Observations on 5 different isolates of Eimeria stiedai from pure infections in laboratory-reared rabbits have confirmed the presence of an oocyst residuum. This structure was seen in 89–100% of the oocysts in cultures prepared both from the liver and from the faeces at different times during the patent period. The residuum consisted of 1–7 or more granules situated centrally in the oocyst and partially concealed by 4 sporocysts. The differential diagnosis of E. stiedai and E. coecicola is discussed.

The activity patterns of the cercariae of Transversotrema patialense have been examined by monitoring the behaviour of individual larvae. Records of three different behavioural modes, namely active, tail–first swimming, passive dropping and resting periods were made separately. The age- and temperature–dependence of the activity patterns during the spontaneously active life of the cercariae were examined and estimates made of the absolute speeds of swimming and dropping. Through the temperature range 25–32° C, the spontaneously active life of cercariae declined from about 18 h to about 6 h. Within this interval, after an initial period of high activity rates, a gradual decline in activity followed. The decline was a result of a decreasing frequency of swimming events rather than any change in the durations of such events. The neural control and energetic significance of the cercarial activity patterns are discussed.

This study compares papillae distribution in seven microphallid cercariae of the genera Microphallus and Maritrema. Certain papillae or groups of papillae have generic, supra–generic or specific significance. Microphallidae are characterized by the absence of C I cycle and of dorsal P II and P III, the presence of one C II1 and one C II2, of four mediodorsal A I D papillae and of two horizontal papillae on the tail. The number and disposition of the papillae at the front of the body (peribuccal and anterodorsal A I D and St DL) and at the back (P cycles) have a generic significance. The number and disposition of the papillae in the middle of the body (A and M cycles) have a specific significance.

Interference microscopy has been used to study the rate at which water enters and is lost from larval and adult stages of Ditylenchus dipsaci and D. myceliophagus. It is shown that the cuticle of the dry nematode, irrespective of stage, is completely permeable to water. In contrast, marked intra– and interspecific differences were found in the rate at which stages dry at 0 and 50% relative humidity. All stages of D. myceliophagus dry very rapidly: in this species, death, as a consequence of severe desiccation, appears to be linked to a lack of any marked ability to control water loss. For D. dipsaci, those stages known to survive desiccation will appear to be the slower dryers. In general, the “order of performance” in slowing the rate of drying is the same as the order previously found for survival of desiccation. Both the 4th– and, to a lesser extent, the 3rd–stage larvae of D. dipsaci show evidence of an intrinsic ability to control water loss.

An analysis of the drying curve for 4th–stage larvae of D. dipsaci supports the indications of interference photographs that the rate of drying is slowed by a decrease in permeability of the drying cuticle.

Vacuum desiccation studies further demonstrate the remarkable ability of the 4th–stage larva of D. dipsaci to control its rate of drying. The survival of 4th– and 3rd–stage larvae of D. dipsaci is diminished by very rapid drying, and the survival of other stages of this species and larval and adult stages of D. myceliophagus is precluded. The decrease in survival of the 4th–stage larvae of D. dipsaci is shown to be associated with a more rapid rate of water loss.

Primary immune expulsion of Trichuris muris was markedly delayed by concurrent infection with Nematospiroides dubius. Maximum delay of expulsion was dependent on size and timing of N. dubius infection relative to T. muris infection. In NIH mice infection with 400 N. dubius larvae immediately before or after T. muris infection was found to be most effective in suppressing expulsion. Infection on day 8 of T. muris infection, when mice are sensitized to T. muris, also impaired expulsion. From this evidence it is suggested that the larvae of N. dubius are immunosuppressive and that the efferent role of the immune response to T. muris is inhibited. The results are discussed in terms of non-specific immunosuppression and their relevance to the tropical disease situation is emphasized.

The rapid elimination of the intestinal phase of Trichinella spiralis in NIH mice is associated with progressive inflammation of the intestinal tract. The non-specific effects of this inflammation were studied in. mice concurrently infected with an unrelated parasite, Hymenolepis diminuta, which does not stimulate a visible inflammatory response but is also immunologically rejected by this strain of mice.

It was demonstrated that the rejection phase of T. spiralis infection had a marked effect upon the growth and survival of H. diminuta,. The cestode either failed to establish or to grow; if the worms were already strobilate when inflammation developed then destrobilation occurred. There was no cross–immunity between the parasites, nor was the interaction a direct consequence of inter–specific competition.

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.

A simple technique for the maintenance in vitro of mature Schistosoma mansoni is described and critically assessed at the ultrastructural level. Females were cultured for 4–6 days with no apparent ultrastructural change, but after this period changes appeared in the cells of the ovary and vitelline gland. At a later stage (10–12 days) lipid bodies appeared in the parenchyma cells. These changes occurred in worms which were active, paired with males and were egg–laying. Thus the activity, pairing behaviour and egg–laying characteristics are not adequate to reveal the true morphological condition and presumably the physiological and biochemical status of cultured worms.

This technique was used to study the effect of Astiban on females and the results were compared with worms treated in vivo. Astiban concentrations greater than 30 µg/ml killed worms within 7–20 h and acted non–selectively. Astiban at low concentrations (10µg/ml) during short–term culture (1–3 h) resulted in a selective action of the drug on maturing vitelline cells. Thus, although the degree of cell damage caused by drug treatment was more severe and occurred earlier than the effects observed in worms cultured in vitro without drugs, both treatments resulted in differential cell death.

The uptake and retention of drug-related material by Schistosoma mansoni was studied in the mouse host following a single oral or intramuscular does (50 mg/kg) of [14C]oxamniquine. Male worms took up more labelled material than did female worms but the amount in each particular sex of worm was found to be similar after both routes of administration. Exposure of worms was therefore independent of the route of administration. Six days after drug administration, at the time of an hepatic shift, significantly more drug-related material* was present in male worms than in female worms. Examination of worms recovered from mice 4 h after treatment showed that metabolites of oxamniquine constituted 70–90% of the drug-related material present in the worms. Both sexes of worms were able to take up matebolites of oxamniquine win vitro.

Hepatic granulomas from mice infected with Schistosoma mansoni for periods of 8 weeks to 1 year were studied by electron microscopy. The different cell types present in the granulomas suggested that whilst a delayed hypersensitivity response predominated during early stages of infection an Arthus-type reaction associated with delayed hypersensi-tivity occurred at later stages of infection.

The ultrastructure of penetrating stages of Babesia major merozoites responsible for causing trans–ovarian infection of the tick Haemaphysalis punctala was studied. These merozoites were different from forms of other Babesia species previously described in the tick in that they were highly pleomorphic. Most of the organelles found in these forms were similar to those found in other stages: however, the apical complex was found to be very active. Micronemes were found to the apical complex was found to be very active. Micronemes were found to be predominant in the cytoplasm of these merozoites and a cytoplasmic projection anterior to the polar ring and bounded by concentric rings was visible. A polar ring with radiating ribs, and microtubules was present. It is thought that the apical complex of these merozoites plays an important role in assisting the parasite to infect the ovary of the tick.