Four new species of myxosporidian parasites are described from marine fishes from Plymouth: Sinuolinea rebae n.sp., from the urinary bladder of Solea solea; Leptotheca vikrami n.sp., from the gall bladder of Zeus faber; Zschokkella russelli n.sp., from the gall bladder of Gaidropsarus tricirratus and Ciliata mustela; and Zschokkella sturionis n.sp., from the gall bladder of Acipenser sturio.

The various terms used in describing the spore of Myxosporidia are reviewed and revised.

A new classification is proposed of the order Myxosporidia.

I wish to thank the Director of the Marine Biological Association's Laboratory for all the facilities he has enabled me to enjoy during my stay at Plymouth, by dedicating a new species of Zschokkella to him. As a mark of gratitude, and with a deep sense of respect to His Highness the Maharaja of Narsinghgarh State, C.I., I take the liberty of dedicating to him the new species of Leptotheca I have discovered. But for his encouragement and help in the early stages of my career it would have been impossible for me to apply for the India State Scholarship which I now hold. I take this opportunity of expressing my thanks to Miss N. G. Sproston for her unfailing help and encouragement during the present studies and am very grateful to her for going through the manuscript critically.

Neospora caninum is an Apicomplexan protozoan that has the dog as a definitive host and cattle (among other animals) as intermediate hosts. It causes encephalopathy in dogs and abortion in cows, with significant loss in worldwide livestock. As any Apicomplexan, the parasite invades the cells using proteins contained in the phylum-specific organelles, like the micronemes, rhoptries and dense granules. The aim of this study was the characterization of a homologue (denominated NcMIC2-like1) of N. caninum thrombospondin-related anonymous protein (NcMIC2), a micronemal protein previously shown to be involved in the attachment and connection with the intracellular motor responsible for the active process of invasion. A polyclonal antiserum raised against the recombinant NcMIC2-like1 functional core (thrombospondin and integrin domains) recognized the native form of NcMIC2-like1, inhibited the in vitro invasion process and localized NcMIC2-like1 at the apical complex of the parasite by confocal immunofluorescence, indicating its micronemal localization. The new molecule, NcMIC2-like1, has features that differentiates it from NcMIC2 in a substantial way to be considered a homologue†.

Pine wilt is the most serious disease of native pines in Japan and potentially the most important nematode disease of conifers in the world. The pinewood nematode Bursaphelenchus xylophilus was found to be the causal agent. Difficulties arose with respect to the precise identity of some isolates of B. xylophilus and of similar species B. mucronatus and B. fraudulentus. Restriction enzyme analyses of repetitive DNA revealed bands specific for the species B. xylophilus, B. mucronatus and B. fraudulentus. Hybridization patterns obtained with unc-22 gene of C. elegans, clearly identified B. xylophilus, B. mucronatus and B. fraudulentus as well as the different geographic isolates of these species. Furthermore, it is possible to define the phylogenetic relationships between the different populations constituting the ‘pine wood nematode’ complex.

In a recent number of Parasitology Dobell (1926) has expressed disagreement with certain views put forward by me (1923) in a paper dealing with the coccidia of cats, dogs and man. His criticisms deal particularly with the name Isospora belli1 given by me to the coccidium discovered in man during the war, but my observations on the coccidia of cats and dogs also come under review. As regards the coccidia of these animals Dobell's criticisms would undoubtedly have been considerably modified if he had referred to a note written by myself and Sheather (1925). He has apparently overlooked this note entirely, an omission which is all the more unfortunate in that it has a very direct bearing on many of the statements made in his article.

The influence of various agents on the adhesion of endospores of Pasteuria penetrans to the nematode Meloidogyne javanica was studied. Similarly, but to a lesser degree, we have also studied the adhesion of conidia of the fungus Dilophospora alopecuri and the coryneform bacterium Clavibacter sp. (syn. Corynebacterium rathayi) to the nematode Anguina agrostis (syn. A. funesta). Reduction in the degree of both spore and conidial attachment following their pre-treatment with periodate and the presence of PAS staining material on spores, conidia and bacteria implicated carbohydrate in these interactions. Tests involving both unbound and FITC-bound lectins demonstrated that wheat germ agglutinin (WGA) can inhibit the degree of attachment of P. penetrans to M. javanica and that this inhibition can be overcome by pre-treatment of the lectin with N, N′-diacetyl chitobiose. Endospores of P. penetrans, amphid and buccal secretions of 2nd-stage larvae of M. javanica and the cuticle and excretory pore secretions of 2nd-stage dauer larvae of A. agrostis bound WGA, indicating that accessible N-acetyl-D-glucosamine residues are present on these structures. Endospores of P. penetrans also bound Con A, indicating the presence of accessible α-D-glucose/α-D-mannose residues on their surface.

