Brucella

Question 1

What are the species of Brucella?

Answer 1

There are 6 species of Brucella, 4 of which cause human brucellosis
• Brucellosis is a zoonosis
• Brucella is a small Gram negative coccobacillus (Biosafety level 3)
• Non-motile, Non-capsulated
• Strict aerobe, Slow growing
• Intracellular pathogen

Question 2

What are Brucella spp associated with human infection?

Answer 2

Brucella melitensis – reservoir: goats/sheep
Brucella abortus – reservoir: cattle
Brucella suis – reservoir: pigs
Brucella canis – reservoir: dogs,foxes

Question 3

What is Brucellosis?

Answer 3

• In animals, Brucella infection leads to abortion
• Brucellosis is endemic in Britain and Ireland
• Cattle: transmission through aborted fetus, milk; May be excreted in milk for many months in animals with mammary gland involvement

Question 4

What is human Infection of Brucellosis?

Answer 4

• Contact with an infected animal e.g., via inhalation of aerosols, conjunctiva, cuts or by consumption of an infected food product i.e., via GIT
• Occupational hazard – vets, farmers, abattoir workers, laboratory personnel
• Notifiable infection

Question 5

What are the portals of entry of Human Brucellosis?

Answer 5

• Conjunctivitae: By aerosols or fingers
• Inhaled aerosols: Slaughterhouse procedures, Laboratory accidents, Veterinary manipulations.
• Ingestion: Diary products, contaminated fingers.
• Abraded Skin: Veterinarian, Abattoir workers

Question 6

What are the characteristic features of human Brucellosis?

Answer 6

• Ingested by PMNs and macrophages
• Multiplies in regional lymph nodes
• Enters blood stream
• Spread to organs and reticulo-endothelial system
• Small granulomata produced in target sites

Question 7

What is acute brucellosis?

Answer 7

• After an Incubation Period of 2-4 weeks, an Influenza-like illness occurs in 50% of infected patients
• PUO- Undulant fever, Rigors/sweating
- Dry cough/lassitude/arthralgia, myalgia/headache/weight loss
• Lymphadenopathy, hepato/splenomegaly
• Depression

Question 8

What is chronic brucellosis?

Answer 8

• Occurs in untreated or inadequately treated patients
• Recurs over months or years
• Characterised by
• Evening depression
• Sweating episodes
• Aches/weakness
• Insomnia

Question 9

What is the diagnosis of Brucellosis?

Answer 9

A: CLINICAL SUSPICION
B: LABORATORY INVESTIGATIONS
1. Blood cultures; 30 - 50% positive in acute infection, take more than 1 set, up to 6 weeks incubation (Biosafety level 3)
2. Bone marrow aspirate
3. SEROLOGY
1. Serum Agglutination test (SAT), Complement fixation test, Coombs test
2. Usually have titre of > 1:160
4. PCR blood, tissue ( reference laboratory)

Question 10

What is the treatment of Brucellosis?

Answer 10

Recommended regimens:
• Doxycycline + Rifampicin for 6 weeks
• Pregnant patients, children or patients intolerant of doxycycline : cotrimoxazole + rifampicin

Question 11

What are the methods of prevention of Brucellosis?

Answer 11

• Pasteurisation of milk
• Eradication of infected cattle
• Immunisation of healthy cattle - live attenuated strain of Brucella abortus
• Avoid soft goats or sheep cheese in geographical areas where B. melitensis is prevalent
• Notifiable infection
• Post exposure prophylaxis e.g. laboratory exposure, Vaccine accidents with vets or farmers