almost 25% of wild flies, caught after feeding for up to 3 mm on dog faeces naturally contaminated with taeniid eggs, had eggs in their intestine. When administered to lambs all 4 species of fly transferred infection. Lambs grazed in winter on plots near kennels that had housed dogs with patent infections of T. hydatigena acquired higher worm burdens than those grazed further away. The burdens were greater downwind of the prevailing wind. After removal of the dogs, blowflies caught in the vicinity contained taeniid eggs but the contents of pitfall traps did not. Blowflies, and to a much lesser degree the insects and dust caught on sticky traps during the presence of the dogs, transferred infection when administered to naive lambs.
Neuromuscular physiology of Hymenolepis diminuta and H. microstoma (Cestoda)
Authors: Thompson C. S. , Mettrick D. F.
Published: June 2009

The physiology of the neuromuscular systems in Hymenolepis diminuta and H. microstoma was studied in vitro using intact, adult worm and strips of worm body wall. Intact worms were insensitive to ionic changes in the in vitro buffering system. However, strips of body wall containing longitudinal muscles were extremely sensitive to ionic manipulation. In intact worms tension generated in the strobila had two components; small brief tension peaks up to 500 mg amplitude are superimposed on larger, longer peaks of up to 1200 mg amplitude. Removal of the scolex and neck region either failed to show significant changes in tension, or showed a reduction in amplitude but not of frequency. Muscle contraction of both H. diminuta and H. microsoma were qualitatively similar. In split-worm preparations the concentration of Ca2+ in the bathing solution significantly affected both spontaneous and evoked contractions in H. diminuta and H. microstoma; the addition of CaCl2 greatly reduced the amplitude and frequency of the contractions. The chloride salts of cobalt, barium, cadmium and manganese elicited prolonged contractions of the longitudinal musculature of both H. diminuta and H. microstoma. While CoCl2 was the most effective in stimulating muscle contraction, the magnitude of the response varied with the concentration of Ca2+ in the bath. The results indicate that peripheral inhibition is extremely important in cestode motor control and that extracellular calcium ions may regulate the peripheral inhibitory mechanisms.
The effect of temperature on the behaviour of the infective larvae of Trichostrongylus colubriformis
Authors: Wharton D. A.
Published: June 2009

The effect of temperature on the behaviour of the infective larvae of Trichostrongylus colubriformis has been investigated. Larvae acclimatized at 3°C or 20°C respond to sudden or gradual increases in temperature by coiling. Increased temperature may indicate a risk of exposure to desiccation and elicits a behavioural response which optimizes survival. Larvae are straight when inactive; coiling is an active response to specific stimuli. Larval activity is initiated by exogenous stimuli. Mechanical disturbance is a major stimulus, the response being affected by changes in temperature. Larvae acclimatized at 3°C or 20°C show a peak of activity at temperatures between 15 and 25°C.
Swimming behaviour of the cercaria ofTransversotrema patialense
Authors: Bundy D. A. P.
Published: June 2009

The spontaneous free-swimming behaviour of the cercaria ofTransversotrema patialensewas recorded using a high-speed micro-cinematographic technique. The sequential change in configuration of the cercaria was analysed quantitatively and the angular relationships of the cercarial components determined with respect to the trajectory of the organism. The cercaria swims tail-first while the tail stem oscillates through an arc of 100–120° with a frequency of 30 Hz at 24°C. The body region oscillates, almost exactly out of phase, through an arc of 180°C at the same frequency. The two furcae execute alternate effective and recovery strokes so that two symmetrical effective strokes are performed during each propulsive cycle. The Reynolds number of the swimming cercaria was approximately 2. The relative importance of viscous and inertial forces in cercarial propulsion is discussed.
The resistance to re-infection of cats repeatedly inoculated with infective larvae of Brugia pahangi
Authors: Denham D. A. , McGreevy P. B. , Suswillo R. R. , Rogers Rosemary
Published: June 2009

