There have been numerous outbreaks of lumpy skin disease (LSD) recently, especially in the Eastern Cape where alternating wet and then sunny weather has probably encouraged the biting insect vectors of the virus.
Although LSD usually infects herds during the wet autumn and summer months, it may also strike during the dry season. Recent research has shown that certain ticks can transmit the disease. This suggests a higher likelihood of infection outside the expected seasons, especially where ticks survive throughout the warmer winter.
Infection with the virus has a profound effect on animal productivity – dramatically reducing milk production, causing abortions and other fertility problems, and damaging hides. The LSD virus destroys cells in the skin and mucous membranes, spreading from the saliva and skin lesions of infected animals by direct contact, and through communal water and feed troughs.
SYMPTOMS OF LSD
To see an animal suffering from LSD is something no stockman would wish to witness. The virus incubates for about seven days before a fever develops, which can last for up to 14 days. The obvious symptoms are a nasal discharge, increased salivation, reduced appetite, a high temperature, the development of many firm and painful lumps in the skin, and lesions in the mucous membranes of the mouth and the nose.
Enlarged lymph nodes are common at the onset of the disease. Affected animals often show swollen legs, udder and brisket, and tend to be reluctant to move. Cows suffering from LSD develop swollen legs. Pneumonia and/or coughing is a common secondary complication and lesions in the lungs and trachea may become life-threatening. Painful mouth ulcers make it difficult for animals to feed, which leads to
weight loss. The fever that comes at the onset of the disease may cause abortions in pregnant animals. Bulls infected with LSD may permanently or temporarily become infertile, and the virus may be shed in their semen. Although bulls are known to recover from LSD, their full recovery is never guaranteed.
Cattle with LSD can become extremely sick and in acute cases they may die. Herd mortality rates vary from 3% to 40%. Infected animals need good nursing, antibiotics and corticosteroids if they are to have a chance of making a recovery.
The recent foot-and-mouth outbreak with its associated economic hardship makes it vital that we look at ways of helping livestock farmers avoid losses. This refers specifically to losses that can be prevented with a minimal investment of as little as R15 per animal per year to protect the herd against disease. Groups of farmers with small herds could consider inoculating animals at a communal point to share the vaccine cost.
LSD mortalities can cause the loss of valuable genetics that farmers have worked hard to build up or to bring into their herds. Breeding opportunities may be lost as sick bulls may only recover when the breeding season has already passed. All these losses have a direct and indirect financial impact on the farmer. LSD can become a trade barrier across national and international borders and even at a local level as visibly sick animals will not be considered for purchase.
Vaccination is the only way to control and prevent LSD and vets consider it a critical part of the annual herd health programme. Vaccinating an animal activates the immune system, which generates a protective response when the animal is exposed to the virus. All animals from six months upwards, including pregnant cows, should be inoculated against LSD every year in spring.
There are some highly effective vaccines available in the country, including the OBP Neeth- ling strain vaccine that has been on the market for over half a century. The vaccines are freeze-dried and come with a sterile diluent, which means the powder and the diluent must be mixed as per included instructions.
During vaccination use a separate needle for each animal – especially if you are inoculating during an outbreak because shared needles can spread the disease. Immunity develops 10 days after vaccination and the animal is fully protected after about three weeks.
The LSD vaccines available in South Africa are live vaccines and may be inactivated if disinfectants and methylated spirits are used to clean the skin or to clean syringes and needles. Re-usable needles should be boiled in water for about 15 minutes and then cooled down before use.
A reliable cold chain from the point of purchase to the injection of the vaccine is essential. The easiest way to keep the cold chain intact in the field is to store the vaccine in a small cooler box with ice packs. The vaccine is highly sensitive to inactivation by sunlight and the cooler box does double duty helping to keep it at the right temperature and out of sunlight.
Insect control through dips and other approved external parasite control remedies help manage infection pressure.
It is worth mentioning that LSD vaccination may have some side effects that seem to be more noticeable in young animals or animals who may not have been vaccinated before. Small lumps at the injection site and elevated temperatures may also occur post-vaccination. Milk production in dairy cows may drop post vaccination but will soon recover in line with their lactation cycles.
While it is generally accepted that antibiotics do not kill viruses, they are often a valuable intervention to manage secondary infections. The use of corticosteroids is also indicated in LSD treatment. Other supportive intervention includes providing milled feed to help animals reluctant to feed due to mouth ulcers from the disease. It is a good idea to isolate infected animals, if this is possible, to stop the spread of the virus through water sources contaminated by infected saliva.
Speak to your local veterinarian or animal health technician regarding basic vaccination programmes that can help make a difference to your operation. Please feel free to contact OBP on (012) 522 1500 or write to firstname.lastname@example.org for any other livestock health enquiries.