The development of the epidermis of the oncomiracidium larva of Entobdella soleae was studied in embryos dissected from the egg and processed for electron microscopy. At first (7- to 8-day embryos at 15 °C) the embryo is covered with a nucleated primary epidermis of flattened cells which are closely associated with the viteUine cells and may take up nutrients from them. This layer is either replaced by or develops into the secondary epidermis which consists of ciliated cellular regions joined by an apparently syncytial interciliary cytoplasmic layer. Both ciliated cells and interciliary cytoplasm are at first nucleated but later both lose their nuclei. There may be a turnover of ciliated epidermal cells at the surface of young embryos. Between days 16–20 a discontinuous presumptive adult epidermis appears beneath the ciliated cells which has connexions to cell bodies lying in the parenchyma. This layer, apparently fuses with the syncytial (?) interciliary regions which have by this time lost their nuclei. After shedding of the ciliated cells, the presumptive adult epidermis spreads out to form a continuous syncytial covering to the post-larva. The ciliated epidermal cells apparently lose their nuclei between days 20 and hatching. This may be associated with the ‘programmed life’ of the ciliated cells. Details of the food reserves and morphology of the ciliated cells are discussed in connexion with the energetics of these cells.

The results of an epidemiological study involving the estimation of worm counts of gastro-intestinal nematodes of lambs, during the period December 1978 to November 1979, in the Baghdad area are reported. Ostertagia spp. and Trichostrongylus spp. were the most abundant nematodes in the weaned lambs used in this study. Ostertagia spp. infection was present throughout the period of observation, the level of infection being the highest during early summer (May–June). Trichostrongylus spp. infection, however, reached a peak during July–August. In the tracer lambs the maximum population of Ostertagia spp. was found during February–March, while that of Trichostrongylus spp. could be observed only after mid-June. Other nematodes encountered were Haemonchus contortus and Trichuris sp. but they were only present in small numbers. The proportion of inhibited larvae of Ostertagia spp. was markedly high during the dry summer months. Little inhibition was noticed during autumn and the early winter months. It appears that if the seasonal inhibition of Ostertagia spp. in Iraq is brought about by an environmental stimulus acting upon pre-parasitic larval stages, that stimulus cannot be chilling or falling temperatures, as observed in temperate northern zones.

Transmission of cercariae of the echinostome digenean Echinoparyphium recurvatum was observed in experimental populations of the second intermediate host snail Lymnaea peregra. Populations of 100 snails were distributed among plastic mesh cages in an infection arena to produce different patterns of host dispersion. Cercarial transmission was investigated in host populations showing three separate patterns of host dispersion; Ideal Regular, Random and Contagious (‘Clumped’). Levels of cercarial transmission in populations showing each type of dispersion pattern were found to be significantly different. The highest rate of cercarial transmission occurred in the contagiously dispersed host population, and the lowest in the randomly dispersed population. Analysis of results from the randomly dispersed population also showed that both the mean percentage prevalence of infection, and also the mean number of cysts recovered per snail, increased significantly with the number of snails per cage. The positive relationship between the mean number of cysts per snail and the number of snails per cage was found to be best described by an exponential function. Chemosensory location of L. peregra snail hosts by E. recurvatum cercariae may provide an explanation for the patterns of cercarial transmission observed.

It has been shown in an earlier paper that if the eggs of parasites are not deposited in unparasitised hosts alone, but distributed according to the laws of chance among unparasitised hosts and hosts already attacked by individuals of the same species, and if all the parasites develop successfully, no matter how many enter a single host, then the effect upon the time required for the extermination of the host, as compared to that which is required if only unparasitised hosts are chosen, is relatively slight.

The hypothesis examined in this paper is that when several parasites enter a single host, one, and only one, will develop successfully. It is shown that in such a case, provided the reproductive rate is decidedly greater than that of the host (e.g. 1·5 times as great), the effect on the time required for the extermination of the host by the parasite will be very little if at all greater than when superparasitism causes merely a loss in efficiency, as in the hypothesis previously examined. When the reproductive rate of the host is practically or actually equal to that of the parasite, the process of control will be seriously retarded, the delay being very much greater than in the preceding hypothesis. Control will, however, occur, even in this case.

