Iron is an essential element for the survival of trichomonads during host–parasite interaction. The availability of this metal modulates several metabolic pathways of the parasites and regulates the expression of virulence factors such as adhesins and proteolytic enzymes. In this study, we investigated the effect of iron depletion on the morphology and life cycle of Tritrichomonas foetus. Scanning and transmission electron microscopy analyses revealed that depletion of iron from the culture medium (named TYM-DIP inducer medium) induces morphological transformation of typical pear-shaped trophozoites into spherical and non-motile pseudocysts. Remarkably, inoculation of pseudocysts into an iron-rich medium (standard TYM medium), or addition of FeSO4 to a TYM-DIP inducer medium reverted the morphological transformation process and typical trophozoites were recovered. These results show that pseudocysts are viable forms of the parasite and highlight the role of iron as a modulator of the parasite phenotype. Although iron is required for the survival of T. foetus, iron depletion does not cause a cellular collapse of pseudocysts, but instead induces phenotypic alterations, probably in order to allow the parasite to survive conditions of nutritional stress. Together, these findings support previous studies that suggest pseudocysts are a resistance form in the life cycle of T. foetus and enable new approaches to understanding the multifactorial role of iron in the cell biology of this protozoan parasite.

This study investigated the molecular and biological variation among different Giardia duodenalis assemblages. In vitro growth and susceptibility to albendazole, fenbendazole, flubendazole, metronidazole, tinidazole and furazolidone was studied for laboratory (AI: WB, AII: G1 and B: GS/M-83-H7) and 6 field isolates of assemblage subtype AI, AII, B and EIII. Additionally, isolates of the 3 assemblages were evaluated in the gerbil upon 3-day oral treatment with albendazole (6 mg/kg), flubendazole (5 mg/kg) and metronidazole (20 mg/kg). Assemblage AI grew significantly faster than all other assemblage subtypes, which showed comparable generation times. The assemblage A laboratory strains displayed altered in vitro drug susceptibilities compared to their matching AI or AII field isolate. No variation in drug susceptibility was observed between field isolates of assemblages A and E. However, assemblage A laboratory strains were more susceptible to the benzimidazoles and less susceptible to the nitro-imidazoles and furazolidone than the assemblage B laboratory strain. In the gerbil, no markedly different drug susceptibilities were observed. In conclusion, the Giardia assemblage subtype can be associated with differences in growth characteristics rather than in drug susceptibility.

A simple technique is described for preparation of Giardia cysts from faecal samples, the growth of trophozoites in suckling mice and the isolation of trophozoites for genetic analysis by allozyme electrophoresis. In total, 125 new isolates of Giardia have been collected from human and animal sources over a wide geographical area of South Australia and the Northern Territory of Australia. A number of long-established axenized isolates of G. intestinalis belonging to Groups I and II also adapted to grow in suckling mice. These findings indicate that suckling mice are permissive hosts for a variety of genetically dissimilar but morphologically similar organisms of the G. duodenalis type and that this in vivo technique may be less selective than isolation by in vitro culture. The use of suckling mice has revealed that infections can be composed of mixed genotypes and that isolation and purification techniques can be selective. Allozymic interpretation is essential to reveal the genetic complexity of such mixtures

An in vitro culture of Plasmodium falciparum (isolate FCUP-1/RSA) was arrested in the trophozoite stage with α-difluoromethylornithine (DFMO), followed by sorbitol treatment to liberate intracellular parasites from infected erythrocytes. Most of the unlysed erythrocytes and ghost membranes were removed by filtration, after agglutination with anti-erythrocyte monoclonal antibodies or wheat-germ agglutinin. A highly purified parasite preparation was obtained after chromatography on an immuno-affinity column consisting of polystyrene particles to which anti-erythrocyte monoclonal antibodies had been adsorbed. Isolated parasites were free of surrounding erythrocyte membranes and structurally intact as assessed by transmission electron microscopy, SDS–PAGE and ELISA.

