Epidemiological analysis of bovine ephemeral fever in 2012–2013 in the subtropical islands of Japan

Abstract

BackgroundBovine ephemeral fever (BEF) is a febrile disease of cattle that is transmitted by arthropod vectors such as mosquitoes and Culicoides biting midges. An outbreak of BEF recently occurred in Ishigaki Island and surrounding islands that are located southwest of Japan. In this study, an epidemiological analysis was conducted to understand the temporal and spatial characteristics of the outbreak. Factors associated with the disease spread within Ishigaki Island were investigated by hierarchical Bayesian models. The possibility of between-island transmission by windborne vectors and transmission by long-distance migration of infected vectors were examined using atmospheric dispersion models.ResultsIn September 2012, the first case of the disease was detected in the western part of Ishigaki Island. In 1 month, it had rapidly spread to the southern part of the island and to surrounding islands, and led to 225 suspected cases of BEF during the outbreak. The dispersion model demonstrated the high possibility of between-island transmission by wind. Spatial analysis showed that paddy fields, farmlands, and slope gradients had a significant impact on the 1-km cell-level incidence risk. These factors may have influenced the habitats and movements of the vectors with regard to the spread of BEF. A plausible incursion event of infected vectors from Southeast Asia to Ishigaki Island was estimated to have occurred at the end of August.ConclusionThis study revealed that the condition of a terrain and land use significantly influenced disease transmission. These factors are important in assessing favorable environments for related vectors. The results of the dispersion model indicated the likely transmission of the infected vectors by wind on the local scale and on the long-distance scale. These findings would be helpful for developing a surveillance program and developing preventive measures against BEF.

Monitoring Taiwanese bovine arboviruses and non‐arboviruses using a vector‐based approach

“…Some reassortment between AINOV and PEAV may occur in nature (Yanase et al ., ), although this phenomenon has not yet been observed by cloning their structure genes (data not shown). In 2012–2013, BEFV broke out in both the Yaeyama Islands, Japan, and Taiwan; BEFV may have been transferred from the Yaeyama Islands to eastern Taiwan through an airstream (Ting et al ., ; Hayama et al ., ). The initial outbreak of BEFV occurred in September 2012 in eastern Taiwan, but the virus soon spread to western Taiwan via Pingtung County; this temporospatial pattern of occurrence is in line with predictions made by airstream simulation (Hayama et al ., ).…”

“…In 2012–2013, BEFV broke out in both the Yaeyama Islands, Japan, and Taiwan; BEFV may have been transferred from the Yaeyama Islands to eastern Taiwan through an airstream (Ting et al ., ; Hayama et al ., ). The initial outbreak of BEFV occurred in September 2012 in eastern Taiwan, but the virus soon spread to western Taiwan via Pingtung County; this temporospatial pattern of occurrence is in line with predictions made by airstream simulation (Hayama et al ., ). Another viewpoint indicated that BEFV may spread in a seasonal direction from southern China to southwestern Taiwan (Walker & Klement, ).…”

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

“…Large-and medium-scale outbreaks of BEF repeatedly occurred in Japan until 1989 (18,19). Since then, the epidemics had been limited to the southwestern islands of Japan, which are close to Taiwan (20,21). However, in 2015 a reoccurrence of BEF was reported in the southern end of Kyushu, which is one of the main islands of Japan (22).…”

“…As a pioneering study, a backward-trajectory analysis of the BEF epidemic in 2012 in Japan's southwestern islands showed that the estimated potential sources of infected vectors were Southeast Asian countries such as Vietnam and Philippine (21).…”

MiR-3470b promotes bovine ephemeral fever virus replication via directly targeting mitochondrial antiviral signaling protein (MAVS) in baby hamster Syrian kidney cells

“…It can spread rapidly and lead to considerable economic losses due to decreased-milk production, reduced-male fertility, disruption of stock movement, and even causes death of infected animals [1, 2]. In addition, BEF is believed to be an ancient disease that has been endemic in tropical, subtropical, and temperate regions of Africa, Asia, and Australia [3–5]. Its causative agent, bovine ephemeral fever virus (BEFV) is an enveloped, nonsegmented, single stranded negative sense RNA virus in the Ephemerovirus genus of the Rhabdoviridae family.…”