Small marine snails and abalone have been identified as high- and low-risk prey items, respectively, for exposure of threatened southern sea otters to Toxoplasma gondii, a zoonotic parasite that can cause fatal encephalitis in animals and humans. While recent work has characterized snails as paratenic hosts for T. gondii, the ability of abalone to vector the parasite has not been evaluated. To further elucidate why abalone predation may be protective against T. gondii exposure, this study aimed to determine whether: (1) abalone are physiologically capable of acquiring T. gondii; and (2) abalone and snails differ in their ability to concentrate and retain the parasite. Abalone were exposed to T. gondii surrogate microspheres for 24 h, and fecal samples were examined for 2 weeks following exposure. Concentration of surrogates was 2–3 orders of magnitude greater in abalone feces than in the spiked seawater, and excretion of surrogates continued for 14 days post-exposure. These results indicate that, physiologically, abalone and snails can equally vector T. gondii as paratenic hosts. Reduced risk of T. gondii infection in abalone-specializing otters may therefore result from abalone's high nutritional value, which implies otters must consume fewer animals to meet their caloric needs.

The study of priority effects with respect to coinfections is still in its infancy. Moreover, existing coinfection studies typically focus on infection outcomes associated with exposure to distinct sets of parasite species, despite that functionally and morphologically similar parasite species commonly coexist in nature. Therefore, it is important to understand how interactions between similar parasites influence infection outcomes. Surveys at seven ponds in northwest Pennsylvania found that multiple species of echinostomes commonly co-occur. Using a larval anuran host (Rana pipiens) and the two most commonly identified echinostome species from our field surveys (Echinostoma trivolvis and Echinoparyphium lineage 3), we examined how species composition and timing of exposure affect patterns of infection. When tadpoles were exposed to both parasites simultaneously, infection loads were higher than when exposed to Echinoparyphium alone but similar to being exposed to Echinostoma alone. When tadpoles were sequentially exposed to the parasite species, tadpoles first exposed to Echinoparyphium had 23% lower infection loads than tadpoles first exposed to Echinostoma. These findings demonstrate that exposure timing and order, even with similar parasites, can influence coinfection outcomes, and emphasize the importance of using molecular methods to identify parasites for ecological studies.

Orca (Orcinus orca) strandings are rare and post-mortem examinations on fresh individuals are scarce. Thus, little is known about their parasitological fauna, prevalence of infections, associated pathology and the impact on their health. During post-mortem examinations of two male neonatal orcas stranded in Germany and Norway, lungworm infections were found within the bronchi of both individuals. The nematodes were identified as Halocercus sp. (Pseudaliidae), which have been described in the respiratory tract of multiple odontocete species, but not yet in orcas. The life cycle and transmission pathways of some pseudaliid nematodes are incompletely understood. Lungworm infections in neonatal cetaceans are an unusual finding and thus seem to be an indicator for direct mother-to-calf transmission (transplacental or transmammary) of Halocercus sp. nematodes in orcas.

Leishmania rely heavily on glycans to complete their digenetic life cycle in both mammalian and phlebotomine sand fly hosts. Leishmania promastigotes secrete a proteophosphoglycan-rich gel (Promastigote Secretory Gel, PSG) that is regurgitated during transmission and can exacerbate infection in the skin. Here we explored the role of PSG from natural Leishmania-sand fly vector combinations by obtaining PSG from Leishmania (L.) major-infected Phlebotomus (P.) papatasi and P. duboscqi and L. tropica-infected P. arabicus. We found that, in addition to the vector's saliva, the PSG from L. major and L. tropica potently exacerbated cutaneous infection in BALB/c mice, improved the probability of developing a patent cutaneous lesion, parasite growth and the evolution of the lesion. Of note, the presence of PSG in the inoculum more than halved the prepatent period of cutaneous L. tropica infection from an average of 32 weeks to 13 weeks. In addition, L. major and L. tropica PSG extracted from the permissive experimental vector, Lutzomyia (Lu.) longipalpis, also exacerbated infections in mice. These results reinforce and extend the hypothesis that PSG is an important and evolutionarily conserved component of Leishmania infection that can be used to facilitate experimental infection for drug and vaccine screening.

