The purpose of this study was to determine whether predisposition to Heligmosomoides polygyrus and Aspiculuris tetraptera (Nematoda) exists within a naturally infected population of mice. A breeding mouse population was housed in a spacious arena in which endemic infections of H. polygyrus and A. tetraptera were present. H. polygyrus were over-dispersed in the mouse population. Prevalence reached 100% by the age of 3 weeks; intensity of infection increased to a peak in the 10 to 15-week-old mice, and remained high throughout life. A group of 73 mice was treated with pyrantel pamoate, and the expelled worms were counted. Mice were returned to the arena. Daily egg production was monitored 4, 8, 12 and 14 weeks after treatment. Mice were then killed and numbers of H. polygyrus and A. tetraptera were counted. Significant positive correlations were detected between numbers of H. polygyrus at first treatment and at necropsy, indicating the existence of predisposition. Similar results were obtained for A. tetraptera. Correlations improved when data were analysed by age class of mice. Analyses based on egg-count data during reinfection did not support the hypothesis of predisposition, however. A. tetraptera and H. polygyrus burdens were significantly correlated only in 3 to 4-week-old mice at the time of the treatment.

The majority of research on Histomonas meleagridis was performed in the first half of the last century, especially those on morphological aspects. In the present study identical monoxenic settings for cultures of the same H. meleagridis clonal strain in its virulent low passage and attenuated high passage form enabled a comparative analysis of parasite characteristics. For the first time, it could be shown that long-term in vitro cultivation led to a severe shift in cell morphology, with the occurrence of a very distinct phenotype expressing a flagellated and highly amoebic cell morphology. Furthermore, the attenuated parasites showed better growth rates and a higher tenacity when confronted with adverse conditions. During these experiments up to 100% of the parasites, both virulent and attenuated, assumed a completely rounded morphology elucidated by electron microscopy. The findings indicate that such previously reported cyst-like stages are a defence strategy of H. meleagridis, independent of the passage level in vitro and pathogenicity in vivo. In conclusion, long-term in vitro passaging of H. meleagridis led not only to an attenuation of the parasite, as previously demonstrated, but also to a shift in the parasite's phenotype regarding morphology, growth behaviour and a higher level of tenacity.

This study compared the immunological and biochemical responses of co-grazed Suffolk and Texel lambs to a natural gastrointestinal nematode infection. Variables analysed included serum pepsinogen, total protein, albumin, haematological variables and nematode-specific serum immunoglobulin activity, at 11, 14 and 17 weeks of age. At 17 weeks, randomly selected lambs were necropsied to determine worm burdens, nematode-specific mucosal abomasal and intestinal immunoglobulin activity. Nematode burden, faecal egg count and pepsinogen concentrations were significantly higher in Suffolks relative to Texels, at all 3 time-points investigated. Suffolks displayed significantly higher erythrocyte, total leukocyte, lymphocyte and neutrophil counts, mean cell volume and packed cell volume, than Texels (P<0·01). However, breed differences in eosinophil counts were not significant. While serum nematode-specific antibody activity levels were significantly higher (P<0·001) in Texels for all isotypes measured, antibody activity levels at a mucosal level were equivalent in both breeds. Correlation analysis of mucosal antibody levels and nematode variables highlighted a more consistent pattern of events in Texels, with more mucosal antibodies negatively correlated with FEC and worm burden, in comparison to Suffolks. In particular, an important role for mucosal IgE is proposed. In Texels, a significant and negative correlation was identified between IgE and faecal egg counts and worm burden (FEC: −0·48, P<0·005). This was not observed in Suffolks. The evidence suggests that susceptibility in Suffolks may be mediated through poor IgE affinity/avidity and/or through deficiencies in related mechanisms such as mast cell production, recruitment or activation.

