We revisited the role of dissimilarity of host assemblages in shaping dissimilarity of flea assemblages using a non-linear approach. Generalized dissimilarity models (GDMs) were applied using data from regional surveys of fleas parasitic on small mammals in four biogeographical realms. We compared (1) model fit, (2) the relative effects of host compositional and phylogenetic turnover and geographic distance on flea compositional and phylogenetic turnover, and (3) the rate of flea turnover along gradients of host turnover and geographic distance with those from earlier application of a linear approach. GDMs outperformed linear models in explaining variation in flea species turnover and host dissimilarity was the best predictor of flea dissimilarity, irrespective of scale. The shape of the relationships between flea compositional turnovers along host compositional turnover was similar in all realms, whereas turnover along geographic distance differed among realms. In contrast, the rate of flea phylogenetic turnover along gradients of host phylogenetic turnover differed among realms, whereas flea phylogenetic turnover did not depend on geographic distance in any realm. We demonstrated that a non-linear approach (a) explained spatial variation in parasite community composition better than and (b) revealed patterns that were obscured by earlier linear analyses.

1. A progenetic metacercaria of Phyllodistomum lesteri sp.nov. is found encysted in the fresh-water shrimps, Palaemon asperulus von Marten and P. nipponensis de Haan.

2. A systematic description is made of this new species including general characteristics of the family, subfamily and genus and a list of the existing 29 phyllodistomes.

3. In general, the new form resembles Pleurogenes medians with regard to its progenetic development.

4. Feeding experiments suggest that two species of fish, Odontobutis obscura and Pelteobagrus fulvidraco, and a species of toad, Bufo bufo asiaticus, are not the final hosts of Phyllodistomum lesteri sp.nov.

Domestic dogs can function as either paratenic or definitive hosts for the zoonotic raccoon roundworm Baylisascaris procyonis. However, factors leading to development of patent infections in dogs are under-studied. Here we compared infection dynamics of B. procyonis in dogs vs the natural raccoon host. Dogs and raccoons were inoculated 5000 or 500 B. procyonis eggs (n = 3 per dose) or were fed B. procyonis-infected laboratory mice (n = 3 per dose; mice inoculated with 1000 or 250 eggs). Fecal samples were analysed via flotation and a commercial coproantigen ELISA designed for detection of Toxocara spp. Two of 12 dogs (both received low dose larvae) developed patent infections; all 12 raccoons became infected with 10 developing patent infections. Compared with dogs, prepatent periods were shorter in raccoons and maximum egg outputs were much greater. Baylisascaris procyonis coproantigens were detectable via ELISA in all raccoons and the patently infected dogs. Finally, dogs spontaneously lost infections while all patently infected raccoons shed eggs until conclusion of the study. Our results demonstrate that dogs are clearly suboptimal hosts showing limited parasite establishment and fecundity vs raccoons. Despite the low competence, patently infected dogs still pose a risk for human exposure, emphasizing the importance of control measures.

Genome assemblies can form the basis of comparative analyses fostering insight into the evolutionary genetics of a parasite's pathogenicity, host–pathogen interactions, environmental constraints and invasion biology; however, the length and complexity of many parasite genomes has hampered the development of well-resolved assemblies. In order to improve Trichinella genome assemblies, the genome of the sylvatic encapsulated species Trichinella murrelli was sequenced using third-generation, long-read technology and, using syntenic comparisons, scaffolded to a reference genome assembly of Trichinella spiralis, markedly improving both. A high-quality draft assembly for T. murrelli was achieved that totalled 63·2 Mbp, half of which was condensed into 26 contigs each longer than 571 000 bp. When compared with previous assemblies for parasites in the genus, ours required 10-fold fewer contigs, which were five times longer, on average. Better assembly across repetitive regions also enabled resolution of 8 Mbp of previously indeterminate sequence. Furthermore, syntenic comparisons identified widespread scaffold misassemblies in the T. spiralis reference genome. The two new assemblies, organized for the first time into three chromosomal scaffolds, will be valuable resources for future studies linking phenotypic traits within each species to their underlying genetic bases.

