Three expression cDNA libraries from Trichinella spiralis worms 14 h, 20 h and 48 h post-infection (p.i.) were screened with serum from pigs experimentally infected with 20 000 T. spiralis muscle larvae. Twenty-nine positive clones were isolated from the 14 h p.i. cDNA library, corresponding to 8 different genes. A putative excretory-secretory protein similar to that of T. pseudospiralis was identified. Three clones corresponded to a T. spiralis serine proteinase inhibitor known to be involved in diverse functions such as blood coagulation and modulation of inflammation. Screening of the 20 h p.i. cDNA library selected 167 positive clones representing 12 different sequences. The clone with the highest redundancy encoded a small polypeptide having no sequence identity with any known proteins from Trichinella or other organisms. Fourteen clones displayed sequence identity with the heat shock protein (HSP) 70. HSPs are produced as an adaptive response of the parasite to the hostile environment encountered in the host intestine but their mechanism of action is not yet well defined. From the 48 h p.i. T. spiralis cDNA library, 91 positive clones were identified representing 7 distinct sequences. Most of the positive clones showed high similarity with a member of a putative T. spiralis serine protease family. This result is consistent with a possible major role for serine proteases during invasive stages of Trichinella infection and host-parasite interactions.

Taenia saginata cysticercosis causes financial losses to the beef industry and farmers, and represents a significant source for human infection in many countries. A case-control study was conducted to identify risk factors for bovine cysticercosis on farms in Switzerland. The case group (n=119) consisted of farms with infected cattle identified at slaughter in 2005 and 2006. Infections were confirmed by morphological or molecular diagnosis. The control group (n=66) comprised randomly selected farms with cattle slaughtered in the same period but with no evidence or history of infection. In personal structured interviews with the farmers, information regarding local surroundings and farm management was collected. Logistic regression revealed the following 5 factors as being positively associated with the occurrence of bovine cysticercosis: the presence of a railway line or a car park close to areas grazed by cattle, leisure activities around these areas, use of purchased roughage and organized public activities on farms attracting visitors. This information is considered useful for government authorities to direct control strategies as well as for farmers to take measures tailored to local situations.

The effect of waterborne zinc (Zn) on Gyrodactylus population dynamics was studied on isolated guppies maintained at concentrations ranging from 0 to 240 μg Zn/l. After 1 week pre-exposure to Zn, each fish was experimentally infected with 3 gyrodactylids and parasite numbers were recorded daily on each fish until the fish either died or recovered from infection. Parasite establishment was most successful at 0 and 240 μg Zn/l (97%) compared with the intermediate Zn concentrations. Low to moderate concentrations of Zn were beneficial to the parasite, as evidenced by the concentration-dependent increase in peak parasite burden on recovered fish up to 120 μg Zn/l. In contrast, 240 μg Zn/l may have been toxic to the parasite, as both peak parasite burden (in fish that recovered from infection), and maximum rate of increase of the parasite population (in fish that died) declined at this concentration. The combined effect of infection and Zn is harmful to the fish, because mortality of infected fish (but not uninfected fish) increased with increasing Zn concentrations. We suggest that the observed mortality occurs because of the inability of fish to continuously produce mucous that is a key factor for protecting fish from both waterborne Zn and ectoparasites.

The development of the exsheathed third-stage larva of Haemonchus contortus to the fourth stage in vitro has been investigated in half-strength Ringer's solution and in solutions with ionic concentrations similar to those found in the abomasum during normal secretion of acid and during heavy infestations of Haemonchus. The concentration of carbon dioxide required for the optimum development of the larva has been shown to be dependent on the pH of the medium. At a low pH the optimum pC02 is low and the larva is less sensitive to a range of carbon dioxide concentrations than at a pH near neutrality. Gastric mucin and histamine have been shown to have an inhibiting and a potentiating effect, respectively, on development, in media at pH 6.

The development of the free-living stages of Ostertagia ostertagi incubated at constant temperatures from 5 to 27 °C and in dung pats in the field was observed. The death rates were adequately described by a single exponential function and the distribution of times for development by a delayed gamma density function. The times of appearance of selected development stages such as maximum numbers of embryonated eggs and half the maximum number of infective larvae, were highly dependent on temperature. The relationships between these times and temperature were adequately described by the Arrhenius equation. The parameters of this equation and mean hourly temperatures recorded in dung pats in the field were used to predict development times in the field. A comparison of predicted and observed times showed that an initial delay accounted for a large proportion of the time required for development in dung pats, particularly the embryonation of eggs. This delay was attributed to lack of aeration associated with high moisture content of the dung pat.

