General information on Brucellosis
|Geographical Distribution of Brucellosis in Africa (red marked)|
Brucellosis is prevalent in most countries of the world.
- Natural transmission occurs by ingesting the bacteria, which are present in large numbers in aborted foetuses, foetal membranes and uterine discharges. Cattle may ingest contaminated feed or water, or lick contaminated genitals of other animals.
- Venereal transmission by infected bulls to susceptible cows appears to be rare. Brucella may enter the body through mucous membranes, the conjunctiva, wounds or intact skin.
- The disease is spread when aborting animals discharge B. abortus bacteria in the placenta, foetus and vaginal discharges to the ground, where they can survive for several weeks. Excretion of the bacteria may occur for several days before abortion and for some time after. Cattle become infected when they ingest or inhale contaminated material. Brucellae bacteria have been recovered from fetuses and from manure that has remained in a cool environment for more over 2 months. Exposure to direct sunlight kills the organisms within a few hours.
- A cow's tail, heavily contaminated with infected uterine discharges, may spread infection if it comes in contact with the conjunctiva or intact skin of other animals. The placenta, placental fluids, and foetus from an aborting animal contain organisms which contaminate the vulva, tail and legs of the animal and the surrounding environment.
- In in-calf females, the bacteria invade and cause abortion in the 7th month. The incubation period is about 6 weeks. It is only when a placenta exists i.e. in the second half of pregnancy, that the uterus is invaded and abortion occurs.
- Shedding from the vagina largely disappears with the decrease in fluids following calving. Some cows that previously aborted shed Brucella from the uterus following normal calvings.
- Transmission may occur by artificial insemination when Brucella-contaminated semen is deposited in the uterus
- The disease can be transmitted to the unborn calf through the placenta by the infected dam. This disease can have serious negative economic consequences to stockmen in both modern intensive dairy systems and pastoral production enterprises.
- Organisms are shed in the milk for a variable period of time in most previously infected cattle for life.
- Housing or confining cattle increases the likelihood of transmission. Under free range conditions the disease is of lower prevalence.
Spread to man
- Man becomes infected when in direct contact with cows at abortion, calving or in the post calving period.
- Vets and stockhandlers are particularly at risk from the splashing of infected droplets into the eye.
- Infection occurs in people drinking unpasteursied milk or milk products.
- Symptoms include recurrent bouts of fever, headache, muscle and joint pains and and general weakness. Brucellosis is often confused with malaria and influenza.
Risks from Raw Milk
In non-pregnant infected animals the Brucella live inside the udder and are excreted with the milk. This presents a very serious health risk to anybody drinking raw milk. Brucellosis is a dangerous zoonosis. To protect yourself and your family always boil milk before consumption.
Signs of Brucellosis
- Abortion is the most obvious manifestation. Animals abort from the 7th month onwards.
- Infections may also cause stillbirths or weak calves, retained placentas, and reduced milk yield. Usually general health is not affected in uncomplicated abortions.
- In less acute infections, cattle may give birth to a full term but weak calf, or merely show a retained placenta. Cows may become infertile due to chronic uterine infection.
- After abortion, the afterbirth doesn't come out (retained placenta). This can further develop to Metritis (infection of the uterus), which often causes infertility.
- In bulls, no symptoms may be seen but if they are, they may include inflammation of the testes, lack of sexual activity and possibly infertility.
- Subcutaneous (under the skin) swellings containing infected fluid may appear on the legs of infected cattle and the placenta often has a thickened leathery appearance with some discolouring.
- Calves infected before puberty usually lose the infection once removed from the source of contamination.
- Mature non-pregnant animals, or animals in early pregnancy, when exposed to infection, are more likely to develop immunity than to show symptoms of disease.
Brucellosis can be diagnosed in abortion materials (placenta, foetus, uterine discharge) and in blood. In cattle, Brucellosis can also be diagnosed in the milk, the milk test is called Milk-Ring-Test.
All aborted foetuses should be handled carefully with gloves to avoid human infection. Do not touch with bare hands!
If you suspect Brucellosis in a lactating cow collect a fresh clean raw milk sample (one cupful is plenty), keep it chilled and take it to the nearest lab for testing.