Parasites in the genus Onchocerca infect humans, ruminants, camels, horses, suids, and canids, with effects ranging from relatively benign to debilitating. In North America, Onchocerca cervipedis is the sole species known to infect cervids, while at least 5 Onchocerca species infect Eurasian cervids. In this study, we report the discovery of a cervid-parasitizing Onchocerca only distantly related to O. cervipedis. To reconstruct the phylogenetic history of the genus Onchocerca, we used newly acquired DNA sequence from O. cervipedis (from moose in Northwest Territories, Canada) and from the newly discovered species (from white-tailed deer in upstate New York), as well as previously published sequences. Ancestral host reconstructions suggest that host switches have been common throughout the evolutionary history of Onchocerca, and that bovid- and cervid-parasitizing species have been particularly important sources of descendant species. North America cervids might therefore serve as a source for Onchocerca invasions into new hosts. Given the high density of deer populations, the potential for zoonotic infections may also exist. Our discovery of a new Onchocerca species with relatively limited sampling suggests that the diversity of Onchocerca associated with cervids in North America may be greater than previously thought, and surveys utilizing molecules and morphology are necessary.

The protozoan parasite Leishmania belongs to the most ancient eukaryotic lineages and this is reflected in several distinctive biological features, such as eukaryotic polycistronic transcription and RNA trans-splicing. The disclosure of this organism's unusual characteristics leads to a better understanding of the origin and nature of fundamental biological processes in eukaryotes. Here we report another unusual phenomenon as we demonstrate that precursor ribosomal RNA can be extensively polyadenylated during post-transcriptional processing[dagger]. Furthermore, we demonstrate that the degree of precursor rRNA polyadenylation is variable in different strains and in the different life-stages of a strain.

A novel repetitive DNA sequence in the sheep parasitic nematode Trichostrongylus colubriformis was cloned and sequenced. A l·1 kb repetitive sequence (Tc15) which hybridized with DNA from T. colubriformis but not with DNA from two other parasitic nematodes, Haemonchus contortus and Ostertagia circumcincta, or sheep was further characterized. Southern blot analysis showed that the repeat hybridized to a range of fragments in restriction digested T. colubriformis DNA and existed in multiple copy number tandem arrays. However, to define clearly the repetitive monomeric unit further screening of phagemid libraries containing BamH I restriction fragments using a subclone of Tc15 as a probe was carried out. Restriction map and sequence data were compiled for 3 clones containing a 145 bp highly repetitive sequence (designated TcREP) which shared homology with the original pTc15 clone. TcREP hybridized to a tandemly repeating sequence monomer of 145 bp in T. colubriformis DNA which was cloned from various genetic environments in the T. colubriformis genome. TcREP homologous sequences were also found in the genomes of two other species of the same genus (Trichostrongylus axei and Trichostrongylus vitrinus) but not in a fourth species (Trichostrongylus rugatus).

The isolation of polysomes in bulk from bloodstream forms of Trypanosoma brucei is described. The polysomes are active in in vitro protein synthesis in the presence or absence of initiation inhibitors. Nascent variant surface antigen (VSA) has been detected on these polysomes using purified radio-iodinated antibody. EDTA-induced ribosomal sub-units and their large rRNA's are characterized. The 26S rRNA is nicked to produce 2 molecules which are both smaller than the 195 rRNA of the small sub-unit which is larger than that found in the majority of eukaryotic small sub-units.

The importance of host heterogeneity in generating aggregation was investigated using Heligmosomoides polygyrus (Nematoda) in laboratory mice. Parameters of infection were compared between inbred and outbred mice, between primary and challenge infection protocols, and between gavage and natural exposure protocols, to investigate the relative effects of innate resistance, acquired resistance and behaviour, respectively. Heterogeneity in acquired resistance was identified as the most consistent factor leading to variability and aggregation of H. polygyrus numbers in mice. This hypothesis was supported in two experiments where groups of mice did not develop resistance to challenge infection (use of certain inbred strains of mice and immunosuppression with corticosteroids in the drinking water) and where variability in worm numbers after the challenge infection was comparable with that after the primary infection. Heterogeneity in host behaviour, particularly in behaviours enhancing skin contact with larvae, also was associated with increased heterogeneity in worm burden, though not as consistently as heterogeneity in acquired resistance. Surprisingly, worm burdens were not more variable in outbred compared with inbred mice. Our data suggest that the relative contributions of innate resistance, acquired resistance and behaviour in generating variable worm burdens are likely to vary spatially and temporally.

