In light of the low success rate of target-based genomics and HTS (High Throughput Screening) approaches in anti-infective drug discovery, in silico structure-based drug design (SBDD) is becoming increasingly prominent at the forefront of drug discovery. In silico SBDD can be used to identify novel enzyme inhibitors rapidly, where the strength of this approach lies with its ability to model and predict the outcome of protein-ligand binding. Over the past 10 years, our group have applied this approach to a diverse number of anti-infective drug targets ranging from bacterial D-ala-D-ala ligase to Plasmodium falciparum DHODH. Our search for new inhibitors has produced lead compounds with both enzyme and whole-cell activity with established on-target mode of action. This has been achieved with greater speed and efficiency compared with the more traditional HTS initiatives and at significantly reduced cost and manpower.

Strongyloides ratti (Nagoya strain) is unique in that a portion of adults parasitizing the small intestine withstands ‘worm expulsion’, which starts at around day 8 post-infection (p.i.) by host immunity, and establishes in the large intestine after day 19 p.i. To investigate the mechanism, adults obtained from the small intestine at day 7 or 19 p.i. were transplanted into the colon of infection-primed immune rats. Adults obtained at day 7 p.i. were rejected quickly, whereas those obtained at day 19 p.i. could establish infection. Moreover, the body length and the number of intrauterine eggs increased in the large intestine. In a separate experiment, large intestinal parasitism was abolished by the treatment of host rats with an anti-oxidant, butylated hydroxyanisole. These results indicate that small intestinal adults between days 7 and 19 p.i. acquired the ability to parasitize the large intestine of immune rats, and that free radicals produced by the host may have played a significant role in the process.

The time-course of the humoral immune response of female blackflies after a challenge with bacteria, different Onchocerca microfilariae species, bacterial endotoxin and microfilarial extract was investigated. Strong bacteriolytic and growth inhibition activities against the Gram-positive bacterium Micrococcus luteus were induced by all agents. Specific differences were found in activity levels and time-course. Notably the endotoxin lipopolysaccharide (LPS) induced a very early, profound bacteriolytic and antibacterial response, which declined within a day after injection. In contrast, the bacteriolytic activities after Escherichia coli D31 and Onchocerca microfilariae infections were lower, but remained elevated over the observation period of 4 days. The bacteriolytic activity was correlated to a haemolymph protein with a molecular weight of around 14 kDa. Anti-Gram-positive activity in the E. coli infected group appeared within the first 6 h. However, it took 4 days in the microfilarial infected blackflies to reach significant levels. The active agent was identified to be a peptide with a molecular weight of around 4–4.5 kDa. Activity against the Gram-negative bacteria E. coli was detected in blackflies injected with E. coli D31, O. dukei microfilariae and microfilarial extract on days 1 and 4 after injection. The immune response in S. damnosum s.l. naturally infected via a bloodmeal on cattle supported the findings of the experimental infections. Similarities of the immune response kinetics between bacterial and filarial infections suggested that intracellular Wolbachia bacteria, released from microfilariae, could be responsible for the antibacterial response. This is supported by the observation that the induction of an immune response in the Drosophila melanogaster mbn-2 cell line by the filarial extract is blocked by polymyxin B, which forms inactive complexes with bacterial LPS.

Visceral leishmaniosis is one of the most important zoonotic diseases on the planet and dogs are the main reservoir of canine visceral leishmaniosis (CVL) in endemic areas. They play an important role in human infection because in dogs the disease appears long time after infection, and they can move uncontrollably, contributing to disperse the parasite. To take the decision to treat the animals or for euthanasia, in an elimination programme, in order to reduce the parasitic load, it is necessary to diagnose correctly, having more effective tools. Our group has developed a new recombinant antigen-based kinesin-related gene of Leishmania braziliensis (Lbk39), which shows 59% amino acid identity to the L. infantum homologue. The Lbk39 gene was synthesized, inserted into the pLEXSY-sat2 vector and transfected into L. tarentolae cells by electroporation. The recombinant protein was secreted in the culture with a C-terminal histidine marker, purified, generating a product at 337.68 μg mL−1. A total of 152 sera from dog's endemic and non-endemic areas were used, being 78 positives and 75 negatives. The antigen Lbk39 showed 100% sensitivity and 96.1% specificity. We compared this antigen with other antigens such as total extract of the parasite, TRDPP, and our data indicate that Lbk39 has potential application in the diagnosis of CVL through antibody detection.

