World Veterinarian Quiz 36

 

Brucellosis

It is an acute or chronic contagious disease of domestic animals that causes placentitis and abortion. The disease thereby possesses a threat to cattle economy. It has been estimated that brucellosis and Cattle and Buffalo causes an annual economic loss of 240 million Rupees.

Synonyms:

Human Disease

•      Malta Fever

•      Undulant Fever

•      Mediterranean Fever

•      Rock Fever of Gibraltar

•      Gastric Fever

Animal Disease

•      Bang’s Disease

•      Enzootic Abortion

•      Epizootic Abortion

•      Slinking of Calves

•      Ram Epididymitis

•      Contagious Abortion

 DISTRIBUTION:

In 18^th century contagious abortion was observed and the agent involved in it known as Brucella abortus was discovered by a bang in 1897 in Denmark.

The disease since then have been recorded from almost all the countries of the world.

•      Sir David Bruce (1855-1931)

–     British Army physician and microbiologist 

–     Discovered Micrococcus melitensis

–     Malta fever

•      A Danish physician and veterinarian, Bernhard Bang discovered Bacterium abortus in 1897 while investigating contagious abortion that had been affecting cattle in Denmark for over a century. He also discovered the organism affected horses, sheep, and goats. Thus the disease became known as “Bang’s disease”.

 

 

ETIOLOGY:

The brucellosis is caused by…

Species	Biovar/ Serovar	Natural Host	Human Pathogen
B. abortus	1-6, 9	cattle, bison, buffalo	yes
B. melitensis	1-3	goats, sheep	yes
B. suis	1, 2, 3	swine	yes
	2	European hares	yes
	4*	reindeer, caribou	yes
	5	rodents	yes
B. canis	none	dogs, other canids	yes
B. ovis	none	sheep	no
B. neotomae	none	rodents	no
B.maris B.pinnipediae,		marine mammals	yes?

 

Brucella species are non-motile, non-sporing small gram negative rods or coccobacilli.

Amongst the various species of B. abortus several strains exist and these are defined as bio types.  

Except B.suis and B.canis all organisms require CO2 for growth.

•      Gram negative coccobacillus

–     Facultative,
intracellular organism

•      Environmental persistence

–     Withstands drying

–     Temperature, pH, humidity

–     Frozen and aborted materials, dust, soil

 

SUSCEPTIBLE HOSTS:

Though all the species of brucella are relatively specific for individual species of animals but they can produce infection in other species of animals and man.

Cattle are more susceptible to B. abortus.

Cattle remain less susceptible to Brucella abortus before reaching sexual maturity and become increasingly susceptible while they attain breeding age.

Pregnant cattle are highly susceptible.

In horses the Organism is present in Bursa causing bursal enlargement or present in Association with Actinomyces bovis resulting to fistulous Withers and pole evil.

Brucella canis is not transmitted to other species except cat and man.

MODE OF TRANSMISSION

Brucella infection is spread through ingestion of food and water contaminated with discharges of aborted foetus or foetal membranes.

The organisms are shed in the great concentration with the infected foetus, foetal membranes and genitalia for several days before and after abortion.

Transmission of infection through flies, ticks, rats, dogs, infected bulls and other inanimate object as possible.

Population at Risk

•      Occupational disease

–     Cattle ranchers/dairy farmers

–     Veterinarians

–     Abattoir workers

–     Meat inspectors

–     Laboratory workers

•      Hunters

•      Travelers

•      Consumers

–     Unpasteurized dairy products

 

PATHOGENESIS

B. abortus has got affinity to invade gravid uterus, mammary glands, testis, lymph nodes and joints.

⇓

The bacteria following invasion localise in the nearby lymph nodes and other lymphoid tissues like spleen, iliac lymph node etc.

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The organisms thereby reach circulation multiply and set off bacteraemia.

⇓

The organisms colonise in gravid uterus and placenta and multiply in large proportion in these tissues.

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A substance known as erythritol is produced by the foetus.

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This is capable of triggering the multiplication of brucella abortus thus there is heavy concentration of bacteria in the foetal fluids causing infection of uterine tissues leading to severe ulcerative endometritis.

⇓

There is abortion during the last trimester of pregnancy.

⇓

Non pregnant adult may develop self limiting immunizing infection and turn into a carrier.

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In the males the organisms multiply in large proportion and localise in epididymis, testis and other accessory sex organs.

⇓

There is epididymitis and orchitis.

⇓

The organisms are shared through semen and thus the males remain a cause of infertility in a herd.

CLINICAL SIGNS

1.    Abortion in last three months of pregnancy it causes abortion storm.

2.    Orchitis and epididymitis in bulls which are spreader of the disease.

3.    Synovitis (Hygromas Swelling)

4.    Fistulous Withers—horse generally suffers and acquires the infection from cow.

Horse

•      B. abortus most common

–     Susceptible to B. suis

•      Fistulous Withers or Poll Evil

–     Inflammation of the

            supraspinous bursa

–     Exudative process

•      Bursal sac fills with clear viscous liquid

•      Can eventually rupture

Swine:

•      B. suis

–     Prolonged bacteremia

–     Abortion, early or late gestation

–     Fertility problems

–     Lameness, posterior paralysis,

–     spondylitis,

–     metritis,

–     abscesses

  Canine:

•      B. canis

–     Abortions

•      Last trimester

•      Prolonged vaginal discharge

–     Bacteremia

–     Failure to conceive,

–     stillbirths,

–     prostatitis,

–     epididymitis

•      Also susceptible to

–     B. melitensis, B. abortus, and B. suis

Marine

•      Reproductive effects

–     Abortion, placentitis

–     Orchitis

•      Systemic disease

–     Meningoencephalitis in dolphins

•      Secondary invader/opportunistic pathogen

–     Debilitated seals, dolphins, porpoises

DIAGNOSIS

The main object of diagnosis of brucellosis in the laboratory is aimed at to identify the animals which are infected and shedding the organisms and thus spreading the disease.

It is not difficult to identify the infected animals employing standard Serological test.

Lab test used in the diagnosis of brucellosis include

1. Isolation of organisms

2. Animal pathogenicity test

3. Test for the presence of antibodies.

Rose Bengal plate test (RBPT): This is a simple and rapid test by which early infection can be detected. This test can be used for the screening of herd. In this test the antigen is stained with rose Bengal dye suspended in acidic buffer.

Milk ring test (MRT): This is modification of agglutination test which is done with milk or cream.  This is a simple test and has found widespread use in locating potentially infected herds.

This test is inexpensive and easy to perform and therefore worthy of consideration as a bulk screening test to effect a preliminary reduction in the pool of infection in heavily brucella abortus infected dairying herds.

LESIONS

•      Granuloma- caseous necrosis – not always present

•      B. suis – granulomas in all tissues

•      Induration of bovine mammary gland and supramammary lymph nodes

•      Rams – tail of epididymis

TREATMENT

There is no known treatment which can cure brucellosis in domestic animals.

Numerous drugs and combination therapy have been recommended.

Penicillin, streptomycin, oxytetracycline have been used with fair amount of success.

VACCINES

Strain 19 B.abortus

B. abortus 45/20 killed vaccine