Oropsylla hirsuta is the primary flea of the black-tailed prairie dog and is a vector of the plague bacterium, Yersinia pestis. We examined the population genetic structure of O. hirsuta fleas collected from 11 prairie dog colonies, 7 of which had experienced a plague-associated die-off in 1994. In a sample of 332 O. hirsuta collected from 226 host individuals, we detected 24 unique haplotype sequences in a 480 nucleotide segment of the cytochrome oxidase II gene. We found significant overall population structure but we did not detect a signal of isolation by distance, suggesting that O. hirsuta may be able to disperse relatively quickly at the scale of this study. All 7 colonies that were recently decimated by plague showed signs of recent population expansion, whereas 3 of the 4 plague-negative colonies showed haplotype patterns consistent with stable populations. These results suggest that O. hirsuta populations are affected by plague-induced prairie dog die-offs and that flea dispersal among prairie dog colonies may not be dependent exclusively on dispersal of prairie dogs. Re-colonization following plague events from plague-free refugia may allow for rapid flea population expansion following plague epizootics.

1. The development of Theileria parva in engorged larvae of R. appendiculatus exposed to a temperature of 4–6° C. for 3 days at intervals of 2, 4, 6, 8 and 9 days after repletion is not retarded; and it appears, from previous experiments and those now described, that, as long as the tick survives, climatic conditions do not kill or weaken the parasite.

2. The virulence of East Coast fever transmitted by ticks fed in the tail brush did not differ from the disease conveyed by ticks infesting the ears.

3. Reference is made to records of mild reactions to Bast Coast fever when the parasites are either rare or absent; and instances are given of such reactions followed by recovery in experimental animals. Although the mild form of the disease seems associated at times with light tick infestation, it is proved that a few infected ticks also transmit a fatal East Coast fever. It is shown also that ticks fed on a bovine during a short or mild reaction can produce a virulent form of the disease in susceptible animals, and that mild reactors acquire an immunity to the virulent disease.

4. The experiments which are described indicate that ticks do not become infected with T. parva from the blood of a bovine for the first 4 days of the reaction period.

5. Evidence is produced which strongly suggests that T. parva tends to disappear from infected hungry ticks kept under laboratory conditions for about a year or more. The age of the tick would appear to be an important factor in the transmission of East Coast fever.

6. Attempts to break down the immunity to East Coast fever, and to produce “turning-sickness”, by massive infestations of ticks were unsuccessful; and further experiments on the transmission of East Coast fever by ticks which had fed on animals suffering from “turning-sickness” did not confirm earlier positive results.

These conflicting results may be explained by the observations that “turning-sickness”, associated with the blocking of the small capillaries of the brain by lymphocytes containing schizonts indistinguishable from the Koch's bodies of T. parva, may be divided into three stages, namely, acute, subacute and chronic; and it is suggested that infection of ticks with T. parva from “turning-sickness” could normally be successful only from animals in the acute and early part of the subacute stages since piroplasms disappear from the peripheral blood stream in the more advanced cases of “turning-sickness”.

7. The opinions of other workers on East Coast fever are discussed in the light of the experiments carried out at Kabete and of field experience in Kenya Colony. It is explained how the results can be applied to the movement of cattle from endemic areas over country free from East Coast fever.

A new species, Demodex aurati, is described from the Golden Hamster, Mesocricetus auratus. It differs in both morphological detail and ecological niche from D. criceti present on the same host.

When pieces of heavily parasitized skin were ‘subplanted’ for 100 days no change in morphological features of either D. aurati or D. criceti occurred.

D. aurati is a low grade pathogen, apparently only harvesting the cells of the follicular epithelium.

The life cycle of D. aurati is described.

