Scour in piglets

Thursday, November 25, 2021

The bad, the worse and the deadly.

By Jackie Clark

Scouring is an unpleasant reality that pork producers around the world face. Diarrhea in piglets can be caused by a variety of pathogens and can lead to consequences for the individual piglet's growth and productivity, survivability, as well as general herd health.

Better Pork connects with veterinarians and researchers to examine how farmers are preventing and treating scours and current research working to improve and expand those options.

How bad is it?

Scouring impacts piglets during "two different stages of production," Dr. Vahab Farzan, research scientist at the Ontario Veterinary College, tells Better Pork. Neo-natal diarrhea occurs in the farrowing room during the suckling period, and post-weaning diarrhea occurs in the nursery.

Neo-natal diarrhea can be devastating.

"In Europe, producers are really losing because of neo-natal diarrhea," says Farzan. The issue is serious in Canada as well.

"Diarrhea in piglets is a major cause of mortality and accounts for up to 70 per cent of losses during the lactation period," Dr. Francisco de Grau tells Better Pork. He's a veterinarian and the associate director of scientific marketing affairs for swine and poultry at Merck Animal Health Canada.

"Diarrhea is a result of abnormal functioning of the gastrointestinal tract and the main cause of mortality in piglets. The affected animals die from hypovolemic shock due to dehydration," he adds.

Aside from mortality, piglet diarrhea also results in "reduced growth rate and associated veterinary costs," says Dr. Charlotte Lauridsen, a professor in the department of animal science at Aarhus University in Denmark.

Producers may observe a lag in growth and dehydration in scouring piglets, but unseen internal damage to intestinal villi can also occur, leading to issues later on in life, de Grau explains.

"Piglets that scour when they are babies may have grower-finisher problems," says de Grau.

Neo-natal diarrhea

"Neo-natal scour is a significant issue. It's not by any means new, it's not on the rise, nor is it decreasing. It's a steady-state challenge for our industry," Dr. Clint Lichty, a veterinarian at South West Vets in Stratford, Ont., tells Better Pork.

The piglets face "transition from in utero to the harsh reality of the outside environment," he explains. "That piglet has been receiving all of its nutrition through the blood supply from the mother. Now it needs to suckle, create its own body heat and fight off infection. It's a huge challenge."

Colostrum is vital to piglet health.

"Piglets are born sterile and they need to travel from mom's rear end all the way to get the colostrum right away. In that space they can be infected by pathogens," says de Grau. "If the pig gets infected in that period of time, around day three they start showing signs of scours."

An initial infection can "damage the intestine and then other bugs in the environment start colonizing," he adds. "They might be indistinct from each other and often present in combination. The most common pathogens in commercial farms are rotavirus, porcine epidemic diarrhea (PED), transmissible gastroenteritis (TGE), Escherichia coli (E. coli), Clostridium and coccidiosis."

Salmonella can also be present, Farzan adds.

Genetic and environmental factors may also contribute to a piglet's likelihood of neo-natal scouring, he adds.

Early in life, "E. coli and rotavirus are probably the two most common enteric pathogens that a neo-natal piglet will face," Lichty says. Starting around 10 days old, they may also see parasite challenges like coccidiosis.

Post-weaning diarrhea

Post-weaning diarrhea is "a clinical effect that is happening over a high-stress or transitionary period," Lichty says.

The piglets are moving from a milk-based diet to a solid diet.

"In milk, you have protection for enteric bugs because the milk is covering the villi in the intestine and is protecting the piglets," explains de Grau. After weaning, "pathogens that they were already in contact with at the farrowing crate or new bugs that they picked up from pen mates at the nursery can show up."

Post-weaning scours "actually may tie all the way back to neo-natal gut health," Lichty says. "If their guts are already damaged by coccidiosis or other pathogens during their time nursing the sow, the weaning transition is made that much harder by the gut damage that persists."

E. coli is the most common cause of diarrhea immediately post-weaning, Lauridsen says. "Later on, other pathogens and nutrition are of major impact."

