Cytochemical staining with diaminobenzidine (DAB) has been used to locate cytochrome oxidase activity in mitochondria from major tissues of three intestinal parasitic nematodes, Nippostrongylus brasiliensis, Haemonchus contortus and Ascaridia galli. Deposition of DAB reaction product was uniform and relatively intense in mitochondria from all tissues studied in N. brasiliensis. However, mitochondria from different tissues of H. contortus and A. galli varied considerably in their cytochemical staining, decreasing in the order hypodermis < muscle < gut < reproductive tissue. Mitochondria in gut and reproductive tissue of A. galli possessed little or no cytochrome oxidase activity. These results are compatible with respect to oxygen availability and the extent and localization of the mammalian-type aerobic mitochondrial electron transport pathway in intestinal parasitic nematodes.

The larval output of Angiostrongylus cantonensis at different initial densities in rats was examined throughout the reproductive life-span of the worms using a modified dilution technique. With an initial density of 2 worms the mean duration of larval output was 414·2 days. The output was at a level above 50000 larvae/female/day from 15 to 45 weeks after infection. The mean total output was 18·9×106 larvae/female. The larval output/female decreased with an increase in the worm burden and also with the passage of time after infection. The longevity of host rats also decreased with increasing worm density and many of the heavily infected rats died early during infection. These results suggest that worm density has an effect on the fecundity of this parasite, and that the effects may be due to fibrous changes in host lung tissue but not changes in the physiology of the worms. It is also suggested that density-dependent effects on fecundity play a role in the population dynamics of both the parasite and host as regulatory mechanisms in the field.

Reciprocal crosses (Schistosoma intercalatum male Zaire×S. intercalatum female Cameroon: S. intercalatum female Zaire×S. intercalatum male Cameroon) were produced in 10 mice by exposing each mouse to 60 male cercariae of one isolate and 60 female cercariae of the other isolate, and vice versa. Hybrid generations originating from the two crosses were established. The infectivity of the F1, F2, F3 and F4 hybrid generations were evaluated after exposing snails individually to 5 miracidia. A comparative histological study of snails infected with F2 and F4 hybrid sporocysts from both crosses was made to assess abnormalities in the intramolluscan development of the hybrids. The worm recovery rate and fecundity were measured by comparing the fitness of the mid-parents with that of the hybrids. S. intercalatum Cameroon was compatible with Bulinus forskalii and incompatible with B. globosus whereas S. intercalatum Zaire was compatible with B. globosus and incompatible with B. forskalii. In the case of S. intercalatum male Cameroon×S. intercalatum female Zaire, hybrid miracidia develops in both B. forskalii and B. globosus in F1, F2 and F3 generations. The infection rate was much lower for B. globosus and F2 and F3 generations produced few cercariae (less than 30 cercariae in overall per snail) and F4 miracidia were only infective to B. forskalii again producing few cercariae. At 40 days post-infection the sporocyst contains masses of acidophilic granules originating from the breakup of pycnotic nuclei. Similarly the F1, F2 and F3 miracidia of the reciprocal cross (S. intercalatum male Zaire×S. intercalatum female Cameroon) exhibited a dual infectivity for B. forskalii and B. globosus, but cercarial productivity was low (less than 30 cercariae overall per snail for F2 and F3 generations). Histological studies demonstrated sporocyst degeneration in snails infected with F4 generation. In the definitive host, the F1 generation (both crosses) exhibited hybrid vigour in that the worm return was greater than that of the mid-parent, F2 and F3 generations. No significant difference in fecundity was demonstrated between the parental strains and the F1 and F2 generations, yet egg production of the F3 generation was significantly lower. It is apparent that there is a post-zygotic barrier in the crosses of S. intercalatum Zaire and S. intercalatum Cameroon from the F2 generations onwards, and sterility of the F4 hybrid sporocyst supports the concept of the existence of 2 distinct taxa.

The genus Eulaelaps was raised by Antonio Berlese in 1903 to include the species of Laelaptidae in which the genito-ventral scutum of the female was large and extended to the anal scutum, and which possessed a large triangular meta-podal scutum posterior to coxa iv.

