The Fight Against Pestivirus: Strategies for Cattle Health Improvement

Wagyu cattle on AA Co’s Wylarah Station near Surat

In 2020, when weaners at the Australian Agricultural Company’s Wylarah property near Surat exhibited respiratory symptoms, a significant concern arose regarding their health. Matias Suarez, the Breeding and Genetics Regional Manager, found signs indicative of pestivirus infection—potentially responsible for Bovine Respiratory Disease (BRD) in weaners.

To confirm the presence of pestivirus, the team conducted tests to identify any stock that were persistently infected (PI). The results revealed a high incidence of PIs, prompting immediate actions: a whole-herd Pestigard vaccination program and a continuous weaner PI testing initiative.

Matias Suarez

Since the implementation of these measures, AA Co has reported a substantial decline in the annual cases of calves testing positive for the disease, along with a significant reduction in BRD occurrences among weaners.

Disease Detection

According to Dr. Michael McGowan, a Professor of Veterinary Science at the University of Queensland, identifying pestivirus within a herd can be challenging due to its varied manifestations. Symptoms can range from decreased pregnancy rates to higher loss rates from pregnancy to weaning.

Common signs include:

• Stillbirths
• Poor suckling response
• Calves showing signs of incoordination or eye malformations
• Arthrogryposis (joints fixed in abnormal positions)
• Mouth and tongue ulceration
• Diarrhea
• Wasting
• Pneumonia in recently weaned calves or feedlot cattle

Testing is vital for confirming pestivirus as the cause of observed symptoms, enabling effective management and control strategies.

Reducing Transmission

Due to its highly contagious nature, Mr. Suarez emphasized the importance of reducing pestivirus transmission. Research indicates that placing a persistently infected animal in close quarters with susceptible cattle can result in a 60% infection rate within 24 hours.

The company took immediate action once pestivirus was confirmed, initiating a comprehensive testing program for bull breeding units, which are transported annually across northern Australia. They also began a vaccination program for all breeding females, aimed at minimizing the risk of producing further PI calves.

Long-term Management

Dr. McGowan views vaccination as a protective measure akin to insurance. Introduced in 2004, studies have shown high effectiveness—between 80% and 85%—in halting dam-to-progeny transmission cycles.

For commercial herds, starting with a heifer-only vaccination program is advisable, as this group is typically more vulnerable to pestivirus outbreaks due to limited natural immunity.

Avoiding Risks

Both experts caution against risky alternatives aimed at saving costs, such as intentionally introducing a PI into the herd to foster natural immunity. This strategy could severely undermine herd productivity. As Mr. Suarez succinctly put it, “At the end of the day, you simply cannot afford to not vaccinate.”

Source: MLA