Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Public, Environmental & Occupational Health, Infectious Diseases, 1117 Public Health and Health Services, Tropical Medicine, 4202 Epidemiology

Abstract:

Plague remains a public health threat in many parts of the world, but particularly in sub-Saharan Africa. In general, it occurs seasonally and shows a clear geographically disjunct distribution in circumscribed foci. In spite of plague’s highly focal nature, the underlying ecology remains often unknown and Ecological Niche Modeling suggests that plague can occur in highly diverse landscapes under wide ranges of environmental conditions (Neerinckx et al. in press). In 1980 a persistent focus of human plague was discovered in Lushoto, northeastern Tanzania. By 2004 >7000 cases had been reported from this region and a strong variation in plague frequency and incidence is seen among neighboring villages in the plague endemic area (Davis et al. 2006). Earlier studies, which focused mainly on the host-vector-parasite system, demonstrated that this striking variation could not be explained by differences in fauna composition or human domestic behavior. Therefore, landscape ecological factors are suspected to determine plague’s local persistence and=or to act as disease-provoking factors. In the present study, we report on the link between human plague incidence in Lushoto and data on climate, landforms, land cover, soils and vegetation. We performed a comparative field survey in a number of plague-positive and -negative villages in Lushoto and gathered the collected information in a GIS database, including an elevation model, weather data time series (rainfall and temperature), landform and land cover descriptions, soil physical and chemical properties, and concentrations of chemical elements in the common plant Rumex usambarensis. We found a positive correlation between plague incidence and altitude, and the endemic plague area appeared to coincide with an area that had been totally deforested in the early 1960s. Moreover, POSTER ABSTRACTS: ECOLOGY OF PLAGUE 101 first observations suggest that villages with a high plague incidence are connected through typical fertile valley bottoms, i.e. Gleysols and Fluvisols, and that hamlets (part of a village) in this valley bottom have had more human plague cases. Soil and plant samples are being analyzed to test if factors that define the microclimate (in this study, bulk density, soil texture, pH, and organic carbon, and concentrations of chemical elements in soil and plant) are linked with plague occurrence in Lushoto. Our results give an indication that a landscape ecological study approach can provide insights into the persistence of plague and how its distribution can be affected by landscape features, and therefore in this case, might open the track towards a better understanding of the underlying ecology of plague’s distribution in Lushoto.