Toxocara genettae sp.nov. and Toxocara sprenti sp.nov. from viverrid hosts in Africa and S.E. Asia respectively are described. Seven Toxocara spp. from viverrid hosts are differentiated. The writer proposes that Toxocara canarisi Puylaert, 1967, from a feline host, become a species inquirendae requiring further study.

Development of surface topography of cultured Schistosoma mansoni was followed in the cercariae, newly transformed and older schistosomula, and adults. Comparison with surface features of schistosomes from animal infections revealed no apparent differences in tegumental folding or morphogenesis, spines, sensory structures, or other components. Eggs produced by worm pairs grown in vitro were grossly abnormal, usually composed of loosely packed vitelline granules and lacking a shell.

Previously we reported the isolation of several Escherichia coli clones expressing fragments of Taenia taeniaeformis antigens as β-galactosidase fused proteins (Bowtell, Saint, Rickard & Mitchell, 1984). Here we describe the isolation of additional antigen-expressing clones from a larval cDNA library and the assignment of these clones to 7 antigen families. These were isolated with a polyspecific rabbit antiserum raised to the oncosphere. Since this serum was capable of reacting with a large number of antigens, it was important to develop techniques for rapidly determining the identity of the native T. taeniaeformis molecule corresponding to a cloned antigen gene. These included active immunization of rabbits with fused proteins and several techniques involving affinity purification on immobilized fused proteins. The reactivity of the antigen-positive clones with sera from humans infected with related parasites was also assessed. Finally, immunization of mice with several fused proteins failed to protect against subsequent infection, although antigens previously identified as candidate host-protective antigens (Bowtell, Mitchell, Anders, Lightowlers & Rickard, 1983) have yet to be identified in the expression library.

Females of Hammerschmidtiella diesingi can survive in the hind-gut of moulting Blatta orientalis. After a period of shrinkage they recover their normal length within 24 hr. in 0·2 and 0·3 m sodium chloride and in 50% sea water, but not in hypotonic media or in hypertonic sucrose. Females of H. diesingi, which have regained their original length in hypertonic media, swell when placed in normally isotonic media; a similar phenomenon occurs with nematodes taken from moulting cockroaches.

The sporozoites of Eimeria acervulina and E. maxima when injected into the caeca of chickens fail to produce infections. Sporozoites of E. mivati injected into the caeca invade the walls and the life-cycle is completed. These observations are discussed in their relation to the fate of sporozoites injected into the allantois of chick embryos. The possible use of these techniques in confirming the identity of a species is discussed.

We wish to thank Mr B. J. Millard for technical assistance with the preparation of the sporozoites.

Five tame monkeys (3 Macacus sinicus and 2 M. rhesus) have been treated with emetine bismuthous iodide per os, in order to study the effects of the alkaloid upon their intestinal amoebae (and other protozoa).

These monkeys were originally infected with Entamoeba histolytica (large and small strains), Entamoeba coli, Endolimax nana, Enteromonas (= Tricercomonas), and Giardia. Treatment with emetine ultimately eradicated the E. histolytica infections from four out of five animals, but did not remove any of their other intestinal protozoa.

It has been found necessary to administer 60 mg. of emetine bismuthous iodide daily for about a week to a macaque weighing about 5 kg. in order to eradicate an infection with E. histolytica. Such dosage was toxic to four of the five monkeys used.

The general conclusion drawn is that emetine affects the various intestinal protozoa of M. sinicus and M. rhesus exactly as it does the comparable species in man; and it is suggested that macaques can therefore be utilized—if similar methods be employed—in place of men in future chemotherapeutic experiments directed towards the discovery of remedies for human amoebic dysentery.

Although schistosomes were thought to be one of the few parasitic helminths that do not produce succinate via fumarate reduction, it was recently demonstrated that sporocysts of Schistosoma mansoni produce, under certain conditions, succinate in addition to lactate. This succinate production was only observed when the respiratory chain activity of the sporocysts was inhibited, which suggested that succinate is produced by fumarate reduction. In this report the presence of essential components for fumarate reduction was investigated in various stages of S. mansoni and it was shown that, in contrast to adults, sporocysts contained a substantial amount of rhodoquinone which is essential for efficient fumarate reduction in eukaryotes. This rhodoquinone was not made by modification of ubiquinone obtained from the host, but was synthesized de novo. Furthermore, it was shown that complex II of the electron-transport chain in schistosomes has the kinetic properties of a dedicated fumarate reductase instead of those of a succinate dehydrogenase. The presence of such an enzyme, together with the substantial amounts of rhodoquinone, shows that in S. mansoni sporocysts succinate is produced via fumarate reduction. Therefore, the energy metabolism of schistosomes does not differ in principle from most other parasitic helminths, which are known to rely heavily on fumarate reduction.

