The causal chain of parasite–host–environment interactions, the so-called ‘dual parasite environment’, makes studying parasites more complicated than other wild organisms. A sample of 65 282 fleas taken from 336 different locations were analysed for changes in the distribution, diversity and compensation of flea communities found on small mammals along an elevational diversity gradient ranging from the Pannonian Plain to the base of the Carpathian summits. The fleas were divided into four groups, which were derived from changes in abundance and occurrence determined from cluster analysis. They are (1) flea species whose range seems unrelated to any change in elevation; (2) species that avoid high altitudes; (3) a group that can be subdivided into two types: (i) host-specific fleas and (ii) mountains species and (4) species opting for high altitudes on the gradient or preferring lower to middle elevations below 1000 m. Our study showed a unimodal pattern of flea diversity along the elevational gradient. It indicated that seasonality significantly conditions changes in biodiversity and patterns of spatial change along the elevational gradient, with specific flea species influenced by their host, while the impact of environmental conditions is more pronounced in opportunistic flea species.

Hubei Province is one of the endemic regions with severe schistosomiasis in China. To eliminate schistosomiasis in lake and marshland regions, this study detected hotspots of schistosomiasis cases both spatially and spatiotemporally on the basis of spatial autocorrelation; clustering and outlier, purely spatial and spatiotemporal cluster analyses at the village level from 2013 to 2017 in Hubei Province. The number of cases confirmed positive by an immunodiagnostic test and etiological diagnosis and advanced schistosomiasis cases dramatically declined during the study period. Significant global spatial autocorrelation of schistosomiasis patients was found at the village level in the whole province in 5 years. Clustering and outlier analysis showed that most HH villages were mainly concentrated along the Yangtze River, especially in Jianghan Plain. Spatial and spatiotemporal cluster analyses showed that significant clusters of the schistosomiasis cases were detected at the village level. In general, space and spatiotemporal clustering of schistosomiasis cases at the village level demonstrated a downward trend from 2013 from 2017 in Hubei Province. High-risk regions included Jianghan Plain along the middle reach of Yangtze River and Yangxin County in the lower reaches of the Yangtze River in Hubei Province. To eliminate schistosomiasis, precise control and management of schistosomiasis cases should be strictly implemented. Moreover, comprehensive prevention and control measures should be continuously strengthened in these regions.

Dinobdella ferox is the most reported and studied leech species parasitizing mammalian mucus membranes. However, our knowledge of D. ferox during parasitizing and its effects on hosts has remained limited. To investigate the behaviour of D. ferox in the parasitic period and the subsequent host symptoms, the author was infested voluntarily with three juvenile leeches under regularly-conducted examinations of complete blood count (CBC) and nasal endoscopy (NE). After the first head protrusion of the parasitizing leech at the host nostril, the occurrence of bleeding-related symptoms decreased and ceased completely weeks before the end of the parasitic period. Negligible impacts of the parasitizing leech on the host were shown by CBCs, and a parasitizing leech was able to hide from NE despite being so large it at times protrudes out of the host nostril. Finally, parasitizing D. ferox were coaxed to emerge at the nostril by water only after their first head protrusion, indicating that non-invasive removal of parasitizing D. ferox before head protrusion might be difficult. Through the voluntary infestation, the full documentation of behaviours of D. ferox in the parasitic period and host symptoms shown in this study will promote better diagnoses and treatments of nasal leech infestation.

Chagas disease (CD) is caused by the intracellular protozoan parasite Trypanosoma cruzi and affects more than 10 million people in poor areas of Latin America. There is an urgent need for alternative drugs with better safety, broader efficacy, lower costs and shorter time of administration. Thus the biological activity of viniconazole, a chloroaryl-substituted imidazole was investigated using in vitro and in vivo screening models of T. cruzi infection. Ultrastructural findings demonstrated that the most frequent cellular damage was associated with plasma membrane (blebs and shedding events), Golgi (swelling aspects) and the appearance of large numbers of vacuoles suggesting an autophagic process. Our data demonstrated that although this compound is effective against bloodstream and intracellular forms (16 and 24 μ m, respectively) in vitro, it does not present in vivo efficacy. Due to the urgent need for novel agents against T. cruzi, the screening of natural and synthetic products must be further supported with the aim of finding more selective and affordable drugs for CD.

