Bluetongue, a disease contracted by wild and domestic ruminants, is a notifiable disease in South Africa. “It is caused by an Orbivirus and is spread by biting midges,” explains Dr Lindsay Parvess, CCS Veterinarian with the Gauteng Department of Agriculture. “The disease often occurs from late summer to early autumn when biting midges are common. These midges are more common around bodies of water such as marshes and dams. Animals that move and stay in these areas will have a higher risk of contracting the disease.
“Bluetongue affects mostly sheep and goats, and occasionally cattle. The disease cannot be spread directly from one animal to another, only through biting midges. Bear in mind that sheep, goats and cattle act as reservoirs for the disease. This means that they harbour the virus, which is then spread from one animal to another by the midges.”
Prevention is better than no cure
As there is no cure for the disease and the treatment of symptoms is often the only option, prevention and control is crucial. “The best control method is vaccination. Vaccinate animals before late summer to protect them when risk of the disease is high. Check the vaccination schedule of the bluetongue vaccine.
“It is important not to use a live virus vaccine on pregnant animals since it can cause abortions and foetal malformations. It is recommended to vaccinate ewes at six weeks and again at nine weeks before the breeding season.” Dr Parvess warns never to vaccinate during an outbreak or during peak disease season as the vaccination can potentiate the situation.
Minimising vector access to livestock is crucial in controlling the disease. A few basic steps can have a massive impact. “Keep your animals away from bodies of water during the bluetongue season and in the late afternoon when biting midges are most active.” In heavily infested areas, use dips or sprays to prevent animals from being bitten by midges.
Detect and control
Keep infected animals separate in order to limit the spread of the disease. “Infected animals become very lethargic, stop eating and have a very high temperature and swelling of the tongue and lips. The tongue may eventually stick out and turn blue, hence the name bluetongue.”
Other signs of infection include salivation, nasal discharge and discharge from the eyes, as well as ulceration in the mouth, lips and ears. “Animals will be reluctant to walk as painful feet are another symptom. There will be redness between the juncture of the skin and the coronary band (top of the hoof), and in severe cases the claws will come off.” If an animal is pregnant at the time of infection, it may abort or give birth to a deformed lamb. If bluetongue does occur, the first step is to contact your local veterinarian, who will report the occurrence of the disease to the state veterinarian. As mentioned, there is no cure, but you can do a lot to make animals comfortable and treat the symptoms.
“Provide soft bedding to prevent pressure sores. Keep animals warm and always provide easy access to palatable feed, such as pellets wetted with warm water, and clean water. Wash the ulcers with salt water to prevent secondary infection.” – Marike Brits, Stockfarm
This article is the fourth in a series of informative animal health articles. The series goes hand in hand with the #VideoVet video series that can be viewed on www.agriorbit.com. Watch the video below.
For more information, contact your MSD Animal Health representative or phone 011 923 9300. (ZA/ORUM/0218/0003e)
Thank you for the support of several role-players in creating this series: the Gauteng Department of Agriculture and Rural Development, Dr Gillian Declercq and the CCS veterinarians (Dr Lindsay Parvess and Dr Heidi Kuhn), MSD Animal Health, as well as Kenneth Ndlovu and the Amogelang team for their assistance and animals for demonstration.