Among the most important problems due to their negative effect on productivity and profitability in pig production are gastrointestinal disorders, particularly diarrhea in pigs.

Diarrhea in pigs is a clinical sign present in many pig diseases. The causes are multiple: the etiological agents involved are bacteria, viruses and parasites; nutritional factors may also be present.

Diarrhea types vary throughout the different productive stages: neonatal diarrhea, post-weaning diarrhea and gray fattening diarrhea. In industrialized production, they often have an endemic presentation because producers overuse antibiotics, which damaging intestinal health and increase bacterial resistance.

In order to preserve the effectiveness of antibiotics that are important for human medicine, the World Health Organization (WHO) calls for restricting the use of antibiotics only for cases where they are truly needed and eliminating their systematic use as growth promoters or preventively in animals.

In line with these guidelines there also is the restriction of zinc oxide (antidiarrheal), as cases of bacterial resistance have been documented, in addition to the negative impact it produces on the environment. In Europe, from 2022 on, its use will be limited to 150 ppm, which makes research for new alternatives necessary.

Natural solutions formulated with plant extracts (pronutrients, flora modulators) are a tool that has been shown to have efficacy for the control of diarrhea in pigs, replacing zinc oxide and growth promoters.

1. Causes of diarrhea in pigs

   • Viruses

• Rotavirus

This virus is widely spread in swine populations around the world and is the leading cause of acute gastroenteritis in young animals. There are four serotypes that affect pigs: A is the most commonly detected, but the infection can also be caused by types B, C, and E and, in some cases, mixed infections occur, with more than one serotype at a time.

The virus is transmitted fecal-orally and the infection results in the destruction of the enterocytes of the small intestine. Those affected are mainly nursing and young piglets, usually during the first week of life. The adult population experiences, on most farms, 100% seroconversion and does not get sick.

The damage caused by the virus in enterocytes affects intestinal absorption, causing aqueous, whitish and profuse diarrhea that may be accompanied by vomiting, leading to dehydration, although with low mortality.

• Porcine epidemic diarrhea (PED):

This disease is caused by a coronavirus (PEDv), which can affect any productive category. The most susceptible are piglets, where morbidity can reach 100%, being more variable in sows.

In piglets less than a week old, the disease causes acute digestive signs, vomiting, watery and profuse diarrhea, followed by an electrolyte imbalance and, in many cases, death. Mortality in this category ranges from 50 to 100%. After this period of maximum susceptibility, mortality can drop by up to 10%. Fattening pigs have signs similar to those of piglets, but less severe, that self-limit after a week, thus, affecting their performance.

Sows may not have diarrhea and simply develop symptoms such as weakness and anorexia. In cases where they lose their litter, they suffer from reproductive disorders such as agalactia or late estrus, caused by from the absence of piglets during the lactation period.

Acute PED outbreaks occur when the disease first enters a farm, after which it can disappear from the farm, stay in the farrowing pens when there is insufficient hygiene or persist among weaning piglets and fattening pigs, where it keeps circulating, causing mild post-weaning diarrhea. In these endemic cases there is a risk that, if piglets are poorly immunized from the sows, a new outbreak will occur.

• Transmissible gastroenteritis (TGE):

This disease, like PED, is caused by a monotypic coronavirus. It is the most virulent enterovirus that affects pigs and can affect all ages. Virtually, all pigs affected during the first week of life die from dehydration and, despite the disease becomes self-limiting after three weeks, economic losses are high.

The virus in pigs is transmitted orally and multiplies in the intestinal villi of the small intestine, causing their destruction. As a result, clinical signs are acute diarrhea and vomiting. The disease can persist in farrowing pens for three to four weeks until the sows manage to develop sufficient immunity to protect piglets.

Its presentation is similar to porcine epidemic diarrhea, but, in this case, the picture is usually less acute and with lower mortality in weaning piglets.

TGE can become endemic in farms that do not apply the all-in-all-out system or have poor hygiene conditions. In this form of presentation, the disease is manifested as mild diarrhea in weaning, with high morbidity and low mortality.

• • Bacteria

• Diarrhea by Escherichia coli, colibacillosis

Colibacillosis is a common disease in suckling and weaning pigs caused by colonization of the small intestine by enterotoxigenic strains of Escherichia coli. These strains of E. coli have fimbriae or pili that allow them to adhere to the jejunum and ileum epithelium. Pathogenic strains produce enterotoxins that cause fluids and electrolytes to be secreted into the intestinal lumen, resulting in diarrhea.

coli infections occur mainly at three levels: neonatal diarrhea (in the first few days of life), piglet diarrhea (after birth and until weaning) and post-weaning diarrhea (in the first few weeks after weaning). This bacterium may be present in combination with other pathogens such as rotavirus.

