The microfibrillate component of the laminated layer of Echinococcus granulosus equinus contains, except for the zone adjacent to the germinal layer, aggregates of electron-dense bodies displaying a sub-structure of electron-lucent spheres. The tegumentary syncytial cytoplasm contains randomly distributed electron-dense granules, many occurring near the apical plasmalemma, although exocytosis was rarely seen. Granules, similar in size and sub-structure to the bodies of the aggregates, also occur in the internuncial connexions and tegumentary cytons, suggesting that they may be produced in the cytons and released into the laminated layer via the internuncial connexions and tegumentary cytoplasm. Cysts incubated for 0·5–2·5 h in serum- and non-serum-containing media showed differences from non-incubated cysts. The distal half of the syncytium contained a progressive increase in the number of granules (distal:proximal 1·9:1 at 2·5 h; cf. 1:1 in non-incubated cysts), and exocytosis of granules into the laminated layer adjacent to the cyst had occurred. This cannot be attributed wholly to serum proteins. Cysts incubated for 21 h appeared ‘normal’, suggesting re-establishment of an equilibrium. Since the matrix of the laminated layer is considered homologous to the glycocalyx of other cestodes, the possible protective role played by the granules/bodies, characteristic of Echinococcus spp., is discussed.

Between August 1978 and July 1979, freshwater gastropods were collected at monthly intervals from 9 different non-lacustrine habitats in the Mwanza region of Tanzania. Of a total of 11708 gastropods representing 14 species, 1748 (14–9%) were infected with trematode sporocysts and/or rediae. Altogether 38 morphologically distinguishable ‘species’ of cercariae were recovered (13 furcocercous, 10 xiphidiocercaria, 6 echin-ostome, 4 cystophorous, 3 gymnocephalous and 2 amphistome species), 22 of which did not conform to previously described African species. The majority (63–8%) of all mature infections were xiphidiocercariae. Biomphalaria pfeifferi, B. sudanica and Ceratophallus natalensis each yielded 11 species of cercariae. Lymnaea natalensis had the highest overall prevalence of infection (36–9%). Cercaria guttera from L. natalensis accounted for 20–4% of all recovered trematode infections and C. blukwa from Biomphalaria accounted for 18–4% of all infections; the high prevalence of these two xiphidiocercariae may alter the transmission patterns of Fasciola gigantica and Schistosoma mansoni, respectively. S. mansoni was recovered from both B. sudanica (22 of 2393 infected) and B. pfeifferi (79 of 1913 infected); S. haematobium (or related species) was recovered from Bulinus (Physopsis) nasutus (50 of 1503 infected) and to a lesser extent from B. (P.) africanus (6 of 186 infected). The findings are discussed in relation to the biological control of trematode diseases in Tanzania.

A survey was made of the helminth fauna of 657 herring gulls (474 ‘adults’ and 183 chicks) in northern Caernarvonshire and Anglesey during the period July 1962 to November 1964. A total of 31 species of helminths were identified (10 species of Trematoda, 11 of Cestoda and 10 of Nematoda), including 1 new species, four new host records and three new British records. Two species of Mallophaga were identified from the birds. In three cases (Gymnophallus deliciosus, Paricterotaenia porosa and Capillaria contorta) a significant difference was found in the burden carried by male and female birds. ‘Adult’ birds were generally found to be more heavily infected with helminths than the chicks, with the exception of the nematode Cyathostoma lari, which was found more frequently in the chicks. A new intermediate host for Capillaria contorta was noted, namely Eiseniella tetraedra.

Three species of Trematoda, two of Cestoda, and two of Nematoda were found to be cyclic (seasonal) in their time of appearance. Tetrabothrius spp. appeared most frequently in winter, whilst Anomotaenia larina was found only during the summer months. C. lari showed a primary peak of appearance in summer, with a secondary peak in winter. Capillaria contorta appeared in high numbers throughout the year.

