NHF: Enteroids as in vitro model for ileitis

Our new contribution to the National Hog Farmer was written by Dr. Talita Resende, a PhD candidate at the University of Minnesota under the supervision of Dr. Connie Gebhart. Talita’s research focuses on swine ileitis and models to better understand its pathogen: Lawsonia intracellularis. Today, she explains how she uses enteroids.

The small intestine is largely responsible for nutrient digestion and absorption in the gastrointestinal tracts of pigs, but it is also an ideal colonization site for enteric pathogens. The investigation of the interactions between host and enteric pathogens can be conducted in vivo, or in vitro, with advantages and disadvantages for each of the models. Enteroids, small intestinal organoids, represent a new in vitro approach to investigate those interactions. But why are enteroids a new approach and what are their advantages in comparison to the current models?

Enteroids are three-dimensional structures originated from embryonic stem cells, induced pluripotent cells or adult stem cells from intestinal tissue. Therefore, they present all the cell types and a structural organization similar to crypts and villi found in the small intestine. This complex structure offers ideal conditions to investigate the mechanisms by which Lawsonia intracellularis causes proliferative enteropathy – also known as ileitis – in pigs.

Science Page: Sow Herd Filter Study

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 note from Dr. Cesar Corzo who is starting a study on sow herd filtration and recruiting herds. The MSHMP mission goes beyond collecting data regarding swine herd disease status, it also includes research projects that are relevant to the swine community.

Objectives of the study

The objectives of the study are to describe the occurrence of PRRSv in the filtered sow herd population within MSHMP and to assess the associations between farm-level factors and the introduction of PRRSv into filtered sow herds. The results of the study may guide practitioners and veterinarians to modify their management and biosecurity practices in filtered sow herds.

Who can enroll?

All filtered sow herds of MSHMP participants will be eligible for the study. The database will be used together with the PRRSv incidence measure to understand occurrence of PRRS before and after filters were installed. A survey has been created to collect farm specific data such as:

  • Date when herd was filtered
  • Type of ventilation (negative or positive)
  • Back draft prevention methodology
  • Type of pre-filter and filter
  • Pre-filter and filter replacement frequency
  • Number of barns and load outs
  • Audit frequency
  • Frequency of gilt introduction and weaning events
  • Regional density

If you are interested in participating, please contact Dr. Cesar Corzo at corzo(at)umn.edu

Senecavirus A publications in English and in Spanish

A fair part of our audience originates from Spanish-speaking countries. Our researchers appreciate your support and your interest in our work. Recently, Drs. Matthew Sturos and Fabio Vannucci published an article in the journal Albeitar regarding Senecavirus A and its tropism for reproductive organs.

A quick summary of the article that can be found online in open access:

Se trata de un virus patógeno emergente en el ganado porcino. En este artículo se proporciona información general sobre el virus y el conocimiento actual de la patogénesis y las características de la enfermedad.

For our English-speaking readers, we recommend a previous publication on this page also by Dr. Sturos called Natural and experimentally-induced Senecavirus A infections in boars.

Happy reading!

Understanding Tail-Biting in Pigs through Social Network Analysis

Today, we are sharing a publication on pig welfare by our colleagues in the Outreach and Extension center at the University of Minnesota, Drs. Li, Zhang, Johnston and Martin. More specifically, the researchers focused their study on the effect of social network on tail-biting in pigs. The full-text of the article is available in open-access on the website of the journal Animals.

We know that pigs are social animals and that they naturally form social structures to maintain a cohesive group. However, we have little understanding of how those group dynamics affect deleterious behavior like tail-biting.  To answer the question of the association between social structure and incidence of tail-biting in pigs, the researchers created 18 groups of 8 pigs.

  • 6  groups were Littermates: all the 8 pigs were born from and nursed by the same sow.
  • 6 groups were Half-group of littermates: 4 pigs were born from the same sow whereas the 4 others came from the litter of another sow.
  • 6 groups were Non-littermates: all 8 pigs were born from a different sow.

Each group was housed in a nursery pen after weaning where the pigs stayed for the duration of the study until they reached 10 weeks of age. Researchers analyzed growth performances, tail injuries, and behavior.