The 50–30 kDa fraction isolated from the excretory/secretory products (E/S) of the nematode Nippostrongylus brasiliensis significantly decreased the amplitude of contraction of segments of uninfected rat intestine when injected into the lumen of the segments maintained in an organ bath. Dot blot analysis of the fraction suggested that it was similar in immuno-reactivity to porcine vasoactive intestinal polypeptide (VIP). When antiserum to porcine VIP was mixed with N. brasiliensis E/S and the mixtures were injected into the lumen of segments of rat intestine, the inhibitory effect of the E/S on amplitude of contraction decreased. When physiological concentrations of porcine VIP (12·9 pmol/ml) were injected into the lumen of segments of uninfected rat intestine the amplitude of contraction decreased significantly. Western blot analysis of the E/S, using antiserum to porcine VIP, recognized a 30 kDa protein in the E/S and also in whole worm homogenate suggesting that synthesis of the peptide occurs inside the nematode. Peptide histidine isoleucine (PHI)-like immuno-reactivity was detected in a 68 kDa fraction of the E/S and the homogenate but this fraction did not affect the amplitude of contractions of the intestine.

The main features of the life-history of Mermis nigrescens, so far as it is known, are briefly discussed. Some data have been collected on its distribution in the British Isles, and on the seasonal appearance of the egg-laying females. The insect hosts of the worm are discussed, and feeding experiments on various invertebrates are recorded, including the experimental infection of the common earwig (Forflctila auricularia). This insect, which has also been found naturally infested, is regarded as an important host for the species, more especially where grasshoppers are absent. Observations by other workers on the influence of the number of larvae per host on the sex of the developing worms, and on the survival of the host, have been confirmed. Two new species, closely related to M. nigrescens, are described: M. kenyensis and M. tahitiensis, from Africa and Tahiti respectively.

This survey records the intestinal protozoa found in 611 hospital cases in Sweden, 1244 mental asylum cases in Sweden, and 159 medical out-patients in Finland. Only one examination was made of each case.

In each of these three groups the following protozoa were found: Entamoeba histolytica, E. coli, Endolimax nana, Iodamoeba bütschlii, Giardia intestinalis, and Chilomastix mesnili. In hospital and asylum cases in Sweden Dientamoeba fragilis was encountered, Trichomonas hominis and a small flagellate were found in the asylum group, and in this group as well as in the series in Finland, Balantidium coli was met with. In one case cysts of this protozoon were found.

In a group of 46 cases, formed stools as well as loose stools obtained after administration of a purgative were examined. The loose samples revealed the presence of Trichomonas hominis, Balantidium coli, and a small flagellate, none of these having been found in the formed specimens. The percentage of Dientamoeba fragilis rose from 8·7 per cent, in the formed stools to 23·9 per cent. in the loose stools. All the other species were more abundantly present in the loose than in the formed samples.

In Sweden, mental asylum cases show a much higher incidence of infections than do the hospital cases.

Intestinal protozoa seem to be more common in Finland than in Sweden.

Among hospital cases in Sweden the residents of Stockholm show a lower incidence of infections than do the people living in rural districts.

At admission, asylum cases are not infected to a higher degree than are the general hospital cases. The rise in incidence of infection is directly proportional to the length of time spent in the institutions up to ten years, after which time no further increase occurs. The male patients show throughout considerably higher percentages of infections than the female patients. Chilomastix mesnili shows a very high incidence in the asylums, whereas the percentage of Giardia intestinalis remains practically the same throughout the time of confinement in the institution.

Tick-borne diseases are a major impediment to improved productivity of livestock in sub-Saharan Africa. Improved control of these diseases would be assisted by detailed epidemiological data. Here we used longitudinal, serological data to determine the patterns of exposure to Theileria parva, Theileria mutans, Babesia bigemina and Anaplasma marginale from 548 indigenous calves in western Kenya. The percentage of calves seropositive for the first three parasites declined from initial high levels due to maternal antibody until week 16, after which the percentage increased until the end of the study. In contrast, the percentage of calves seropositive for T. mutans increased from week 6 and reached a maximal level at week 16. Overall 423 (77%) calves seroconverted to T. parva, 451 (82%) to T. mutans, 195 (36%) to B. bigemina and 275 (50%) to A. marginale. Theileria parva antibody levels were sustained following infection, in contrast to those of the other three haemoparasites. Three times as many calves seroconverted to T. mutans before seroconverting to T. parva. No T. parva antibody response was detected in 25 calves that died of T. parva infection, suggesting that most deaths due to T. parva are the result of acute disease from primary exposure.