Generally, "post-weaning diarrhea is a very significant cause of economic loss for swine producers everywhere, not just in Canada. It's a global issue," says Farzan. Mortality or illness post-weaning causes greater economic losses because more money has now been invested in those piglets – parti-cularly feed costs.

Then, if they scour, "they are going to dehydrate, die, lose weight, or if they survive, they are going to lag in terms of weight gain," he explains.

Prevention & treatment

"The focus on neo-natal scouring for me is actually on prevention – easing that transition," Lichty says. Ensuring the farrowing room is warm and draft-free, and ensuring newborn piglets are dried as soon as possible can help minimize stress in early life.

"Another piece of the prevention puzzle is immunity. Most sows would be vaccinated prior to farrowing with a multivalent vaccine," he explains. Depending on the individual farm's vaccine program, they may cover bacterial infections, Clostridium, E. Coli and sometimes rotavirus.

"That immunity is passed onto the piglet through colostrum and milk," he explains.

The significance of colostrum cannot be understated.

"The sow placenta stops the antibodies from passing. So, it's very important for swine species to get the colostrum right away," says de Grau.

Post-weaning, "some producers vaccinate the piglets," says Farzan. "There are a couple of vaccines available. They are live vaccines; they're put in the water."

"But the uptake on Canadian swine is low," he explains. "Most producers vaccinate sows against E. coli so the piglets can receive maternal protection during the suckling period."

In addition to vaccination and monitoring nursing, farmers can manage their facilities to improve health states.

"Cleaning and disinfecting make a big difference," Lichty says.

Easing the transition from farrowing room to nursery can also help.

Piglets go "from primarily consuming milk to primarily consuming solid, plant-based feed basically overnight," he explains. "The prevention strategy is environmental. Putting piglets into a clean environment where the challenge is as low as possible and managing their temperature and the humidity of their environment reduces stress."

Also, "because the primary upset is in their digestive system, creep feeding and making sure these pigs are consuming as much plant-based feed as possible prior to weaning is helpful on that transition," he adds.

Some producers also use zinc as part of their prevention strategy.

"Usually, the zinc in feed is less than 500 parts per million (ppm) per kilogram which is basically promoting growth performance and is OK," says Farzan. Some producers use in-feed zinc with up to 2,500 to 3,000 ppm to control post-weaning diarrhea.

However, there are concerns about residual zinc in the environment and public health, he explains. So, we need to look for alternative methods which have no risk for our health and envi-ronment.

This is also a concern for European producers.

"Some countries are using high levels of zinc oxide (ZnO) – up to 2,500 ppm, during the first two weeks post-weaning," Lauridsen explains. However, because of environmental concerns, ZnO over 150 ppm will be banned in the European Union starting in June 2022.

Farmers in the EU have a growing interest in alternative strategies to address piglet diarrhea, she says. A similar trend is seen in Canada.

"Zinc and copper and those kinds of minerals are basically creating an environment in the gut where bacteria like E. coli can't survive or thrive as well and hence protect the pig. We've trended away from those kinds of interventions," Lichty says. "High zinc levels are associated with antibiotic resistance."

In addition to the potential for regulation of zinc, consumers are increasingly looking for meats pro-duced with fewer or no antibiotics, Lichty adds.

Producers who want to cash in on premiums on antibiotic-free pork will need to look at alternative treatment options, he says.

For example, Farzan and his collaborators are conducting research on certain in-feed additives, such as probiotics, and their impact on E. coli.

But generally, for now, "bacterial infections can effectively be treated with antibiotics," Lichty explains. "If it's a virus like rotavirus, we're relying mostly on supportive therapy."

A vet may suggest antidiarrheals or electrolytes, de Grau adds.

A more serious infection may involve reporting requirements.

"PED is the Number 1 scary scour bug," Lichty says. "At any stage, even adults will scour. The younger the pig is, the more dramatic the effect is."

If farmers observe many litters starting to scour and vomit over a short period of time, and if sows are impacted, they should contact their vet to talk about the potential of PED, he explains.

New approaches – E. coli

Farzan is leading a research project to better understand factors which may impact post-weaning E. coli diarrhea to help test interventions more accurately.

"We have an infection model for E. coli, but there is room to improve and optimize it," he explains.