Great Island Virus (GIV) is an arbovirus present in the tick Ixodes uriae, a common ectoparasite of nesting seabirds. Common guillemot (Uria aalge) and black-legged kittiwake (Rissa tridactyla) are the preferred and most abundant hosts of I. uriae on the Isle of May, Scotland. As part of a study to understand the epidemiology of GIV, the ability of guillemot and kittiwake to support tick-borne transmission of GIV was examined. GIV was present in ticks feeding in isolated guillemot colonies and guillemots had virus-specific neutralizing antibodies demonstrating previous GIV infection. By contrast, only uninfected ticks were found in colonies inhabited solely by kittiwakes. GIV was isolated from kittiwake ticks in colonies which also contained breeding guillemots but no virus-specific neutralizing antibodies were present in blood samples of kittiwake on which infected ticks were feeding. Thus guillemots are the main vertebrate hosts of GIV on the Isle of May whereas kittiwakes do not appear to be susceptible to infection. Virus infection of adult ticks feeding on guillemots was highly efficient and may involve both viraemic transmission and transmission from infected to uninfected ticks feeding together on birds that do not develop a patent viraemia.

Green fluorescent protein (GFP)-parasite transfectants have been widely used as a tool for studying disease pathogenesis in several protozoan models and their application in drug screening assays has increased rapidly. In the past decade, the expression of GFP has been established in several Leishmania species, mostly for in vitro studies. The current work reports generation of four transgenic parasites constitutively expressing GFP (Leishmania mexicana, Leishmania aethiopica, Leishmania tropica and Leishmania major) and their validation as a representative model of infection. This is the first report where stable expression of GFP has been achieved in L. aethiopica and L. tropica. Integration of GFP was accomplished through homologous recombination of the expression construct, pRib1.2αNEOαGFP downstream of the 18S rRNA promoter in all species. A homogeneous and high level expression of GFP was detected in both the promastigote and the intracellular amastigote stages. All transgenic species showed the same growth pattern, ability to infect mammalian host cells and sensitivity to reference drugs as their wild type counterparts. All four transgenic Leishmania are confirmed as models for in vitro and possibly in vivo infections and represent an ideal tool for medium throughput testing of compound libraries.

Parasites typically have low reproductive fitness on paratenic hosts. Such hosts offer other significant inclusive fitness benefits to parasites, however, such as increased mobility and migration potential. The parasite fauna of the guppy (Poecilia reticulata) is dominated by the directly transmitted ectoparasites Gyrodactylus bullatarudis and Gyrodactylus turnbulli. In the wild, close predatory and competitive interactions occur between the guppy and the killifish Rivulus hartii. Previous observations suggest that these fish can share gyrodactylids, so we tested experimentally whether these parasites can use R. hartii as an alternative host. In aquaria, G. bullatarudis was the only species able to transmit from prey to predator. Both parasite species transferred equally well to prey when the predator was experimentally infected. However, in semi-natural conditions, G. bullatarudis transmitted more successfully to the prey fish. Importantly, G. bullatarudis also survived significantly longer on R. hartii out of water. As R. hartii can migrate overland between isolated guppy populations, G. bullatarudis may have an enhanced ability to disperse and colonize new host populations, consistent with its wider distribution in the wild. To our knowledge, this is the first empirical study demonstrating a predator acting as a paratenic host for the parasites of its prey.

We studied the structure of chigger mite (Trombiculidae) communities parasitic on a South African rodent, Rhabdomys pumilio. We aimed to determine whether: (a) different chigger species differ in preferences for certain body areas of a host and (b) chigger assemblages among body areas of the same host individual, are structured and if so, whether the structure of these assemblages is aggregative or segregative. Rhabdomys pumilio is parasitized by seven chigger species belonging to six genera. The three most abundant species (Leptotrombidium sp. nr. muridium, Schoutedenichia sp. and Neoschoengastia sp. A) displayed a non-random distribution across the host body, with the two most abundant species (L. sp. nr. muridium and Schoutedenichia sp.) significantly associated with the tail area. In addition, whenever non-randomness of chigger co-occurrence in the same body area was recorded, it indicated positive but not negative co-occurrences of different species. This might be due to similarity of chigger species in resource needs and strategies to avoid host defence efforts.

At a temperature of 27°C the external cuticular membrane of the first larval stage (L1) of Meloidogyne javanica is formed within a day of the start of elongation of the embryo within the egg. The first and only moult within the egg starts to occur 50 h after the commencement of elongation. Thus the cuticle of the L1 is shed approximately a day after its formation. It is much thinner than the cuticle of the L2, is not covered during its formation by a closely adherent cuticle in the process of being moulted and its outermost membrane may be formed differently.