In order to improve our knowledge about the taxonomic status and the population structure of the causative agent of Human African Trypanosomiasis in the Central African subregion, 169 newly isolated stocks, of which 16 came from pigs, and 5 reference stocks, were characterized by multilocus enzyme electrophoresis, for 17 genetic loci. We identified 22 different isoenzyme profiles or zymodemes, many of which showed limited differences between them. These zymodemes were equated to multilocus genotypes. UPGMA dendrograms revealed one main group: Trypanosoma brucei gambiense group I and 3 T. brucei ‘non-gambiense’ stocks. T. b. gambiense group I zymodemes were very homogenous, grouping all the human stocks and 31% of the pig stocks. Two main zymodemes (Z1 and Z3) grouping 74% of the stocks were found in different remote countries. The genetic distances were relatively high in T. brucei ‘non-gambiense’ zymodemes, regrouping 69% of pig stocks. The analysis of linkage disequilibrium was in favour of a predominantly clonal population structure. This was supported by the ubiquitous occurrence of the main zymodemes, suggesting genetic stability in time and space of this parasite's natural clones. However, in some cases an epidemic population structure could not be ruled out. Our study also suggested that the domestic pig was a probable reservoir host for T. b. gambiense group I in Cameroon.

1. Stained specimens of two forms of a ciliate parasite resembling Lambornella stegomyiae Keilin which is probably Glaucoma pyriformis Ehrenberg are discussed. These were collected from the haemocoel of culicine mosquito larvae at Livingstone, Northern Rhodesia. The form previously referred to as type A (Muspratt, 1945) is the fast multiplying form which destroys the larva and that referred to as type B is considered to be either an encysting or degenerate form.

2. In nature the larva of Aëdes (Finlaya) fulgens Edw. is the most suitable host of the parasite because the normal (type A) parasitic ciliates are dependent on escaping from the larval host before death by the rupture of the anal papillae. This occurs most frequently in parasitized larvae of the above species.

3. The encystment of the organisms on the cuticle of the larvae is discussed with reference to statements by previous workers. Stages in the penetration of the cuticle by the organisms and the formation of cuticular resting cysts have been observed.

4. Larvae of A. aegypti used in laboratory experiments proved to be unsuitable as: (a) The anal papillae do not rupture easily. (b) After some time the reproductive power of the ciliates degenerates if they are transmitted from larva to larva of this species only.

5. Attempts to destroy anopheline larvae with the parasite were negative although the ciliates entered the haemocoel.

6. A suggestion as to the possible life-cycle is appended in the form of a diagram.

Following a brief historical introduction, the results of differential counts, precipitin tests and skin reactions on seven cases of trichinosis 4–9 years after recovery are presented. Eosinophile counts ranging from 2 to 7 per cent. were encountered, but the number of cases studied does not warrant any conclusion being drawn. Positive precipitin tests and intradermal reactions were encountered in cases up to 7 years after infection. The findings are discussed, together with a consideration of the pertinent literature, and the importance of the skin reaction and precipitin tests as aids to diagnosis are emphasised in conjunction with due consideration of the history and symptomatology. It is affirmed that the tests have proved of value in establishing a diagnosis in mild cases.

It is a pleasure to acknowledge our indebtedness to Dr George R. Minot, who made the records of the hospital available to us, and to Dr W. D. Sutliff, whose continued interest and ready co-operation greatly facilitated our work.

The behaviour and development of Elasmosoma sp., near pergandei Ashm. (Neoneurinae: Braconidae: Hymenoptera), a parasite of the ant, Formica obscuriventris clivia Creighton, was studied in a coastal sand dune habitat in central Oregon over a 2-year period. Female wasps oviposited into the abdomen of major worker ants after alighting briefly on the host. Embryonic development of the wasp occurred inside the serosal membrane or trophamnion of the egg in the abdomen of the ant host. First instar wasp larvae possessed a large head capsule with falcate mandibles, 11 ventral body lobes, an elongate tail and a dorsally located anus. Second instar larvae were unspecialized and lacked the large head capsule, elongate tail and paired ventral body lobes. Third instar larvae were hymenopteriform with a distinct head capsule. Cocoon formation and adult emergence is described. Observations on the percentage parasitism and altered behaviour of parasitized ants are presented. The association between neoneurine wasps and ants is a well-balanced system that has been in existence for at least 40 million years.

