The performance of 4 serological tests for the diagnosis of Chagas disease was evaluated in Santander, Colombia, a region still presenting active transmission. Serum samples from 638 individuals were submitted to an enzyme immunoassay test (EIA), using total lysate of a local Trypanosoma cruzi strain and 52·5% were positive (335/638). A subset of this group (94 positive individuals and 90 seronegatives) was randomly selected for further serological confirmation. Three additional tests were used – indirect immunofluorescence (IIF) and 2 distinct enzyme-linked immunosorbent assays using total lysate of the Y strain (EIA BM) and a mixture of 2 recombinant antigens (EIA RA). Seventy-nine patients were seropositive in all tests (84·0% – 79/94). The number of positive sera with the IIF, EIA RA and EIA BM was 84/94 (89·4%), 80/94 (85·1%) and 79/94 (84·0%), respectively. In 15 out of the 94 EIA seropositive patients (16·0%), 10 individuals were negative in all 3 tests (10·6% – 10/94). One was negative in the EIA BM and positive in the other two tests (1·1% – 1/94) and 4 patients were positive, solely, in the IIF assay (4·3% – 4/94). Relative to the 90 EIA negative individuals, 89 were confirmed in all other tests (98·9% – 89/90). One individual, although seronegative in the IIF, was positive in both confirmatory EIA tests (1·1% – 1/90). In addition, 120 blood specimens were submitted to PCR amplification. This group consisted of 79 confirmed seropositive cases, 16 individuals with discordant serological results and 25 validated seronegative individuals. The PCR was able to detect the presence of parasite DNA in 67 out of the 79 seropositive patients (84·8%), in 8 individuals with discordant serology (50·0%) and in only one seronegative individual (4·0%). The results pointed to the necessity for performing more than one serological test, preferentially with antigens from autochthonous strains, to achieve a reliable diagnosis of Chagas disease in Colombia.

The in vivo effects of a single, subcurative dose (200 mg/kg body wt of mouse) of praziquantel on the structure of the tegument and subtegumental tissues of juvenile (21-, 26- and 30-day-old) and adult Schistosoma mansoni are described. In juvenile worms praziquantel caused only moderate damage to both the tegument and subtegumental tissues although the degree of drug-induced damage was related to both the sex of the worms and to the developmental status of each individual worm. In general, male worms exhibited more extensive and longer lasting surface damage than females. However, the level and extent of the changes increased as the worms became more developmentally advanced with adult worms showing extensive damage to the tegument and vacuolization and disruption of the subtegumental tissues. The possible correlation between the stage-dependent changes in susceptibility to praziquantel and age-related changes, particularly in the phospholipid composition of the outer tegumental membrane is discussed.

The primary infection of breeding female rates with N. brasiliensis was examined as an experimental model for the study of the effect of lactation on host-parasite relationships.

Self-cure was inhibited when the period of infection corresponded with lactation, and a majority of worms could persist to day 34 when lactation was prolonged. A normal self-cure occurred during pregnancy, when litters were removed at birth or when the suckling litter was reduced to 3 young.

Babesia parasites generally require a defined percentage of serum in the culture medium for their in vitro growth. In this study, we attempted to culture Babesia bovis in a serum-free condition. The growth pattern and morphology of B. bovis in serum-free (plain) GIT medium were unaltered as compared to those of the standard growth condition containing 40% bovine serum in M199. When exposed to the test drugs, the parasite in plain GIT medium showed clearly lower IC50 values than those in 40% serum-containing GIT medium, indicating that several serum components may interfere with the drug bio-availability. Therefore, the serum-free culture system is useful for standardizing drug test protocols and understanding the roles of serum factors in the drug test.

1. The main facts in Brasil's (1907) account of the intracellular schizogony in Selenidium caulleryi from Protula tubularia have been confirmed. Early stages in the sporogony of this species are described now for the first time.

2. Intracellular schizogony is described for the first time in Selenidium mesnili Brasil from Myxicola infundibulum, and here also the early stages in sporogony are noted for the first time.

3. The life histories of Caullery and Mesnil's two unnamed species of Selenidium (now called S. spionis (Köll.) and S. foliatum n.sp.) from Scolelepis fuliginosa have been exhaustively studied. No schizogonic phase has been observed in either. The gametocysts, here described for the first time, are found to develop fully only after escape into the sea. The gametocysts of S. spionis are ovoid, 108μ x 60μ and contain spores with four sporozoites: those of S. foliatum are spherical, 70μ in diameter, and their spores contain eight sporozoites.