"For example, some pigs genetically don't have receptors in their intestine for specific strains of E. coli to attach to so most of them don't become infected, even if you challenge them with E. coli," he says. "But if you're testing a control method on a group of pigs by challenging them with E. coli, you need to make sure all those pigs are susceptible."

So, he is investigating the response of pigs with and without receptors to E. coli challenges.

"The other element is age of the pigs," Farzan adds. E. coli receptors can develop early or later in a piglet's life, depending on the E. coli type. The researchers want to challenge pigs of different ages with E. coli and observe the difference in response.

Finally, the researchers want to find out "how much E. coli can make a pig sick?" says Farzan. Understanding more about pig susceptibility to E. coli, age of pigs, and infectious doses should improve the infection model.

"Hopefully other researchers can use it when they are going to study the effectiveness of control measures such as vaccines and probiotics," says Farzan.

Researchers at Aarhus University are working to develop a vaccine against post-weaning E. coli.

"Development of vaccines has been of major interest for a long time. However, phasing out antibiotic growth promoters in the EU in 2006 has probably promoted the initiatives, because of the increased diarrhea problem in the herds," Lauridsen says.

"To fight E. coli with a vaccine, you need the introduction of local immunity of antibodies of the immunoglobulin A-type in the gut. This is a challenge, but this is what makes the vaccine of major interest," she explains. Immunoglobulin A is an antibody that helps protect mucous membranes, like those in the intestines.

The technique is currently "being investigated in a small number of animals," she adds.

The goal is for the vaccine to "reduce the use of antibiotics, and thereby reduce the risk of antimicrobial resistance," Lauridsen says. "The ban on ZnO starts in 2022. However, the project runs until 2024, so I do not expect the vaccine to be an alternative to ZnO."

New approaches – rotavirus M

In December 2020, Merck received approval for a new vaccine approach for rotavirus and porcine circovirus 3 (PCV3), explains de Grau.

"This vaccine is an RNA-particle vaccine," he says. It uses "similar technology to the COVID vaccines."

Viruses have an external structural piece, and "researchers know that this particle is what stimulates the immune system … this is the part that attacks the villi. So, the vaccine will use a piece of this and develop protection for it," he explains. Scientists "take a piece of this virus, insert it into an adenovirus, replicate, and at the end you have a vaccine that is similar to an autogenous vaccine because it was produced for the virus you have on your farm."

For this process, veterinarians collect samples from the farm and take them to the lab, where scientists identify the strain and produce the vaccine.

"This technology is important in swine, especially because we can develop a vaccine in 14 weeks. And there are new diseases always in swine," de Grau says. "In less than three months they can start vaccinating, which is amazing. For a commercial vaccine it would take 10 years."

As of May 2021, "50,000 sows are beginning to be vaccinated or will be vaccinated with this technology for rotavirus and approximately 38 per cent of Canadian sows are vaccinated with this technology for rotavirus and flu or PCV3," he adds.

Future approaches

There is an ever-growing interest in how pig microbiomes may be enhanced or manipulated to improve health and productivity.

"The gut microbiome in the piglet is very important and there is a correlation between the bacterial population that they're going to colonize from birth to weaning in the intestine of the piglet and post-weaning E. coli diarrhea," says Farzan. His research involves farms in Ontario, Quebec, Alberta, Saskatchewan and Manitoba.

"We are looking at the gut microbiome a couple of days after farrowing and one week after, also at weaning and one-week post-weaning," he explains. "At the same time, we're collecting information about diarrhea in piglets."

The researchers "are looking at the rectal and vaginal microbiome of the sows to find out how the sow microbiome forms the outgoing piglets' gut microbiome," he adds.

So far, probiotic or prebiotic interventions "haven't been proven to be really successful as treatments" for piglet diarrhea, says Lichty. However, "if we can reduce the incidence in the first place, then we can reduce the need for antibiotics and using zinc or copper at high levels."

Consumer and general societal concerns about environmental impact and development of antimicrobial resistance may drive innovation in this area of research and add to farmers' toolkits for combating scour.

"At the end of the day, the consumer has influence," Lichty says.

"The premium drives that kind of production." BP