The variability within schistosome populations was explored using mixed populations of cercariae from multimiracidial snail infections and individual clones of Schistosoma mansoni cercariae obtained from monomiracidial snail infections. We investigated the heterogeneity between different clones of S. mansoni with respect to infectivity and metabolism. One difference between clones of cercariae was found in the recovery of adult worms from Balb/C mice. Recovery of adult worms was greater after infections with a mixed population than with a clonal population. To investigate some biochemical features of individuals in clones or mixed populations, the uptake of [35S]methionine into individual parasites and their membrane proteins was measured. Isoelectric focusing of a soluble membrane fraction: the frozen–thawed supernatant extracted from individual clones, showed the presence of proteins of isoelectric point between 7.2 and 8.2 in all clones. These proteins were less labelled with [35S]methionine in the clones than in the mixed population. It was concluded that basic proteins are synthesized by all clones and in the mixed population but at different rates. Differences in the rate of incorporation of [35S]methionine into the surface membranes of schistosomula and adult worms derived from individual clones are reported. In addition, a direct correlation between the percentage of recovery of adult worms from mice infected with individual clones of S. mansoni and the rate of incorporation of [35S]methionine into schistosomula of these particular clones was observed. It is suggested that the high rate of metabolism shown by an individual clone may account for the enhanced survival of the cercariae derived from that clone during penetration of the skin and migration through the vertebrate host. In order to examine individuals in a population of schistosomula, from a clone or mixed population, the lysosome-specific fluorescent probe LysoTracker DND-99 was used to label the parasites and quantitative fluorescent measurements were made on individual parasites. There were significant differences between clones and a mixed population. Furthermore, the variation between individuals from a mixed population was greater than from that in any clone, just as was found in the infectivity studies. Freshly transformed schistosomula of individual clones labelled with the LysoTracker DND-99 showed less variations in the quantitative uptake of the dye within a single clone when compared to the mixed population. We conclude that for any biochemical and biological parameter, a population of cercariae consists of individuals showing a wide range of values, with a much greater range in a mixed population. This variability is likely to have great relevance for infectivity of the final host and the efficacy of drugs and the immune system.

The formation of the definitive procercoid excretory system of the pseudophyllidean cestode Triaenophorus nodulosus has been investigated. This process can be divided into 3 main stages. In the first stage, active autophagic processes lead to the formation of intracellular excretory canals. In the second stage, the process of the autolysis is enhanced and the system of intercellular lacunae functioning as an excretory system is formed. A definitive excretory system of the procercoid forms at the next stage, by means of the migration and proliferation of undifferentiated cells replacing the lacunar system.

An important element in most approaches to the subject of parasitism is the consideration of environment. Parasites are set apart within animal ecology because they experience two environments, one the ‘external’ conditions and the other created by the living body of the host. As in any ecological system, external environmental conditions have a major influence on life history parameters: these conditions may be experienced directly by ‘off-host’ stages of a parasite or, to a greater or lesser extent, indirectly through the body of the host. However, uniquely in parasitic associations, the internal (host) environment has a dual influence on the physiological conditions encountered by parasites: first, the host buffers the external conditions (by homeostatic mechanisms moderating environmental fluctuations, by behavioural responses selecting appropriate habitat conditions, etc.), but second, the host creates a suite of hostile factors associated with immune defence. This living, reactive environment has no parallels elsewhere in free-living animal ecology: it has the characteristic of reacting specifically to kill the organisms within its boundaries.