The consumption of a high-fat diet modifies both the morphology of the small intestine and experimentally tested effects of schistosomiasis mansoni. However, whether a schistosomiasis infection associated with a high-fat diet causes injury to the small intestine has never been investigated. Mice were fed either a high-fat or a standard-fat diet for 6 months and were then infected with Schistosoma mansoni cercariae. Physical characteristics of the intestinal tissue (mucosal thickness, small intestinal villi length and height, and abundance of goblet cells and enterocytes on the villous surface) and the distribution of granulomas along the intestinal segments and their developmental stage were measured at the time of sacrifice (9 or 17 weeks post-infection). The group fed a high-fat diet exhibited different granuloma stages, whereas the control group possessed only exudative granulomas. The chronically infected mice fed a high-fat diet exhibited higher granuloma and egg numbers than the acutely infected group. Exudative, exudative/exudative-productive and exudative-productive granulomas were present irrespective of diet. Computer-aided morphometric analysis confirmed that villus length, villus width, muscular height and submucosal height of the duodenal and jejunal segments were affected by diet and infection. In conclusion, a high-fat diet and infection had a significant impact on the small intestine morphology and morphometry among the animals tested.

The semi-slug, Parmarion martensi, is an intermediate host of the zoonotic nematode, Angiostrongylus cantonensis, the aetiological agent of neuroangiostrongyliasis or rat lungworm disease in humans. Rearing methods were developed for P. martensi to facilitate studies on nematode transmission and control. Parmarion martensi exhibited high survivorship when reared on a diet of dog food and fresh fruits and vegetables in temperature-controlled cabinets at 21.4°C, 98% relative humidity and 12:12 L:D cycle. Rearing containers were lined with moist paper towels for substrate and plastic pots were provided for hiding/resting and egg-laying. Under these conditions, time to first reproduction was 165.3 ± 12.3 days, fecundity was approximately 34.5 ± 7.8 eggs per adult, and hatch rate was 52.7 ± 3.2%. Survivorship post egg hatch was 86.2 ± 2.9% at 30 days (neonates had a mortality rate of about 14%) and 99% thereafter for up to a year. The demographics of laboratory-reared and wild-caught P. martensi were similar except for the weight of reproductive adults, which was significantly higher in laboratory-reared adults (4.0 ± 0.2 g) than in field-collected adults (1.5 ± 0.1 g).

During August and September 1909 I had an opportunity, thanks to the Government Grant Committee of the Royal Society, of making a fairly comprehensive examination of the parasites of fishes from the English Channel at the Marine Biological Laboratory, Plymouth. During that time nearly five hundred fishes, belonging to about 80 species, were dealt with and a very extensive collection of parasites made. A considerable number of species were obtained many of which are new to British waters but the number of absolutely new species amounted to very few. Of these I am describing here four of the most noteworthy, three of which appear to be of new generic type. A complete account of the investigations will be published later.

The effect of host age on the course of infection of Raillietina cesticillus in the chicken has been investigated. It was found that male hosts become resistant to the cestode with increasing age. This resistance manifests itself in an increased rate of destrobilization and consequent loss of scolices and in a decreased rate of growth of the worms. The cestodes are distributed over a greater length of intestine in old than in young birds.In female hosts age resistance develops more rapidly than in males until the birds are 84 days old and from this age onwards the manifestations of resistance decline.The possible factors responsible for age resistance to R. cesticillus are discussed.

The relationship between intensity and site of infection of Diorchis brevis, D. inflata and D. ransomi in Fulica atra from central Poland has been analysed; of 173 adult birds 152 (87·9%) were infected with one or more of these three species. From (1) the incidence of the three species (D. brevis, 59·5%; D. inflata, 69·9%; D. ransomi, 61·3%), (2) the high total incidence and high total intensity of infection (118·2 worms/bird) in hosts harbouring the three species concurrently and (3) the frequent co-occurrence of all three species in the same site in the host gut, it is concluded that there are no antagonistic interactions among these species. There are, however, some inter-dependencies between the number of parasites and the site occupied by particular species. In heavy infections there was a tendency to specific segregation and extension of the site of each species. This suggests the existence of inter- and intra-specific competition at higher densities of infection, regulating the spatial distribution of these parasites in the host gut.

