Why U.S. Pork Producers Need to Pay Attention to Australia Right Now
The U.S. has the necessary components for Japanese encephalitis virus (JEV) transmission – competent insect vectors and susceptible vertebrate maintenance and amplifying hosts, said Leela Noronha of the Foreign Arthropod-Borne Animal Disease Research Unit at USDA’s National Bio and Agro-Defense Facility, in Manhattan, Kan.
Concern over this deadly virus is based in part on the precedent set by West Nile virus which grew exponentially since being introduced in 1999, the Swine Health Information Center (SHIC) reports.
Insect vectors of JEV are numerous though it is primarily transmitted by Culex spp. mosquitoes. In experimental conditions, a few North American Culex species and others have been shown to be competent insect vectors. Avian hosts of JEV can serve as mobile virus reservoirs which are typically asymptomatic, Noronha said during a webinar hosted by SHIC. Wild and domestic North American species have demonstrated susceptibility experimentally.
JEV-affected swine play an important role in virus amplification. Wild pigs are wildcards that can impact transmission given they represent a rapidly expanding, free-range population of vertebrate hosts.
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If the disease hasn’t been reported yet in the U.S., why all the fuss?
During the webinar, Natalia Cernicchiaro of Kansas State University, shared information on the risk of introduction of JEV in the continental U.S.
She used maps to illustrate the global expansion of JEV from Asia to northern Europe to Africa where competent vectors and hosts exist. This region is susceptible to JEV because the U.S. shares similar climate and environmental conditions with countries where JEV is epidemic and has competent vectors and hosts. Also, there is increased travel and trade from and to JEV-affected regions since World War II. This combined with the fact that there is no active surveillance in U.S. for JEV at this time is notable.
Cernicchiaro and a team of experts conducted a qualitative and quantitative risk assessment addressing the likelihood of JEV reaching the US. This risk assessment addressed:
- probability of entry
- probability of transmission
- probability of establishment
- extent of spread
- likelihood of persistence
- impact of disease
Aircraft and cargo ships emerged as the most likely pathways of introduction for JEV via infected adult mosquitoes in the study, she said. The probability of introduction of JEV through infected adult mosquitoes via aircrafts was deemed very high whereas the probability of entry via ships/containers was considered of low to moderate risk.
“Although the probability of transmission was deemed of variable risk, from low to high, depending on the U.S. area of introduction and the season, under current conditions, the probability of JEV establishment in the U.S. is considered negligible because of the low availability of amplifying hosts (pigs) and the limited contact rates between infected mosquitoes and hosts in airports and seaports, areas at high risk of introduction of infected vectors,” SHIC reports.
Given the study findings, prevention and control should be directed towards the aircraft pathway and include aircraft disinfection in the countries of origin, or when arriving at the destination.
Cernicchiaro also said the study results point to the need for active surveillance programs on the east and west coasts of the U.S.
More from Farm Journal's PORK:
Mosquito-Borne Virus "Is a Nightmare" For Australian Pig Farmers
Mosquito-Borne Virus Discovered on Australian Pig Farms
SHIC Adds to Preparedness With Updated PTV and JEV Fact Sheets
Japanese Encephalitis Virus Could Happen in U.S. Swine Herds