Haemoproteus species (Haemoproteidae) are widespread blood parasites and are transmitted by Culicoides biting midges and Hippoboscidae louse flies. Although these pathogens may cause morbidity or mortality, the vectors and patterns of transmission remain unknown for the great majority of avian haemoproteids. Haemoproteus nucleocondensus has been frequently reported in Europe in great reed warblers Acrocephalus arundinaceus after their arrival from African wintering grounds, but this infection has not been found in juveniles at the breeding sites. The factors that prevent its transmission remain unclear. This study was designed to test whether the sporogony of H. nucleocondensus (lineage hGRW8) can be completed in Culicoides impunctatus, one of the most abundant European biting midge species. Wild-caught females were infected with H. nucleocondensus from great reed warblers. Microscopic examination and PCR-based methods were used to detect sporogonic stages and to confirm species identity. This study showed that H. nucleocondensus completes sporogony in C. impunctatus, suggesting that there are no obstacles to its transmission from the point of view of vector availability and average temperature in Northern Europe. We discuss other ecological factors which should be considered to explain why the transmission of H. nucleocondensus and some other Southern origin haemosporidians are interrupted in North Europe.

In this study, a microsporidian pathogen of the date moth (Apomyelois (Ectomyelois) ceratoniae, Zeller, 1839) also known as the carob moth, is described based on light microscopy, ultrastructural characteristics and comparative molecular analysis. The pathogen infects the gut and hemolymph of A. ceratoniae. All development stages are in direct contact with the host cell cytoplasm. Fresh spores with nuclei arranged in a diplokaryon are oval and measured 3.29 ± 0.23 μm (4.18–3.03 μm, n = 200) in length and 1.91 ± 0.23 μm (2.98–1.66 μm, n = 200) in width. Spores stained with Giemsa's stain measured 3.11 ± 0.31 μm (3.72–2.41 μm, n = 150) in length and 1.76 ± 0.23 μm (2.16–1.25 μm, n = 150) in width. Spores have an isofilar polar filament with 10-12 coils. An 1110 bp long alignment of the current microsporidium showed an SSU rRNA gene difference of only 0.0009, corresponding to >99.91% sequence similarity with Nosema fumiferanae, while RPB1 gene sequences were 98.03% similar within an alignment of 969 bp. All morphological, ultrastructural and molecular features indicate that the microsporidian pathogen of A. ceratoniae is the new isolate of the N. fumiferanae and is named here as Nosema fumiferanae TY61.

The impact of Toxocara canis infection of Balb/c mice mothers on the future immune response of their offspring towards reinfection with the same parasite was studied. Two groups of offspring, the first originating from the mothers infected with a single dose of 1000 Toxocara canis eggs and the second from non-infected mothers, were both challenged with 500 T. canis eggs per animal at 6 weeks of age. The proportions of spleen CD4+ and CD8+ T lymphocytes, the level of serum cytokines IFN-γ and IL-5, eosinophilia in peripheral blood, the production of specific antibodies and the number of migrating larvae were monitored. In both groups of offspring, the challenge infection resulted in an increase in CD4+ T-cell subtype in comparison with the non-infected healthy control, although after an initial decline a subsequent increase in CD8+ was observed. The immunoregulation index (CD4+/CD8+) was lower in the group of mice originating from infected mothers throughout the whole experiment compared to the offspring of non-infected mothers as well as in healthy control mice of the same age. In the offspring of infected mothers mainly, a reduced production of IFN-γ and of IL-5, suppressed eosinophilia and a higher level of protective antibodies was detected, compared to the control second group, in which the INF-γ concentration significantly increased after day 42 p.i. In the first group of offspring before challenge, 12·7±2·5 larvae in the brains and 32±2·1 larvae in the muscles transmitted from the infected mothers were detected. There was a significant reduction in larval recovery from brain on days 42 and 49 p.i. (56·7 and 56·8%, respectively), while from muscles in the same time there was a reduction of 46·7 and 39%, respectively, compared to the offspring of non-infected mothers. These results indicate a significant protective memory of immune mechanisms against T. canis induced in offspring of Toxocara-infected mother mice.

