IBR expert says cases can occur in closed herds

IBR cases can occur in closed herds and can spread widely within herds without severe clinical signs in most animals, according to Isabelle Truyers of Zoetis.

Truyers joined Zoetis Ireland earlier this year as an Area Veterinary Manager (Livestock).

She previously worked in mixed practice in Northern-Ireland, completed a farm animal residency programme at the University of Glasgow and, for the past 5 years, was employed as a Lecturer in Farm Animal Practice at the University of Edinburgh.

She is a European Veterinary Specialist in Bovine Health Management.

In May 2012 Isabelle was involved in an outbreak of IBR in a dairy herd whilst she was working in Edinburgh.

The disease was identified in the herd following the death of a first lactation heifer with respiratory problems.

The herd had discontinued IBR vaccination five years previously, but had very good biosecurity and composite milk samples of first lactation heifers consistently tested IBR negative in the past few years (last test March 2012).

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There had been no other classical signs of IBR up until the death of this heifer but the herd had experienced poorer than average fertility in recent months.

In June 2012 sampling confirmed that 99% of the milking cows had been infected with IBR and over two thirds of the in-calf heifers also tested positive.

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At this point, the herd was vaccinated for IBR straight away using the Rispoval IBR-Marker vaccines to control clinical disease and reduce shedding from the IBR carriers.

Following Rispoval IBR vaccination the conception rate in the herd increased from 26%, during the period when IBR was actively circulating, to 42% without any other changes in management.

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“The Rispoval IBR vaccination programme is very straight forward and reliable. We gave a single dose of Rispoval IBR-Marker live followed by a single dose of Rispoval IBR-Marker inactivated within six months. After that animals only needed a single booster of Rispoval IBR-Marker inactivated once a year.

“Rispoval IBR-Marker vaccines have since protected the herd from further clinical disease and yearly blood sampling has demonstrated that Rispoval IBR-Marker vaccines have also prevented new infections from occurring.

“IBR is a very infectious and economically important disease in cattle caused by bovine herpes virus,” she said.

What she learned from this case study was that:

1. IBR breakdowns can occur in closed herds, possibly due to recrudescence (shedding of the virus from IBR carriers) from older IBR carrier cows.

  • Dairy herds with endemic IBR infections are likely to see recrudescence of IBR virus at some stage.
  • Young stock reared without direct contact with the adult cows appeared to remain free of IBR infection in this herd.
  • Groups of naive, unvaccinated replacement heifers are at high risk of disease when they calve and are introduced into the main milking cow herd.
  • Therefore heifers should be vaccinated before the first breeding and, where possible, reared separately from the adult cows.

2. IBR virus spread widely within this milking herd without severe clinical signs in most animals. Poor fertility was noted and this may have been related.

  • The conception rate was 26% when IBR was active in the herd and increased to 42% following Rispoval IBR-Marker vaccination.
  • Only Rispoval IBR-Marker vaccines provide IBR abortion protection.

3. Vaccination with the Rispoval IBR-Marker live/inactivated programme has controlled clinical IBR disease to date and significantly reduced the risk of IBR virus shedding from carrier cows, allowing vaccinated heifers to remain free from IBR infection.

  • In this herd, eradication of IBR is a goal that could potentially be achieved within five years of control/vaccination being implemented.
  • In endemically infected herds the Rispoval IBR-Marker live/inactivated programme can provide good control of disease and potentially aid in eradication of the disease if that is the goal.
  • You can protect your herd by administering a primary course of two doses of Rispoval IBR-Marker vaccine followed by a Rispoval IBR-Marker yearly booster.