The distribution of helminths within the birds was also examined. Gymnophallus deliciosus was generally found in the gall bladder, whilst Parorchis acanthus was found only in the rectum. Intestinal trematodes were normally found in the mid-third of the small intestine (e.g. Spelotrema excellens, Himasthla elongata). In the case of C. lingua, however, peak numbers were found in the duodenum, whilst Brachylaemus fuscatus was found most frequently in the posterior third of the small intestine. Cestodes appeared most frequently in the anterior or posterior thirds of the small intestine (e.g. Tetrabothrius spp., Anomotaenia micracantha). Hymenolepis cirrosa showed two peaks of infection along the length of the small intestine, a small one in the anterior third, a much larger one in the posterior third. Attempts were made to correlate the helminth burden found with the food eaten by the birds and the availability of intermediate hosts.

I should like to thank Mr J. Hobart and Dr I. V. Herbert for all the help that they have given me in the preparation of this manuscript, and also the bodies that gave me permission to shoot birds on their land, particularly the Nature Conservancy. Finally, I would like to thank the S.R.C. for the grant that made this work possible.

1. A study has been made of the effect of acriflavine upon Bodo caudatus. The drug has the property of producing a percentage of modified Bodos without parabasal bodies but no permanently aparabasal strains have been produced.

2. A technique was devised whereby the resistance, as judged by two different types of survival experiment, could be correlated with the percentage of modified Bodos produced when the strain is put to grow in an ascending series of concentrations of acriflavine incorporated in the culture medium.

3. The peak of the count of altered Bodos in relation to the concentration in which it occurs is found to be the index of the sensitiveness of the strain at that date. The maximum reaction as gauged by the numbers of modified Bodos produced in an untreated strain of average sensitiveness is about 70 to 80 per cent., and this occurs in so low a concentration as 1/1,000,000. 1/5,000,000 gives a count below the maximum and 1/50,000,000 produces only 1 to 4 per cent. according to the sensitiveness of the strain.

4. The mass untreated strain was originally derived from a single Bodo isolated in the autumn of 1926. This strain in 1927–28 was used as the mass untreated strain in the experiments. Its resistance was found to fluctuate from below a capacity to evolve with great difficulty in 1/50,000 to a somewhat feeble development in 1/10,000 acriflavine incorporated plates. The mass untreated strain was never able to evolve in plates containing 1/5000 acriflavine at any time.

5. Strains grown from single isolations from the untreated mass culture showed different degrees of natural resistance. The most resistant clones could develop in 1/5000 acriflavine incorporated plates, but not in 1/2000. The great importance of this natural range of resistance in estimating an acquired drug fastness is emphasized. Strains which had been made resistant could be brought to live continuously in 1/1500 acriflavine incorporated plates, but no evolution was obtained in 1/1000.

6. Evidence that drug fastness in Bodo caudatus is due to the interaction of selective inheritance and the actual modification of the quality of the Bodo by evolution in the drug is given. The modification is not apparently a mutation, it is a heritable piling up of changes in a particular direction.

7. A high resistance once acquired is retained through prolonged cultivation upon drug-free media. A gradual loss occurs, partly by a dilution through multiplication of the character impressed and partly by the survival of variants of less resistance to acriflavine, but of perfect viability in other circumstances and the competition of these within the strain. The loss of resistance is greatly accelerated in single cell cultures (clones) isolated from the resistant strains, but up to the present no treated strain has entirely lost the effect of the original exposures to the drug. The longest time elapsing between the creating of a partially resistant strain and its test for resistance above that of the untreated culture is one year.

8. The bearing of the data obtained in Bodo caudatus upon the condition found in trypanosomiasis and upon certain aspects of chemotherapy in this group is discussed.

9. Bodo caudatus being an organism without conjugation and therefore without bi-parental inheritance and consequently lacking the reorganising effect that such a periodic closing of the cycle produces, affords an example of a labile organism capable of being progressively altered within certain limits under the influence of the environment.