In spite of the fact that frogs form a common subject of biological examination and experiment it is curious that, in this country, there have been few reports on the helminth parasites with which they are so frequently infected. We owe practically all our knowledge of the Trematode parasites of amphibians to continental zoologists. The early researches of von Frölich (1789–1802) and Rudolphi (1809) followed, a hundred years later, by those of von Linstow (1877–1890) and Looss (1894–1901), are responsible for the greater part of the existing information. Amongst others who have devoted some attention to the subject may be mentioned the names of Dujardin (1845), Diesing (1836–1858), Gastaldi (1854) and Olsson (1876).

The behavioural responses of Onchocerca lienalis microfilariae (mf) to tissue factors of the surrogate black fly host, Simulium vittatum, were studied using a novel in vitro bioassay. Mf accumulated towards thoracic tissues to a density 4 times higher than towards abdominal tissues, despite the larger surface area and volume of abdominal tissues. Mf migrated toward thoracic tissues regardless of whether or not contact with thoracic tissues was possible. Therefore, mf directed themselves toward the thorax rather than arresting their movement after they make contact with thoracic tissues. Chemical cue(s) provided a principal guidance for mf to locate thoracic tissues. Mf lost their ability to differentiate thoracic and abdominal tissues following addition of thoracic attractant(s) to excised abdomens and reversed their differential response when excised thoraces were depleted of chemical cue(s). Mf did not respond to salivary gland product, but to other thoracic factor(s). Intact thorax that was connected to 1–2 abdominal segments attracted considerably less mf than excised thorax. However, intact thorax attracted more mf than excised abdomen. Abdominal tissue size did not affect thorax attractiveness. Involvement of a large molecular weight protein(s) was suggested by the high attractiveness of the 100 kDa Centricon concentrator retentate and complete precipitation of attractant(s) by ethanol.

In a previous paper (1927) I have given a general account of Dipterous larvae and their parasites living in the wounds of a horse-chestnut tree standing on the Downing site, Cambridge. This tree contained two types of wounds: (1) a surface wound with sap exudation or slime-flux, and (2) a large hollow or reservoir filled with water.

Third-stage larvae of Pseudoterranova decipiens commonly infect whitefish such as cod, and the parasite can be transferred to humans through lightly prepared (sushi) meals. Because little is known about the nematode's cold tolerance capacity, we examined the nematode's ability to supercool, and whether or not cold acclimation could induce physiological changes that might increase its ability to tolerate freezing conditions. Even if third-stage Pseudoterranova decipiens larvae have some supercooling ability, they show no potential for freezing avoidance because they are not able to withstand inoculative freezing. Still, they have the ability to survive freezing at high subzero temperatures, something which suggests that these nematodes have a moderate freeze tolerance. We also show that acclimation to high temperatures triggers trehalose accumulation to an even greater extent than cold acclimation. Trehalose is a potential cryoprotectant which has been shown to play a vital role in the freeze tolerance of nematodes. We suggest that the trehalose accumulation observed for the cold acclimation is a general response to thermal stress, and that the nematode's moderate freeze tolerance may be acquired through adaptation to heat rather than coldness.

It has already been shown (Imms, 1930) that the stem generation of the frit-fly in the Harpenden district is subjected to natural destruction, to a marked degree, by the agency of certain hymenopterous parasites. Among these, two species, viz. the Cynipid Rhoptromeris eucera Htg. and the Chalcid Halticoptera fuscicornis (Walk.) were found to predominate in numbers. Parasitisation, to a lower degree, by the Proctotrypid Loxotropa tritoma Thoms. was also noted and the Chalcid Callitula bicolor Spin. was recorded for the first time as having been reared from this same host. Evidence was also brought forward which o appeared to indicate that the parasitisation of frit-fly by the above combination of species increases in intensity as the season advances. In other words the stem generation of frit-fly, attacking late sown oats, is subjected to markedly heavier parasitisation than when it attacks oat sown earlier in the same season.

