Bovine Ephemeral Fever (Three Day Sickness)

Bonnie Skinner, Manager Biosecurity & Extension, New South Wales

What is it?

Bovine Ephemeral Fever (BEF), commonly known as “three day sickness”, is an insect-borne virus (arbovirus) that affects cattle and buffalo.

Where is it?

The disease is endemic to Africa, Asia, the Middle East and Australia. BEF was first reported in Australia in 1936 after an outbreak in the Northern Territory, which spread into the Kimberley region of Western Australia, into Queensland and southerly through the eastern states down to Victoria[1]. Episodic outbreaks typically start with the beginning of the wet season in the Northern Territory and move easterly and southerly through Queensland and New South Wales and occasionally to Victoria (December to April). Occasionally in Northern Australia cases are reported in the winter and spring. The spread of BEF is largely dependent on insect populations, rainfall events and wind direction. The National Arbovirus Monitoring Program (NAMP) monitors the distribution of BEF in Australia by blood sampling cattle and trapping of insects that spread the virus.

Figure 1: Distribution of bovine ephemeral fever virus in Australia, 2014-2015 to 2016-2017[2].

http://www.bom.gov.au/climate/averages/climatology/gridded-data-info/metadata/md_koppen_classification.shtml

How is it spread to cattle?

BEF is spread by biting insects; primarily mosquitoes and biting midges (Culicoides species). The virus cannot be transmitted directly from one animal to another (by close contact, aerosol droplets or body secretions) – there must be a biting insect present to transmit the virus.

What are the signs?

Clinical signs in cattle typically last a few days, which is why BEF is known as “three day sickness”. Figure 2 illustrates the clinical signs associated with BEF. The first signs seen are usually a high fever of 40-41°C which persists for 1-2 days. This may be accompanied by shivering, head held low with watery eyes, runny nose, and drooling saliva. In dairy cows most noticeably milk production will drop by up to 50% or more[3]. As the virus progresses into the second day there is often general stiffness, with lameness in one or more legs and swelling of the joints. Some cattle will lay down (often those in good or fat condition) and are reluctant to move or get back up. By day three animals are willing to eat and drink again, though may remain lame for another few days.

Figure 2: Clinical signs of Bovine Ephemeral Fever in cattle

Production impacts

While the disease does not have a high mortality rate, the number of animals that are affected by the disease during an outbreak varies depending on the number of susceptible cattle and how widespread the disease is as a result of insect distribution. Past outbreaks demonstrate morbidity rates of 30-35% and as much as 100% in severe outbreaks[4]. Deaths from BEF are uncommon (at around 1% of the herd) and commonly result from euthanizing animals who are unable to get up[5]. Temporary infertility up to 6 months can develop in bulls and abortions can occur in late pregnancy cows due to the high fever during the virus[6]. Cows in late lactation may not recover until the following lactation period[7], affecting calf performance and/or milk yields. Cattle being prepared for market and musters on extensive properties can be delayed, and permanent weight loss in affected animals is reported to average 10kg[8].

Diagnosis and treatment

A veterinarian can diagnose BEF based on the presence of clinical signs and the spread of disease through a herd and/or a blood sample. BEF can be confirmed by culture from a blood test taken during the fever stages of the disease, and by PCR where two samples are collected, one in the initial days of clinical disease and another 14 days later[9]. General treatment involves providing shade, water and food to the affected animals as well as non-steroidal anti-inflammatories (NSAIDs). Animals that are lying down should be encouraged to stand and may need to be rolled several times a day if they are in good to fat condition.

Susceptibility and prevention

Cattle who are infected with the virus once often develop lifetime immunity. Young growing calves (over six months of age) or cattle recently introduced into endemic areas are the most susceptible to disease, as well as cattle born during a drought when insects are unable to breed. These cattle are not exposed to the virus as younger animals and so are highly susceptible when the drought breaks and insect numbers rapidly increase.

A vaccine is available by prescription from a veterinarian for cattle from six months of age and is commenced with the first dose given at the start of summer, and a second dose four weeks later. This is then maintained with an annual booster given 8-10 weeks before the start of BEF season. Deciding on vaccination will depend on risk and history of outbreak in your area, number and class of livestock to vaccinate. Producers should consider the potential cost of treating sick animals compared to vaccination.  Contact your veterinarian to discuss your vaccination strategy.

For further information about the BEF risk to your herd or the vaccine, contact your local private or government veterinarian.

 

[1] Seddon HR. (1938). The spread of ephemeral fever (three-day sickness) in Australia 1936-37. Australian Veterinary Journal (14), 90–101.

[2]Adapted from National Arbovirus Monitoring Program Annual Report 2016-17 https://www.animalhealthaustralia.com.au/our-publications/namp-report/

[3] Department of Primary Industries NSW (2016). Bovine ephemeral fever: Three Day Sickness (No. 1423). Primefacts. Retrieved from: https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0011/679106/bovine-ephemeral-fever-three-day-sickness.pdf

[4] McGown, P., Entwistle, K.W., O’Rourke, P.K., Perkins, N. (2010). Economic impact of bovine ephemeral fever virus in extensive northern beef herds. Projects AHW.020 & AHW.091. Final report prepared for Meat & Livestock Australia, Sydney. Retrieved from: https://www.mla.com.au/research-and-development/search-rd-reports/final-report-details/Animal-Health-and-Biosecurity/Economic-impact-of-Bovine-Ephemeral-Fever-Virus-in-Extensive-Northern-Beef-Herds-Phase-1-And-2/122

[5] Department of Primary Industries NSW (2016). Bovine ephemeral fever: Three Day Sickness (No. 1423). Primefacts. Retrieved from: https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0011/679106/bovine-ephemeral-fever-three-day-sickness.pdf

[6] St George, T.D. (1989). An overview of Arboviruses affecting domestic animals in Australia. Australian Veterinary Journal, (66) 12, 393 – 395

[7] Walker P.J. (2005) Bovine Ephemeral Fever in Australia and the World. In: Fu Z.F. (eds) The World of Rhabdoviruses. Current Topics in Microbiology and Immunology, vol 292. Springer, Berlin, Heidelberg.

[8] Walker, P.J., Cybinski D.H., (1989). Bovine ephemeral fever and rhabdoviruses endemic to Australia. Australian Veterinary Journal, (66) 398-400.

[9] Department of Primary Industries NSW (2016). Bovine ephemeral fever: Three Day Sickness (No. 1423). Primefacts. Retrieved from: https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0011/679106/bovine-ephemeral-fever-three-day-sickness.pdf