Immunity to Eimeria maxima, judged by oocyst production resulting from a low challenge inoculum, was evident when the challenge was given as early as 3 days after the immunizing dose of 250 or 500 oocysts. Immunity was complete, i.e. no oocysts were produced, to challenge at 7 days after an initial inoculum of 500 oocysts, or at 14 days after 250 oocysts. Judged by the above criteria 250 oocysts of E. tenella did not induce immunity to challenge given at 3, 5, 7 or 14 days. The findings are discussed.

Following a 2–5 ml meal containing 2 g (80%) glucose and 30 mg methionine administered by stomach tube at 09.00 h, H. diminuta was found to change its position in the rat's intestine. Usually while the stomach contained food ≤ 45 %, by weight, of the tapeworm lay in the posterior 40 % of the small intestine, after the stomach was empty the reverse was true.

The effect of hyperosmotic fluid entering the duodenum was determined by injecting, following laparotomy, varying amounts of 80 % glucose and 1 ml of varying concentrations. A volume ≤ 0-4 ml of 80 % led to the death and expulsion of worms within 7 h, and 1 ml of < 50 % glucose also killed the worms.

The expulsion of 15 % of the tapeworms from rats given 2–5 ml hypertonic meal by mouth was correlated with the failure of the stomach in some rats to regulate the stomach emptying. Worms in these rats were found from 4 h onwards in the caecum and large intestine, and by 9 h in the faeces.

That the movement of worms, other than those expelled, was not caused by a sub-lethal flux of hyperosmotic fluid was shown by feeding an iso-osmotic meal to rats; the worms moved to a more posterior position during the day, but none was expelled.

Single worm infections in rats kept on a normal feeding regime until 07.00 h and then starved throughout the day also showed a posterior migration. Using a method which involved the simultaneous cutting of the small intestine into 5 cm sections, it was possible to show that this movement involved the whole worm, the scolex moving from a mean position 10–15 cm to one 20–25 cm from the stomach, and the terminal proglottid moving from approximately 75 cm to 95 cm from the stomach.

Worms in Wistar rats responded similarly to those in SPF CFE (Sprague Dawleys) with the exception that there was some evidence that the stomach emptying of a hyperosmotic meal was better controlled and hence a smaller percentage of the worms were expelled.

The results are discussed in relation to diurnal changes in the level of the external site location stimulus which other workers have shown to exist by surgically transplanting H. diminuta into the ileum.

The enthusiastic assistance of Miss Helen Stallard, B.Sc., and Miss Patricia Grant is gratefully acknowledged, and financial support from the Medical Research Council, London (Grant No. G967/164/T).

A 3000 bp cDNA insert (G6/1) from Giardia duodenalis, cloned into Escherichia coli is located on chromosome 3 of Giardia stocks which have 3 chromosomes detectable by field-inversion gel electrophoresis in the range 650–800 kb and on chromosome 3 and/or 4 of stocks with 4 chromosomes in this size range. The loss of this sequence from chromosome 4 but not chromosome 3 was associated with the induction of drug resistance in a previously sensitive laboratory stock. G6/1 appears to represent a single copy gene in Giardia as determined by hybridization of the probe to cleaved genomic DNA. Furthermore, the sequences flanking at least 12 kb of G6/1 are the same when G6/1 appears on both chromosomes 3 and 4. The cDNA encodes a protein associated with the nuclei of trophozoites during some stages of growth of the parasite. In a non-dividing culture, the antigen is associated with the nuclei of about 30% of trophozoites and fewer in a dividing culture. Three Giardia stocks with obvious chromosome rearrangements, which grow poorly and fail to divide normally, apparently lack the DNA sequence G6/1.

As a subject of investigation the Trematode fauna of British Birds does not appear to have aroused at any time much enthusiasm amongst British zoologists and as a result we owe the greater part of our knowledge of the subject to continental workers. The fact that our bird fauna is practically identical with that of the adjacent parts of Western Europe would lead us to expect that the parasites of our birds should not differ materially from those met with in the same species of birds on the continent. As a matter of fact, no species of bird Trematode hitherto recorded from this country can be regarded as peculiar to Britain, with the possible exception of Echinostephilla virgula Lebour, which, however, will almost certainly be met with in other localities later.

