Avian malaria alters the dynamics of blood feeding in Culex pipiens mosquitoes.

Background: Some Plasmodium species have the ability to modify the behaviour of their mosquito vectors. This is thought to be an adaptive strategy that maximizes the parasite's transmission.

Methods: The effect of Plasmodium relictum infections on the blood feeding behaviour of Culex pipiens quinquefasciatus mosquitoes was monitored.

Early -induced inflammation does not accelerate aging in mice.

Aging is associated with a decline of performance leading to reduced reproductive output and survival. While the antagonistic pleiotropy theory of aging has attracted considerable attention, the molecular/physiological functions underlying the early-life benefits/late-life costs paradigm remain elusive. We tested the hypothesis that while early activation of the inflammatory response confers benefits in terms of protection against infection, it also incurs costs in terms of reduced reproductive output at old age and shortened longevity.

Eco-immunology and bioinvasion: revisiting the evolution of increased competitive ability hypotheses.

Immunity is at the core of major theories related to invasion biology. Among them, the evolution of increased competitive ability (EICA) and EICA-refined hypotheses have been used as a reference work. They postulate that the release from pathogens often experienced during invasion should favour a reallocation of resources from (costly) immune defences to beneficial life-history traits associated with invasive potential.

Avian malaria: a new lease of life for an old experimental model to study the evolutionary ecology of Plasmodium.

Avian malaria has historically played an important role as a model in the study of human malaria, being a stimulus for the development of medical parasitology. Avian malaria has recently come back to the research scene as a unique animal model to understand the ecology and evolution of the disease, both in the field and in the laboratory. Avian malaria is highly prevalent in birds and mosquitoes around the world and is amenable to laboratory experimentation at each stage of the parasite's life cycle.

Host immune responses to experimental infection of Plasmodium relictum (lineage SGS1) in domestic canaries (Serinus canaria).

Understanding the complexity of host immune responses to parasite infection requires controlled experiments that can inform observational field studies. Birds and their malaria parasites provide a useful model for understanding host-parasite relationships, but this model lacks a well-described experimental context for how hosts respond immunologically to infection. Here, ten canaries (Serinus canaria) were infected with the avian malaria parasite Plasmodium relictum (lineage SGS1) in a controlled laboratory setting with ten uninfected (control) birds.

Evolution of plastic transmission strategies in avian malaria.

Malaria parasites have been shown to adjust their life history traits to changing environmental conditions. Parasite relapses and recrudescences--marked increases in blood parasite numbers following a period when the parasite was either absent or present at very low levels in the blood, respectively--are expected to be part of such adaptive plastic strategies. Here, we first present a theoretical model that analyses the evolution of transmission strategies in fluctuating seasonal environments and we show that relapses may be adaptive if they are concomitant with the presence of mosquitoes in the vicinity of the host.

Patterns of phenoloxidase activity in insecticide resistant and susceptible mosquitoes differ between laboratory-selected and wild-caught individuals.

Background: Insecticide resistance has the potential to alter vector immune competence and consequently affect the transmission of diseases.

Methods: Using both laboratory isogenic strains and field-caught Culex pipiens mosquitoes, we investigated the effects of insecticide resistance on an important component of the mosquito immune system: the phenoloxidase (PO) activity. As infection risk varies dramatically with the age and sex of mosquitoes, allocation to PO immunity was quantified across different stages of the mosquito life cycle.

Food availability and competition do not modulate the costs of Plasmodium infection in dominant male canaries.

Understanding the different factors that may influence parasite virulence is of fundamental interest to ecologists and evolutionary biologists. It has recently been demonstrated that parasite virulence may occur partly through manipulation of host competitive ability. Differences in competitive ability associated with the social status (dominant or subordinate) of a host may determine the extent of this competition-mediated parasite virulence.

Impact of host nutritional status on infection dynamics and parasite virulence in a bird-malaria system.

Host resources can drive the optimal parasite exploitation strategy by offering a good or a poor environment to pathogens. Hosts living in resource-rich habitats might offer a favourable environment to developing parasites because they provide a wealth of resources. However, hosts living in resource-rich habitats might afford a higher investment into costly immune defences providing an effective barrier against infection.

Both infected and uninfected mosquitoes are attracted toward malaria infected birds.

Background: The biting behaviour of mosquitoes is crucial for the transmission of malaria parasites. This study focuses on the feeding behaviour of Culex pipiens mosquitoes with regard to the infection status by the avian malaria parasite Plasmodium relictum (lineage SGS1).

Methods: Uninfected and sporozoite-infected mosquitoes were provided with a choice between an uninfected bird and a bird undergoing a chronic P.

Immunity and the emergence of virulent pathogens.

The emergence/re-emergence of infectious diseases has been one of the major concerns for human and wildlife health. In spite of the medical and veterinary progresses as to prevent and cure infectious diseases, during the last decades we have witnessed the emergence/re-emergence of virulent pathogens that pose a threat to humans and wildlife. Many factors that might drive the emergence of these novel pathogens have been identified and several reviews have been published on this topic in the last years.

Immune evasion, immunopathology and the regulation of the immune system.