The free-living amoeba Naegleria fowleri is the aetiological agent of primary amoebic meningoencephalitis (PAM), a disease leading to death in the vast majority of cases. In patients suffering from PAM, and in corresponding animal models, the brain undergoes a massive inflammatory response, followed by haemorrhage and severe tissue necrosis. Both, in vivo and in vitro models are currently being used to study PAM infection. However, animal models may pose ethical issues, are dependent upon availability of specific infrastructural facilities, and are time-consuming and costly. Conversely, cell cultures lack the complex organ-specific morphology found in vivo, and thus, findings obtained in vitro do not necessarily reflect the situation in vivo. The present study reports infection of organotypic slice cultures from rat brain with N. fowleri and compares the findings in this culture system with in vivo infection in a rat model of PAM, that proved complementary to that of mice. We found that brain morphology, as present in vivo, is well retained in organotypic slice cultures, and that infection time-course including tissue damage parallels the observations in vivo in the rat. Therefore, organotypic slice cultures from rat brain offer a new in vitro approach to study N. fowleri infection in the context of PAM.

Interpretation of anthelmintic activity using in vitro screens has, until now, relied on the detection of drug-induced effects on nematode development, viability and motility. A novel biochemical parameter dependent upon the spectrophotometric assay of acetyicholinesterase (AChE), an enzyme secreted in large quantities by certain trichostrongylid nematodes, has been developed to replace these often subjective indices of activity. Using Nippostrongylus brasiliensis, a worm frequently employed for primary screening, the secretion of this enzyme in the presence or absence of a large number of drugs in vitro was determined. During a 4-day incubation period in a complex undefined medium without serum, AChE was secreted by normal 4th larval and immature adult stages of the worm in a linear fashion. All modern broad-spectrum veterinary anthelmintics, regardless of their mode of action, dramatically reduced the amount of enzyme secreted. Correlation between the biochemical and observa tional parameters was excellent and the selectivity of the assay when based solely on enzyme secretion was not lost. Other advantages were that the time required for the activity of certain slow-acting compounds to be detected was reduced from 7 to 4 days and that close microscopical examination of the worms was not necessary.

In August, 1933, I received from Colonel A. E. Hamerton, C.M.G., D.S.O., R.A.M.C. (ret.), Pathologist to the Zoological Society of London, samples of a stool obtained from an Indian rhinoceros (Rhinoceros unicornis) on exhibition in the Society's Gardens. The animal in question was at that time suffering from severe diarrhoea and wasting, and its faeces—preserved in 5 per cent formalin—contained numerous undetermined ciliates. On examination of the material I found that two kinds of ciliates were present, one a typical Entodinium (Entodiniomorpha Ophryoscolecidae), and the other an entodiniomorphous form obviously belonging to the Cycloposthiidae, but differing from all the members of this family hitherto described.

Biochemical studies on the non-specific phosphomonoesterases of Fasciola hepatica have shown the presence of acid phosphomonoesterase active at pH 4·6 and two forms of alkaline phosphomonoesterases active at pH 7·6 and pH 9·6 respectively. Histochemical studies have located acid phosphomonoesterase in the walls of the intestinal caeca and to a lesser extent in the tegument. Alkaline phosphomonoesterase was found to occur mainly in the excretory ducts and to a lesser degree in the uterine wall. Glycogen was mainly concentrated in the yolk glands, parenchyma, mature eggs and the non-muscular regions of both oral and ventral suckers.

Dr A. J. Probert takes pleasure in recording the support of the British Council and the Indian University Grants Commission to enable him to study in India.

