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When timed correctly, diagnostic-guided pulsed medication reduces death and productivity losses while permitting pigs to develop immunity to disease. The concept applies equally well to control respiratory disease in late finishing.

• A 2001 presentation case compared several vaccine procedures and feed medication for controlling death loss from respiratory disease in finishing pigs. The pulsed feed medication, using systemic antibiotics (Denagard^® plus chlortetracycline) reduced mortality by half compared to traditional, continuous feed medication approach using antibiotics with activity limited to the gut (tylosin and bacitracin). This change in feed antibiotic strategy provided the largest reduction of mortality of over 20 interventions tested.

• Antibiotics used strategically at therapeutic levels in another pulse-dosing regimen let pigs develop an immune response to Mycoplasma, even while suffering no performance or mortality loss increases compared to continuously medicated pigs. At the same time, overall antibiotic use was reduced from 12 to 5 weeks.

Moreau I.; et. al. 2001. Observations and description of an intervention method affecting death loss rate in all in/all out finishers. Proc Allen D. Leman Conf 2001:197-200.

Walter D.; et. al. 2000. The effect of a metaphylactic pulse dosing in-feed antimicrobial strategy on finishing pig health and performance. J Swine Health Prod 8(2):65-71.

Infection

Eradication?

Better diagnostics raise hopes for disease eradication. On ileitis, the outlook isn't promising:

• One study that blood sampled operations found over 96 percent positive. USDA survey data from 2000 showed 75 percent of 10,000-plus head grow-finish sites had the disease.

• One estimate suggests the dose of bacteria necessary to infect a pig is only about one-tenth the amount typically shed in feces.

• Studies in both the field and the lab show infection can persist for at least 10 weeks.

• One study showed that disease transmission occurred between all-in/all-out groups in spite of normal cleaning procedures.

• Lawsonia eradication attempts in Denmark have suffered high failure rates.

Johnasen, M.; et. al. Attempt to eradicate Lawsonia intracellularis by medication in 9 sow herds preliminary results. Proc Int Pig Vet Soc 2002(1)222.

Bane D.; et. al. 1997. Prevalence and management risk factors associated with Lawsonia intracellularis seropositivity in the U.S. swine herd. Proc A.D. Leman Swine Conference.

Winkelman N.L.; et. al. 1998. Use of a challenge model to measure the impact of subclinical porcine proliferative enteritis on growth performance in pigs. Proc AASP. 29:209-211.