Glossary of Terms

Glossary of Animal Health Terms

PART 1   Terms in general use
PART 2   The four diseases in the health schemes
Prepared for the British Limousin Cattle Society


A high state of freedom from a particular disease regularly monitored by testing for that disease.
Immune substances produced as a result of infection or vaccination or acquired as in colostrum or antisera.
Microorganisms that cause disease.
Serum containing antibodies to a particular disease or diseases which when administered to an animal provides it with temporary immunity.
The principle of taking measures to keep premises and therefore stock free from incoming diseases.
Bovine Viral Diarrhoea (see Part 2)
An animal having disease causing organisms within it and capable of infecting others. It may show no symptoms of the disease itself.
An independent self regulating body which sets standards for the control and eradication of four non statutory diseases (see Part 2) to which licensed participating health schemes must conform to.
The first milk rich in antibodies – the calf’s first source of immunity. Colostrum may also contain infections for example Johnes disease.
When an animal may be infected with two or more infections at the same time.
The genetic blueprint of all life. In the future testing for infectious organisms may involve looking for their D.N.A. in the diagnosis of the disease.
Divisional Veterinary Manager to whose office all incidents of notifiable diseases should be reported.
Degenerative nervous system diseases which affect all species and may be transmissible.
The process of removing a particular infection from a herd.
A health scheme licensed by CHeCS and administered by BIOBEST.
Highlands and Islands Health Scheme licensed by CHeCS and administered OLA (Orkney Livestock Association) and Biobest Laboratories
Infectious Bovine Rhinotraceitis (see Part 2)
An animal has immunity to a disease when it is protected by antibodies to that disease. It may have made these antibodies itself as a result of infection or vaccination or acquired them passively in colostrums or antiserum.
The animal’s ability to make antibodies may be interfered with by drugs or concurrent infections, for example BVD virus.
The time from when an animal is first infected with a disease until symptoms develop. For most diseases this is a few days but for encephalopies and Johnes disease for example the incubation period can be years.
Mycobacterium avium subspecies psuedotuberculosis – the scientific name for Johnes disease causative organism.
A herd is said to be monitored free of a disease when regular tests come back negative but there is still an element of doubt. The disease in question may have a long incubation period and there are limitations in the ability of the current test procedures to pick up these animals.
A fatal enteritis of young stock due to BVD complex.
An animal is said to be naïve when it has no immunity to a particular disease. New born calves before receiving colostrum are naïve. Animals participating in a health scheme in which that disease has been eradicated are naïve to it and if introduced to a new herd where that disease exists are naïve and therefore susceptible to it.
A disease is notifiable if there is a statutory requirement to notify the D.V.M of any suspicion of that disease. Examples are FMD and brucellosis.
Premium Cattle Health Scheme administered by SAC.
Persistently Infected. Calves infected with BVD virus during the first third of pregnancy and survive to term remain persistently infected. They release virus throughout their lives and are the main way in which the virus is spread. They may appear normal.
A period of isolation before an animal joins its intended herd. Animals incubating disease should show symptoms during this period as long as the incubation period does not exceed the quarantine period.
Scottish Agricultural College.
Testing a representative sample of the herd for one or more diseases.
An animal meets an infection, makes antibodies to it and recovers with no permanent side effects. For example a bull goes to market, meets BVD, has a temperature for a day, recovers and goes to its new owner symptomless. However the transient infection may have left him temporarily infertile.
Substances which when administered to an animal cause its immune system to respond by actively making antibodies to that disease. Vaccines may be dead or live.
Marker Vaccines
The vaccine is labelled in such a way that the antibodies taken from an animal vaccinated with a marker vaccine can be differentiated from antibodies that it may have made from having been infected with that disease.
Booster Vaccines
The same vaccine that was used in the initial course may need to be repeated at recommended intervals. Exposure to the disease concerned may naturally boost the animal’s immunity if previously vaccinated.
A disease of animals that can infect human beings, for example leptospirosis.


The four diseases currently available for control in cattle health schemes are:-
IBR – Infectious Bovine Rhinotracheitis
BVD – Bovine Virus Diarrhoea
Johnes Disease

IBR is an acute viral disease. In young animals it mainly affects the upper respiratory tract and can lead to a fatal pneumonia. In mature animals it causes abortions and reduced fertility. Once infected an animal remains infected for life and may release infected virus throughout its life when stressed. It is spread via airborne secretions and bulls’ semen. For pedigree breeders IBR is important in that animals and herds that have had contact with IBR are barred from export to certain countries. When the technology of marker vaccines is better understood they will have their part to play. Some European countries are free of IBR It may be controlled with vaccine but take veterinary advice especially where animals, embryos and semen from the herd may be suitable for export.
BVD is a complex of diseases of viral origin. Effects of the disease may be reduced fertility, abortion, foetal abnormalities, enteritis and mucosal disease. It is spread by PIs (Persistently Infected calves) and semen from transiently infected bulls, contaminated needles and equipment. Control is by biosecurity, removing persistently infected calves and vaccination.
Leptospirosis disease in cattle is caused by two species of Leptospiria characterised in dairy cattle by milk drop and in beef cattle by abortions in the second half of pregnancy. Infection is via infected urine either from the cow or urine contaminated water or pasture. It can affect human beings. Infected animals may be carriers for life. Control in an infected herd is by vaccination
Johnes Disease (paratuberculosi) also known as MAP is a chronic infectious bacterial enteritis that results in persistent diarrhoea, progressive wasting and eventual death. It is untreatable. It has an incubation period of 2-6 years. Animals are usually infected when young. The calf may be infected while in the womb, drinking infected colostrums and milk, or consuming food and water contaminated by Johnes infected faeces. The organism may last for a year in slurry or on pastures. In the individual animal diagnosis by laboratory means is unreliable until the disease symptoms are well established and hence a whole herd testing procedure is adopted.

The term Monitored Free has been adopted in describing freedom from Johnes disease status of a herd. In herds where no case of Johnes disease has been diagnosed, two clear blood tests 12 months apart of all animals two years and over are required for Monitored Free status. In herds that have had a positive case, three clear tests of all cattle over two years old at yearly intervals are required for Monitored Free status. However, due to the long incubation of the disease there may still be an unexpected positive. A vaccine is available but the implications of using it in a herd wishing to sell breeding stock need to be very carefully considered by the breeder.