Since Professor Kellogg has published a list of Mallophaga, in Wytsman's Genera Insectorum, so recently as 1908, my reasons for preparing the present publication require an explanation. This explanation involves some criticism of Kellogg's list, but my main reasons are concerned rather with the plan of this list than with the few errors and omissions that I indicate.

The present review will examine epidemiological perspectives and be confined mainly to the results of those field studies published since 1975 in order to provide concrete scientific evidence of the effect of ascariasis on childhood malnutrition, particularly on growth. The field studies were done in many developing countries from Africa, Asia and Latin America, using cross-sectional and intervention studies in which anthelmintics were employed, with different dosing frequency and follow-up periods ranging from 33 days to 2 years. In general, a better nutritional status in terms of growth, lactose tolerance, vitamins A and C, and albumin levels were observed among Ascaris–free or treated than among Ascaris–infected or untreated children even in cross-sectional or non-randomized studies. More importantly, the improvement in weight or height after chemotherapeutic treatment was found to be significant particularly in those randomized controlled studies with an initially high prevalence of ascariasis and malnutrition, a low prevalence of other intestinal parasites, repetitive and regular treatments of children with tetramisole, levamisole or pyrantel, within a period of 12 or 24 months. Reasons for failures to detect improved growth in some studies are provided. This review strongly indicates that A. lumbricoides infection definitely retards childhood growth.

Chagas' disease is a debilitating but comparatively neglected illness that affects about 15 million people. There is an urgent need to develop new, more effective, and less-toxic compounds. In this study, we assessed the in vitro anti-trypanosomal activity of the sesquiterpene elatol from the Brazilian red seaweed Laurencia dendroidea. We used electron microscopy to evaluate the effect of elatol on the morphology and ultrastructure of the parasite. Elatol showed a dose-dependent effect against the epimastigote, trypomastigote, and amastigote forms, with IC50 values of 45·4, 1·38, and 1·01 μm, respectively. Observation of treated intracellular amastigotes by light microscopy demonstrated a total elimination of the infection at a dose of 3·0 μm. In addition, the compound did not affect the red blood cells, and the CC50 value for LLCMK2 cells was 27·0 μm. Transmission and scanning electron micrographs showed aberrant-shaped cells and breaks in the plasma membrane, prominent swollen mitochondria, and extensive formation of cytoplasmic vacuoles in all the forms. This is the first report of the anti-trypanosomal effect of the sesquiterpene elatol.

The dilution effect, that high host species diversity can reduce disease risk, has attracted much attention in the context of global biodiversity decline and increasing disease emergence. Recent studies have criticized the generality of the dilution effect and argued that it only occurs under certain circumstances. Nevertheless, evidence for the existence of a dilution effect was reported in about 80% of the studies that addressed the diversity–disease relationship, and a recent meta-analysis found that the dilution effect is widespread. We here review supporting and critical studies, point out the causes underlying the current disputes. The dilution is expected to be strong when the competent host species tend to remain when species diversity declines, characterized as a negative relationship between species’ reservoir competence and local extinction risk. We here conclude that most studies support a negative competence–extinction relationship. We then synthesize the current knowledge on how the diversity–disease relationship can be modified by particular species in community, by the scales of analyses, and by the disease risk measures. We also highlight the complex role of habitat fragmentation in the diversity–disease relationship from epidemiological, evolutionary and ecological perspectives, and construct a synthetic framework integrating these three perspectives. We suggest that future studies should test the diversity–disease relationship across different scales and consider the multiple effects of landscape fragmentation.

Entomopathogenic nematodes (EPN) are soil-transmitted parasites and their foraging strategies are believed to range from ‘ambush’ to ‘cruise’ foragers. However, research on their behaviour has not considered the natural habitat of these nematodes. We hypothesized that EPN behaviour would be influenced by soil habitat quality and tested this hypothesis using 2 EPN species Steinernema carpocapsae (an ‘ambusher’) and Heterorhabditis megidis (a ‘cruiser’) in 2 contrasting habitats, sand and peat. As predicted from previous studies, in sand most S. carpocapsae remained at the point of application and showed no taxis towards hosts, but in peat S. carpocapsae dispersed much more and showed a highly significant taxis towards hosts. H. megidis dispersed well in both media, but only showed taxis towards hosts in sand. In outdoor mesocosms in which both species were applied, S. carpocapsae outcompeted H. megidis in terms of host finding in peat, whereas the opposite was true in sand. Our data suggest that these 2 EPN may be habitat specialists and highlight the difficulties of studying soil-transmitted parasites in non-soil media.