The presence on one host species of two different species of this genus, which has affinities with demodicids of evolutionally remotely related hosts, poses an interesting problem in species specificity and ectoparasite evolution.

I wish to thank Dr Miriam Shaw, Miss Shirley DiBenedetto and Miss Helen Krause for their excellent technical help, and Dr Lawrence Bartlett and Dr Harold Rauch for perusal of the manuscript and suggestions on project procedure.

This investigation was supported by a research grant E-562 from the Institute of Allergy and Infectious Disease, of the National Institutes of Health, Public Health Service.

Allozyme markers were used to study genetic variation in Lecithochirium fusiforme within a natural population of Conger conger. Six of 16 enzyme-coding loci studied were found to be polymorphic. These loci were surveyed in 12 infrapopulations of adult flukes. High levels of genetic variation were detected (P=0·375); Ho=0·048; He=0·085). However, the population did not conform to Hardy-Weinberg expectations, as it showed a significant deficit of heterozygotes. L. fusiforme also exhibited low differentiation between infrapopulations (FST=0·064). Despite significant linkage disequilibrium at Pgm-1 and Pgm-2 (P<0·05), mating system does not appear to be the principal reason for the deficit of heterozygotes detected, because some polymorphic loci were in Hardy-Weinberg equilibrium. Association between FIS and FST statistics suggests the existence of the Wahlund effect. However, all infrapopulations showed a strong deficit of heterozygotes for most polymorphic loci (FIS=0·409). Detection of significant genetic differentiation among temporal samples and the existence of paratenic hosts in the life-cycle suggests the Wahlund effect, caused by the mixture of genetically distinct temporal samples in the infrapopulations. Occasional temporal gene flow also might explain the high estimated genetic polymorphism.

The cercaria of Fasciola hepatica has four types of cystogenic cells which can be characterized by their position and by their histochemical properties. On the basis of their histochemical reactions, each type of cell was related to a specific layer in the cyst wall of the metacercaria.

The tanned protein cells occupy almost all of the ventral half of the body and contain large granules consisting of basic protein and phenols. Although the presence of a phenolase could not be demonstrated, it is considered that the granules are composed of tanned protein. Before the cercaria leaves the redia, the granules are secreted to the exterior to form a layer contained by a thin, bounding membrane. The tanned protein cells form layer I of the cyst wall.

The mucopolysaccharide cells are concentrated at the dorsal and dorso–lateral surface except for a few around the ventral sucker. They contain acid and neutral mucopolysaccharides and contribute to layers II and IIIb and c. Some of the granules are secreted to the exterior before the cercaria leaves the redia, in a similar manner to the tanned protein granules.

The mucoprotein cells are few in number and lie centrally between the ventral sucker and the pharynx. They give reactions for proteins and carbohydrate-protein complexes and probably help to form layers II and IIIa of the cyst wall.

The keratin cells fill almost the entire dorsal half of the body and contain numerous rod-like granules. These rods are composed of a protein containing sulphydryl groups and disulphide bonds and give rise to layer IV. After secretion of the tanned protein granules to the exterior, some of the keratin cells move to the ventral part of the body formerly occupied by the tanned protein cells.

The outer cyst wall exists in a preformed state in the free swimming cercaria.

I am grateful to Professor J. D. Smyth and Dr J. A. Clegg of this department for advice and encouragement during this investigation and in the preparation of the manuscript. The work was done during the tenure of a Commonwealth Post-Graduate Scholarship.

Field rodent surveys for Babesia infection were performed from 2002 to 2005 in the vicinities of human babesiosis occurrences in Taiwan and mainland China. Babesia microti was identified by microscopical examination and/or PCR in 1 Rattus coxinga and 1 Crocidura horsfieldii in central Taiwan and in 13 Niviventer confucianus and 1 Apodemus agrarius in Zhejiang and Fujian Provinces of southeastern China. Of 15 B. microti samples detected by PCR, all except 1 were shown to be the Kobe-type, the aetiological small subunit rRNA gene-type of the first Japanese patient; the exception was also a Kobe-related type. The Kobe-type had been found in rodents only in a few places including the human infection occurrence place in Japan. The internal transcribed spacer 1 to 2 sequences of the Taiwanese and Chinese Kobe-types were very similar to each other but considerably different (approx. 94% pairwise identities) from that of the Japanese Kobe-type. A Taiwanese Kobe-type strain was serologically differentiated from the Kobe strain originating from the Japanese first patient. The distribution of the Kobe-type in the vicinities of human babesiosis occurrences in Taiwan and China as well as in Japan is suggestive of involvement of the Kobe-type in Asian human babesiosis.

