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Modern swine production, with its new genetics, regulatory changes, social movements, and reduced antibiotic use, has become even more sophisticated and faces new challenges that are increasingly complex to solve.
Digestive diseases in pigs that were previously addressed individually, targeting a single pathogen, now form a porcine digestive complex that must be tackled from multiple angles. Poorly controlled digestive cases during the early weaning stages create favorable conditions for the combined action of digestive pathogens during the finishing phase, such as Brachyspira and Lawsonia (Table 1). Among these, the most concerning at present is swine dysentery (Hidalgo et al., 2010).
Table 1. Agents identified in mixed infections on finishing farms with enteric problems (Digespor, 2008-2009)*.
| Mixed infections | Farms (%) |
|---|---|
| B. hyo + L. intr | 25 (11.4%) |
| B. hyo + B. pilo | 2 (0.9%) |
| B. hyo + S. ent | 13 (5.9%) |
| L. intr. + B. pilo | 4 (1.8%) |
| L. intr. + S. ent | 11 (5%) |
| B. pilo + L. int | 4 (1.8%) |
| B. hyo + L. int + S. ent | 8 (3.6%) |
| B. hyo + L. int + B. pilo | 3 (1.3%) |
| B. hyo + L. int + B. pilo+ S. ent | 2 (0.9%) |
*Digespor, research group on digestive diseases from INDEGSAL (Institute of Livestock Development and Animal Health - University of León, Spain).
Which Brachyspira is responsible for digestive problems in pigs?
B. hyodysenteriae is the classical etiological agent of swine dysentery and remains the most prevalent in the EU, while B. hampsonii, discovered in the last decade, is widespread in North American farms. Another spirochete, B. suanatina, which can be isolated from poultry, has occasionally been found on farms with dysentery symptoms (Burrough ER, 2016) that are negative for other spirochetes, lawsonia, or salmonella.
There are other, weakly hemolytic Brachyspira species, some of which are associated with colitis (B. pilosicoli) while others may or may not be associated with enteric pathology (B. intermedia/B. murdochii) or appear non-pathogenic (B. innocens) (Carvajal et al, 2019).
What makes dysentery such a complex problem to control today?
The key factors are mainly:
- Low infective doses
- Long elimination periods
- Highly resistant agents in the environment
- Existence of biological vectors and fomites
- Increased control of antimicrobial use
All of this leads to easy contamination of farms, the establishment of enzootic infections after the initial outbreak, and very complex control measures and eradication programs.
With the incidence of dysentery in the Spanish industry currently at 20%, with varying degrees of clinical manifestation, the economic impact on production is very worrisome.
The disease may present as hyperacute, acute, or chronic, depending on factors such as increased proliferation and transmission, as well as the colonization of Brachyspira.
The occurrence of dysbiosis, more or less severe, nutrition or nutrition management, water quality, stress factors of all kinds (environmental, nutritional, management, etc.) will be determinant in how the disease presents and how it will impact us economically, if at all:
- The subclinical form may reduce production results to a varying extent or practically not affect them at all.
- The clinical form is aggressive with increased mortality and high morbidity that will cause clear deterioration of the animals, long emptying of fattening farms, increased balances and antibiotic treatments and economic losses that can reach up to €15 per animal.
In the mid-20th century, the measures taken against this disease were based on sanitary downtimes and intensive cleaning and disinfection.
At the end of the 20th century, eradication programs were based on prolonged antibiotic treatment, intensive cleaning and disinfection and pest management programs.
Today, with the current welfare regulatory frameworks, with sows housed in groups instead of individually (increasing horizontal transmission on the farm), new highly productive genetics with high consumption and growth, restriction in the use of antibiotics, higher infection pressure from viral processes, and increasing antibiotic resistance together with the presentation of mixed digestive processes, controlling the disease and its transmission is very complicated.
The market must seek a new disease control approach to achieve optimal production, economic, and sustainability results.
We must therefore approach it broadly, both in terms of time - digestive pathologies in finishing start at an early age - and in terms of the diversity of agents involved, even if one of them is the predominant.
Conclusion
Proper analysis and identification of critical points along the entire production process, where digestive pathogens are addressed from farrowing to finishing, cleaning and disinfection programs, sanitary management, and environmental and nutritional control, will help us design a control program that meets our expectations.
Vaccination programs adapted to the results obtained, proper adjustment of nutritional programs, the use of nutritional tools authorized by the health authorities and scientifically studied, frequently validated cleaning and disinfection programs both in various points of the farms and in transport, as well as a strict control of rodents and other vectors will allow us to reduce antibiotic treatments to what is strictly necessary and achieve the maximum profitability of our farm, allowing us to compete satisfactorily in a highly demanding market (Gómez García M, 2022).