1. Permanent and temporary pastures were examined using a modification of Taylor's method.

2. The goodness of fit of Neyman's Contagious Distribution Type A when applied to larvae on pastures is discussed.

3. Examination of permanent pastures over a period of 3 years showed that the difference in time of maximum infestation was greater between fields in the same year than between years for the same field.

4. Counts made on pastures where disease had occurred showed reasonably close agreement with Taylor's estimate.

5. No larvae were detected on fields after ploughing and reseeding.

6. The number of larvae per lb. of herbage on reseeded pastures was low, but the growth of grass masked the fact that the total population was relatively high at the end of the season.

Rotylenchulus reniformis, Anguina agrostis and Meloidogyne javanica respond differently to gradients of chemical attractants. In chemotaxis assays performed on agarose plates, R. reniformis L2 larvae oriented their movement to several common inorganic salts, cyclic AMP and AMP, as well as to germinated host plant seeds. M. javanica L2 larvae were attracted to germinated seeds, but not to the salts tested, and A. agrostis dauer larvae were not strongly attracted to any of 12 different tested agents, including host root or shoot tips. Attraction of R. reniformis to salts was measured by comparing different pairwise combinations of ions at equivalent concentrations. The indicated order of attractiveness was: Cl− > Na+ > C2H3O2− > Mg2+, NH4+, SO42−. The least attractive salts, (NH4)2 SO4 and MgSO4, were weakly attractive at an orientation threshold of 1 mm, whereas the most attractive salt, MgCl2, was strongly attractive at a threshold of 0·2 mM Cl−. 3′, 5′ cyclic AMP was strongly attractive at a threshold of 0·05 mM, whereas 5′-AMP was a weak attractant. Some of these responses may affect the distribution of R. reniformis in its natural environment.

The uptake of radioactive pyrimethamine by a sensitive and a resistant strain of Plasmodium falciparum, the metabolic fate of pyrimethamine inside these parasites and the kinetic properties of dihydrofolate reductase (DHFR) from both strains have been studied. Uptake of the drug was identical in both strains and no metabolite of pyrimethamine was found in either strain. DHFR from the resistant strain was 300 times less sensitive to inhibition by pyrimethamine than the enzyme from the sensitive strain, while the Michaelis constant for dihydrofolate remained unchanged and inhibition was competitive in both cases. Altered properties of plasmodial DHFR are apparently the only mechanism responsible for pyrimethamine resistance in the strain of Plasmodium falciparum studied.

It was found that interference contrast microscopy gave good morphological differentiation of the living and intact salivary glands from adult ixodid ticks, Rhipicephalus appendiculatus and Amblyomrna variegatum, removed by dissection. In many cases the individual cell types of the acini could be recognized. When the salivary glands of infected adult ticks were examined Theileria parasites were detected. Theileria parva, T. taurotragi and T. mutans could be detected in the salivary glands after they reached the mature secondary sporoblast stage achieved even in unfed ticks. Parasites were detected only in type III acini. The morphology of tertiary sporoblasts and sporozoites of these Theileria spp. was clearly recognized in feeding ticks. Sporozoites of T. parva proved to be infective to cattle and to peripheral blood leucocytes of cattle in vitro after interference contrast examination. Interference contrast examination of living salivary glands was used for selection of salivary glands with high infections of T. parva sporozoites and the sporozoites could be separated in large numbers from these salivary glands. Using this technique it appeared possible to clone Theileria parasites from salivary glands with 1 infected acinus.

F1, Quackenbush (Q) × Wild (W) Mus musculus were assayed and selected for their level of immunity to secondary infections with 100 Nematospiroides dubius using faecal parasite egg counts. A significant positive linear correlation was found between the number of parasite eggs voided in the faeces and the number of N. dubius recovered after secondary infections in mice. Selection for immunity was not influenced by the conformation of the mice. High (H) and low (L) responder colonies together with a randomly (Rd) bred colony of mice were established over 5 generations. Adaptive immunity was more efficacious in protecting female than male mice and appeared to be controlled by a few dominant genes; the heritability (h2) of the trait was estimated at 0·56 for the parental stock and 0·55 for the F5 Rd colony and the realized heritability was 0·49. Higher anti-N. dubius antibody titres were detected in H than L mice. H mice harboured fewer and less fecund parasites than Rd colony mice; L mice had more worms with greater fecundities than Rd mice. The levels of primary infection in H and L mice related to the levels developed after secondary infection from F4. This suggested at least partial linkage of genes controlling innate with genes controlling adaptive immunity against N. dubius.

