The SICA[ − ] or non-agglutinable phenotype of Plasmodium knowlesi schizont-infected erythrocytes has been defined serologically but not biochemically. Similarly, non-cloned SICA[ + ] or agglutinable parasites have been shown serologically to express SICA or variant antigen(s) but the number and nature of such antigens have not been defined. Here we describe the immunochemical analysis of surface antigen expression on [125I]lactoperoxidase-labelled erythrocytes infected either with a SICA[ − ] elone or with non-cloned SICA[ + ] parasites using the methods developed for identification of variant antigens with cloned SICA[ + ] parasites. No 125I-labelled antigens in the size range Mr 190000–225000 were specifically immunoprecipitated from erythrocytes infected with the SICA[ − ] elone, even using homologous antisera produced by multiple infections or immunizations. Further, no125I-labelled proteins of this size were seen in detergent extracts of the SICA[ −] parasites that were not also seen with uninfected cells. We conclude that the SICA[ − ] phenotype reflects the absence of a variant antigen at the erythrocyte surface, as predicted by the serological assays. In contrast, with the non-cloned SICA[ + ] parasites, a complex group of proteins, Mr 195000–225000, was identified by [125I]lactoperoxidase labelling of intact infected erythrocytes. These proteins are SICA antigens since they not only share the characteristic detergent solubility properties and size range of SICA antigens identified previously with SICA[ + ] clones, but they were only immunoprecipitated by antisera which reacted specifically with the surface of infected erythrocytes. Agglutinating sera immunoprecipitated several of these 125I-labelled antigens. Sera specific for clones derived from this non-cloned SICA[ + ] population failed to agglutinate, but did react by indirect immunofluorescence with 10–16% of infected cells. These sera specifically immunoprecipitated single, quantitatively minor 125I-labelled antigens in this size range. The results suggest that a population of non-cloned SICA[+] parasites contains at least 10 different variant-antigen phenotypes. Indirect immunofluorescence was also performed against a non-cloned SICA[ + ] population derived by antigenic variation of a SICA[ + ] clone in vivo. The variant population contained at least 3 antigenically distinct SICA phenotypes, indicating that antigenic variation of clones may produce populations as antigenically heterogenous as antigenic variation of uncloned lines. It is therefore likely that natural malaria isolates contain a large number of different variant antigens.

The brush border of the intestinal cells of the infective larva of Trichinella spiralis is shown to consist of microvilli. It is suggested that large vesicular complexes in association with Golgi complexes may be responsible for the production of the mucopolysaccharide or mucoprotein filling the lumen of the intestine. Indirect evidence of a latent intranuclear virus infection is presented. The cuticle lining the hind gut, although continuous with the external cuticle, is not similar in structure.

I would like to thank Dr D. L. Lee for instruction in all aspects of this work, Professor Boyd for the use of the Anatomy Department electron microscope and the Agricultural Research Council for financial support.

The infectivity of wild and laboratory strains of Heligmosomoides polygyrus (Nematospiroides dubius) in laboratory mice and in three species of wild British rodent was compared. Wild strains, of the subspecies H. p. polygyrus, were isolated from wild caught Apodemus sylvaticus. Only very low-level infections of the wild strains became established in laboratory mice. Similar worm burdens of the laboratory strain became established in laboratory mice and A. sylvaticus, although infections in A. sylvaticus were more short lived. Cortisone treatment of hosts increased the establishment and survival of the heterologous worm strain to that of the homologous strain. In contrast, neither strain of parasite established in Clethrionomys glareolus or Microtus agrestis, and cortisone treatment of C. glareolus did not increase establishment. Infection of laboratory mice with the wild-strain parasite induced significant immunity to a challenge infection with the laboratory strain.

A new subgenus and species of avian haemocytozoon Fallisia (Plasmodioides) neotropicalis is described. The principal characteristics are the main host cells, thrombocytes and mononuclear leucocytes, where trophozoites, schizonts and gametocytes are found. Occasionally, granulocytes and very rarely reticulocytes are also parasitized. Phanerozoites very similar to those of Plasmodium of birds are also present. The host is the domestic pigeon, Columbalivia, an imported species but similar parasites have been identified, always mixed with species of Plasmodium, in several indigenous species of Ciconiiformes, which seem to be the natural hosts. This is the first report in birds of a representative of the genus Fallisia, parasites of neotropical lizards.

For the tick Hyalomma anatolicum anatolicum, at constant temperature and humidity, the pattern of oviposition is constant, and consists of a peak period, usually after 2–3 days, followed by a gradual decline.

Oviposition proceeds more rapidly in constant darkness than in continuous light.

With increased temperature the oviposition period is decreased, but with increased humidity the period is extended.

The largest eggs are laid from 0 to 48 h after the peak of egg production, and no correlation has been observed between female size and egg size.

