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PED Update in US: Downward Trend in Cases Continues

04 April 2014

US - The total number of farms that have tested positive for the Porcine Epidemic Diarrhoea (PED) virus now stands at 5,267, writes Jackie Linden. There are further signs of a slow-down in new case submissions and no new states have reported positive results in the latest weekly report.

The National Animal Health Laboratory Network (NAHLN) reports 247 positive accessions out of 802 tested at eight veterinary diagnostic labs. In addition, the Network adjusted last week’s number down to 270. This maintains the general downward trend in positive case submissions. No new states reported a confirmed case, so the number of states reporting at least one confirmed case of PED remains at 27.


US states with PEDv-positive swine accessions

Pig Farms Testing Positive for PEDv: 5,267

The total number of pig farm samples (termed 'laboratory biological accessions' in the official report) that have tested positive for the PED virus (PEDv) since April 2013 now stands at 5,267, which is 247 more than the previous week.

For the current month to date, 3,373 farm samples have been tested, of which 1,088 or 33 per cent tested positive for the PEDv in the latest report for the week of 29 March 2014.

Since testing was fully reported in November 2013, 13,090 farm samples have been tested, of which 33 per cent have tested positive for the PED virus.


Figure 1. Number of pig farm samples positive for PEDv
(since April 2013; data from NAHLN)

Results by age class

Suckling pigs

For the current month to date, 490 farms have been tested, of which 252 were positive for PEDv.

Since testing was fully reported in November 2013, 1,731 farms have been tested, of which 1,106 or 52 per cent tested positive for PEDv.

Nursery pigs

For the current month to date, 502 farms have been tested, of which 180 were positive for PEDv.

Since testing was fully reported in November 2013, 2,214 farms have been tested, of which 986 or 38 per cent tested positive for PEDv.

Grower/finisher pigs

For the current month to date, 487 farms have been tested, of which 114 were positive for PEDv.

Since testing was fully reported in November 2013, 2,414 farms have been tested, of which 1,064 or 31 per cent tested positive for PEDv.

Sows and boars

For the current month to date, 274 farms have been tested, of which 86 tested positive for PEDv.

Since testing was fully reported in November 2013, 933 farms have been tested, of which 489 or 35 per cent tested positive for PEDv.

Unknown age class

For the current month to date, 1,757 farms have been tested, of which 3489 tested positive for PEDv.

Since testing was fully reported in November 2013, 6,220 farms have been tested, of which 1,749 or 26 per cent tested positive for PEDv.

Results by state

No new states have reported a first confirmed case of PED in the state this latest report so the total number of states reporting at least one confirmed case of PED remains at 27.

The total number of positive accessions on this report is 5,270 - 247 more than the previous week.

Those states with 50 or more positive tests are: Iowa, 1,694; Minnesota, 838; North Carolina, 538; Illinois, 450; Oklahoma, 336; Indiana, 275; Ohio, 234; Kansas, 219; Missouri, 111; Michigan, 93; Pennsylvania, 74; Nebraska, 73; Colorado, 64, Texas, 53 and South Dakota, 52.

For the most recent week (week of 23 March), 48 of the 247 new positive results were in Iowa, followed by Minnesota (45) and Illinois (43).

Individual Pigs Testing Positive for PEDv: 17,275

The total number of individual swine samples (termed 'biological samples' in the official report) since testing began in June 2013 now stands at 17,275, which is 898 more than the previous report.

For the current month to date, 13,287 samples have been tested, of which 3,478 or 26 per cent tested positive for PEDv.

Since testing was fully reported in November 2013, 52,818 samples have been tested, of which 27 per cent tested positive for PEDv.


Figure 2. Number of pig samples positive for PEDv
(since June 2013; data from NAHLN)

Environmental Samples Testing Positive for PEDv: 3,689

The total number of environmental samples testing positive since testing began in June 2013 now stands at 3,689, which is 251 more than the previous report.

For the current month to date, 3,582 samples have been tested, of which 888 or 25 per cent tested positive for PEDv.

Since testing was fully reported in November 2013, 12,744 samples have been tested, of which 24 per cent tested positive.


Figure 3. Number of environmental samples positive for PEDv
(since June 2013; data from NAHLN)

Notes on the report

These data are collated by USDA APHIS VS NVSL National Animal Health Laboratory Network (NAHLN) and cited by the American Association of Swine Veterinarians (AASV) in a report dated 2 April 2014.

Veterinary diagnostic laboratories that have voluntarily reported PEDv testing data to NAHLN include: University of Georgia–Athens, University of Illinois, Iowa State University, Kansas State University, University of Minnesota, Nebraska Veterinary Diagnostic Center, Ohio Department of Agriculture, Purdue University, Michigan State University - Diagnostic Center for Population and Animal Health and South Dakota State University. This data does not include testing conducted at private diagnostic laboratories, at the NVSL, or for research purposes.

Data summaries provided in this report reflect the most current and complete data available at the time the report was prepared, and summaries in this report may differ from those provided in past reports.

Monitoring of PEDv testing started the week of 16 April 2013; April monthly totals include samples tested starting in that week.

USDA NAHLN began collating PEDv testing data on 16 June 2013. Weekly data prior to that date were provided by Iowa State University Diagnostic Laboratory. During the 2013 federal government shutdown, the University of Minnesota diagnostic collected and reported PEDv testing data (weeks of 22 September to 6 October 2013). Data from all sources are compiled in order to be as comprehensive as possible.

In general, a laboratory accession is a set of samples received at the laboratory where the samples were collected by a practitioner on a single premises on a single day. Therefore, each laboratory accession represents a single swine herd and each sample represents an individual animal tested for PEDv on a given date. Because multiple swine within a herd are often simultaneously infected, analyses commonly use the laboratory accession as the epidemiological unit of interest.

Initially, some testing laboratories only provided data on PEDv-positive accessions and samples. Data on PEDV-negative accessions and samples became available from all laboratories starting November 2013. Therefore, summaries of the 'total number tested' (e.g. number of accessions tested or number of samples tested) were calculated for samples tested on or after 1 November 2013.

Age classes are defined as suckling (up to one month old or still on sow), nursery (one to three months), grower/finisher (three to eight months) and sow/boar (older than eight months).

This report does not currently include results of testing on feed samples.

This report only includes PCR testing data at this time, with addition testing types to be added to the report as information on the performance of new assays becomes available.

The format for this report is currently in transition as stakeholder feedback is incorporated.

 

Further Reading

Find out more information on PED by clicking here.

Jackie Linden

Jackie Linden

Top image via Shutterstock



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