Costs and benefits of the immune response have attracted considerable attention in the last years among evolutionary biologists. Given the cost of parasitism, natural selection should favor individuals with the most effective immune defenses. Nevertheless, there exists huge variation in the expression of immune effectors among individuals.

Malaria infection increases bird attractiveness to uninfected mosquitoes.

The epidemiology of vector-borne pathogens is largely determined by the host-choice behaviour of their vectors. Here, we investigate whether a Plasmodium infection renders the host more attractive to host-seeking mosquitoes. For this purpose, we work on a novel experimental system: the avian malaria parasite Plasmodium relictum, and its natural vector, the mosquito Culex pipiens.

Experimental inhibition of nitric oxide increases Plasmodium relictum (lineage SGS1) parasitaemia.

Malaria is a widespread vector-borne disease infecting a wide range of terrestrial vertebrates including reptiles, birds and mammals. In addition to being one of the most deadly infectious diseases for humans, malaria is a threat to wildlife. The host immune system represents the main defence against malaria parasites.

Density-dependent effects on parasite growth and parasite-induced host immunodepression in the larval helminth Pomphorhynchus laevis.

Larval helminths exploit the physiology of their intermediate hosts: first, as a resource for energy and space and second by altering the immune system activity to ensure their survival. Whereas the growth pattern under parasite competition has been investigated, the effect of multiple infections on the level of parasite-induced immunodepression in a trophically transmitted helminth has been neglected. In this study, amphipods Gammarus pulex were infected in the laboratory by the acanthocephalan Pomphorhynchus laevis to investigate how parasite density in the intermediate host affected (i) cystacanth growth and (ii) the level of parasite-induced alterations of the host immune defences, two traits strongly linked to host exploitation.

Variation between populations and local adaptation in acanthocephalan-induced parasite manipulation.

Many trophically transmitted parasites manipulate their intermediate host phenotype, resulting in higher transmission to the final host. However, it is not known if manipulation is a fixed adaptation of the parasite or a dynamic process upon which selection still acts. In particular, local adaptation has never been tested in manipulating parasites.

Patterns of aging in the long-lived wandering albatross.

How does an animal age in natural conditions? Given the multifaceted nature of senescence, identifying the effects of age on physiology and behavior remains challenging. We investigated the effects of age on a broad array of phenotypic traits in a wild, long-lived animal, the wandering albatross. We studied foraging behavior using satellite tracking and activity loggers in males and females (age 6-48+ years), and monitored reproductive performance and nine markers of baseline physiology known to reflect senescence in vertebrates (humoral immunity, oxidative stress, antioxidant defenses, and hormone levels).

Parasite virulence when the infection reduces the host immune response.

Parasite infections often induce a reduction in host immune response either because of a direct manipulation of the immune system by the parasite or because of energy depletion. Although infection-induced immunodepression can favour the establishment of the parasite within the host, a too severe immunodepression may increase the risk of infection with opportunistic pathogens, stopping the period over which the parasite can be transmitted to other hosts. Here, we explore how the risk of contracting opportunistic diseases affects the survival of the amphipod Gammarus pulex infected by the acanthocephalan Pomphorhynchus laevis.

Variation and covariation in infectivity, virulence and immunodepression in the host-parasite association Gammarus pulex-Pomphorhynchus laevis.

Parasites often manipulate host immunity for their own benefit, either by exacerbating or suppressing the immune response and this may directly affect the expression of parasite virulence. However, genetic variation in immunodepression, which is a prerequisite to its evolution, and the relationship between immunodepression and virulence, have rarely been studied. Here, we investigated the variation among sibships of the acanthocephalan parasite, Pomphorhynchus laevis, in infecting and in immunodepressing its amphipod host, Gammarus pulex.

Variation in immune defence among populations of Gammarus pulex (Crustacea: Amphipoda).

Despite intensive studies in ecological immunology, few have investigated variation in immune defence among natural populations; in particular, there is a lack of knowledge of the sources of spatial variability in immune defence in the wild. Here we documented variation among twelve populations of the freshwater crustacean Gammarus pulex in the activity of the prophenoloxidase (ProPO) system, which is an important component of invertebrate immunity. We then tested for trade-offs between investment in immune defence and fitness-related traits such as survival and fecundity, as well as for environmental causes of variability (water temperature and conductivity, parasite prevalence).

Immune depression induced by acanthocephalan parasites in their intermediate crustacean host: consequences for the risk of super-infection and links with host behavioural manipulation.

Parasite survival in hosts mainly depends on the capacity to circumvent the host immune response. Acanthocephalan infections in gammarids are linked with decreased activity of the prophenoloxidase (ProPO) system, suggesting an active immunosuppression process. Nevertheless, experimental evidence for this hypothesis is lacking: whether these parasites affect several immune pathways is unknown and the consequences of such immune change have not been investigated.

Is there a role for antioxidant carotenoids in limiting self-harming immune response in invertebrates?

Innate immunity relies on effectors, which produce cytotoxic molecules that have not only the advantage of killing pathogens but also the disadvantage of harming host tissues and organs. Although the role of dietary antioxidants in invertebrate immunity is still unknown, it has been shown in vertebrates that carotenoids scavenge cytotoxic radicals generated during the immune response. Carotenoids may consequently decrease the self-harming cost of immunity.