Introduction. The ectoparasitic honey bee mite Varroa destructor feeds on the haemolymph of the honey bee, Apis mellifera, through a single puncture wound that does not heal but remains open for several days. It was hypothesized that factors in the varroa saliva are responsible for this aberrant wound healing. Methods. An in vitro procedure was developed for collecting salivary gland secretions from V. destructor. Mites were incubated on balls of cotton wool soaked in a tissue culture medium (TC-100), and then induced to spit by topical application of an ethanolic pilocarpine solution. Results. Elution of secretions from balls of cotton wool, followed by electrophoretic analysis by SDS-PAGE and electroblotting indicated the presence of at least 15 distinct protein bands, with molecular weights ranging from 130 kDa to <17 kDa. Serial titration of V. destructor salivary secretions in TC-100 followed by an 18-h incubation with haemocytes from the caterpillar, Lacanobia oleracea, indicated that the secretions damage the haemocytes and suppresses their ability to extend pseudopods and form aggregates. Conclusion. We suggest that these secretions facilitate the ability of V. destructor to feed repeatedly off their bee hosts by suppressing haemocyte-mediated wound healing and plugging responses in the host.

Ultrastructural studies on adult Nippostrongylus brasiliensis removed at varying stages after infection from rats given a single dose of 2000 infective larvae have shown that changes in their cytology occur and that these can be correlated with the onset and development of immunity to this nematode in the host. The most noticeable changes are resorption of spermatozoa by the male reproductive tract, a drop in egg production, changes in the cytology of the intestinal cells, and the appearance of many large droplets, which look like droplets of lipid, in the cytoplasm of the hypodermis, muscles, excretory glands, reproductive system and the intestine. There are no obvious changes in the structure of the cuticle of the nematode during the course of infection. Possible reasons for the onset of these changes in the nematode are discussed.

Much of this work was carried out during the tenure of grants from the U.S. Public Health Service (grant number AI 04275) and from the Agricultural Research Council while I was working at the Molteno Institute in Cambridge. I wish to thank the late Professor J. D. Boyd and Dr C. C. D. Shute of the Department of Anatomy, Cambridge, for permission to use the electron microscopes, Mrs B. Fisher for technical assistance and Mr Paul Rogers for assistance with the photography.

The surface architecture of adult male Schistosoma mansoni was explored using a range of lectins with differing carbohydrate specificities. Highest specific binding was achieved with concanavalin A and the agglutinin of molecular weight 60000 from Ricinus communis; the binding of wheat germ agglutinin was mostly non-specific. Small amounts of peanut agglutinin and soybean agglutinin binding were observed and the binding of these lectins was increased by pre-treating the parasite with neuraminidase. The fucose binding protein of Lotus tetragonolobus failed to bind. These results indicate that mannose and/or glucose, galactose, N-acetyl-glucosamine, N-acetyl-galactosamine and sialic acid are exposed on the surface of the adult male schistosome.

1. The morphology and life-history of Dientamoeba fragilis, as observable in cultures, are described and illustrated, and the stages correlated with those commonly found in human faeces.

2. The nuclear structure especially is reinterpreted, and nuclear and cytoplasmic division are described in detail.

3. It is shown that the “normal” binucleate condition of this “amoeba” represents an arrested telophase stage of mitosis—the “granules” in the nuclei being really chromosomes (constant in number), and the strand connecting the nuclei being a persistent centrodesmus. The chromosome number is probably 6 (certainly not 4).

4. Binary fission is the only method of reproduction hitherto observed: no cysts or other stages in the life-history have been discovered.

5. Attempts to transmit D. fragilis to a man and 2 macaques (M. rhesus and M. sinicus) by administration of trophic amoebae per os—and in the case of M. rhesus inoculation per anum—were unsuccessful. It was also found impossible to infect chickens permanently by injection per anum (though one chick acquired an infection lasting for a week).