Seven microfilaraemic and five amicrofilaraemic cats which had been repeatedly infected with Brugia pahangi were challenged along with normal cats 28, 14 and 1 day before autopsy. The lymphatics of the amicrofilaraemic cats contained no female adult worms originating from the repeat infections and only two adult males (both from the same cat). Only 5·2 % of the worms in the control cats were recovered from the amicrofilaraemic cats. Most of the challenge worms were killed in the first 24 h. The microfilaraemic cats all contained fertile adult male and female worms derived from the repeated infection but in such low numbers as to indicate considerable resistance to infection. Compared to their controls 26·4% of the challenge worms were recovered. Analysis of the life-cycle stages recovered showed that in both groups there was attrition of all stages and that although a number of worms reached L5 these were all killed later in the amicrofilaraemic cats.
The effect of temperature on the survival and infectivity of the free-living larvae of Nippostrongylus brasiliensis
Authors: Hindsbo O.
Published: June 2009

The development, survival and infectivity of larvae of Nippostrongylus brasiliensis at 10 and 21 °C have been studied. In cultures developed for 1 weekat21 °C but stored at either 10 or 21 °C the mean recovery of larvae in 1·5 h Baermann sediment (46% and 42% of total eggs, respectively) and their infectivity (66% and 70% day 8 p.i. recovery, respectively) at 4 weeks of cultivation were similar. However, at 20 weeks of cultivation only a few larvae survived storage at 21 °C (1·4%) and the survivors showed very low infectivity (4·1%), whereas larvae stored at 10 °C retained most of their survival and infectivity rates (41% and 44%, respectively). In cultures developed and stored at 10 °C a lower mean proportion (17%) of the eggs was recovered as larvae at 4 weeks of cultivation. The mean infectivity rate of these larvae increased from 4 to 12 weeks of cultivation (18 % and 42 %, respectively) but was reduced at 20 weeks of cultivation (27 %). An increased proportion of adult female worms was recovered from rats infected with larvae from cultures showing poor development or survival and the fecundity of the adult females decreased in all groups as the storage time of the cultures was increased. Eggs from low fecundity adult worms showed normal development of larvae. The relation between survival, temperature in the habitat and the geographical distribution of the larvae of N. brasiliensis is discussed.
The in vitro cultivation of P. falciparum ookinetes, and their enrichment on Nycodenz® density gradients
Authors: Carter E. H. , Suhrbier A. , Beckers P. J. A. , Sinden R. E.
Published: June 2009

Employing a simple method of growing ookinetes of Plasmodium falciparum in culture, 40% of mature gametocytes convert to macrogametes, 4% reach the retort-form ookinete stage and 0·45% become mature ookinetes. A single-step gradient centrifugation method on 12·5% Nycodenz® enriches both gametocytes and ookinetes.
The mode of action of some benzimidazole drugs onTrichinella spiralis
Authors: Fornelio A. Criado , Caabeiro F. Rodriguez , Gonzalez A. Jimenez
Published: June 2009

In an attempt to find possible targets for benzimidazole action in muscle-stage larvae ofTrichinella spiralis, the effects of mebendazole and thiabendazole were testedin vivoby oral treatment of infested mice andin vitroby including these anthelmintics in an adequate maintenance medium containing decapsulated larvae. The effects of the anthelmintics on succinate dehydrogenase and fumarate reductase activities, measured in the mitochondrial fraction obtained from thein vivo- orin vitro-treated larvae showed that only thiabendazole causes significant inhibition of fumarate reductase activity. On the other hand, measurements of free glucose, glycogen reserves and soluble protein in the treated larvae indicate thatin vivo, mebendazole and thiabendazole clearly diminish free glucose levels, althoughin vitroonly mebendazole produces the same diminution. Both the glycogen and protein contents of the larvae remained unchanged after treatmentin vivoorin vitro.The importance of these findings with regard to a possible site of action for mebendazole and thiabendazole is discussed.
Physiological and morphological changes associated with recovery from anabiosis in the dauer larva of the nematode Anguina agrostis
Authors: Preston Christine M. , Bird A. F.
Published: June 2009

