Twenty-one sheep were killed after having been kept for varying times on a pasture contaminated with Haemonchus contortus. The proportions of linguiform A to linguiform B phenotypes were estimated for the H. contortus populations of each sheep. They gave further evidence that the linguiform B phenotype gradually replaces the linguiform A phenotype during the summer. Given the genetic basis of the phenotype it is pointed out that this seasonal change would appear to be inconsistent with any theory stating that essentially only one generation of worms is involved in the yearly outbreaks of disease.

There were no differences in mean intestinal worm burdens 8 days after subcutaneous injection of 4000 infective larvae of Strongyloides ratti into rats in dioestrus, pro-oestrus, oestrus and metoestrus. Thus, changes in the hormonal environment of the migrating larvae dependent on the oestrous cycle did not alter the worms' destination or affect their potential for development. In particular, the results are prima facie evidence that prolactin is not, on its own, responsible for the re-orientation of larvae in the tissues of nursing mothers. Other sources of variability in experimental S. ratti infections are analysed and the ‘exact dose’ technique offered as a corrective for some procedural errors.

The fate of 75Se-labelled schistosomula in mice treated at 24 h post-infection with either Ro 11–3128 or oxamniquine, compared to untreated controls, was followed by compressed organ autoradiography. No difference in the total percentage of schistosomula detected as foci was found between the three groups at each sampling time. However, the distribution of schistosomula was altered. In oxamniquine-treated mice there was a delayed migration from the skin relative to controls and fewer parasites in total appeared to reach the lungs. In Ro 11–3128 treated mice very few parasites left the skin. Ro 11–3128 treatment induces resistance to challenge whereas oxamniquine does not. The fate of challenge schistosomula in previously infected Ro 11–3128 treated mice was also compared to that in control mice. There was evidence for delayed or reduced migration from the skin of Ro 11–3128 treated mice. Significant death of challenge parasites occurred in the lungs, or post-lung sites in both control and treated mice. It was not possible to conclude that any of the late attrition was immune-dependent in the treated mice and the results appeared to indicate that a significant fraction of parasite death occurred at the skin stage.

This study assessed the virulence of Trypanosoma evansi, the causative agent of camel trypanosomiasis (surra), affecting mainly camels among other hosts in Africa, Asia and South America, with high mortality and morbidity. Using Swiss white mice, we assessed virulence of 17 T. evansi isolates collected from surra endemic countries. We determined parasitaemia, live body weight, packed cell volume (PCV) and survivorship in mice, for a period of 60 days’ post infection. Based on survivorship, the 17 isolates were classified into three virulence categories; low (31–60 days), moderate (11–30 days) and high (0–10 days). Differences in survivorship, PCV and bodyweights between categories were significant and correlated (P < 0.05). Of the 10 Kenyan isolates, four were of low, five moderate and one (Type B) of high virulence. These findings suggest differential virulence between T. evansi isolates. In conclusion, these results show that the virulence of T. evansi may be region specific, the phenotype of the circulating parasite should be considered in the management of surra. There is also need to collect more isolates from other surra endemic regions to confirm this observation.

Under the name of Zografia notonectae n.g., n.sp., Bogoyavlensky (1922) has described a new organism which he found parasitic in the body cavity of Notonecta (Hemiptera) collected in ponds in Russia (government of Moscow).

Gene expression is known to vary significantly during the Leishmania life-cycle. Its monitoring might allow identification of molecular changes associated with the infective stages (metacyclics and amastigotes) and contribute to the understanding of the complex host-parasite relationships. So far, very few studies have been done on Leishmania (Viannia) braziliensis, one of the most pathogenic species. Such studies require, first of all, reference molecular markers. In the present work, we applied differential display analysis (DD analysis) in order to identify transcripts that might be (i) candidate markers of metacyclics and intracellular amastigotes of L. (V.) braziliensis or (ii) potential controls, i.e. constitutively expressed. In total, 48 DNA fragments gave reliable sequencing data, 29 of them being potential markers of infective stages and 12 potential controls. Eight sequences could be identified with reported genes. Validation of the results of DD analysis was done for 4 genes (2 differentially expressed and 2 controls) by quantitative real-time PCR. The infective insect stage-specific protein (meta 1) was more expressed in metacyclic-enriched preparations. The oligopeptidase b showed a higher expression in amastigotes. Two genes, glucose-6-phosphate dehydrogenase and a serine/threonine protein kinase, were found to be similarly expressed in the different biological samples.

Engorged, parasitic water mites were observed to decrease the growth rate and to increase the stadium length of nymphal backswimmers. Unengorged mites were found to have no effect on the host. The extended stadium lengths of parasitized hosts should reduce the instantaneous rate of natural increase of populations of parasitized hosts because this rate is sensitive to any factor that delays the onset of reproduction.

