Review of porcine epidemic diarrhea virus exposure techniques

Review of porcine epidemic diarrhea virus exposure techniques

Review of porcine epidemic diarrhea virus
exposure ­techniques
Matthew B. Turner, DVM
Prestage Farms, Clinton, North ­Carolina
Introduction
Since the introduction of PEDV into the US swine herd
in 2013, there has been a plethora of information generated about the virus itself, patterns of dissemination, duration of immunity, amplification rates, immunological
response, environmental stability, and losses associated
with infection. The initial response to control this coronavirus after a herd became infected was based on the
historical control methods developed for another coronavirus already present in the US swine herd, transmissible
gastroenteritis virus (TGEV). As PEDV spread rapidly
throughout the US swine herd, many veterinarians were
afforded the opportunity to try new techniques to control/eliminate the virus. In an effort to characterize how
veterinarians in the US were handling breeding herds
that had become infected with PEDV, a survey was distributed in December, 2014 to gather information about
current practices used for with PEDV infected ­farms.
Methods
An internet based survey was created and distributed
through fluidsurveys.com. Sixty (60) swine veterinarians
were invited to complete the survey and were chosen based
on recommendations from other veterinarians, practice
areas, and volume of sow herd interactions. 44 surveys were
completed (74% completion rate), 6 were started but never
finished, and 10 were never started. Surveys were completed in 9 different states, with all the major swine producing
areas of the US represented. The 7 page survey required an
average of just over 13 minutes to complete. The data from
incomplete surveys is not included and some responses
had to be interpreted and modified because it was entered
in different formats (sow count instead of % of herds for
example). Responses that could not be easily interpreted
were verified if possible before analysis was ­completed.
The total number of herds represented was 702 distinct
sow breeding herds, and the total approximate breeding
inventory was reported to be 2.19 million ­sows.
Results
Demographics of ­participants
What is the best description for your veterinary p­ ractice?
• Food Animal Practice (not swine exclusive): 4 ­(9.1%)
• Mixed Animal Practice (food animal and companion
animal): 1 ­(2.2%)
• Swine Corporate Practice (a single swine client):
20 ­(45.5%)
• Swine Exclusive Private Practice (multiple unrelated
clients): 19 ­(43.2%)
Do you have experience with any strain of PEDV that has
infected one or more sow breeding farms in the U
­ S?
• Yes:42 ­(95.5%)
• No: 2 ­(4.5%)
Response to PEDV infection in 702 sow breeding ­herds
How many herds were intentionally exposed to cause
infection and stimulate immunity after the herd became
­infected?
• 688 of 702 (98%) attempted to expose all animals in
the ­population.
Were replacement breeding animal entries stopped? *­
• Closed to replacement animals for greater than
26 weeks: 147 ­(20.94%)
• Closed to replacement animals for 16 to 26 weeks: 311 ­(44.30%)
• Closed to replacement animals for up to 16 weeks: 136 ­(19.37%)
• Replacement animals continued a normal delivery
schedule: 117 ­(16.67%)
* A single farm can be represented twice if their normal delivery is a 16 week or longer interval- the sum
of responses is greater than 100%. Results captured
and reported as a count of herds ­(count/688)
PEDV exposure ­techniques**
**Results were captured as an approximate percentage
of herds. The percentage of herds was multiplied by the
number of herds reported by the veterinarian to determine a weighted estimate of farm count, which was divided by the total number of herds intentionally exposed,
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2015 AASV Annual Meeting: Beyond Our Oath: Integrity, Intensity, Professionalism
which was 688. Results reported below are the weighted
sow farm count (weighted farm ­count/688).
Of the 688 farms where the herd was intentionally exposed to cause infection and stimulate immunity, what
was the source of infectious ­virus?