Phosphorylcholine (PC) is a common constituent of proteins secreted by filarial nematodes. As this substance has been shown to interfere with immune responses, we are interested in designing strategies for blocking its attachment. Towards this end, we are investigating the mechanism of incorporation of PC into filarial molecules and in the present manuscript we describe experiments relating to elucidating the source of PC for attachment. Synthesis of phosphatidylcholine in eukaryotic organisms can occur by a mechanism involving the transfer of PC from CDP-choline to diacylglycerol (the Kennedy pathway). By (i) measuring transfer of radio-isotope labelled PC from CDP-choline to parasite molecules and (ii) employing inhibitors of CDP-choline synthesis, we have investigated whether CDP-choline can act as a source of PC for transfer to ES–62, a major secreted glycoprotein of the rodent filarial nematode Acanthocheilonema viteae. Although we can find no evidence of this, we show that attachment of PC is blocked by hemicholinium-3, an inhibitor of choline kinase, the first enzyme in the Kennedy pathway. Thus, at least the first step in this pathway – phosphorylation of choline, would appear to be necessary for attachment of PC to ES-62.

Approximately 90% of Hymenolepis citelli cysticercoids given to 6-week-old male CFLP mice by stomach tube became established. Equally high recovery rates were obtained from administering 1, 3 and 6 cysticercoids.

In 1-worm infections worms increase in weight until about day 25–28 post infection. After a few days at maximum weight (mean weights of worms 24–42 mg) there is a small, 10–25%, decrease in weight, after which there is little change in weight up to day 90 (as long as studied).

One-worm infections survived without loss until day 30, after which a slow loss occurred, but only in two experiments, both with older mice, did loss exceed 50% by day 80. In 3-worm infections worms were rejected between days 17 and 30, but loss varied from 50 to 80% during this period in replicate experiments. With 6-worm infections rejection occurred over a shorter period (days 17–22), was more uniform between experiments and was more complete, over 75% of worms being lost. In both 3- and 6-worm infections a residual population, usually of only a single worm, persisted in 20–50% of the mice until the end of the experiments (day 63–78).

Cortisone prevented loss of worms from both 3- and 6-worm infections; worms continued to grow until day 25 ± 2 (as in 1-worm infections), by which time they were considerably larger than (the surviving) worms in mice not receiving cortisone. The biomass (worm burden per mouse) remained constant from day 25 to 55 in mice receiving cortisone.

The results are discussed with particular reference to: H. diminuta and the evidence that mice do mount an immunological response against tapeworms in the intestine; the existence of an antigenic threshold in mice; the apparent existence of a similar rejection pattern in a natural population of H. citelli in Peromyscus maniculatus, and hence the importance of immunity as a factor preventing gradual increase in number of tapeworms in the intestine during the life of a host.

1. A simple apparatus for feeding all stages of Rhodnius prolixus through a rubber membrane is described.

2. Observations have been made on the behaviour of Rhodnius during feeding, and on the effect of different diets on the insect.

3. Rhodnius has been shown to feed and grow successfully on freshly drawn rat and horse blood, and on whipped ox blood. Horse serum was readily taken and showed no effect on the development of the bugs until after the third stage, when they either failed to moult or emerged deformed.

Ringer's solution, aqueous solutions of ‘Marmite’ and cow's milk provided good feeds, though caused mortality after 24 hr. Stored oxalated blood killed bugs 21 days after feeding. No feeding took place when diets of water, glycine and ascorbic acid were offered.

In CFLP male tapeworm-free mice, from 2 to 7 weeks old at infection, at least 80% of single Hymenolepis diminuta establish and grow but then are rejected; day of rejection defined as the first day when ≦ 50% of the worms were recovered. Young mice, 2 to 4 weeks old, usually reject their worms during days 16–20 while older mice, 5 to 7 weeks old, reject them during days 12–14. Biomass (total dry weight of all worms recovered on a given day from a group of mice) varied markedly with host age and was consistently greatest in 4-week-old mice. The position of the worm in the intestine did not vary with host age. The quality of mice (categorized by the Medical Research Council Laboratory Animals Centre) did not appear to affect the course of a primary, single H. diminuta infection although, undoubtedly, the mice had varied immunological histories. Variations in time of rejection and biomass of worms recovered are accounted for by both immunological and physiological mechanisms.