The European earwig (Forficula auricularia L.) accidentally introduced some years ago into the United States, is now abundant in several of the Western and at least one of the Eastern States; it has become established also in New Zealand, where, according to Tillyard, it has become a major pest, eating into peaches, nectarines, and apricots and rendering them useless for sale.

For normal development of the parasites, Eimeria acervulina and E. tenella in the chicken, dietary thiamine, riboflavin, biotin, nicotinic acid and folic acid are required. E. acervulina required thiamine for second schizogony and sporulation; riboflavin for first schizogony and possibly gametogony, biotin for the development of the sporozoites/trophozoites and for gametogony, and nicotinic acid for schizogony and gametogony. E. tenella required thiamine and riboflavin for gametogony; biotin for first schizogony; and nicotinic acid for second schizogony.

Cystosporogenes operophterae, a microsporidian parasite of the winter moth, Operophera brumata, was cultured in a Spodoptera frugiperda cell line. The infected cultures were achieved by addition of haemolymph from larvae infected with C. operophterae. The infection rates for the cell line ranged from 80 to 95% after incubation for 10 days at 25 or 20 °C. There was no development in cultures incubated at 30 °C. Light and electron microscopy were used to observe the development of C. operophterae in vitro.

Groups of ten cattle were exposed to 0, 40 and 400 adult Rhipicephalus appendiculatus feeding once a week for 24 weeks. Although no differences in cumulative percentage weight gain were found at the end of the experiment, animals free of ticks performed better during the first 12 weeks. A marked recovery of the 400-tick group was recorded during weeks 13–24 and after ticks were removed. Haemoglobin and packed cell volume values were lowered in tick-infested animals but no clear trends were observed in red and white blood cells. No differences between the percentages of ticks feeding in the 2 tick-infested groups on day 2 were observed but higher numbers of females were feeding on the 40-tick group on day 5. More ticks were found on day 5 after tick application to the cattle during weeks 1–6 than in the rest of the experiment. Significant correlations were found between lymph node enlargement and ear damage when they were tested against tick load. R. appendiculatus nymphs feeding on the formerly tick-infested cattle were fewer, lighter and engorged in a shorter time than those on the control animals. The possible causes for the reduction in ticks feeding, the changes in cattle weights, blood composition and development of host resistance are discussed.

In the present paper seven species of cymothoid isopods parasitic on the marine fishes of the Kerala coast are described. A preliminary diagnosis of three of them was published earlier (Pillai, 1954). Full descriptions of all the species are given below. The larval stages described were in all cases taken from the brood pouch. The present work forms part of a thesis for which the author was awarded the Ph.D. Degree by the Kerala University.

The human hookworm Necator americanus appears to have evolved a number of complementary strategies to overcome the host's haemostatic processes. These include the inhibition of blood coagulation, platelet aggregation and mediator release, and the secretion of fibrinogenolytic enzymes. These strategies presumably allow the parasite to establish the chronic infections so often documented in human populations.

Host selection among humans by Anopheles punctulatus was studied in an area of Papua New Guinea endemic for malaria and filariasis. Blood films were made from the stomach contents of freshly engorged mosquitoes found resting on the walls of houses in which the parasite status of the occupants was known. Engorgement rates on humans were non-random but could not be consistently related to the parasite status of individuals in the houses for either malaria or filaria. In some households, anophelines preferentially fed on parasitaemic individuals while in other households aparasitaemic individuals were significantly more often selected. This finding is believed to reflect the fact that malaria and filarial infections in this endemic area are predominantly asymptomatic. There were no significant differences in axillary temperatures between malaria or microfilariae positive or negative individuals.