There is an essential requirement for highly sensitive tools that will differentiate nematode parasites of animals and plants to the species level. For studying host range, genetic variation, virulence and resistance, the availability of well defined populations is vital. Many nematode species cannot be identified with certainty using traditional morphological or morphometric techniques. This is particularly the case for the more accessible developmental stages that, depending on the particular group concerned, live as eggs and larvae in the environment or as micro-filariae that circulate in the blood or inhabit the skin. Morphological identification of these stages requires specialized expertise and is extremely time consuming. Immunological assays have their place in nematode identification but they do not discriminate between current and previous infections, an essential requirement in many epidemiological and prevalence studies. In addition to being highly sensitive, DNA-based methods of detection define present over past infection and are not dependent on the parasite stage. Many types of methodology are available for the detection and definition of nematode DNA. This paper reviews these methods citing examples that have been used with success in the laboratory as well as the field.

Successful metazoan parasitism, among many other factors, requires a supply of nutrients and the removal of waste products. There is a prerequisite for a parasite-defined vasculature. The angiogenic mechanism(s) involved presumably depend on the characteristics of the tissue- and vascular system-dwelling, parasitic helminths. Simplistically, 2 possibilities or a combination of both have been considered in this review. The multifactorial induction of parasitic helminth-associated neovascularization could arise through, either a host-, a parasite- or a host-/parasite-dependent, angiogenic switch. Most studies appear to support the first and third hypotheses, but evidence exists for the intrahepatic cestode Echinococcus multilocularis, the free-living nematode Caenorhabditis elegans and the intravascular trematode Schistosoma mansoni for the second inference. In contrast, the nematode anti-coagulant protein NAPc2 from adult Ancylostoma caninum is also an anti-angiogenic factor.

Buffalo-adapted Theileria parva causes Corridor disease in cattle. Strict control measures therefore apply to the movement of buffalo in South Africa and include mandatory testing of buffalo for the presence of T. parva. The official test is a real-time hybridization PCR assay that amplifies the V4 hypervariable region of the 18S rRNA gene of T. parva, T. sp. (buffalo) and T. sp. (bougasvlei). The effect that mixed T. parva and T. sp. (buffalo)-like infections have on accurate T. parva diagnosis was investigated in this study. In vitro mixed infection simulations indicated PCR signal suppression at 100 to 1000-fold T. sp. (buffalo) excess at low T. parva parasitaemia. Suppression of PCR signal was found in field buffalo with mixed infections. The T. parva-positive status of these cases was confirmed by selective suppression of T. sp. (buffalo) amplification using a locked nucleic acid clamp and independent assays based on the p67, p104 and Tpr genes. The incidence of mixed infections in the Corridor disease endemic region of South Africa is significant, while the prevalence in buffalo outside the endemic area is currently low. A predicted increase of T. sp. (buffalo)-like infections can affect future diagnoses where mixed infections occur, prompting the need for improvements in current diagnostics.

The effect of acquired immunity on the duration of Plasmodium falciparum infections is unclear, although this is an important term in models of malaria transmission. It is problematical to determine the duration of infections because of the difficulty of distinguishing persisting infections from new ones, and because parasite densities are often transiently below the limit of detection. We recently developed a dynamic model for infection incidence, clearance and detection of multiple genotype P. falciparum infections and fitted it to a panel dataset from a longitudinal study in Northern Ghana. We now extend this model to allow for seasonal and age variation in infection rates and also age dependence in clearance and in detectability of infections. These models indicate that there is seasonal variation in the infection rate, and age dependence in detectability. The best fitting models had no age dependence in infection or clearance rates, suggesting that acquired immunity mainly affects detectability.