Superparasitism of the type here examined will therefore not necessarily produce any marked retardation of the process of control in cases where control within reasonable time would otherwise be probable.

The effect of the intestinal changes brought about by the expulsion of Trichinella spiralis in rats was studied in relation to the growth and survival of a concurrent infection with Hymenolepis diminuta, a cestode not normally rejected by the rat in low-level infections. Growth of H. diminuta was stunted in rats given T. spiralis just before, or after, infection with H. diminuta, the stunting being more pronounced when the cestode was given closer to the period of inflammation. There was no loss of the cestode from dual-infected rats and no evidence for destrobilation was found. Lower T. spiralis burdens had a correspondingly weaker effect on growth of H. diminuta, and stunting was abolished by administration of the anti-inflammatory drug cortisone acetate. It is concluded that the stunting of H. diminuta is probably due to the non-specific inflammatory component of the rat's response to T. spiralis infection.

In the skin of Rana temporaria from Czechoslovakia two unicellular parasites have been found: Dermocystidium ranae Guyénot & Naville and Dermosporidium granulosum n.sp.

Dermocystidium ranae. Two stages were found, one of which is new. An account is given of the morphology, development and occurrence of both stages, including details which have hitherto not been recorded.

Dermosporidium granulosum n.sp. This species is represented by cysts situated in the stratum spongiosum corii. They are divided by septa into small chambers containing groups of spherical spores with a central nucleus and with numerous small cytoplasmic inclusions. Within the cyst, the sporoblasts occupy the periphery, while the ripe spores are in the centre.

Larval nematodes occurring in cysts in the body musculature of Icelandic cod have been identified as belonging to Porrocaecum Raillet & Henry, 1912 (subgenus Terranova Leiper & Atkinson, 1914), probably P. decipiens Krabbe and Anisakis Dujardin, 1845. Identification was made possible by rearing them in vitro to the pre-adult condition. The experiments show that the following conditions are necessary for the moult to the pre-adult state; (1) a fairly high culture temperature (37° C.); (2) the presence of pieces of fish for 24 hr. towards the beginning of the culture period. 1 % pepsin, while it assists the hatching from the cysts, is not essential for the moult to the pre-adult condition. Experiments indicate that the moult takes place 3–5 days after fish has been supplied.

The larvae and pre-adults of both genera are described. Samples of larvae from cod from Greenland and the Barents Sea probably consist only of Porrocaecum and Anisakis, but a sample from West Scotland contained only Porrocaecum. The significance of the moult to the pre-adult state is discussed.

Observations have been made on the hatching behaviour of the larva of the monogenean Entobdella soleae and on the effects of various enzymes on the opercular cement of the egg. These observations indicate that hatching is brought about by a proteolytic hatching fluid which is produced by two pairs of ventral head glands and spread over the inner surface of the opercular joint by rotation of the larva about its longitudinal axis. After hatching there is no trace of the ventral head glands. Similar glands are present before hatching in the oncomiracidium of E. hippoglossi.

The hind-body region of Schistosoma mansoni cercariae observed in the scanning electron microscope demonstrates various stages of contraction which may be compared with those of living larvae which are secreting the acetabular gland contents.

No evidence for an extensive lesion was found in cercarial bodies which had shed their tails under experimental conditions. Experiments on the permeability of the larvae to sodium fluoride, methylene blue and amino acids demonstrated that tail loss significantly affects the permeability of the bodies although the effect is greater immediately after decaudation than at later times. Subsequent increases in permeability may be correlated with a change in the general body surface.

A Ciliate, which seems to be new, has recently been discovered in the caecum of cattle in Cambridge. Out of 8 cattle examined 5 were found to be heavily infected, while in 10 sheep and 4 goats there was no infection. I have given the name Buxtonella to the new genus that has had to be established, as it was through the kindness of Prof. Buxton, Director of this Institute, that I obtained the material in which it was first found. The specific name refers to the grooved ridge or furrow which forms the most conspicuous feature of this species.

