The Effect of Tilmovet® Feed Medication on PRRS-Positive Herds

Figure 1. PRRS virus - an enveloped RNA virus

Figure 2. Lung from pig suffering from porcine respiratory disease complex (PRDC) - concurrent presence of PRRSV, M. hyopneumonia, P. multocida. (Images courtesy of P.G. Halbur)

Tilmovet® adminstration in PRRSV-viraemic pigs post-weaning

A study was conducted in a transition farm in Spain which was affected by a PRRSV outbreak with the highly pathogenic and aggressive Rosalia PRRSV strain. The Rosalia PRRSV variant has caused lots of problems in pig farms in Spain since 2021, leading to an increase in reproductive problems (sows) and a higher incidence of respiratory infections combined with higher mortality rates (piglets, growers, finishers). The animals on the Spanish farm were also affected by G. parasuis and M. hyopneumoniae. 

Tilmovet® Premix (16 mg/kg bodyweight) was administered to weaned piglets during the first 21 days of the trial. At the outset of the trial, the pigs showed a high level of PRRSV infection with 51% and 46% PRRSV PCR-positive pigs in the control and the Tilmovet® medicated groups, respectively.

To evaluate the effect of Tilmovet® feed medication, three subgroups were created according to the qPCR result (Ct value) of each pig at the beginning of the study. The three subgroups comprised: 

• Pigs that were negative to qPCR at the start of the study (Ct value >40)
• Pigs with a low viral load at the start of the study (Ct value between 30-40)
• Pigs with a high viral load at the start of the study (Ct value <30)

In pigs with a negative PCR result at 3 weeks of age, Tilmovet® feed medication resulted in a 26% reduction in PRRS infection at 8 weeks of age, and a 23% reduction at 10 weeks of age after an infection peak at 6 weeks of age. In non-medicated pigs (the control group), the percentage of positive pigs increased by 8% at 8 weeks of age and by 5% at 10 weeks of age as indicated in Figure 3.

Figure 3. Evaluation of the viral load in PRRSV-negative pigs at the start of the study over the duration of the trial

In the low-level PCR-positive pigs, Tilmovet® medication resulted in a greater reduction in the infection levels, reducing the infection by 30% at 6 weeks of age and by 40% at 8 weeks of age versus the control group in which the infection level decreased by 15% at 6 weeks of age and by 8% at 8 weeks of age (Figure 4). 

Figure 4. Evaluation of the viral load in low-positive pigs at the start of the study over the duration of the trial

In the high-level PCR-positive piglet group, a higher infection reduction by 18% at 6 weeks of age and 40% at 8 weeks of age) was observed in the Tilmovet® group versus the control group with only an 8% reduction at 6 weeks of age and a 29% reduction at 8 weeks of age (Figure 5).

Figure 5. Evaluation of the viral load of high-positive pigs at the start of the study over the duration of the trial

A higher survival rate at the end of the study was determined in the Tilmovet® group (82%) in comparison to the control group (78%, Figure 6). The relatively low survival rates in both groups were based on the highly pathogenic PRRSV strain and the first disease outbreak caused by this strain on the Spanish farm.

Figure 6. Survival rate 3 to 10 weeks of age

A higher daily weigh gain during the period of the study was seen in the pigs that received Tilmovet® feed medication compared to the control group (Table 1). 

Table 1. Body weight and average daily gain (ADG) of pigs in the two treatment groups

The effect of Tilmovet® on PRRS clinical expression in viraemia situations

The use of Tilmovet® feed medication as an early intervention strategy post weaning was proven successful in the case of the PRRSV viraemia situation caused by the highly pathogenic Rosalia variant.

Reducing the presence of the PRRS virus helps to: 

• Stabilize PRRSV infection situations
• Prevent interactions between PRRSV and respiratory bacteria pathogens
• Prevent PRDC and other complex respiratory diseases
• Reduce mortality in growers and finishers
• Minimize spread of the virus both inside the unit and to other pig farms

Tilmovet® feed medication protocols represent an important element of a PRRS chemotherapy approach.

References are available on request