Gametogenesis in Dirofilaria immitis has been studied principally by means of the aceto-orcein chromosomal squash technique, but with additional ultrastructural observations. A terminal germinative zone, in which a continuous and rapid division of germ cells occurs, has been identified in the gonoduct of both male and female worms. Approximately 20% of cells within these germinative zones were in arrested mitotic division following the incubation in vitro of excised gonads in 0·01% colchicine for 4 h. All primary spermatocytes within a 1–2 cm length of the testis proximal to the germinative zone were at the prophase of the 1st meiotic division. In the corresponding region of the ovary, the primary oocytes were similarly at the prophase of the 1st meiotic division in 75% of female worms examined but in the remaining 25% all primary oocytes possessed markedly less condensed, probably interphase nuclei. A possible hormonal control of the cyclical development of primary oocytes, but not primary spermatocytes in D. immitis is suggested. In most of the remaining length of the gonoducts beyond this region of cells at meiotic prophase, the chromatin material of both primary spermatocytes and oocytes is decondensed. Recondensation of chromosomes in the spermatocytes is observed just prior to entry into the seminal vesicle, where meiosis I is completed and meiosis II takes place. In the primary oocyte, completion of meiosis only occurs after fertilization within the seminal receptacle by an entire male gamete. Following the 2 meiotic divisions in the oocyte and subsequent extrusion of the 2 polar bodies, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n = 10). Male chromosomes within the oocyte remain visible throughout late oogenesis and fusion occurs without the formation of pronuclei.

Groups of mice were infected with 1,5 or 10 cysticercoids of Hymenolepis microstoma. Infections were terminated with the anthelmintic ‘Zanil’ after 5, 15 or 30 days and the mice challenged with 6 cysticercoids. The growth of the worms in the secondary infections decreased as either the intensity (number of cysticercoids administered) or duration of the primary infections increased. It is postulated that the results have an immunological basis.

Infectivity of Pseudechinoparyphium echinatum cercariae to 11 species of gastropod was examined experimentally. Broad specificity and differential host—parasite compatibility were exhibited. Nine gastropod species functioned as second intermediate hosts. Planorbarius corneus, Physa fontinalis, Lymnaea peregra and Biomphalaria alexandrina showed high levels of compatibility with the parasite. In single-species exposures over 90% of cercariae encysted in each of these hosts. Low compatibility with the first intermediate host species Lymnaea stagnalis may be a mechanism preventing super-infection of emitting snails. Cercariae did not infect the prosobranchs Bithynia tentaculata and Viviparus viviparus. Experimental infection of a host community comprised of 8 European gastropod species revealed an order of host utilization similar to that shown in single-species exposures. However, cercarial transmission success in P. fontinalis and L. peregra (compared to that in P. corneus) was significantly reduced. This may have been due to the marked preference to cercariae for P. corneus compared to the other two highly suitable hosts for whom cercariae showed equal preference.

Toxoplasma gondii is a globally distributed parasite infecting humans and warm-blooded animals. Although many surveys have been conducted for T. gondii infection in mammals, little is known about the detailed distribution in localized natural populations. In this study, host genotype and spatial location were investigated in relation to T. gondii infection. Wood mice (Apodemus sylvaticus) were collected from 4 sampling sites within a localized peri-aquatic woodland ecosystem. Mice were genotyped using standard A. sylvaticus microsatellite markers and T. gondii was detected using 4 specific PCR-based markers: SAG1, SAG2, SAG3 and GRA6 directly from infected tissue. Of 126 wood mice collected, 44 samples were positive giving an infection rate of 34·92% (95% CI: 27·14–43·59%). Juvenile, young adults and adults were infected at a similar prevalence, respectively, 7/17 (41·18%), 27/65 (41·54%) and 10/44 (22·72%) with no significant age-prevalence effect (P = 0·23). Results of genetic analysis of the mice showed that the collection consists of 4 genetically distinct populations. There was a significant difference in T. gondii prevalence in the different genotypically derived mouse populations (P = 0·035) but not between geographically defined populations (P = 0·29). These data point to either a host genetic/family influence on parasite infection or to parasite vertical transmission.