The number of eggs produced by a tick is directly proportional to its engorged weight, and since the engorged female weight is a direct reflexion of its unfed weight, the number of eggs laid is directly dependent on the size of the unfed female.

Guinea-pigs show partial immune response to adults of H. anatolicum anatolicum when the ticks are fed on them repeatedly. This minimizes the amount of nutrients imbibed and accordingly egg-laying potential is not realized.

The material on which this study was made was presented to us by Dr R. P. Chaudhuri, and we gratefully acknowledge his kindness.

The locomotion of two species of cercariae has been studied by cinematography. The ability of the tail to generate bending waves providing the force to drive the cercaria forward has been demontrated. The waveform of the tail and its relation to the pattern of movement has been described and evidence is presented that the tail is capable of propagating complicated swimming movements in the absence of the body. The pattern of propulsion is related to the functional organisation of the tail musculature of the cercaria.

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.

Isolates of Trypanosoma cruzi from human patients, domestic and sylvatic animals and vector insects were obtained in different areas of Argentina. Electrophoretic patterns of enzymes from extracts of 95 isolates were analysed. On the basis of zymograms providing information on 10 loci, 12 zymodemes are described according to their genotypes. Data presented show fixed heterozygosity, absence of segregation of genotypes, significant departures from Hardy–Weinberg equilibrium, and over-represented genotypes. This evidence supports the hypothesis that sexual reproduction is very restricted or absent in this parasite. The proportion of polymorphic loci is 80%. The expected mean heterozygosity per locus (He) is 0·43, while the observed value (Ho) is 0·24. Differences between these values may be explained by accepting a basically clonal structure for T. cruzi. The data matrix of 12 zymodemes using 28 characters was analysed using a Wagner parsimony algorithm. Two equally most parsimonious unrooted trees were generated; both have 39 steps. The results show clusters clearly separated according to the geographical origin of the stocks. There are some indications of some correlations between genetic composition of the parasite and the clinical picture of the infection in human patients.

Entomopathogenic nematode infective juveniles are likely to encounter both uninfected and infected insects and host quality depends on the stage of the infection. We hypothesized that nematode response to infected hosts will change over the course of an infection. Here, we tested this hypothesis by focusing on the influence of host infection status on long-range attraction to host volatile cues. The attraction response of 3 nematode species (Steinernema carpocapsae, S. glaseri and S. riobrave) with different foraging strategies to infected and uninfected insects (Galleria mellonella and Tenebrio molitor) was tested at 24 h intervals from start of infection to emergence of infective juveniles from depleted host. As expected, based on their foraging strategies, S. carpocapsae was not very responsive to hosts, S. glaseri was highly responsive and S. riobrave was intermediate. Generally, the level of attraction did not change with time after infection and was similar between infected and uninfected hosts. An exception was S. glaseri infected T. molitor, which tended to be less attractive to S. glaseri than uninfected hosts. These results suggest that any influence of host infection status on infection behaviour is occurring at subsequent steps in the host-infection process than host attraction, or involves non-volatile cues.

The aim of the study was to measure the impact of Schistosoma japonicum and Trichuris suis infections in young growing pigs fed low- or high-protein diets. Thirty-two pigs, 6–10 weeks old, were randomly allocated to 2 groups receiving either a high- or a low-protein diet. After 11 weeks half of the pigs from each group were infected with 1500 S. japonicum cercariae and 4000 T. suis eggs. The weight of the pigs was measured throughout the study, and blood and faecal samples were collected every second week from the time of infection. At the time of infection the low-protein pigs had significantly lower mean body weights, haemoglobin and albumin levels compared with the high-protein pigs, and this pattern continued throughout the study. The serum albumin concentration was further significantly reduced in the infected low-protein pigs compared to the non-infected low-protein pigs. Significantly more S. japonicum worms as well as faecal and tissue eggs were found in the low-protein pigs compared with the high-protein pigs. No differences between the 2 diet groups were observed in T. suis establishment rates or faecal egg excretion. We conclude that this low-protein diet increased the establishment rates of S. japonicum, favoured larger deposits of S. japonicum eggs in the liver and faecal egg excretion, reduced weight gains and caused anaemia and hypoalbuminaemia in younggrowing pigs as compared with a high-protein diet.

Very variable levels of immunity to a second infection with Schistosoma mansoni were recorded in 7 strains of mice, 12–15 weeks following a small primary infection. When 2 or more strains of mice were assayed at the same time, less variation occurred within the experiment than between different experiments. This evidence suggested variation between pools of cercariae as the main cause of variability in immunity. In direct experiments in one strain of mouse, 2 different pools of cercariae stimulated widely different levels of immunity to the same challenge. Conversely, challenge infections drawn from different pools showed different susceptibility to immunity stimulated by the same primary infection. Individual clones of cercariae, from snails infected with single miracidia, showed a high level of susceptibility to immunity stimulated by a small bisexual infection, or were not susceptible at all. Antigenic polymorphism is the most likely explanation for the differences observed between clones of cercariae. However, indirect immunofluorescence showed the presence of at least 1 common antigen on the surface of schistosomula derived from different clones of cercariae and clone-specific antigens have not been detected.