The ultrastructure of the pseudohaptoral squamodiscs of the monogenean Diplectanum aequans is described. The most prominent feature of the squamodisc is the presence of epidermally-embedded spines which are covered by the outer epidermal membrane. These spines, which are ‘hollow’, are composed of a moderately electron-dense material with denser fibrils embedded within it. The squamodisc epidermis is similar in appearance to the haptor epidermis, with the exception of the epidermis ‘inside’ the spines. Here the epidermis contains free ribosomes and stacks of alternating electron-lucent/electron-dense, membrane-bound sacs. The arrangement of the musculature of the spines is described. The free, prehensile, edges of the squamodiscs contain numerous radially orientated nerves, some of which are assumed to be mechano-receptors.

A new flagellate, Proteromonas hemidactyli sp.nov., is described from the large intestine of the lizard, Hemidactylus brooki, in Hyderabad, India. It is characterized by a long, slender and fusiform body, two similar but subequal flagella, a kidney-shaped sub-blepharoplastic body, a ribbon-like paranuclear body and a vesicular nucleus. A parabasal body is absent.

I am extremely grateful to Dr S. S. Qadri, Reader in Zoology, Osmania University, Hyderabad for his guidance and advice during the course of this work. I am thankful to Dr S. Mehdi Ali, Professor of Zoology, Marathwada University, and Dr S. N. Singh, Professor of Zoology, Osmania University, for providing me with laboratory and library facilities. Thanks are also due to the Council of Scientific and Industrial Research, New Delhi, for the award of a fellowship.

The survival, growth and development of Onchocerca lienalis 3rd-stage (L3) larvae implanted into mice within micropore chambers has been studied with a view to developing a vaccination model for studies of protective immunity in onchocerciasis. The influence of host genetics on worm recoveries and development (growth and moulting rate) was analysed in a panel of inbred mice (CBA, BALB/c, DBA/2, SJL, 129J, C57BL/10 (B10), C3H/He and NIH), together with mice of BALB and B10 backgrounds with different major histocompatibility complex (H-2) genes (BALB/c, BALB.K, BALB.B and B10, B10.D2/n, B10.BR, B10.S). Parasite recoveries and development were similar in all mouse genotypes tested. They were unaffected by procedures designed to block or modulate phagocytic cell function with carbon or carrageenan, or to suppress inflammation by treatment with hydrocortisone acetate. A comparison of chambers sealed with membranes designed to admit (5·0 μm pore size) or exclude (0·2 μm pore size) host cells demonstrated no effect on the percentage recovery of living larvae, although dead larvae were more frequently retrieved when cells were excluded. Recoveries and rates of development of larvae implanted into immunodeficient scid mice and athymic Hooded rats were similar to those recorded in immunocompetent controls. We conclude that host genetic factors and immunocompetence are not significant determinants of survival, growth or development of O. lienalis larvae implanted within micropore chambers into naive mice. Despite its limitations, the use of this system merits further investigation as an approach to the study of protective immunity against developing larvae in onchocerciasis.

Three new species of dactylogyrid monogeneans with three anchors are described: two of them, Eutrianchoratus magnum and E. minutus, from Ophiocephalus obscurus, and Heteronchocleidus ctenopomae from the anabantid Ctenopoma kingsleyae, all from south Ghana.

Analysis of the variation in the morphological patterns of the anchors and the bars in the known species of the Heteronchocleidinae suggests gradual specialization from an ancyrocephaliid type with two pairs of anchors to types with three anchors arranged in triangular symmetry.

Heteronchocleidinae occur on both ophiocephaliid and anabantiid fish in Southeast Asia as well as in West Africa.

The diagnosis of the genus Polycliphora gen. nov. is based on the large number of haptoral clamps and on their skeleton. The systematic position of the parasite is discussed. Among the Diclidophoridae, Polycliphora nezumiae gen. et sp. nov., becomes the type of a new sub-family.

