Browsing by Author "Leirs, H"
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Item Arenavirus infection correlates with lower survival of its natural rodent host in a long-term capture-mark-recapture study(2018) Mariën, J.; Sluydts, V.; Borremans, B.; Gryseels, S.; Broecke, B. V.; Sabuni, C. A.; Katakweba, A. A. S.; Mulungu, L. S.; Günther, S.; de Bellocq, J. G.; Massawe, A. W.; Leirs, HBackground: Parasite evolution is hypothesized to select for levels of parasite virulence that maximise transmission success. When host population densities fluctuate, low levels of virulence with limited impact on the host are expected, as this should increase the likelihood of surviving periods of low host density. We examined the effects of Morogoro arenavirus on the survival and recapture probability of multimammate mice (Mastomys natalensis) using a seven-year capture-mark-recapture time series. Mastomys natalensis is the natural host of Morogoro virus and is known for its strong seasonal density fluctuations. Results: Antibody presence was negatively correlated with survival probability (effect size: 5–8% per month depending on season) but positively with recapture probability (effect size: 8%). Conclusions: The small negative correlation between host survival probability and antibody presence suggests that either the virus has a negative effect on host condition, or that hosts with lower survival probability are more likely to obtain Morogoro virus infection, for example due to particular behavioural or immunological traits. The latter hypothesis is supported by the positive correlation between antibody status and recapture probability which suggests that risky behaviour might increase the probability of becoming infected.Item Demographic and spatio-temporal variation in human plague at a persistent focus in Tanzania(Elsevier, 2006-10) Makundi, R.H; Davis, S; Machan"gu, R.S; Leirs, HHuman plague in the Western Usambara Mountains in Tanzania has been a public health problem since the first outbreak in 1980. The wildlife reservoir is unknown and eradication measures that have proved effective elsewhere in Tanzania appear to fail in this region. We use census data from 2002 and hospital records kept since 1986 to describe the temporal, spatial and demographic variation in human plague. A seasonal peak in cases occurs from December to February with the numbers of cases during this peak varying between 0 and 1150. Variation in incidence, calculated for each village as the mean number of cases per thousand inhabitants per year, indicates that human plague is concentrated around a group of three neighbouring, relatively isolated, high-altitude villages; Nywelo, Madala and Gologolo. However, there was no evidence that these villages were acting as a source of infection for the remainder of the focus. The likelihood of becoming infected with plague is highest between the ages of 5 and 19 and lowest for adult men. This was most clear in the ward encompassing the three high-incidence villages where the risk of plague among children aged 10–14 was 2.2 times higher than for adults aged 30–34, and among adults aged 30–34, the risk was 2.4 times higher for women than men.Item Do farming practices influence population dynamics of rodents? A case study of the multimammate field rats, Mastomys natalensis, in Tanzania(Blackwell Publishing Ltd, Afr. J. Ecol., 2006) Massawe, A. W.; Rwamugira, W; Leirs, H; Makundi, Rhodes H.; Mulungu, Loth S.A capture-mark-recapture study was conducted in crop fields in Morogoro, Tanzania, to investigate how the population dynamics of multimammate field rats, Mastomys natalensis, was influenced by the commonly practised land preparation methods and cropping systems. Two land preparation methods (tractor ploughing and slash and burn) and two cropping systems (mono-cropping with maize and inter-cropping with maize and beans) were investigated in a Complete Randomized Design experiment with 2 · 2 factors, and two 0.5 ha replicates per treatment. Mastomys natalensis comprised 97.8% of the abundance of the three rodent species captured in the study area. The slash and burned fields had higher rodent population densities than tractor ploughed fields (P < 0.05). Recruitment rates were higher in the slash and burn fields than in the tractor ploughed fields, suggesting that the former were more favourable habitats for M. natalensis. Land preparation methods appeared to influence the population dynamics of M. natalensis through recruitment of new individuals in the population and most probably survival. Apart from the temporal changes in population density, which were reflected in both tractor ploughed and slash and burn fields, cropping systems (mono- and inter-crop) had little effect on the population dynamics of M. natalensis [F(1,8) ¼ 6.50; P > 0.05]. The study shows that land preparation methods should be considered a component of rodent pest management in ecologically based or integrated management practices. In maize fields in Tanzania, the crop is most susceptible to damage by M. natalensis in the first 2 weeks after planting, and therefore, lower densities of rodents will result into lower crop damage in tractor ploughed fields.Item Human activity spaces and plague risks in three contrasting landscapes in Lushoto District, Tanzania(Tanzania Journal of Health Research, 2014-07-14) Hieronimo, P.; Gulinck, H; Kimaro, D.N; Mulungu, L.S; Kihupi, N.I; Msanya, B.M; Leirs, H; Deckers, J.ASince 1980 plague has been a human threat in the Western Usambara Mountains in Tanzania. However, the spatial-temporal pattern of plague occurrence remains poorly understood. The main objective of this study was to gain understanding of human activity patterns in relation to spatial distribution of fleas in Lushoto District. Data were collected in three landscapes differing in plague incidence. Field survey coupled with Geographic Information System (GIS) and physical sample collections were used to collect data in wet (April to June 2012) and dry (August to October 2012) seasons. Data analysis was done using GIS, one-way ANOVA and nonparametric statistical tools. The degree of spatial cooccurrence of potential disease vectors (fleas) and humans in Lushoto focus differs significantly (p ≤ 0.05) among the selected landscapes, and in both seasons. This trend gives a coarse indication of the possible association of the plague outbreaks and the human frequencies of contacting environments with fleas. The study suggests that plague surveillance and control programmes at landscape scale should consider the existence of plague vector contagion risk gradient from high to low incidence landscapes due to human presence and intensity of activities.