4. New or hitherto little known species of Selenidium are recorded from Cirratulus cirratus Müll., Branchiomma vesiculosum Mont., Sabella pavonina Sav., Pomatoceros triqueter L. and Terebella lepidoria Kühl, and the morphological characters of the trophozoites are described.

5. A discussion follows of the value of the diagnostic characters of the genus Selenidium. It is suggested that this genus requires drastic revision and will probably have to be dismembered. Stress is laid, however, on the occurrence in all the gregarines examined, and at all the observed stages of their development, of characteristic chromatic bodies at the anterior end, structures which have hitherto escaped the notice of most observers.

The hatching of Hymenolepis diminuta eggs and penetration of the emergent hexacanths in adult and larval Tenebrio molitor beetles had been described. Hatching was shown to be a two-stage process involving rupture of the eggshell by the insect's mandibles and digestion of the remaining egg-layers in the midgut lumen. Penetration of hatched embryos was examined by histological methods that demonstrated the rate of migration and the route taken by hexacanths entering the haemocoel of adult beetles. Differences in the arrangement of the midgut tissues in adult and larval T. molitor were detected and shown to account for the failure of hexacanths to complete migration in the larvae. The role of the embryonic hooks and penetration gland secretions during hatching and penetration has also been discussed.

I should like to thank Professor T. R. E. Southwood for providing generous research facilities, Dr June Mahon for her advice and encouragement, and in particular, Dr W. Mordue for his continuous interest and many useful criticisms. This work was conducted during the tenure of a Science Research Council Studentship at Imperial College of Science and Technology, London, S.W. 7.

The structure of the head and especially of the mouth-parts of these economically very important flies has been studied by many observers. The first very brief remarks on the proboscis were made by Wiedemann (1830), in his original description of the genus Glossina. He pointed out that the proboscis is almost as long as the thorax, and setiform and triangular in its basal part, the palps almost as long as the proboscis and horizontal. In the same year, Robineau-Desvoidy (1830) described another species of tsetse-fly, Glossina palpalis, but under the generic name Nemorphina, which became a synonym of Glossina. In his diagnosis of the genus, he gave an even shorter description of the proboscis which he believed was not adapted for sucking blood.

Prior field studies and modelling analyses have individually highlighted the importance of age-specific and spatial heterogeneities on the risk for schistosomiasis in human populations. As long-term, large-scale drug treatment programs for schistosomiasis are initiated in subSaharan Africa and elsewhere, optimal strategies for timing and distribution of therapy have yet to be fully defined on the working, district-level scale, where strong heterogeneities are often observed among sublocations. Based on transmission estimates from recent field studies, we develop an extended model of heterogeneous schistosome transmission for distributed human and snail population clusters and age-dependent behaviour, based on a ‘mean worm burden+snail infection prevalence’ formulation. We analyse its equilibria and basic reproduction patterns and their dependence on the underlying transmission parameters. Our model allows the exploration of chemotherapy-based control strategies targeted at high-risk behavioural groups and localities, and the approach to an optimal design in terms of cost. Efficacy of the approach is demonstrated for a model environment having linked, but spatially-distributed, populations and transmission sites.

An enzymatic comparison has been made between isolates of Schistosoma mansoni from rats and humans in Guadeloupe and a Burundi isolate of S. rodhaini. Analyses of LDH, MDH, AcP, PGM, GPI, G6PDH and HK by isoelectric focusing provided no evidence for the involvement of S. rodhaini in the recent evolution of the schistosomes currently endemic in Guadeloupe. No distinction could be made between murine and human isolates of S. mansoni and it is suggested that murine schistosomiasis should not therefore be ignored in control programmes. Rattus rattus were captured at seven sites around the island; of 142 examined, 48 were positive for schistosomes. Differences in prevalence between habitats were marked and only small changes in prevalence were observed in localities sampled in 1982 and 1983. Animals with the greatest worm burdens were associated with areas of high prevalence, and age-related changes in worm burden were observed. Two alleles, a and b, at the MDH-1 locus of S. mansoni from rats were identified. Differences in the overall frequencies of these alleles were observed for schistosomes from different localities. Allelic frequences representative of schistosomes from rats at four localities were stable from 1982 to 1983. The majority of positive animals, even those with light worm burdens, were found to be infected with a number of different schistosome genotypes.