Rats were treated with betamethasone at different stages of infection with Strongyloides ratti. Treatment caused a diminution in the number of adult worms recovered but this residual population was not expelled as were worms from untreated rats. If treatment was started after expulsion had already begun adult worm numbers increased – suggesting that auto-infection occurred. Treatment throughout a primary infection prevented the development of an immune response which expelled, or killed, a challenge infection. Treatment, just before and just after challenge, prevented the expulsion of the challenge infection. Worm expulsion up to day 35 was prevented by treating rats with betamethasone 4, 6, 8 and 10 days after infection.

The effects of exposure to infective larvae on the antibody response to a cocktail of specific recombinant antigens of Onchocerca volvulus and to a worm extract were evaluated by comparing the responses of individuals from a vector controlled area with those from an area of continuing transmission by ELISA. Individuals from the vector controlled areas were found to have reduced responses to both antigen preparations. Amicrofilerdermic (mf–) individuals from the area of vector control exhibited significantly lower total and subclass IgG responses to the worm extract. In contrast, the responses to the cocktail of specific recombinants were significantly reduced in individuals from the area of vector control who were still microfilerdermia positive (mf+). The distribution of IgG subclass specific responses was similar to both antigen preparations, both dominated by the IgG4 and IgG1 subclasses. IgG1 responses to the worm extract remained elevated in the vector controlled individuals but IgG4 was significantly reduced in the mf – individuals. Both subclasses reflected the total IgG response to the cocktail of recombinants and were significantly reduced in individuals from the vector controlled area, when compared to individuals from the hyperendemic area. IgG1 responses to the cocktail of recombinants are significantly lower than IgG4 in all individuals and virtually absent in individuals from the vector-controlled area. Measuring total IgG and IgG4 is more sensitive than IgG1 in detecting infection, 100 or 97% respectively, but they remain elevated in the individuals from the vector controlled areas even after 8–10 years interruption of transmission. These results have important implications for the serological monitoring of control programmes in individuals who have previously been infected.

The monogenean Protopolystoma xenopodis has been established in Wales for >40 years following introduction with Xenopus laevis from South Africa. This provides an experimental system for determining constraints affecting introduced species in novel environments. Parasite development post-infection was followed at 15, 20 and 25°C for 15 weeks and at 10°C for ⩾1 year and correlated with temperatures recorded in Wales. Development was slowed/arrested at ⩽10°C which reflects habitat conditions for >6 months/year. There was wide variation in growth at constant temperature (body size differing by >10 times) potentially attributable in part to genotype-specific host-parasite interactions. Parasite density had no effect on size but host sex did: worms in males were 1·8 times larger than in females. Minimum time to patency was 51 days at 25°C and 73 days at 20°C although some infections were still not patent at both temperatures by 105 days p.i. In Wales, fastest developing infections may mature within one summer (about 12 weeks), possibly accelerated by movements of hosts into warmer surface waters. Otherwise, development slows/stops in October–April, delaying patency to about 1 year p.i., while wide variation in developmental rates may impose delays of 2 years in some primary infections and even longer in secondary infections.

The behaviour of the sand martin flea Ceratophyllus styx jordani Smit was studied in relation to its ecology.

The cocooned resting imago in the host's old nest is the main over-wintering stage. Mechanical disturbance of the cocoons by the exploratory habits of the newly returned sand martins elicits emergence of the imagines in spring. The seasonal rise in temperature is not, by itself, important in causing emergence, as it does not become effective until many weeks after the martins have returned, by which time undisturbed fleas are likely to have died inside their cocoons.

When the imagines break out of their cocoons they are negatively photo-tactic, but become positively phototactic within 24 h. This response takes them outwards along the martin's disused burrow until the increasing intensity of light reduces their activity so that they aggregate on the lower lip of the entrance. Positive phototaxis prevents them dispersing downwards from the entrance.

Periodically the fleas bury themselves in sand; this response may function for water conservation. The proportion buried is greatest at night.

The sand martin's habit of hovering close to a succession of entrances renders it accessible to the fleas, whose main host-finding response is an outward jump from the burrow entrance. This jump is released by a sudden decrease in light intensity and is directed towards dark objects. Vibration and air currents do not release jumping.

