During the last few years I have successfully used a new method for investigating intestinal amoebae in cultures, and in the hope that it may also prove serviceable to other workers I now propose to describe it. At the same time I take the opportunity of noting two new staining methods which I have used especially in conjunction with this technique, but which are of general utility in protozoology and cytology.

The inoculative mechanism whereby cystophorous cercariae infect the copepod 2nd intermediate host is described for the first time in Cercaria vaullegeardi. Experimental infections of the harpacticoid copepod Tigriopus brevicornis are recorded and the infection process is related to the ultrastructure of the cercaria and to the feeding mechanics of harpacticoids. The cystophorous tail of C. vaullegeardi is shown to be a device whose shape and construction ensure that the cercarial body is neither damaged by copepod mouthparts nor swallowed, but reaches the host haemocoel during the initial stages of feeding. The cystophorous tail consists essentially of a caudal cyst, into which the cercarial body retracts at encystment, and various appendages including a delivery tube. The infection mechanism is triggered when the copepod mandibles bite the narrow posterior caudal cyst beak, when the delivery tube everts into the mouth and penetrates the dorsal mid-gut wall. The cercarial body, lubricated by tegumental secretions, passes simultaneously through the delivery tube and is inoculated into the host haemocoel.

Fifty-six sheep, worm-free birth, were each given a sigle infection of 50 000 Haemonchus contortus larvae at varying at varying times over a 2 year period. They were killed from 13 to 89 days infection and the lengths of both male and female parasites measured. Using a computer, growth curves for each sex were constructed and the relative lengths of the worms in each infection were calculated by dividing their measured lengths by the lenghts predicted by the appropriate curve. Since there was no significant difference between the relation length of male and female worms in an infection, the mean value was used in further analyses. Differences in sex of host and duration of infection had no significant effect on the relative length of parasites. There was a close relation between relative length and the time of year of infection. The relation was cyclical and closely followed a sine curve with a maximum at day 90 and a minimum at day 275 of the year. Arrested development at the 4th larval stage occurred at the time of year risen again. It is suggested that this cyclic change in growth pattern and arrested development is controlled by the seasonal variation in concentration of a substances present in the host’s blood. Parasite relative length was also related to sheep age, but the relationship observed was largely an artifact of the close birth dates of many of the sheep.

The author has examined 1437 crops of hair, removed from adult or adolescent males on admission to jail, at Cannanore, South India. There is a high positive correlation between weight of hair and rate of infestation with head-lice, men with less than 10 g. of hair being 14·6% infested, those with 10–19·9 g. 39·9%, and those with over 20 g. 56–59%.

There appears to be a negative correlation with age, but this seems to be due to the older men having less hair: if one standardizes hair weight there is no tendency for older men to be less infested than younger. In a similar way, the large differences in rate of infestation between different religious groups appear to be due to a great extent (but not entirely) to differences in hair weight.

No evidence was found that rate of infestation is different at different times of year. The rates in the rainy and dry seasons scarcely differ, in spite of the intensity of the rain, and of the fact that the rainless period lasts for six months. It is possible that there is a long-period, secular change in rate of infestation.

The ability of the cercariae of Schistosoma mansoni to penetrate the tails of mice was shown to remain constant throughout their lives. However, their capacity to establish themselves and then reach maturity decreased as they aged. The abdominal route of penetration produced consistently higher maturation rates than the tail route. Significantly different maturation rates were obtained by modifying the standard tail infection technique. Evidence is presented that age-related mortality of schisto-somula occurs within 24 h of penetration and may be associated with the exhaustion of energy reserves during the penetration of the stratum corneum. The relationship of this age-related mortality to ‘mass mortality’ is discussed.

1. The life cycle of Cotylurus brevis Dubois and Rausch, from the cercaria to the adult, has been investigated for the first time by using laboratory-bred primary, secondary and definitive hosts. The holometabolic metamorphosis with the formation of a tetracotyle stage in a second intermediate host has been described in detail.

2. The cercaria of C. brevis obtained from Lymnaea stagnalis in Edgbaston Pool has been found to be identical with Cercaria helvetica XXXIV Dubois from Lake Neuchâtel. The total number of flame cells in the cercaria is twenty, as opposed to the fourteen in the cercaria of Cotylurus cornutus Rudolphi (= ‘Strigea tarda’ described by Mathias (1925), Harper (1929, 1931) and Wesenberg-Lund (1934)).

3. In nature the second intermediate host of Cotylurus brevis is Lymnaea stagnalis. Under experimental conditions L. pereger and L. auricularia were also found to act as second intermediate hosts, but neither Planorbis corneus, P. carinatus nor various leeches could act as second intermediate hosts.

