Comparisons of successful and failed attempts to eradicate livestock ticks reveal that the social context of farming and management of the campaigns have greater influence than techniques of treatment. The biology of ticks is considered principally where it has contributed to control of ticks as practiced on farms. The timing of treatments by life cycle and season can be exploited to reduce numbers of treatments per year. Pastures can be managed to starve and desiccate vulnerable larvae questing on vegetation. Immunity to ticks acquired by hosts can be enhanced by livestock breeding. The aggregated distribution of ticks on hosts with poor immunity can be used to select animals for removal from the herd. Models of tick population dynamics required for predicting outcomes of control methods need better understanding of drivers of distribution, aggregation, stability, and density-dependent mortality. Changing social circumstances, especially of land-use, has an influence on exposure to tick-borne pathogens that can be exploited for disease control.

Recent have shown the relationship between Ecto-Nucleoside-Triphosphate-Diphosphohydrolases (Ecto-NTPDases or ecto-nucleotidases) and virulence and infectivity in trypanosomatids. In this work, the inhibition of the ecto-ATPase activities and promastigote growth of Leishmania amazonensis by CrATP was characterized. Furthermore, this compound was used to investigate the role of ecto-nucleotidase in the interaction of L. amazonensis with resident peritoneal macrophages obtained from BALB/c mice. CrATP partially inhibits the ecto-ATPase activity, presenting Ki values of 575·7±199·1 and 383·5±79·0 μm, in the presence or absence of 5 mm MgCl2, respectively. The apparent Kms for ATP (2·9±0·5 mm to Mg2+-dependent ecto-ATPase and 0·4±0·2 mm to Mg2+-independent ecto-ATPase activities) are not significantly altered by CrATP, suggesting a reversible non-competitive inhibition of both enzymes. When CrATP was added to the cultivation medium at 500 μm, it drastically inhibited the cellular growth. The interaction of promastigote forms of L. amazonensis with BALB/c peritoneal macrophages is strongly affected by CrATP. When the parasites were treated with 500 μm CrATP before interacting with macrophages, the adhesion and endocytic indices were strongly reduced to 53·0±14·8% and 39·8±1·1%, respectively. These results indicate that ecto-nucleotidase plays an important role in the infection process caused by Leishmania amazonensis.

Parvicapsula minibicornis is a myxozoan parasite implicated in mortalities of both juvenile and pre-spawning adult salmon in the Pacific Northwest of North America. Disease severity and presentation varies between salmon species and geographical localities. To better characterize population structure of the parasite, we sought genetic markers in the P. minibicornis ribosomal RNA gene. We compared samples from California with the type specimen from British Columbia, identified sequence variations, and then sequenced 197 samples from fish, river water and the parasite's polychaete worm host. Although DNA sequences of the parasite were >98·9% similar, there was enough variation to define 15 genotypes. All genotypes were detected in fish samples, although not in all species. A single genotype only was found in sockeye and pink salmon in the Fraser River Basin, but was not detected in sockeye from the adjacent Columbia River Basin. All coho salmon, irrespective of river basin, were infected with a unique mix of 2 genotypes. These data indicated that the P. minibicornis population exhibited strong signals of structuring by both geography and salmonid host species. Particular genotypes may correlate with disease differences seen in salmon populations in the Pacific Northwest.

The recent implementation of mass drug administration (MDA) for control of uro-genital schistosomiasis has identified an urgent need for molecular markers to both directly monitor the impact of MDA, for example to distinguish re-infections from uncleared infections, as well as understand aspects of parasite reproduction and gene flow which might predict evolutionary change, such as the development and spread of drug resistance. We report the development of a novel microsatellite tool-kit allowing, for the first time, robust genetic analysis of individual S. haematobium larvae collected directly from infected human hosts. We genotyped the parasite populations of 47 children from 2 schools in the Ségou region of Mali, the first microsatellite study of this highly neglected parasite. There was only limited evidence of population subdivision between individual children or between the two schools, suggesting that few barriers to gene flow exist in this population. Complex relationships between parasite reproductive success, infection intensity and host age and gender were identified. Older children and boys harboured more diverse infections, as measured by the number of unique adult genotypes present. Individual parasite genotypes had variable reproductive success both across hosts, a pre-requisite for evolutionary selection, and, phenotypically, in hosts of different ages and genders. These data serve as a baseline against which to measure the effect of treatment on parasite population genetics in this region of Mali, and the tools developed are suitable to further investigate this important pathogen, and its close relatives, throughout their range.