The aim of this study was to evaluate cytokine expression in 22 Leishmania infantum naturally infected dogs, in order to correlate this parameter with the clinical status of infected animals. After 4 and 8 months from the first diagnosis of Leishmania infection, clinical and laboratory examination of dogs was performed and peripheral blood mononuclear cells (PBMC) were isolated. The cytokine profile was analysed in terms of IFN-gamma, IL-4, IL-10 and TNF-alpha mRNA expression in cultured PBMC by a semi-quantitative reverse transcriptase-PCR. Thirteen out of 22 Leishmania-infected dogs remained asymptomatic in the follow-up, while 9 showed clinical signs of leishmaniasis. IL-4, IL-10, TNF-alpha and IFN-gamma mRNA levels were not significantly different in asymptomatic compared to symptomatic animals 4 months from the diagnosis of Leishmania infection, but were significantly higher in symptomatic versus asymptomatic dogs after 8 months from diagnosis. In addition, IL-4, IL-10 and TNF-alpha mRNA levels significantly increased only in symptomatic dogs at 8 months, in comparison to the levels found at 4 months. These results show a mixed Th1 and Th2 cytokine response in Leishmania-infected dogs, with higher cytokine expression in dogs with manifest clinical disease, during the second follow-up after 8 months from the first diagnosis of infection.

Immune mapped protein 1 (IMP1) is a newly discovered protein in Eimeria maxima. It is recognized as a potential vaccine candidate against E. maxima and a highly conserved protein in apicomplexan parasites. Although the Neospora caninum IMP1 (NcIMP1) orthologue of E. maxima IMP1 was predicted in the N. caninum genome, it was still not identified and characterized. In this study, cDNA sequence encoding NcIMP1 was cloned by RT-PCR from RNA isolated from Nc1 tachyzoites. NcIMP1 was encoded by an open reading frame of 1182 bp, which encoded a protein of 393 amino acids with a predicted molecular weight of 42·9 kDa. Sequence analysis showed that there was neither a signal peptide nor a transmembrane region present in the NcIMP1 amino acid sequence. However, several kinds of functional protein motifs, including an N-myristoylation site and a palmitoylation site were predicted. Recombinant NcIMP1 (rNcIMP1) was expressed in Escherichia coli and then purified rNcIMP1 was used to prepare specific antisera in mice. Mouse polyclonal antibodies raised against the rNcIMP1 recognized an approximate 43 kDa native IMP1 protein. Immunofluorescence analysis showed that NcIMP1 was localized on the membrane of N. caninum tachyzoites. The N-myristoylation site and the palmitoylation site were found to contribute to the localization of NcIMP1. Furthermore, the rNcIMP1-specific antibodies could inhibit cell invasion by N. caninum tachyzoites in vitro. All the results indicate that NcIMP1 is likely to be a membrane protein of N. caninum and may be involved in parasite invasion.

Immunopathological and ultrastructural studies were carried out on the gut of 30 specimens of powan Coregonus lavaretus (L.) from Lake Piediluco, Italy. The digestive tracts of 10 (33·3%) of the powan were found to harbour an acanthocephalan Dentitruncus truttae (Sinzar 1955). The numerous trunk spines of D. truttae reduced the number of mucosal folds near the parasite site of infection. The acanthocephalan induced hyperplasia and hypertrophy of the intestinal mucous cells and many worms were surrounded with an adherent mucous gel. Near the site of acanthocephalan attachment, the number of mucous cells was significantly higher (P<0·01) in comparison to those found in uninfected intestines. Rodlet cells (RCs) were present in the epithelial layer in both infected and uninfected fish, with no significant difference in the numbers observed (P>0·05). In infected intestine, mast cells were more abundant than in uninfected gut (P<0·01). Migration of the mast cells and their intense degranulation at the site of infection were suggested. Immunohistochemical tests applied to sections of intestinal tissue of both infected and uninfected powan revealed that the parasitized C. lavaretus had a larger number of mast cells positive for met-enkephalin and serotonin antisera.