Dispersal from aggregations in disused burrows may occur by transport on the host, or by spontaneous horizontal emigration along the cliff face, or by falling after an unsuccessful host-finding jump. Fleas which have fallen become negatively geotactic and positively anemotactic. Fleas wandering on the cliff face visually detect burrow entrances up to 30 cm away, and turn towards them. Preference for moister sand and, possibly, a negative phototactic response, may induce the fleas to remain in newly found burrows.

Small aggregations of fleas also occur at the entrances of burrows currently in use by martins. Fleas circulate between the entrance and nest chamber of these burrows, until the martin begins to incubate its eggs. The entrance aggregation then disappears and fleas accumulate in the nest chamber. There is some interchange of fleas between infested burrows in the martin's pre-incubation period.

The general pattern of behaviour resembles that of C. gallinae. Behavioural differences between the two species are related to the ecology of their hosts. C. styx is adapted to dispersal and host finding in its host's breeding site, whereas C. gallinae is adapted to reach foraging birds. This difference partly accounts for the narrow host specificity of C. styx and the wide host range of C. gallinae.

My grateful thanks are due to Chris. Mead and Giles Pepler for information on sand martins' behaviour and migratory arrival. I would also like to thank Brian Little, who introduced me to several colonies in the Tyne Valley. The valuable advice of the Hon. Miriam Rothschild and Dr E. T. Burtt is especially acknowledged.

Pseudodiplorchis americanus has an extremely brief opportunity for transmission, restricted to less than 24 h in the year when the host (Scaphiopus couchii) enters water to breed. This strict annual cycle means that invading worms have 1 year to complete reproductive development. Despite this, a large proportion of the parasite suprapopulation is not prepared for transmission at the time of host breeding. The present study correlates detailed soil temperatures for one field site in S.E. Arizona, spanning 3·5 years, with laboratory data on parasite growth and reproductive development at a series of controlled temperatures. Development is totally inhibited at 16°C. Optimal growth and development occurs at 25°C and is slower at both 20°C and a diurnal cycle fluctuating between 20 and 34°C (mean 27°C) (simulating summer temperatures experienced by host and parasite). The effective period for accumulation of infective stages by P. americanus in any one season varies according to the timing of the summer rains in consecutive years. Between 1985 and 1988, the interval between host breedings varied from 11 to 13 months and the period when temperatures were above 20°C varied from 4 to 5·5 months per year. Since the first month post-infection (p.i.) consists of pre-reproductive development, first-year worms have only 3–4·5 months to produce infective larvae. In the shortest seasons, these worms may not be able to complete reproductive preparation in time for the first opportunity for transmission. In different parts of the geographical distribution of S. couchii, different cycles of temperature, rainfall and host breeding occur; varying temperature regimes represent an important abiotic control of P. americanus reproductive biology and transmission.

Since November 1906 I have had in the animal house attached to the Bacteriological Laboratory, a rather large female Macacus pileatus (No. 47). This monkey, which had been bought from a villager, had never been used for any experiment: it was kept in the same cage with a monkey inoculated with yas. In October 1907 the monkey, which so for had been in good health, began to lose appetite, and looked somewhat ill: nevertheless the animal continued to jump about in the cage and play with its compantion till a short time before death, on 5. xi. 07. The monkey never had any diarrhoea, and I thought it might have died from a peculiar form of malaria, extremely common in Ceylon monkeys.

Immunity to microbial infections is well understood; however, information regarding the immunity to parasitic multicellular organisms remains lacking. To understand innate host cellular immunity to nematodes, we compared the cellular response of the greater wax moth (Galleria mellonella) larvae against the non-parasitic, bacterial-feeding nematode Caenorhabditis elegans and pathogenic nematode Heterorhabditis bacteriophora. When intact first-instar or dauer larvae of C. elegans were injected into a G. mellonella larva, most of the nematodes were alive and not confined by the surrounding reaction by insect haemocytes (encapsulation), similarly as the pathogenic nematode, whereas most of the heat-killed nematodes of both species were severely encapsulated by 24 h after inoculation. Other non-parasitic nematodes were also not encapsulated. Surprisingly, C. elegans injected into the insect haemocoel grew and propagated in the live insect, resulting in death of the host insect. Our results suggest that C. elegans has some basic mechanisms to evade immunity of G. mellonenlla and grow in the haemocoel.

1. Annual fluctuations in the percentage of L. saxatilis infected by Cercaria ubiquitoides at Whitstable, Kent, are described.

2. Females are consistently more frequently parasitized than males.

3. At higher shore stations more L. saxatilis are parasitized than at lower shore stations.

4. Possible reasons for the above phenomena are discussed together with the relationship between trematode infection and the reproductive activity of L. saxatilis.