Various treatments are found to be moderately effective in managing Demodex-related diseases except tea tree oil (TTO) and terpinen-4-ol (T4O), which showed superior miticidal and anti-inflammatory effects in numerous clinical studies. Their possible effects include lowering mite counts, relieving Demodex-related symptoms, and modulating the immune system. This review summarizes the current clinical topical and oral treatments in human demodicosis, their possible mechanisms of action, side-effects and resistance in treating this condition. TTO (especially T4O) is found to be the most effective followed by metronidazole, ivermectin and permethrin in managing the disease. This is because TTO has anti-parasitic, anti-bacterial, anti-fungal, anti-inflammatory and wound-healing effects. Furthermore, nanoTTO can even release its contents into fungus and Pseudomonas biofilms. Combinations of different treatments are occasionally needed for refractory cases, especially for individuals with underlying genetic predisposal or are immuno-compromised. Although the current treatments show efficacy in controlling the Demodex mite population and the related symptoms, further research needs to be focused on the efficacy and drug delivery technology in order to develop alternative treatments with better side-effects profiles, less toxicity, lower risk of resistance and are more cost-effective.

Life-history attributes of the capsalid monogenean Benedenia lutjani, a parasite of Lutjanus carponotatus from the Great Barrier Reef, Queensland, Australia, were investigated from experimental infections. Oncomiracidia of B. lutjani invaded and attached at any site on the fish, but more commonly invaded body surfaces. Immature specimens then migrated to the pelvic fins. Development of the reproductive organs of B. lutjani corresponded with migratory movements on the host. Parasite aggregation on the pelvic fins coincided with the development of functional male reproductive organs and some protandrous worms that possessed a vagina appeared to be inseminated. Migration to, and aggregation on, the branchiostegal membranes (membranous folds posterior to the opercula) coincided with the onset of sexual maturity and commencement of egg production by parasites. The rate of parasite development and the timing of migratory events on the host were influenced by water temperature. All specimens of B. lutjani reached sexual maturity between 12 and 14 days p.i. at 24 °C and between 8 and 10 days p.i. at 27 °C. Anterior hamuli grew continually during a 16-day experiment at 27 °C and 25-day experiment at 23 °C and their length appeared to provide a suitable index to estimate parasite age. The possible adaptive significance of the migratory behaviour, site-specificity and its link with changes in parasite development are discussed.

A deterministic, dynamic simulation model is developed to account for the interactions between gastrointestinal parasitism and host nutrition, and predict their consequences on performance and level of parasitism of sheep. Larval intake and established adult worms are assumed to result in nutrient loss for the host. In order to reduce this loss the host will mount an immune response, which will affect the establishment rate of incoming larvae, mortality rate of adult worms, and fecundity of female worms, as well as nutrient loss caused by larval intake per se. Host anorexia is modelled as a function of worm mass. Parasitism is also assumed to affect the allocation of ingested nutrients to the host's bodily functions, with maintenance getting absolute priority, and protein allocated to immunity and production proportionally to their requirements. Inputs to the model include the expected growth attributes of the animal, feed quality, various parasitological parameters and daily larval intake. Outputs include feed intake, growth rate and body composition, as well as worm burden and faecal egg counts. The model allows exploration of the consequences of gastrointestinal parasitism on sheep of different growth characteristics, kept under environments that vary in the provision of nutrients and exposure to parasites.

This work was carried out with a strain of trypanosomes isolated by inoculation into domestic rabbits of fleas naturally infected from wild rabbits in Hertfordshire.

The course of infection was studied in experimentally infected normal and splenectomized rabbits, in which the incubation period varied from 5 to 12 days. After recovery from the infection, rabbits became immune to re-infection. Immune rabbit serum had no protective action against Trypanosoma lewisi.

Attempts to infect other animals with the rabbit trypanosome produced negative results.

Young rabbits proved to be more susceptible to infection with this trypanosome, and their parasitaemia lasted longer than in adult rabbits, but the parasite was found to be non-pathogenic to these animals.

