Among approximately eighty larvae of Trachea secalis, gathered from the same locality near Cape Town, South Africa, the incidence of microsporidian infection has been found to be 100%. In the majority of cases the parasite had heavily involved the lower portion of the gut, whereas the rectum and the upper portion of the gut were never infected. In severe cases the gut tissue was practically destroyed and replaced by an almost solid mass of spores. Except during the stages preceding spore formation, the infected portion of tissue can be detected by the unaided eye. When spores have been produced in large numbers, the involved area, which may be no larger than the head of a pin, and is usually located within the posterior third of the gut, becomes white and opaque, and contrasts sharply with the healthy surrounding tissue. The latter is transparent, and appears dark, owing to the colour of the contents. At a later stage it is not unusual to find the infected zone in the form of a narrow band which encircles the gut. The infection then spreads upwards and downwards. Finally, the entire lower portion of the gut becomes white and chalky. With the exception of the gut contents the parasite has not been found elsewhere in the body of the host.

The lobate ctenophore Mnemiopsis leidyi is a periodically abundant and voracious plankton predator in coastal waters along the east coast of the United States. In the 1980s it was accidentally introduced to the Black Sea where it caused a dramatic reduction in fisheries. We investigated how M. leidyi is affected by infestation with parasitic larvae of the sea anemone Edwardsia lineata. Infested M. leidyi contained 1–30 (median 7) E. lineata larvae. Within M. leidyi most larvae had their mouth in the gastrovascular system near the aboral end of the pharynx. Parasitic E. lineata ingested all food previously ingested and pre-digested by M. leidyi. Non-infested M. leidyi had higher growth rates than infested individuals, which had zero or negative growth rates. Egg production was similar for infested and non-infested M. leidyi of similar size. Simulation based on the empirical data suggests that growing, non-infested, M. leidyi are expected to have a larger life-time egg production than infested shrinking individuals. E. lineata could be at least partially responsible for the sharp decline of M. leidyi populations in fall in US coastal waters. Advantages and disadvantages of E. lineata as a potential candidate for the control of the artificially introduced M. leidyi population in the Black Sea are discussed.

Echinococcus multilocularis survived, strobilated and matured sexually in the small intestine of 6-week-old male golden hamsters that were either non-treated or treated with prednisolone tertiary-butylacetate (PTBA), following oral administration of 20000 protoscoleces. Non-treated hamsters harboured the adult worms for up to 25 days post-infection (p.i.). Hamsters treated with PTBA from the day of infection (day 0 p.i.) harboured more adults than the non-treated, and their survival periods were extended. Moreover, a remarkable improvement in worm recovery, development and survival periods was observed in hamsters additionally treated with PTBA on days — 14 and — 12 p.i., and the worm development including proglottisation, sexual maturation and egg formation was comparable with that in dogs. With the present results it is suggested that Echinococcus/rodent systems represented by the E. multilocularis/golden hamsters may rejuvenate the current stagnant research on host-parasite interactions of the definitive host-stage and egg-stage of Echinococcus.

Erythrocyte invasion assays are described for two species of rodent malaria, namely Plasmodium berghei and P. c. chabaudi. These invasion assays are simple, are carried out using a candle jar and allow a number of assays to be performed simultaneously. Our results demonstrate that both rodent malaria species show an in vitro preference for reticulocytes although the preference of P. c. chabaudi for these cells is not as marked as that of P. berghei. The details of our invasion assays and our results obtained are discussed.

1. A qualitative and semi-quantitative analysis of the free amino acids in the haemolymph of Rhodnius prolixus has been made by paper chromatography.

2. Twenty-one amino acids or related compounds were detected of which histidine appears at the highest concentration.

3. The α-amino-N concentration of haemolymph is among the lowest values recorded for insect haemolymphs.

4. A substance corresponding in position to thyroxine has been detected in haemolymph of a few immature insects, and is formed if iodate is added to freshly withdrawn haemolymph.

I wish to record my great appreciation to the late Professor P. A. Buxton, C.M.G., F.R.S., for his valuable assistance and criticism during this study and to members of the staff for helpful discussions. The study forms part of a Thesis for the degree of Ph.D. approved by the University of London, and was financed by the South African Council for Scientific and Industrial Research whose generous support I acknowledge with pleasure.