Morphological and physiological changes that occur during the rehydration of 2nd-stage infective larvae (L2) of Anguina agrostis are described. The first signs of motility, after 2 days of dehydration, were observed 0·5 h after rehydration and 90 % of the nematodes were moving within 15 h. Anabiotic A. agrostis were able to withstand repeated dehydration and rehydration. These procedures caused A. agrostis to accumulate large lipid droplets, which showed most clearly in the tail region. By means of a double labelling technique, it was shown that cuticle permeability of anabiotic L2 of A. agrostis initially increased slightly during rehydration. This was followed by a sharp decrease in permeability between 1 h and 8 h from the start of the experiment. A slower decline in permeability occurred between 8 h and 16 h and little further decrease occurred between 16 h and 24 h. The results are discussed in relation to the possible involvement of the epicuticle.
Biomphalaria glabrata: changes in calcium reserves following parasitism by larval Schistosoma mansoni
Authors: Shaw M. K. , Erasmus D. A.
Published: June 2009

Larval Schistosoma mansoni have been shown to induce morphological changes to the internal calcium reserves (in particular the calcareous inclusions in Type A calcium cells and to the inner, nacreous layer of the shell) of Biomphalaria glabrata within 48 h of miracidial penetration. Control experiments have shown that these changes were not due to either the experimental procedures used, mechanical damage or to starvation effects. The effects were, however, analogous to experimentally induced acidosis, suggesting that the rapidly transforming miracidium-sporocyst quickly induces changes in the host's metabolism, presumably by the production and release of CO2 and waste metabolites into the haemolymph.
Transient non-susceptibility toSchistosoma mansoniassociated with atrial amoebocytic accumulations in the snail hostBiomphalaria glabrata
Authors: Richards C. S. , Minchella D. J.
Published: June 2009

In someBiomphalaria glabrata–Schistosoma mansonicombinations snails are susceptible to infection as juveniles, but have variable susceptibility as adults. These snails become non-susceptible at the onset of egg-laying and typically revert to susceptibility in old age. Certain stocks ofB. glabratahave the capacity to form amoebocytic accumulations in the atrium, and this ability is under genetic control. The atrial amoebocytic accumulations are transitory, typically appearing at onset of egg-laying and disappearing after a few months. A snail stock which has genetic tendencies for both adult variable susceptibility and atrial amoebocytic accumulations was studied. An association between the time of occurrence of adult non-susceptibility and atrial accumulation is revealed as snails never became infected withS. mansoniwhen amoebocytic accumulations were present. Developing parasites, however, were not necessarily encapsulated and destroyed by amoebocytes. Some sporocysts were able to delay development until the amoebocytic accumulations disappeared. The timing of atrial amoebocytic accumulations and resulting transient non-susceptibility in this host-parasite combination could influence snail population dynamics.
Ascaris lumbricoides infection in pre-school children from Chiriqui Province, Panama
Authors: Holland Celia V. , Crompton D. W. T. , Taren D. L. , Nesheim M. C. , Sanjur Diva , Barbeau Irma , Tucker Katharine
Published: June 2009

An epidemiological survey of intestinal parasitic infections was conducted in a sample of 203 children aged 3–5 years from a semi-urban and a rural community in Chiriqui, Panama, in 1983–4. On the basis of stool examinations, the prevalences of Ascaris lumbricoides, Trichuris trichiura, hookworm, Giardia intestinalis, Entamoeba spp. and Strongyloides stercoralis were found to be 27, 34, 14, 15, 5 and 4% respectively. The results from children from the two communities were compared. Polyparasitism occurred significantly more often in rural than semi-urban children. Following anthelmintic treatment with levamisole, the numbers of A. lumbricoides passed/child were recorded and the frequency distribution of the parasite was observed to be highly aggregated with a variance to mean ratio of 10·2. For A. lumbricoides, relationships between worm burden, worm biomass and egg production were investigated. In the data analysis, an attempt was made to explore the influence of numbers of male worms on egg production. The results are compared with those obtained during other recent studies on the epidemiology of A. lumbricoides infection in other countries.
Plasmodium vivax malaria in the common marmoset, Callithrix jacchus: adaptation and host response to infection
Authors: Mitchell G. H. , Johnston D. A. , Naylor B. A. , Knight A. M. , Wedderburn N.
Published: June 2009

Infection with Plasmodium vivax was established in splenectomized Callithrix jacchus marmosets by inoculation of parasitized blood from Aotus trivirgatus carrying the Vietnam Palo-Alto line of P. vivax. Subsequent blood passage through intact marmosets resulted in higher peak parasitaemias (about 1% of red cells infected) and the loss of stainable Schüffner's dots in infected cells. Primary infections with the adapted line were patent for 74 days or more, and induced both a substantial antibody response, as determined by indirect fluorescence, and some lymphocytosis, but no marked anaemia. Marmosets which had recovered from their primary infection (or in which it was drug-cured) suffered abbreviated patency with low-grade parasitaemia on re-infection.
Origins and organization of genetic diversity in natural populations ofTrypanosoma brucei
Authors: Cibulskis R. E.
Published: June 2009