Histomoniasis was transmitted to poults inoculated orally with recently harvested whole intact male worms in three trials (4/5, 5/6, 2/4), but not with female worms (0/5, 0/9, 0/3). When triturated male worms were given in two trials, the rate of transmission was reduced (3/5, 0/10). Triturated female worms given orally produced histomoniasis in 1/9 poults. These results suggest that further unknown steps may be involved in histomonad transmission by heterakid worms.

This study was partially supported by NSF Grant GB-5227.

An antiserum was raised in rabbits against a soluble extract of fresh homogenized adult Fasciola hepatica of rat origin and was then absorbed with rat and mouse tissue antigens. This antiserum reacted specifically with the surface coat of adult flukes, of both rat and mouse origin, by indirect immunofluorescence to show the detail of surface spines. When tested against juvenile stages recovered from mice the reaction was positive with all but the earliest hepatic parenchyma stages. No reaction was present on the tegumental surface of newly excysted juveniles or stages 1 or 2 days post-infection (p.i.) whether recovered from the peritoneal cavity or the hepatic parenchyma.

Information on the spatial pattern of African animal trypanosomosis forms a prerequisite for rational disease management, but few data exist for any country in the continent. The present study describes a raster or grid-based Geographic Information System for Togo, a country representative of subhumid West Africa, with data layers on tsetse, trypanosomosis, animal production, agriculture and land use. The paper shows how trypanosomosis prevalence and packed cell volume (PCV) map displays may be predicted from correlations between representative field data and environmental and satellite data acquired from the National Oceanographic and Atmospheric Administration (NOAA) and Meteosat platforms. Discriminant analytical methods were used to assess the relationship between the amount of field data used and the accuracy of the predictions obtained. The accuracy of satellite derived predictions decreases from tsetse abundance to trypanosomosis prevalence to PCV value. The predictions improve when eco-climatic and epidemiological predictors are combined. In Togo, and probably elsewhere, the patterns of trypanosomosis prevalence and PCV are much influenced by animal husbandry and other anthropogenic factors. Additional predictor variables, incorporating these influences might therefore further improve the models.

The investigation, of which the results contained in this paper are a part, was first commenced in 1910. It was then proposed to describe in some detail the entire anatomy of the adult insect, but when a measure of progress had been made, and the alimentary, tracheal, and nervous systems had been almost completed, the work was interrupted by my taking up an appointment in India. On returning to England in 1915, the enquiry was resumed for a short period at the end of the year, but early in 1916 it had to be abandoned again to meet the superior claims of entomological work with the Forces in Mesopotamia, for the War Office. This, and other investigations connected with problems which have arisen in England in consequence of the War, prevented any further progress being made, but, with the declaration of the Armistice it was felt that attention might once more be given to it. In the limited time which could be devoted to the work, it has not been possible to carry out the original plan of including the whole anatomy in one paper, and the description of the head and mouth parts has been selected because of the somewhat novel considerations which have arisen in connection with the latter, particularly with regard to the function of the labium during the operation of piercing, the publication of which it seemed undesirable to delav further.

Our preliminary observation, that sera from schistosomiasis patients react with carcinomas, raised the possibility of antigenic cross-reactivity. We here extend this observation to show that mice experimentally infected with Schistosoma mansoni react with human urothelial and transitional bladder carcinomas and also with a gastric carcinoma cell line, AGS. To identify cross-reacting epitopes, we looked for the expression of carcinoma markers in schistosome worms and eggs using monoclonal antibodies against tumour antigens MUC1, Tn and TF (also known as the oncofetal Thomsen-Friedenreich antigen or T antigen). Immunohistochemical staining showed that the TF-epitope is present in adult intravascular S. mansoni worms and eggs deposited in tissues of infected animals. The localization of TF-immuno-reactive material in schistosomes was seen at the parasite surface between male and female worms and around trapped eggs in the liver. This localization is consistent with the antigen being secreted. Mice experimentally infected with S. mansoni, developed circulating antibodies against the TF-epitope (identified as Gal(beta1-3) GalNAc-O-R) as seen in ELISA using TF-expressing asialoglycophorin (AGP) as antigen. The observed anti-TF response in S. mansoni-infected mice reflects the complexity of host-parasite interactions in this infection.