Cyathocotyle bushiensis Khan 1962 is a digenean intestinal parasite of ducks that appears to be involved in seasonal mortality of the definitive host. Temperature dependence of egg hatching and miracidial survival at 25%C were experimentally investigated as part of a study on transmission of the larval stages. Maximum percentage of hatching was obtained at a temperature of 25%C, at which the average hatching time was 21·7 days. The average hatching time decreased linearly from 38·9 days to 9·8 days between 18 and 28%C. Eggs exposed to cold (4%C) prior to incubation at 25%C were significantly less successful in hatching than fresh eggs incubated at the same temperature. Their hatching percentage was much reduced and their average hatching time was increased. Similarly, eggs collected in late autumn (as opposed to summer) and incubated at 23%C had significantly lower hatching success and significantly increased average hatching time. At 25%C, the average life-span of the miracidia was 8·8 h. These results are compared with similar data from other digenean species and their significance is discussed in relation to transmission to the first intermediate host in climatic conditions prevalent in endemic areas.

The development of Carmyerius exoporus Maplestone in the snail Anisus nata-lensis Krauss is described with the emphasis laid on the redial and cercarial productivity of the rediae of the first and subsequent generations.

The miracidium gives rise to one sporocyst. From 25 to 32 germinal cells present in the miracidium, only six to eleven develop into embryo balls in the sporocyst and, of these, only three to nine develop into rediae of the first generation.

The redia of the first generation gives birth to daughter rediae and cercariae. No alternation in the development of redial and cercarial embryos was noted in the rediae of C. exoporus and a small number of redial embryos was observed to develop alongside the more numerous cercarial embryos throughout the life of the first generation rediae.

The rediae of the second and subsequent generations also give birth to daughter rediae and cercariae.

The cercariae leave their parent redia when they are still immature and continue the development in the snail tissue.

Two attempts to transfer immunity against N. muris to rats using the lymph node and spleen cells from actively immunized donors were unsuccessful. Experiments showed that the rats were sufficiently inbred, that the transfer technique was satisfactory, and that the donors were adequately immunized. The rats' competence as donors for adoptive transfer was demonstrated with sheep red cells as antigen. The adoptive transfer of immunity against sheep red cells was successful in recipients whose donors had sheep red cells only and no N. muris. There was no detectable transfer of immunity against N. muris or sheep red cells to recipients whose donors had received both.

We are very grateful to Miss Kathleen O'Brien for technical assistance, to Professor P. B. Medawar, F.R.S., for his help and advice and to Dr E. J. Delorme for showing us Professor M. F. A. Woodruff's skin-grafting technique.

Among the earlier investigators, attempts to cultivate trypanosomes in NNN medium were made by Petrie (1905) and Brumpt (1906a), who isolated Trypanosoma denilewskyi and T. granulosum, respectively, but failed to estabilsh them in subculture.

Cestodes collected from birds of El Recreo, Zelaya, Nicaragua are reported. Sacciuterina mathevossiani sp.nov. from Rhamphocaenus rufiventris is the only species in the genus with 32 rostellar hooks, each 22–24 μm long, and with 5–9 testes. Angularella beema (Clerc, 1906) Strand, 1928, from Iridoprocne albilinea, is partially redescribed. Also reported are Dilepis undula (Schrank, 1788) Weinland, 1858, from Turdus grayi; Anomotaenia mutabilis (Rudolphi, 1819) Baer et Bona, 1960, from Florida caerulea; Ophiovalipora lintoni (Olsen, 1937) Coil, 1950, from Butorides viriscens; Hymenolepsis pellucida Fuhrmann, 1906, from Ramphocelus paserinii and Gymnostinops montezuma; and Raillietina (R). maplestonei Southwell, 1930, from Amazona autumnalis. All are new records for Nicaragua.

Thanks are expressed to Dr Thomas R. Howell, University of California who, assisted by Mr John Zeiger, collected and identified the hosts. The collecting of birds was supported in part by a grant to Dr Howell from the University of California Association in Tropical Biogeography. Gratitude is also expressed to Dr W. H. Coil, University of Kansas, who examined some of the specimens and offered helpful suggestions, and to Miss Dorothy B. Segal, Beltsville Parasitological Laboratory, for checking the records on Angularella.