Why should sheep be vaccinated?
In cases where there are risks of infection from certain contagious and fatal diseases, vaccinating sheep is considered economically worthwhile.
Simply put, a vaccination consists of the administration or inoculation of the weakened or dead strain of a pathogen into the sheep’s body. The purpose of vaccines is to trigger necessary immune responses within the organism, in this case within the sheep. Thus, following any possible future exposure to the pathogen in natural circumstances, the organism’s immune system should be able to recognise the harmful bacteria or virus and respond to it effectively. Therefore they should be able to produce a rapid response to infection and reduce or completely prevent harm. This form of medicine is preventative and often ensures that animals are able to survive when exposed to a bacteria or virus for which there can be no cure. They survive because their own bodies, due to the vaccination, will usually acquire the ability to fight off the infection themselves.
Vaccination aids in the prevention of outbreaks and transmission of pathogens throughout the flock and throughout different farms. Sheep in particular are kept in large numbers and if one contracts a disease then the infection can spread rapidly to the others. As generally outdoor animals then exposure to bacteria and viruses in the environment from contaminated surfaces, other domestic animals and wildlife can occur. Additionally, some diseases are fatal and so can result in large economic losses. Vaccination can lead to a decrease or even eradication of severe symptoms leading to death.
New sheep brought into the farm may be infected and act as sources of infection. Vaccination can reduce this risk. When vaccinating, owners should ensure that the area where the vaccination takes place is clean and that the syringe is sterilised so as to not transmit further infection. As well as vaccination being economically favourable, it can be much less stressful than having a flock infected with various diseases. Clearly, it is not possible to isolate every animal from all possibilities of infection and so vaccination can contribute to their protection.
When should sheep be vaccinated?
The age of vaccination for sheep depends of the type of vaccine given. Factors such as pregnancy should be taken into account when vaccinating a ewe since some vaccines can cause abortion. Veterinarians should ideally be consulted for advice when vaccinating animals since correct doses may differ for different breeds.
Regular boosters, including annual and twice-yearly boosters, are administered in order to provide the sheep with long term protection against certain diseases. If these are used then for the protection to be relatively continuous, as they usually are, dates for the next booster are often marked in calendars by responsible farmers.
Which vaccines are most commonly used?
The main vaccines which are administered are used because the diseases they protect may be particularly prevalent, contagious, or harmful.
A brief overview of the main diseases is as follows:
Orf
Also known as sore mouth disease, orf is a highly contagious disease in sheep. It is transmitted via skin abrasions generally in areas of rough grazing. Other animals such as dogs and cats can be transmitted the disease. Symptoms include lesions around the nose and mouth. It is possible for sheep to die after infection. Humans are able to contract the disease and this usually results in painful finger lesions which must be treated immediately. In sheep, there is no specific cure for the infected animal. Preventative measures such as removing course plants may prove to be economically worthwhile. Vaccines are available to reduce the spread of the disease.
Louping ill
Louping ill is a highly infectious disease which typically affects the central nervous system in sheep. Certain types of ticks can act as vectors, thus contributing to the transmission of the disease. The signs and symptoms of infection are fevers and in cases where the disease has progressed, neurological signs such as muscular un-coordination. The disease can be fatal to over half of infected sheep. As a viral infection, no specific treatment currently exists and vaccines may be given to sheep. Transmission can be reduced by decreasing tick numbers on the sheep.
Foot Rot
A contagious disease, foot rot results following the infection of two types of bacteria which need to interact for the disease to occur. The signs and symptoms of this disease are painful and foul smelling feet which can lead to lameness. Lameness in many sheep results in a reluctance to move to the feeding area and so growth production decreases, leading to economic losses on the farmer’s part. Antibiotics can be used to treat severe cases of Foot Rot. There are vaccinations to prevent or reduce infection in the flock.
Erysipelas
This is another highly infectious disease found in sheep. The bacteria which cause erysipelas can infect young lambs through open wounds or via the umbilicus. The joints of the sheep become inflamed and a progression of arthritis can occur. Sheep can be vaccinated to prevent lambs from acquiring the disease.
Watery Mouth
Watery Mouth is a disease which more commonly occurs in lambs following ingesting a high quantity of the bacteria E. coli. This is transmitted by oral contact with dirty bedding or contaminated surfaces such as the mother’s wool. As can be inferred from the name, excessive drooling is included in the symptoms of watery mouth. Other signs are depression and dehydration. Generally, any treatment given is given too late and fatalities often occur. Good hygiene is vital for the prevention of this disease. The lamb should also have the right amount of colostrum. Vaccines are also available to prevent the spread of watery mouth.
Pasteurellosis
Pasteurellosis is an infectious bacterial infection of the upper respiratory tract. Symptoms can include fever, depression, and sudden death. Farms with known infection of this disease require necessary vaccinations.
Toxoplasmosis
Toxoplasmosis is transmitted via ingestion of contaminated feed and water. Some sheep show no signs or symptoms and others can have abortions. Vaccines are available but can be harmful to pregnant women.