Histone H1 in Leishmania presents relevant differences compared to higher eukaryote counterparts, such as the lack of a DNA-binding central globular domain. Despite that, it is apparently fully functional since its differential expression levels have been related to changes in chromatin condensation and infectivity, among other features. The localization and the aggregation state of L. braziliensis H1 has been determined by immunolocalization, mass spectrometry, cross-linking and electrophoretic mobility shift assays. Analysis of H1 sequences from the Leishmania Genome Database revealed that our protein is included in a very divergent group of histones H1 that is present only in L. braziliensis. An antibody raised against recombinant L. braziliensis H1 recognized specifically that protein by immunoblot in L. braziliensis extracts, but not in other Leishmania species, a consequence of the sequence divergences observed among Leishmania species. Mass spectrometry analysis and in vitro DNA-binding experiments have also proven that L. braziliensis H1 is monomeric in solution, but oligomerizes upon binding to DNA. Finally, despite the lack of a globular domain, L. braziliensis H1 is able to form complexes with DNA in vitro, with higher affinity for supercoiled compared to linear DNA.

The world health organization currently recognizes diarrhoeal diseases as a significant cause of death in children globally. Protozoan parasites such as Giardia and Entamoeba that thrive in the oxygen-deprived environment of the human gut are common etiological agents of diarrhoea. In the urogenital tract of humans, the anaerobic protozoan parasite Trichomonas vaginalis is notorious as the most common non-viral, sexually transmitted pathogen. Even with high medical impact, our understanding of anaerobic parasite physiology is scarce and as a result, treatment choices are limited. Fluorescent proteins (FPs) are invaluable tools as genetically encoded protein tags for advancing knowledge of cellular function. These FP tags emit fluorescent colours and once attached to a protein of interest, allow tracking of parasite proteins in the dynamic cellular space. Application of green FPs-like FPs in anaerobic protozoans is hindered by their oxygen dependency. In this review, we examine aspects of anaerobic parasite biology that clash with physio-chemical properties of FPs and limit their use as live-parasite protein tags. We expose novel FPs, such as miniSOG that do not require oxygen for signal production. The potential use of novel FPs has the opportunity to leverage the anaerobe parasitologist toolkit to that of aerobe parasitologist.

The bisbenzimidazole compound Hoechst 33342 (Ho342) has been identified as a specific Topoisomerase-I (Topo-I) inhibitor in mammalian cells. More recently, we have reported the ability of Ho342 to target L. donovani Topo-I, leading to parasite growth inhibition in vitro by mechanisms involving DNA breakage and apoptosis-like phenomenon. As the Ho342 lead molecule (2,5′-Bi-1H-benzimidazole) can be used as a starting structure for derivative compounds more effective against Leishmania, defining the Ho342 resistance mechanism(s) in Leishmania represents an important strategic tool. In the present study, we selected resistant parasites to Ho342 (LdRHo.300). While we observed an increase of the Topo-I gene expression correlated by a higher Topo-I DNA relaxation activity, the Topo-I genes (LdTOP1A and LdTOP1B) sequencing did not reveal any mutation for the resistant parasites. Moreover, our results on Ho342 cellular accumulation suggested the presence of a potential energy-dependent Ho342 transporter in the wild-type parasite, and that an alteration of this transporter has occurred in LdRHo.300, leading to an altered drug accumulation. Collectively, Ho342 resistance characterization provided results supporting that the resistance developed by LdRHo.300 involves complex mechanisms, most likely dominated by an altered drug accumulation, providing new insight in the Ho342 resistance mechanisms.

