Managing acute and chronic PEDv infection in sow herds: what have we learned so far?

Luc Dufresne DVMDirector of Health Assurance

Seaboard Farms

• Total 47 sow farms 217,000 sows• 46 Sow farms 213,000 sows are PED infected

– 125,000 broke in May/June 2013 • Pod 302, Cell 2, Cell 4, Farm 10, Farm 9 (boar stud)

– 57,0000 broke in November 2013• Cell 6, Farm 1 and Farm 28

• 13,500 broke in March 2014• 10,000 broke in May 2014• 4,000 broke in November 2014

Control Approach I: the TGE approach

• Load-close-homogenize program similar to TGE.• Wean all piglets 10 days of age and older into an off-site facility. • Enter gilt to induce a minimum of 12 week closure of the farm• Start immediately exposing sows and gilts 2 to 5 weeks pre-farrow

with scours – The purpose of tissue feedback is to get all animals onsite uniformly exposed

to the virus as quickly as possible– Whole herd feedback is performed a minimum of 3 times in a two week period.– Ratio of 1 intestine to 10 sows for each feedback. – The number of sows recorded to show some clinical signs varied greatly from

less than 40% up to 90%.

Immunity

• In our experience herds return to normal (pre-break) pre-wean mortality 5 to 6 weeks after exposure.

• Using the above protocol, about 70% of herds’ pre-wean mortality remains normal for an extended period

• Unfortunately, the remainder of herds experience varying degrees of clinical relapse.

• Herds that broke during the 2nd wave of infection that occurred during winter never returned to normal and moved from acute to chronic infection.

“Classic” PED• n = 86 herds

• Avg TTBP = 7.4 wks• 95% CI = 1.7-13

• Avg lost 2,501/1000 sows• 95% CI = 64-4,939

Total company-Seaboard

Seaboard-Cell 4

Seaboard-Cell 2

Seaboard-Cell 6

Endemic sow herd

• Failure to induce complete herd protective immunity? • Waning herd immunity combine with a higher than normal

viral challenge• Additional risk factor– No or limited herd closure– Gilt exposure on-site or entering shedding gilts– Size of the farm (>5000 sows)– Colder temperatures – Walkthrough farrowing house

Lessons learned

• It is not TGE!• Virus exposure is the easy part • Herd Immunity is as high as it going to get 3 to 4 week after exposure

– Time is not on your side!

• Virus replicate at very high level especially in piglet– Do not allow the virus to replicate more than necessary

• Virus is highly infectious – Hygiene need to reach new standard– Minimize movement of animals and people

New protocol

• As soon as herd is diagnosed positive for PEDv– All piglet 7+ days are wean offsite– All remaining piglet are Euthanized immediately

• Exposure– Control inoculum (virus amplified on CD piglets)– Administer through backpack sprayer – 3 administration over a week

• Systematic euthanasia– All piglet are euthanized at birth for 21 days

• Not 14, not 18 ….21

• Hygiene– White wash all farrowing houses

• Immunity– Administer IPED+ vaccine to all sows and gilts 1 week pre-farrow

New protocol

• Results– 10 herds were exposed using the new protocol – 10 out of 10 were back to normal piglet output 6 weeks after

exposure– 8 out of 10 where non-clinical and negative on first group of piglet

that where not euthanized– 10 out of 10 were producing negative piglet 8 week after initial

exposure– None of the 10 farms experience re-break

-4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160%

20%

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% of baseline Weaned

old protocol new protocol

Gilt Exposure to PED

• Maintaining herd immunity appears to be the best solution until we understand better the virus or better tools are available to control or eradicate the disease

• Goal is having an immune population that produce negative piglet at weaning

• Gilt acclimatization– Insure homogenous gilt exposure to PED virus– Insure animal have time to develop immunity and stop shedding

before they are introduced into the sow farm

Gilt PED Exposure• Gilts exposed for the 1st time at 10-12 week of age– 1 time spray in nose/mouth– 1 time thru waterline

• Gilts exposed for a 2nd time at 18 to 24 week of age– 1 time thru waterline only– 4 week before shipment to cool-off site

Gilt Exposure

• Gilts are moved to cool-off site for 6 to 10 weeks– Oral fluids are collected and tested for PED 1 week before

shipment and every week animal are shipping from the barn/room

– If scour is detected at anytime around shipment• Movement is cancelled• Scour is tested immediately for PED by PCR

Gilt acclimatization

• Issue– Still sporadic sites are testing positive before shipment

• Often in winter• Re-test the following week and usually negative• Often moving animal to another site or a clean room on same site and they will test

negative – Environmental contamination

– Scour in mature gilts is more prevalent than expected• Often have to hold shipment for scour testing when we have loose stools observed

in gilts– Most of the time came back negative

– Need high level of oversight to insure exposure and sampling are done at the right time and all movement are approved by a veterinarian

Dealing with Endemic sow herds

• Increase Immunity– Vaccine will help– Virus exposure may be necessary especially on gilts

• Reduce pressure of infection– Bubble depop and unidirectional pig flow

• Through early weaning or off site farrowing• High hygiene and people movement are key and hard to control

– Reduce virus replication• Euthanasia of at-risk litter

– Gilt Litter– Scouring Litter

Gilt exposure in endemic sow herd

• Gilt immunity remains problematic– In herds that experienced PED re-break, gilts remained the most at risk animal

• Even if they had received live exposure as growing gilts

• Why?– When gilts are exposed as a young animal they are protected from the virus

but they do not appear to develop enough immunity to later form a lactogenic immunity.

– To do so, the gilt appears to need to be in mid to late-stage pregnancy to develop the gut/mammary gland immune axis

– Growing gilt exposure helps reduce the risk of disease re-activation in the sow herd, but will not, by itself, be sufficient for the gilt to adequately protect her litter in an endemic herd.

Evaluate PED shedding following live virus inoculation of gestating gilts

• Objective-o Determine immunologic response and duration of shedding following live virus

inoculation of gestating gilts previously inoculated during acclimation. – Tested 3 doses (106, 105, 104 viral copies per dose)

*equation without extraction factor (received 12/2/13); **equation with extraction factor (received 5/18/15)

The higher doses (106 and 105) resulted in higher titers (p<0.05).

PEDv FFN Titers were higher with increasing dose of PED inoculum.

5.83E+06 5.83E+05 5.83E+04 p-value*Day 0 160 160 120 0.4179Day 21 1280 960 240 0.0214

Median of PEDv FFN Titers

*Kruskal-Wallis comparison of mean ranks

Fecal and Anorexia scores were normal (score=1) for all doses within 7 days post-inoculation.

Clinically relevant fecal shedding ceased between 17 and 21 days post-inoculation.

• Implications-o Oral re-inoculation of gestating gilts with PEDv

– Higher titers were associated with higher doses– Shedding (estimated by Ct values) was not different b/t doses on days 0, 3 and

21 post-inoculation– Fecal scores returned to normal (score=1) 6 days post-inoculation for all doses– Anorexia scores returned to normal (score=1) 7 days post-inoculation

o Gestating gilts previously exposed to PEDv are positive (Ct<35) for PEDv by PCR for 17-21 days post-inoculation

Evaluate PED shedding following live virus inoculation of gestating gilts

Conclusion

• PEDv cases have dropped off significantly in 2015– Significant number of herds already infected– Increased our knowledge of the disease

• Epidemiology• Risk factor• Control and prevention

– It is likely that acute infection will remain endemic in growing pigs• Main risk factors remain the same

• Do not become complacent!