4. The tetracotyle stage of Cotylurus brevis is morphologically indistinguishable from the corresponding stage of other species of Cotylurus.

This study aimed to evaluate the performance of the point-of-care circulating cathodic antigen (POC-CCA) test in a highly endemic area in Brazil, comparing it to the Kato-Katz (KK) technique for sensitivity, specificity and the intensity of the reaction of the test in relation to the parasitic load. The community in Sergipe, Brazil, participated in the study, providing three stool samples, one of urine (POC-CCA) and fingers tick blood sample was tested by enzyme-linked immunosorbent assay (ELISA). Sensitivity, specificity, positive predictive value, negative predictive value, accuracy, kappa coefficient and Spearman's correlation were calculated for the POC-CCA test using the KK as the reference. The prevalence of schistosomiasis by KK testing was 48.82%; POC-CCA (t+) 66.14%; POC-CCA (t−) 45.24%. ELISA results showed 100% agreement in individuals with high and moderate eggs per gram (EPG). POC-CCA presented good diagnostic performance in individuals with medium and high EPG, but there were a high number of false negatives in individuals with low intensity infections. As observed, POC-CCA-filter test improves accuracy and sensitivity compared to a conventional test.

Amastigotes from Leishmania braziliensis and L. mexicana were isolated from cutaneous lesions in infected animals using the plant lectin Concanavalin A as a specific agglutination agent. Amastigotes were collected in preparations of up to 95% purity as determined by cell count. The parasites obtained by this method showed no apparent loss of viability as measured by growth rates and DNA replication, or pathogenicity as measured by routine passages in hamsters or mice.

A cDNA encoding a Na,K-ATPase alpha subunit homologue, designated SNaK1, was isolated from an adult cDNA library of Schistosoma mansoni. The 3.8 kb DNA contained a 3021 bp open reading frame potentially encoding a 1007 amino acid protein that had an Mr of 111817 and a pI of 5.48. Homology searches for SNaK1 revealed approximately 70% sequence identity with a variety of Na,K-ATPases from evolutionarily diverse organisms. SNaK1 is predicted to contain 10 transmembrane regions typical of this protein family as well as other conserved domains, such as the phosphorylation site and ATP binding domain. Antibodies raised against an amino terminal peptide detected the protein in membrane preparations of eggs, cercariae and adult males and females, suggesting a general role for SNaK1. The mobility of the protein differed in various life-stages suggestive of post-transcriptional or post-translational modification. Immunolocalization of SNaK1 in sections of adult worms using epifluorescence and electron microscopy, revealed antibody labelling in the subtegumental and peripheral layers. Strong staining was discernible in the peripheral muscle band indicating that SNaK1 plays a central role in muscle contraction in adult parasites and may be the primary target of ouabain action. Staining was also detected in the secretory bodies in sections of ducts in this region and over the RER of the presumed gastrodermis. Immunogold labelling was also localized over neuronal vesicles in axons associated with the peripheral muscle layer.

The antigenic relationships of 7 stocks and 7 clones of Trypanosoma vivax from East and West Africa were compared by immune lysis. Sera from goats infected with different stocks and clones of T. vivax, collected on days 40 and 80 after infection, were used in the immune lysis test with homologous and heterologous stocks and clones of trypanosomes. Sera from infected cattle were included to compare stocks and clones from Kenya. The parasites that were used as antigen in the immune lysis tests were collected from infected mice when variable antigen type (VAT) homogeneous populations were used, from goats for infection with stocks and clones from Nigeria, The Gambia and Uganda, and from cattle for Kenyan stocks. Reciprocal cross-reactivity between sera and parasites was found between all the stocks and clones from Nigeria and The Gambia with the exception of one clone from Nigeria that was not recognized by antisera to a clone from The Gambia. There was also cross-reactivity between a stock and clone from Uganda and stocks and clones from Nigeria and The Gambia. Sera from goats infected with stocks and clones from Nigeria, The Gambia and Uganda recognized parasite populations that were homogeneous for one VAT (ILDat 1.2) of the rodent infective stock from Nigeria. Some antisera to West African stocks recognized another stable variant from a Ugandan stock adapted to rodents (ILDat 2.1), indicating that these VATs were expressed in the repertoires of the heterologous stocks. There was no cross-reaction between stocks from Nigeria, The Gambia or Uganda with Kenyan stocks. A stock from Galana (Kenya) and Bamburi (Kenya) showed reciprocal cross-reactivity. Two other Kenyan stocks, from Kilifi and Likoni, also showed cross-reactivity by immune lysis but showed no antigenic relationship with the other Kenyan stocks.

