Colibacillosis is an infection of the bacterium Echerichia coli (E. coli), and although it is harmlessly found in the gut of pigs, some strains cause disease — in particular, haemolytic E. coli, and specifically, enterotoxigenic E. coli (ETEC). These strains use fimbriae (long, thin appendages of bacteria) to attach to the gut wall, binding to specific receptors on the small intestine enterocytes. This enables the bacteria to colonize the gut and secrete enterotoxins. It is these that affect gut function, leading to diarrhea, dehydration, potentially septicemia and death. Piglets become infected through the environment, other scouring piglets and, most importantly, the sow herself. This is because close to farrowing time, sows excrete E. coli at a greater rate.
Symptoms of colibacillosis
Neonatal colibacillosis can become evident three days after birth, and it most commonly occurs in the first week of life. Symptoms include scouring along with severe dehydration; mortality can be high, and the onset rapid. In most cases, whole litters will be affected. Diagnosis is carried out by histological analysis of the villi along with isolation of the specific organisms.
Similarly, in post-weaning infections, a yellowish diarrhea and dehydration are seen — often occurring around two weeks after weaning. Feed intake is reduced, and pigs appear lethargic. However, mortality is not as severe (generally about 10 percent).
A yellowish, slightly mucoid, watery scour is seen in neo-natal colibacillosis. | Photo courtesy of Merck
Colibacillosis infections occur in both indoor and outdoor herds and can become chronic on the farm. The main effect for producers is a reduction in the number of piglets weaned per sow. However, even those who respond to treatment and survive may still be affected. Weaning weights are lower, and there are potential longer-term issues with gut health.
Risk factors
Whether or not piglets succumb to colibacilosis is due to a balance of factors. On one hand is the level of immunity passed to the piglets from the sow via colostrum and milk, then, on the other hand, is the degree of exposure the piglets had to the bacteria at birth. Later in the piglets' lives, E. coli can occur in conjunction with other pathogens to cause disease, such as viruses, coccidian and other bacteria, including clostridia.
Many believe that inappropriate weaner housing is the biggest risk factor for post-weaning colibacillosis.
Control strategies
It is essential to both reduce the spread of E. coli as well as the reservoir of infection. Increasing the immunity of the piglets and the sows is also key. Understanding the risk factors will enable producers to modify management techniques in order to reduce them — for example, the prolific use of foot dips, controlling pests and stopping the movement of pigs between groups during an outbreak.
Read more: 6 major piglet diarrhea causes and their management
Farrowing hygiene is particularly important. Pens should be thoroughly cleaned and disinfected, and the sow herself washed before introduction to the accommodation. In outdoor herds, arcs should be moved between batches and the bedding disposed.
In order to reduce the likelihood of an outbreak of colibacillosis, other pathogens need to be considered. “By reducing the overall infection pressure within a herd the incidence of disease lessens,” explained Miquel Collell, global swine technical director, Merck. “Ensuring the sow is as healthy as possible means that she will be able to pass on the best level of immunity to her piglets.” Raising the immunity of the sows has also been carried with feedback protocols — utilizing scour from infected litters.
“Suckling piglets are generally kept in good conditions,” Miquel said. “But after weaning, everything changes: environment, temperature, grouping and diet.” Feed intake and diet formulation can influence animal’s susceptibility to infection. This must be reviewed along with environmental conditions, if an outbreak occurs. Small amounts of creep should be available so that feed intake isn’t too great just after weaning, which can lead to proliferation of E. coli. Ensuring low viscosity and highly digestible ingredients are used in diets for newly weaned pigs will help prevent diarrhea. Feed additives, including probiotics and organic acids, are also used with the aim of creating a gut environment hostile to pathogen growth.
Medication
Oral antibiotics are the most common treatment for neonatal colibacillosis. Veterinary confirmation of a bacterial, rather than viral or coccidal cause, should be sought. Strain sensitivity testing should also be carried out to make sure a suitable antibiotic is used on the litters affected. In the case of a significant outbreak, the decision may be taken by the vet to dose all piglets on the unit at birth. Electrolytes are an important tool in the reduction of dehydration. They may be delivered in the drinking water or, in the case of seriously ill animals, given orally by syringe. Antibiotics will also be used in cases of post-weaning infections.
Vaccination
Vaccinating the sow can effectively prevent ETEC infections in neonatal piglets. Immunity is passively passed on through the colostrum and milk. There are several maternal vaccines on the market that have been extensively used to prevent colibacillosis. They induce the sow to produce antibodies against bacterial adhesion factors, preventing binding — hence diarrhea and dehydration. Some also offer protection against Clostridium. Sows and gilts are vaccinated during gestation, according to product specific protocols. “Porcilis coliclos is given to gilts for the first time six to eight weeks before farrowing, followed by a booster three to four weeks later,” said Miquel. “Then sows are given a single injection two to four weeks before farrowing, which is enough time to raise levels of IgG and IgA.”
The focus on reducing antibiotic usage in agriculture lends itself to the use of prophylactic strategies, including vaccination.
Producers should remember that optimal protection relies on adequate colostrum intake and management techniques should maximize this. “The importance of lactogenic immunity shouldn’t be forgotten, the sow’s milk provides good levels of IgGs,” he added.
Once piglets have been weaned, the antibodies in the sow’s milk are no longer able to protect them. Therefore, in order to prevent post-weaning colibacillosis, an entirely different strategy is required. Autogenous vaccines are available for the prevention of colibacillosis, but their effectiveness depends on certain conditions being met. “If an outbreak of diarrhea occurs, accurate diagnostics are essential,” described Miquel. “In order for autogenic vaccines to work the isolated strain needs to be both pathogenic and immunogenic.” An active mucosal immunity is required to protect pigs against post-weaning diarrhea.
Future strategies
The aim to reduce antibiotic usage in agriculture lends itself to the use of prophylactic strategies in pig production. Focusing on hygiene and management, alongside the use of vaccination, will improve immunity and reduce infection pressure. Certainly the results and experience of maternal vaccination protecting against neonatal colibacillosis are positive. Return on investment has been calculated to be 1:4 in the suckling period and 1:6 from farrow to finish.
The situation post weaning is more complicated. If diagnosis is clear and pathogen isolation good, autogenous vaccines can be a useful tool to prevent colibacillosis. However, many believe there is room for improvement in terms of weaner management. Perhaps, if their accommodations were better, the risk of colibacillosis would be less — then fewer antibiotics would be needed to treat diarrhea caused by E. coli and other pathogens. At the same time vaccine development is progressing, new strategies for weaners could augment management tool kits.
