Glucose uptake was examined in adult specimens of Proterometra macrostoma (Trematoda: Digenea) recovered from the stomach (endoparasites) and gills (ectoparasites) of longear sunfish, Lepomis megalotis. The endoparasitic forms transported glucose directly through the external body surface by Na+-independent, facilitated diffusion, but the ectoparasites absorbed glucose by free diffusion alone. To determine how this transport function is regulated, cercariae were incubated in solutions having Na+ concentrations normally found in fish gut (50 mM) and in fresh water (0·5 mM). Glucose transport capacity was retained in 50 mM Na+, but disappeared in worms incubated for 1–3 days in 0·5 min Na+. Returning worms from the latter solution to one containing 50 mM Na+ fully restored glucose transport within a day. By contrast, incubation up to 5 days in 0·5 mM Na+ had no effect on glucose transport in endoparasitic adults of P. macrostoma and cercariae of P. edneyi. Thus, cutaneous sugar transport function in the migrating larva of P. macrostoma is subject to indirect regulation by environmental Na+.

Specific sequences derived from the gene for the precursor to the major merozoite surface antigens (PMMSA) of Plasmodium falciparum have been expressed in Escherichia coli and the products have been used to produce antibodies. These antibodies, together with monoclonal antibodies, have been used to investigate the form of the PMMSA protein associated with merozoites. Polypeptide fragments derived by processing from the PMMSA protein have been detected in extracts of merozoites and assigned to locations within the PMMSA coding sequence.

Antigenic differences between intra-lymphocytic theilerial parasites isolated from the blood of 18 African buffalo and grown in vitro were assessed with anti-schizont monoclonal antibodies (mAbs). There was marked antigenic diversity both between isolates from different buffalo and between isolates taken at different times from the same buffalo. Many of the isolates from both wild and captive buffalo appeared to consist of mixed parasite populations. Some isolates were found by limiting dilution cloning and mAb testing to contain at least 3 or 4 distinct populations of Theileria. Once cloned, Theileria-infected lymphoblastoid cell lines retained their mAb profiles during prolonged in vitro cultivation and, when recloned, the subclones had the same mAb profile as their parent clone. The implications of these results for further studies on buffalo-derived theilerial parasites are discussed.

An enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies to Encephalitozoon cuniculi in man, using spores derived from tissue culture as antigen. Negligible cross-reactions were found with other microsporidia of vertebrate or of invertebrate origin and there was no cross-reaction with Toxoplasma gondii, using ELISA, immunoperoxidase or immunofluorescence staining. A high prevalence of antibodies to E. cuniculi was found in patients suffering from schistosomiasis, malaria and neurological and psychiatric disorders, but not in healthy individuals.

An African buffalo (Syncerus caffer), born in captivity and demonstrated to be Theileria-free, and 2 susceptible cattle were inoculated with a Theileria parva lawrencei sporozoite stabilate. The buffalo had a very mild disease reaction, while the 2 cattle died of acute theileriosis. It was possible to isolate T. p. lawrencei from the buffalo up to 888 days after infection by the application of non-infected Rhipicephalus appendiculatus nymphs and up to 657 days after infection by the establishment of lymphoblastoid cell lines infected with T. p. lawrencei schizonts from peripheral mononuclear blood cells. The infection rate and levels of Theileria in the resultant adult ticks varied from 11 to 70% with 0·3–11 acini infected/tick. Stabilates prepared from these tick batches caused fatal T. p. lawrencei infections in cattle.

Host specificity of a siphonostome copepod Ophiopsyllus reductus was confirmed by the results of an extensive survey of co-existing possible alternate host brittlestars. The parasite was found only on Ophiocomella ophiactoides. The ability to discriminate between potential hosts was tested experimentally. O. ophiactoides was always preferred and, in experiments with unrelated alternative hosts, the discrimination was absolute. When closely related species were the alternate host, discrimination was less complete. It is suggested that the discrimination is due to recognition of either tactile or chemical characteristics of the preferred host.

