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Three Day Sickness Warning

Hunter and Mid Coast cattle producers are being asked to consider their management approach to Three Day Sickness, this spring. Hunter Local Land Services animal health surveillance activities has found our region’s herds have had very little exposure to the virus over the previous two hot dry summers.
District Vet Dr Lyndell Stone said Three Day Sickness, also known as Bovine Ephemeral Fever (BEF), is a viral disease of cattle transmitted by mosquitos and midges.
“The low exposure over the last two summers creates infection risks for mature, pregnant, lactating and finished cattle and these animals may benefit this year, more than any other year, from Vaccine protection during Spring before mosquitos potentially arrive over summer carrying the virus,” said Dr Lyndell Stone.
“In our region, particularly, closer to the coast, it normally arrives in mid to late summer, only occasionally skipping a year.
“Such regular virus appearance, in the past, means each year’s crop of weaners are generally infected whilst young and then have good lifelong protection against the inflammatory effects of the virus.”
However, the very minimal distribution of the virus over the previous two years could mean our herd is more severely affected when the virus does arrive, as herds have a higher proportion of non-immune stock. In addition, when cattle are older, heavier, pregnant and lactating when first infected they are generally more severely affected than young cattle. In this situation, vaccination by November may be an important part of on farm cattle management.
“Cattle when first infected, develop strong long-term immunity against further infection,” said Dr Stone.
“Young animals generally suffer less severe illness, but the impact of the virus when older animals are first infected can be more severe.
“When this situation has occurred in the past, producers have presumed that they are seeing a more severe variant of the virus, however, the virus is actually very stable and hasn’t changed over the years.”
The virus causes lameness and fever. Cattle can become recumbent, and it can affect bull fertility and cause abortion in breeders. There is also a considerable management burden looking after recumbent cattle.
Hunter Local Land Services monitors the distribution of this and other mosquito and midge borne viruses through sentinel herds at Taree, Maitland, Singleton and Scone.
Monthly blood sampling results of the sentinel herds confirm this situation. The dry weather seems to have changed the normal seasonal and regular infection pattern, so that herds in the Mid Coast and Hunter farming areas have missed their normal exposure to the virus two years running.
The District Vet team is advising producers may need to consider vaccinating their older and/or higher value stock towards the end of this year against a 2020 BEF season.
The vaccine is available from private veterinary practitioners.