The fine structure of egg shells of four different genera belonging to the order Tylenchida has been examined. The species examined were Meloidogyne javanica, Rotylenchulus reniformis, Tylenchulus semipenetrans and Pratylenchus minyus. They are all similar in their basic structure, being composed of vitelline membrane, chitin and lipid layers, but there is considerable variability in the thickness of these layers.

We have retained the conventional nomenclature because of its convenience, but it is clear that these layers have a variety of chemical components. However, they do appear to contain the compounds from which they take their name. Thus chitin occurs in the chitin layer, and lipid in the lipid layer. The latter is removed by the technique used in isolating the shell from the egg. Chemical analysis of the hydrolysis products of these shells has revealed a high (35 %) proline content which appears to be a characteristic of those nematode egg shells which have been examined so far. These analyses and treatment with enzymes indicate that the chitin layer is a chitin–protein complex.

Experiments on the permeability of eggs of M. javanica at different temperatures indicate that changes in permeability are not due to the melting of a single lipid with a distinct melting point as had been thought in the past. We have found that Arrhenius activation energies calculated from the two slopes of an Arrhenius plot were 17·8 kcal/mol and 43·0 kcal/mol respectively, the transition from one to the other taking place at 62°C. We think that these changes are due to changes in the properties of lipoprotein membranes in the lipid layer. These membranes appear to be of paramount importance in controlling the permeability of the nematode egg shell.

The object of this paper is to develop the ideas put forward in previous publications (Duke, 1919, 1921).

A cross-sectional study of bancroftian filariasis was conducted in 2 adjacent communities, Mvumoni and Kilore in Muhaka, Kwale District. Wuchereria bancrofti infection, clinical manifestations and anti-filarial IgG responsiveness were determined before the long rains, a time coinciding with a low transmission season. The prevalence of microfilaraemia increased gradually with age and was significantly higher in Kilore (24%) than in Mvumoni (6·3%, P<0·001). Similarly, the prevalence of antigenaemia increased with age and also was significantly higher in Kilore, 48·9% than in Mvumoni, 20·5% (P<0·001). Hydrocele, funiculitis, lymphangitis and lymphadenitis were also significantly more common in Kilore than in Mvumoni. In comparing the 2 communities, levels of IgG4 responsiveness in antigen-positive persons were higher in Kilore than Mvumoni (P=0·034), but this was related to higher antigen loads in persons in Kilore than in Mvumoni. In antigen-negative persons, anti-filarial antibodies of 3 IgG isotypes were significantly higher in Kilore than Mvumoni (P<0·001, for IgG1, IgG2, IgG4). These results emphasize the highly focal nature of bancroftian filariasis in this setting and demonstrate that anti-filarial antibody levels are related to transmission intensity.

We cloned and expressed Echinostoma caproni HSP70 in Escherichia coli. This molecule presents an open reading frame (ORF) of 655 amino acids, and a theoretical molecular weight of 71 kDa. E. caproni HSP70 protein showed a high homology to other helminth molecules, major differences being located in the C-terminal region of the molecule, with a hydrophobic portion. Studies of protein and messenger RNA (mRNA) expression revealed a distinct pattern, depending on the host (low- or high-compatible). Specific polyclonal antisera raised against the recombinant protein expressed in Escherichia coli demonstrated its selective presence in excretory/secretory products (ESP) of adult parasites obtained from high-compatible hosts. Immunological studies showed clearly the association of HSP70 with the parasite surface and other structures, including eggs.