Yellow-eyed penguins (YEPs) have suffered major population declines over the past 30 years, with no single cause established. Leucocytozoon was first identified in yellow-eyed penguins in 2005. During the 2008/09 breeding season, a high mortality was seen in both mainland yellow-eyed penguins as well as those on Enderby Island of the Auckland Islands archipelago. A high overall prevalence of Leucocytozoon spp. in association with a high incidence of chick mortality was observed during this period on Enderby Island. One chick had histological evidence of leucocytozoonosis with megaloschizonts in multiple organs throughout its body. In addition, a high prevalence (73·7%) of Leucocytozoon was observed by PCR in the blood of adult Enderby yellow-eyed penguins taken during the 2006/07 season. These findings were different from the low prevalence detected by PCR on the coast of the South Island (11%) during the 2008/2009 breeding session and earlier on Campbell Island (21%) during the 2006/2007 breeding session. The Leucocytozoon spp. sequences detected lead us to conclude that the Leucocytozoon parasite is common in yellow-eyed penguins and has a higher prevalence in penguins from Enderby Island than those from Campbell Island and the mainland of New Zealand. The Enderby Island yellow-eyed penguins are infected with a Leucocytozoon spp. that is genetically distinct from that found in other yellow-eyed penguin populations. The role of Leucocytozoon in the high levels of chick mortality in the yellow-eyed penguins remains unclear.

This paper is based on the study of a large material derived from various sources and containing a great number of abnormal specimens of Pediculus humanus, namely 155 hermaphrodites, besides abnormalities other than sexual which occur very rarely among insects.

Praziquantel (500 mg/kg) administered orally to BALB/c mice with secondary equine E. granulosus daily for 21, 30 or 30 + 30 days without the drug resulted in the majority of cysts, using bench criteria of turgidity and eosin exclusion, being assessed as ‘alive’. Ultrastructural examination of 54 of these ‘alive’ cysts did not support this conclusion. They all showed increased vesiculation of the germinal layer leading, in many, to the loss of its integrity. Increased mitochondrial numbers occurred frequently. The longer drug treatments appeared to have greater effects on the germinal layer of ‘alive’ cysts and there was no detectable re-establishment of structural organization within 30 days after drug withdrawal. Subjectively, there was no substantial difference between cysts from 4-month and 9-month infections or between affected peritoneal and hepatic cysts. Tissue from collapsed cysts was necrotic. Peak serum levels of praziquantel (6430–6136 μg/l) occurred 5–10 min after drug administration (500 mg/kg) and dropped rapidly to less than 10 μg/l at 3 h. In an in vitro study at praziquantel concentrations of 1000 and 5000 μg/l over a 10-day period, most cysts were judged ‘alive’ by bench criteria but showed ultrastructurally a time- and concentration-dependent loss of integrity identical to that seen in vivo. Turgidity and eosin exclusion therefore underestimate the effect of praziquantel and the results indicate that in vitro experiments can fulfil a legitimate preliminary role in a hydatid chemotherapy programme.

In the laboratory, yields of infective 3rd-stage larvae of Trichostrongylus tenuis were determined by temperature when moisture was adequate. On the moor, eggs in caecal faeces did not develop to infective larvae during the winter. In summer, development did occur and yields of infective larvae were related to temperature: greatest yields were obtained when mean monthly soil surface temperatures ranged between 76 and 103°C. Rainfall was unimportant, as was desiccation. During summer the mean monthly mortality of infective larvae was 44% but over winter survival was negligible.

