Mathematical and spatial epidemiology to rift valley fever and its association with climate in Sudan : Prospective study

Abstract

Rift valley fever (RVF) is transboundary zoonosis that impacts on health and trade. It caused by RNA virus that belongs to family Bunyviridae, genus Phlebovirus. It characterized by abortion in small ruminants following heavy rain falls. Also the virus is stable and survives in mosquito vector. Also, it is transmitted by contact with infected tissues and undercooked milk. RVF symptom is influenza like illness, in a severe cases bilateral blindness and encephalitis occurred. Its case fatality rate is very low (CFR=1%), however, it is reported to be as 50% in man. The objectives were to understand RVF epidemiology, analyze its climate and spatial patterns. The method used was to examine dependent and independent variables. The univariate analyses showed significant association between RVF and rain falls, vegetation cover, temperature and ElNino, respectively. The multivariate analyses found significant association between rain fall and vegetation index and RVF. This means rain fall and vegetation index were risk factors for RVF occurrence. Also, likelihood of transmission was calculated as 2.42 where infectiousness that an individual can infect another one. RVF basic reproduction number (R0) was estimated as 0.003. The study discussed RVF likelihood as (1.08%±2SD) decrease in RVF prevalence during year 2025; however no RVF outbreak is expected. The study concluded overall RVF prevalence was 34%. It recommended regression analyses is a very good to predict RVF, however vector ecology is essential. Therefore, this improves RVF management.