Piglet diarrhoea and anaemia: diagnosis in the farrowing unit

Neonatal diarrhoea in piglets is one of the leading causes of disease and mortality in the farrowing unit. Even when piglets survive, the consequences to pig development and performance can seriously damage the farm’s finances and profits.

Diarrhoea (or scour) can have several causes, not all of them infectious. There is not a single approach to manage and prevent it. Problems with stockmanship, biosecurity, or nutrition, soon manifest as piglet diarrhoea. It is only natural to want a straightforward explanation whenever there is an outbreak, however, this simplistic way of looking at a very complex picture often means that efforts to manage the disease are unsuccessful. Neonatal scour should always be considered a multi-causal phenomenon.

There are four pillars that favour the appearance of diarrhoea in the farrowing unit:

• Poor immunity
• Poor environment
• Poor stockmanship
• Pathogens

These pillars work in tandem. For example, suppose a careless farrowing unit worker fails to ensure that smaller piglets drink colostrum; they will be susceptible to a host of pathogens, which also benefit from a dirty environment. In our example, as piglets begin to scour, the litter is given antibiotics indiscriminately, which damages their gut microbiome, making them even more prone to diarrhoea. Soon, cases start to mount and, even if not many piglets die, the impact will be felt most acutely in the profits. It is easy to see how poor management lies at the root of neonatal diarrhoea.

As pig farming intensifies, there is less room for error, so even in exceptionally well-managed farms there are occasional outbreaks. This is due in part to the exceptional resilience of some pathogens, such as coccidia, which are nearly impossible to eradicate from herds.

Poor immunity as a contributing cause of neonatal diarrhoea

The placenta prevents piglets from getting antibodies from their dam when they are in the womb. They can’t create their own defences either because they live in a practically sterile environment. Then, at farrowing, they are thrown defenceless into a hostile milieu. Thankfully, sow colostrum is packed with antibodies and piglets’ gut can "absorb" these life-saving defences. This is called "passive immunity transfer". It is passive because the piglet did not have to synthesise antibodies on its own (active immunity).

When piglets do not get enough colostrum, they are easy prey to any microorganism that is present in the environment. This means that not only dangerous bacteria and viruses can harm the newly farrowed piglet, but any microorganism, even beneficial ones, can quickly get out of hand. This is why piglets that do not drink colostrum die so quickly and why treatment with antibiotics is futile in these cases.

The window of opportunity closes quickly because antibody concentration drops quickly in milk and the piglet’s gut becomes impermeable to maternal antibodies, the piglet is no longer receptive to the sow’s immunity. Normally, the passive immunity transfer window closes at 48 hours at the latest. However, a well-managed farrowing unit makes it a top priority to ensure that all piglets get enough colostrum.

There are some other factors that can cause poor passive immunity transfer. Agalactia (when sows don’t produce milk) is a serious concern. Large litters, poor gilt selection (poor maternal abilities, too few or poor-quality teats, etc.), and an unfavourable environment can contribute to some piglets not getting colostrum. Stockmanship is crucial to increase the success of passive immunity transfer.

When the sows have not been exposed to certain pathogens, they will not have circulating antibodies against these diseases, so they will not be able to confer protection to their piglets, even if they drink enough colostrum. The consequence is that piglets simply will not be immune. This happens, for example, when replacement gilts are not correctly acclimated to the herd or vaccinated.

Sow selection has focused on prolificacy in the last decades, leading to very big litters that often surpass the dam’s ability to provide colostrum, milk, and iron to all its piglets.

Poor environment as a contributing cause of neonatal diarrhoea

Picture the following scenario: a litter is born to a top-performing sow, perfectly healthy, and drinks enough colostrum, but the farrowing pen is dirty, damp, drafty, and cold, without any additional heat source. To make matters worse, the sow is getting a poor-quality diet and is developing a shoulder sore that goes unnoticed. One would expect this litter to deteriorate quickly, and, in fact, it is only a matter of days before piglets start scouring and dying.

The environment affects farrowing unit performance in several ways. A poor environment causes stress in the sow, which can lead to less milk production, diminished appetite and, in the long run, more days to the next farrowing. If the sow is being affected, the piglets will have fewer resources to fend off disease and, sooner or later, they will begin to scour.

In a poor environment, piglets themselves will use their precious resources to simply stay alive.

Finally, a dirty environment provides many opportunities for pathogens to hide and, even with the best-quality colostrum available, sometimes the sheer amount of viruses and bacteria is so great (high pathogen burden) that diarrhoea becomes inevitable.

Bedding is a common source of contamination so it is shunned in most intensified systems. However, in more traditional farms it is very comfortable for piglets. Dirty bedding should be removed daily from the farrowing pen and replaced completely between litters.