To adapt to different environmental conditions between poikilothermic and homeothermic hosts, the plerocercoid of Spirometra erinacei (sparganum) might express a variety of biologically active molecules. We have identified a 78 kDa glucose-regulated protein of the sparganum (SpGrp78) by differential display of mRNA, employing RNAs each from sparganum adjusted at 9 °C and 37 °C. A full-length cDNA of 2148 bp encodes for a protein of 651 amino acids with a predicted molecular mass of 71 610 Da and shares molecular characteristics with heat-shock protein 70, including a putative ATP binding site, signal peptide cleavage site and endoplasmic reticulum retention signal. Phylogenetic analysis revealed that SpGrp78 was mostly related to those of Echinococcus multilocularis and E. granulosus. Expression of SpGrp78 mRNA increased approximately 7-fold by inhibition of glycosylation by tunicamycin, 2-fold by temperature-shift from 9 °C to 37 °C and slightly by pH-shift to 4·0 or 5·5. These results suggested that induction of SpGrp78 mRNA is related to the functional role of SpGrp78 as a molecular chaperone when the parasite adapts to a new host environment.

Although in nature Sleeping Sickness is chiefly transmitted by Glossina palpalis, the possibility of other modes of infection has been suggested by various authors.

Transfer of Eimeria apionodes from wood mice directly into untreated laboratory mice was unsuccessful but transfer into corticosteroid-treated animals produced an oocyst output, about 1000 times less than that observed from wood mice after a similar inoculum. Repeated passage through corticosteroid-treated laboratory mice resulted in a line adapted to survival in untreated animals. This line was compared with the parent strain maintained in wood mice and some features of the oocyst output patterns, notably the pre-patent period, appeared to be controlled by the host species. The oocyst production of each population was higher in the host species to which it was adapted than in the other host species (P > 0·001). Once adapted to laboratory mice, the line produced insignificantly different levels of oocysts in corticosteroid-treated and untreated animals (P > 0·05).

Some species in Subuluridae, Thelaziidae and Ascaridiidae are discussed. Subulara helicospicula sp.nov. from malcohas and a bulbul from Borneo is described. It differs from other species in having long, unequal spicules which are helical throughout their distal half. Allodapa suctoria (Molin, 1860) Seurat, 1914, is reported from several species of birds from Taiwan, Borneo and Palawan. A. turnicis (Maplestone, 1931) Inglis, 1958, was found in the button quail, Turnix sustator on Palawan.

Thelazia digiticauda Schuurmans-Steckhoven, 1937, is redescribed from specimens recovered from the eyes of a ruddy kingfisher, Halcyon coromanda from Taiwan. Ceratospira inglisi sp.nov. from a cockatoo in Palawan and a pigeon in Borneo differs in spicule size from the three species so far described. Oxyspirura {Y.) mansoni (Cobbold, 1879) Skrjabin, 1931, was recovered from bamboo partridges, Bambusicola thoracica, from Taiwan, and Oxyspirura (0.) popawi Skrjabin, 1929, was found in the eyes of a swallow, Hirundo daurica in Taiwan.

Ascaridia columbae (Gmelin, 1790) Travassos, 1913, was common in a variety of pigeons in Borneo and Palawan, and A. subaequalis (Wehr, 1930) was found in the lesser coucal, Centropus bengalensis in Taiwan and in a common coucal, C. sinensis in Palawan.

Using the method developed by VanOrden & Nelson (1926) in withdrawing and examining cloacal contents of four captive individuals of the Plathander or clawed frog (Xenopus laevis), the writer determined that infections of ciliate protozoans had persisted for more than 6 years.

The value of arsenic in the treatment of trypanosomiasis is no new discovery.