A mathematical model of the parasitic phase of the life-cycle of Ostertagia ostertagi in calves is described. The model is used in the re-analysis of previously published data from a long-term trickle infection experiment in which groups of calves were infected daily with graded doses of 3rd-stage (L3) larvae. The results of the analysis are consistent with the hypothesis that the observed changes in the intensity of infection in the calves were the result of a decline in the proportional establishment of ingested L3 larvae, and a rise in the death rate of the 5th-stage worms as the duration of exposure to infection increased. The proportion of ingested L3 larvae that become established in the mucosa can be described as an exponential decay function of the duration of the infection. Within the range of trickle intensities investigated, the function appears to vary independently of the level of exposure to infection. In contrast, the rate of mortality of the 5th-stage worms appears to be an increasing linear function of the total cumulative number of 3rd-stage larvae administered.

Arecoline hydrobromide was tested for its efficiency in causing dogs to purge and in removing hydatid worms by infecting, dosing and autopsying 157 dogs. Doses were given by mouth in water at various rates, by mouth in meat, and by subcutaneous injection.

The tabulated results indicate that the median efficiency of hydatid-worm removal, with doses of or above grain/10 lb. weight, are 95% or more. Dosing in meat is almost equally efficient but the action is slower, taking usually over 1 hr. instead of 15–30 min. Injections of arecoline caused purgation but not worm removal. Increasing the dosage rate above grain/10 lb. body weight increased the proportion of dogs that vomited and caused convulsions in some, but did not markedly increase efficiency in worm removal. The dose recommended for general use is grain/10 lb. body weight; though half or double this dose is about equally suitable. None of the dogs tested was killed by arecoline.

Repeated doses were given to see how many were required to ‘clear‘ a dog. Dogs usually gave negative results after three doses that caused purging.

Arecoline showed a similar high degree of efficiency against Taenia species and Dipylidium; usually removed about half the Toxocara specimens present, and had no significant effect against hookworms.

Solutions of arecoline were tested in vitro on isolated Taenia segments arranged to record. Solutions of 0.001% or more in Ringer's solution almost invariably caused extreme relaxation of the segment, its normal rhythmical contractions ceasing. The segments were not killed.

Arecoline hydrobromide appears to exert its anthelminthic action: first, by causing the muscles of cestodes to relax, so that the hold on the host's intestine is lost; secondly, by causing the host to purge, so that the detached worms are removed from the host's body.

The writer wishes to thank Sir Louis Barnett, Dr Hercus and other members of the Hydatid Committee for their interest and support. She especially thanks Miss D. Medley, Hydatid Assistant, who has carried out the heavy share of the infecting of dogs and handling of faeces. Thanks are also given to Mr L. K. Whitten, Agricultural Parasitologist, for technical advice; to Mr Grimmett, for analysing arecoline-content of pills; and to the various members of the Medical School staff who have given helpful advice.

This review presents a progression strategy for the discovery of new anti-parasitic drugs that uses in vitro susceptibility, time-kill and reversibility measures to define the therapeutically relevant exposure required in target tissues of animal infection models. The strategy is exemplified by the discovery of SCYX-7158 as a potential oral treatment for stage 2 (CNS) Human African Trypanosomiasis (HAT). A critique of current treatments for stage 2 HAT is included to provide context for the challenges of achieving target tissue disposition and the need for establishing pharmacokinetic–pharmacodynamic (PK–PD) measures early in the discovery paradigm. The strategy comprises 3 stages. Initially, compounds demonstrating promising in vitro activity and selectivity for the target organism over mammalian cells are advanced to in vitro metabolic stability, barrier permeability and tissue binding assays to establish that they will likely achieve and maintain therapeutic concentrations during in-life efficacy studies. Secondly, in vitro time-kill and reversibility kinetics are employed to correlate exposure (based on unbound concentrations) with in vitro activity, and to identify pharmacodynamic measures that would best predict efficacy. Lastly, this information is used to design dosing regimens for pivotal pharmacokinetic–pharmacodyamic studies in animal infection models.

