Valnemulin (Econor® premix - Novartis) was centrally approved by the European Commission in January 2004, for the 'treatment of clinical signs of porcine proliferative enteropathy (ileitis)' caused by Lawsonia intracellularis and 'prevention of clinical signs of porcine colonic spirochaetosis (colitis)' caused by Brachyspira pilosicoli, to add to its original claim of the prevention and treatment of swine dysentery caused by Brachyspira hyodysenteriae.Following the first article on 'colitis)' (Pig World, March 2004), this second article looks at ileitis and the role of valnemulin in its treatment and control in the field.
Ileitis (Porcine proliferative enteropathy)
Ileitis is an infectious condition, caused by L. intracellularis, and characterised by thickening in the lining (epithelial cells) of mainly the small intestinal mucosa. Related conditions are necrotic enteritis, regional ileitis and the acute proliferative haemorrhagic enteropathy or 'bloody gut'.Infection is by the oral route, usually due to faecal contamination and is especially seen in continuous flow systems with poor hygiene (Collins and Love, 2003). The organism is ingested and quickly invades and multiplies inside the epithelial cells. Bacteria are shed and can invade other cells or may pass out of the host in the faeces and can infect other pigs. They can survive outside the host for 14 days. The thickening of the terminal small intestine (ileum), leads to poor absorption of nutrients and also diarrhoea hence the adverse impact on growth and feed conversion. Other bacteria appear to exacerbate the lesions, e.g. E. coli and B. pilosicoli. Mucosal changes appear 8-10 days after infection and peak at about 21 days when resolution starts to take place as immunity develops. Shedding of L. intracellularis starts at about 13 days post infection and may last for upto 10 weeks. Clinically the disease normally affects growing pigs 3-4 weeks after weaning, but may occur even in adults.
McOrist et al (1998) showed that valnemulin was extremely active against L. intracellularis and carried out a dose-titration study to look at the prevention and treatment of disease produced by an artificial oral challenge with cell cultures infected with L. intracellularis. In the prevention study, valnemulin was administered in the feed at 0, 25, 37.5 and 50ppm two days before infection and in the treatment part at 75ppm, seven days after infection until the trial end on day 21. There were seven pigs per treatment group. The pigs were then necropsied and the intestines examined for gross and microscopic lesions.
Table 1. Results of valnemulin dose-titration study using an artificial challenge of L. intracellularis in cell culture (McOrist et al 1998)
Marked improvements in performance were seen at the 75ppm valnemulin treatment level for both growth (27%) and FCE (27%) in comparison with untreated controls and microscopic lesions were eliminated.
Graph 1. Effect of varying levels of valnemulin in the feed on gross and histopathological lesions of ileitis.
In a field study carried out in the UK (Jones et al, 2004) on a small farm with a history of ileitis, one group was given valnemulin at 75ppm for 14 days and the other remained as an untreated control. The trial lasted 14 days and the pigs were weighed at the beginning and end and the feed eaten recorded. Clinically the pigs were examined for diarrhoea on a regular basis and samples were taken for PCR testing and confirmation of the presence of L. intracellularis. 
Table 2. Results of a UK field trial with valnemulin 75ppm for the treatment of ileitis (Jones et al, 2004)
Valnemulin 75ppm in feed was effective in reducing the clinical signs of ileitis although there was some self-cure taking place in the untreated controls by day 14. There was an 81% reduction in the shedding of the organism during the trial and a 19% improvement in growth rate and a 15% improvement in FCE. With these new claims, it can be seen (Table 3) that valnemulin offers the most protection against the three major enteric infections in grower pigs.
Table 3. Comparison of products activity scores on enteric infections and their effects on FCE and potential production losses
If one looks at the adverse effect of the diseases on FCE (data taken from clinical trials), one can calculate the cost of a disease outbreak say in grower pigs (8-12 weeks of age) and estimate the production loss of extra feed costs and compare it with the cost of in feed medication either for treatment or prevention. Valnemulin can now be used effectively and economically to reduce the acute losses from all three enteric diseases, ileitis, colitis and swine dysentery.
References:
Collins, A.M. and Love, R.J.(2003) Risk factors associated with Lawsonia intracellularis infection. Manipulating Pig Production Ed. Paterson, J.M., Australian Pig Science Association (Inc.) Werribee, Victoria, Australia, p. 28.
Jones, M.A., Gale, C.S., Roger, P.A., Burch, D.G.S. and Ripley, P.H. (2004) Assessment of the efficacy of valnemulin (Econor®) Premix in the treatment of naturally-occurring outbreaks of porcine proliferative enteropathy (PPE) (Ileitis) under field conditions in the U.K. Proceedings 18th International Pig Veterinary Society Congress Hamburg, Germany, in press.
McOrist, S., Morgan, J.H., Ripley, P. and Burch, D.G.S. (1998) In-vitro and in-life studies of efficacy of valnemulin for proliferative enteropathy (ileitis). Proceedings 15th International Pig Veterinary Society Congress Birmingham, England, 3, p. 114.
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