This is an investigation of the impact of salinity on transovarial transmission and burden of a microsporidian sex ratio distorter in the inter-tidal crustacean Gammarus duebeni. Exposure of parasitized mothers to increased salinity during the gonotrophic cycle caused an increase in parasite burden in the follicle cells and a decrease in burden in the oocytes. It appears that salinity impedes parasite transmission from the follicle cells to the oocytes during host oogenesis. A lower proportion of the young were infected in broods from elevated salinity and, in infected offspring, parasite burden was lower than in control embryos. Parasite replication occurred during embryogenesis. However, the pattern of parasite growth did not differ between salinities, indicating that differences in parasite burden could be attributed to a reduction in the initial parasite burden transmitted to the gamete, rather than to a reduction in parasite replication during host embryogenesis. We discuss our findings with respect to parasite/host dynamics and the ecology of the host.

This study aimed to evaluate associations between toxoplasmosis and psychiatric disorders in Taiwan based on the National Health Insurance Research Database, Taiwan (1997–2013). Patients newly diagnosed with toxoplasmosis formed the case group (n = 259), and the control group included propensity-score matched patients without toxoplasmosis (n = 1036). The primary outcome was incidence of psychiatric disorders. Cox proportional hazards regression and stratified analyses were performed to examine risk of developing specific psychiatric disorders between patients with and without toxoplasmosis. Patients with toxoplasmosis had significantly higher incidence of psychiatric disorders than those without toxoplasmosis (P = 0.016). A significant difference was found in numbers of psychiatric disorders between the two groups during 14 years of follow-up (log-rank P < 0.001). Those with toxoplasmosis had significantly higher risk of bipolar disorder [adjusted hazard ratio (aHR = 3.60, 95% confidence interval (CI) = 2.07, 7.26), depression (aHR = 4.94, 95% CI = 2.15, 11.80) and anxiety (aHR = 5.36, 95% CI = 2.98, 25.88), but no significant between-group differences were found for schizophrenia and other psychiatric disorders. In conclusion, the present nationwide population-based analysis revealed that Toxoplasma gondii infection in Taiwan significantly increases the risk for developing bipolar disorder, depression and anxiety, but not for schizophrenia and other psychiatric disorders.

In May 1921 and again in February 1923 a specimen of the copepod Acartia clausi Giesbrecht, from which was emerging a parasitic trematode, occurred in the townets. The first, taken between Rame Head and the Mewstone, outside Plymouth Sound, was a full grown female Acartia, nearly dead, which had the skin broken between the first and second segments of the metasome where the trematode was emerging. The second, taken close to the shore from near the mouth of the Cattewater, was a full grown male which was alive but the skin was broken between the cephalosome and metasome where the trematode was emerging in a similar way to the first.

A trickle infection experiment was undertaken to study in detail the population dynamics of Oesophagostomum dentatum in pigs. Three groups of 32 pigs were inoculated via the feed twice weekly with 100 (Group A), 1000 (Group B) or 10000 (Group C) O. dentatum infective larvae (L3). Five pigs from each group were killed 2, 4, 8, 12, 16, and 20 weeks after the first inoculation (p.i.) to determine their worm burdens. Weekly faecal egg counts were determined. At slaughter, worms were counted, differentiated according to sex and developmental stage, and their length measured. Faecal egg counts ranked with dose rate until week 15, but later were more variable. The proportion of the total number of L3 administered which were recovered at slaughter inversely ranked with dose rate. In group C it decreased over time, whereas in groups A and B there was no consistent pattern. Worm fecundities (epg/female) in groups A and B were higher than in group C. The lengths of the female worms increased over time, whereas the lengths of the male worms remained approximately constant from week 8. The study suggests reduced establishment of incoming larvae and lower fecundity of the female worms at high dose levels.

In the last years, there were a growing number of studies using the metric H2′ to calculate complementary specialization in host–parasite interaction networks. However, only a few studies have explored the sensitivity of H2′ to network dimensions (i.e. species richness and number of interactions), which consequently could generate studies that are not comparable among them or lead to biased conclusions. In this study, we used the recent published study conducted by Rivera-García et al. in 2016 involving host–bat fly networks as an example to call attention to the risk of using H2′ to calculate specialization for small matrices. After conducting analyses based on both empirical and simulated data, we show that H2′ values are strongly affected by randomly allocation of species interactions to another cell in the matrix for small networks and that therefore the results and conclusions presented in Rivera-García et al. in 2016 are only an artefact of the dataset used. Therefore, we fully recommended taking into account the careful use of small networks to measuring specialization in host–parasite interactions.