To assess whether apoptosis occurs in pig brain granulomas due to Taenia solium cysticerci, brain tissues from 30 pigs naturally infected with T. solium cysticercosis were evaluated by terminal deoxynucleotidyl transferase-end labelling (TUNEL) staining. In addition, tissues were stained with CD3 marker to identify T lymphocytes. Examination of TUNEL-stained tissues showed apoptotic cells in early lesions that contained viable cysticerci. Apoptotic cells were primarily found interspersed with normal cell types, and were mostly located in the inflammatory infiltrate. Late or advanced granulomas with disintegrated scolices did not show TUNEL-positive cells. CD3+ cells were found in both early and advanced lesions and apoptosis mainly co-localized with CD3+ T lymphocytes. This suggests that these cells are constantly undergoing apoptosis and thus die as soon as they arrive at the site of infection. Apoptosis indeed may be one way by which T. solium cysticerci down-regulate the host's cellular immune response in early cysticercosis. Therefore, further research is needed to establish if other cells besides T-lymphocytes are also a target for destruction by cysticerci in early cysticercosis as well as studies to assess if cysteine protease is expressed by viable cysticerci in situ.

Renal infections by parasitic ciliates were studied in adult snails of Helix aspersa aspersa and Helix aspersa maxima collected from 2 mixed rearing system-based heliciculture farms located in Galicia (NW Spain). The occurrence of ciliates was also examined in slugs (Deroceras reticulatum) invading the greenhouses where first growing and fattening of snails is carried out. Histological examinations revealed a severe destruction of the renal epithelium in heavily infected hosts. Three ciliate isolates, one from each host species, were obtained and grown in axenic cultures. Cultured and parasitic ciliates were characterized morphologically and morphometrically. In addition, the encystment behaviour, the occurrence of autogamy, and the sequences of the mitochondrial cytochrome-c oxidase subunit 1 (cox1) and the small subunit ribosomal RNA (SSU rRNA) genes were also studied in the 3 isolates. A polymorphic life cycle involving resting and reproductive cysts, together with the morphological and morphometrical characteristics and the confirmation that autogamy occurs within cysts, demonstrate that our ciliates belong to the species Tetrahymena rostrata (Kahl, 1926) Corliss, 1952. The 3 isolates formed a well-supported clade using both genetic markers, and were clearly separate from the strain ATCC® 30770™, which has been identified as Tetrahymena rostrata. We argue that our Spanish isolates should be regarded as Tetrahymena rostrata, and that the ATCC isolate should be regarded as a misidentification as neither cytological nor cytogenetical support for its identity has been presented.

The possibility of coproantigen detection in the diagnosis of strongyloidiasis was investigated in rats experimentally infected with Strongyloides ratti. A capture ELISA was developed using affinity-purified polyclonal antibodies raised in rabbits against adult and filariform larval somatic antigens. The first detection of coproantigen coincided with patency and the coproantigen level remained elevated even when the parasite count was low. Following challenge infection, when examination of stool for larvae or ova was negative, coproantigen was detected by anti-adult somatic capture ELISA. Despite the use of antisera raised against crude worm extracts, the test was specific showing only low cross-reactivity with Necator americanus and Syphacia muris.

American cutaneous leishmaniasis (ACL) is a complex disease with a rich diversity of animal host species. This diversity imposes a challenge, since understanding ACL transmission requires the adequate identification of reservoir hosts, those species able to be a source of additional infections. In this study we present results from an ACL cross-sectional serological survey of 51 dogs (Canis familiaris), where we used diagnostic tests that measure dog's exposure to Leishmania spp. parasites. We did our research in Panamá, at a village that has undergone significant ecosystem level transformations. We found an ACL seroprevalence of 47% among dogs, and their exposure was positively associated with dog age and abundance of sand fly vectors in the houses of dog owners. Using mathematical models, which were fitted to data on the proportion of positive tests as function of dog age, we estimated a basic reproductive number (R0 ± s.e.) of 1·22 ± 0·09 that indicates the disease is endemically established in the dogs. Nevertheless, this information by itself is insufficient to incriminate dogs as ACL reservoirs, given the inability to find parasites (or their DNA) in seropositive dogs and previously reported failures to experimentally infect vectors feeding on dogs with ACL parasites.