During the past few months we have collected a considerable amount of information relating to the value of pH. as affecting the distribution of the three species of Limnaea commonly found in North Wales. Tables I and II show that L. truncatula occurs over a range of pH. 6·0 to 8·6, and L. peregra 5·8 to 8·8; L. palustris was recorded from 7·4 to 8·0 (but only three of the readings included this species).

It has been demonstrated that Hymenolepis microstoma in mice treated with cortisone grow larger than those in control mice.

The possibility of this being an immunosuppressive or growth-stimulating effect is discussed since the results from two strains of mice are different.

Antibody production is suppressed in the cortisone-treated animals and it is suggested that the circulating antibody normally affects a partial rejection of the worm.

I am grateful to Professor C. A. Hopkins and Dr T. S. C. Orr for many helpful comments during the course of this work and especially to Professor C. A. Hopkins for the facilities which he has placed at my disposal. Many thanks also to Miss Gillian Moore and Mr Jack Keys for their expert technical assistance. This work was in part supported by a grant from Fisons Pharmaceuticals Ltd.

Despite intensive research during the last few decades, understanding of ecological and physiological factors related to haemosporidian infections in birds is still fragmentary. Since more model organisms are needed in order to understand these infections in the wild, we analysed avian haemosporidian infections in the rufous-collared sparrow (Zonotrichia capensis, Emberizidae) in a dry forest of the Ecuadorian Andes. Parasite diversity was screened using molecular and morphological approaches. By molecular diagnosis, we identified three linages that were phylogenetically placed in the context of molecular haemosporidian diversity and associated with a morphospecies. By microscopy, we identified five described morphospecies and one additional undescribed morphospecies. We found that avian haemosporidian prevalence on the study site was 76.3%. Additionally, we used a series of generalized linear models to explore the potential relationship of parasite prevalence and parasitaemia with a set of variables related to physiological and environmental conditions. Although our results revealed associations of haemosporidian infections with precipitation, age and sampling site, the models only explained a small fraction of the variation.

Artemisinin-based combination therapy is exerting novel selective pressure upon populations of Plasmodium falciparum across Africa. Levels of resistance to non-artemisinin partner drugs differ among parasite populations, and so the artemisinins are not uniformly protected from developing resistance, already present in South East Asia. Here, we consider strategies for prolonging the period of high level efficacy of combination therapy for two particular endemicities common in Africa. Under high intensity transmission, two alternating first-line combinations, ideally with antagonistic selective effects on the parasite genome, are advocated for paediatric malaria cases. This leaves second-line and other therapies for adult cases, and for intermittent preventive therapy. The drug portfolio would be selected to protect the ‘premier’ combination regimen from selection for resistance, while maximising impact on severe disease and mortality in children. In endemic areas subject to low, seasonal transmission of Plasmodium falciparum, such a strategy may deliver little benefit, as children represent a minority of cases. Nevertheless, the deployment of other drug-based interventions in low transmission and highly seasonal areas, such as mass drug administration aimed to interrupt malaria transmission, or intermittent preventive therapy, does provide an opportunity to diversify drug pressure. We thus propose an integrated approach to drug deployment, which minimises direct selective pressure on parasite populations from any one drug component. This approach is suitable for qualitatively and quantitatively different burdens of malaria, and should be supported by a programme of routine surveillance for emerging resistance.

A decline in serum thyroxine (T4) occurs in Nya[ratio ]NYLAR female mice infected with Toxoplasma gondii. To ascertain whether the hypothyroxinaemia might be the result of primary thyroid dysfunction, 2 parameters of thyrofollicular cell function were monitored to determine (a) if the cell surface membrane receptors for thyroid-stimulating hormone (TSH) were operative, and (b) whether the cyclic adenosine monophosphate (cAMP)-dependent cascade of intracellular events leading to the release of T4 was responsive to exogenous cAMP. Our results indicated that both parameters were intact and functional in the infected-mouse thyrocytes. However, the elicited T4 responses were distinctly diminished in magnitude, reflecting a lack of readily available thyroidal T4 reserves. Because the continuing synthesis, storage, and release of T4 is dependent on the pulsatile stimulation of the thyroid by TSH, we suggest that the depletion of T4 reserves is likely due to perturbation of the pulsatile release of TSH from the pituitary, rather than to primary thyroid malfunction.

