Brucellosis
Synonyms:
Bang's disease, Crimean fever, Gibraltar fever, Malta fever, Maltese fever, Mediterranean fever, rock fever, or undulant fever.
ETIOLOGY:
Caused by Brucella spp.; small, Gram-negative, non-motile, non-spore-forming, rod shaped (coccobacilli) bacteria. There are five Brucella spp. each causing a different form of the disease.
o Brucella abortus - affects cattle, causing bovine brucellosis (contagious abortion) o Brucella ovis - affects sheep, causing ovine brucellosis
o Brucella melintensis - mainly affects female goats, causing caprine brucellosis - can also affect female sheep.
o Brucella suis - affects pigs, causing swine brucellosis - it has also been isolated from horses. o Brucella canis – affects dogs, causing canine brucellosis.
Mode of Transmission
It may spread through the ingestion of food and water contaminated with discharge of aborted fetus /occasionally organism enter through the inhalation. In dogs, the infections spread through the aborted fetus ,discharge from the genitalia, fomites in the kennel.
Symptoms
Cattle: Abortion , usually from 6th month onward, there is grayish white mucoid purulent discharge from the vagina.the abortion may be due to toxic material liberated by organism.there may be chronic endometritis .mastitis may occur.Lactation may be decreased in the bull orchitis or epididymitis. there may be change in the seminal vesicles. Bulls loose sexual desires and remain fertile.
Dog: i): Abortion(brownish mucoid odorous discharge) ii): Epididymitis iii): Orchitis iv): Scrotal dermatitis
Prevalence
In general, brucellosis can be found in any season of the year. The epidemic peak occurs from February to July and is closely related to the months associated with delivery and abortion in animals
Diagnosis
Diagnosis is based on bacteriology or serology. B. abortus can be recovered from the placenta but more conveniently in pure culture from the stomach and lungs of an aborted fetus
Lab test are used to identify the organism: 1. isolation of organism 2. Serological test
- Staining Method:
Staining of material: Material obtains from the aborted fetus, placenta, cotyledons. Prepare stain as Carbol fuschin 20%, Acetic acid 3 % and Methylene blue 10%
Result: Brucella will stain red with a background will be black. It is first confirmatory test.
- Rose Bengal Plate Test
It is used as a screening test. It is simple and rapid test by which early infection can be detected. False positive reaction has been reported. It may be due to residual antibodies activity from vaccination. You must do confirmatory test like ELISA and CFT.
Procedure:
o 2: Mix it with the one drop of antigen.
Result: If positive then there will be formation of clumping and agglutination occurs.
- Milk Ring Test (MRT):
This test also known as ABRT( Abortus Bang Ring Test).It is also a screening test
Procedure:
o Take 1ml of milk in test tube
o Add 1 or 2 drops of stained antigen in test tube. o Mix it well by shaking
o Incubate it for 1 hr at 25-30 C.
Result: If positive then blue ring is formed on creamy surface of milk. If negative then remain white.
- Complement Fixation Test (CFT)
It is used as a confirmatory test. Immunoglobulins (IgG , IgM)has been detected.
- ELISA
It is also used as a confirmatory test.
Treatment
Antibiotics like tetracyclines, rifampicin, and the aminoglycosides streptomycin and gentamicin are effective against Brucella bacteria. However, the use of more than one antibiotic is needed for several weeks, because the bacteria incubate within cells.
The gold standard treatment for adults is daily intramuscular injections of streptomycin1g for 14 days and oral doxycycline100 mg twice daily for 45 days (concurrently). Gentamicin 5 mg/kg by intramuscular injection once daily for seven days is an acceptable substitute when streptomycin is not available or difficult to obtain
Control & Prevention
Following measures adopt to control brucellosis:
o Where it is desire to eradicate brucellosis ,test and slaughter method will be most rational approach
o All abortion should be suspected to Brucellosis, unless otherwise proved. o Hygienic disposal of the uterine discharge, fetus, fetal membrane strictly o Care should be taken to clear and disinfect the contaminated premises.
o All newly purchased animals should not be kept in strict isolation and test twice at interval of 30 days before introduction into the herd and positive reactor must be disposed off.
o Pregnant animal should not be purchased. If purchased then animal should be isolated till it calve.
o At the calving time hygienic measures should be consider.
o It is necessary to test animals those have aborted 3 weeks following abortion and the reactors should be eliminated.
o Scheduled vaccination programs for young animals
o Screening of herds, livestock markets, abattoirs & Subsequent removal of diseased o Awareness among the farmers, livestock & public health authorities
Successful eradication has been made possibly in many countries. But it is not controlled in Pakistan due to poor hygienic measurement. All brucella organisms are killed by commonly used disinfectants, but brucella abortus has been found to survive 60 days in manure and 182 days in fecal material.
A strain 19 and RB51 Brucella abortus is used in calf or adult cattle. it is used in calves between 4 -8 month of age. Dose of 5ml is used subcutaneously. Adult cow can also be vaccinated with this strain but reaction are expected to be more severe and pregnant animal may abort. Animal vaccinated at adult stage develop agglutinin which persist throughout their lives.
Another vaccine Brucella abortus 45/20 Killed vaccine is useful to control disease in tropical countries. Commercial Brucella abortus c-19 live freeze dried vaccine (intervet). Female calf at 5-7 month to be vaccinated. There is no need to vaccine in bull which is used for natural mating .if bull used for AI then it is necessary to perform screening test to declare the bull free from brucellosis infection.
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