1. The envelope surrounding Polymorphus minutus during its development in Gammarus pulex has been found to be a capsule produced by a wound healing haemocytic reaction of the host. The haemocytic reaction is stimulated when the parasite stretches the connective tissue serosa of the host's gut.

2. The capsule is a thin, acellular structure, consisting of a protein-carbohydrate complex like that constituting host connective tissue. This material is produced and deposited by the haemocytes.

3. The ability of the haemocytes to produce this protein-carbohydrate material is considered to be the mechanism which ensures the growth of the capsule during the subsequent development of the parasite in the haemocoel.

4. A second layer appears within the capsule just before the parasite reaches the cystacanth stage. This layer is believed to be produced by the parasite.

5. The relevant literature is reviewed, and it appears that the envelopes surrounding all developing Acanthocephala, which have been studied to date, are probably capsules originating in the manner described above.

I am very grateful to Dr P. Tate for advice and encouragement during this work, and to Dr George Salt, F.R.S., for helpful discussions and criticism of the manuscript.

A qualitative and quantitative analysis was made of the release of surface-associated molecules from developing Dirofilaria immitis infective-stage larvae (L3). D. immitis L3s were labelled with 125I using an Iodogen catalysed reaction and either maintained in culture or placed in chambers that were implanted into Lewis rats. The larvae released 10–20% of the labelled material each day during the first 4 days of in vitro and in vivo development. The loss of surface-labelled peptides from developing larvae corresponded with an increase in the amount of trichloroacetic acid-precipitable radioactivity found in the culture medium. SDS—PAGE analysis of the labelled material showed that the same 35 and 6 kDa components found in larval extracts were shed into culture medium by the developing parasites. Metabolic labelling studies and experiments in which larvae were labelled after different times in culture indicated that, once released, the surfaceassociated molecules were not replaced, and that this net loss of surface peptides resulted in a reduction in the antigenic potential of the cuticular surface. Antibodies from both immunized rabbits and naturally infected dogs immunoprecipitated the 35 kDa component. In contrast, the 6 kDa molecule was not recognized by the antibodies in any of the sera tested. Shedding of surface peptides and reducing surface antigenicity may represent mechanisms by which D. immitis infective-stage larvae evade immune attack.

Our freshwater fishes have for long been a subject of some economic interest and in consequence their diseases and their parasites have received quite a considerable amount of attention. Much has been written on the subject, even in this country, and it has formed the basis of not a little speculation and possibly some results of economic value. As usual, however, more attention has been devoted to the matter on the continent and in America. It is, nevertheless, gratifying to find that Mclntosh (1863) was one of the first to realise the important help to be derived from a scientific study of fish parasites in investigations on such problems as migration, etc. His work has been greatly amplified by the later researches of such men as Hofer (1904) and Zschokke (1884–1914) in Europe, and Ward (1908–11) in America, to mention only a few well-known names which have been prominent in this line of investigation.

To date, large-scale production of Cryptosporidium parvum oocysts has only been achieved by amplification in neonatal calves and sheep. Many laboratories currently depend on supplies from external sources and store oocysts for prolonged periods which results in progressive loss of viability. Six to 8-week-old interferon γ receptor knockout (IFNγR-KO) mice on a C57BL/6 background were inoculated by gavage (2000 oocysts/animal). Fecal pellets were collected daily from 7 days post-infection (p.i.) up to 2 weeks p.i. Intestinal oocyst yield was assessed at days 11, 12 and 14 p.i. by homogenization of intestinal tissues. Ether extraction and one or more NaCl flotations were used to purify oocysts. Total recoveries averaged 2·6×106 oocysts/mouse from fecal material and 3·8×107 oocysts/mouse from intestinal tissues. Overall, 2·3×109 purified oocysts were obtained from 60 mice. Recovered oocysts were capable of sporulation and were shown to be infectious both in vitro and in vivo. Oocyst amplification was achieved in only 11–14 days with minimal expense. The simplicity of this method presents a practical alternative for the routine passage, maintenance and storage of C. parvum in biomedical laboratories.