Diarrhea in newborn piglets can start just 2-3 hours after infection. Feces can be whitish, yellowish, or brown. Severe cases can lead to dehydration and cause above 70% mortality. The smaller they become infected, the higher this percentage. Diarrhea can become hemorrhagic and cause sudden death.

Once piglets are weaned, a period characterized by being frequently associated with digestive disorders, E. coli can infect them. In this category we can see signs such as lethargy and disorientation with a noticeable drop in consumption. However, diarrhea tends to be less severe and mortality is low, around 10%.

• Necrotic enteritis by Clostridium perfringens

It is a disease that is always a challenge for sows and their piglets. The responsible etiological agent is Clostridium perfringens type A and C. It is found in the soil and intestine of all pigs.

Piglets are infected with C. perfringens orally, from the feces of the sows, usually during the first days of life. Piglets are more susceptible to enteritis when they have not consumed enough colostrum.

When the necessary conditions exist in the host, the microorganism goes through the enterocytes of the jejunum and develops an exotoxin that causes necrosis of the structural components of the villi.

perfringens type A can cause mortality, but the enteritis it causes is milder, compared to that of type C, which is more virulent. Type A pigs usually have pasty diarrhea, their hairs can become rough, they usually recover, but we see the impact on stunting.

The picture is quite different when it is caused by C. perfringens type C: piglets have unpleasant-smelling diarrhea that is often bloody and many of them die quickly. In weak litters, type C mortality can reach a 100% and happen so fast that it occurs within a few hours, even before the sign appears. The most common presentation is acute.

• Clostridial diseases:

Clostridium difficile disease is characterized by diarrhea in newborn piglets. The course of the disease is so fast that they usually become infected a few hours after birth and even appear to be born with diarrhea.

Like C. perfringens, C. difficile is ubiquitous, and it is also present in the intestines of pigs. Under favorable conditions they multiply at high speed and produce toxins that cause diarrhea.

• Proliferative enteropathy or ileitis by Lawsonia intracellularis

The course of the disease is characterized, in its beginning, by a proliferation of immature intestinal epithelial cells that, inside, contain a large amount of Lawsonia intracellularis. Injuries occur in the last 50 centimeters of the ileum and the ascending third of the colon.

Changes in the intestine range from edema and hyperemia with thickening and redness of the mucosa to a brain-like mucosa. The picture may worsen until the appearance of clotted blood in intestinal lumen and necrotic accumulation in the mucosa.

It affects fattening pigs, generating heterogeneous litters in which a variable percentage of low-weight animals appear, most of which have chronic gray diarrhea.

1. • Parasites

Coccidiosis is the most common cause of parasitic diarrhea in piglets. It appears from the 5^th day of life. The most common etiological agent is Cystoisospora suis and yellowish, odorless diarrhea is characteristic. Other less common coccidia are some of the genus Eimeria and Cryptosporidium.

Traditional treatments are focused on the control of Cystoisospora suis and the most commonly used drugs are toltrazuril, trimethoprim-sulfonamide.

Intestinal optimizer pronutrients administered orally to piglets are an effective tool for coccidia control.

2. Traditional treatments and natural solutions of the diarrhea in pigs

   • Preventive

• Natural solutions 

– Pronutrients

In their natural state, animals instinctively consume plants containing pronutrients. These are active botanical molecules needed in small quantities for the proper functioning of the organism. Pronutrients should be added to commercial diets to boost organ function and increase resistance to animal infections.

Pronutrients work by stimulating certain portions of the DNA to activate specific genes that would not be expressed or whose expression would be reduced. This DNA stimulation produced by pronutrients increases the synthesis of functional proteins, improving the physiology of the target organs.

There are different types of pronutrients. The following are those that are applied to prevent enteric diseases that occur with diarrhea in pigs.

– Intestinal conditioners

Intestinal conditioners are a group of pronutrients that have enterocytes as target cells. In small amounts, they promote the regeneration and activity of these cells, in this way, the intestinal mucosa is better organized, favoring the absorption of nutrients. Increasing the renewal rate of enterocytes improves mucosal integrity and limits colonization by pathogenic bacteria. In addition, cells are renewed quicker, thus limiting colonization by bacteria.

