Gouleako and Herbert viruses in pigs, Republic of Korea, 2013.

Several viruses in the family Bunyaviridae are pathogenic to animals and cause vector-borne zoonoses. In 2013, investigation of cause of death of 9 pigs on 1 farm in the Republic of Korea found infection with Gouleako and Herbert viruses. Subsequent investigation revealed high prevalence of these viruses among pigs throughout the country.

Evidence of infectivity of airborne porcine epidemic diarrhea virus and detection of airborne viral RNA at long distances from infected herds.

Porcine epidemic diarrhea virus (PEDV) spread rapidly after being diagnosed in the USA in April 2013. In this study we assessed whether PEDV could become airborne and if so, whether the virus was infectious. Air samples were collected both from a room containing experimentally infected pigs and at various distances from the outside of swine farms experiencing acute PEDV outbreaks. Results indicated presence of infectious PEDV in the air from experimentally infected pigs and genetic material of PEDV was detected up to 10 miles downwind from naturally infected farms. Airborne transmission should be considered as a potential route for PEDV dissemination.

Corrigendum: Monitoring the Spread of Swine Enteric Coronavirus Diseases in the United States in the Absence of a Regulatory Framework.

[This corrects the article DOI: 10.3389/fvets.2016.00018.].

Production impact & time to stability in sow herds infected with porcine epidemic diarrhea virus (PEDV).

PEDV was first detected in United States in May, 2013. The virus spread through the swine industry and was reported in 30 US states by June, 2014 (Morrison and Goede, 2014). There are limited data describing the impact on production in sow farms. Veterinarians attempt to control the virus in sow herds with a program that stimulates herd immunity. There are no data on how long it takes with this control program to achieve a stable state of consistently produce weaned pigs that are not infected with the virus. This study involved participants and data from an existing program called the Swine Health Monitoring Project. Veterinarians were invited to share production data from 429 herds infected with PEDV. These data, in conjunction with diagnostic reports, were used to estimate the time required for the herd to produce PEDV PCR negative pigs and the production loss. Of the 429 infected herds that achieved the stable state of weaning PEDV PCR negative pigs, the median time was 28 weeks, ranging from 7 to 64 weeks. A median of 2.7 piglets/inventoried sow were not weaned and the average time required to recover to baseline production was 10 weeks in 183 herds. Herd infected in quarters 3 or 4 of the year had approximately twice the negative impact. These data are valuable for veterinarians in advising clients on the anticipated impact and time to re-achieve a stable state with regards to PEDV.

Spatial and temporal epidemiology of porcine epidemic diarrhea (PED) in the Midwest and Southeast regions of the United States.

Emergence of porcine epidemic diarrhea virus (PEDV) in the US in 2013 caused a major impact in the swine industry due to its high mortality and rapid spread through the country. Even though the role of potential sources of infection in the epidemiology of the disease at the farm level (feed, fomites) has been extensively investigated, there is a lack of knowledge about the dynamics of disease spread at the regional level. Here, we investigated the dissemination of PEDV infection in two areas located in the regions with the highest swine density in the country (Southeast and Midwest) including more than 2400 farms. Location and date of outbreaks were used to assess the spatial and temporal clustering of cases using global (Cuzick-Edwards, Knox and directional tests) and local (Bernouilli model of the spatial scan statistic) techniques in the first 10 months of the epidemic. A strong spatio-temporal pattern was detected in both areas of study, with an increased risk of disease at <2km distances of recently (<7 days) infected farms, although extent of clustering was higher in the Southeast. Results, computed for two different locations in the first months of the epidemic, suggest that local transmission from infected farms into neighboring PEDV-free sites is a likely explanation for a substantial proportion of the reported PEDV-positive farms and consistent with the rapid spread of a highly infectious disease in the absence of immunity.

Monitoring the Spread of Swine Enteric Coronavirus Diseases in the United States in the Absence of a Regulatory Framework.