Eimeria maxima has been used as a model apicomplexan parasite to study sexual stage development and oocyst wall formation. A complete understanding of the wall's biochemical and biophysical properties is of great interest in research on all apicomplexan parasites. Purified gametocytes, zygotes and oocysts were analysed by three-dimensional confocal microscopy, and wide-field fluorescent microscopy was used to investigate the appearance and spatial organization of the 2 types of wall-forming bodies (WFBs). In addition, a variety of staining procedures and immunoassays were used to assess the biosynthesis, metabolic activity, intactness and molecular composition of the WFBs in situ. WFBs were extracted from gametocytes/zygotes and their composition was assessed by microscopy and SDS-PAGE analysis. It was concluded that isolated gametocytes are intact and metabolically active. Additionally, it was observed that the Type 1 WFBs are aligned at the periphery of the parasite and fuse together producing neutral lipid rich patches that appear to be inserted into the space between 2 parasite-specific membranes. Finally, it was shown that the WFBs extracted from purified gametocytes had the same shape, size and staining properties as those observed in situ, and contained the major glycoprotein antigens known to be present in these organelles.

The modified Kato technique has the advantages of reproducibility, simplicity and economy: the disadvantage is that it cannot be used in conjunction with traditional faecal preservatives. Sodium azide has been evaluated as a preservative for human faeces for subsequent Kato analysis. More than 400 faecal samples (from normal and malnourished children, and from mixed-age participants in a field survey of the Turks and Caicos Islands) were each mixed with 2–5 mg of sodium azide powder and stored in 2 or 4 ml autoanalyser cups at ambient tropical temperature. At intervals up to 30 weeks, aliquots were prepared for Kato analysis. Trichuris trichiura, Ascaris lumbricoides and Necator americanus eggs were well preserved without degenerative or developmental changes in morphology. Quantitative analyses of 18 samples indicated that the mean egg count/sample did not change significantly after storage for 1, 2, 4, 8, 12 and 16 weeks in preservative. The use of azide preservative extends the applications of the Kato technique to field and clinical studies in which delays may occur between specimen collection and examination. The direct costs of azide preservation are substantially lower than for traditional methods and the preserved specimens are more compact and resistant to leakage.

The migration and development of Sanguinicola inermis in carp fingerlings were investigated by quantitative analysis of serial sections of fish and examination of flukes from hosts up to 90 days p.i. Cercariae penetrated through the epidermis and migrated through connective tissue and muscle to establish in the blood system and commence egg production within 28 days p.i. Most flukes established in the ventral blood system and released eggs which accumulated in gill epithelial tissue. A minority of flukes inhabited dorsal blood vessels and shed eggs which lodged in connective tissue and visceral sites. Maximum life-span of the parasite is between 56 and 70 days p.i. and egg production peaked at day 42 p.i.

In and around the British Isles, three biologically specialized strains of the fish acanthocephalan Pomphorhynchus laevis have been recognized, each differing in geographical distribution and both final and intermediate host utilization. Six restriction endonuclease digests of the genomic DNA of the English freshwater and marine strains were compared by genomic cross-hybridization using the randomly sheared and radio-isotope labelled genomic DNA of freshwater P. laevis, and also by using a heterologous isotope labelled ribosomal DNA probe. Autoradiographs of hybridized Southern blots provided evidence for considerable homogeneity in the total repetitive DNA of the two strains as well as some preliminary evidence for possible restriction fragment length polymorphisms using EcoR I and Pvu II.

Significant suppression in the incidence of cyclical development of Trypanosonia congolense, T. vivax and T. brucei occurred in Glossina morsitans centralis maintained on goats immunized with in vitro-propagated uncoated forms of T. congolense, T. vivax and T. brucei, respectively. This was observed when tsetse given a T. congolense-infected feed were subsequently maintained on uninfected immunized goats and also when uninfected tsetse were fed on immunized goats infected with T. congolense, T. vivax and T. brucei. Suppression of infection rates in tsetse was trypanosome species specific, but was independent of the trypanosome stock used for immunization of goats. These findings were reflected in antibody responses to uncoated trypanosomes, as measured by immunofluorescence and the solid-phase immuno radiometric binding assay. Thus, antibody from goats immunized with uncoated trypano somes of one species exhibited minimal reactivity with uncoated forms of other species of trypanosomes, but showed high levels of activity with uncoated forms of the same or unrelated stocks of the same species. However, in view of the range of hosts upon which tsetse feed, it is open to question whether the use of a vaccine which suppresses trypanosome infection rates in tsetse would have any significant effect in the field.