Brucellosis - Pedigogy

Master Preventive Medicine – Notes, Case Studies and Practical Insights – with Lomash

Brucellosis:

Synonyms: Bang’s Disease, Contagious abortion, Infectious abortion, Enzootic abortion, Undulant fever

It is acute or chronic contagious disease of domestic animals characterized by placentitis, abortion in last trimester (6-9^th month)
It is primarily seen in cattle, sheep, goat, and secondarily in other animals as well.
It is zoonotic in nature and occurs worldwide.

Etiology:

Brucella abortus, B. melitensis, B. ovis, B. suis, B. canis
Non-motile, non-spore forming, gram-ve rods or cocco bacilli, aerobic bacteria that require added CO₂ for growth.
All brucella species can be destroyed by common disinfectants.
abortus had been found to survive in 60 days in manure and 182 days in foetal tissues.

Epidemiology:

This disease was first discovered by Bangs in Denmark in 1897.
Since, then it has been recorded from all most all of the countries.
Cattle are more susceptible to B. abortus than other species
Cattle remains less susceptible to B. abortus before reaching sexual maturity and becomes increasingly susceptible after reaching breeding age.
Pregnant cattle are highly susceptible.

Transmission:

Bacteria is transmitted through ingestion of contaminated food and water by discharges.
Through inhalation of organism
Through skin breach or injury
Through improperly disinfected trucks, contact with infected cattle at market place.
Congenital infection/placental transmission
Venereal route or AI through contaminated semen
Transmission through bite of ticks, flies, mosquitoes, rats, dogs is possible.
Milk of cow shed bacteria.

Pathogenesis:

Clinical Signs:

Cattle and buffalo:

Abortion takes place after 6 months onward, i.e. last triemester of pregnancy.
Greyish white mucoid or mucopurulent vaginal discharge.
Retention of placenta.
Cows shows normal signs of parturition before abortion.
Cotyledon remains attached and shows necrotic changes with sticky odorous brown exudates.
Cattle may develop swelling of bursa of joints of limbs known as hygroma.
In bull, epididymitis and orchitis are seen.
Bull loses sexual desire and remain infertile.

Sheep and goat:

Horse:

Dog:

Abortion in bitch
Following abortion, brownish mucoid odorous discharge is expelled from genitalia.
Male dog shows epididymitis, orchitis and scrotal dermatitis.

PM Lesions:

Affected foetal membranes are swollen, infiltrated with yellow gelatinous fluid.
Cotyledons shows necrotic changes.
Affected cotyledons are dirty yellow in color
Cotyledons are covered with greyish yellow deposits.
Mucus membrane of intestine and abomasum are congested.
Stomach contents are either mucoid or mucopurulent or purulent.
Sometimes, fetus is expelled in completely enveloped pus like materials with swelling of umbilicus.
Lungs shows areas of consolidation.
Edema of regional lymph nodes resulting to edema of dependent limbs.

Diagnosis:

Based on clinical signs and symptoms
Isolation of organism: organism can be isolated from tissue excretions microscopically or culturally.
Animal pathogenicity test: Guinea pig are inoculated with suspension of organs and lymph nodes of fetus, placenta, etc. enlargement of regional lymph nodes in site of inoculation and enlargement of spleen indicates positive result.
Rose Bengal plate test: It is simple and rapid test by which early infection can be detected. In this test, antigen is stained with Rose Bengal suspended in acidic buffer. Visible clumping/agglutination indicates presence of anti-Brucella antibodies.
Milk Ring Test (MRT): This is modification of agglutination test which is done with milk or cream. In this test, antigen mixed with hematoxylin are mixed with fresh milk in a sterile tube in proportion to one drop to each ml. mixture is then incubated in water bath at 37°C for a period of 30-60 minutes. Strongly positive test is indicated by a decolorized milk column capped by bluish violet cream layer.
Rapid or plate agglutination test: A drop of serum is taken from a cow which has aborted 3 weeks back on a glass slide and 1 drop of colored B. abortus antigen is to be mixed and tilted to and fro. There will be agglutination at bottom of fluid within 1-2 minutes in positive case.

Differential Diagnosis:

It is caused by Campylobacter foetus.
Abortion takes place at 5-6 months.
Placenta show pin-point hemorrhage, edema and plaque.
Agglutination test with blood and cervical at 21 and 40 days following abortion may give positive response.

This is caused by Aspergillus sps
Abortion takes place at 2-7 months.
Placenta shows necrosis and intercotyledonary areas may have raised leathery appearance.

Treatment:

There is no treatment that can cure brucellosis. Numerous drugs and combination therapy have been recommended.
Chlortetracycline, penicillin, streptomycin, oxytetracycline have been used with fair success.

Control:

Where it is desired to eradicate disease, test and slaughter will be the rational approach.
Hygienic disposal of uterine discharges, foetus, fetal membranes are to be observed strictly.
Care should be taken to clear and disinfect the contaminated premises.
All newly purchased animals are to be kept in strict isolation and tested twice at interval of 30 days before introduction in herd.
Pregnant animals should not be purchased. If purchased, it should be isolated till it calves.
Calving should be attended with all hygienic precautions.
A strain 19 Brucella abortus is used either in calves or adult cattle. Dose is 5ml which is given SC.