Summer time predation on the obligatory off-host stage of an invasive ectoparasite

Context-dependent insect predation pressure on an avian ectoparasite

Context dependence arises when ecological relationships vary with the conditions under which they are observed. Context dependence of interactions involving parasites is poorly known, even if it is key to understanding host-parasite relationships and food web dynamics. This paper investigates to which extent predation pressure on an avian ectoparasite (Carnus hemapterus) is context-dependent. Based on a predator-exclusion experiment, predation pressure on C. hemapterus pupae in the host's nest for 3 years, and its variation between habitat types are quantified. Variation in precipitation and normalized difference vegetation index (NDVI) is also explored as a likely cause of context dependency. We hypothesize that predation pressure should fluctuate with such surrogates of food availability, so that inter-annual and intra-annual differences may emerge. The number of nests with significant reduction of pupae varied widely among years ranging from 24% to 75%. However, average pupae reduction in nests where a significant reduction occurred did not vary between years. No differences in predation rates between habitat types were detected. Precipitation and NDVI varied widely between years and NDVI was consistently lower around nests on cliffs than around nests on trees and farmhouses. Parallels were found between variation in predation pressure and precipitation/NDVI at a wide scale (highest predation the driest year, and much lower the 2 rainier ones), but not at the nest scale. This paper shows clear context-dependent insect predation pressure on an ectoparasite under natural conditions, and that such interaction changes in signs rather than magnitude between years. The causes for these variations require longer-term studies and/or well-designed, large-scale experiments.

Keds, the enigmatic flies and their role as vectors of pathogens

Hippoboscid flies (Diptera: Hippoboscidae), commonly known as keds or louse flies, have been for long time overlooked by the scientific community, and their vector role of infectious agents to humans and domestic animals has been scantly investigated. This is partly due to the fact that the host range for most species is primarily restricted to wildlife, being rarely reported on domestic animals and humans. This led to a scarce scientific knowledge about their biology, ecology, behaviour, epidemiology as well as vector competence. However, the life history of some hippoboscid species, e.g., Melophagus ovinus, Lipoptena cervi and Hippobosca equina, suggests that these ectoparasites are important candidates to vector infectious disease agents (e.g., Rickettsia spp., Borrelia spp., Bartonella spp., Anaplasma phagocytophilum, Theileria ovis). Indeed, the peculiar biological and behavioural traits (i.e., obligatory blood sucking and reproductive physiology) of many ked species make them a suitable pabulum for pathogen's multiplication and for their transmission to receptive hosts. Therefore, studies focusing on the ked bio-ecological aspects as well as on their vector role are advocated along with the control of keds affecting different animal species. This review discusses current information on keds, highlighting their importance as vectors of pathogens of medical and veterinary concern to all animal species, with a special focus on mammals.

Defining host range: host-parasite compatibility during the non-infective phase of the parasite also matters

Host range and parasite specificity determine key epidemiological, ecological and evolutionary aspects of host-parasite interactions. Parasites are usually classified as generalists or specialists based on the number of hosts they feed on. Yet, the requirements of the various stages of a parasite may influence the suitability of a given host species. Here, we investigate the generalist nature of three common ectoparasites (the dipteran Carnus hemapterus and two species of louse flies, Pseudolynchia canariensis and Ornithophila metallica), exploiting two avian host species (the European roller Coracias garrulus and the Rock pigeon Columba livia), that frequently occupy the same breeding sites. We explore the prevalence and abundance of both the infective and the puparial stages of the ectoparasites in both host species. Strong preferences of Pseudolynchia canariensis for pigeons and of Carnus hemapterus for rollers were found. Moderate prevalence of Ornithophila metallica was found in rollers but this louse fly avoided pigeons. In some cases, the infestation patterns observed for imagoes and puparia were consistent whereas in other cases host preferences inferred from imagoes differed from the ones suggested by puparia. We propose that the adult stages of these ectoparasites are more specialist than reported and that the requirements of non-infective stages can restrict the effective host range of some parasites.