A two-colour flow cytometry technique was used to assess killing of Giardia muris trophozoites by rabbit anti-trophozoite antibodies and complement. Binding of rabbit antibody to trophozoites and killing of trophozoites were documented by flow cytometry, after incubating the organisms with fluorescein-conjugated anti-rabbit IgG and propidium iodide (PI). Percentages of PI+ (dead) trophozoites ranged from >80%, after incubation with rabbit antiserum and complement, to <30%, after incubation with complement alone. The assay technique may be applicable to studies aimed at determining whether intestinal antibodies from Giardia-infected mammals can kill Giardia trophozoites.

Among the different stages in the protozoan Perkinsus marinus life cycle, the trophozoite stage is known to be the most infective stage in marine molluscs. To develop a direct method for in vitro studies of P. marinus proliferation under various environmental conditions, monoclonal antibodies (MAbs) specific for this pathogen were produced. Inbred strains of mice BALB/c were immunised with a trophozoite prepared from cloned isolate Perkinsus 1 cultured on JLODRP1 medium. The mouse polyclonal antiserum showing the highest antibody titre for pathogen trophozoites was chosen for lymphocyte hybridisation. The screening of positive hybridoma by indirect enzyme-linked immunosorbent assay (ELISA) revealed two probes (17B2D5 and 19G3H6) detecting P. marinus trophozoites and their protein lysates but also trophozoites from P. atlanticus. These MAbs belonged to the immunoglobulin IgG1 subclass. Their binding specificity was investigated by ELISA and fluorescein (FITC) methods. Both immunoreacted with trophozoite stage as well as hypnospore and zoospore stages of P. marinus, but neither with hemolymph and tissues of oysters, Crassostrea gigas and C. virginica, nor with parasites, Bonamia ostreae and Marteilia refringens. A competitive ELISA method was developed, using 17B2D5 MAb to evaluate parasite multiplication in culture media and to estimate the parasite burdens from infected oysters. This method is sensitive enough to detect 103 trophozoites in 50 μL assay sample.

Examination of Giemsa stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot area showed the presence of seven out of the nine Plasmodium species of lizards which have been previously described in Africa. These species are redescribed using a set of biological characters and procedure which enabled a large quantity of each stage of any species to be studied, measured and compared. The utilization of these characters and procedure was a reaction to the multiple infections in individual lizards and a wide host range of each species among lizard species. The adoption of the criteria is recommended for future taxonomie work on lizard Plasmodia in Africa.

A key which brings together all the previously described species of lizard Plasmodia and the new species encountered in the present investigation is presented. The key is simplified so that it can be of use to epidemiologists and pathologists who may work on saurian malaria in Africa.

During investigations on the malaria parasites of lizards in the West Pokot district of Kenya, haemoproteids, haemogregarines, pirhemocyton-like and anaplasma-like organisms were found in the blood. Microscopic examination showed that some of these are new species and they are described in this paper. The new described species are Haemoproteus mungutii (haemoproteid), Karyolysus poleensis, Schellakia mabuyai (haemogregarines), Pirhemocyton kongelai, Haematractidium omogoi, Sauroplasma kachelibaensis (Pirhemocyton-like organisms), Eperythrozoon ngokai and Aegyptianella elgonensis (anaplasma-like organisms). K. poleensis and S. mabuyai are regarded as the first report of the genera in lizards in Africa while A. elgonensis is regarded as the first report of the genus Aegyptianella in lizards.

During investigations into the epidemiology of malaria of lizards in Kenya, Giemsa-stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot district were examined for the presence of Plasmodium species. Ten new species were found and described. These are Plasmodium sapaaensis, P. kyaii, P. kachelibaensis, P. icipeensis, P. gloriai, P. odhiamboi, P. bowiei, P. kaninii, P. kadogoi and P. adunyinkai.

P. sapaaensis was found to be related to P. mabuiae, P. kadogoi to P. rhadinurum, P. kaninii to P. minasense (s. Telford) and P. adunyinkai to P. maculilabre. P. kyaii and P. kachelibaensis have distinct characteristics which distinguish them from the Plasmodium species in the tropiduri group reported so far.

Four species i.e. P. icipeensis, P. odhiamboi, P. gloriai and P. bowiei, exhibited peculiar characteristics most especially their effect on the white cells. They were therefore constituted into the “Kenyan” group.