Varroa destructor mites (Acari: Varroidae) are harmful ectoparasites of Apis mellifera honey bees. Female foundresses of wax-capped pupal host cells and their daughters feed on host fluids from open wounds on the host's integument. Details of V. destructor mite nutrition are forthcoming, and little is known about the potential physical effects on hosts from mite feeding. Chemical analysis of waste excretions can infer details of animals’ nutrition. Here, chemical analysis by high-performance liquid chromatography/mass spectrometry (HPLC-MS/MS) of mite excretions showed that the purine content of V. destructor waste consists of guanine with traces of hypoxanthine. Traces of uric acid and caffeine were also detected. Concentrations of guanine attenuated over time and excretions collected from senescing mites did not contain detectable guanine. Non-reproducing individual female mites maintained in vitro, housed in gelatin capsules and provided a honey bee pupa, deposited an average of nearly 18 excretions daily, mostly on the host's integument rather than on the capsule wall. The weight and volume of excretions suggest mites can consume nearly a microlitre of host fluids each day. Compounded over 10 days, this together with open wounds, could lead to substantial water loss and stress to developing pupae.

The first UK epizootic of highly pathogenic (HP) H5N1 influenza in wild birds occurred in 2008, in a population of mute swans that had been the subject of ornithological study for decades. Here we use an innovative combination of ornithological, phylogenetic and immunological approaches to investigate the ecology and age structure of HP H5N1 in nature. We screened samples from swans and waterbirds using PCR and sequenced HP H5N1-positive samples. The outbreak's origin was investigated by linking bird count data with a molecular clock analysis of sampled virus sequences. We used ringing records to reconstruct the age-structure of outbreak mortality, and we estimated the age distribution of prior exposure to avian influenza. Outbreak mortality was low and all HP H5N1-positive mute swans in the affected population were <3 years old. Only the youngest age classes contained an appreciable number of individuals with no detectable antibody responses to viral nucleoprotein. Phylogenetic analysis indicated that the outbreak strain circulated locally for ∼1 month before detection and arrived when the immigration rate of migrant waterbirds was highest. Our data are consistent with the hypothesis that HP H5N1 epizootics in wild swans exhibit limited mortality due to immune protection arising from previous exposure. Our study population may represent a valuable resource for investigating the natural ecology and epidemiology of avian influenza.

Objective. Glycogen synthase kinase 3 (GSK-3) is a promising target for the treatment of various human diseases such as type 2 diabetes, Alzheimer's disease and inflammation. Successful inhibition of the homologues of this kinase in Plasmodium falciparum, Trypanosoma brucei and Leishmania donovani makes the kinase an attractive target for the treatment of malaria, trypanosomiasis and leishmaniasis, respectively. The aim of this work was to compare the binding sites of the GSK-3 kinases of different parasites and to analyse them as possible targets for therapeutic compounds. Methods. Both a sequence alignment and homology models of the structure of 21 different GSK-3 homologues belonging to mammals, insects, pathogenic fungi, nematodes, trematodes and protozoa have been analysed, 17 of them being studied for the first time. Results. The structure of the kinases and, in particular, their binding sites, were found to be rather conserved, possessing small insertions or deletions and conserved amino acid substitutions. Nevertheless, the kinases of most species of parasite did have some amino acid differences from the human kinase, which could be exploited for the design of selective drugs. Conclusion. Comparison of the human and parasite GSK-3 ATP binding site models has shown that the development of selective drugs affecting parasite GSK-3 is possible. Known inhibitors of human GSK-3 can also be used as starting scaffolds for the search for drugs acting against parasitic diseases.

