Host condition and host immunity affect parasite fitness in a bird-ectoparasite system

1. Parasites might preferentially feed on hosts in good nutritional condition as such hosts provide better resources for the parasites' own growth, survival and reproduction. However, hosts in prime condition are also better able to develop costly immunological or physiological defence mechanisms, which in turn reduce the parasites' reproductive success. The interplay between host condition, host defence and parasite fitness will thus play an important part in the dynamics of host-parasite systems.;2. In a 2 x 2 design, we manipulated both the access to food in great tit Parus major broods and the exposure of the nestlings to hen fleas Ceratophyllus gallinae, a common ectoparasite of hole-breeding birds. We subsequently investigated the role of manipulated host condition, host immunocompetence, and experimentally induced host defence in nestlings on the reproductive success of individual hen flea females.;3. The food supplementation of the nestlings significantly influenced the parasites' reproductive success. Female fleas laid significantly more eggs when feeding on food-supplemented hosts.;4. Previous parasite exposure of the birds affected the reproductive success of fleas. However, the impact of this induced host response on flea reproduction depended on the birds' natural level of immunocompetence, assessed by the phytohaemagglutinin (PHA) skin test. Flea fecundity significantly decreased with increasing PHA response of the nestlings in previously parasite-exposed broods. No relationship between flea fitness and host immunocompetence was, however, found in previously unexposed broods. The PHA response thus correlates with the nestlings' ability to mount immunological or physiological defence mechanisms against hen fleas. No significant interaction effect between early flea exposure and food supplementation on the parasites' reproductive success was found.;5. Our study shows that the reproductive success of hen fleas is linked to the hosts' food supply early in life and their ability to mount induced immunological or physiological defence mechanisms. These interactions between host quality and parasite fitness are likely to influence host preference, host choice and parasite virulence and thus the evolutionary dynamics in host-parasite systems.

Social Work Education and Training in Europe and the Bologna Process

A short review of the last three decades shows that social work programmes have developed similarly in (almost) all European countries, both in terms of structural and content-related characteristics. Here I would like to focus on the following aspects: Increased academic focus of training, Generalist programme, International/European orientation. Increased academic focus means that social work programmes have been established at uni-versities or comparable higher education institutions, such as universities of applied sciences. The only exception is France where the approximately 150, generally fairly small colleges and the 14 larger instituts regionaux have a hybrid position between vocational colleges and universities and are roughly comparable to academies.

Social Work, Mobility and Membership

Social work is more involved in the collective life of its clientele than are other human service activities, because it is directly concerned with the bonds and conflicts between individuals, and the co-operative and competitive aspects of groups and communities. Hence it relies on being sited in organisations relevant to service users' lives, and on being able to influence these collectivities. This article argues that the 'organisational landscape' is being transformed, as commercial enterprises (more mobile and adaptable than either state or non-government organisations) take over important aspects of collective provision. The implications of this transformation for practice are analysed, by reference to examples from the United Kingdom in particular.