The reporting and monitoring of swine enteric coronavirus diseases (SECD), including porcine epidemic diarrhea virus and porcine delta coronavirus, in the United States have been challenging because of the initial absence of a regulatory framework and the emerging nature of these diseases. The National Animal Health Laboratory Network, the Emergency Management and Response System, and the Swine Health Monitoring Project were used to monitor the disease situation between May 2013 and March 2015. Important differences existed between and among them in terms of nature and extent of reporting. Here, we assess the implementation of these systems from different perspectives, including a description and comparison of collected data, disease metrics, usefulness, simplicity, flexibility, acceptability, representativeness, timeliness, and stability. This assessment demonstrates the limitations that the absence of premises identification imposes on certain animal health surveillance and response databases, and the importance of federally regulated frameworks in collecting accurate information in a timely manner. This study also demonstrates the value that the voluntary and producer-organized systems may have in monitoring emerging diseases. The results from all three data sources help to establish the baseline information on SECD epidemiological dynamics after almost 3 years of disease occurrence in the country.

A Porcine Epidemic Diarrhea Virus Outbreak in One Geographic Region of the United States: Descriptive Epidemiology and Investigation of the Possibility of Airborne Virus Spread.

This study describes a spring 2013 outbreak of porcine epidemic diarrhea virus (PEDv), using data from 222 swine sites in 14 counties area in 4 contiguous states in the United States. During the outbreak, the premises-level incidence of PEDv was 40.5 percent (90/222 sites). One of the three companies from which data were collected had a lower incidence (19.5 percent) than the other two companies (41.1 and 47.2 percent). Sow sites had the highest incidence of PEDv during the outbreak (80.0 percent). Spatial analysis showed that PEDv was clustered rather than randomly distributed, which suggested that sites near a positive site had increased risk of acquiring PEDv infection. Meteorological data were used to investigate the hypothesis that PEDv was spread by air. If airborne dissemination played a role in this outbreak, we would expect the direction of disease spread to correlate with the predominant wind direction. Two methods were used to determine the direction of disease spread--linear direction mean analysis in ArcGIS and the direction test in ClusterSeer. The former method indicated PEDv spread was south to slightly southwest, and the latter indicated spread was to the southeast. The predominant wind direction during the month of the outbreak was toward the south, with some southeast and southwest winds; the strongest wind gusts were toward the southwest. These findings support the hypothesis that PEDv was spread by air. The results, however, should be interpreted cautiously because we did not have information on direct and indirect contacts between sites, such as movement of trucks, feed, pigs or people. These types of contacts should be evaluated before pathogen spread is attributed to airborne mechanisms. Although this study did not provide a definitive assessment of airborne spread of PEDv, we believe the findings justify additional research to investigate this potential mechanism of transmission.

Previous infection of sows with a "mild" strain of porcine epidemic diarrhea virus confers protection against infection with a "severe" strain.

Porcine epidemic diarrhea virus (PEDv) infected approximately 50% of the US swine breeding herds from July 2013 to July 2014 as estimated by the Swine Health Monitoring Project. In the absence of effective vaccines or standard control protocols, there is an urgent need for evidence of cross-protective immune countermeasures. Here, we evaluated the response of 3-day-old piglets born to sows exposed seven months earlier to a mild strain of PEDv to challenge with a virulent PEDv isolate. Piglet survival to one week of age was 100% compared to 67% in piglets born to sows not previously exposed, and morbidity was 43% compared to 100%, respectively. At necropsy at 7 days of age, the PEDv Ct value was 23.6 (range 16.6-30.6) in intestinal contents, compared to 17.2 (range 15.9-18.5) (p<0.06) in litters from sows with no previous exposure to PEDv. The findings indicated that durable lactogenic immunity was present in sows previously exposed to a mild strain of PEDv and this immunity induced cross-protection to representative virulent PEDv. Thus, a naturally attenuated form of PEDv provided significant passive immune protection for seven months against piglet challenge with virulent PEDv.