This study explored whether the yard environment and child hygiene and play behaviours were associated with presence and intensity of Ascaris and hookworm in preschool children and with eggs and larvae in soil. Data were collected using questionnaires, a visual survey of the yard, soil samples and fecal samples collected at baseline and following re-infection. The presence of eggs/larvae in soil was associated negatively with water storage (eggs) but positively with dogs (eggs) and distance from home to latrine (larvae). Baseline and re-infection prevalences were: hookworm (28·0%, 3·4%); Ascaris (16·9%, 9·5%); Trichuris (0·9%, 0·7%). Zero-inflated negative binomial regression models revealed a higher baseline hookworm infection if yards had eggs or larvae, more vegetation or garbage, and if the child played with soil. Baseline Ascaris was associated with dirt floor, dogs, exposed soil in yard, open defecation and with less time playing outdoors, whereas Ascaris re-infection was associated with water storage, vegetation cover and garbage near the home and not playing with animals. Our results show complex interactions between infection, the yard environment and child behaviours, and indicate that transmission would be reduced if latrines were closer to the home, and if open defecation and water spillage were reduced.

African animal trypanosomiasis (AAT) affects the livestock of 12.3 million Somalis and constrains their development and wellbeing. There is missing data on AAT in the country after the civil war of the 1990s. Therefore, this study has aimed to assess the prevalence of Trypanosoma spp. in 614 blood samples from cattle (n = 202), goats (n = 206) and sheep (n = 206) in Afgoye and Jowhar districts, Somalia using parasitological and molecular methods. Twenty-one out of 614 (3.4%; 95% CI: 2.1–5.2%) and 101/614 (16.4%; 95% CI: 13.6–19.6%) ruminants were positive for Trypanosoma spp. by buffy coat technique (BCT) and internal transcribed spacer 1 (ITS1)-polymerase chain reaction (PCR), respectively. Using ITS1-PCR, the highest prevalence was observed in cattle (23.8%; 95% CI: 18.4–30.1%) followed by goats (17.5%; 95% CI: 12.9–23.3%) and sheep (8.3%; 95% CI: 5.1–12.9%). A total of 74/101 (73.3%; 95% CI: 63.5–81.6%) ruminants were shown coinfection with at least two Trypanosome species. The four T. brucei-positive samples have tested negative for T. b. rhodesiense, by the human-serum-resistance-associated-PCR. Trypanosoma evansi, T. godfreyi, T. vivax, T. brucei, T. simiae and T. congolense were the Trypanosoma species found in this study. This is the first study on the molecular detection of Trypanosoma sp. in ruminants in Somalia. Further investigations and control measures are needed to manage Trypanosomiasis spreading in the country. Studies should also focus on the detection of T. b. rhodesiense in the country.

To improve the diagnosis of human fascioliasis caused by Fasciola gigantica, we developed a peptide-based enzyme-linked immunosorbent assay (peptide-based ELISA) based on the detection of specific IgG4 subclass antibody. Two identified B-cell epitopes of F. gigantica cathepsin L1 were synthesized as single synthetic peptides, acetyl-DKIDWRESGYVTELKDQGNC-carboxamide (peptide L) and acetyl-DKIDWRESGYVTEVKDQGNC-carboxamide (peptide V), and their diagnostic potential was evaluated. The sera of 25 patients infected with F. gigantica, 212 patients with other parasitic infections, 32 cholangiocarcinoma patients and 57 healthy controls were analysed. The sensitivity, specificity, accuracy, and positive and negative predictive values of this assay were the same with both peptides at 100%, 99·7%, 99·7%, 96·2% and 100%, respectively. These highly sensitive and specific peptide-based ELISAs for the detection of specific IgG4 antibody could be useful for laboratory diagnosis of human fascioliasis in future large-scale surveys throughout Southeast Asia where this disease is prevalent.

A consideration of the facts presented in the foregoing pages appears to warrant certain conclusions which must, however, be regarded in part as provisional and subject to revision when our knowledge of the various species of ticks has become more extended. The views here expressed may prove of practical use in the study of the Ixodidae.