The first two phases in the growth of Maritrema linguilla in Ligia oceanica, which occur in unencysted specimens in the pleopod sinuses, from day 0 to day 28 post-infection (p.i.), include a 3-fold increase in size, an enormous increase in the relative size of the excretory bladder, metamorphosis of papilliform extensions of the tegument into microvilli and development of single pointed spines and cystogenous gland cells. The third phase, from day 29 to day 38 p.i., following migration to the dorsal haemocoel, includes production of 3 cyst wall layers, the loss of single pointed spines and a considerable decrease in the relative size of the excretory bladder. The fourth phase from day 39 to day 42 p.i., involves a further increase in body size and the formation of digitiform spines. The fifth, sixth and final phases from day 43 to day 120 p.i. first include the completion of the last two cyst wall layers and then an increase in body size and development of the digestive, excretory and reproductive systems to almost adult dimensions but sperm, ova, vitelline globules and eggs are produced only in the final host.

Nymphal Rhipicephalus appendiculatus (Trans-Mara) were fed on a steer infected with a Theileria parva parva (Kilae 1) stock isolated from an indigenous steer in the Trans-Mara Division, Kenya, which had a high piroplasm parasitaemia. A total of 5000 engorged nymphs which had dropped on one day were enclosed in elongated nylon bolting silk tubes in groups of 200–300 and were transported immediately to the Trans-Mara where they were suspended vertically in the grass cover with one end touching the ground. Over 98% of the nymphs moulted into adult ticks and 50% moult occurred by day 28 after exposure. The ticks showed over 80% survival up to 308 days post-exposure but thereafter showed a marked mortality so that only 22·5 % of the ticks were alive after 439 days. Theileria parasites were detected in the salivary glands by day 35 post-exposure and infection rates and levels increased markedly between 180 and 235 days post-exposure. Thereafter, the infection rates and levels generally decreased. Groups of ticks were triturated and the resultant supernatant fluid inoculated into pairs of susceptible cattle, and these proved infective from day 44 to 145 after exposure. Three subsequent attempts to induce infections with supernatant fluid were unsuccessful. From 294 days after exposure, groups of 50 ticks were applied to cattle and caused lethal T. p. parva infections up to 439 days post-exposure. Climatic observations showed a relatively even monthly rainfall as well as mean maximum and minimum monthly temperatures. Clean nymphal R. appendiculatus were applied to a steer infected by adult ticks exposed for 405 days and the resultant adults were incubated at 37 °C for 6 days. Supernatant fluid produced from these ticks caused a lethal T. parva infection in a susceptible steer.

A monoclonal antibody-producing hybridoma cell line has been raised against merozoites of Babesia divergens. This antibody is strongly reactive against merozoites in an enzyme-linked immunosorbent assay (ELISA) and is also positive in an indirect fluorescent antibody test (IFAT) on preparations of live merozoites. The antibody recognizes an antigen, of molecular weight (Mr) 50–60 K by Western blot analysis on SDS–polyacrylamide gel electrophoresis (SDS–PAGE) gels. Merozoite neutralization assays show that the antibody significantly inhibits merozoite invasion of bovine erythrocytes.

The tegumental membrane potential (–63±2·9 mV) of adult male Schistosoma mansoni in RPMI-1640 is significantly depolarized (–26±7·3 mV) when the parasite is incubated in inorganic media (Hank's Balanced Saline or RPMI-1640 without organic constituents). Of 9 amino acids (L-glutamine, D-glutamine, L-arginine, L-proline, L-aspartate, L-glutamate, L-asparagine, L-isoleucine and L-methionine) L-glutamine alone is sufficient to repolarize the membrane potential to a value (–56±4·5 mV) not significantly different from that found in RPMI-1640. Repolarization by glutamine is dose-dependent, with significant effects obtained as low as 0·10 mM. The concentration of phosphate in the medium also significantly alters the membrane potential. Physiological levels of phosphate (5·6 mM) are necessary in conjunction with L-glutamine to obtain the full repolarization of the membrane potential. In the absence of organic constituents, the membrane potential is strongly dependent on the external medium pH. When L-glutamine is present in the medium, the membrane potential becomes virtually independent of the external pH.

Plasmodium chabaudi AS strain in mice is characterized by an acute primary parasitaemia, and one or more less acute recrudescences. Previous work has shown, using a passive protection assay, that the recrudescent parasites are usually antigenically different from parasites of the parent population with which the mice were first infected. In this study the effect of mosquito transmission on the antigenic expression of recrudescent populations of P. chabaudi was examined. In the first experiments the recrudescent population which was antigenically different from the parent population was uncloned. After transmission through Anopheles stephensi the recrudescent population appeared to revert to an antigenic type similar to that of the parent population. In the second experiment clones from a recrudescent population were mosquito transmitted and again the parasites of the primary patent parasitaemia in the mice, bitten by the infected mosquitoes, had reverted to the parental type. It is suggested that antigenic variants of P. chabaudi AS strain may revert to a basic type after mosquito transmission.

