Detection of influenza A virus in aerosols of vaccinated and non-vaccinated pigs in a warm environment

Today we are sharing a publication from the Torremorell lab regarding the impact of vaccination (both homologous and heterologous) on the detection of swine influenza virus in aerosols. The full publication is available in open access online on the PlosOne website.

Influenza A virus can be transmitted by direct and indirect contact and aerosols. Indeed, the virus has been detected and isolated from aerosols generated from pigs with and without immunity. Since then, there has been increased evidence of the role of aerosols in influenza transmission among swine.

Vaccination is used in swine populations as a strategy to mitigate clinical effects and the economic impact of influenza infections. It has also been proven to reduce shedding in pigs. Additionally, a study on the transmission of influenza in ferrets showed that high temperature may decrease the risk of airborne transmission. Therefore, we wondered if combining vaccination and high temperature would affect the detection of influenza virus in the air.

The objective of this study was to assess the effect of  vaccination on the generation of influenza A virus bioaerosols under warm conditions in pigs with varying degrees of cross-protective immunity.

Material and Methods

36 pigs of three weeks of age, seronegative for influenza were separated into four groups:

  1. vaccinated with an influenza strain identical to the one used for the challenge (homologous)
  2. vaccinated with a commercial vaccine containing multiple strains of influenza, all different from the challenge strain (heterologous, multivalent)
  3. vaccinated with a commercial vaccine containing one influenza strain different from the challenge strain (heterologous, monovalent)
  4. unvaccinated, which received an injection of saline instead

Pigs were challenged intranasally and intratracheally with a strain of H1N1 influenza virus, two weeks after the last vaccination.
Serum collected the day prior to the vaccination and at the end of the study 14 days post inoculation were tested via hemagglutination inhibition (HI) and ELISA.. Nasal swabs and oral fluids were collected and tested via PCR. Air samples were collected three times a day and tested via PCR and virus isolation. Temperature and humidity were recorded every five minutes.

Results

Hemagglutination inhibition and ELISA

Prior to infection, pigs in group 1 (Vaccinated, homologous) had significantly higher HI titers compared to the other three groups. In the group 3 (vaccinated, heterologous monvalent) 4 pigs had HI titers against the challenge strain, while pigs in groups 2 and 4 were negative against the challenge strain. All groups were HI positive against the challenge strain at necropsy, however HI titers were statistically different between group 4 and groups 1 and 3.

Proportion of pigs infected

The proportion of pigs infected was significantly higher in group 4 than in the vaccinated ones. Also, the percentage of infected pigs in group 1 was significantly lower than in group 2, but there was no difference with group 3.

Torremorell vacc pigs aerosol influenza proportion negative pigs
Proportion of negative pigs over time

Nasal swabs and oral fluids

Pigs in group 4 had higher amounts of nasal virus shedding most of the sampling days compared to vaccinated groups. Additionally, group 2 had higher levels of IAV compared with groups 1 and 4. Oral fluid results were in agreement with nasal swab.

 

Torremorell vacc pigs aerosol influenza nasal shedding
Nasal shedding over time

Air samples

All air samples in the vaccinated groups tested negative by RRT-PCR. Air samples collected at days 1, 2 and 3 from NON-VAC pigs tested positive by RRT-PCR but negative by virus isolation

Abstract

The 2009 influenza pandemic, the variant H3N2v viruses in agricultural fairs and the zoonotic poultry H5N9 infections in China have highlighted the constant threat that influenza A viruses (IAV) present to people and animals. In this study we evaluated the effect of IAV vaccination on aerosol shedding in pigs housed in warm environmental conditions. Thirty-six, three-week old weaned pigs were obtained from an IAV negative herd and were randomly allocated to one of 4 groups: 1) a homologous vaccine group, 2) a heterologous multivalent vaccine group, 3) a heterologous monovalent group and, 4) a non-vaccinated group. After vaccination pigs were challenged with the triple reassortant A/Sw/IA/00239/04 H1N1 virus. Environmental temperature and relative humidity were recorded throughout the study. Nasal swabs, oral fluids and air samples were collected daily. All samples were tested by RRT-PCR and virus isolation was attempted on positive samples. Average temperature and relative humidity throughout the study were 27°C (80°F) and 53%, respectively. A significantly higher proportion of infected pigs was detected in the non-vaccinated than in the vaccinated group. Lower levels of nasal virus shedding were found in vaccinated groups compared to non-vaccinated group and IAV was not detected in air samples of any of the vaccinated groups. In contrast, positive air samples were detected in the non-vaccinated group at 1, 2 and 3 days post infection although the overall levels were considered low most likely due to the elevated environmental temperature. In conclusion, both the decrease in shedding and the increase in environmental temperature may have contributed to the inability to detect airborne IAV in vaccinated pigs.

Vaccination against Lawsonia intracellularis decreases shedding of Salmonella enterica serovar Typhimurium in co-infected pigs changes the host gut microbiome

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week,  we are sharing the summary of a publication by  Dr. Fernando Leite who recently received his PhD from the University of Minnesota. The full scientific article regarding the effect of the vaccination against Lawsonia intracellularis on the shedding of Salmonella typhimurium and the host microbiome is available on open access in Nature.

