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- The wet conditions, says Dr Dedré Nel of the Weltevrede Animal Clinic in Excelsior in the Free State, are expected to exacerbate the possibility of insect-borne diseases such as three-day stiffsickness (TDS) in beef and dairy cattle.
- TDS is caused by a virus that is transmitted to cattle by Anopheles and Culex spp mosquitoes, as well as Culicoides spp mosquitoes. Outbreaks typically occur when insect activity increases.
- The disease is characterised by sudden onset that can progress to a more severe level very quickly, with animals seemingly recovering within three days (hence the name three-day stiffsickness).
- The best way of preventing and controlling TDS is through immunisation of the host population, as well as environmental control of vectors.
- It is recommended that unvaccinated cattle be immunised when they are six months or older.
Excellent rainfall conditions are predicted to last until midsummer in South Africa’s summer rainfall regions. While this is good news, it is likely to lead to an increase in livestock diseases. The wet conditions, says Dr Dedré Nel of the Weltevrede Animal Clinic in Excelsior in the Free State, are expected to exacerbate the possibility of insect-borne diseases such as three-day stiffsickness (TDS) in beef and dairy cattle.
TDS is caused by a virus that is transmitted to cattle by Anopheles and Culex spp mosquitoes, as well as Culicoides spp mosquitoes. Outbreaks typically occur when insect activity increases.
TDS, says Dr Nel, is prevalent across South Africa, usually during summer and autumn. Countrywide outbreaks have increased sharply since 2020, leading to large-scale losses. These outbreaks can be attributed to, among other things, above-average rainfall and animals not being vaccinated. The latter, she believes, was due to a shortage of vaccines, whereas the disease did not pose a significant problem in previous years.
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Economic impact
Research published in the Veterinary Research journal shows that the mortality rate of TDS is usually low, whereas infection and morbidity rates during outbreaks often are very high. This has serious economic consequences for producers, especially in respect of dairy cows producing less milk and poor condition among beef cattle. According to this research, a study showed that TDS can result in an estimated average net loss of 175,9kg of milk per cow per lactation.
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Symptoms and susceptibility
According to an information piece by Drs Vorster and Mapham from Vetdiagnostic and the Veterinary House Hospital in Pietermaritzburg respectively, this disease is characterised by sudden onset that can progress to a more severe level very quickly, with animals seemingly recovering within three days (hence the name three-day stiffsickness).
Typical clinical symptoms include the sudden onset of a fever as high as 41°C. The animal’s body and legs become stiff and painful. It may also experience a loss of appetite, increased salivation, nasal discharge and watery eyes. Swollen joints, muscle spasms, as well as an accelerated pulse and respiratory rate can also occur. Animals are not able to stand up and have trouble swallowing.
All age groups are susceptible to this virus, explains Dr Nel. Animals experiencing stress, such as lactating cows and fast-growing animals, are typically more severely affected. Moreover, the size and weight of the animal play a role in the recovery process. “We’ve seen that bulls have a harder time recovering from the virus, because of their weight and muscle damage brought on by the constant immobility when lying down.” She recommends that such animals be turned, and their legs moved regularly to boost blood circulation and prevent muscle damage.
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Act preventively
The best way of preventing and controlling TDS is through immunisation of the host population, as well as environmental control of vectors. Dairy cattle, feedlot animals, valuable breeding animals and calves from unvaccinated dams must be vaccinated.
It is also recommended that unvaccinated cattle be immunised when they are six months or older. A booster dose must be given four weeks later. Mature animals can be injected regardless of the stage of gestation or lactation. Annual vaccination is also recommended, and animals should ideally be vaccinated in late winter or early spring. During seasons with high rainfall, this vaccine must be used in combination with an insect control programme aimed at combatting midges and mosquitoes. – Christal-Lize Muller, Stockfarm
For more information or a list of references, send an email to Dr Dedré Nel at dedre.nel24@gmail.com.
