It is perhaps unnecessary to introduce this series of papers with the remark that the chief interest in the study of the Mallophaga centres about the problems associated with their distribution and that these problems are in some measure at least coincident with the problem of the genetic relationship of their hosts. All this has been said very clearly, many times and by various writers. Yet I repeat it again, for it is this interest which is responsible for the papers to follow and it is as a contribution toward the study of these problems that they are intended, notwithstanding the circuitous route that may be followed in arriving at this goal.

The C57BL6 strain of mice is highly susceptible to Plasmodium berghei sporozoite infections and consequently requires repeated immunizations with irradiated sporozoites to obtain protective immunity. After a live sporozoite challenge in the immunized hosts, hepatic-stage parasites found in the liver after 48 h are of different sizes – small schizonts corresponding to blocked forms (derived from irradiated sporozoites), and schizonts of intermediate size (derived from live sporozoites). Large schizonts corresponding to mature hepatic forms are found only in unimmunized but challenged C57BL6 mice. Using monoclonal and polyclonal antibodies directed to liver-stage parasites, different patterns of binding reactivity to the above forms are observed. More than 20% of the irradiated sporozoites transform into blocked forms after immunization and persist in the liver. Upon sporozoite challenge in such immunized animals the rate of transformation of sporozoites into hepatic parasites is less than 2%. These observations shed light on the fate of live sporozoite development in irradiated sporozoite-immunized C57BL6 mice.

Vertically transmitted parasites (VTPs) such as Wolbachia are expected not only to minimize the damage they inflict on their hosts, but also to protect their hosts against the damaging effects of coinfecting parasites. By modifying the fitness costs of the infection, VTPs can therefore play an important role in the evolution and epidemiology of infectious diseases.

Using a natural system, we explore the effects of a Wolbachia–Plasmodium co-infection on mosquito fecundity. While Plasmodium is known to frequently express its virulence by partially castrating its mosquito vectors, the effects of Wolbachia infections on mosquito fecundity are, in contrast, highly variable. Here, we show that Plasmodium drastically decreases the fecundity of mosquitoes by ca. 20%, and we provide the first evidence that this decrease is independent of the parasite's burden. Wolbachia, on the other hand, increases fecundity by roughly 10%, but does not alter the tolerance (fecundity–burden relationship) of mosquitoes to Plasmodium infection.

Although Wolbachia-infected mosquitoes fare overall better than uninfected ones, Wolbachia does not confer a sufficiently high reproductive boost to mosquitoes to compensate for the reproductive losses inflicted by Plasmodium. We discuss the potential mechanisms and implications underlying the conflicting effects of these two parasites on mosquito reproduction.

For the opportunity of studying this collection of round-worms from Zanzibar I am greatly indebted to Mr W. Mansfield-Aders, Economic Biologist to the Zanzibar Government.

1. Atebrin given during the incubation period delays the appearance of parasites in the blood of birds infected by direct blood inoculation with Plasmodium relictum.

2. If given to birds infected by the bites of mosquitoes it does not retard the appearance of parasites in the blood, when given either before, or after, the infective bites, but it has some action in diminishing the severity of the attack and the degree of splenic enlargement.

3. Parasites appear in the blood of birds, infected by sporozoites, actually during the course of atebrin treatment if this is prolonged beyond the normal incubation period.

4. When asexual parasites appear in the blood of mosquito-infected birds after atebrin treatment they are abnormal in appearance and devoid of pigment grains; gametocytes are rarely seen in the blood of such birds, but if present they have normal pigment granules.

5. Treatment with atebrin produces peculiar bodies in the blood cells of canaries.

Certain facts are known concerning the correlation of the distribution of animal species and the hydrogen ion concentration of the soil and water. An attempt is made to apply them to the distribution of malarial fever, as illustrating insect borne disease, and to some of the numerous Trematode infections, afflicting man and other animals, in which snails act as intermediate hosts. The importance of measurements of hydrogen ion concentration (by the colorimetric method) by field workers on the distribution of animals is urged.

The writer wishes to acknowledge his indebtedness to Dr M. V. Lebour for the suggestion that snails may prove a suitable group for the study of the relation between the reaction of the habitat and animal distribution.