The host–parasite relationship of the Chinese mainland strain of Schistosoma japonicum in CBA mice is described and compared to previous reports on this parasite in mice. S. japonicum took under 2 weeks to complete its migration to the portal system of mice, and peak passage of schistosomula through the lungs occurred 5–6 days after infection. The mean percentage establishment of worms, which was independent of the infecting inoculum, was 46%. The adult worm burdens remained constant over a 28-week period of infection. Male and female worms reached maximum mean lengths of 13 and 19 mm, respectively. Egg laying commenced 30 days after infection. The number of ova deposited in the liver stabilized at some 55000 by 12 weeks of infection with 30 cercariae, but the intestinal egg burden rose from 132000 at 12 weeks to 430000 at 28 weeks. Faecal eggs were first observed 6 weeks after mice were exposed to 100 cercariae and 7 weeks after lighter exposures. Faecal egg output also stabilized 12 weeks after infection. The formation of granulomas in the liver occurred within 2 weeks of egg deposition and encompassed a maximum area 14 weeks after infection. Fifty per cent mortality occurred 15 weeks after exposure, but only in hosts infected with 100 cercariae.

The large and small forms of Tylenchorhynchus macrurus are distinguished as separate species. The large form becomes T. icarus and differs from the small form, T. macrurus in the greater number of annules on the female tail, longer stylet and slimmer body. The oxygen consumption of both species is similar when assessed in terms of body surface area. Soil samples from the field indicated that (a) greatest concentrations of T. icarus occurred at about 5 cm. depth, (b) few occurred below 24 cm., the depth of the top soil, and (c) numbers of T. icarus in the top 5 cm. of soil decreased during dry periods and increased after rain. T. icarus migrates to the wet end of a moisture gradient and has maximum mobility in soil at a moisture content corresponding to field capacity and at 20° C. T. icarus survived osmotic pressure equivalent to 1 m urea for 4 days. Their oxygen consumption increased with increasing osmotic pressure but in 1 m urea there was a decline which was even more pronounced in 2 m urea. Of a population of T. icarus 35% survived for 32 weeks in soil with plants. In damp sand at 10° C, oxygen consumption was steady for 32 weeks but after 48 weeks the nematodes were dead. It is suggested that the free-living stages of plant parasitic nematodes have similar migratory habits.

The stem infestation of Oscinella frit in England is attacked by at least two species of hymenopterous parasites of considerable importance. The species are Halticoptera fuscicornis Walk. (Chalcidoidea) and Rhoptromeris eucera Htg. (Cynipoidea). It is also parasitised to a much lesser degree by Loxotropa tritoma Thoms. (Proctotrypoidea). These three species are described and figured in detail.

The three species named above have been reared by the writer from host puparia obtained in the Harpenden district; they have also been reared in the Leeds and Oxford districts by other observers. They attack the host in the larval stage of the latter and emerge from the puparia. All three species are characteristic parasites of cyclorrhaphous Diptera.

In the Harpenden district a parasitism of 27 per cent. was observed in 1926 and of 37 per cent. in 1927, Rhoptromeris eucera being the dominant parasite.

Evidence is brought forward which appears to indicate that the parasites, collectively, become more abundant as the season advances, with the result that Oscinella frit affecting late sown oats suffers markedly heavier parasitisation than when it attacks oats drilled earlier in the season.

The time of maximum emergence of Oscinella frit in out-of-door rearing cages during the years 1926 and 1927 coincided very closely with its period of greatest abundance in the field, as recorded by Cunliffe.

Evidence was obtained that copulation of Nippostrongylus brasiliensis did not occur until at least 104 h after rats had been subcutaneously infected with 1000 3rd-stage larvae. The majority of worms copulated for the first time approximately 120 h after infection.

Females usually, but not invariably, contained infertile eggs in the uterus before the first insemination occurred. Fertile eggs were not seen in the uterus until sperm had ascended from the vagina to the seminal receptacle, a process which appeared to take about 3 h.

On average each female in a normal mixed infection was capable of producing about 1000 fertile eggs every 24 h. Females recovered from rats on the 10th day after infection and transplanted into uninfected rats, were capable of producing an average of 3500 fertile eggs each without further insemination. When newly matured females, which had received a single full insemination, were isolated from males they produced on average, between 1000 and 1500 fertile eggs each.

From these observations it was concluded that in normal mixed infections females must copulate at least once every other day and probably once a day, in order to maintain fertile egg output. It was also deduced that females are capable of storing from 4000 to 4500 sperm in the seminal receptacle.

There was clear evidence of reduced reproductive efficiency in both male and female worms recovered from rats during the expulsion phase of the infection.

The author wishes to thank Professor J. J. C. Buckley and Dr J. A. McFadzean for their suggestions, criticism and encouragement and Miss G. Merchant and Mrs P. Counsel for able technical assistance.