The rTSSA-II (recombinant Trypomastigote Small Surface II) antigen was evaluated by ELISA to detect anti-Trypanosoma cruzi antibodies in sera from naturally infected dogs and humans. For this evaluation ELISA-rTSSA-II was standardized and groups were classified according to the results obtained through xenodiagnosis, ELISA and PCR. Sensitivity (Se), Specificity (Sp), Kappa index (KI) and area under curve (AUC) were determined. The Se was determined by using 14 sera from dogs infected with T. cruzi VI (TcVI) whereas Sp was determined by using 95 non-chagasic sera by xenodiagnosis, ELISA-Homogenate and PCR. The performance of ELISA-rTSSA-II in dog sera was high (AUC=0·93 and KI=0·91). The Se was 92·85% (1 false negative) and Sp was 100%. Two sera from dogs infected with TcI and 1 with TcIII were negative. For patients infected with T. cruzi, reactivity was 87·8% (36/41), there was only 1 indeterminate, and Sp was 100%. Fifty-four sera from non-chagasic and 68 sera from patients with cutaneous leishmaniasis did not react with rTSS-II. ELISA-rTSSA-II showed a high performance when studying sera from naturally infected dogs and it also presented 100% Sp. This assay could be an important tool to carry out sero-epidemiological surveys on the prevalence of T. cruzi circulating lineages in the region.

In order to investigate the dynamics of Septin4 (Sept4) expression and its function in the formation of fibrotic livers in mice infected with Schistosoma japonicum, we constructed the mouse model of S. japonicum egg-induced liver fibrosis for 24 weeks. Immunohistochemical staining, qRT-PCR and Western blot were used to detect the expression of Sept4 and α-smooth muscle actin (α-SMA). We found Sept4 localized in the perisinusoidal space where hepatic stellate cells (HSCs) distribute in the periphery of circumoval granulomas and the portal venule. The expression of Sept4 and α-SMA had a similar significant tendency of an up-regulation to a peak at 12 weeks post-infection (p.i.) followed by a down-regulation. At 24 weeks p.i. both were at a low level. These results suggest that Sept4 and α-SMA may interact together in HSCs. Based on this evidence, we hypothesize that Sept4 seems to be involved in the formation of inflammatory granulomata and subsequent liver fibrosis by regulating HSCs activation.

Virulence is part of the proximate base to the understanding of host–parasite interactions, and therefore it is crucial to interpret parasite-induced damage as an outcome of co-evolution between parasite and host. We experimentally investigated the impact of 2 congeneric ticks with contrasting transmission modes and host specificity, on the health of songbird nestlings (Parus major). The nidicolous Ixodes arboricola lives in tree holes where it obtains blood from adult birds and their nestlings, hence is prone to vertical transmission. All developmental stages of the field-dwelling Ixodes ricinus feed on different host taxa, hence are prone to horizontal transmission. Within each nest we infested 3 nestlings with varying loads of I. ricinus and 3 with Ixodes arboricola. Ixodes arboricola had no negative effects on nestling health (haematocrit, inflammation, body size, body condition). Body size was positively associated with the number of feeding I. arboricola adults. In contrast, I. ricinus infestations by nymphs and adult ticks led to haematocrit reductions. Furthermore, I. arboricola was a more prudent feeder, with longer feeding durations for smaller bloodmeals. Although the negative effects on nestling health were limited, our results are in line with current theories, stating that virulence increases with horizontal transmission, reduced dependence on individual hosts and reduced relatedness among co-exploiting ticks.

It is suspected that host-parasite interactions are influenced by climatic oscillations such as the North Atlantic Oscillation (NAO). However, the effects of climatic oscillations on host-parasite interactions have never been investigated. A long-term (1982–1999) dataset of the host snail Lymnaea stagnalis and trematode metacercariae infection has been collected for Lake Chany in Western Siberia. Using this dataset, we estimated the impact of the NAO on the population dynamics of hosts and parasites as well as their interactions. The results of general linear models showed that the abundance of dominant parasite species and the total parasite abundance significantly increased with NAO, with the exception of Moliniella anceps. Other climatic and biological factors were relatively weak to explain the abundance. There was no significant relationship between NAO and the population density of host snails. The prevalence of infection was related to the total abundance of parasites, but not to the NAO. Thus, the responses to the NAO differed between the host and parasites, indicating mismatching in host-parasite interactions. Therefore, climatic oscillations, such as the NAO, influence common parasitism.

