Auerswald et al. JEV Seroprevalence in Domestic Birds serological evidence for WNV presence in Southeast Asia since decades. These findings mark the need for a re-definition of areas at risk for JEV and WNV transmission, and the need for further and intensified surveillance of mosquito-transmitted diseases in domestic animals.

Japanese encephalitis (JE) is the largest worldwide cause of infectious encephalitis in humans and is caused by a mosquito-borne flavivirus. JE transmission cycle involves Culex mosquitoes, pigs and aquatic birds as principal vertebrate amplifying hosts. JE infection is responsible for reproductive disorder in pigs when occurring after sexual maturity. In tropical areas, JE is endemic and the majority of pigs get infected before the age of 6 months. However, in subtropical areas, pigs may be infected after sexual maturity and thus experience clinical signs, inducing economic loss. The study aimed at better characterizing the influence of seasonal temperature variations (through estimates of degree days, DD) on JE circulation in pigs in subtropical area and inferring on the potential impact on JE symptomatic infection in reproductive pigs. Six hundred and forty-one pig's sera sampled in northern Vietnam were analysed for Japanese encephalitis virus (JEV) by pan-flavivirus ELISA. A subset of 108 ELISA-positive samples, representative of each sampling occasion, were confirmed by JEV neutralization test compared with West Nile virus neutralization test. We modelled the seroprevalence of pigs according to a DD variable using a generalized additive model. We then predicted the age of infection in pigs according to their month of birth, using averaged temperature data over 10 years. The model predicts that only 80 percentage of pigs born between July and September will be protected against JEV when reaching sexual maturity contrary to the rest of the year when almost all pigs will seroconvert before sexual maturity. In subtropical area such as northern Vietnam, pigs could thus show symptomatic infection due to JE, and consequently reproductive disorders. Vaccination of future breeder pigs in epidemic areas could avoid the occurrence of JE-associated reproductive disorders.

Introduction The objective of this study is to show the importance of interspecies links and temporal network dynamics of a multi-species livestock movement network. Although both cattle and sheep networks have been previously studied, cattle-sheep multi-species networks have not generally been studied in-depth. The central question of this study is how the combination of cattle and sheep movements affects the potential for disease spread on the combined network. Materials and methods Our analysis considers static and temporal representations of networks based on recorded animal movements. We computed network-based node importance measures of two single-species networks, and compared the top-ranked premises with the ones in the multi-species network. We propose the use of a measure based on contact chains calculated in a network weighted with transmission probabilities to assess the importance of premises in an outbreak. To ground our investigation in infectious disease epidemiology, we compared this suggested measure with the results of disease simulation models with asymmetric probabilities of transmission between species. Results Our analysis of the temporal networks shows that the premises which are likely to drive the epidemic in this multi-species network differ from the ones in both the cattle and the sheep networks. Although sheep movements are highly seasonal, the estimated size of an epidemic is significantly larger in the multi-species network than in the cattle network, independently of the period of the year. Finally, we demonstrate that a measure based on contact chains allow us to identify around 30% of the key farms in a simulated epidemic, ignoring markets, whilst static network measures identify less than 10% of these farms. Conclusion Our results ascertain the importance of combining species networks, as well as considering layers of temporal livestock movements in detail for the study of disease spread.