The cercaria of Parorchis acanthus swims by a series of spasmodic ventral flexions of the body moving with the dorsal surface of the body foremost. The wave of contraction continues along the tail which therefore moves dorso-ventrally. Creeping movements precede cyst formation. The structure of the tail is admirably suited to swimming movements and to rapid shortening and lengthening. The wall is provided with circular and longitudinal muscles and abundant mitochondria. The centre of the tail contains fluid in which is a network of large myoblasts the processes of which overlap and probably slide over one another during the tail movements. Glands opening into the terminal tail invagination secrete an adhesive substance consisting of mucoprotein and glycoprotein which together with the vesicular secretion around the aperture enables the tail tip to attach itself to the substratum.

I would like to express my sincere thanks to Dr I. ap Gwynn of this department for invaluable help in the preparation of the electron-micrographs and Mr R. A. Moore and Mr M. C. Bibby for technical assistance.

Trypanosoma bouffardi Leger & Blanchard, 1911, is described from naturally infected Lagonosticta s. senegala, Estrilda b. bengalus, Vidua chalybeata, Estrilda t. troglodytes and Amadina f. fasciata, all of which are new host records for Nigeria; Vidua chalybeata is a new host record for trypanosomes.

There was no significant morphological difference between populations of this trypanosome in the various natural and experimental vertebrate hosts.

T. bouffardi was transmissible to nine species of Ploceidae belonging to the three subfamilies Estrilinae, Ploceinae and Viduinae; but not to Pycnonotus barbatus, chickens or pigeons.

The parasitaemia produced by infections of T. bouffardi reached 4·1 × 105 parasites/mm3 of blood.

Reproduction of the trypanosomes was synchronous and discontinuous and occurred in the blood by unequal binary fission of trypomastigotes. Occasionally longitudinal equal binary fission of trypomastigotes also took place. There was no concentration of dividing forms in the tissues.

T. bouffardi did not grow on NNN medium although it has been grown for a short time on the medium described by Yesufu (1970).

In a paper entitled ‘Crithidia sp., parasitic in the alimentary tract of Cenaeus carnifex’ (Gibbs, 1942), an attempt was made to describe a flagellate found in the mid-gut, hind-gut and rectum of a plant-feeding insect which is common in the Cape Peninsula, South Africa. It was shown that leishmanial forms and bodies described as mould-spores were carried around attached to the flagella of leptomonads. It was also observed that, in some form, the parasite was resistant to desiccation, as nymphs became infected when allowed to feed on the dried dejecta of infected insects. Large, fast-moving leptomonads were described as being the only forms found in the mid-gut, while smaller leptomonads with the attached bodies, as well as crithidial forms, were found in the hind-gut. The rectum was not studied on account of the difficulty then experienced in removing it unruptured.

Age-stratified data on toxoplasma seroprevalence in pregnant women in Stockholm, Sweden for the years 1969, 1979 1987 provide the basis for an analysis of temporal patterns of Toxoplasma gondii infection, and estimation of the risk maternal toxoplasmosis, in this population. A catalytic infection model, in which the rate or force of infection is assumed to be a function of time (and not, as is more usual, age), was employed to describe the observed changes in levels toxoplasma seropositivity. A range of simple incidence functions (up to 3 parameters) were fitted using a method maximum likelihood. The data were significantly better described by a linear or an exponential decay in the rate of infection through time compared with a constant level. More complex incidence functions gave no better data description. Thus, whilst there is strong evidence for declining incidence in Stockholm over the past 4–5 decades, the data do not allow discrimination between different possibilities for the nature of this decline. Based on these modelling results, best estimates of the force of infection in 1987 acting on susceptible women are within the range 0 to 0·0045/susceptible/year (95% confidence limits), yielding a possible risk of maternal toxoplasmosis of between 0 and 2·7 cases/1000 pregnancies. These values are shown to be significantly lower than estimates based upon an assumption of temporal stability in toxoplasma incidence, which may be of practical significance to public health policy.

