6.4 How do antibiotics fit into the prevention and control of Ileitis and what can I expect from their use?

To use antibiotics for long-lasting control and prevention of Ileitis is very difficult because Ileitis typically affects a high proportion of pigs (at least 20%) within a building, on different moments of the growing and finishing phase making the disease an on-going clinical or sub­clinical problem. It is therefore vital that effec­tive treatment be administered to the affected and in-contact pigs over an extended period of time or at the onset of the clinical signs. The particular antibiotics known to be effective in both challenge and controlled field investigations include lincomycin, tylosin, tiamulin and chlortetracycline. Due to the differences between farms and their Ileitis problem, only general principles can be considered here. On farms where disease is common (endemic), the most appropriate means of targeted use may be following some known period of exposure. However, it can be difficult to establish when an outbreak starts and when that suggested time-point relates to build-up of the bacteria in the group. In other words, the infection can build up slowly or quickly, with variations in disease onset. This variation can occur on different farms and importantly on the same farm between different groups in the same building. Whereas on farms where the disease is uncommon or at a very low level, acute outbreaks can only be counteracted by antibiotics after the first animals have died or are suffering from the severe clinical symptoms.

It is now not considered appropriate to use antibiotics for long periods of the growing and finishing period. In the case of Ileitis, this tactic may actually make the situation worse, because it lowers exposure of pigs to the endemic disease and hence lowers the immunity in each group to the disease. If antibiotics are to be used, then they should be used in a “targeted’ manner. The most appropriate means of targeted use depends on the pattern of infection on each farm and when infection and disease are occurring. The use of blood serology and faeces testing may lead to a farm specific Ileitis profile which pinpoints the time of infection. This most often means that lesions due to Lawsonia intracellularis already have developed in the intestines which will lead to a decrease in growth, a decrease in nutrient uptake and an increase in feed conversion. It has not proved possible to eliminate Lawsonia intracellularis permanently from pig raising systems through antibiotics.