Growth performances did not differ among groups in this study. However, littermates showed a higher incidence of tail-biting with 15% of the pigs showing chewing or puncture wounds with visible blood but no infection.

tailbiting and social networkBehavior was analyzed by videotaping the pigs 2 weeks after they were placed into their pens, 1 week later when each group was moved together to a new pen and 1 week after the move. The video recordings were viewed by a trained researcher to determine association interactions among pigs. Pigs were considered associated with each other if they were lying together frequently and with more than 50% or more of their bodies in contact with each other. For each pig (white circle in the figure above), researchers measured the direct association between each individual pig and its penmates (1) as well as the peripheral association among the penmates (2).

At the individual pig level, littermates had lower direct association than non-littermates and half-group of littermates, suggesting that littermates might be less socially connected directly among themselves. However, the indirect association among penmates did not vary.

Another interesting observation, although statistically insignificant, is that littermates appeared to spend less time in the lying posture than other groups.

Overall, littermates had a lower strength of social connections, more absent ties, and fewer weak ties, compared to non-littermates and half-group of littermates. Less social connection with pen-mates might predispose pigs in littermate pens to development of tail-biting. Regardless of litter origin, most pigs appeared connected by weak social ties and few pigs formed strong social ties with their pen mates.


The objective of this study was to investigate the association between social structure and incidence of tail-biting in pigs. Pigs (n = 144, initial weight = 7.2 ± 1.57 kg, 4 weeks of age) were grouped based on their litter origin: littermates, non-littermates, and half-group of littermates. Six pens (8 pigs/pen) of each litter origin were studied for 6 weeks. Incidence of tail injury and growth performance were monitored. Behavior of pigs was video recorded for 6 h at 6 and 8 weeks of age. Video recordings were scanned at 10 min intervals to register pigs that were lying together (1) or not (0) in binary matrices. Half weight association index was used for social network construction. Social network analysis was performed using the UCINET software. Littermates had lower network density (0.119 vs. 0.174; p < 0.05), more absent social ties (20 vs. 12; p < 0.05), and fewer weak social ties (6 vs. 14, p < 0.05) than non-littermates, indicating that littermates might be less socially connected. Fifteen percent of littermates were identified as victimized pigs by tail-biting, and no victimized pigs were observed in other treatment groups. These results suggest that littermates might be less socially connected among themselves which may predispose them to development of tail-biting.

Science Page: Sow Farm PRRS status classification survey

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 survey from the MSHMP team on the different protocols used to classify PRRS status.

Key points

  • The majority of veterinarians consider it important to classify sow herd PRRS status.Our survey showed that 8/21 follow AASV guidelines, with the others using alternative criteria.
  • Half of the surveyed veterinarians use processing fluids as part of their testing protocol for determining sow herd PRRS status.
  • Most of the respondents mentioned that AASV PRRS classification guidelines should be re-visited.

Twenty-one veterinarians from 12 participant systems and 1 non-participant group completed the questionnaire accounting approximately for 1.5 million sows.

When asked how important it was to classify sow farm PRRS status, 12/21 (57%) answered very important, 8/21 (38%) answered important. Among the most important reasons requiring PRRS status were:

  • Commingling of pigs downstream,
  • Timing the Depopulation/Re-population of growing sites with continuous flow, and
  • Defining gilt acclimation and introduction procedures.

The testing protocol to classify a farm as stable varied across and within systems. However, the most frequent sample collected was due-to-wean blood sampling. Other samples are shown in the figure below.

PRRS classification survey


Acclimation strategies in gilts to control Mycoplasma hyopneumoniae infection

Today we are sharing a review article regarding the acclimation strategies in gilts to control Mycoplasma hyopneumoniae infection published in Veterinary Microbiology by  the University of Barcelona in collaboration with Dr. Maria Pieters.

Key points

  • M. hyopneumoniae monitoring should be performed in incoming gilts and recipient herd.
  • Gilt acclimation against M. hyopneumoniae aids to maintain farm health stability.
  • Vaccination is the main strategy used to acclimate gilts in Europe and North America

Monitoring and diagnosis of M.hyopneumoniae

The article first covers how to assess the M. hyopneumoniae health status of the herd. Various methods of monitoring and diagnosis are detailed and compared with each other.

  • Most commonly used: M. hyopneumoniae antibody detection by ELISA but the interpretation of the results can be challenging.
  • Most useful technique: PCR on different respiratory tract samples.
  • No consensus on sample type to detect bacterial DNA in live pigs.