Macroparasites are almost always aggregated across their host populations, hence the Negative Binomial Distribution (NBD) with its exponent parameter k is widely used for modelling, quantifying or analysing parasite distributions. However, many studies have pointed out some drawbacks in the use of the NBD, with respect to the sensitivity of k to the mean number of parasites per host or the under-representation of the heavily infected hosts in the estimate of k. In this study, we compare the fit of the NBD with 4 other widely used distributions on observed parasitic gastrointestinal nematode distributions in their sheep host populations (11 datasets). Distributions were fitted to observed data using maximum likelihood estimator and the best fits were selected using the Akaike's Information Criterion (AIC). A simulation study was also conducted in order to assess the possible bias in parameter estimations especially in the case of small sample sizes. We found that the NBD is seldom the best fit for gastrointestinal nematode distributions. The Weibull distribution was clearly more appropriate over a very wide range of degrees of aggregation, mainly because it was more flexible in fitting the heavily infected hosts. Moreover, the Weibull distribution estimates are less sensitive to sample size. Thus, when possible, we suggest to carefully check on observed data if the NBD is appropriate before conducting any further analysis on parasite distributions.

New oral treatments are needed for all forms of leishmaniasis. Here, the improved oral efficacy of quercetin (Qc) and its penta-acetylated derivative (PQc) was evaluated in cutaneous leishmaniasis after encapsulation in lipid-core nanocapsules (LNCs) of poly(ε-caprolactone). Leishmania amazonensis-infected BALB/c mice were given 51 daily oral doses of free drugs (16 mg kg−1) or LNC-loaded drugs (0·4 mg kg−1). While treatment with free Qc reduced the lesion sizes and parasite loads by 38 and 71%, respectively, LNC-Qc produced 64 and 91% reduction, respectively. The antileishmanial efficacy of PQc was similar but not as potently improved by encapsulation as Qc. None of the treatments increased aspartate aminotransferase, alanine aminotransferase or creatinine serum levels. These findings indicate that when encapsulated in LNC, Qc and, to a lesser extent, PQc can safely produce an enhanced antileishmanial effect even at a 40-fold lower dose, with implications for the development of a new oral drug for cutaneous leishmaniasis.

We examined the patterns of composition and structure of parasite communities in the Mediterranean sparid fish Boops boops along a gradient of fish sizes, using a large sample from a single population. We tested the hypothesis that species forming the core of the bogue parasite fauna (i.e. species which have a wide geographical range and are responsible for recognizable community structure) appear early in the fish ontogeny. The sequential community development observed supported the prediction that core species appear in the fish population earlier than rare and stochastic species. There was also a strong correlation between the order of ‘arrival’ of the species and their overall prevalence. Six key species were responsible for recognizable community structure across size/age cohorts; the addition to this baseline community of key parasite species resulted in a nested structure that is linked to differential species abundance rather than fish size. Information on the life-cycles, distribution and host range of the parasites is used to explain the observed patterns of parasite community structure. We conclude that the small mouth size of B. boops coupled with suction feeding may provide a setting for passive sampling as a mechanism leading to non-random parasite community structure.

Common arthropod vectors for trypanosomes are flies, fleas and bugs. This study reports on an unknown trypanosome species isolated from naturally infected Haemaphysalis hystricis ticks, hereby, referred to as Trypanosoma KG1 isolate. The parasite has been successfully cultured in vitro with L929 or HEK 293T cell line as feeder cells. This trypanosome cannot survive in vitro without feeder cells. Following experimental infections of ticks, the trypomastigote-like and the epimastigote-like forms of this trypanosome could be detected by Giemsa-stained smears of the midgut and salivary glands of Ornithodoros moubata ticks which were made to feed on a culturing medium containing Trypanosoma KG1 isolate through an artificial membrane. Trypanosoma KG1 isolate could also be detected from Giemsa-stained smears of the haemolymph up to 30 days post-inoculation into the O. moubata haemocoel. Trypanosoma KG1 isolate cannot be propagated in laboratory animals including mice, rats, rabbits and sheep. A phylogenetic tree constructed with the 18S rRNA gene indicates that Trypanosoma KG1 is a member of the stercorarian trypanosomes.

The present findings apply to a particular area, the four northern counties of England, and must be viewed within the limits of the data presented.

Only one tick, Ixodes ricinus L., the so-called sheep tick, infests sheep and cattle in northern England. I. canisuga Johnston, alone or with I. ricinus, has been found on sheep dogs and foxes.

The distribution of the sheep tick in this region is markedly discontinuous, the total infested areas including only about one-fifth of the hilly country, to which the tick is almost exclusively confined.