Experimental work has established that a sexual process can occur in African trypanosomes (Jenni, Marti, Schweizer, Betschart, Le Page, Wells, Tait, Paindavoine, Pays & Steinert, 1986; Paindavoine, Zampetti-Bosseler, Pays, Schweizer, Guyaux, Jenni & Steinert, 1986; Tait, personal communication). However, the role of the process in natural populations of trypanosomes is poorly understood. This paper considers what information can be gained from analyses of isoenzyme polymorphism. A cladistic approach is used to help determine whether trypanosome diversity could have been produced by mutation alone. When applied to three East African populations ofTrypanosoma bruceiit provides evidence that some diversity has arisen through a sexual process; this explains the variation observed within a locality and can account for the evolution of differences between localities. However, the extent to which genetic exchange currently operates is less clear. Analysis of genotype frequencies indicates that agreements with Hardy-Weinberg expectations can be obtained even if genetic exchange exerted no influence over genotype frequencies. Moreover, analysis of joint locus frequencies reveals disequilibrium between loci and that trypanosome populations may be lacking several genotype combinations. Thus, genetic exchange may not occur sufficiently frequently, or in such a way as to break up associations between loci. The relevance of these observations to the evolution of strain differences withinT. bruceiis discussed.
Attempts to protect goats against challenge withTrypanosoma vivaxby initiation of primary infections with large numbers of metacyclic trypanosomes
Authors: Vos G. J. , Moloo S. K. , Nelson R. T. , Gardiner P. R.
Published: June 2009

Attempts were made to immunize goats by infection with large numbers of metacyclic trypanosomes of a clone ofTrypanosoma vivax, followed by chemotherapy. Five groups of 6 goats each were infected intradermally with 5 different doses of cultured metacyclics ofT. vivax, ranging from 102to 106trypanosomes/goat. Four weeks after infection, the goats were treated with 10 mg/kg diminazene aceturate (Berenil, Hoechst A.G.). Three weeks after treatment, 3 goats in each group were challenged intradermally with 104homologous metacyclics derived from culture. The remaining 3 goats in each group were challenged by 20 tsetse infected with the homologous clone. Five out of 30 goats were resistant to homologous challenge; 4 of the goats that had been challenged with cultured parasites, and 1 that had been challenged by tsetse. In each group 1 goat was protected. Protection was therefore not apparently influenced by the number of trypanosomes used to establish the primary infection. In another experiment, 6 goats were each infected by feeding 100 tsetse on the goats for 15 consecutive days. Three weeks after infection the goats were treated with Berenil and 3 weeks later challenged by 20 tsetse infected with the homologous clone. Three out of the 6 goats resisted challenge. The susceptible goats in both experiments, however, showed a reduction in the peak of parasitaemia following challenge compared with both challenge controls and the initial infections. Lytic antibodies to cultured metacyclics ofT. vivaxwere detected in goats that resisted challenge after a primary infection with cultured metacyclics, and in resistant and susceptible goats after a primary infection by tsetse. All infected goats produced lytic antibodies to live bloodstream forms, as well as antibodies to bloodstream form lysates (demonstrated by ELISA). It is suggested that the immunity that had been induced in some of the experimental animals is due to antibody responses to both metacyclic and bloodstream variable antigen types (VATs) expressed during infection.
The host—parasite relationship ofSchistosoma haematobiumin CBA mice
Authors: Agnew A. M. , Lucas S. B. , Doenhoff M. J.
Published: June 2009