The migration of infective nematode larvae into the tissues of their hosts has been proposed as a mechanism of reducing larval mortality and increase parasite lifetime reproductive success. Given that individual hosts differ in the level of exposure, strength of immune response and physiological conditions we may expect the number of larvae in tissue to vary both between and within hosts. We used 2 gastrointestinal nematode species common in the European rabbit (Oryctolagus cuniculus) and examined how the number of larvae in the tissue changed with the immune response, parasite intensity-dependent constraints in the lumen and seasonal weather factors, in rabbits of different age, sex and breeding status. For both nematode species, larvae from the gastrointestinal tissue exhibited strong seasonal and host age-related patterns with fewer larvae recovered in summer compared to winter and more in adults than in juveniles. The number of larvae of the 2 nematodes was positively associated with intensity of parasite infection in the lumen and antibody responses while it was negatively related with air temperature and rainfall. Host sex, reproductive status and co-infection with the second parasite species contributed to increase variability between hosts. We concluded that heterogeneities in host conditions are a significant cause of variability of larval abundance in the gastrointestinal tissues. These findings can have important consequences for the dynamics of nematode infections and how parasite's life-history strategies adjust to host changes.

It has been shown that in samples of the eggs of T. colubriformis, the smaller eggs (i) have a greater probability of survival when incubated at fixed temperature and saturation deficit; (ii) require less time to develop and hatch when incubated in water at constant temperature, and (iii) have a greater surface area relative to volume, than do the larger eggs.

A hypothetical basis for the relation between egg size and desiccation survival is briefly discussed.

Responses to Taenia taeniaeformis infection were studied in mice with severe combined immunodeficiency (scid), which lack functional T and B lymphocytes. In the early phase of infection, accumulation of polymorphonuclear leucocytes (PML) occurred around the larvae in the liver of scid mice and their immunocompetent counterparts, C.B-17, (a BALB/c strain, genetically resistant to this parasite). PML accumulation continued until encapsulation of developing larvae by fibroblasts (14 days p.i.), and subsequent fibrosis resulted in granuloma formation. No infiltration of eosinophils or macrophages around larvae was observed in scid mice prior to granuloma formation, while in C.B-17 mice infiltration was observed as early as 5 days p.i., when specific antibodies could not be detected in the circulation. Most larvae were destroyed by 14 days p.i. in C.B-17 mice. In scid mice the larvae survived but the host capsules (cysts) were thin and most contained blood at 42 days p.i. In these cysts, inflammatory cells were observed on the larval surface and in invaded parasite tissue. Hepatocyte coagulation necrosis adjacent to larvae was commonly found in C.B-17 mice by 5 days p.i., while it did not occur in scid mice throughout these experiments. These results suggest that in host responses to larval T. taeniaeformis, PML accumulation and encapsulation by fibrosis are T and B cell independent, while eosinophil and macrophage infiltration, as well as resistance to infection, are T and/or B cell dependent. Additionally, there may be an association between host cell necrosis around larvae and T and/or B cell responses.

High primary doses of Trichinella spiralis administered orally to Kenyan baboons (Papio anubis) induced a marked but unpredictable eosinophilia which started 2–3 weeks after infection and persisted as erratic waves for at least 6 months. Low primary oral doses induced no eosinophilia but a later, high challenge gave an accelerated eosino-philic response, although the peak was lower than in high primary infection. Intravenous injection of infective T. spiralis larvae resulted in a predictable, rapid eosinophilic response which persisted for several weeks. Intravenous injection of a particulate material, Sepharose, gave no oesinophilic response.

Percutaneous Schistosoma mansoni infection of baboons resulted in a two-stage eosinophilic response: an initial rise occurred about ⅔ of the way through the pre-patent period and was followed by a second rise at the onset of patency. After peaking, the eosinophilia waned erratically over the next 3 or 4 weeks.