Four monoclonal antibodies, raised against macroschizonts of Theileria parva, were studied to characterize their antigen binding specificity. The indirect fluorescent antibody test showed that the antigen(s) recognized were present in the macroschizont stage of the parasite life-cycle but not in piroplasm, kinete or sporozoite stages. Immunoblot analysis of macroschizont stage antigens suggested that all four antibodies recognized the same antigen. This was a molecule which varied in molecular mass between different parasite stocks, ranging from 68000 to 95000 Da. The antigen was localized by immunoelectron microscopy to the surface of the intracellular macroschizonts.

The patients we are concerned about in tropical medicine are unfortunately affected by a wide range of conditions, not only those seen and studied extensively in the West, such as cancer, cardiovascular diseases and viral or bacterial infections, but also the major protozoan and metazoan conditions – the parasitic diseases. It is with this spectrum of pathophysiological changes that occurs in this last group that we are presently concerned and this communication is intended to present an overview of the subject.

Isoenzyme analysis was used to characterize 6 species of trypanosomes of the subgenus Herpetosoma using 13 different enzyme systems. The species studied were Trypanosoma lewisi, T. musculi, T. grosi, T. microti, T. evotomys and T. nabiasi which cannot be distinguished on morphological grounds. Extracts for thin-layer starch-gel electrophoresis were prepared from cultures of insect forms in either Schneider's Drosophila or Grace's insect tissue culture media with foetal calf serum or a nutrient agar medium. Extracts of T. lewisi and T. musculi bloodstream forms were also run for comparison. All parasites gave distinct patterns which enabled them to be differentiated on one or more enzyme systems. Two types of computer analysis were used to group the parasites; using these techniques the murine parasites T. lewisi, T. musculi and T. grosi fell into one broad group, and T. microti and T. evotomys of microtine rodents formed another. These findings are in accord with earlier observations on the behavioural characteristics of these parasites in their mammalian host and their vector (fleas). The clear differences observed provide the basis for the application of other biochemical and immunological techniques for differentiation within this subgenus of trypanosomes.

Regional differences in the response of mice to infection with three strains of dermotropic Leishmania spp. were shown for skin covering the trunk. Lesions tended to appear earlier and to grow more rapidly on sites over the caudal half of the body than the cranial half, and caudal lesions were more likely than cranial ones to result in metastatic disease in susceptible strains of mice. Site-related variations in lesion development were observed in different strains of mice as well as in golden hamsters. The effect of these regional differences on the development of some parasite-specific, immunological reactions was examined, as were parasite thermosensitivity and location-related variations in host skin temperature as possible explanations.

Parasites can have a wide range of pathophysiological effects on the host. This review describes those associated with some parasites of major importance in man and animals. Haemoprotozoan diseases such as trypanosomiasis and malaria are primarily associated with anaemia. Such anaemias have a complex aetiology involving various mechanisms responsible for red cell destruction as well as possible defects in red cell production. In addition to these haematological effects these diseases are associated with marked disturbances in heart function and the nervous, immune and urinary systems. The other major groups of parasitic diseases are those associated with the gastrointestinal tract. The most advanced studies have been conducted on the pathophysiology of gastrointestinal nematode parasites of sheep and have revealed significant effects on feed intake, gastrointestinal function, and protein and energy metabolism. Similar studies have yet to be conducted in other hosts and parasitic diseases. There is also a need to examine in greater detail the factors which can modulate pathophysiological responses by the host to parasitic infections.

The long-term, in vivo effects of a single, subcurative dose (200 mg/kg body weight of mouse) of praziquantel on the structure of adult Schistosoma mansoni and on the process and speed of tegumental repair are described. In both male and female worms praziquantel caused often extensive damage to the tegument, in the form of surface blebbings, swellings and lesions, and vacuolization and disruption of the subtegumental tissues. Repair of the drug-induced tegumental damage occurred slowly with partial and, more rarely, complete repair only being seen after 65 days post-treatment (p.t.), although signs of damage were still observed, particularly in male worms, at 100 days p.t. In contrast, repair of damage to the subtegumental/parenchymal tissues including the tegumental perikarya occurred relatively quickly, with the majority of worms examined appearing normal by 8–12 days p.t. The possible role(s) of the host immune response in relation to the speed of tegumental repair in vivo is discussed.