Browsing by Author "Pfeiffer, Dirk U."

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A spatial analysis of Rift Valley Fever Virus seropositivity in domestic ruminants in Tanzania
(PLOS ONE, 2015-07-10) Sindato, Calvin; Pfeiffer, Dirk U.; Karimuribo, Esron D.; Mboera, Leonard E.G.; Rweyemamu, Mark M.; Paweska, Janusz T.
Rift Valley fever(RVF) is an acute arthropod-borne viral zoonotic disease primarily occurring in Africa.Since RVF-like disease was reported in Tanzaniain1930,outbreaks of the disease have been reported mainly from the eastern ecosystem of the Great Rift Valley. This cross-sectional study was carried out to describe the variation in RVF virus (RVFV) seropositivity in domestic ruminants between selected villages in the eastern and western Rift Valley ecosystems in Tanzania, and identify potential risk factors. Three study villages were purposively selected from each of the two Rift Valley ecosystems. Serum samples from randomly selected domestic ruminants (n=1,435) were tested for the presence of specific immunoglobulin G(IgG) and M(IgM) ,using RVF enzyme-linked immunosorbent assay methods .Mixed effects logistic regression modelling was used to investigate the association between potential risk factors and RVFV seropositivity. The overall RVFV seroprevalence (n=1,435) in domestic ruminants was 25.8% and species specific seroprevalence was 29.7%, 27.7% and 22.0% in sheep (n=148), cattle (n=756) and goats (n=531), respectively. The odds of seropositivity were significantly higher in animals sampled from the villages in the eastern than those in the western Rift Valley ecosystem (OR=1.88,CI: 1.41,2.51; p<0.001) , in animals sampled from villages with soils of good than those with soils of poor water holding capacity (OR=1.97; 95%CI:1.58,3.02;p<0.001), and in animals which had been introduced than in animals born within the herd (OR=5.08,CI:2.74, 9.44;p<0.001). Compared with animals aged 1–2 years, those aged 3 and 4–5 years had 3.40 (CI:2.49,4.64;p<0.001) and 3.31 (CI:2.27,4.82,p<0.001) times the odds of seropositivity. The findings confirm exposure to RVFV in all the study villages, but with a higher prevalence in the study villages from the eastern Rift Valley ecosystem.
Spatial and temporal pattern of Rift Valley fever outbreaks in Tanzania; 1930 to 2007
(Plos One, 2014) Sindato, Calvin; Karimuribo, Esron D.; Pfeiffer, Dirk U.
Background: Rift Valley fever (RVF)-like disease was first reported in Tanzania more than eight decades ago and the last large outbreak of the disease occurred in 2006–07. This study investigates the spatial and temporal pattern of RVF outbreaks in Tanzania over the past 80 years in order to guide prevention and control strategies. Materials and Methods: A retrospective study was carried out based on disease reporting data from Tanzania at district or village level. The data were sourced from the Ministries responsible for livestock and human health, Tanzania Meteorological Agency and research institutions involved in RVF surveillance and diagnosis. The spatial distribution of outbreaks was mapped using ArcGIS 10. The space-time permutation model was applied to identify clusters of cases, and a multivariable logistic regression model was used to identify risk factors associated with the occurrence of outbreaks in the district. Principal Findings: RVF outbreaks were reported between December and June in 1930, 1947, 1957, 1960, 1963, 1968, 1977– 79, 1989, 1997–98 and 2006–07 in 39.2% of the districts in Tanzania. There was statistically significant spatio-temporal clustering of outbreaks. RVF occurrence was associated with the eastern Rift Valley ecosystem (OR = 6.14, CI: 1.96, 19.28), total amount of rainfall of .405.4 mm (OR = 12.36, CI: 3.06, 49.88), soil texture (clay [OR = 8.76, CI: 2.52, 30.50], and loam [OR = 8.79, CI: 2.04, 37.82]). Conclusion/Significance: RVF outbreaks were found to be distributed heterogeneously and transmission dynamics appeared to vary between areas. The sequence of outbreak waves, continuously cover more parts of the country. Whenever infection has been introduced into an area, it is likely to be involved in future outbreaks. The cases were more likely to be reported from the eastern Rift Valley than from the western Rift Valley ecosystem and from areas with clay and loam rather than sandy soil texture.