Porcine reproductive and respiratory syndrome (PRRS) caused by the PRRS virus (PRRSV, Figure 1) is recognized as the most endemic and economically important disease in swine worldwide.
Figure 1. The PRRS virus - an enveloped RNA virus
Any effort directed towards the control of PRRS will have an important impact on the health status of pigs herds and on the profitability of the swine industry.
Vaccines cannot eliminate the PRRS virus. As a result of ongoing mutation and recombination processes of PRRSV in the field, highly pathogenic virus variants are created, examples of which can be found in Spain (Rosalia), in China and elsewhere.
The Rosalia PRRSV variant present in Europe is characterized by a high spreading potential inside and outside farms causing higher mortality rates among piglets and finishers than earlier PRRSV varieties (PRRSV Type 1, PRRSV Type 2).
The use of products with anti-viral activity during PRRS infection is considered an effective measure to reduce the severity of the clinical effects.
Tilmovet® 5-day medication programme (15mg/kg body weight, 3-time administration, 14-day non-treatment period in between) benefits PRRS-positive herds under field conditions by:
Activity and antiviral effects of Tilmovet®
Tilmovet® (tilmicosin) provides an antimicrobial effect against different bacteria and accumulates rapidly in macrophages and neutrophils, the location of PRRS virus replication. The 2-6 times higher intracellular accumulation of tilmicosin in comparison to other macrolide antibiotics is the key factor for its high antimicrobial and antiviral effect in pigs.
Tilmovet® administration in PRRSV-viraemic pigs post-weaning
The antiviral activity of Tilmovet® Oral Solution in PRRSV viraemic pigs was determined in a field study in Spain.
The study was conducted in a transition farm affected by a PRRSV outbreak with the highly pathogenic Rosalia PRRSV strain. The animals on the farm were also affected by G. parasuis and M. hyopneumoniae post-weaning.
Tilmovet® Oral Solution was used in a 5-day medication programme 3 times (15 mg/kg body weight) with a treatment stop of 14 days in between treatments.
At the start of the study 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.
For evaluation of the effect of Tilmovet® water medication, three subgroups were created according to the qPCR results (Ct value) of each pig at the start of the study. The three subgroups comprised:
In the pigs with a PCR-negative result at the start of the study (3 weeks of age), Tilmovet® water medication reduced the PRRS infection by 8% at 8 weeks of age and by 14% at 10 weeks of age after the infection peak at 6 weeks of age (Figure 2). In the non-medicated pigs, the percentage of positive pigs increased by 8% at 8 weeks of age and by 5% at 10 weeks of age.
Figure 2. Evaluation of the viral load of PRRSV-negative pigs at the start of the study for the duration of the trial
Tilmovet® medication in the low-level PCR-positive pigs at the beginning of the study resulted in a higher infection reduction of 25% at 6 weeks of age and a 47% reduction at 8 weeks of age versus the control group, in which the viraemia decreased by 15% at 6 weeks of age and 8% at 8 weeks of age. The results are shown in Figure 3.
Figure 3. Evaluation of the viral load of low positive pigs at the start of the study for the duration of the trial
In the high level PCR-positive pigs at the beginning of the study, a similar infection reduction of 25% at 8 weeks of age and 40% at 10 weeks of age in the Tilmovet® group was observed versus the control group with a 29% reduction at 8 weeks of age and a 40% reduction at 10 weeks of age (Figure 4).
Figure 4. Evaluation of the viral load of high positive pigs at the start of the study for the duration of the trial
A higher survival rate at the end of the study (Figure 5) was seen in the Tilmovet® group (83%) in comparison to the control group (78%). 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 5. Survival rate 3 to 10 weeks of age
A higher daily weight gain was seen in pigs that received the Tilmovet® water medication in comparison to the control group (Table 1).
Table 1. Body weight and average daily gain (ADG) of pigs in the two treatment groups
Therapeutic approach with Tilmovet® in PRRSV viraemia situations
The use of Tilmovet® water medication has been explored in the case of a PRRSV viraemia situation in a swine herd post-weaning. Using Tilmovet® water medication was an excellent strategy to reduce the virus load and spreading during the PRRS infection.
Reducing the presence of the PRRS virus helps to:
Tilmovet® water medication protocols represent an important element of a PRRS chemotherapy approach.