A strong antibody response, measured by countercurrent imnruno-electrophoresis, was given in oral infections with T. spiralis, but intravenous injections elicited little or no antibody formation. Parasitological evidence indicated no cross-resistance to S. mansoni in baboons injected with T. spiralis 9 days previously. Thus, the intravenous injection of infective T. spiralis larvae appears to be a suitable method of inducing experimentally a non-specific eosinophilia to investigate possible immune mechanisms to S. mansoni in the baboon.

The Mochlus fernandi lizards (Scincidae) from the Kivu province (Congo) around Lwiro, Katana, are infected with a broad leaf-like monomorphic trypanosome, Trypanosoma mochli. The high moisture requirements of M. fernandi, which resemble European salamanders, and the morphological similarity of T. mochli to amphibian trypanosomes point to an aquatic transmission and vector for this species.

In this study two aspects of the biology of the cercaria of Himasthla militaris were examined. Firstly, the cercarial emergence from the first intermediate host, Hydrobia stagnorum, was studied. On a 9 h light (9L)/15 h dark (15D) schedule cercariae of Himasthla militaris emerged from naturally infected Hydrobia stagnorum predominantly during darkness. Inversion of the photo-period resulted in an immediate reversal of the emergence pattern. A comparison between the cercarial release patterns under natural conditions and in a constant light/temperature environment showed that an endogenous as well as an exogenous factor is controlling this process. Secondly, the penetration of the cercaria in Nereis diversicolor and the site-finding of the larva within this second intermediate host was investigated. After a short external migration on the body of N. diversicolor the cercaria enters the polychaete via the anus opening, perforates the gut-wall and moves through the coelom to the anterior segments to encyst in the muscle tissue. This internal migration results in a specific distribution pattern of the metacercariae, with more than 50% of the cysts localized in the first 12 segments and a maximum in segment number 9 (13·8%).

Very little is known about parasite-altered mating behaviour. This paper describes two experiments on the impact of infection and starvation on mating in Biomphalaria glabrata snails. In the first experiment, snails were infected with the parasitic trematode Schistosoma mansoni. During both the early and the late stages of infection, snails were allowed to mate with individuals of the same infection status and uninfected controls. Their mating activities were filmed and later analysed. The mating frequencies of patently infected (shedding) snails were found to be lower than those of controls. This is thought to result from stress induced by the pathology. Successfully infected snails were found to mate more often as males than as females. This is seen as a compensation for the reduced fecundity caused by trematode infection. Successfully infected snails also exhibited partner choice. More matings were found between snails of the opposite infection status than among snails of the same infection status. This may be explained by the good genes hypothesis and can be seen as a specific response to schistosome infection. In the second experiment, starved snails were allowed to mate with starved and control snails. They mated less often than controls and more often as males than as females, controls showing the opposite pattern. This may be considered to be a general stress response. No partner choice has been found with starved snails. It is suggested that partner choice in infected snails occurs in response to specific rather than general stress.

In former times when this country was dependent upon bees for its supply of sugar, a heavy mortality among these insects was of sufficient importance to be placed on record. In his Animal Plagues Fleming (1871) gives a number of references to such losses. In Ireland there was a “mortality of bees” in 950 A.D. and again in 992 A.D. there was a “great mortality upon men, cattle and bees.” In 1035 A.D. the destruction of bees afflicted the whole of Bavaria. An eclipse of the sun in 1124 A.D. was followed by a great pestilence amongst oxen, sheep, pigs, and bees. During the time of the “Black Death,” also, there appears to have been heavy losses of bees and at the Manor Court of Heacham in Norfolk, a statement was made on oath by the steward in the forty-fifth year of the reign of Edward III (1372 A.D.) to the effect that ten out of eleven stocks of bees had perished from the murrain. There is little doubt that this entry in the manorial court rolls refers to epidemic disease, but, as Fleming points out, “there is evidently no relationship between the morinâ of the bees and that of the sheep and cows.”