We have examined several taxonomic features of a number of strains of Eimeria from many sources world wide. The strains were isolated on the basis of their small spherical (or sub-spherical) oocysts. From a study of mean oocyst dimensions, electrophoretic variation of enzymes, ability to develop in embryonated eggs, absence of gross lesions in heavily infected chickens, and cross-immunity, all the strains were found to belong to one species. For convenience, the parasites when isolated, were referred to as strains of E. mitis/mivati-type, but after characterization they were clearly found to be E. mitis. In contrast, a laboratory strain of E. mivati supplied to one of us (M.W.S.) was found to be a mixture of E. acervulina and E. mitis. Evidence from these and other studies supports the notion that E. mivati is a nomina dubia.

The population dynamics of Sphaerospora dicentrarchi and S. testicularis, myxosporean parasites of sea bass (Dicentrarchus labrax), was studied in different groups of cultured and wild fish. S. dicentrarchi prevalence was higher for wild fish (100%) than for cultured ones (70.5%). Infection levels increased with host age and there were no significant sex differences in cultured fish. Among parasitized organs, the gall bladder and intestine registered the highest infection levels in wild and cultured fish. A progressive increase in infection levels of S. testicularis was observed in cultured males during the spawning season in four consecutive periods. The evolution of the percentage of the different parasitic stages is pointed out. The infection seems to be related to water temperature and gonadal maturation.

The diversity and similarity of parasite communities is a result of many determinants widely considered in parasite ecology. In this study, the metazoan parasite communities of 15 chub populations (Leuciscus cephalus) were sampled across a wide geographical range. Three hypotheses of biogeographical gradients in species diversity were tested: (1) latitudinal gradient, (2) a ‘favourable centre’ versus ‘local oasis’ model, and (3) decay of similarity with distance. We found that the localities in marginal zones of chub distribution showed lower parasite species richness and diversity. A latitudinal gradient, with increasing abundance of larvae of Diplostomum species, was observed. There was a general trend for a negative relationship between relative prevalence or abundance and the distance from the locality with maximum prevalence or abundance for the majority of parasite species. However, statistical support for a ‘favourable centre’ model was found only for total abundance of Monogenea and for larvae of Diplostomum species. The phylogenetic relatedness of host populations inferred an important role when the ‘favourable centre’ model was tested. Testing of the hypothesis of ‘decay of similarity with geographical distance’ showed that phylogenetic distance was more important as a determinant of similarity in parasite communities than geographical distance between host populations.

The development of Amplicaecum robertsi has been followed from the egg to the adult stage using laboratory mice and rats as intermediate hosts. The eggs were found to be resistant to desiccation and would develop under water; they were infective to mice after culturing for 18 days after removal from the uterus.

Completion of the first moult occurred after hatching of the eggs in the intestine. Within 6 hr. of infection second-stage larvae had reached the liver. They also appeared in the lungs and carcass, but after 2 days were mostly confined to the liver.

At 5–7 days after infection larvae underwent a period of lethargy followed by the second moult and the third-stage larvae commenced a period of growth reaching a length of 79 mm. at 28 weeks after infection in the liver of mice. In rats the growth of the larvae was slower for the first 2 months, but eventually they reached more or less the same proportions as in mice. The intestinal caecum appeared at a length of 3–4 mm., but there was no development of the reproductive organs throughout the third stage and no evidence of the third moult in rodents.

Fifty carpet snakes were autopsied and searched for larvae and adults of A. robertsi; in two snakes third-stage larvae were found in the aorta; in one snake the third moult was observed in the wall of the stomach and oesophagus; in three snakes the fourth moult was observed in the wall of the stomach; in twenty-six snakes adults were found.

Experimental infection of laboratory-reared carpet snakes showed that infection with embryonated eggs resulted in second-stage larvae in the tissues which did not develop further. Infection with third-stage larvae, resulted in two distinct migratory patterns depending upon the maturity of the larvae administered. Larvae from the liver of laboratory rats which had been infected less than 12 weeks previously, migrated to various tissues, especially the aorta, of the snake, where they remained coiled in cysts filled with clotted blood for periods up to 112 days. Growth occurred within these cysts, but no evidence of moulting was observed. In contrast, larvae from the liver of laboratory rats infected 12 weeks or more previously, and from mice infected for 8 weeks or more, underwent the third moult in the wall of the oesophagus and stomach of the snake.

With the onset of the fourth stage, the development of the reproductive organs became evident and continued during the fourth stage. It appeared that the fourth stage may occur in two phases, possibly depending on the size of the third-stage larva at the time of ingestion. Some experimental infections indicated that third-stage larvae may give rise to attached fourth stage larvae, probably capable of active growth. Other observations indicated that fourth-stage larvae may remain encapsulated in the wall of the stomach or oesophagus until sex differentiation is completed, after which the fourth moult occurs and the adult parasite emerges, leaving two sheaths of the same length within the capsule.