It was demonstrated that this trypanosome multiplies in the spleen, where the stages of division are confined to the capillaries. Multiplication follows the inoculation of metacyclic trypanosomes from infected fleas or blood forms. It proceeds by division of the nucleus and kinetoplast into four, followed by fission of the cytoplasm, giving rise to four small daughter individuals. These are transformed into trypanosome forms, which are shed into the peripheral blood, where they change into the typical adult trypanosomes.

The development in the intermediate host takes place in the gut of the rabbit flea, Spilopsyllus cuniculi, with the production of metacyclic trypanosomes in the hind-gut (posterior station).

The nomenclature and synonymy of the rabbit trypanosome are discussed, and it is concluded that its valid name is Trypanosoma nabiasi Railliet, 1895.

The inadequacy of current diagnostics for the detection of low worm burdens in humans means that schistosomiasis mansoni is more widespread than previously acknowledged. With the inception of mass drug treatment programmes aimed at disease elimination and the advent of human vaccine trials, the need for more sensitive diagnostics is evident. In this review, we evaluate the merits and limitations of the principal diagnostic methods, namely detection of eggs in faeces; anti-schistosome antibodies in serum; parasite-derived proteins and glycans in serum or urine; parasite DNA in blood, faeces or urine. Only in the baboon model, where actual worm burden is determined by portal perfusion, have faecal smear and circulating antigen methods been calibrated, and shown to have thresholds of detection of 10–19 worm pairs. There is scope for improvement in all the four methods of detection, e.g. the identification of single targets for host antibodies to improve the specificity of enzyme linked immunosorbent assay. Despite recent advances in the definition of the schistosome secretome, there have been no comprehensive biomarker investigations of parasite products in the urine of infected patients. Certainly, the admirable goal of eliminating schistosomiasis will not be achieved unless individuals with low worm burdens can be diagnosed.

In complex organisms, apoptosis is a constitutive cell death process that is involved in physiological regulation of cell numbers and that can also be induced in the course of inflammatory and immune responses. Neutrophils are among the first cells recruited during inflammation. Neutrophils constitutively die by apoptosis at inflamed sites, and are ingested by macrophages. Recent studies investigated how phagocytic clearance of senescent neutrophils influences the survival of intracellular protozoan parasites that have been phagocytosed by, or have invaded phagocytes. The results indicate that neutrophil clearance plays an unexpected role in regulation of intramacrophagic protozoan parasite infection.

Epidemiological data are often fragmented, partial, and/or ambiguous and unable to yield the desired level of understanding of infectious disease dynamics to adequately inform control measures. Here, we show how the information contained in widely available serology data can be enhanced by integration with less common type-specific data, to improve the understanding of the transmission dynamics of complex multi-species pathogens and host communities. Using brucellosis in northern Tanzania as a case study, we developed a latent process model based on serology data obtained from the field, to reconstruct Brucella transmission dynamics. We were able to identify sheep and goats as a more likely source of human and animal infection than cattle; however, the highly cross-reactive nature of Brucella spp. meant that it was not possible to determine which Brucella species (B. abortus or B. melitensis) is responsible for human infection. We extended our model to integrate simulated serology and typing data, and show that although serology alone can identify the host source of human infection under certain restrictive conditions, the integration of even small amounts (5%) of typing data can improve understanding of complex epidemiological dynamics. We show that data integration will often be essential when more than one pathogen is present and when the distinction between exposed and infectious individuals is not clear from serology data. With increasing epidemiological complexity, serology data become less informative. However, we show how this weakness can be mitigated by integrating such data with typing data, thereby enhancing the inference from these data and improving understanding of the underlying dynamics.

The results are described of further studies on a virus found in the roots of certain normal-looking plants. It is shown that the virus is a contamination arriving from outside sources. The virus has been detected in the sludge at the bottom of the water tanks, and the experimental evidence shows that it is water-borne to the soil whence it reaches the roots of the plants. Experiments to test the possibility that the virus is also air-borne have so far proved negative.

The virus is exceedingly resistant, it can be completely desiccated and remains infective in the dry state for many weeks. It is also unaffected by alcohol and is still infective after being stored in absolute alcohol for 6 months.

The virus is thought to be a transitional stage between a pathogen and a non-pathogen.