The host—parasite relationships of two geographical isolates ofSchistosoma haematobiumin CBA mice are described and compared to previous reports on this parasite in other experimental hosts and in man. The mean percentage establishment of worms in mice was 17% and was not affected by the age or sex of the host. Adult worm burdens remained constant over 20 weeks, but were reduced after 18 months of infection. Male and female worms reached mean maximum lengths of 4·78 and 5·9 mm respectively. Egg laying commenced 9·5 weeks after infection and eggs accumulated in the tissues throughout the period of infection. A large increase in the rate of egg accumulation occurred coincidental with the appearance of eggs in the bladder of some mice. Faecal eggs were first observed in some mice at 12·5 weeks and most mice excreted a few eggs by 17 weeks p.i. (post-infection). Eggs were not found in the urine of infected mice. Excreted eggs and eggs isolated from the livers of infected mice hatched, but the resulting miracidia were unable to infect appropriate snail hosts. The development of hepatic granulomas and egg-induced pathology in the bladder of mice is described.
Effect of repeated anthelmintic treatment on ability to detect predisposition of mice to Heligmosomoides polygyrus and Aspiculuris tetraptera (Nematoda) infections
Authors: Scott Marilyn E.
Published: June 2009

Several recent studies have demonstrated predisposition of certain humans to heavy gastro-intestinal nematode infections. This finding has been used to support the concept of community control of nematodes based on selective treatment of the few heavily infected individuals in the community. A mouse model has been used in this study to determine whether those individuals found to be ‘predisposed’ to heavy infection continue to regain heavy nematode infections following repeated anthelmintic treatments. Re-infection was examined over 3 intervals of 8 weeks in 52 mice and individual worm burdens attained following drug-induced expulsion were analysed. In the case of Heligmosomoides polygyrus, parasite numbers obtained after first treatment were only significantly correlated with those obtained after the second treatment. Re-infection levels in mice during the second and third re-infection periods did not correlate with parasite loads at the beginning of the study. In the case of Aspiculuris tetraptera, correlations after each re-infection period remained significant, although the magnitude of the correlation coefficient decreased with successive re-infection intervals. The data suggest that a selective control programme based on repeated screening to identify heavily infected individuals prior to each treatment would reduce the number of H. polygyrus in the host population 17–6% more than a single screening at the beginning of the control programme, and would reduce the number of A. tetraptera by 14% more than a single screening. Re-infection rates for H. polygyrus were shown to decrease with increasing mouse age whereas re-infection rates for A. tetraptera increased with increasing mouse age.
Study on genetic polymorphism of Leishmania infantum through the analysis of restriction enzyme digestion patterns of kinetoplast DNA
Authors: Angelici M. C. , Gramiccia M. , Gradoni L.
Published: June 2009

Twenty-nine Leishmania infantum strains characterized by different host source, tropism and belonging to 6 zymodemes, were examined by restriction enzyme analysis of kinetoplast DNA (kDNA) using 15 endonucleases. The enzymes which produced only one fragment revealed full identity between all the strains examined, while those producing many bands gave different electrophoretic patterns. They were interpreted with the aid of numerical analyses (cluster and multifactorial analysis). The results show a cline of genetic variability among the strains, the highest similarity being observed between most of the viscerotropic strains isolated from man, dog, black rat and sandflies. The strain agents of human cutaneous leishmaniasis show a varying degree of genetic divergence from this group, which appears more evident when characters from isoenzymes are considered.
Distribution patterns of Opisthorchis viverrini within a human community
Authors: Haswell-Elkins M. R. , Elkins D. B. , Sithithaworn Paiboon , Treesarawat Phattara , Kaewkes Sasithorn
Published: June 2009

This paper describes patterns of infection with Opisthorchis viverrini within a human community assessed by egg count, parasite-specific antibody levels and worm burden determined by expulsion chemotherapy. All three measurements increased significantly with age, reaching a plateau in young adults. There were no significant sex-associated differences in the prevalence or intensity of infection, antibody levels, or in the frequency of heavy worm burdens. A striking 81·5% of the total Opisthorchis population and 74% of the total egg output were expelled by the most heavily infected 10% of the humans sampled. This extreme over-dispersion, together with recent findings that hepatobiliary disease frequently accompanies heavy infections, argues that the priority for community-based parasite control programmes should be to maximize treatment and health promotion efforts toward heavily infected individuals.
Immunocytochemical and radioimmunometrical demonstration of serotonin- and neuropeptide-immunoreactivities in the adult rat tapeworm,Hymenolepis diminuta(Cestoda, Cyclophyllidea)
Authors: McKay D. M. , Fairweather I. , Johnston C. F. , Shaw C. , Halton D. W.
Published: June 2009