• Material from the farm being exposed: 573 ­(83%)
• Material from another farm: 82 ­(12%)
• Material amplified in inoculated pigs off site:
33 ­(5%)
Of the 688 farms where the herd was intentionally exposed to cause infection and stimulate immunity, what
was the type of material ­used?
•
•
•
•
Piglet feces or intestinal contents only: ­197 (29%)
Sow/gilt feces only: ­0 (0%)
Piglet intestinal homogenate only: ­382 (55%)
Combination of sow/gilt feces and piglet feces/intestines/intestinal contents: ­97 (14%)
• Other type: ­15 (2%)
Of the 688 farms where the herd was intentionally exposed to cause infection and stimulate immunity, was the
exposure material identical for all animals ­exposed?
• Exposure material was identical: 604 ­(88%)
• Exposure material was not identical: ­84 (12%)
Of the 688 farms where the herd was intentionally exposed to cause infection and stimulate immunity, how
many times was each animal ­exposed?
• 1 exposure: 68 ­(10%)
• 2-3 exposures: 534 ­(78%)
• 4 or more exposures: 96 ­(14%)
Of the 688 farms where the herd was intentionally exposed to cause infection and stimulate immunity, what
was the duration of exposure? (number of days from first
to last e­ xposure)
•
•
•
•
•
1 day: ­84 (12%)
2-7 days: ­339 (49%)
8-21 days: ­221 (32%)
22-42 days: ­37 (5%)
Greater than 42 days: ­7(1%)
• Water delivery device (water line injection): ­1(0%)
• Applied to the feeding/watering area without feed
present: ­37 (5%)
• Added the exposure material on top of feed- “top
dressed”: ­386 (56%)
• Another delivery method: ­5 (1%)
Gilt exposure/acclimation strategies and t­ echniques
For farms infected with PEDV, what is the planned exposure status at farrowing for replacements? Estimated by
percentage of farms, weighted byfarm count (% of f­ arms)
• Farrow a previously PEDV exposed replacement
animal: ­384 (55%)
• Farrow a PEDV naïve replacement animal: ­304 (43%)
• Farrow an unknown PEDV exposure status replacement animal: ­10 (1%)
Do you intentionally expose replacement animals to live
PEDV? Count of veterinarians (% of veterinarians) not
weighting by herd c­ ount.
• Yes: ­21(50%)
• No: ­21(50%)
Of those veterinarians that intentionally expose replacement gilts to PEDV, what is the age at the first PEDV
exposure (% of herds)? (Simple average of percentage,
not weighted by herd c­ ounts)
•
•
•
•
2-12 weeks: ­42%
12-22 weeks: ­31%
Over 22 weeks: ­21%
Variable age: ­5%
Of those veterinarians that intentionally expose replacement gilts to PEDV, what is the age at the last PEDV exposure (% of herds)? (Simple average of percentage, not
weighted by herd c­ ounts)
•
•
•
•
2-12 weeks: ­36%
12-22 weeks: ­37%
Over 22 weeks: ­22%
Variable age: ­5%
Of those veterinarians that intentionally expose replacement gilts to PEDV, how many exposures are administered (% of herds, not weighted by herd ­counts)?
Of the 688 farms where the herd was intentionally exposed to cause infection and stimulate immunity, how
was the exposure administered? (may be greater than
100% because many farms were exposed more than o­ nce)
• One exposure: ­77%
• Two exposures: ­8%
• 3 or more exposures: ­14%
• Mixed with feed to make a gruel/paste: ­210 (30%)
• Individually dosed sows by spraying or squirting the
inoculum on/in the nose/mouth: ­108 (16%)
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Of those veterinarians that intentionally expose replacement gilts to PEDV, what is the source of infectious
PEDV? (% of herds, not weighted by herd ­counts)
•
•
•
•
From the destination farm: ­57%
From another farm: ­16%
From inoculated piglets (amplified off ­site): 23%
Another source of PEDV: ­5%
Of those veterinarians that intentionally expose replacement gilts to PEDV, how is the exposure material distributed? (% of herds, not weighted by herd ­counts)
• Mixed with feed: ­17%
• Sprayed or squirted on/in the nose or mouth: ­21%
• Water delivery device (metered into drinking water):
­31%
• Applied to feed/water area: ­34%
• Natural exposure to shedding animals: ­5%
• Other: ­7%
Of those veterinarians that intentionally expose replacement gilts to PEDV, do you confirm infection occurred
through laboratory methods (serology or ­PCR)?
