Valnemulin (Econor^® - Novartis) was originally approved in 1999 in the European Union (EU) for the prevention and treatment of swine dysentery caused by Brachyspira hyodysenteriae and enzootic pneumonia caused by Mycoplasma hyopneumoniae. It was the first veterinary medicinal premix to be centrally approved across the EU and is categorized as a prescription only medicine (POM). In January 2004 it was approved by the European Commission for the new indications 'for the prevention of porcine colonic spirochaetosis (colitis) caused by B. pilosicoli and the treatment of porcine proliferative enteropathy (ileitis) caused by Lawsonia intracellularis. This makes it the first premix to be registered for these three enteric infections in the EU, which is a great step forward given that, they are responsible for the majority of diarrhoeas encountered in growing pigs, as evidenced by a recent survey where they were implicated in diarrhoeas on 79% of the 85 units investigated (Thomson et al 1998).

In a two-part series, the use and efficacy of valnemulin for these two new enteric indications, colitis and ileitis, will be reviewed.

Colitis
B. pilosicoli is a spirochaete bacterium with many similarities to B. hyodysenteriae, the cause of swine dysentery. It causes porcine spirochaetal diarrhoea or colitis, a milder form of diarrhoea mainly seen in grower pigs. Clinically it affects pigs of 6-12 weeks of age with a non-specific grey to brown diarrhoea, frequently without blood but often with mucus, affecting upto 50% of the animals. There is usually a low mortality of 2-5% but a steady reduction in performance parameters such as growth rate and feed conversion efficiency of approximately 10-20%.

A recent artificial challenge study showed the comparative pathogenic effects of B. hyodysenteriae and B. pilosicoli (Thomson et al, 2003) over a 14-day period. The detrimental effects of B. pilosicoli were similar to the mildly pathogenic form of swine dysentery but only half as severe as the pathogenic form of the disease.

Table 1. Comparison of B. hyodysenteriae and B. pilosicoli infections in pigs

Group	Feature	Clinical score (%)	Pathological score  (%)	ADG (g)
Control	Uninfected	0	1	810 (-)
B. hyodysenteriae	Pathogenic form	29	45	590 (-27%)
B. hyodysenteriae	Mild form	8	16	740 (-9%)
B. pilosicoli	Pathogenic form	10	19	710 (-12%)

Valnemulin has been shown to be highly active against B. pilosicoli and also against strains potentially resistant to other antibiotics such as tylosin and lincomycin (Kinyon et al, 2002).

Table 2. Comparison of the MICs of various antimicrobials against 25 isolates of B. pilosicoli

Antimicrobial	MIC50 (µg/ml)	MIC90 (µg/ml)	Range (µg/ml)
Valnemulin	0.06	0.5	0.03-2.0
Tiamulin	0.125	1.0	0.06-8.0
Lincomycin	32	64	4.0->128
Tylosin	>512	>512	<16->512

In an artificial challenge study in 4-6 week old pigs, infected with B. pilosicoli and then medicated with valnemulin at 25ppm for 4 weeks, a substantial improvement in performance was seen and 97% of the pigs treated were completely protected from the disease (Morgan et al 2002).

Table 3. An artificial challenge study for the prevention of colitis caused by B. pilosicoli

	Untreated infected control	Valnemulin 25ppm	Improvement (%)
No of pigs	35	36	-
ADG (g)	470	610*	30
FCE	1.75	1.49*	15
Colonisation	32/35 (91%)	1/36* (3%)	97
Days with diarrhoea	111	31*	72
Ave diarrhoea score	0.54	0.19*	65

(Key: * p =<0.05)

Similarly in a UK field trial (Glossop et al, 2000), piglets were born outdoors and brought into straw-kenneled yards at weaning at about 4 weeks of age. Usually 2-4 weeks later they broke down with diarrhoea attributed to B. pilosicoli infection. A batch of pigs of 6 weeks of age was divided into two treatment groups, one as an untreated control and the other receiving valnemulin 25 ppm in the feed. Diarrhoea had already started in a few pigs (5%) at the beginning of the trial and rapidly developed in the untreated group (30%) but remained low in the valnemulin group. The trial lasted for 28 days and excellent performance improvements and diarrhoea control was achieved.

Table 4. Prevention of colitis with valnemulin 25ppm, UK field trial results

Results day 0-28:	Untreated control	Valnemulin 25ppm
No of pigs	60	60
ADG (g)	365	429* (18%)
FCE	2.167	2.026 (-7%)
Mean cumulative condition score	3.1	1.5*
Mean cumulative diarrhoea score	6.5	3.0*

(Key: * p =<0.05)

Valnemulin is highly active against the causal agent B. pilosicoli and has proven highly effective in preventing the disease in controlled infection and field studies, reducing bacterial shedding and gut colonisation as well as markedly improving performance in growth and FCE.
  (For further information visit www.econor.co.uk)

 

References:
Glossop, C., Whitehead, A., Ripley, P., Burch, D. and Fisch, R. (2000) Evaluation of the efficacy of Econor (valnemulin hydrochloride) in the prevention of naturally-occurring porcine colonic spirochaetosis. Proceedings 16th International Pig Veterinary Society Congress, Melbourne, Australia p. 12

Kinyon, J.M., Murphy, D., Stryker, C., Turner, V., Holck, J.T. and Duhamel, G. (2002) Minimum inhibitory concentration for US swine isolates of brachyspira pilosicoli to valnemulin and four other antimicrobials. Proceedings 17th International Pig Veterinary Society Congress, Ames, Iowa, USA 2, p. 50

Morgan, J.H., Demarest, H.L., Burrows, M.R., Ripley, P.H. and Holck, T. (2002) Model of colonic spirochaetosis for testing of Econor for prevention of disease. Proceedings 17th International Pig Veterinary Society Congress, Ames, Iowa, USA 2, p. 142

Thomson, J.R., Smith, W.J. and Murray, B.P. (1998) Investigations into field cases of porcine colitis with particular reference to infection with Serpulina pilosicoli. Veterinary Record 142, 235-239

Thomson, J. R., Murray, B.P., Henderson, L.E. Moore, L. Meikle, C.S. (2003) Virulence studies in porcine Brachyspira species by experimental challenge of pigs. Proceedings 2nd International Conference on Colonic Spirochaetal Infections in Animals and Man, Eddleston, Scotland Abstract 10

 

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