In north-west Northumberland, tick distribution shows a significant degree of correlation with certain factors inherent in or influenced by the surface geology. Broadly speaking, where surface geology lends itself to relatively good natural drainage and soil, the grazing is relatively good and ticks are absent; and where surface geology results in relatively poor natural drainage and/or soil, the grazing is relatively poor (‘rough’) and ticks are present.

No consistent correlations between soil characteristics—i.e. pH, available phosphates and potash, soil textures, mechanical analysis and soil depth—and tick distribution have been found. Nor is there a consistent correlation- between quality of natural drainage and tick distribution. The interaction of soil and natural drainage factors, however, profoundly influences the character of the vegetation layer.

In the four northern counties, the same plant dominants occur on tick-infested and tick-free hill lands. Where grazing is rough ticks are usually present irrespective of whether the dominant plant is one of the rough grasses (Nardus, Molinia, Agrostis, Aira), bracken or heather; where grazing is relatively good (i.e. not rough), ticks are invariably absent.

Observations on a smaller scale show that the thicker, i.e. rougher, the vegetation layer, the denser the tick population and also the thicker the vegetation layer, the thicker the basal mat. On five plots it has been shown that there is a consistent positive correlation between mat thickness and tick population density: the thicker the mat,’ the denser the tick population irrespective of whether bracken or grass is the dominant. Thus the chief controlling factor in tick distribution is the physical character of the vegetation layer.

Haemolymph free amino acids (HFAAs) in adult Tenebrio molitor varied in concentration with beetle age. Between 9 and 30 days post-emergence the concentration range was 34–94 mM with a peak occurring in 15-day-old insects. Much of this age-related variation was due to changes in the concentration of a single amino acid, proline. An analysis of concentrations of individual HFAAs in 15-day-old beetles, following infection with metacestodes of Hymenolepis diminuta, revealed that changes in female insects are more marked than those occurring in males. In the former, changes occurred in the concentration of 9 amino acids (isoleucine, leucine, arginine, serine, threonine, tyrosine, phenylalanine, proline and alanine/citrulline) whereas in the latter only 4 amino acids were affected (threonine, glycine, histidine and arginine). It is suggested that H. diminuta may interact with the endocrine system of its beetle host.

Intracellular differentiation of Leishmania promastigotes to amastigotes is a critical step in the establishment of infection. In this report three related features of mexicana subspecies amastigotes were used to follow the differentiation of the parasites within macrophages. Early after infection, (a) parasites did not contain ultrastructurally recognizable megasomes, (b) cysteine proteinase activity of parasite lysates was not detected in gelatin-containing acrylamide gels, and (c) parasites were essentially resistant to L-leucine-methyl ester (Leu-OMe). Typical megasomes were first identified on the 5th day, were more prevalent on day 7, and underwent swelling in macrophages exposed to Leu-OMe. Cysteine proteinase activity was first detected on day 3 and increased thereafter. Susceptibility to Leu-OMe of parasites studied in situ or isolated from infected macrophages increased with time of intracellular residence and by 7 days approached that of amastigotes isolated from mouse lesions. In contrast, parasites derived from either promastigotes or amastigotes were equally susceptible to another leishmanicidal compound, tryptophanamide (Trp-NH2). The results provide additional support for the involvement of megasomes and their cysteine proteinases in parasite killing by Leu-OMe, and highlight the slow pace of the intracellular differentiation of L. amazonensis promastigotes to amastigotes.

Nitric oxide (NO) production has been suggested to play a role as effector molecule in the control of the malarial infections. However, the roles of this molecule are debated. To assess whether blood-stage parasite killing is NO dependent, we investigated the course of blood-stage Plasmodium chabaudi chabaudi (Pcc) infections in inducible nitric oxide synthase (iNOS)-deficient mice. Parasitaemia, haematological alterations, and survival were not affected by the lack of iNOS. To exclude a role of NO produced by other NOS, controls included NO suppression by oral administration of aminoguanidine (AG), a NOS inhibitor. As in iNOS-deficient mice, no difference in the parasitaemia course, survival and haematological values was observed after AG treatment. Our results indicate that NO production is not required for protection against malaria in our murine experimental model. However, C57BL/6 mice treated with AG lost their resistance to Pcc infections, suggesting that the requirement for NO production for parasite killing in murine blood-stage malaria might be strain dependent.