Intracellular recordings have been made from neurones in the head ganglia of Ascaris. The neurones had low resting membrane potentials of –21±9 mV (n = 78) and a relatively high input resistance (e.g. 25 MΩ for a 100 μm cell). In all cases the intracellular location of the recording electrode was verified by injection of the fluorescent marker, 5, 6-carboxyfluorescein (CBXF). To ascertain whether or not the low membrane potential was due to impalement damage, the same neurone was recorded from using two microelectrodes. The membrane potential following the first impalement by a 20 MΩ 3 M KCl electrode was –38 mV and following the second impalement by a 80 MΩ CBXF (for subsequent intracellular labelling) electrode was decreased to –34 mV. Input resistance of these cells was estimated using both single and two electrode intracellular recording techniques and in both cases yielded a relatively high value for the size of cell (e.g. 25 MΩ for a 100 μm cell). Neurones labelled by intracellular injection of the fluorescent marker 5, 6-carboxy-fluorescein were morphologically simple and lacked extensive arborizations. The dorsal ganglion is a discrete structure consisting of only 3 neurones. Here we compare the morphological properties of these neurones to those described in the dorsal ganglion of Caenorhabditis elegans. The whole mount preparation of Ascaris ganglia thus provides a useful model to study the functional properties of neurones in nematode central nervous system and presents the possibility to assess central sites of action for anthelmintics.

The fully embryonated egg of Notocotylus attenuatus is shown to contain a sporocyst, an opercular cord and apparently 2 cells which are situated outside the sporocyst. One of these cells is rich in glycogen whereas the other contains a variety of inclusions. These contents are indicative of a truncated life-cycle which omits the miracidium, an observation as yet unique among the Digenea.

The pentastomid parasite, Raillietiella frenata, is native to Asia where it infects the Asian House gecko, Hemidactylus frenatus. This gecko has been widely introduced and recently R. frenata was found in introduced populations of cane toads (Rhinella marina) in Australia, indicating a host-switch from introduced geckos to toads. Here we report non-native adult R. frenata infecting the lungs of native cane toads in Panama. Eight of 64 toads were infected (median = 2·5, range = 1–80 pentastomids/toad) and pentastomid prevalence was positively associated with the number of buildings at a site, though further sampling is needed to confirm this pattern. We postulate that this pattern is likely due to a host shift of this parasite from an urban-associated introduced gecko. This is the first record of this parasite infecting cane toads in their native range, and the first instance of this parasite occurring in Central America.

1. The width and length of eggs of Haemonchus contortus, Cooperia curticei, Trichostrongylus axei, T. vitrinus, Bunostomum trigonocephalum, Chabertia ovina, Oesophagostomum venulosum and Ostertagia spp. were measured.

2. Frequency distributions of the linear dimensions of the eggs of each species are given, together with the frequencies calculated on the assumption that the distributions are normal.

3. A method of species differentiation based on egg measurements is described, the method being based upon the statistical chances of eggs of different species falling into particular size classes.

4. The application of the method and the construction of a classifying scale are described.

Experimental intraperitoneal Taenia crassiceps cysticercosis in mice exhibits distinct genetical, immunological and endocrinological features possibly resulting from the complex interactive network of their physiological systems. Very notable is the tendency of parasites to grow faster in hosts of the female sex. It is also remarkable in the feminization process that the infection induces in chronically infected male mice, characterized by their estrogenization, deandrogenization and loss of sexual and aggressive patterns of behaviour. The proto-oncogene c-fos is a sex steroid-regulated transcription factor gene, expressed basally and upon stimulation by many organisms. In the CNS of rodents, c-fos is found expressed in association to sexual stimulation and to various immunological and stressful events. Hence, we suspected that changes in c-fos expression in the brain could be involved in the feminization of the infected male mice. Indeed, it was found that c-fos expression increased at different times during infection in the hypothalamus, hippocampus, less so in the preoptic area and cortex, and not in several other organs. The significant and distinctive regional changes of c-fos in the CNS of infected mice indicate that the brain of the host senses intraperitoneal cysticercosis and may also announce its active participation in the regulation of the host–parasite relationship. Possibly, the host's CNS activity is involved in the network that regulates the estrogenization and deandrogenization observed in the chronically infected male mice, as well as in the behavioural and immunological peculiarities observed in this parasitic infection.

It would appear from casual references in literature that the seals and their relatives are quite commonly infested with certain mites which occur in the nasal passages or even in the bronchial tubes. Although there are several such references, apparently in but three have the mites been named. In these three cases they have been referred to the Gamasid (or Dermanyssid) genus Halarachne. The first species, Halarachne halichoeri Allman, from Halichoerus gryphus, an Atlantic seal, was described in 1847; the second, H. americana Banks, from Monarchus tropicalis, which is also an Atlantic species, was described in 1896; the third, H. otariae Steding, from Otaria californica (which is known to American mammalogists as Zalophus cali-fornianus), was described in 1923. The specimens upon which this last species was based were obtained in Germany, although the host is a native of the west coast of North America.