Standard indirect immunocytochemical techniques have been interfaced with confocal scanning laser microscopy (for whole-mount preparations) and epifluorescence microscopy (for cryosections) to investigate the occurrence and distribution of serotoninergic and peptidergic nerve elements in adultH. diminuta. Serotonin (5-HT)-immunoreactivity (IR) was widespread throughout the worm, occurring in the paired cerebral ganglia, transverse commissure, the 10 longitudinal nerve cords and in a plethora of small nerve fibres of the peripheral nervous system. An abundance of serotoninergic nerve cell bodies was found in association with the lateral nerve cords. The genital atrium and accessory reproductive ducts were richly innervated with serotoninergic nerve fibres. Thirty-five antisera to 20 vertebrate regulatory peptides and 1 invertebrate peptide (FMRFamide) were used to screen the worm for neuropeptide IR. Immunostaining was obtained with antisera raised to pancreatic polypeptide (PP), peptide YY (PYY), neuropeptide Y (NPY), substance P (SP), peptide histidine isoleucine (PHI), xenopsin (XP) and FMRFamide. The most extensive pattern of IR occurred with antisera to PP and PYY, IR being evident in the cerebral ganglia, transverse commissure, longitudinal nerve cords and in small nerve fibres that ramified throughout the parenchyma. A series of bipolar nerve cell bodies between the median nerve cords displayed PP/PYY-IR. The distribution of FMRFamide-IR was reminiscent of the PP/PYY pattern but was less extensive. Comparison of the serotoninergic and peptidergic nervous systems has revealed general similarities and some distinct differences, especially with regard to the distribution of immunoreactive nerve cell bodies. Quantitative data are presented on the levels of PP-, SP-, PH1-, and gastrin-releasing peptide (GRP)-immunoreactivities demonstrable in acid-alcohol extracts of whole worms. The highest level of peptide IR determined was recorded for PP.
Resistance to Millettia molluscicide in Biomphalaria glabrata: a quantitative genetical approach
Authors: Lam P. K. S. , Whitfield P. J. , Edge H.
Published: June 2009

This paper demonstrates the use of a quantitative genetical technique to assess genetic variance in molluscicide resistance in a Millettia thonningii-Biomphalaria glabrata system. Results indicated that there were significant genetic variances in both snail size and survival time in 10 p.p.m. molluscicide suspension. The possibility of wider applications of this technique in examining the genetic basis of molluscicide or pesticide resistance in target species is discussed.
Immunological relationships during primary infection with Heligmosomoides polygyrus (Nematospiroides dubius): dose-dependent expulsion of adult worms
Authors: Robinson M. , Wahid F. , Behnke J. M. , Gilbert F. S.
Published: June 2009

The survival of Heligmosomoides polygyrus was monitored during primary infections in female C57Bl10, NIH and BALB/c mice at low and high intensities of infection. Survivorship curves were fitted for each data set and analysed. C57Bl10 mice, given either low or high intensities of infection, harboured parasites for 28–37 weeks, heavier infections surviving marginally but significantly longer. Essentially the survivorship curves of H. polygyrus in C57Bl10 mice could be accounted for by senility, the increased probability of worms with a longer life-span occurring at high infection intensities and, possibly, by a contribution from host-protective immune mechanisms in the terminal stages of infection. The pattern of survivorship was different in NIH and BALB/c mice. NIH mice showed weak but significant density-dependent suppression of parasite loss and infections in this strain did not exceed 27·5 weeks in duration. Primary infections in BALB/c mice were briefer still and showed marked dependence on parasite density. Thus low-level infections lasted 10–15 weeks whereas heavier infections survived for 21–34 weeks. The data suggested that both strains developed host-protective responses to adult H. polygyrus and that parasite survival was curtailed earlier than would be expected if senility alone was involved. The hybrid strains (C57Bl10 × NIH)F1 and (B10G × NIH)F1 both expelled H. polygyrus in a dose-dependent manner, worm loss commencing within 10 weeks of infection. In some experiments worm loss was clearly evident by weeks 4 and 6. These hybrid strains showed gene complementation in that adult worms were cleared considerably earlier than in parental strains.
Differential targeting of dense granule proteins in the parasitophorous vacuole ofToxoplasma gondii
Authors: Achbarou A. , Mercereau-Puijalon O. , Sadak A. , Fortier B. , Leriche M. A. , Camus D. , Dubremetz J. F.
Published: June 2009