Chagas disease is a complex tropical pathology caused by the kinetoplastid Trypanosoma cruzi. This parasite displays massive genetic diversity and has been classified by international consensus in at least six Discrete Typing Units (DTUs) that are broadly distributed in the American continent. The main clinical manifestation of the disease is the chronic chagasic cardiomyopathy (CCC) that is lethal in the infected individuals. However, one intriguing feature is that only 30–40% of the infected individuals will develop CCC. Some authors have suggested that the immune response, host genetic factors, virulence factors and even the massive genetic heterogeneity of T. cruzi are responsible of this clinical pattern. To date, no conclusive data support the reason why a few percentages of the infected individuals will develop CCC. Therefore, we decided to conduct a systematic review analysing the host genetic factors, immune response, cytokine production, virulence factors and the plausible association of the parasite DTUs and CCC. The epidemiological and clinical implications are herein discussed.

The enzymatic activities of NTPDase and 5′nucleotidase are important to regulate the concentration of adenine nucleotides, known molecules involved in many physiological functions. Therefore, the objective of this study was to evaluate the activity of NTPDase and 5′nucleotidase in serum and liver tissue of rats infected by Fasciola hepatica. Rats were divided into two groups: uninfected control and infected. NTPDase activity for adenosine triphosphate (ATP) and ADP substrates in the liver was higher compared with the control group at 15 days post-infection (PI), while seric activity was lower. In addition, seric and hepatic samples did not show changes for 5′nucleotidase activity at this time. On the other hand, either NTPDase or 5′nucleotidase activities in liver homogenate and serum were higher at 87 days PI. Early in the infection, low NTPDase activity maintains an increase of ATP in the bloodstream in order to activate host immune response, while in hepatic tissue it decreases extracellular ATP to maintain a low inflammatory response in the tissue. As stated, higher NTPDase and 5′nucleotidase activities 87 days after infection in serum and tissue, probably results on an increased concentration of adenosine molecule which stimulates a Th2 immune response. Thus, it is possible to conclude that F. hepatica infections lead to different levels of nucleotide degradation when considering the two stages of infection studied, which influences the inflammatory and pathological processes developed by the purinergic system.

The aim of this study was to evaluate the anti-trypanosomal effect of treatment with 3′-deoxyadenosine (cordycepin) combined with deoxycoformycin (pentostatin: inhibitor of the enzyme adenosine deaminase) in vitro by using mice experimentally infected with Trypanosoma evansi. In vitro, a dose-dependent trypanocidal effect of cordycepin was observed against the parasite. In the in vivo trials, the two drugs were used individually and in combination of different doses. The drugs when used individually had no curative effect on infected mice. However, the combination of cordycepin (2 mg kg−1) and pentostatin (2 mg kg−1) was 100% effective in the T. evansi-infected groups. There was an increase in levels of some biochemical parameters, especially on liver enzymes, which were accompanied by histological lesions in the liver and kidneys. Based on these results we conclude that treatment using the combination of 3′-deoxyadenosine with deoxycoformycin has a curative effect on mice infected with T. evansi. However, the therapeutic protocol tested led to liver and kidney damage, manifested by hepatotoxicity and nephrotoxicity.

Infections by the protozoan parasite Toxoplasma gondii are widely prevalent in humans and animals in Turkey but little is known of the burden of their clinical toxoplasmosis. Many early papers on toxoplasmosis in Turkey were published in Turkish and often not available widely. Here, we review prevalence, clinical spectrum, epidemiology and diagnosis of T. gondii in humans and animals in Turkey. This knowledge should be useful to biologists, public health workers, veterinarians and physicians. Although one-third of the human population in Turkey is seropositive, the rate of congenital toxoplasmosis is unknown and no information is available in children 12 years old or younger. One large outbreak of acute toxoplasmosis has been reported in 14–18-year old school children in Turkey. An alarming rate (36%) of T. gondii tissue cysts were reported in tissues of sheep and water buffalo meats destined for human consumption; these reports require verification. Genetically, T. gondii strains from domestic cats and wild birds in Turkey were generally classical type II and III, like those prevalent in Europe. A separate genotype, Type 1 Africa, was isolated from two congenitally infected children and a domestic cat in Turkey.