Murine monoclonal and polyclonal antisera, raised against the 38 kDa subunit of Echinococcus granulosus antigen 5, were used to investigate the tissue distribution of the antigen in hydatid cysts. Immunoreactivity was visualized by indirect immunofluorescence on whole protoscoleces, and ultrastructural immunocytochemistry utilizing colloidal gold-based labelling procedures on unsectioned and cryosectioned brood capsules and protoscoleces. In protoscoleces, the 38 kDa subunit of antigen 5 was localized at the interface of parenchymal cells and associated extracellular matrices, as well as along the interface of the tegumentary syncytium in the somal region and its basal matrix. Cytoplasmic labelling of parenchymal cells was rare; when observed, it was associated with vesicles and membranes in cytoplasmic extensions of parenchymal cells. In brood capsules, the antigen was associated with the external face of the plasma of degenerating parenchymal cells. The 38 kDa subunit occurs along the extracellular face of cell membranes, suggesting that antigen 5 is either a component of the membranes or associated extracellular matrices.

I. In the following three experiments it will be shown that ripe eggs of Ascaris suilla can hatch in the intestine of the pig, that the larvae issuing from these eggs enter the body of the pig and pursue the same course through the body as in the rat and mouse. They have been found in the lung of the pig from the 6th to the 8th day and in the trachea on the 8th day. Dead larvae have been found in the faeces of the pig on the 11th day after infection (Expt. 6).

Food intake, body weight changes, serum protein and amino acid concentrations were measured during the course of primary infections of Nippostrongylus brasiliensis in rats fed on either a 2% protein (casein) diet or a 16% protein diet (Oxoid 41 B). Total serum protein concentration declined from 77·84±5·35 mg/ml in uninfected well-nourished rats to 54±3·29 mg/ml in rats at 9 days post-infection (p.i.). A reduction from 47·80±2·78 to 40·38±5·62 mg/ml had occurred in protein-malnourished rats by day 6 p.i. The hypoproteinaemia was accompanied by significant hypoalbuminaemia in the protein-malnourished rats and concentrations fell from approximately 33 to 19 mg/ml at the time of peak infection. Six days after inoculation, a significant increase was detected in the concentration of serum amino acids in both well-nourished and protein-malnourished rats; the effect was more prolonged for non-essential than for essential amino acids. The results are discussed briefly in relation to recent work on the control of protein metabolism during malnutrition.

Interactions between tapeworm species in a single host offer intriguing opportunities for immunological studies that attempt to identify the mechanism(s) underlying protection against cestode infections. Mice that are immunized against Hymenolepis citelli infections were shown to be refractory to subsequent H. diminuta challenge infections. The reciprocity of the response was also demonstrated, although the protection recorded for H. diminuta when mice are sensitized with H. citelli is weaker than that observed when mice are primed with H. diminuta against H. citelli challenge. H. citelli was also shown to be expelled simultaneously during the rejection phase of H. diminuta in concurrent infections, indicating the susceptibility of the former tapeworm to the rejection mechanism initiated by the latter. H. microstoma immunized mice were shown to be strongly protected against heterologous H. citelli challenge. However, mice primed against H. citelli were not as strongly protected against H. microstoma challenge infections: a statistically significant protection was obtained only after a 12-cysticercoid H. citelli primary infection, although a 6-cyst infection did stunt the growth of H. microstoma challenge worms. It is presently suggested that the cross-protective responses observed in the study between H. citelli, H. diminuta and H. microstoma may have emanated from a specific immunological cross-reactivity due to the sharing of similar immunogens.

Mutations in pfcrt K76T are associated with chloroquine resistance in Plasmodium falciparum. Previous studies of K76T mutations in Senegal reported the association of T76 with in vitro-resistant isolates, but this mutation was also prevalent in chloroquine-sensitive isolates. This suggests involvement of additional genetic loci in modulating chloroquine resistance. Additional pfcrt polymorphisms at codons A220S, Q271E, N326S and R371I have been found in chloroquine-resistant isolates. We wanted to test if sequential acquisition of mutations at these codons leads to in vitro chloroquine resistance. Stepwise accumulation of mutations was not detected, rather there was almost complete linkage between the pfcrt K76T mutation and polymorphisms in these codons. Therefore these additional polymorphisms do not enhance the correlation between pfcrt T76 and chloroquine resistance in Senegal. These data suggest that in vitro chloroquine resistance requires the genetic background of the pfcrt K76T mutation and additional mutations in genetic loci outside the pfcrt gene.

A critical review is presented of the species of Dinobothrium and their probable synonyms. D. septaria v. Beneden and D. planum Linton are accepted as valid species. D. keilini Sproston and D. plicitum Linton are regarded as of doubtful status, the former being probably a synonym of D. septaria, while D. plicitum may be a synonym of D. planum. The type-specimens of D. keilini and of D. paciferum Sproston have been re-examined. A new interpretation is offered of the structure of the scolex of D. paciferum, and some other details of its anatomy are redescribed. A small species from Cetorhinus maximus is described, which is very similar to, and may prove to be identical with, Dinobothrium paciferum. As it apparently differs in having the neck and parts of the bothria covered with spines, it is treated as a distinct species and named D. spinosum. The question of the specific identity of the known larval forms of Dinobothrium is briefly discussed.