We studied the distribution of ectoparasite species (an ixodid tick, a chigger mite, 7 mesostigmate mites, 5 fleas and 3 lice) on bodies of 5 species of rodent hosts from the marshlands in Argentina to establish whether arthropod ectoparasites are segregated across body parts of the same host individual. We asked (a) whether an individual ectoparasite species prefers certain parts of the body of its host and, if yes, whether these preferences overlap among ectoparasite species; (b) whether ectoparasite species composition differs among different parts of a host's body; and (c) whether co-occurrences of ectoparasite species within pre-defined body parts of a host are non-random and, if yes, whether ectoparasites co-occur in the same body part of a host either less or more often than expected by chance. It was found that, in general, ectoparasite species were not segregated across body parts of a host. Although some ectoparasites preferred certain body parts, these preferences were similar among ectoparasites belonging to different species and/or higher taxa resulting in similarity among host body parts in ectoparasite species composition. In addition, ectoparasite species demonstrated a tendency to co-occur on the same body parts of a host and not to be segregated among them. It was concluded that the distribution of ectoparasites on the body of a small mammalian host is driven mainly by their interaction with the host rather than by distinct preferences or interactions among ectoparasite species.

Dogs serve as hosts for a great number of parasites, which may affect their health and wellbeing. This study aimed to observe tick borne pathogens in dogs from Palestine including Hepatozoon canis and Babesia species. The prevalence of both H. canis and Babesia species infections in apparently healthy dogs, from ten districts of the West Bank was surveyed. DNA was extracted from blood samples obtained from dogs (n = 362) and ticks (n = 213) collected from dogs (n = 77). A primer set that amplifies a partial sequence of the Babesia and Hepatozoon 18S rRNA gene was used for PCR and the DNA sequences of the PCR products of all samples were determined. Twenty-nine (8·0%) of the dogs were found infected including 20 with H. canis (5·5%), seven with Babesia vogeli (1·9%) and two with undefined Babesia spp. (0·6%). Twelve Rhipicephalus sanguineus s.l ticks were pathogen-positive, including ten with H. canis (4·7%), one with B. vogeli (0·5%), and one with Hepatozoon felis (0·5%). The results indicated that a wide range of tick borne pathogens is circulating in the canine population in the surveyed region. This study is the first report on the prevalence of H. canis, B. vogeli and Babesia spp. in dogs in Palestine and its results will assist in the management of diseases associated with these blood parasites.

Infection by a variety of species of intestinal nematode infection gives rise to a wide variation in parasite load within a host population. There has been much investigation into the basis of this variation and is thought to involve several factors. Studies of infections of gut dwelling nematodes in laboratory rodents has clearly demonstrated that this variation may be due to the production of cytokines produced as part of the host immune response to infection. More specifically, activation of distinct T helper cell subsets leads to the generation of effective or ineffective responses resulting in clearance of the parasite load or maintenance of chronic infection. The induction of differential responses remains to be determined but is likely to be influenced at a number of levels including involvement of accessory cells and activation of co-stimulatory molecules on antigen presenting cells. Moreover, it appears that these parasites may actively interfere with the host cytokine response to promote their own survival. This review concentrates on recent findings of cytokine mediated control of intestinal nematodes highlighting a central role for the immune system in regulating both acute and chronic infection by these parasites.