Both in vitro and in vivo studies have shown that this increase in the absorption levels of vitamins and aminoacids improve growth and conversion rates.

Because of their characteristics, conditioner pronutrients can be used to replace growth promoters.

– Results of the use of pronutrients in post-weaning pork

– Intestinal optimizers

Pronutrients that act as intestinal optimizers promote local immune system activity in the gut, thus, cells in the local immune system are ready to react to protozoa such as Cystoisospora suis and other pathogens during their passage through the intestine.

– Use of optimizing pronutrients in suckling pigs

– Gut microbiota modulators

There are natural solutions on the market that have the ability to balance the intestinal flora, limiting pathogenic bacteria and promoting the development of beneficial flora.

The cimenol ring is a botanical extract used as a preservative and intestinal biocide. It is effective against E. coli, Salmonella, Clostridium and other microorganisms related to diarrhea.

The modulation of the microbiota produced by the biocidal effect of the cimenol ring prevents diarrhea and improves the productive parameters of pigs at different growth stages.

An indirect method for controlling diarrhea in piglets is to work on the sow microbiota. The cimenol ring, given prior to farrowing and during lactation, decreases the bacterial load of maternal feces Which is the main source of piglet infection.

– Productive parameters and effect on the microbiota with the use of cimenol ring in post-weaning pigs

• Antibiotic growth-promoters

Antibiotics are commonly used to control bacterial diarrhea.

Antibiotic growth promoters (AGPs) are continuously used at subtherapeutic doses to monitor the development of bacteria associated with diarrheal processes and promote development.

The benefits of AGP are well known, however, the residues they leave in meat and the resistance that bacteria acquire are the reasons why the legislation of different countries prohibits or limits their use, with the aim of safeguarding human health.

In addition, the European Union has banned them since 2006.

• Vaccines

There are E. coli vaccines on the market consisting of dead strains, certain pathogens, specific antigens or a combination thereof. Vaccines combining Clostridium perfringens’ endotoxin antigens with E. coli antigens are also used.

Auto-vaccines are another method used for immunization. These can be produced in the laboratory from pathogens isolated on the same farm they are to be used.

As a less complex tool, farms can apply the feedback system. It is a process of collecting infective material from piglet feces with diarrhea that is then diluted and orally administered to sows or gilts to immunize them. This immunity will be transferred to their piglets during lactation.

Antiviral vaccines have not been shown to be sufficient as a single prevention measure. While they exist for the rotaviruses and coronavirus mentioned above, biosecurity measures, as well as the control of secondary infections, are essential to reduce their morbidity.

To improve the effectiveness of vaccination, there are natural tools on the market. Immunostimulant pronutrients are biologically active molecules that aim to stimulate specific and nonspecific immunity. They are vaccine enhancers and are used strategically over different periods. Their use is indicated both for sows, as they will improve antibody titer in colostrum, and in combination with the vaccination of pigs at any stage of life.

• Zinc oxide

It is a compound widely used for the prevention of diarrhea in piglets. Incorporated at 3000 ppm in feed is effective for controlling diarrhea-causing bacteria, however, it is necessary to use this ingredient in high doses due to its low bioavailability (22%), which poses a risk to the environment. As a result, its use will be limited in Europe to 150 ppm from 2022, limitations that will soon reach the rest of the world.

• Curative treatments

Another strategy for controlling bacterial diarrhea is the use of antibiotics at therapeutic doses. They can be administered parenterally or in pulse-shaped food.

Despite being used at therapeutic doses, administration in successive cycles results in a lower sensitivity of bacteria to these antibiotics, with the risk of resistance.

Their use is limitated in many countries (e.g. European Union), where veterinary prescription is necessary, as the veterinarian should evaluate the group of animals concerned and decide whether antibiotic treatment is justified.

3. Conclusions

Veterinarians, as health workers, are committed to the guidelines set by the World Health Organization, which focus on the systematic reduction of antibiotic use. This recommendation aims to preserve the effectiveness of antibiotics for human health.

Today, there are different natural solutions available to control diarrhea (pronutrients, cimenol ring), which allow us to reduce the use of antibiotics and the environmental impact of some additives.

To know the most prevalent etiological agents in diarrheal disease will allow us to develop a preventive strategy in order to reduce the impact or establish an early diagnosis and appropriate treatment.