• Yes 8 ­(38%)
• No 13 ­(62%)
Of those veterinarians that intentionally expose replacement gilts to PEDV, are gilts moved from the exposure
site before entry into the breeding ­herd?
• Gilts are moved from the exposure site to the breeding herd: ­55%
• Gilts are moved from the exposure site to a cool
down site before entry into the breeding herd: ­42%
• Gilts are moved through 2 or more cool down sites
before entry into the breeding herd: ­1%
• Gilts are exposed while in the breeding population:
­1%
Of those veterinarians that intentionally expose replacement gilts to PEDV, do you monitor for shedding before
movement to the breeding ­herd?
• Yes 15 ­(72%)
• No 6 ­(28%)
Current actions for an outbreak in a naïve ­herd.
Only veterinarians who reported a PEDV infection were
surveyed (42 veterinarians). Results are a count (%) of
42 veterinarians who plan to utilize each management
­strategy.
Will you immediately start or continue gilt a­ cclimation?
• Yes: 35 ­(84%)
• No: 7 ­(17%)
Will you load the farm with replacement gilts to facilitate
a farm c­ losure?
• Yes: 39 ­(93%)
• No: 3 ­(7%)
Will you terminate pregnancy in groups you expect to
not ­live?
•
•
•
•
No: 32 ­(76%)
Yes, 1 week: 2 ­(5%)
Yes, 2 weeks: 6 ­(14%)
Yes, 3 or more weeks: 2 ­(5%)
Will you euthanize pigs at birth to facilitate a rapid clean
up, if yes how l­ ong?
•
•
•
•
No: ­4 (10%)
Yes, 1 week: ­13 (19%)
Yes, 2 weeks: ­17 (40%)
Yes 3 or more weeks: ­8 (31%)
Will you intentionally expose the sow farm to induce infection and stimulate i­ mmunity?
• No: ­2 (5%)
• Yes: 40 ­(95%)
What material would you use to expose farms to induce
infection and stimulate i­ mmunity?
•
•
•
•
Combination of exposure materials: ­ 8(19%)
Pre-made inoculum from another source: ­4 (10%)
Feces from farm piglets: ­10 (24%)
Intestinal tissue homogenate from farm piglets: ­
20 (48%)
How will you distribute the exposure material to induce
infection and stimulate i­ mmunity?
• Apply inoculum onto feed “top ­dress”: 11(26%)
• Apply inoculum to feed or water area without feed
present: ­3 (7%)
• Individually dose sows by spraying or squirting material on/in nose or mouth: ­19 (45%)
• Mix the exposure material with feed to make a gruel:
­7 (17%)
• Some other method of delivery: ­1(2%)
• Use a water delivery device: ­1(2%)
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2015 AASV Annual Meeting: Beyond Our Oath: Integrity, Intensity, Professionalism
Discussion
The findings of this survey are a simple overview and
summary of current practices related to PEDV infection
on swine breeding farms in the US as of December 2014.
There is no implication of a standard of practice and
there was no attempt to determine what practices were
or are most successful in elimination of PEDV from a
breeding herd. There is no doubt advances will be made
in the understanding of and management of PEDV in
the future that will render practices detailed in this text
obsolete, and possibly ­contraindicated.
Acknowledgements
The author would like to thank the veterinarians that
helped in the beta testing of the survey, the veterinarians
that took the time to complete the survey, and the AASV
for survey funding and technical ­assistance.
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