The Swine Health Information Center (SHIC) Swine Disease Fact Sheet Library continues to be updated. This process, part of SHIC’s mission to protect the health of the US swine herd, provides guidance and resources for producers, practitioners, and diagnosticians who are on the front lines of swine health concerns. Most recently, updated fact sheets on high path porcine reproductive and respiratory virus (HP-PRRSV) and Ebola virus were posted. While each fact sheet was thoroughly updated, taxonomy and epidemiology sections for both viruses saw the greatest change.
PRRS emerged in the US and Germany in the late 1980s, causing severe illness in pigs. Since then, PRRS has become an economically devastating disease and occurs in many parts of the world. Countries thought to be PRRS-free include Sweden, Norway, Finland, Switzerland, New Zealand, Australia, Argentina, Brazil, and Cuba.
HP-PRRS was first described in China in 2006 and circulates there yet with new variants continuing to appear. While to date Chinese HP-PRRSV variants have not been detected in the United States, there is ongoing concern about transboundary spread. The virus has spread to other countries in Asia, including Vietnam, Bhutan, Cambodia, Laos, Malaysia, Myanmar, the Philippines, Thailand, Singapore, and India.
Clinical presentation of HP-PRRS is variable but Infections with highly virulent strains are characterized by increased disease severity. In the 2006 Chinese outbreak, morbidity rates ranging from 50% to 100% were noted. An overall mortality rate of nearly 20% was observed, with up to 100% mortality in individual herds. Mortality rates were highest in suckling pigs (100%), followed by nursery pigs (70%), finishers (20%), and pregnant sows (10%).
In breeding animals, anorexia, fever, lethargy, depression, respiratory distress, and vomiting can be seen, as well as cyanosis of the ears, abdomen, and vulva. Transplacental transmission results in reproductive failure (stillborn, autolyzed, and/or mummified fetuses) or birth of viremic piglets. In young, growing, and finishing pigs, acute viremia is followed by respiratory disease including pneumonia, sneezing and expiratory dyspnea. Fever, lethargy, and depression can also be seen.
Additionally, neurological signs have been associated with HP-PRRSV, as well as an erythematous blanching rash. HP-PRRSV causes clinical disease and death in all ages, including adult pigs and pregnant sows.
There are six Ebola virus species, each known by species name (common name): Bombali Ebola virus (Bombali virus), Bundibugyo Ebola virus (Bundibugyo virus), Reston Ebola virus (Reston virus), Sudan Ebola virus (Sudan virus), Taï Forest Ebola virus (Taï Forest virus), and Zaire Ebola virus (Ebola virus). “Ebola virus” refers specifically to the species Zaire Ebola virus. Ebola viruses occur mainly in regions of Africa. Bats are thought to be the primary reservoir hosts. Reston virus is the only known Ebola virus that occurs in Asia.
Clinical illness due to Ebola virus has not been reported in pigs. However, serosurveys indicate pigs in some regions have been exposed to Ebola virus. The prevalence of Reston virus in pigs is unknown.
Natural infection with Ebola virus has not been described. Young pigs experimentally infected with Ebola virus develop non-specific respiratory disease. Clinical signs and lesions in pigs co-infected with Reston virus and PRRSV were consistent with severe, atypical PRRS (i.e., fever, respiratory distress, diarrhea, lameness, blue ears, petechiae, and elevated mortality).
In one experimental study, five-week-old pigs inoculated with Reston virus remained asymptomatic. However, more recently, it was shown that piglets aged three, five, or seven weeks developed respiratory distress following oronasal inoculation with Reston virus.
Reston virus is not known to cause disease in humans; however, concern about spillover events and changes in pathogenicity remain.
SHIC, launched in 2015 with Pork Checkoff funding, continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit http://www.swinehealth.org or contact Dr. Sundberg at [email protected].