6. Consideration of its cytology and development leads to the conclusion that D. fragilis is not a true amoeba but an aberrant flagellate closely related to Histomonas. No flagellate stages, however, have yet been discovered.

7. Some consequences of this conclusion are briefly discussed, and hopeful directions for further inquiries are indicated.

8. On analogy with Histomonas, it is suggested that D. fragilis may be conveyed from man to man not by direct oral infection with trophic forms but in the ova of a nematode worm—possibly Trichuris (or Ascaris?).

We measured in vitro anthelmintic activity in extracts from 85 species of Australian native shrub, with a view to identifying species able to provide a degree of worm control in grazing systems. Approximately 40% of the species showed significant activity in inhibiting development of Haemonchus contortus larvae. The most active extracts showed IC50 values of 60–300 μg/ml. Pre-incubation with polyvinylpolypyrrolidine removed the activity from some extracts, implicating tannins as the bioactive agent, while in other cases the pre-incubation had no effect, indicating the presence of other anthelmintic compounds. Plant reproductive maturity (onset of flowering or fruiting) was associated with increasing anthelmintic activity in some species. Variability was observed between plants of the same species growing in different environments, while variation between individual plants of the same species within a single field suggests the existence of distinct chemotypes. Significant activity against adult H. contortus worms in vitro was also demonstrated in a limited number of extracts tested against this life stage. Our study indicates that there is potential for Australian native shrubs to play an anthelmintic role in grazing systems, and highlights some plant biology factors which will need to be considered in order to maximize any anthelmintic effects.

Saliva inoculated by sandfly females during feeding stimulated production of high levels of anti-saliva antibodies. To determine whether 3 species of the genus Phlebotomus have species-specific salivary antigens we performed dot-blots and immunoblots using sera from mice, hamsters and rabbits repeatedly bitten by sandflies. Important differences were found in the antigen components of the salivary gland lysates (SGL) of Phlebotomus papatasi, P. perniciosus and P. halepensis. In total 4–9 species-specific antigens were detected in each species by immunoblotting. Cross-reactivity was not detected between P. papatasi and the other species tested; in the SGL of P. papatasi sera from animals bitten by this species recognized 5–7 major antigens while sera from animals bitten by other species did not react. A weak cross-reaction was observed between P. perniciosus and P. halepensis; in SGL from P. perniciosus, the sera from rabbits and hamsters bitten by this species recognized about 8 intense bands while sera from animals bitten by P. halepensis reacted weakly with up to 4 saliva polypeptides.

Urbanization involves a physical change in which increasing proportions of populations live in urban settings, however defined. It also implies considerable changes in the ways in which these people live, how they earn their livelihoods, the food which they eat, and the wide range of environmental factors to which they are exposed. There is another underlying assumption that, increasingly, urban populations will be more healthy than their rural counterparts and that higher levels of urbanization will equate with better health status. This paper discusses some of the assumptions underlying this contention. It takes issue with certain of them, particularly the assumption that urbanization affects the health of all residents equally. It is manifestly evident that in many cities, particularly in the developing world, the poor are exposed to greater risks and have much lower health status than their richer neighbours. In addition, whilst urban residents may theoretically have a better access to health care and services than do residents in many rural areas, and whilst many indicators of health do appear better in more highly urbanized societies than ones less so, there are caveats. The paper introduces the concept of epidemiological transition, which suggests that, whilst life expectancy might be higher in many urbanized countries and in certain cities, the inhabitants are often merely suffering from different forms of ill-health, often chronic or degenerative, rather than infective. In certain cities in middle-income countries, residents, particularly the poor, are exposed to a double risk of both infection and chronic degenerative ailments. The paper concludes with a consideration of more general recent statements from the World Health Organization among others, on the impact of urbanization on health. The ‘Healthy Cities’ project is also discussed. WHO identifies a range of general determinants of urban health: physical, social, cultural and environmental. Many represent the by-products of modernization and especially industrialization. It is emphasized that urbanization, and the concentration of human beings into new areas in particular, can bring exposure to new risk factors for large numbers of people. The growth of infectious and parasitic disease in some urban settings must therefore be recognized, as must the emergence of chronic diseases, with the concomitant need for investment in new types of health and social care. However, a number of constraints militate against the achievement of improved urban health, especially in developing countries. The paper concludes by considering some important constraints: the very scale of urban health problems; the impacts of structural adjustment programmes which cut public expenditure on environmental health, health services and nutrition, thereby increasing the vulnerability of the poor; urban management problems; lack of political will; and the difficulties of measuring change in health and effects of policies.

