By Roelof Bezuidenhout
Vets say that many diseases and health issues could be prevented if farmers took biosecurity more seriously. It’s no good worrying about foot-and-mouth or Rift Valley while it’s making the headlines, and then become complacent once the threat appears to have subsided. The resurgence of Rift Valley fever illustrates how quickly things can go wrong – after decades without a major outbreak, interest in prevention waned, and now the consequences are clear. Biosecurity is a full-time responsibility, protecting not only your own livelihood but also your neighbours and consumers.
Various threats
Livestock farmers must maintain their flocks’ immunity at optimal levels to protect against insect-borne diseases. This involves vaccination, ensuring proper nutrition, minimising parasite loads that can weaken immunity, and selecting animals with natural disease resistance. Prolonged stress can also reduce immunity.
Preventing insect-transmitted diseases is challenging, as many insects, particularly those carried by the wind, travel long distances. The most common insect-borne diseases, including blue tongue, Rift Valley fever and Wesselsbron disease, can be controlled through vaccination. In more intensive systems, fly populations – especially nuisance flies and blowflies – can be managed using baited flytraps.
To reduce the risk of disease transmission, ectoparasiticides can be used. For example, applying insecticides to the faces of animals may help prevent eye infections. In intensive systems, the risk of ticks entering the property can be reduced by spraying insecticides around the perimeter, creating vegetation-free buffer zones, using fowl to patrol the area, and even deploying pheromone-treated bait animals to trap ticks.
New species or strains of internal parasites may also be introduced to a farm. Stud animals often bring their own parasites with them. While it’s nearly impossible to keep ticks entirely off a farm, regular chemical control is essential, and it’s crucial to eradicate parasites on any animals introduced to the farm.
Genetic diseases can be introduced to a flock through recessive genes, often becoming apparent only after the first offspring are born. More subtle genetic issues affecting traits like disease resistance, parasite tolerance, reproduction, mothering ability and environmental adaptation may take longer to identify.
Key aspects to monitor
• Introduction of new animals: It’s well known that animals can contract diseases from other livestock. Taking animals to shows and bringing them back, or introducing new breeding stock such as rams or bulls, can introduce diseases and parasites to the farm. That’s why any animal reintroduced to a farm should be treated as if it came from an unknown source and be quarantined and monitored for a period to prevent potential outbreaks. And to be safe, only buy animals from farms with strong biosecurity practices and sound health management.
• Waterways: Biosecurity risks extend to waterways. Flash floods can carry infectious materials, such as droppings, from one farm to another, spreading disease. Several years ago, floods washed lucerne bales contaminated with red water ticks downstream, resulting in cattle losses along the banks of the Orange River in the Karoo – an area where red water is not typically found. To minimise risk, livestock should be kept out of camps near water courses during wet seasons.
• Shearing time: Diseases can be introduced to a farm by shearers and their vehicles. For example, quarter evil, caused by the bacterium Clostridium chauvoei, led to the death of 200 pregnant ewes (from a flock of 2 000) after a shearing team arrived from another farm where they had slaughtered and eaten a cow that had died of the disease.
• Contaminated feed: All feed should be carefully examined upon arrival on the farm. It is safer to buy from a trusted supplier rather than shopping around for feed. Contaminated bales may carry tick larvae, and dead birds or small mammals in feed can cause botulism.
• Migrating birds: Diseases can be introduced by flocks by birds. Foot rot, for example, often appears on Karoo farms shortly after the first storks arrive from Europe in summer, suggesting these birds may be passive carriers. Farmers also suspect that lumpy wool disease is spread by birds, particularly cattle egrets that perch on sheep. Although it’s impossible to prevent birds from coming onto your farm – and they play an important role in pest control – flock managers can mitigate risks by dipping livestock in zinc sulphate after the birds’ arrival.
• Predators: Carnivores can spread disease both through bite wounds and by serving as intermediate hosts for parasites. Caracal (rooikat) are known carriers of the paralysis tick, and jackal host tapeworms and the parasite responsible for bovine cerebral theileriosis (commonly known as turning sickness, or draaisiekte). The introduction of rabies on a small-stock farm is usually associated with dogs, cats, jackal or mongoose.
• Fences and gates: Poor fencing is a major problem, particularly in the case of sheep scab, red lice and other parasites that can be picked up along farm boundaries. Stray animals can introduce several diseases. And outsiders crossing your farm on foot is another problem – foot rot is just one disease that can be spread by humans.
Essential biosecurity measures
The risk of diseases and parasites can be minimised by implementing internal biosecurity measures alongside external ones:
- Animals that may carry infectious agents or parasites should be isolated, treated or culled. Weak and debilitated animals are particularly vulnerable to infection and can become sources of contamination. Hospital camps, however, can be a hidden risk, as they often harbour infections and parasites. These camps are sometimes used for healthy animals out of convenience, only for them to be reintroduced to the flock. Common examples include newly bought rams, ewes carrying triplets or more, and injured animals.
- Handling facilities and feedlots should be maintained to prevent the buildup of organic matter, parasites and infectious agents. Lambing pens can also pose a risk in this regard.
- Autopsies should be conducted in a secure area, and hazardous materials must be disposed of properly to prevent the spread of disease and parasites.
- Infectious diseases can spread through animal handling and treatment. Abscesses should be lanced in a designated area that can be thoroughly cleaned, with runoff water contained and treated to kill bacteria, preventing transmission by insects or other means.
- Needles and surgical instruments used for vaccines, medications or nutritional supplements, as well as tag applicators, tattooing equipment and tail-docking tools, can act as disease vectors. Needles should be disposed of after use, and instruments should be sterilised between applications to avoid the transmission of infections.
Quarantine tips
- Dip all new animals upon arrival, but ideally before they are moved from the source.
- Administer a drench if necessary, and assess the response after 10 days.
- Vaccinate the animals as needed, at least against diseases that commonly occur on your farm.
- Footbath animals with a zinc sulphate solution, adding a small amount of soap.
 | Roelof Bezuidenhout is a fourth-generation wool, mohair, mutton and game farmer and freelance journalist. Attended Free State University, majoring in animal husbandry and pasture science. Other interests include golf, photography and geology. |