The Argasidae represent the relatively primitive type of ticks because they are less constantly parasitic than are the Ixodidae. Their nymphs and adults are rapid feeders and chiefly infest the habitat of their hosts. In certain Argasidae (O. moubata and O. savignyi) the disadvantage of their possessing an “active” larval stage has resulted in the development of an “inactive” larva, i.e. the young nymph being the first to suck blood. In O. megnini we have a considerable adaptation brought about by the difficulty there must be in the tick entering the small aperture of the ear more than once. Owing to the Argasidae infesting the habitats of their hosts, their resistance to prolonged starvation and their rapid feeding habits, they do not need to bring forth a large progeny, because there is less loss of life in the various stages, as compared to Ixodidae, prior to their attaining maturity.

The Ixodidae are more highly specialized parasites than the preceding. The majority are parasitic on hosts having no fixed habitat and consequently all stages, as a rule, occur upon the host. In the genus Ixodes we find an adaptation of certain species according to the habits of the hosts upon which they are parasitic. In the species which usually occur upon wandering hosts both sexes are found upon the host, whereas in other species which occur on hosts possessing more or less fixed habitats the males are rarely or never found upon the host. The males of species of Ixodes, both sexes of which occur upon the host, are characterized, as a rule, by the possession of hypostomes with prominent teeth, the reverse being the case in forms wherein the males do not occur upon the host. Where species occur upon a wandering host it is essential, for their propagation in nature, that both sexes should be carried about upon the host.

Procyclic forms of Trypanosoma brucei brucei remain and propagate in the midgut of tsetse fly where iron is rich. Additional iron is also required for their growth in in vitro culture. However, little is known about the genes involved in iron metabolism and the mechanism of iron utilization in procyclic-form cells. Therefore, we surveyed the genes involved in iron metabolism in the T. b. brucei genome sequence database. We found a potential homologue of vacuole protein sorting 41 (VPS41), a gene that is required for high-affinity iron transport in Saccharomyces cerevisiae and cloned the full-length gene (TbVPS41). Complementation analysis of TbVPS41 in ΔScvps41 yeast cells showed that TbVPS41 could partially suppress the inability of ΔScvps41 yeast cells to grow on low-iron medium, but it could not suppress the fragmented vacuole phenotype. Further RNA interference (RNAi)-mediated gene knock-down in procyclic-form cells resulted in a significant reduction of growth in low-iron medium; however, no change in growth was observed in normal culture medium. Transmission electron microscopy showed that RNAi caused T. b. brucei cells to have larger numbers of small intracellular vesicles, similar to the fragmented vacuoles observed in ΔScvps41 yeast cells. The present study demonstrates that TbVPS41 plays an important role in the intracellular iron utilization system as well as in the maintenance of normal cellular morphology.

Monte Carlo simulations were developed to assess the potential impact of parasite pathology on vector salivary function as well as of host haemostasis on transmission. Assuming that a proportion of desisting vectors switch host following failure to locate blood, we demonstrate three possible consequences: (1) infected vectors contact more hosts than non-infected hosts, (2) non-infected vectors are biased to infected hosts, independently of attraction, and (3) an exponential relationship exists between parasite load and transmission. We discuss possible epidemiological implications.

We evaluated the effect of chemotherapy with a sequential combined treatment of a low dose of benznidazole and allopurinol, in different schedules of administration, in experimental models of acute and chronic Trypanosoma cruzi infection. Mice were infected with Nicaragua T. cruzi isolate, a virulent parasite from an endemic area of Nicaragua, genotyped as TcI (Grosso et al. 2010). We assessed survival rate, IgG levels, histopathological studies and quantified parasitaemia. A 15% survival rate was recorded in untreated mice during the acute phase of T. cruzi infection. Allopurinol administered immediately after benznidazole treatment was able to reduce parasitaemia and attenuate tissue damage by reducing inflammation. Trypanosoma cruzi-specific antibodies also decreased in 40–50% of the treated mice. The addition of allopurinol during the chronic phase showed the highest beneficial effect, not only by reducing parasitaemia but also by lowering the degree of inflammation and fibrosis.