Factors affecting survival of parasites introduced to new geographical regions include changes in environmental temperature. Protopolystoma xenopodis is a monogenean introduced with the amphibian Xenopus laevis from South Africa to Wales (probably in the 1960s) where low water temperatures impose major constraints on life-cycle processes. Effects were quantified by maintenance of eggs from infections in Wales under controlled conditions at 10, 12, 15, 18, 20 and 25°C. The threshold for egg viability/ development was 15°C. Mean times to hatching were 22 days at 25°C, 32 days at 20°C, extending to 66 days at 15°C. Field temperature records provided calibration of transmission schedules. Although egg production continues year-round, all eggs produced during >8 months/ year die without hatching. Output contributing significantly to transmission is restricted to 10 weeks (May–mid-July). Host infection, beginning after a time lag of 8 weeks for egg development, is also restricted to 10 weeks (July–September). Habitat temperatures (mean 15·5°C in summer 2008) allow only a narrow margin for life-cycle progress: even small temperature increases, predicted with ‘global warming’, enhance infection. This system provides empirical data on the metrics of transmission permitting long-term persistence of isolated parasite populations in limiting environments.

The monogenean Protopolystoma xenopodis has been established in Wales for >40 years following introduction with Xenopus laevis from South Africa. This provides an experimental system for determining constraints affecting introduced species in novel environments. Parasite development post-infection was followed at 15, 20 and 25°C for 15 weeks and at 10°C for ⩾1 year and correlated with temperatures recorded in Wales. Development was slowed/arrested at ⩽10°C which reflects habitat conditions for >6 months/year. There was wide variation in growth at constant temperature (body size differing by >10 times) potentially attributable in part to genotype-specific host-parasite interactions. Parasite density had no effect on size but host sex did: worms in males were 1·8 times larger than in females. Minimum time to patency was 51 days at 25°C and 73 days at 20°C although some infections were still not patent at both temperatures by 105 days p.i. In Wales, fastest developing infections may mature within one summer (about 12 weeks), possibly accelerated by movements of hosts into warmer surface waters. Otherwise, development slows/stops in October–April, delaying patency to about 1 year p.i., while wide variation in developmental rates may impose delays of 2 years in some primary infections and even longer in secondary infections.

Strongyloides ratti (Nagoya strain) is unique in that a portion of adults parasitizing the small intestine withstands ‘worm expulsion’, which starts at around day 8 post-infection (p.i.) by host immunity, and establishes in the large intestine after day 19 p.i. To investigate the mechanism, adults obtained from the small intestine at day 7 or 19 p.i. were transplanted into the colon of infection-primed immune rats. Adults obtained at day 7 p.i. were rejected quickly, whereas those obtained at day 19 p.i. could establish infection. Moreover, the body length and the number of intrauterine eggs increased in the large intestine. In a separate experiment, large intestinal parasitism was abolished by the treatment of host rats with an anti-oxidant, butylated hydroxyanisole. These results indicate that small intestinal adults between days 7 and 19 p.i. acquired the ability to parasitize the large intestine of immune rats, and that free radicals produced by the host may have played a significant role in the process.

Acanthochondria cornuta (Copepoda: Chondracanthidae) (N=4841; prevalence: 80·0%; mean±s.d. [range] intensity: 28·8±24·0 [1–110] parasites) infected the branchial chambers of the European flounder, Platichthys flesus (L.), (N=210) according to an established spatial pattern. This was independent of host size. Higher intensities resulted, most frequently, in higher numbers of infection sites, probably due to increased intraspecific competition. Preferential infection of the ocular side was supported by the recorded abundance data and reflected, probably, the fish's bottom-dwelling behaviour. As the parasite develops from one stage into another, it seems to migrate towards different sites: the copepodites and pre-adult females occurred, mainly, in the holobranchs; the adults preferred the internal wall (non-gravid/post-gravid females; adult males) or the pseudobranchs (gravid females). The ventilating water current along with the blood supply are suggested as 2 major factors in determining parasite spatial distribution within the chamber. Parasite crowding in a restricted and narrow space of the posterior region of the internal wall was recorded frequently and resembled that previously reported for the plaice. Differences to other host-parasite systems previously studied should relate with the anatomy of the respiratory apparatus. Bigamous females are reported for the first time.