The ability of Trichomonas vaginalis to adhere to plastic surfaces in the presence of various agents and under different growth conditions was examined in wells of microtitre plates containing unsupplemented TYI medium or the same, with various supplements. Following incubation, the wells were thoroughly washed and adhesion was determined by microscopic counting of the adherent organisms. There was no detectable adhesion in the absence of both serum and carbohydrate. Optimal adhesion (about 10–20% of the total number of parasites) was obtained throughout the growth curve in culture media supplemented with either serum or serum Cohn fractions IV–I (rich in α-globulin) or IV-4 (rich in α + β-globulin) and 25 mM glucose, maltose or fructose, but not in plates pre-coated with the Cohn fractions. Cohn fraction II + III (rich in β + γ-globulin) moderately enhanced adhesion while Cohn fractions II (rich in γ-globulin) or V (albumin), fibronectin, Tamm-Horsfall glycoproteins and polylysine were without effect. Non-metabolizable sugars (methyl derivatives of glucose, mannose or fucose) did not support growth, but, surprisingly, enhanced adhesion. At 4 °C, the trichomonads were not able to adhere and pre-adherent organisms detached from the plastic surface. Optimal adhesion was obtained at a pH range of 6·5–7·5 but was already detectable at pH 5·5. Cytochalasin E markedly suppressed adhesion. The data taken together suggest that the firm, serum-dependent adhesion of T. vaginalis to plastic surfaces is apparently not influenced by the rate of multiplication, requires energy and the binding by the organisms of certain serum proteins, which possibly enhances their hydrophobic interaction with the plastic substratum.

We performed a systematic review and meta-analysis on the prevalence and factors associated with Schistosoma mansoni infection in Brazil. We searched the PubMed, Web of Science and Latin-American and Caribbean System on Health Sciences Information (LILACS) databases, scientific publications articles, according to The PRISMA Statement, from 2000 to 2016. A total of 27 studies were included according to the established criteria. The prevalence of S. mansoni infection varied widely, from 0·1 to 73·1%, based on Kato-Katz technique. Of the identified studies, 42·9% were performed in the state of Minas Gerais, and 33·3% were performed in the northeast region of Brazil. We identified sex, age, education level, family income, contact with water and the presence of the intermediate host snail as major risk factors associated with infection. The meta-analysis summarized a high prevalence rate pooled for Schistosoma mansoni. On the other hand, the analysis of the subgroup showed a highly significant reduction of the prevalence rate after control measures. The epidemiological factors evidenced in the studies show the influence of environmental and social conditions on the occurrence of schistosomiasis.

Refugia-based treatment strategies aim to prolong anthelmintic efficacy by maintaining a parasite population unexposed to anthelmintics. Targeted selective treatment (TST) achieves this by treating only animals that will benefit most from treatment, using a determinant criterion (DC). We developed a mathematical model to compare various traits proposed as DC, and investigate impacts of TST and drenching frequency on sheep performance and anthelmintic resistance. Short term, decreasing the proportion of animals drenched reduced benefits of anthelmintic treatment, assessed by empty body weight (EBW), but decreased the rate of anthelmintic resistance development; each consecutive drenching had a reduced impact on average EBW and an increased impact on the rate of anthelmintic resistance emergences. The optimal DC was fecal egg count, maintaining the highest average EBW when reducing the proportion of animals drenched. Long-term, reducing the proportion of animals drenched had little impact on total weight gain benefits, across animals and years, whilst reducing drenching frequency increased it. Decreasing the frequency and proportion of animals drenched were both predicted to increase the duration of anthelmintic efficacy but reduce the total number of drenches administered before resistance was observed. TST and frequency of drenching may lead to different benefits in the short versus long term.