An epidemiological survey of the distribution and abundance of Diplostomum spathaceum in farmed rainbow trout (Salmo gairdneri) from Mill of Cantray trout farm (Nairn, Morayshire) involved monthly sampling of fish over a 3-year period. Diplostomurn metacercariae were present in both the lens and aqueous humour of infected fish, and these have been treated separately throughout the study. The infection period was normally between May and September each year and transmission of the parasite from snail to fish did not occur at temperatures below 10°C. The prevalence and abundance of both lens and humour metacercariae reached a maximum in September. The cleansing and application of a molluscicide (copper sulphate) to the raceways in spring resulted in a 56% reduction in the numbers of metacercariae infecting trout during the following summer. However, no further improvement in parasite control was recorded when the treatment was repeated in the following year. Experiments using caged fish indicated that diplostomiasis was confined to certain areas of the farm only and that the infection rate of rainbow trout with D. Spathaceum cercariae was correlated (P < 0·01) with water temperature. The results of the study indicated that it is possible by regular cleaning and use of molluscicides to keep the intensity of diplostomiasis at such a level that rainbow trout do not become severely affected. However, as with other parasitic diseases, a combination of control methods will probably be required to eradicate the disease completely from trout farms.

The clearing action of mosquito larvae in turbid water and their scarcity or absence in clean water, is an old-established popular belief in mosquito ridden districts of both the old and new world. If the presence of certain species of Anopheles larvae in clear running water, where they doubtless feed on algae, be excepted, it is probable that this general observation is in the main correct. The fact that numbers of mosquito larvae are frequently present in the small collections of clear water which occur in the cut ends of bamboos, the axils of leaves, or the smaller rock or root pools, is an apparent but not a real contradiction of the correctness of this popular belief, because in these instances one of two possibilities may have occurred. Either the large number of dormant eggs which hatched when rain first filled the receptacle was sufficient to check and control bacterial or yeast development from the start, or, as is more likely in the case of root or rock pools, the turbidity due to bacteria or yeasts had been rapidly cleared as the rapacity of the quickly growing larvae increased beyond the source of nutriment.

Among the functional changes observed in L. truncatula infected with F. hepatica were those of growth, reproduction and mortality. For the first 3 weeks after infection there was no difference between the growth of infected and uninfected groups of snails. Thereafter there was a temporary accelerated growth which occurred between the fourth and seventh weeks after infection. The onset of this period of rapid growth in the different age groups of infected snails coincided with the time of migration of the rediae into the hepatopancreas. Of more significance was the influence of infection on the reproduction of the snail. There was a sharp decline in oviposition 2–3 weeks after infection, followed by a complete cessation of egg production at the end of the fifth week. Once oviposition ceased, it was not resumed and there was no self-cure. Contrary to general belief, infected groups of L. truncatula have been found to live longer than the uninfected controls. With isolated snails, however, there was a tendency for the uninfected snails to live longer than the infected ones. The possible interpretation of the discrepancies between isolated and mass cultured snails are discussed. The hepatopancreas and the gonad (ovotestis) were the two structures directly affected by the infection. Establishment of the rediae in the hepatopancreas invariably resulted in parasitic castration.

A new microsporidian parasite of a freshwater cladoceran from southern Sweden is described using light and electron microscopical methods. Development comprises 2 merogonial sequences, the first resulting in a cluster of 8 merozoites, the second in a chain of 4 merozoites. Each secondary merozoite develops into a sporont which divides into 2 sporoblasts, each of which develops into a spore. The spores are broadly oval and in fresh smears measure about 6 μm in length, with a single nucleus and a posterosome. The polar filament is about 40 μm long, of even thickness throughout, and appears as 15—18 coils in a single layer. The anchoring disc is small and the polaroplast is composed of 2 lamellar parts. Outside the plasma membrane of the sporont a 5-layered, electron-dense substance is produced, which further differentiates into endo- and exospore, an electron-dense substance occurring patchily on the exospore and a pansporoblast membrane. During development the sporoblasts and the young spores are connected by a dense substance. Mature spores appear single or paired. The pansporoblast membrane is composed of 2 structurally different layers, namely a thin outer, single membrane and an inner layer composed of tubular structures. It is connected to the spore coat by patches of the dense substance. The new microsporidium is considered to belong to a new genus of the family Telomyxidae, and its systematic relationship with this and the related family Tuzetiidae is discussed. A survey of microsporidia from Cladocera is included.