The functional significance of each of the larval stages is discussed and it was concluded:—that the first-stage larva is one of tissue differentiation, whereby development proceeds to the infective stage; that the second stage represents a migratory phase without structural changes; that the third stage represents a growth phase, characterized by considerable increase in size, but without further radical changes in differentiation.

In contrast, the fourth stage is characterized by absence of growth, inability to migrate, and by marked structural changes in the reproductive organs, whereby the sexes are differentiated. Evidently this development may take place while the fourth stage is attached to the wall of the stomach or oesophagus, or while the larva remains in the capsule in a state of quiescence.

The fourth moult may occur in the attached state, but usually occurs within the capsule. After it is completed, the adult may remain for an indefinite period within the capsule with the two sheaths of the third and fourth stage. The emergence of the adult worms may be influenced by the arrival of food in the stomach. Once this phase is initiated, both growth and reproductive activity ensue during the adult stage.

This work was financed by a research grant from the University of Queensland. The writer wishes to acknowledge the valuable assistance of Miss Ann Pritchard.

Three strains of Eimeria acervulina and 3 strains of E. mivati were compared. E. acervulina was characterized by the ovoidal shape of its oocysts and their rapid sporulation, small first-generation schizonts containing few merozoites, and its inability to complete development in the chorio-allantois of chicken embryos. E. mivati had more rounded oocysts with a Longer sporulation time, larger first-generation schizonts containing twice as many merozoites and it developed readily in the chorio-allantois. Pre-patent periods were variable but generally shorter with E. acervulina. A strain of E. mivati attenuated by repeated embryo passage showed a reduced pre-patent period.

A specific extracellular proteinase, degrading selectively the cecropin-based defence system of insects, is secreted into the larval body during parasitism of the greater wax moth by the Heterorhabditis bacteriophora/Photorhabdus luminescens complex and by phase 1 of P. luminescens. The proteolytic digestion of insect inducible cecropin-like immune molecules was demonstrated by the disappearance of the Galleria mellonella cecropins and purified Hyalophora cecropin B peptide PAGE bands upon exposure to infected extracts, and a similar abrogation of antibacterial activity using an agar diffusion assay. Proteolytic activity of infected extracts produced by nematode/bacterial complex and phase 1 variant of P. luminescens was shown to be correlated with cecropin-inhibitory activity, suggesting that this anti-cecropin agent may be responsible for the ability of bacteria to establish infection and the insecticidal nature of H. bacteriophora. Antibacterial activity of Galleria lysozyme and that of chicken egg-white lysozyme to which P. luminescens is insensitive, was unaffected by H. bacteriophora proteinase.

A large number of fresh-water Invertebrates has been examined and the parasites obtained from them include examples of the commoner groups to be met with in any area surveyed. Six larval Trematodes have been described in detail, and by means of direct animal experiment two of them have been definitely related to known adults. Of these two one is the larva of Notocotylus seineti Fuhr., and is doubtfully Cercaria monostomi v. Linst., while the other is the larva of Echinoparyphium recurvatum v. Linst., and is described here in detail for the first time. The four xiphidiocercariae described are new. Data relating to the activity, duration of free life, and process of encystment of cercariae within the bodies of secondary intermediate hosts is also given.

Effect of the parasite on the host. The disruption of the tissues brought about by the presence of sporocysts or rediae in the liver of a mollusc injures the host, and in many cases brings about its death. The gonads also are often attacked and completely destroyed. This latter feature of parasitic castration has been observed by Giard (1888) among certain species of Limnaea, Planorbis and Paludina attacked by sporocysts. Brown (1926) states that the gonads are rarely infected. As regards the encysted stages of cercariae these appear to do very little harm to their hosts even when present in large numbers. These observations are in agreement with those of Lebour (1912) for the sporocyst, rediae, and encysted stages of marine Trematodes.

Double infection. I have found no instance of a double infection among the species described. In the literature, several records show the parasitism of two or more species of cercariae, within one and the same host. The occurrence of two species is most commonly met with, and as a rule one is in predominance. Sewell (1922) states that double infection is not common in India. Faust (1917), on the other hand, has found as many as four trematode species within the same host individual (Planorbis trivolis). Hesse (1923) states that “every large Limnaea peregra examined was heavily infected with sporocysts of either of the two species, but it was rare to find both together.” Brown (1926) in the neighbourhood of Birmingham has found three examples of associated xiphidiocercariae and furcocercariae, one example of xiphidiocercariae and echinostome cercariae, and two examples of echinostome cercaria, all from Limnaea stagnalis L.

