Presentation Number # 14:
Brucellosis
-local name-cause- Brucellosis is a bacterial disease that infects many types of animals.
Humans can become infected by eating or drinking milk products that have
not been properly pasteurized and by exposure to infected fluids and tissues.
There are several different strains: B. abortus usually infects cattle and B.
mellitensis is found in sheep and goats. Both strains can infect humans and
other animal species. B abortus from cattle and especially B mellitensis from
goats are the most common infections in humans. Farmers and veterinarians
are at most risk when assisting the delivery of newborn calves, lambs, and
goats. Children and family members that drink or eat milk from infected family
milk cattle and goats are also at risk. Brucellosis bacteria are found in the
udder (milk producing tissue) and the reproductive tract (uterus or womb, the
fetus, placenta, and testicles) so contact with fluids, discharges, and milk can
transmit the infection.
Animals are also infected by exposure to these fluids and tissues, especially
when females are giving birth and other animals in the herd lick the newborn,
the placenta, or the uterine fluid on the ground or the rear of the mother.
Brucellosis causes an infection of the uterus and will often cause late period
abortions or the birth of weak offspring. Infected females may eventually have
normal offspring but will always be infected and can spread the disease to
other animals in the herd every time she comes in heat or gives birth. Some
male animals can be infected and occasionally will develop infections and
abscesses in the testicles which can cause sterility. The disease is usually
introduced into a herd when buying new infected animals or when exposed to
other animals.
Cattle have a syndrome where calves born from infected mothers will become
infected at birth but not show any disease or test positive on a blood test until
they have matured and had their first heat cycle. Once they start having heat
periods they can then spread infection in the vaginal fluid and mucus
discharge.
-symptoms- animals with Brucellosis rarely show signs of severe illness. The
most common symptoms are: a sudden outbreak of abortions in a herd, weak
offspring that usually die in a few hours to days, retained placentas, infertility,
and males can develop swollen infected testicles. Infected horses and
donkeys can sometimes develop severe draining abscesses on the top of the
shoulder and base of the neck.
Humans can become infected and have many vague symptoms; the most
common are: fever, alternating sweats and chills, headaches, back pains,
muscle pain, and weakness. The fever has a typical pattern of being very high
then dropping only to go back up again. Severe infections can damage the
brain, spinal cord, and the heart. Untreated people can be infected for years
and have long lasting damage and symptoms of periodic fevers, pain and
permanent joint damage, and chronic fatigue and weakness. Small children
can die in severe cases.
-diagnosis- the only sure means to diagnose Brucellosis is by blood tests
and the culture ( or growing the bacteria in a laboratory) of the milk or infected
tissues. The symptoms of abortion and infertility are not specific to
Brucellosis….there are many other infectious, toxic, or physical causes of
abortion that can be confused with Brucellosis. There are several acceptable
blood tests that are used in laboratories all over the world. All these tests
require collection of a small volume of blood into a glass collection tube; these
samples are spun down until the blood clot separates from the liquid serum
portion of the blood, and the test is then performed on a small amount of the
serum. The test is used to find the presence of antibodies which are small
proteins in the blood that fight the bacterial infection in the animal's body.
Infected animals develop large amounts of antibodies to try to eliminate the
infection.
-treatment- there is no inexpensive, effective treatment for Brucellosis in
livestock. Even when treated with long periods of antibiotic therapy most
animals will continue to test positive and shed the bacteria to other animals.
The best recommendation is to test all animals over 10-12 months of age and
remove the infected animals from the herd. Positive or suspected animals
should be slaughtered and not be re-sold to another farmer. Meat from
animals infected with Brucellosis is safe to eat because the bacteria is found
in the uterus and udder tissues. People slaughtering the animals must take
precautions not to touch the fluid and tissues from these 2 areas of the body.
Also, dogs should not be allowed to eat the internal organs or viscera to
prevent their infection or the movement of infected body parts to areas where
other livestock can have contact by licking or eating.
Treatment of human Brucellosis requires long periods of antibiotic therapy
using combinations of 2 or 3 different drugs for 6 weeks or longer. Even after
treatment, some people continue to have relapses of the disease especially
after periods of stress or overwork. There is a risk of chronic infections due to
damage to the heart, joints, and brain.
-prevention- vaccination is the primary means of prevention, especially in
areas with high levels of infection. Because cattle usually have a different
strain of Brucella bacteria than sheep and goats, 2 different type vaccines
must be used in these species:
- Strain 19 and RB 51 vaccines are used in cattle to prevent
Brucella abortus
-Rev -1 vaccine is used in goats and sheep to prevent Brucella
mellitensis
All Brucellosis vaccines are made from live bacteria so the veterinarian giving
the injections must be careful to not stick himself with the needle or get the
vaccine on the skin or in the eyes to prevent infection. Accidental vaccine
exposure can cause severe abscesses where the needle penetrated the skin
and cause a general infection.
Vaccination of young female animals 2-4 months of age is recommended in
most herds but adult vaccination is often used in outbreaks or in infected
herds. Male animals should not be vaccinated because the live bacteria in the
vaccine can cause infections in the testicles and sterility. Vaccination is
effective for the life of the animal and does not have to be repeated yearly like
many other diseases (Blackleg, Foot and mouth Disease, etc).
Prevention of human Brucellosis depends on controlling the disease in
animals by vaccination and eventually by testing all animals and eliminating
infected animals or herds. There is not sufficient funding or infrastructure in
Afghanistan at this time for these programs. The primary means of preventing
Brucellosis in people, especially in children, is to kill the bacteria in milk
products ( milk, yoghurt, milk chai, and cheese) by heating all fresh milk to a
high enough temperature (72 deg C for 15 minutes) or simply allowing milk to
heat until it almost boils for 30-60 seconds. This temperature will not harm the
milk but will kill Brucellosis, TB, and other bacteria. The milk should be put in
a clean container and not allowed to have contact with unheated milk by
using spoons or mixers that were used with raw milk without cleaning first.
Please contact your local veterinarian and report any cases of abortion
or infertility in animals that could be evidence of Brucellosis. Also
report suspected cases of human infection to the local health
authorities.