In three series of infections 32 mice were given metacercarial cysts of Fasciola hepatica X-irradiated at 3 Kr.: 8 mice received 20 cysts each and 10 mice 40 cysts each. In serial kills 9–24 days after infection 127 young flukes were recovered, 10 + 49 entire and 39 + 29 in serial sections of infected liver. These flukes were stunted and inhibited in their development. During a period of 8–22 days the length and breadth of the flukes increased from 0·53 mm. x 0·27 mm. to 1·12 mm. x 0·37 mm., whereas the mean length and breadth of normal flukes 22 days old is 3·4 mm. x 1·9 mm. The intestines of the flukes have about 10–14 lateral diverticula or sacculations but not normal branches during this period. In the sections of 12– to 29–day infections 16 dead flukes were observed in various stages of disintegration but flukes deemed alive at the time of fixation were noted in all stages from 8 days onwards, although some of them were injured by inflammatory processes set up in the liver. Injury is caused by massive infiltrations into the inner substance of the cuticle of band-type neutrophil leucocytes, which raise the epicuticle in extensive blister-like formations, but the basal portion of the cuticle (lamina vitrea) remains more or less intact. The cuticular sheets ultimately fragment, apparently as a result of chemical action, and leucocytes which had infiltrated into the cuticle rejoin the aggregate of similar cells inside the burrow. How the leucocytes effect an entry into the cuticle is not clear, but it is more probably by chemical than by physical means. When the epicuticle has been destroyed the fluke is in a dying condition. Few leucocytes penetrate into the parenchyma, suggesting that the lamina vitrea is relatively resistant to these cells and that death is due to chemical action following widespread but superficial damage to the cuticle.

The remaining 14 mice which received 40 X-irradiated cysts each were challenged 22 days later with 10 or 5 normal cysts. This procedure was followed by serial kills at intervals during the period 8–53 days after infection. Three almost mature flukes were recovered at 32 days and one mature fluke at 39 days. The mature fluke was of unusually small size (6·4 mm. x 4·3 mm.), but it had shed many viable eggs into the bile duct and gall bladder. The numbers of flukes of the challenge infections did not differ significantly from those of normal controls: 62 flukes in groups of 1–8 per mouse provided means of 4·4 flukes per mouse and 55·4 flukes per 100 cysts. In similar experimental infections of mice (which, however, received 2 doses of cysts X-irradiated at 4 Kr.) Hughes (1963) recovered 39 flukes in groups of 1–7 per mouse, providing means of 3·5 flukes per mouse and 35·3 flukes per 100 cysts. In his control experiments, which also serve as the writer's controls, 10 mice received 10 normal cysts each and in 22– to 29–day infections 34 flukes were recovered in groups of 3–5 per mouse, providing means of 4·25 flukes per mouse and 42·5 flukes per 100 cysts. There is therefore no evidence of immunity in terms of either delayed maturation or reduced fluke burdens. At all stages of infection flukes of the challenge infection bear comparison with flukes of single normal infections, except for an apparent diminution of growth (which requires confirmation) about 3–4 weeks after infection. This accords with generally accepted opinion that any small degree of immunity which is acquired by the hosts of liver flukes is almost undemonstrable. Further experiments with reduced periods between infections with X-irradiated cysts and a challenge infection may be profitable and are in progress but it is suggested that in such experiments nutritional effects may arise as a result of modification of the hepatic tissue on which young flukes feed by leucocytic infiltrations of the inflammatory reaction which is normally directed towards the repair of damage caused by the flukes.

My former pupil Denys H. Hughes, of the Parasitology Group, Allen and Hanburys (Ware), kindly set up the experimental mice to my specifications and I am deeply grateful to him for this kindness and consideration and for the respect he has shown for my wishes. Mice and cysts—X-irradiated as required— were supplied by Allen and Hanburys, for which my thanks are also proffered.

My personal technician, Mr John Wells, has attended to my technical needs constantly. In addition to making numerous series of excellent sections and whole mounts, he undertook the task of measuring several dimensions of more than 100 flukes. His patience and perseverance in the face of continual requests for more and more, good and still better materials has been commendable and I am glad to express my gratitude to him. I am grateful also to Mr R. D. Reed of this Department, who prepared the photomicrographs for Pls. 1–4 of this paper, sometimes when under the pressure of other duties.