Parasite prevalence is an important variable in many evolutionary and ecological studies. In birds, haemosporidian blood parasites have been in focus of many comparative analyses. Because low prevalence is difficult to estimate precisely and that studies finding low prevalence are more likely to remain unpublished, our knowledge of parasite prevalence is biased towards highly infected taxa. Species with naturally low levels of infection are nonetheless interesting as they may provide models for studying the evolution of pathogen resistance. In the present study we show that the prevalence of Haemoproteus parasites is markedly lower in several taxa within the widely distributed chiffchaff species-complex compared to other species within the genus Phylloscopus. Since chiffchaffs, P. collybita, commonly coexists in the same habitat as congeners frequently infected with Haemoproteus parasites, immediate ecological variables like abundance of vectors can hardly explain this difference. Some of the parasites infecting coexisting congeners are broad host generalists leaving it enigmatic why chiffchaffs are almost free of Haemoproteus infections. We propose that detailed infection experiments are needed to illuminate whether chiffchaffs possess a genetic immunity against Haemoproteus parasites or if other more subtle ecological processes, like anti-vector behaviour, play a role in its generally low level of infestation.

Rigorous proofs applicable to the routes of migration of Strongyloides ratti and Nippostrongylus brasiliensis skin-penetrating juveniles inside the rat are extended. By applying the inequality principle (Tindall & Wilson, 1988) it was confirmed with a probability of error of I in 1010 that N. brasiliensis larvae applied to the skin passed through the lungs on their way to the intestine. Taking the analysis further, migrating larvae of S. ratti or N. brasiliensis were extracted from the nose or lungs, respectively, of donor rats and transferred to recipients by stomach tube to assay their ability to colonize the intestine. Results showed that (a) changes undergone by each parasite in its proven, specific transit site were essential before larvae could establish in the intestines of recipients, (b) these changes were not completed until larvae had been in the nose or lung for a significant period.

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

Third and artificially hatched second-stage larvae of A. suum were exposed to the action of saline and normal and homologous immune pig serum. Precipitates developed at the mouth, excretory pore, anus and around the cuticle of third-stage larvae when they were placed in immune pig serum, but not in saline or normal serum. Precipitate was most evident at the excretory pore and was often the first precipitate to form. It is suggested that the excretory products may play an important role in stimulating the production of antibody in the host. A relationship was noted between the antibody titre of the serum and the amount of precipitate, the life span of the larvae, their activity, and the rate at which precipitates formed. It is concluded that the titre of the serum was in some degree a measure of the ability of the host to resist reinfection.

Circumlarval precipitates did not form when second-stage larvae were placed in samples of the same immune serum. It is pointed out that this may be due to the lack of sufficient antigenic material available to react with antibody in the antisera. It is also suggested that an absence of sufficient larval antigen may also partly account for the small degree of resistance exhibited by the resistant host within the first 2 or 3 days of reinfection.

The work, which is abstracted from a Ph.D. thesis, was carried out in 1957 under the tenure of an Animal Health Trust Wellcome Fellowship. I am grateful to Dr Soulsby, under whose guidance this work was carried out.

Sporozoites of 3 species of Eimeria were introduced into the caecum of young chickens. E. praecox and E. maxima failed to develop in this site, but light infections of E. acervulina were detected. Infection of the small intestine with all 3 species occurred when sporozoites were introduced via the caecum.

Infections were produced when mucosal scrapings of small intestine from birds, inoculated via the caecum 1–4 h previously, were inoculated orally to susceptible chickens. Experiments with 51Cr-labelled sporozoites of E. praecox introduced in the caecum, confirmed that small numbers of sporozoites are capable of migrating from the lower to the upper intestine. Sporozoites were not transferred with liver tissue from birds given sporozoites via the caecum but were transferred with the liver of chickens given sporozoites intraperitoneally.

The unlabelled antibody method was used in the ultrastructural localization of two hydatid fluid antigens, antigen 5 and antigen B, in brood capsules and protoscoleces of Echinococcus granulosus and E. multilocularis. Antigen 5 was found in the parenchyma cells of the protoscolex and brood capsule wall and to a lesser extent in the walls of the flame cells and collecting ducts of the excretory system and in the surrounding interstitial material. It is suggested that, while some excretion of this antigen may occur from the protoscolex, it could also be liberated into the cystic cavity by degeneration of protoscoleces and parenchymal cells of the brood capsule wall. Antigen B was found mainly in the distal cytoplasm and perinuclear cytoplasm of the tegument anterior to the suckers. It is apparently secreted to the outside and was present in the brood capsule contents; it adheres to the anterior surface and the posterior periodic acid–Schiff (PAS)-positive glycocalyx of the protoscolex and to the inner surface of the brood capsule wall. The protoscolex tegument posterior to the suckers was negative. The parenchyma cells of the protoscolex and brood capsule wall were also positive although the intensity of the reaction product was variable.

