Dr Sello Maboe
When lumpy skin disease (LSD) outbreaks occur it suggests a lack of knowledge about primary animal health care. There may also be herds that are behind with vaccination, but in the case of LSD it’s never too late to vaccinate.
Vaccination is the best way to control the infection and transmission of LSD. It is an economically important notifiable disease of cattle in South Africa. It has impacts on animal welfare and the profitability of livestock farming.
WHAT ARE THE SYMPTOMS?
The disease is mostly self-descriptive. The typical skin lesions can range from a few to thousand and can be up to 5cm in diameter. These lumps or nodules occur on the face, neck, limbs, flanks, udder, teats, scrotum, perineum and on the mucous membranes of the mouth, nose, eyes and vulva.
Enlarged lymph nodes are common at the onset of the disease. Affected animals often have swollen legs and a reluctance to move. Nasal and eye discharges as well as excessive salivation are very common in infected animals. Secondary pneumonia, and/or coughing, is common in infected animals due to the infection of the respiratory tract and possibly worsened by other opportunistic pathogens.
There is often a drop in milk production (more noticeable in dairy animals) because of secondary mastitis that occurs following infection. Animals lose weight, often battling to eat because of painful mouth lesions.
HOW DOES LSD FURTHER AFFECT A CATTLE FARMER?
Apart from the known losses attributed to LSD, it is highly likely that animals will not be allowed near the saleyards. Biosecurity is justifiably getting more attention than it used to in that environment. The risk of disease transmission is highest in a place like the saleyard where animals congregate and are then transported to other places, including into neighbouring countries. Severely affected animals may die (up to 10%), especially those that encounter opportunistic infections while suffering from LSD. LSD losses are not restricted to mortalities. For example, when exposed raw lesions from the infection get secondary complications, the animal may need to be treated with antibiotics and anti-inflammatories. Blowfly fly strike is another possible complication.
HOW CAN I PREVENT OR MINIMISE LOSSES?
Registered, highly effective LSD vaccines are available, e.g. the OBP vaccine (Neethling strain). The control of insects around susceptible animals helps manage the infection pressure. This is mainly achieved using dips and other approved external parasite control remedies. The number of infected animals that suffer secondary lung infections highlights the importance of vaccinating for respiratory diseases, be they viral and/or bacterial, where possible.
THE BEST TIME TO INTERVENE?
The disease is commonly seen during the wet summer and autumn months when biting flies and mosquitoes are in abundance. Recent research has shown that certain ticks can also transmit LSD. This suggests a higher likelihood of discovering the disease outside the normal seasons we have gotten used to over the years. And it is particularly so in areas that experience warmer winters, where implicated ticks survive and show some activity, even if this is to a limited extent.
Cattle should be immunised way before the rainy season to allow them enough time to build up the required antibodies they need to overcome the disease challenge. This period is usually from August to September, especially in the summer rainfall areas. Most breeding cows that follow the summer rainfall pattern will be getting ready to calve around, or shortly after, that period. This means calves can get maternal antibodies from the colostrum of their vaccinated mothers. Unless it is specifically contra-indicated, most LSD vaccination programmes coincide with this period in the life of a breeding female animal.
TREATMENT
While it is generally accepted that antibiotics do not kill viruses, they are often a valuable intervention in the management of secondary infections. Other supportive intervention may also include providing milled feed to help animals that may be reluctant to feed due to mouth ulcers from the disease.
Dr Sello Maboe is the technical and marketing manager at Onderstepoort Biological Products. Email him at sello.maboe@obpvaccines.co.za
