dr. montserrat torremorell - influenza: understanding the current state, future impact and what...
TRANSCRIPT
Swine influenza: Current state, future impact and what producers can do to reduce
their risk
Montse Torremorell, DVM, PhDLeman Chair, University of Minnesota
Introduction
• Influenza is a common cause of respiratory disease in pigs
• Worldwide distributed
• Multiple subtypes and strains within a subtype which difficult the control
• Influenza is shared among
pigs, poultry and people
UMN VDL 2008-2013
300
200
100
0
400
500
600
700
800
900
1000
Others
Untypable
H3 / N?
H3 / N2
H1 / N?
H1 / N2
H1 / N1
Influenza can be costly
• Economic impact– $3.23 difference from baseline in loss per
head placed (Dykhuis Haden et al., 2012)
– $10.41 difference from baseline in loss per head placed due to SIV/PRRSV combination (Dykhuis Haden et al., 2012)
– $10.31 ($0.89 ADG, $2.73 FC, $2.94 THI, $3.75 Vet Med) (Donovan 2005)
Current state• 1. Gilts and weaned pigs can be a source of
influenza virus Sub-population N Positive Prevalence
Gilts < 1 m on-site 625 73 11.7
Gilts > 1 m on-site 1767 37 2.1
Piglets 1796 94 5.2
Total 4188 204 4.9
Sow farms
Sampling Events
Pools(pools of 3 swabs)
n=52
n=252
n=2,520
44% +
26% +
15% +
How important are weaned pigs?
Allerson et al., 2013
Sampling event Sampling event
Farm 1 2 3 4 5 6 Farm 1 2 3 4 5 6 1 H1 H1 H1 27
2 28 3 29 H1 H1
4 30 H1 H1 H1 H1 5 H3 31
6 32 H3
7 33 8 34 H1
9 H3 H3 H3 35 H3 H3 H3 H3 H3 H3 10 36 H3 H3 H3/H1 H3 H3 H3
11 H1 H1 H1 37 H1 H1 H1 H1 H1 H1
12 38 H1 H1 13 H1 H1 39
14 40 H3 H3 15 41
16 H3 H3 42 17 43
18 44 H1 H1 H1 H1
19 H1 H1 H1 45 H3 20 46
21 47 H3 H3 H3 22 48
23 49
24 50 H1 H1 25 H1 H1 51 H1 H1
26 52 H1 H1 H1
Farm ID
Count of HA gene sequences compared
Subtype Lowest % identity between all sequences
1 3 H1 99.89 3 H3 99.711 2 H1 99.813 2 H1 99.419 3 H1 99.525 2 H1 99.830 2 H1 99.935 6 H3 98.836 6 H3 98.837 6 H1 99.438 2 H1 99.940 2 H3 10044 4 H1 99.847 2 H3 99.850 2 H1 99.751 2 H1 99.952 3 H1 99.8
• HA gene sequences similar across (+) sampling events within farm
• 3 sow herds tested (+) for 6 consecutive sampling events over durations of 156, 165, and 165 days
• Different viruses across farms
Current state
• 1. Weaned pigs are a source of influenza virus
• 2. Infections in growing pigs are highly prevalent
Current state
• 2. Infections in growing pigs are highly prevalent
32 farms tested monthlyfor 2 years (Jun 2009-Dec 2011)16,170 nasal swabs 746 (4.6%) tested positive
Corzo et al., 2012
EpidemiologyGrow-finish surveillance
Corzo et al., 2012
Genetic diversity in grow-finish sitesFa
rm Id
entifi
catio
n N
umbe
r
H1N1 pH1N1 H1N2 H1N2v H3N2 H3N2v Untypable Mixed Infection
Corzo et al., 2012
Current state
• 1. Weaned pigs are a source of influenza virus
• 2. Infections in growing pigs are highly prevalent
• 3. Infections in groups of pigs can be prolonged
Detection of influenza virus in an all-in/all-out wean-to-finish facility
Oral fluid and nasal swab results
0
20
40
60
80
100
0 9 16 26 35 47 58 69 79 96
Day of study
Per
cen
tag
e p
osi
tive
Nasal swabs
Oral fluids
Weaned pigs are an important source for virus movementProlonged detection of infection in growing pig populations
Positives Re infected
99 (75%) 29 (29%)
Positives Re infected
124 (98%) 102 (82%)
Current state
• 1. Weaned pigs are a source of influenza virus
• 2. Infections in growing pigs are highly prevalent
• 3. Infections in groups of pigs can be prolonged
• 4. People can be a source of new viruses into pigs
Sick people can infect pigs
• Multiple reports on human flu strains infecting pigs– H1N1 pandemic virus– H3N2s
• People contribute to the influenza genetic diversity found in pigs
• Not all strains transmitted equally
What can producers do?
• 1. Vaccination of influenza– Improvement of clinical signs but does not
always minimize transmission– Sow vaccination
• Pre-farrowing vaccination• Whole herd mass vaccination
– Interference with maternal immunity
Suckling Piglet Monitoring
0%10%20%30%40%50%60%70%80%90%
100%
21-Feb 10-Mar 22-Mar 6-Apr 25-Apr 10-May 25-May
14 days 14 days 14 days 14 days 14 days 14 days 14 days
Negative Suspect Positive
0%10%20%30%40%50%60%70%80%90%
100%
21-Feb 10-Mar 22-Mar 6-Apr 25-Apr 10-May 25-May
21 days 21 days 21 days 21 days 21 days 21 days 21 days
Negative Suspect Positive
At 14 days of age
At 21 days of age
Sow vaccination performed on Feb11 and Mar 11-14
CT value: 37.99
1 pig
Corzo et al., 2013
What can producers do?
• 2.Take a “PRRS-like” approach: – Understand where the viruses come from:
• What’s the source of virus?• Weaned or replacement animals or people or air?
– Start at the top– Assess whether/how different practices/strategies
work:• Vaccination – how should we vaccinate populations?• Herd closure• Early weaning• Others?
What can producers do?
• 3. Implement seasonal vaccination of farm personnel
What works needs to be done?
• 1. Better vaccines and know how to vaccinate
• 2. Deeper understanding of influenza transmission and epidemiology
• 3. Assess biosecurity programs to minimize introduction of new viruses and mitigate existing ones
Conclusions
• Influenza is a very important problem in pigs
• Control of influenza can be very frustrating
• Prevention of new infections should be a priority
• Seminar Title: PEDV, PRRS and Influenza: Understanding the current state, future impact and what producers can do to reduce their risk.
• • Presenters: Dr. Lisa Becton, National Pork Board [PEDV] – Dr. Montserrat
Torremorell, U of MN [Influenza] – Dr. Dave Wright, Veterinarian [PRRS]• • Seminar Format: Each presenter will have up to 15 minutes to discuss the most
up-to-date information about their area of focus. Topics of discussion should include, but are not limited to,
• 1. What is the current state of the health challenge in MN / nationally?• 2. What new developments have been made to control the health challenge?• 3. What can producers do to reduce their risk of exposure on their farms? • 4. What work still needs to be done?