125I-labelled, isolated variable surface glycoproteins (VSGs) of Trypanosoma b. brucei bind both homologous and heterologous anti-VSG sera and binding to heterologous antisera may be blocked by other unlabelled VSGs (Barbet & McGuire, 1978). This paper presents results which suggest that oligosaccharide residues have importance in the antigenic structure of VSG cross-reacting determinants. The ability of VSG to bind heterologous anti-VSG sera was destroyed by periodate oxidation but not by extensive proteolysis. A VSG glycopeptide fragment was isolated from two different VSGs, which blocked by 100 % the binding of VSG to heterologous anti-VSG sera and therefore contained the cross-reacting determinants. The native glycopeptide fragment was resistant to digestion with trypsin, pronase or leucine aminopeptidase and prolidase. We also show that a VSG synthesized in the reticulocyte lysate cell-free system was not immunoprecipitated by heterologous anti-VSG sera in contrast to the same VSG labelled by metabolic incorporation of [35S]methionine in vivo.

Raillietiella gigliolii is a cephalobaenid pentastomid which inhabits the lungs of the South American worm-lizard Amphisbaena alba. The host is a facultative inquiline of nests of the leaf-cutting ant Atta cephalotes where it feeds occasionally (and possibly by accident) on ants but more often on beetles and their larvae which are themselves inquilines of ant nests. Ants store exhausted leaf-substrate in special underground chambers which serve as refuse dumps and it is here that larvae of the three-horned rhinoceros beetle Coetosis biloba feed: these larvae are also known to be prey items of A. alba. From observations of captive colonies of Atta, we have demonstrated that pentastomid-egg contaminated faeces of A. alba, introduced into the colony, are rapidly cut up and thrown onto the refuse dump, where, under natural circumstances they will be eaten by Coelosis. These larvae have an unusual and highly specialized gut physiology and parasite eggs will develop to an infective stage within the haemocoel in 70–96 days. Cockroaches are refractory to infection. Ants are the vital link in transmission since they literally deliver eggs to the Coelosis larvae. The strong trophic links which exist between the various components of the life-cycle offset a low fecundity of 100 eggs/female parasite/day but nonetheless maintain a high prevalence (86%) of infection.

The object of these experiments was to study the pathogenesis and kinetics of Theileria annulata infection in the efferent lymph of the draining lymph nodes of calves. Efferent lymphatics of calves were cannulated prior to infection with T. annulata sporozoite or an allogeneic schizont cell line. Potentially lethal sporozoite challenge induced cell shut-down from days 4–6 and then a massive increase in output of blasting cells (both infected and non-infected) in the efferent lymph. The rate of lymph flow and total cell output increased to 5 to 10-fold from day 6 onwards. Sporozoites were never isolated from the efferent lymph. However, large numbers of parasite-infected cells were seen in efferent lymph from the sixth day of infection. The animals inoculated with an allogeneic T. annulata-infected cell line exhibited only a small increase in flow rate and cell output. Parasite-infected cells of recipient origin were seen in efferent lymph from day 11 onwards. However, cells of donor origin were never isolated either from efferent lymph or peripheral blood. Thus the parasite transferred from the inoculated donor cell line to the cells of the recipient before schizonts appeared in efferent lymph.

Adult Haemonchus contortus worms simultaneously excrete and fix CO2. Their initial content of CO2 was measured as 4·55 μmoles/100mg wet weight and their excretion rate in air as 1 μmole/100 mg wet weight/h for at least 4 h. When the worms were incubated either aerobically or anaerobically with 14CO2 most of the metabolized radioactivity was associated with propan-1-ol and propionate but small amounts were found in succinate and lactate. No radioactivity was associated with ethanol or acetate, two major catabolites of glucose. Stepwise degradation of the metabolized radioactive propanol and propionate showed that all the radioactivity in both compounds was associated with carbon atom no. 1. These results show that H. contortus has much in common with the anaerobic energy metabolism of Ascaris lumbricoides but they are not inconsistent with the utilization of the tricarboxylic acid cycle by the worm. H. contortus worms were found to metabolize their excretory products. When they were incubated with either [2,3-14C]succinate or [2-14C]acetate, 14CO2 was excreted under aerobic but not under anaerobic conditions. These results are consistent with a pathway similar to that used by Ascaris operating alone under anaerobic conditions and together with the tricarboxylic acid cycle under aerobic conditions.