Detailed accounts of the morphology of the elephant louse and of its phylogenetic affinities and origin are given. The main points noted are: The peculiarity of the knobs and plate in the head are described. The mouthparts are described, a notable feature being the rotation of the mandible to 180 degrees. Structural peculiarities of the thorax with the muscles are given. The abdomen is found to consist of eight segments. The alimentary canal is described; no crop has been found. The histology of Weber's organ is given, and it is held that this organ is excretory in function. The structure of the spiracle is described, no spiracular gland has been found. The reproductive organs are described. In the female, the follicular epithelium of the ovary is binucleate and a spermatheca is present. In the male, the testis is bi-follicular. The affinities of the elephant louse are discussed and the creation of a new order, the Rhyncophthiraptera, to accommodate Haematomyzus, is suggested.

Gland cells surrounding the oesophagus in the redia of Fasciola hepatica are described. These cells produce electron-dense, membrane-bound vesicles which have an unusual mechanism for secretion of their contents.

Helminthes have the capacity to modulate host immunity, leading to positive interactions with coinfecting microparasites. This phenomenon has been primarily studied during coinfections with a narrow range of geo-helminthes and intracellular microparasites in human populations or under laboratory conditions. Far less is known regarding differences in coinfection dynamics between helminth types, the range of microparasites that might be affected or the overall community-level effects of helminth infections on microparasites in wild systems. Here, we analysed the presence/absence and abundance patterns of enteric parasites in long-tailed macaques (Macaca fascicularis) on the island of Bali, Indonesia, to assess whether naturally occurring helminth infections were associated with increased shedding of the most common intracellular (Cryptosporidium spp., Isospora spp.) and extracellular (Entamoeba spp., Giardia spp.) microparasites. We also comparatively assessed the statistical correlations of different helminth taxa with microparasite shedding to determine if there were consistent relationships between the specific helminth taxa and microparasites. Helminth infections were associated with increased shedding of both intracellular and extracellular microparasites. Platyhelminthes repeatedly displayed strong positive correlations with several microparasites; while nematodes did not. Our results indicate that helminthes can influence microparasite community shedding dynamics under wild conditions, but that trends may be driven by a narrow range of helminthes.

Heparin-binding proteins (HBPs) play a key role in Trypanosoma cruzi-host cell interactions. HBPs recognize heparan sulfate (HS) at the host cell surface and are able to induce the cytoadherence and invasion of this parasite. Herein, we analysed the biochemical properties of the HBPs and also evaluated the expression and subcellular localization of HBPs in T. cruzi trypomastigotes. A flow cytometry analysis revealed that HBPs are highly expressed at the surface of trypomastigotes, and their peculiar localization mainly at the flagellar membrane, which is known as an important signalling domain, may enhance their binding to HS and elicit the parasite invasion. The plasmon surface resonance results demonstrated the stability of HBPs and their affinity to HS and heparin. Additionally, gelatinolytic activities of 70 kDa, 65·8 kDa and 59 kDa HBPs over a broad pH range (5·5–8·0) were revealed using a zymography assay. These proteolytic activities were sensitive to serine proteinase inhibitors, such as aprotinin and phenylmethylsulfonyl fluoride, suggesting that HBPs have the properties of trypsin-like proteinases.

Even if we do not always acknowledge the fact, nutrition is a fundamental aspect of symbiosis and parasitism. (1) The significance of nutrition often forms a basic feature in schemos of classification of the various associations between living organisms (see Read, 1908; Whitfield, 1979). (2) The growth and reproduction of different parasites appear to Vary in response to the nutrition of the host (see Mettrick & Podesta, 1974; Nesheim, Crompton, Arnold & Barnard, 1977; 1978; Parshad, Crompton & Nesheim, 1980). (3) The course of a parasitic infection may also vary in response to the nutritional status of the host and perhaps such variations are the result of the affocts of nutrition on the host's immune response (Chandra & Nowberne, 1977; Chandra, 1980). (4) Finally, parasitic disease is well known to be much more scrious in undernourished hosts (see Chandra & Newberne, 1977); when man's the deprived host, the impact of infections and parasitic disease on young children is Particularly severe and distressing (Latliam, 1975).