Poor management as a contributing cause of neonatal diarrhoea

In modern pig farming, stockmanship and management remain crucial factors in the farrowing area. Good personnel work tirelessly to enforce biosecurity rules and therefore reduce the pathogen burden in the environment. They also take care of their piglets with an eye for cross-fostering and ensure that piglets get all the colostrum they need. Good workers also notice when something goes wrong, so they can limit outbreaks and reduce mortality.        

Pathogens that cause diarrhoea in neonatal piglets

There are many bacteria, viruses, and protozoans (one-celled parasites) than can cause neonatal diarrhoea in piglets. Some, such as coccidia, are practically ubiquitous, whereas others are more specific to certain regions or production systems, such as Porcine Epidemic Diarrhoea (PED). You should also keep in mind that some types of scour are more common at certain stages of the process. These are the most important in the farrowing unit:

Rotavirus, Transmissible Gastroenteritis (TGE), and PED

Viral diarrhoeas in piglets are characterised by a watery scour that lasts for a few days. Piglets can become dehydrated quickly. Coinfections with bacteria (such as Escherichia coli) are common and can dramatically increase the mortality of an outbreak. There is no treatment for viral infections, so veterinarians will treat the dehydration and coinfections as they appear.

Rotavirus is practically ubiquitous and very difficult to eradicate from a farm because of the virus’ triple-layer capsid, which makes it impervious to practically all disinfectants. TGE and PED are both caused by coronaviruses. TGE is devastating for piglets in naïve herds and can cause up to 100% mortality! Nevertheless, as the TGE becomes endemic on a farm, it becomes a self-limiting disease. PED is similar to TGE, but not as aggressive.

Coccidiosis

Coccidia (Cystoisospora suis) are probably the most economically significant parasites of pigs. These unicellular parasites invade the gut lining where they reproduce at a vertiginous rate, damaging the gut’s absorptive capacities. It is normally not deadly to pigs but it carries huge consequences for performance all throughout the production process. Subclinical infections (pigs without signs) are quite problematic for farms, because these individuals keep shedding oocysts (coccidia ‘eggs’) and contaminating the environment.

Coccidiosis diarrhoea is usually creamy, but it can progress to a more watery scour when other pathogens are involved. Treating coccidiosis is not very effective and not economically prudent. Therefore, the best strategy is to prevent piglets from getting the disease in the first place. There is a class of drugs known as coccidiostats that can be used for metaphylaxis on positive farms.

Clostridiosis

Clostridia are deadly bacteria that cause some of the most aggressive scours. Paradoxically, they are normal inhabitants of the gastrointestinal tract. Clostridia are also incredibly difficult to eliminate from the environment because they can form spores diminutive ‘seeds’ that are among the hardiest biological structures known to science.

Clostridiosis usually occurs when there is an imbalance in the gut that allows Clostridia to thrive. For example, when antibiotics are used indiscriminately, many beneficial bacteria that keep clostridial species in check die; soon thereafter, the population of clostridia explodes. When other pathogens, such as Coccidia, damage the gut lining, this creates the perfect environment for these bacteria. Finally, gorging can also favour clostridiosis; in fact, one of the telltale signs of the disease is that it is usually the biggest, fattest piglets that die first.

Between the most important Clostridia that cause diarrhoea in neonatal piglets: Clostridium perfringens type C (CpC), and C. perfringens type A (CpA), CpC is the most aggressive and causes haemorrhagic diarrhoea; piglets can die so quickly that they might not even have time to scour. CpA causes a pasty diarrhoea and is not as deadly. CpA is one of the most frequently diagnosed bacterial pathogen causing ND nowadays.

Escherichia coli diarrhoea

Colibacillosis is one of the most common scours of neonatal piglets. It is characterised by a profuse, watery diarrhoea that can dehydrate pigs quickly and cause them to die. E. coli comes in many varieties. Some are normal inhabitants of the gut. However, toxigenic strains can wreak havoc in the farrowing area. In fact, another name for colibacillosis is neonatal diarrhoea: it is the most typical of all piglet scours.

E. coli usually affects very young piglets but, when there are viral infections, older pigs can develop secondary colibacillosis.

Salmonellosis

This bacterial disease is most often associated with older pigs during the weaner and growing stages. However, it is also of concern to the farrowing area. The bacteria that cause salmonellosis in pigs are Salmonella enterica serovars Cholerasuis and Typhimurium. S. Cholerasuis is deadlier but it is often a problem later in life. S. Typhimurium is more common in piglets, though it has low mortality.

Salmonellosis should never be underestimated. First, pigs can shed bacteria in their faeces months after they recover, so it is easy to see how the disease can be introduced to the farrowing area. Second, salmonellosis is a zoonosis: it can affect humans too.

Other infectious diseases to keep in mind

A very interesting disease we should consider is the porcine respiratory and reproductive syndrome (PRRS). This viral disease does not cause diarrhoea in piglets by itself, but because it does produce agalactia in sows, it leads to scouring because of a failure of passive immunity transfer. Because it can infect piglets even before they are born, it is also an important cause of stillbirths and neonatal mortality.