The sheep ked has been largely eradicated in the UK but persists in the feral Soay sheep of St Kilda in the Outer Hebrides. Sheep keds transmit Trypanosoma melophagium, but parasitaemias are typically cryptic and this trypanosome has not been recorded in the St Kilda sheep. Trypanosomes were detected by PCR in preserved keds and were also found in gut smears from live keds; one infected gut was used to establish the trypanosome in vitro. Examination of the morphology of bloodstream forms from culture confirmed its identity as T. melophagium. Most keds were found to harbour the trypanosome, particularly those collected from lambs. DNA was extracted from preserved keds and from trypanosomes grown in vitro. Sequence analysis of the small subunit ribosomal RNA (SSU rRNA) gene and the spliced leader transcript showed the T. melophagium sequences to be very similar to those from T. theileri. A partial sequence of the ked SSU rRNA gene was also obtained. The close genetic relationship of T. melophagium and T. theileri suggests that T. melophagium represents a lineage of T. theileri that adapted to transmission by sheep keds and hence became a specific parasite of sheep.

The unique environment of the Mediterranean Sea makes fish stock assessment a major challenge. Stock identification of Mediterranean fisheries has been based mostly from data on biology, morphometrics, artificial tags, otolith shape and fish genetics, with less effort on the use of parasites as biomarkers. Here we use some case studies comparing Mediterranean vs Atlantic fish stocks in a multidisciplinary framework. The generalized Procrustes Rotation (PR) was used to assess the association between host genetics and larval Anisakis spp. datasets on demersal (hake) and pelagic (horse mackerel, swordfish) species. When discordant results emerged, they were due to the different features of the data. While fish population genetics can detect changes over an evolutionary timescale, providing indications on the cohesive action of gene flow, parasites are more suitable biomarkers when considering fish stocks over smaller temporal and spatial scales, hence giving information of fish movements over their lifespan. Future studies on the phylogeographic analysis of parasites suitable as biomarkers, and that of their fish host, performed on the same genes, will represent a further tool to be included in multidisciplinary studies on fish stock structure.

The red poultry mite, Dermanyssus gallinae, is one of the most economically deleterious ecto-parasites of layer hens worldwide. D. gallinae is difficult to eliminate from infested poultry farms, and even to study, because it resides on the host only during the bloodmeal at night, and hides in the crevices of poultry houses during the day. Here, the life-cycle of D. gallinae was reproduced entirely in vitro. Mites were incubated in a glass pipette at 30 °C, 60–95% relative humidity and total darkness. A feeding apparatus, composed of a membrane, reservoir and blood was fitted on the pipette during bloodmeals. We tested feeding rates on blood mixed with 1 of 3 anti-coagulants (EDTA, heparin and trisodium citrate) at different concentrations, and biological and artificial membranes. The best engorgement and survival rates for all 3 haematophagous life-stages of the parasite were observed in 1-day-old chick membranes and heparinized (0.02 mmol/ml) blood. We then describe the steps in developing a complete self-sustaining in vitro life-cycle. A colony of mites was maintained in vitro for 7 generations. Losses in the first generation were heavy, but survival had multiplied 5-fold by the fifth generation. We hypothesize that heavy mortality rates during the first life-cycle correspond to selective pressure: only the mites which fed and survived in vitro were able to reproduce.

The monogenean Gyrodactylus salaris Malmberg, 1957 is an economically important parasite on Atlantic salmon whereas the morphologically very similar G. thymalli Žitňan, 1960 on grayling is considered harmless. Even molecular markers cannot unambiguously discriminate both species. The nuclear internal transcribed spacer (ITS) sequences are identical in both species, and although mitochondrial cytochrome oxidase I (COI) sequences show substantial variation, no support for monophyly of either species is found. Analysis of nucleotide sequences of the intergenic spacer (IGS) have, however, been interpreted as support for 2 species. Here, IGS and COI sequences from 81 G. salaris and G. thymalli specimens of 39 populations across the species' distribution range were determined. Mitochondrial diversity was not reflected in the nuclear marker. Since various 23 bp IGS repeat types usually differ by just one nucleotide and sequences primarily differ in the number and order of repeat types, alignments may be biased and arbitrary, impeding meaningful phylogenetic analyses. The hypothesis that parasites on rainbow trout represent hybrids of both species is rejected. The presence or absence of particular repeat types is not considered informative. We interpret the IGS data as support for G. salaris and G. thymalli being a single species.