Outdoor observations were made on the rate of development of the free-living stages of H. contortus at different times of the year, and on the migratory activities and longevity of the larvae in faeces, on herbage and in soil.

The effects of temperature and humidity on the survival and development of eggs and larvae, both in faeces and when separated from the faeces, were studied in the laboratory.

The results of these observations are discussed in relation to the heavy mortality of the free-living stages of H. contortus and to the transmission of infection in the field.

Changes associated with schizogony and gametogony in Eimeria tenella have been studied by means of electron microscopy.

In infections of E. tenella both small and large schizonts are formed, and in both cases merozoites are developed by a surface ‘budding’ mechanism. The final severance of the merozoite from the schizont appears to give rise to the dorsal pore of the merozoite. Newly formed merozoites contain structures which are absent in the mature organism.

Early in microgametogony the nucleus of the microgametocyte divides repeatedly to produce a number of smaller nuclei which migrate peripherally in the cell. The chromatin aggregates into the peripheral part of each nucleus, which then elongates to form the nucleus of the of microgamete. That part of the gametocyte nucleus which is devoid of chromatin, probably gives rise to the perforatorium and three flagella of the gamete. Residual material is left in the gametocyte cytoplasm in the form of a gametogenic cyst.

‘Wall-forming’ bodies are present in the earliest macrogametocyte and ‘dark bodies’ are developed later. After fertilization these bodies migrate to the periphery of the zygote. In E. tenella the oocyst wall is trilaminate. The limiting membrane of the zygote separates from the cell to become the outermost membrane of the cyst wall. The middle layer of the cyst wall is developed from the ‘dark bodies’, and the ‘wall forming’ bodies give rise to the inner layer of the oocyst wall.

The excretions-secretions (E-S) of Acanthocheilonema viteae consist mainly of one product, molecular weight 62 kDa. This molecule is synthesized during the vertebrate phase of the parasite life-cycle and is first detectable in the E-S of L4 parasites. It is cross-reactive with E-S of human filarial parasites as a consequence of possessing a phosphorylcholine (PC) moiety. The 62 kDa molecule has been employed as a model for the study of the origin and fate of filarial E-S. Immunohistological analysis has shown the molecule to be located predominantly in the parasite gut. Transplantation of adult female [S] methionine pulsed worms into uninfected jirds resulted in the radio-labelled secreted 62 kDa antigen being detected in the bloodstream within 4 h by SDS–PAGE/immunoprecipitation analysis. The systemic half-life of the molecule as estimated by clearance of injected, purified I-labelled material was measured in naive and infected jird hosts.

A survey of lungworm infection in rats in Queensland has shown that 23% of Rattus norvegicus, 6·5% of R. rattus 4·5% of R. fuscipes and 0% of Melomys cervinipes were infected with lungworms. Detailed examination of the lungworms revealed that there are two distinct species; one is Angiostrongylus cantonensis which was found to occur in R. norvegicus and R. rattus, the other is a new species, namely, A. mackerrasae, which was found in R. fuscipes in an area of rainforest near Brisbane. Some R. norvegicus in Brisbane also harboured A. mackerrasae. The two species were distinguished by the length of the spicules, relative length and appearance of the postero-lateral ray in the male, the presence of a minute projection at the tip of the tail in the female, length of the vagina and the distance between anus and vulva. The first-stage larvae of the two species were found to be identical. As this species has been found to be the only lungworm in R. fuscipes which is an indigenous Australian rat, it is suggested that A. mackerrasae may have originated in the Australian region.