We counted the numbers of pupae of two ectoparasitic flies (Protocalliphora sp. and Ornithomyia sp.) in the nests of a passerine bird, the pied flycatcher (Ficedula hypoleuca) to find out if their prevalence or intensity are affected by long-term environmental pollution by a copper smelter and whether such an interaction would have impacts on birds' breeding success. Fecal metal concentrations of F. hypoleuca nestlings were used to explore direct association between metal levels and parasite prevalence, but we also included other explanatory factors in our analysis, such as timing of breeding, brood size, ambient temperature, habitat quality and host population density. We found that environmental pollution decreased the prevalence of Protocalliphora via changed habitat quality but did not affect the prevalence of Ornithomyia. The prevalence of neither ectoparasite was, however, directly related to ambient metal levels. Both ectoparasites showed higher prevalence when ambient temperature during the nestling period was high, emphasizing the potential of climate change to modify host–parasite relationships. The prevalence of Ornithomyia was further highest in dense F. hypoleuca populations and late broods. Nestling survival decreased with increasing infestation intensity of Ornithomyia while no association was found for Protocalliphora. Despite relatively low numbers and overall weak effect of parasites on survival, the possible delayed and/or sublethal effects of these ectoparasites call for further studies. Our results suggest that pollution-related effects on avian ectoparasite numbers are species-specific and reflect habitat changes rather than direct toxic effect of heavy metals.

The immune response affects host's survival and reproductive success. Insurmountable immune function has not evolved because it is costly and there is a trade-off between other life-history traits. In previous studies several factors such as diet and temperature have been proposed to cause interpopulation differences in immune response. Moreover, the insect immune system may be functionally more protective upon secondary exposure, thus infection history may associate with the immune response. Here we measured how geographical location and parasite burden is related to variation in immune response between populations. We included 13 populations of the Northern Damselfly Coenagrion hastulatum (Odonata: Coenagrionidae) in Finland over a latitudinal range of 880 km to this study. We found that water mites associated strongly with the immune response at interpopulation level: the more the mites, the higher the immune response. Also, in an alternative model based on AIC, latitude and individual size associated with the immune response. In turn, endoparasitic gregarines did not affect the immune response. To conclude, a positive interpopulation association between the immune response and the rate of water mite infection may indicate (i) local adaptation to chronic parasite stress, (ii) effective ‘induced’ immune response against parasites, or (iii) a combined effect of both of these.

Guinea worm disease, dracunculiasis or dracontiasis, is an ancient disease with records going back over 4500 years, but until the beginning of the 20th century, little was known about its life cycle, particularly how humans became infected. In 1905, Robert Thomas Leiper was sent by the British colonial authorities to West Africa to investigate the spread of Guinea worm disease and to recommend measures to prevent it. While carrying out his investigations, he made important contributions to the aetiology, epidemiology and public health aspects of Guinea worm disease and provided definitive answers to many outstanding questions. First, he tested the validity of previous theories; second, he confirmed the role of water fleas, which he identified as Cyclops, as the intermediate hosts in the life cycle; third, he investigated the development of the parasite in its intermediate host; and fourth, he recommended measures to prevent the disease.

[The crustacean Order Cyclopoida in the Family Cyclopidae contains 25 genera, including Cyclops which itself contains over 400 species and may not even be a valid taxon. It is not known how many of these species (or indeed species belonging to related genera) can act as intermediate hosts of Dracunculus medinensis nor do we know which species Fedchenko, Leiper and other workers used in their experiments. It is, therefore, best to use the terms copepod, or copopoid crustacean rather than Cyclops in scientific texts. In this paper, these crustaceans are referred to as copepods except when referring to an original text.]