Classification of the herd based on incoming replacement and recipient herd


Proposed farm classification according to M. hyopneumoniae health status. (aELISA results (negative/positive) could depend on infection pattern in the farm and sampling time point.)


Clinical signs Lung lesions ELISA resulta PCR result
Negative Not observed Not observed Negative Negative
Provisional negative Not observed Not observed Positive Negative
Positive Subclinical infected I Not observed Not observed Positive/Negative Positive
Subclinical infected II Not observed Observed Positive/Negative Positive
Clinical affected Observed Observed Positive/Negative Positive

Prevention and control

Vaccination against M. hyopneumoniae, using commercial vaccines, is the most commonly used strategy to control its associated diseases in worldwide swine production systems.

However, since protection against M. hyopneumoniae infection by commercial vaccines is not complete, antimicrobial treatments are frequently required to control disease outcome. Several antibiotic classes are effective in reducing the incidence and severity of M. hyopneumoniae compatible lung lesions: macrolides, lincosamides, tetracycline, and fluoroquinolones among others.

Acclimation scenarios


The most common replacement origin used in Europe was external and that most respondents knew M. hyopneumoniae health status of replacement on arrival, being in most of the cases seropositive. Nevertheless, only 28% of respondents verified this theoretical M. hyopneumoniae status given as ELISA test results. Additionally, the most used strategy to acclimate gilt was vaccination alone (58%).

North America

Gilt Development Units are utilized to allow ample time to incoming gilt to gradually adopt the health status of the recipient herd. These acclimation facilities are in most of the cases continuous flow allowing an effective gilt exposure to M. hyopneumoniae. Gilt vaccination in North American swine industry was also recognized as the most common practice used at acclimation.

Natural exposure

Natural exposure was also used in both continents to help acclimate the incoming gilts to  M.hyopneumoniae. However, taking into account that pig-to-pig transmission of this bacterium has proven to be extremely slow , the ratio of infected and naïve gilts as well as the time of exposure are crucial and should be considered to achieve an effective exposure.



Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary causative agent of enzootic pneumonia (EP), one of the most economically important infectious disease for the swine industry worldwide. M. hyopneumoniae transmission occurs mainly by direct contact (nose-to-nose) between infected to susceptible pigs as well as from infected dams to their offspring (sow-to-piglet). Since disease severity has been correlated with M. hyopneumoniae prevalence at weaning in some studies, and gilts are considered the main bacterial shedders, an effective gilt acclimation program should help controlling M. hyopneumoniae in swine farms. The present review summarizes the different M. hyopneumoniae monitoring strategies of incoming gilts and recipient herd and proposes a farm classification according to their health statuses. The medication and vaccination programs against M. hyopneumoniae most used in replacement gilts are reviewed as well. Gilt replacement acclimation against M. hyopneumoniae in Europe and North America indicates that vaccination is the main strategy used, but there is a current trend in US to deliberately expose gilts to the pathogen.


Science Page: Assessment of PRRS area spread for sow herd outbreaks in US swine dense regions

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 project from Dr. Andreia Arruda in collaboration with the MSHMP team regarding Porcine Reproductive and Respiratory Syndrome virus (PRRSV) area spread for sow herd outbreaks in US swine dense regions.

Dr. Arruda has also been investigating PRRS seasonality in the US and how topography surrounding a farm influences outbreak risk.

Key points

  • Strong evidence of area spread was not found after evaluating three farm clusters located in two swine dense regions.
  • All barns of a nursery/finishing site should be sampled to define status.
  • Sick pen might not be the best target when sampling for PRRSV in grower pig sites

Background and Objectives

Area spread refers to the transmission of a pathogen (here PRRSV) through small particles in the air as well as through fomites on which the pathogen would have deposited on.

The objective of the study was to determine if the virus detected in a recently infected sow farm was similar to the one detected in neighboring farms (in other words: was local spread a likely source of infection?)

Methods and Results

35 farms were monitored for PRRSV. As soon as a farm broke, all of the neighboring farms were sampled for PRRSV independently of the type of production on site. If a sick pen was present on the farm, effort was made to include it in the sampling. Positive samples were then sequenced to compare to the original virus from the outbreak.

PRRS area spread arruda
Graphical representation of the results of one specific region.

For two of the three area spread assessments performed, no similar sequence to the one obtained from the farm under investigation was found. Also it was not always possible to detect PRRSV in sick pens of the growing pig sites sampled in our study.