Dairy Farming Manual
|What is Brucellosis? (5-10)
1 Brucellosis is a bacterial disease which is dangerous for your animals and you.
|What are the signs of Brucellosis? (11-17)
2 The signs include:
Cows: abortion or still birth
|How can your animals get Brucellosis? (18-26)
|How can you treat, prevent and control Brucellosis?
4 You cannot treat Brucellosis.
Husbandry Unit 10.2:
Note: Numbers in brackets refer to illustrations in the Extension Materials.
Brucellosis is an infectious disease,
causing abortion, infertility and decreased milk yield in cattle.
It may cause serious disease in people as well.
What is Brucellosis?
|5 Brucellosis is a disease which can pass easily from one animal to another.|
|6 Your cows can lose their calves because of the disease.|
|7 If your cows get Brucellosis, they produce less milk (because of abortion).|
8 Brucellosis is also a dangerous disease for people.
- muscle pain
Cause of disease (9)
Brucellosis is caused by a bacteria. The type which affects cattle is called Brucella Abortus. The bacteria can survive not only in the animal but also in the surroundings for some time.
Affected animals (10)
Brucellosis can attack cattle,
buffalo, goats, sheep, dogs, horses, and a number of other animals as well.
People can also get seriously ill when infected from cattle with Brucellosis;
the disease in man causes fever, headache, muscle pain and weakness.
| What causes Brucellosis?
This bacteria can live for a long time
in the animal and in the surroundings.
|Which animals get Brucellosis?
|What are the signs of Brucellosis?
Abortions and still born calves
11 Cows with Brucellosis have abortions or still born calves, usually in the last 4 months of pregnancy.
After abortion, there are bacteria in:
- the discharge from the uterus
Signs of disease (11-16)
Abortions and still-born calves delivered at, or just before, term are often the two most obvious features to be observed. Abortion usually takes place in the last half of pregnancy. After abortion metritis (i.e. infection of the uterus) will follow in the majority of cases, impairing the fertility of the animal. Other signs of Brucellosis infection in a herd may be increased incidence of retained placenta (i.e. placenta is not delivered after birth, but stays in the uterus) and decreased milk yield.
After abortion, bacteria are found in the placenta and foetus, and also in the uterine discharges of the cow and in the milk.
If a cow has aborted once, she
will normally not abort again due to Brucellosis - but she will continue,
at subsequent normal calvings, to shed the bacteria from the uterus and
in the milk. In this way she is a permanent risk to other cows, and
to people as well.
|12 Next pregnancy, your cow will normally not abort because of Brucellosis but bacteria still live in the uterus and in the milk.|
|13 Your cow passes Brucellosis on to other animals and to other people.|
14 After abortion your cow may get an infection in the uterus (metritis).
If the infection is serious your cow may
not get pregnant again.
15 If your cow has Brucellosis, the placenta may stay in the uterus.
| Bulls can also be affected.
In bulls the bacteria cause inflammation of the testicles and other reproductive
organs. This means that the bacteria can be present in the semen.
Pregnant cows and heifers are much more susceptible to infection than non-pregnant animals. Calves not yet at puberty are fairly resistant to infection.
Low milk production
16 Cows with Brucellosis have abortions and so produce less milk.
|Inflammation of the male reproductive organ
The semen can contain bacteria.
|How can your animals get Brucellosis?
The bacteria live in:
- the milk.
Colostrum from cows with Brucellosis can give the disease to calves from cows which do not have Brucellosis.
Infected cows and heifers are the most common sources of infection. As mentioned above: If a cow has once been infected, it will keep on housing and excreting bacteria for a lifetime, even after it is apparently normal again. This means the cow has become a carrier that can infect the rest of the herd.
Bacteria are especially found in the placenta, aborted foetuses, uterine fluid and discharge from the vagina as well as milk from infected cows. Colostrum can transmit the disease to calves of uninfected cows.
Semen used from infected bulls can also transmit the disease to cows by A.I. or, in rare cases, by natural breeding.
Bacteria spread by infected cows can survive for weeks outside the body, and the possibility of spreading disease through con-taminated tools, people or other animals is large.
The incubation period, i.e. the
period from exposure to the infective agent until signs of disease, is
very different from case to case, from about 1-2 weeks until several months.
|20 Semen with bacteria can pass on Brucellosis in A.I. and sometimes in natural mating.|
|21 Bacteria live for some
time outside the body.
Vehicles, equipment and you can easily carry the bacteria from one animal to another.
|22 The period from contact with the bacteria to signs of the disease can be 1 week up to 3 or 4 months.|
heifers get Brucellosis more easily than non-pregnant animals.
Blood samples from infected animals can be tested in the laboratory for disease. Similarly, samples of discharge from the vagina or from aborted foetus (stomach) can be sent to the laboratory for diagnosis.
Diagnosis on a herd basis, is often undertaken by screening herds with the Milk Ring Test (MRT) (also called Brucellosis Ring Test, BRT).
This simple test can be carried out on bulk milk either on the farm or during reception at the dairy plant/milk collecting centre. When infected herds are located by BRT, reactors are found individually by serological testing. An area can be continuously screened by applying the BRT this way 3-4 times a year.
Another way to screen herds in a country or a region is to examine blood samples of all cattle in the area but this is of course far more costly and the BRT is sufficiently reliable as a screening test if followed by blood testing of individual cattle in reactor herds.
In areas where the BRT is applied
to dairy herds serologic testing of all marketed beef cattle can be undertaken.
If reactors are found the herd of origin is tested by individual blood
|24 Your vet can identify Brucellosis
by laboratory tests on:
- discharge from the vagina
- stomachs from aborted foetuses.
|25 He can check your herd 3-4 times a year by the Milk (or Brucellosis) Ring Test on your farm or at the milk collecting centre.|
|26 If the Milk Ring Test is positive he takes blood samples of all your animals for laboratory testing.|
Treatment and prevention (27-30)
Treatment of individual animals has been tried, but without success.
On the other hand, successful eradication of the disease has been carried out in several countries by detection and slaughter of infected animals, followed by proper disinfection of premises and succeeding testing of remaining animals in the herd.
It must be kept in mind that even though animals that have aborted once normally calve at term in the following calvings these animals keep on secreting bacteria from the uterus and genital organs after calving and frequently continuously in the milk. This means that other animals in the herd will be infected sooner or later, if the carriers are not slaughtered.
Prevention is possible by vaccination of female calves. This gives a high grade of protection although some animals may be infected if they are heavily exposed to Brucellosis bacteria.
Replacement animals should be tested before introduction into the herd and/or they should be vaccinated animals only.
Vaccination on a national scale
has been practised with a high degree of success, provided the aim is a
reasonable level of control with the disease. Complete eradication
in a region or a country, needs slaughter of infected animals and continuous
screening, possibly combined with vaccination of calves. The slaughter
policy has been applied with success in some European countries.
In Asia, vaccination is often obligatory, and slaughter of infected animals
recommended to farmers.
|How can you treat animals with Brucellosis?|
|How can you prevent and control Brucellosis?
28 You can control Brucellosis
|29 Vaccination of female calves helps prevent Brucellosis but they may still get the disease with a lot of contact with the bacteria.|
|30 Always test
before mixing them with your herd.