Leiper described the remarkable changes that took place when an infected copepod was placed in a dilute solution of hydrochloric acid; the copepod was immediately killed, but the Dracunculus larvae survived and were released into the surrounding water. From this, he concluded that if a person swallowed an infected copepod, their gastric juice would produce similar results. He next infected monkeys by feeding them copepods infected with Guinea worm larvae, and thus conclusively demonstrated that humans became infected by accidentally ingesting infected crustaceans. Based on these conclusions, he advocated a number of control policies, including avoidance of contaminated drinking water or filtering it, and these preventive measures paved the way for further research. The challenge to eradicate Guinea worm disease was not taken up until about seven decades later since when, with the support of a number of governmental and non-governmental organizations, the number of cases has been reduced from an estimated 3·5 million in 1986 to 25 in 2016 with the expectation that this will eventually lead to the eradication of the disease.

The epidemiology of coccidiosis involving Eimeria perforans, E. media, E. stiedae, E. irresidua, E. magna and E. piriformis was studied for a period of 35 months in a free-living population of wild rabbits, confined to an experimental enclosure.

Relations between the seasonal fluctuations of the above species, on the one hand, and severity of infection and age and social status of hosts, on the other hand, based on the oocyst counts from 2326 faecal samples collected at regular monthly intervals, are indicated.

Mortality within the population was analysed, and coccidiosis was found not to be responsible for the general mortality pattern.

Thanks are due to Mr M. Dudzinski of the Division of Mathematical Statistics, C.S.I.R.O., Canberra for statistical analysis of the data. Mr H. McL. Gordon and Dr J. C. Boray of MacMaster Laboratories, C.S.I.R.O., Sydney, and Dr W. L. Nicholas, of the Australian National University, Canberra, read the manuscript and offered many helpful suggestions. Messrs E. R. Hesterman and D. Purchase of the Wildlife Survey Section, C.S.I.R.O., Canberra, provided valuable technical assistance.

Perkinsus marinus is responsible for a chronic disease (Dermo) of the Eastern oyster, Crassostrea virginica. In order to simulate the in vivo environment more closely, a chemically defined medium (JL-ODRP-3) was supplemented with tissue homogenate extracts or plasma from oysters possessing varying degrees of susceptibility to P. marinus infection. In media supplemented with extracts from highly susceptible oysters (C. virginica), P. marinus cells secreted elevated amounts of a set of low molecular weight serine proteases (LMP: 30–45 kDa) as assessed by enhanced digestion within gelatin-substrate SDS–PAGE gels. Oyster species of low susceptibility (C. gigas and C. ariakensis) did not exhibit this ability to upregulate P. marinus LMP expression. Oyster extract supplementation also led to pronounced changes in P. marinus cellular morphology, such that the cells were comparable to those observed within naturally infected oysters.

The morphology and development of Trypanosoma cobitis during its life-cycle in the blood of 6 species of River Lee fish, and also in its invertebrate vector, the fish leech Hemiclepsis marginata L., are described in detail.

A microsporidium was isolated from larvae of Spodoptera litura (Fabricius) collected from Tamil Nadu, India. This microsporidian species is monomorphic, disporous and develops in direct contact with the cytoplasm of the host cell. The nuclear configuration of merogonic and sporogonic stages was diplokaryotic. The merogonic proliferative stage was unusual that normal development with 1, 2 and 4 binucleated forms were common, while large multinucleate meronts containing 8 and 12 small compact horseshoe-like diplokaryotic nuclei were also observed. The fresh spores were typically ovocylindrical in shape, with a mean size of 3·91×1·91 μm and the polar filament length was ~90 μm. Infection was systemic with mature spores produced in the midgut, nervous tissue, muscles, labial glands, gonads, tracheae, epidermis, Malpighian tubules and, most extensively, fat body tissues. The new isolate was highly pathogenic to S. litura larvae. Host specificity tests performed on 37 non-target hosts of 5 different insect orders revealed that the new isolate is pathogenic only to lepidopteran insects. We sequenced the 16S small subunit rRNA (SSU rRNA) gene of the isolate and compared it with 72 non-redundant microsporidian sequences from the GenBank. Based on the light microscopic studies and phylogenetic analyses, the new isolate is assigned to the genus Nosema. Significant differences in the SSU rRNA sequence were identified when compared with the type species Nosema bombycis and other closely related species viz., Nosema spodopterae. Structural differences were also observed in the 16S SSU rRNA between the new isolate and the two above-mentioned microsporidian pathogens. We conclude that the microsporidian isolate reported here is distinctly different from the other known species and is likely to be a new species.