Dose-dependent effects of experimental infection with the virulent Neospora caninum Nc-Spain7 isolate in a pregnant mouse model.

Pregnant BALB/c mice have been widely used as an in vivo model to study Neospora caninum infection biology and to provide proof-of-concept for assessments of drugs and vaccines against neosporosis. The fact that this model has been used with different isolates of variable virulence, varying infection routes and differing methods to prepare the parasites for infection, has rendered the comparison of results from different laboratories impossible. In most studies, mice were infected with similar number of parasites (2 × 10(6)) as employed in ruminant models (10(7) for cows and 10(6) for sheep), which seems inappropriate considering the enormous differences in the weight of these species. Thus, for achieving meaningful results in vaccination and drug efficacy experiments, a refinement and standardization of this experimental model is necessary. Thus, 2 × 10(6), 10(5), 10(4), 10(3) and 10(2) tachyzoites of the highly virulent and well-characterised Nc-Spain7 isolate were subcutaneously inoculated into mice at day 7 of pregnancy, and clinical outcome, vertical transmission, parasite burden and antibody responses were compared. Dams from all infected groups presented nervous signs and the percentage of surviving pups at day 30 postpartum was surprisingly low (24%) in mice infected with only 10(2) tachyzoites. Importantly, infection with 10(5) tachyzoites resulted in antibody levels, cerebral parasite burden in dams and 100% mortality rate in pups, which was identical to infection with 2 × 10(6) tachyzoites. Considering these results, it is reasonable to lower the challenge dose to 10(5) tachyzoites in further experiments when assessing drugs or vaccine candidates.

A focused ethnographic study of community social capital

Social capital, a relatively new public health concept, represents the intangible resources embedded in social relationships that facilitate collective action. Current interest in the concept stems from empirical studies linking social capital with health outcomes. However, in order for social capital to function as a meaningful research variable, conceptual development aimed at refining the domains, attributes, and boundaries of the concept are needed. An existing framework of social capital (Uphoff, 2000), developed from studies in India, was selected for congruence with the inductive analysis of pilot data from a community that was unsuccessful at mobilizing collective action. This framework provided the underpinnings for a formal ethnographic research study designed to examine the components of social capital in a community that had successfully mobilized collective action. The specific aim of the ethnographic study was to examine the fittingness of Uphoff's framework in the contrasting American community. A contrasting context was purposefully selected to distinguish essential attributes of social capital from those that were specific to one community. Ethnographic data collection methods included participant observation, formal interviews, and public documents. Data was originally analyzed according to codes developed from Uphoff's theoretical framework. The results from this analysis were only partially satisfactory, indicating that the theoretical framework required refinement. The refinement of the coding system resulted in the emergence of an explanatory theory of social capital that was tested with the data collected from formal fieldwork. Although Uphoff's framework was useful, the refinement of the framework revealed, (1) trust as the dominant attribute of social capital, (2) efficacy of mutually beneficial collective action as the outcome indicator, (3) cognitive and structural domains more appropriately defined as the cultural norms of the community and group, and (4) a definition of social capital as the combination of the cognitive norms of the community and the structural norms of the group that are either constructive or destructive to the development of trust and the efficacy of mutually beneficial collective action. This explanatory framework holds increased pragmatic utility for public health practice and research. ^