Materials and Methods

A total of five treatment groups were used:

  1. challenged with S. Typhimurium alone,
  2. challenged with both S. Typhimurium and L. intracellularis,
  3. challenged with S. Typhimurium and vaccinated against L. intracellularis,
  4. challenged with both S. Typhimurium and L. intracellularis and vaccinated against L. intracellularis
  5. a non-infected control.

Results

The greatest difference in shedding level between groups was found at 7 days post-infection. At this time point, the co-challenged animals from the vaccinated group shed statistically less S. Typhimurium per gram of feces than the animals from the non-vaccinated, co-challenged group. The co-challenged vaccinated group also shed significantly less S. Typhimurium than the singly infected S. Typhimurium group.
L. intracellularis vaccination did not have a significant impact on S. Typhimurium shedding when animals were singly infected with S. Typhimurium.

Leite Ileitis vaccination salmonelle co infection

 

At 7 days post-infection, different treatment groups had significant differences in their microbiome community structure. The co-infected vaccinated group clustered apart from all other treatment groups.

Conclusion

These results indicate that vaccination against L. intracellularis impacts the microbiome and reduces shedding of S. Typhimurium in co-infected animals.

 

The swine group is presenting its research around the world: come see us at the 2018 IPVS!

The summer has just started and our faculty and graduate students have attended multiple conferences to share the latest and most advanced results of their research. Do not miss them at the 2018 IPVS!

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Come see us at the 2018 IPVS

Multiple members of our group will be presenting at the 2018 IPVS in Chongqing, China.

Name Presentation Date Time
Cesar Corzo Regional monitoring for PRRSV Monday 11th 12:15pm
Talita Resende Instestinal lymphangectasis and lipogranulomatous lymphangitis in pigs Tuesday 12th 9:45am
Carles Vilalta New strategies for sampling piglets Wednesday 13th 10:00am
Maria Pieters The effect of gilt flow on Mycoplasma hyopneumoniae acclimation Wednesday 13th 12:15pm
Montse Torremorell Transmission of influenza A virus in pigs: the role of the piglet Wednesday 13th 13:30pm
Fabian Chamba Influenza herd-level prevalence and seasonality in Midwestern US breeding herds Wednesday 13th 14:00pm
Jose Angulo Elimination of vaccine porcine reproductive and respiratory syndrome virus as part of PRRS elimination program using load-closehomogenize method Wednesday 13th 14:45pm
Talita Resende Next-generation sequencing coupled with in situ hybridization: a novel diagnostic platform to identify emerging pathogens and new variants of endemic viruses Wednesday 13th 14:45pm

Do not forget to vote for Minneapolis 2022!

Please visit us at our booth as we are competing to host the IPVS in 2022.

IPVS_2022.002

 

Science Page: Update on EWMA all versus EWMA original 13

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week,  we are sharing an update on the EWMA comparison by the MSHMP team.

Key points:

  • Even though small differences between both EWMAs exist, the EWMA of the original 13 participating systems is still a good indicator of the overall PRRS EWMA.
  • Questions from participants are always welcome and help us to provide answers and insights to all of you.

REMINDER: WHAT IS THE EWMA?

The Exponential Weighted Moving Average (EMWA) is a statistical method that averages data over time, continually decreasing the weight of data as it moves further back in time.  An EWMA chart is particularly good at monitoring processes that drift over time and is used to detect small shifts in a trend.

In our project, EWMA is used to follow the evolution of the % of farms at risk that broke with PRRSV every week. EWMA incorporates all the weekly percentages recorded since the beginning of the project and gives less and less weight to the results as they are more removed in time. Therefore, the % of farms at risk that broke with PRRSV last week will have much more influence on the EMWA than the % of farms at risk that broke with PRRSV during the same week last year.

EWMA vs EWMA 13

Results from this year’s comparison

EWMA 13 is still a good representation of the overall EWMA. The reason that the EWMA 13 is still representative may be because they cover a wide area of the States and they still represent a high percentage of the final EWMA. A minor difference occurred in 2017’s summer as some farms of the 13 experienced outbreaks. However, as we have discussed in previous science pages each state or region seems to have a different EWMA pattern.

Last year comparison of the EMWA

Production Losses From an Endemic Animal Disease: PRRS in Selected Midwest US Sow Farms

In this publication in Frontiers in Veterinary Science, Drs. Valdes-Donoso from UC Davis and Andres Perez from the Center of Animal Health and Food Safety (CAHFS) at the University of Minnesota, measured the impact of Porcine Reproductive and Respiratory Syndrome (PRRS) on the production of weaned pigs.