I wish to express my sincere gratitude to Professor J. F. A. Sprent and Dr L. R. Ash for their advice and encouragement during this study. Special thanks are also due to Miss M. Cremin for her assistance and to Mr H. Lavery for providing specimens from North Queensland. This work was supported by a grant from the U.S. Department of Health, Education and Welfare No. A 107023–02.

Previous workers have described the curious method by which the female bed-bug is fertilized. They have suggested that the large quantity of sperm injected serves some function other than that of fertilizing the egg.

The rate of metabolism of the virgin bug is much less than that of the fertilized female.

Ovarian development never occurs until the female has been fertilized. After fertilization, egg development is apparently controlled by a hormone produced by the corpus allatum.

Living sperm will always be found in the spermathecae of females which are laying fertile eggs.

The so-called imperfect eggs produced when the sperm is exhausted are normal save for being unfertilized. They have been considered as malformed because of their tendency to shrivel quickly in dry air.

Sperm remains viable in the female for a definite period depending on the temperature. This period is longer at low than at high temperature. Provided a certain minimum amount of sperm is introduced (this minimum is less than the quantity introduced by a well-nourished male at one copulation), the period of viability of sperm is the same no matter how many eggs are produced. The number of eggs depends only on the amount of food taken.

There is no evidence that the sperm serves any nutritive function in the female.

1. It has been shown by spectroscopic and histochemical methods that eight representative species of Polyopisthocotylea feed mainly on the blood of their hosts.

2. The blood is probably haemolysed fairly rapidly and subsequently absorbed by amoeboid ingestion, the globin moiety of the haemoglobin forming the chief nutriment of the parasite and the unaltered haematin being eliminated either by its discharge from epithelial cells into the gut lumen or by the sloughing off of intact epithelial cells.

3. In a more limited sample of skin-and cloaca-inhabiting Monopisthocotylea there was no evidence of a blood-feeding habit.

This study serves to clarify the current status of canid and felid Ancylostoma species present in Australia. The morphological identification of A. ceylanicum from cats for the first time in Townsville, Australia, appears to be in error, together with the genetic markers provided for the species. Morphological and genetic data presented herein provide strong evidence that the hookworms from cats in Towsville are not A. ceylanicum as previously identified (i.e. the first report of this species in Australia), but are A. braziliense. Therefore the subsequent genetic markers established for A. ceylanicum in subsequent molecular studies based on these Townsville specimens should also be attributed to A. braziliense. Based on this information, a study of canine hookworm species present in northern India is also in error and it is apparent that the hookworms found in this region are those of A. ceylanicum. The distribution of A. braziliense and A. ceylanicum in the Americas and Asia Pacific region is discussed together with the importance of combining parasite morphology with genetic data for parasite diagnosis in epidemiological studies.

The ABA-1 protein of Ascaris lumbricoides (of humans) and Ascaris suum (of pigs) is abundant in the pseudocoelomic fluid of the parasites and also appears to be released by the tissue-parasitic larvae and the adult stages. The genes encoding the polyprotein precursor of ABA-1 (aba-1) were found to be arranged similarly in the two taxa, comprising tandemly repeating units encoding a large polyprotein which is cleaved to yield polypeptides of approximately 15 kDa which fall into 2 distinct classes, types A and B. The polyprotein possibly comprises only 10 units. The aba-1 gene of A. lumbricoides is polymorphic, and the majority of substitutions observed occur in or near predicted loop regions in the encoded proteins. mRNA for ABA-1 is present in infective larvae within the egg, and in all parasitic stages, but was not detectable in unembryonated eggs. ABA-1 mRNA was confined to the gut of adult parasites, and not in body wall or reproductive tissues. Recombinant protein representing a single A-type unit for the A. lumbricoides aba-1 gene was produced and found to bind retinol (Vitamin A) and a range of fatty acids, including the pharmacologically active lipids lysophosphatidic acid, lysoplatelet activating factor, and there was also evidence of binding to leukotrienes. It failed to bind to any of the anthelmintics screened. Differential Scanning Calorimetry showed that the recombinant protein was highly stable, and unfolded in a single transition at 90·4 °C. Analysis of the transition indicated that the protein occurs as a dimer and that the dimer dissociates simultaneously with the unfolding of the monomer units.