Extensive connective tissue lysis is a common outcome of haplosporidian infection. Although such infections in marine invertebrates are well documented, they are relatively rarely observed in freshwater invertebrates. Herein, we report a field study using a comprehensive series of methodologies (histology, dissection, electron microscopy, gene sequence analysis, and molecular phylogenetics) to investigate the morphology, taxonomy, systematics, geographical distribution, pathogenicity, and seasonal and annual prevalence of a haplosporidian observed in zebra mussels, Dreissena polymorpha. Based on its genetic sequence, morphology, and host, we describe Haplosporidium raabei n. sp. from D. polymorpha – the first haplosporidian species from a freshwater bivalve. Haplosporidium raabei is rare as we observed it in histological sections in only 0·7% of the zebra mussels collected from 43 water bodies across 11 European countries and in none that were collected from 10 water bodies in the United States. In contrast to its low prevalences, disease intensities were quite high with 79·5% of infections advanced to sporogenesis.

Studies on immuno-conglutinin levels in animals infected with T. brucei have shown that immuno-conglutinin appears in rabbits infected with T. brucei ‘M’ variant within 7 days after infection and reaches its peak titre within 30 days. In rabbits infected with the more virulent ‘R’ variant immuno-conglutinin levels rose more rapidly and reached peak titres within 10–14 days after infection.

High levels of immuno-conglutinin are detectable in the sera of rabbits and cats infected with trypanosomes before a significant amount of neutralizing antibody is produced. This difference is most marked in animals infected with the antibody-resistant variant ‘R’ which is more virulent for rabbits.

In animals treated effectively the immuno-conglutinin level dropped to its pre-infection level, while the titre of neutralizing antibody only decreased to a slightly lower level.

No change in the titres of immuno-conglutinin and neutralizing antibody was observed after treatment of animals infected with a drug-resistant strain.

These results are very promising for further field trials and introduce a new approach and method for testing the efficiency of chemotherapy in trypanosomiasis.

Variations in the general protein and 40 enzymes of the 8 European pathotypes of the potato cyst nematode Globodera rostochiensis and G. pallida have been examined by isoelectric focusing (IEF) and cluster analysis. Differences in the protein patterns were observed and the presence of a major band at pH 8·0 allowed the two species to be discriminated. Extra isozymed of peptidase (EC 3.4. 11.*) and esterase (EC 3. 1. 1. 1) were also found in G. rostochiensis. Intra-species variation was seen within G. rostochiensis for superoxide dismutase (EC 1. 15. 1. 1) and within G. pallida for phosphoglucomutase (EC 2. 7. 5. 1) and glucose phosphate isomerase (EC 5. 3. 1. 9). The results suggest that the two species are very similar and the prospect for recognizing their pathotypes by IEF is discussed.

The entry of Theileria parva merozoites into bovine erythrocytes in vivo is described and compared to sporozoite invasion of lymphocytes. Merozoites make initial contact with erythrocytes with any part of their surface and invasion of the host cell does not require the re-orientation of the apical end of the merozoite towards the surface of the erythrocyte. After the initial attachment the merozoite and host cell membranes form a continual close junction with the two apposed membranes separated by a 6–8 nm gap containing moderately dense material. The progressive circumferential ‘zippering’ of these closely apposed membranes leads to the movement of the parasite into the erythrocyte. The newly internalized merozoite which is completely surrounded by the erythrocyte plasma membrane escapes from this enclosing membrane by a process involving the discharge of at least the rhoptries; whether the merozoite also contain other types of secretory organelles (e.g. micronemes, microspheres or dense bodies) remains to be determined. Morphologically, the events involved in merozoite invasion of erythrocytes are almost identical to the process of sporozoite invasion of lymphocytes but differ significantly from the entry process of the invasive stages of other Apicomplexan parasites.

The transmission of Hammondia heydorni among sheep, goats, cattle, dogs and coyotes is described. Oocysts of H. heydorni, obtained from dog faeces by feeding naturally infected goat meat, were fed to an experimental goat. After 312 days tissues from this animal were fed to 2 dogs. One dog, which received goat muscle, shed oocysts, whereas the other dog which received brain, spleen, kidneys, lungs and liver did not. Oocysts from the dog fed goat muscle were fed to an experimental sheep. After 73 days sheep tissues were fed to a dog and a coyote, both of which shed oocysts 5–8 days later. A second isolate of H. heydorni was obtained by feeding naturally infected beef to a coyote. These oocysts were fed to a single goat and sheep and after 71 days, muscle from these 2 animals was fed to 2 dogs and 2 coyotes, all of which shed oocysts 5–8 days later. None of the animals inoculated with H. heydorni became ill and no Hammondia-like organisms were found in tissue sections from the herbivores. Another dog shed H. heydorni-like occysts between 7 and 10 days after ingesting naturally infected muscles from a moose. These results indicate that H. heydorni infects goats, sheep, moose and coyotes in addition to cattle and dogs.