To do so, they monitored 16 different sow farms, all parts of a single production system in the Midwest for 48 weeks and recorded a total of 8 indicators:

  • number of weaned pigs
  • number of stillbirths per litter
  • number of live births per litter
  • number of pre-weaned dead
  • number of sows farrowing
  • number of sows repeating service
  • number of sows aborting
  • number of sows dead

For each farm and each indicator, the 12 weeks before the outbreak served as a baseline for the farm performances and the data was recorded until 35 weeks post outbreaks. All of the outbreaks occurred during the second half of 2014. The inventory of the farms varied between 2,714 and 6,009 breeding females.

The following figure represented the weekly average for the 8 recorded parameters from 12 weeks pre-outbreak to 35-weeks post-outbreak.

Perez PRRS sow farm losses Midwest

Based on these results, it was estimated that a PRRS outbreak caused a 7.4% decrease in weaned pigs per sow year, i.e., 1.92 fewer weaned pigs per breeding unit. In an average sized farm of this firm, the slight reduction in farrowing yielded a decline of 249 fewer farrows per year. The chances that a sow repeats service increased by 37%, while aborted fetuses increased by 26% in a year with a PRRS outbreak.

The primary estimate (using 12 weeks as pre-outbreak period) is that PRRS reduced weaned pig production per farm by 7.4% on an annual basis, leading to a decrease in output value per sow year of $86.6, or $367,521 per farm year for an average sized farm. If instead we assume the outbreak began in t −1 (i.e., using 11 weeks as pre-outbreak period), the estimated reduction in weaned pig production was 7.6%, or $88.8 less per sow year and an average revenue loss of $376,773 among the farms studied.

Results showed that weaned pig production declined in week − 1, although statistically insignificant, as did several performance indicators. The data suggest that the average PRRS outbreak in this set of farms began at least one week before it was announced.”

The rise in abortions was the strongest signal of PRRSV activity in our data. Increased surveillance, particularly to rising abortions, may allow farms to identify PRRS more quickly.

The length of PRRS outbreaks, as well as their effects over time, is highly variable. The results of this study demonstrate that PRRS has a negative effect on weaned pig production for a longer time than previously estimated. Indeed, the estimated means of weaned pig production remained below the baseline throughout the 35 weeks that we are able to observe following the outbreak.

For more details, read the open-access publication on the Frontiers in Veterinary Science website.

Abstract:

Porcine reproductive and respiratory syndrome (PRRS) is an endemic disease causing important economic losses to the US swine industry. The complex epidemiology of the disease, along with the diverse clinical outputs observed in different types of infected farms, have hampered efforts to quantify PRRS’ impact on production over time. We measured the impact of PRRS on the production of weaned pigs using a log-linear fixed effects model to evaluate longitudinal data collected from 16 sow farms belonging to a specific firm. We measured seven additional indicators of farm performance to gain insight into disease dynamics. We used pre-outbreak longitudinal data to establish a baseline that was then used to estimate the decrease in production. A significant rise of abortions in the week before the outbreak was reported was the strongest signal of PRRSV activity. In addition, production declined slightly one week before the outbreak and then fell markedly until weeks 5 and 6 post-outbreak. Recovery was not monotonic, cycling gently around a rising trend. At the end of the study period (35 weeks post-outbreak), neither the production of weaned pigs nor any of the performance indicators had fully recovered to baseline levels. This result suggests PRSS outbreaks may last longer than has been found in most other studies. We assessed PRRS’ effect on farm efficiency as measured by changes in sow production of weaned pigs per year. We translated production losses into revenue losses assuming an average market price of $45.2/weaned pig. We estimate that the average PRSS outbreak reduced production by approximately 7.4%, relative to annual output in the absence of an outbreak. PRRS reduced production by 1.92 weaned pigs per sow when adjusted to an annual basis. This decrease is substantially larger than the 1.44 decrease of weaned pigs per sow/year reported elsewhere.

Science Page: Docking the tail or not: Effect on tail damage, skin lesions and growth performance

Pig tail
Credit: Jon Olav Eikenes

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week,  we are sharing a report by Dr. Yuzhi Li regarding the effects of tail docking in pigs.

Key points:

  • Many swine producers have been looking for an alternative to tail docking since it is a painful procedure for pigs.
  • A study examining welfare and performance of pigs with docked and undocked tails was performed
  • Performance was unaffected by tail docking, and it reduced incidence of tail damage

A study was conducted to evaluate the effect of tail docking on welfare and performance of growing-finishing pigs. Pigs, including 120 pigs that were tail-docked at birth and 120 pigs that remained with intact tails were used. Pigs were housed in 8 pens of 30 pigs in a
confinement barn for 16 weeks, with 4 pens each housing pigs of both sexes with docked or intact tails.

Results indicate that tail docking did not affect daily gain, feed intake, gain to feed ratio. During the study period, 5% of docked pigs were removed from their home pen due to tail damage, compared to 21% of intact pigs were removed for reasons associated with tail biting or tail damage. Consequently, 97% of docked pigs and 90% of intact pigs were sold for full value.

This study suggests that tail docking did not affect growth performance of pigs or eliminate occurrence of tail biting, but it reduced the incidence of
tail damage in pigs housed in a confinement system.

For more details, take a look at the full results table.