Infection with digenetic trematodes causes an inhibition or complete cessation of fecundity in their intermediate hosts, freshwater snails. It has been demonstrated in the host–parasite combination Lymnaea stagnalis–Trichobilharzia ocellata that the action of the female gonadotropic hormones upon their target organs is inhibited by the peptide schistosomin. Schistosomin is produced in the central nervous system of the snail and released upon parasitic infection. In order to study the in vitro release of schistosomin, a bioassay was developed. Central nervous systems were incubated with either an acetic acid or a methanolic extract of larval stages of Trichobilharzia ocellata (miracidia, mother sporocysts, cercariae). The incubation media were chromatographed using HPLC and released schistosomin (-like material) was tested for bioactivity in the calfluxin bioassay. The in vitro release of schistosomin was only induced with a methanolic extract of cercariae. The nature of the cercarial factor is discussed.

The attachment of Eimeria tenella to its target cells as an obligatory intracellular pathogen is essential for the development of disease. Previous reports have established that other intracellular protozoa parasites have either fibronectin, an adhesion protein, or fibronectin receptors, both of which are involved in the interaction with the host cells. In this current research, studies have been undertaken to visualize a surface component that may be involved in the attachment of E. tenella to host cells. For this purpose, monoclonal antibodies, both anti-chicken and anti-human fibronectin, and also anti-chicken integrin were used. Our results show a fibronectin-like molecule with an apparent molecular weight of 110 kDa in mature schizonts and microgametes. Staining with serum directed against chicken integrin revealed immunoreactivity within mature schizonts. Both the fibronectin-like molecule and the integrin may play an important role in the parasite stage-cell interaction and the promotion of parasite uptake.

1. Two experiments are described investigating the effects of level of metabolism on (a) resistance to, and (b) recovery from, Notoedric scabies of rats. The progress and severity of the disease was measured by weekly counts of the number of lesions; the metabolic rate in some rats was raised by administration of iodinated casein and in others was depressed by methyl thiouracil.

2. In normal rats, the initial severe phase of the disease was followed by a partial recovery with survival of a smaller population of parasites.

3. This recovery process in established infestations was hastened by elevation and retarded by depression of the metabolic rate.

4. Resistance to the development of severe disease was enhanced by elevation and reduced by depression of the basal metabolic rate.

5. The level of the residual infestation, after the severe phase of the disease had passed, was also affected by the treatment, being decreased by the higher but increased by the lower metabolic rate.

Adult. Eyeless; camerostome without movable cheeks. In size (largest specimen 14 × 9 mm., Smallest 9 × 6 mm.), configuration, grooves, etc strongly recalling O. coriaceus, and the younger specimens have a suggestion of a similar dorsal pattern, but the whole surface is uniformly mammillate and the hood and the rather long palps are visible from the dorsal aspect. Discs in most specimens inconspicuous. Basis capituli about as broad as long, broadest posteriorly, where there are short, stiff, caducent bristles (? three pairs) directed outwardly. Hypostome lanceolate, with very small corona, followed by 2/2 well spaced teeth, about 6 per row. The leg armature, best understood from Text-fig. 1, is highly characteristic, the most striking feature being a prominent, rather sharp tooth on the proximal false articulation of the tarsus in legs I, II and III, but absent on tarsus IV. All the tarsi bear a prominent dorsal tooth near their distal ends. Legs I and II show characteristic prominences on other articles, notably the penultimate, which has a dorsal tooth at its basal and distal extremities.

The cuticular permeability of anhydrobiotic 4th-stage juveniles of Ditylenchus dipsaci decreases during rehydration, as indicated by staining with osmium tetroxide, the measurement of permeability coefficients by the rate of uptake of tritiated water from a HOH/C-inulin bathing solution and by an increased ability to slow down the rate of water loss and to survive subsequent desiccation. The initial decrease in permeability coefficient is rapid, suggesting a physical effect due to the rehydration of the cuticle, followed by a slower reduction over the subsequent 1–4 h which is dependent upon metabolic activity. The reestablishment of the permeability barrier is sensitive to metabolic inhibitors which affect enzyme activity and post-transcriptional protein synthesis. Sodium iodoacetamide was the only inhibitor which affected maintenance of the permeability barrier. An Arrhenius plot of changes in cuticular permeability with temperature indicated a sharp increase in permeability at 40–50°C and brief exposure to diethyl ether resulted in loss of the permeability barrier, suggesting that a superficial layer, probably the epicuticle, is responsible for controlling cuticular permeability.