Abortion: See Vibriosis, Leptospirosis, Rift Valley Fever
Prevention of Brucellosis
Non infected herds must be protected. The greatest danger is from replacement animals. Additions should be vaccinated calves or nonpregnant heifers. If pregnant or fresh cows are added, they should originate from Brucellosis-free areas or herds and be seronegative. Replacements should be isolated for around 30 days and retested before being added to the herd.
A single vaccination of heifers between 5 and 8 months of age with S19 vaccine (also called Buck 19) will normally protect cows for life. S19 vaccine can also be used on adults to vaccinate all animals and to protect the whole herd. Because S19 vaccine can cause abortions, it is safer not to vaccinate pregnant animals.
Bulls should not be vaccinated as the vaccine may result in the organism appearing in the semen Adult cattle should be vaccinated annually with dead B. abortus vaccine (45/20), or a with a reduced dose (one twentieth) of S19 vaccine.
S19 vaccine should be handled with care. It is a live vaccine and can infect humans.
S19 vaccine can also be used to protect livestock other than cattle, but the best time for vaccination and the duration of immunity are not well known. In some countries there are special Brucellosis vaccines for sheep and goats.
Vaccination will reduce the number of infected animals in a herd by by over 90% if carried out over a period of 5 years. Vaccination cannot eradicate Brucellosis but it can lay the groundwork for future eradication.
Prevention - Control - Treatment
The disease can be controlled by:
- Managing effective sanitary measures in the cattle environment
- Vaccination. Calves under eight months can be vaccinated with live vaccines (S.19) to prevent infection. Such vaccinations can provide lifelong immunity. However, the live vaccine should be used with care in adult animals because it can cause abortion in in-calf females and inflammation of the testes in adult males. Adult cattle should be vaccinated annually with dead B. abortus vaccine (45/20).
- Because of the danger of human infection, infected fetuses, placenta and cows should be handled with great care. Handlers of such material should always wear gloves for protection. They should also ensure that keep their hands away from the mouth, nose and eyes until after the hands are thoroughly disinfected.
Other useful home remedies
- Isolate all cows that have aborted until all the discharges have stopped
- Burn or burry all contaminated materials such as fetuses, foetal membranes
- Clean and disinfect all cattle premises which may be contaminated with fetuses and foetal membranes.
- With the risk of human infection, proper hygienic precautions should be taken when handling abortions and where infection is known to occur in certain herds of cattle, drinking of raw milk and un pasteurized milk products should be prohibited
- Samburu: Crush a piece of sokotei root (Salvadora persica, toothbrush tree) about two fingers long. Boil in 5 litres of water for 1 hour. Allow the mixture to cool, than sieve and drench the animal has aborted. Use 2 litres for cows, 1 litre for sheep and goats.
(Source: ITDG and IIRR, 1996)
Information Source Links
- Barber, J., Wood, D.J. (1976) Livestock management for East Africa: Edwar Arnold (Publishers) Ltd 25 Hill Street London WIX 8LL. ISBN: 071310063X
- Blood, D.C., Radostits, O.M. and Henderson, J.A. (1983) Veterinary Medicine - A textbook of the Diseases of Cattle, Sheep, Goats and Horses. Sixth Edition - Bailliere Tindall London. ISBN: 0702012866
- Blowey, R.W. (1986). A Veterinary book for dairy farmers: Farming press limited Wharfedale road, Ipswich, Suffolk IPI 4LG
- Force, B. (1999). Where there is no Vet. CTA, Wageningen, The Netherlands. ISBN 978-0333-58899-4.
- Hall, H.T.B. (1985). Diseases and parasites of Livestock in the tropics. Second Edition. Longman Group UK. ISBN 0582775140
- Hunter, A. (1996). Animal health: General principles. Volume 1 (Tropical Agriculturalist) - Macmillan Education Press. ISBN: 0333612027
- Hunter, A. (1996). Animal health: Specific Diseases. Volume 2 (Tropical Agriculturalist) - Macmillan Education Press. ISBN:0-333-57360-9
- ITDG and IIRR (1996). Ethnoveterinary medicine in Kenya: A field manual of traditional animal health care practices. Intermediate Technology Development Group and International Institute of Rural Reconstruction, Nairobi, Kenya. ISBN 9966-9606-2-7.
- Pagot, J. (1992). Animal Production in the Tropics and Subtropics. MacMillan Education Limited London. ISBN 0-333-53818-8
- The Organic Farmer magazine No. 50 July 2009