The biosynthesis and fate of 4 different dense granule proteins ofToxoplasma gondiiwere studied with 3 monoclonal antibodies raised against tachyzoites and 1 polyclonal antibody raised against a recombinant protein. These proteins have the following molecular weights: 27 kDa (GRA 1), 28 kDa (GRA 2), 30 kDa (GRA 3) and 40 kDa (GRA 4). All four proteins were found in dense granules by immunoelectron microscopy; inT. gondii-infected cells, they were found in the vacuolar network but, in addition, GRA 3 was also detected on the parasitophorous vacuole membrane. Therefore, dense granule contents undergo differential targeting when exocytosed in the parasitophorous vacuole. Metabolic labelling and immunoprecipitation showed that GRA 2 and GRA 3 were processed from lower molecular weight precursors, and that GRA 2 and GRA 4 incorporated [3H] glucosamine and are thus likely to be glycosylated.
In ovocultivation ofMicrophallus primas(Trematoda: Microphallidae) metacercariae to ovigerous adults and the establishment of the life-cycle in the laboratory
Authors: Saville D. H. , Irwin S. W. B.
Published: June 2009

This investigation reports for the first time the establishment of a trematode life-cycle in the laboratory usingin ovocultivation of the adult stage.Microphallus primasmetacercarial cysts were removed fromCarcinus maenascrabs and chemically excysted. Using a modification of the technique developed by Fried (1962) the released metacercariae were grown in fertile hen's eggs to ovigerous adult flukes. These were removed from the under surface of the chorio-allantoic membrane of chick embryos 5 days post-infection and the fluke eggs recovered were used to infect laboratory-rearedHydrobia ulvaesnails. When challenged against parasite-free crabs the cercariae released from the experimentally infected snails gave rise to metacercarial cysts that were again identified asM. primas.
Variation in resistance to isometamidium chloride and diminazene aceturate by clones derived from a stock ofTrypanosoma congolense
Authors: Peregrine A. S. , Knowles G. , Ibitayo A. I. , Scott J. R. , Moloo S. K. , Murphy N. B.
Published: June 2009

Nine clones were derived from a drug-resistantTrypanosoma congolensestock (IL 2856) and characterized in mice for their sensitivity to isometamidium chloride and diminazene aceturate. All clones were derived from the stock without drug selection and expressed high levels of resistance to isometamidium chloride (50% curative dose [CD50] values ranging from 1·5 to 5·1 mg/kg) and intermediate to high levels of resistance to diminazene aceturate (CD50values ranging from 5·1 to 21·0 mg/kg). By contrast, the isometamidium chloride and diminazene aceturate CD50values for a drug-sensitive clone,T. congolenseIL 1180, were 0·018 mg/kg and 2·3 mg/kg, respectively. For both drugs, there appeared to be significantly different levels in expression of drug resistance amongst the 9 clones derived from IL 2856. Isoenzyme analysis of 7 enzymes showed that all 9 clones expressed the same electrophoretic variants. Thus, all 9 clones were identical for these phenotypic markers. The clone which expressed the highest level of resistance to isometamidium in mice (IL 3270) was transmitted to Boran cattle via the bite of infectedGlossina morsitans centralis. IL 3270 produced an infection rate in tsetse of 5·0%. The resulting infections in cattle were shown to be resistant to intramuscular treatment with 2·0 mg/kg isometamidium chloride and 14·0 mg/kg diminazene aceturate. This contrasts with doses of 0·25 mg/kg isometamidium chloride or 3·5 mg/kg diminazene aceturate which are deemed sufficient to cure fully sensitive infections. Finally, 9 clones (subclones) were derived from IL 3270 and characterized in mice for their sensitivity to isometamidium chloride. Seven of the subclones expressed a significantly lower level of resistance to isometamidium than the parental clone and amongst the subclones there was significant variation in resistance. Thus, expression of a high level of resistance to isometamidium appears to be unstable in the rodent host and at least a component of the genetic determinant(s) for this drug-resistant phenotype is (are) likely to be unstable.