Evans (1880), who described the first pathogenic trypanosome, recommended the administration of arsenic. Lingard (1899), for many years, investigated surra in India and treated twenty-one horses suffering from that disease with arsenious acid. One horse survived. His system of treatment was, the administration of arsenic in the form of Fowler's solution, commencing with 5 grains, twice daily and gradually increasing to 10 grains. Treatment extended over several months; the total amount of arsenic given, in some instances, amounted to over 2,000 grains. During the period of treatment intermissions of 30 to 50 days were recorded, but all the animals, with one exception, finally succumbed to the disease. Bruce (1897 and 1903), treating nagana in Zululand, gave 6 to 12 grains of arsenic in form of arsenite of soda to horses and asses suffering from that disease. Trypanosomes remained absent during the period of treatment, but reappeared immediately treatment ceased. Trélut (1907) claims to have cured cases of dourine by the daily administration of 3 to 6 grammes of arsenious acid. Archangeliky and Novikoff (1907) also record cases of dourine cured by them with arsenite of sodium and cacodylic acid. Marchal (1903) stated that he cured five stallions suffering from dourine by subcutaneous injections of 1 gramme of cacodylate of soda. Loeffler and Ruehs (1908) record a number of successful experiments on animals affected with nagana, which they treated with a solution of arsenious acid. They consider this solution to be a specific cure and a prophylactie for nagana. Laveran and Thiroux (1907–8) repeated these experiments and came to conclusions different form those of Loeffler and Ruehs.

In an interconnected world, the international pet trade on wild animals is becoming increasingly important. As a consequence, non-native parasite species are introduced, which affect the health of wildlife and contribute to the loss of biodiversity. Because the investigation of parasite diversity within vulnerable host species implies the molecular identification of large samples of parasite eggs, the sequencing of DNA barcodes is time-consuming and costly. Thereby, the objectives of our study were to apply the high resolution melting (HRM) approach for species determination from pools of parasite eggs. Molecular assays were validated on flatworm parasites (polystomes) infecting the Mediterranean pond turtle Mauremys leprosa and the invasive red-eared slider Trachemys scripta elegans in French natural environments. HRM analysis results indicated that double or multiple parasitic infections could be detected from wild animal populations. They also showed that the cycle of parasite eggs production was not regular over time and may depend on several factors, among which the ecological niche and the target species. Thereby, monitoring parasites from wild endangered animals implies periodic parasitological surveys to avoid false negative diagnostics, based solely on eggs production.

Immunization was performed against Schistosoma mansoni or S. japonicum infection in rhesus monkeys either with living schistosomula and young adult worms or with only schistosomula by intra-peritoneal injection. Each monkey was immunized four or more times and subsequently challenged. A significant degree of resistance against the challenge was produced. The injected worms lived in the peritoneal cavity for a short period, then died and disintegrated therein, thus obviating their inhabiting the circulatory system. The functional antigens were evidently derived from the metabolic products of the immunizing living schistosomes in the peritoneal cavity.

The results of the present experiment indicate that the main immune mechanism induced by the intraperitoneal injection of living schistosomula and young adult worms is that which inhibits the development of the late stage of schistosomula and the early stage of adults which have originated from the challenge infection. This immune mechanism may be induced by the functional antigens either from both the schistosomula and adult worms or from the schistosomula alone.

Whilst examining amphibian helminths collected from Pahang, Malaya, a hitherto undescribed species of Oswaldocruzia was found among them. In a previous paper (Yuen, 1962), I have recorded the only other Malayan species of Oswaldocruzia: namely O. hoepplii Hsu from Bufo melanostictus Boulenger, Rana macrodon Boulenger, and R. cancrivora Gravenhorst from various parts of Singapore.

The observations recently set forth by Dr Leiper, and by Dr Sambon in a discussion, have led us to re-examine the ova of S. japonicum in the material which we have at hand. This material was described previously by one of us together with a report of some comparative measurements of the ova of this species of trematode furnished by Dr Shiga.

1. A brief account is given of a schistosoma cercaria obtained from Bulinus truncatus possessing four pairs of flame cells in the body.

A monkey, Cercopithecus sebaeus, was experimentally infected with this cercaria, adult male and female S. haematobium being formed in the mesenteric veins, and terminal spined ova in the sub-mucosa of the colon.

The view is expressed that this cercaria was probably an aberrant form of the cercaria of S. haematobium.