Parasites of the genera Plasmodium and Haemoproteus (Apicomplexa: Haemosporida) are a diverse group of pathogens that infect birds nearly worldwide. Despite their ubiquity, the ecological and evolutionary factors that shape the diversity and distribution of these protozoan parasites among avian communities and geographic regions are poorly understood. Based on a survey throughout the Neotropics of the haemosporidian parasites infecting manakins (Pipridae), a family of Passerine birds endemic to this region, we asked whether host relatedness, ecological similarity and geographic proximity structure parasite turnover between manakin species and local manakin assemblages. We used molecular methods to screen 1343 individuals of 30 manakin species for the presence of parasites. We found no significant correlations between manakin parasite lineage turnover and both manakin species turnover and geographic distance. Climate differences, species turnover in the larger bird community and parasite lineage turnover in non-manakin hosts did not correlate with manakin parasite lineage turnover. We also found no evidence that manakin parasite lineage turnover among host species correlates with range overlap and genetic divergence among hosts. Our analyses indicate that host switching (turnover among host species) and dispersal (turnover among locations) of haemosporidian parasites in manakins are not constrained at this scale.

The present study was designated to ascertain the anthelmintic activity of the rhizomes of Paris polyphylla and to isolate and characterize the active constituents. The methanol extract from rhizomes of P. polyphylla showed significant anthelmintic activity against Dactylogyrus intermedius with the median effective concentration (EC50) 22·5 mg L−1. Based on this finding, the methanol extract was fractionated by silica gel column chromatography in a bioassay-guided fractionation yielding 2 bioactive compounds, the structures of these compounds were elucidated as formosanin C and polyphyllin VII. The in vivo tests revealed that formosanin C and polyphyllin VII were significantly effective against D. intermedius with EC50 values of 0·6 and 1·2 mg L−1, respectively. The acute toxicities (LC50) of formosanin C and polyphyllin VII for grass carp were 2·8 and 2·9 mg L−1, respectively. The overall results provide important information for the potential application of formosanin C and polyphyllin VII in the therapy of serious infection caused by D. intermedius.

During the cyst formation of Trichinella spiralis, the infected muscle cell undergoes basophilic change and apoptosis, which results in nurse cell formation. This study revealed expression kinetics of some apoptosis genes such as p53 and its closely related genes (tumor suppressor genes p53, p53; mouse double minute 2, MDM2; cyclin-dependent kinase inhibitor p21, p21waf). RT-PCR (reverse transcription polymerase chain reaction) results showed that these genes were temporarily expressed in the infected muscles during the cyst formation period, but not in normal muscles (or very low if any), which suggested the involvement of these apoptosis genes in the nurse cell formation. Cysts and neighbouring muscle cells were separately collected and RT-PCR was performed, which suggested that p53 was expressed in the cysts. An immunocytochemical study showed that p53 was expressed in the nucleoplasm of basophilic cell in the cyst and Trichinella larvae, which suggested involvement of these apoptosis genes in the nurse cell formation. The same p53 expression kinetic study was performed on p53 knockout mice. The knockout mice did not express p53 genes, but expressed the other apoptosis genes in the same kinetics with only minor exceptions, suggesting that the expressions of these genes during the cyst formation were more or less p53-independent. There were no differences in the number and morphology of the cysts between the knockout mice and wild type mice. Thus apoptosis seen during the Trichinella cyst formation can be operated in the presence or absence of p53.

Egg-laying patterns and egg production in Heteraxine heterocerca from the gills and Benedenia seriolae from the skin of Japanese yellowtail Seriola quinqueradiata in Japan were investigated in vivo. Eggs were collected every 3 h from sexually mature H. heterocerca and B. seriolae infecting 3 S. quinqueradiata kept individually over 3 consecutive days and exposed to alternating periods of illumination and darkness (LD 12:12; light on 06.00, light off 18.00) and maintained at 23·8±0·1°C and 35 ppt salinity. A well-defined egg-laying rhythm was demonstrated for H. heterocerca while B. seriolae was shown to release eggs continuously. A total of 114 000 H. heterocerca eggs was collected and of these, 45·4 (42·5–49·9)% were collected during the first 3 h period following dark at 18.00 h. A total of 662 857 B. seriolae eggs was collected and these were distributed over each 3 h period ranging from 11·1 to 14·1% of the daily egg output. All eggs extracted from the uterus of each H. heterocerca were joined together forming an ‘egg-string’. The contrasting egg-laying patterns of H. heterocerca and B. seriolae suggest that each species makes use of a different infection strategy to infect the same host species, S. quinqueradiata.