Brucella + Brucellosis Flashcards
What are some synonyms for brucellosis?
- malta fever
- mediterranean fever
- undulant fever
- contagious abortion
- infectious abortion
- enzootic abortion
Describe the microbiology of brucella
- gram negative small coccobacilli
- non-motile, non-sporulating
- aerobic, capnophilic, catalase +
- urease + (except B. ovis)
- facultative intracellular
- multiple species
- environmental persistence (withstands drying, temp, pH, humidity)
What are the 6 species of Brucella and what types are they?
- B.abortus, B. melitensis, B suis - smooth
- possess O=polysaccharide (OPS)
- cause most disease
- B.ovis, B.canis - rough
- do not produce OPS
Describe the taxonomy of Brucella
- phylum: alpha Proteobacteria
- order: Rhizobiales
- family: Brucellaceae
- genus: Brucella
What are the clinical signs in ruminants?
- largely sub-clinical until the final trimester
- repro failure, abortion
- most infected cattle will only abort once, but excrete large amounts of bacteria after calving
- calves then born will be weak/ unhealthy
What is the main route of introduction for Brucella?
- animal movement
- introdction of infected animals into herd/ flock
- shared grazing
How does Brucella affect non-pregnant animals?
Describe the process of infection of Brucella in pregnant and non-pregnant animals
Clinical signs in pigs?
- similar to ruminants
- may see swollen joints and tendon sheaths
- lameness, incoordination
- posterior paralysis
- spondylitis
- abscesses in various organs
Clinical signs in horses?
- vague lameness
- classically ‘fistulous withers’ - infected bursae
Clinical signs in marine animals?
- similar to all others
- plus meningoencephalitis
- subcutaneous abscesses
Who is at risk for human brucellosis?
- cattle ranchers/ dairy farmers
- vets
- abattoir workers
- meat inspectors
- lab workers
- hunters
- travelers
- consumers of unpasteurized dairy products
How is zoonotic Brucella transmitted?
- conjunctiva or broken skin contacting infected tissues
- ingestion
- inhalation of infectious aerosols
- inoculation with vaccines
- incubation: 7-21 days- several months
What are Brucella’s mechanisms of pathogenesis?
- intracellular existance in vivo
- facultatively extracellular intracellular pathogen
- reside within non-professional phagocytes such as macrophages and from Brucella containing Vacuoles (BCVs)
- invisible for immune system (stealth pathogen)
- pre-activated macrophages e.g. with IFN-y, successfully kill invading Brucella cells
What virulence factors does Brucella lack?
- Capsules
- Adhesins
- Fimbriae
- Excreted toxins
Describe the Virulence: Type IV secretion system
- Injection needle
- injects effector proteins in cytoplasm cell
- T4SS is crucial for establishment of the replicative niche- an endoplasmic reticulum (ER) derived vacoule
- Brucella T4SS mutants are highly attenuated
What are the different diagnostic tests for Brucella?
- serological testing
- testing of milk
- examination of smears
- culture of products of abortion
- tissues collected post mortem
- bacteriological identification
How is microscopy used in diagnostics?
- smears of milk, vaginal discharge or placenta
- stamp’s modified Ziehl-Neelsen method
- gram negative bacteria, not truly acid fast, but they are resistant to decolourization by weak acids
How can culture be used in diagnostics?
- tissue are often contaminated and Brucella are slow growing so:
- due to slow growth, selective media are usually required on primary growth
- use a selective media e.g. Farrells’s medium containing 10-20% v/v horse serum
- serum detroxe agar generally recommended only for subculture
- use 10% CO2
How is typing used in diagnostics?
- generally only in Reference Labs
- serology based on variants of surface OPS
- susceptibility to phages
- growth on media containing dyes
- CO2 requirement, H2S production
- molecular tests (in nonreference labs)
- based on tandem repears, variable repeats
- multilocus sequence typing
- PCR based
How is serology used in diagnostics?
- LPS surface antigens (OPS) very immunogenic
- other organisms share epitopes and cause cross-reaction
- Yersinia enterocolitica O:9 real probelm
- incubation period variable depending on challengs
- abortion may precede serological reaction
- antibodies present in serum and milk
- cost, sensitivity and specificity important issues in survelliance programme
- take vaccination into account
How is Brucella controlled?
- Pasteurisation of milk
- vaccination of cattle, sheep, goate in enzootic areas
- but level of post-vaccination serological reactions requires cessation if prevalence <2%
- eradication testing and culling
- continure surveillance milk/ blood
- identification of herds and individual animals
- epidemiological tracing
How is Brucella controlled by vaccination?
- reduction from >5% prevalence to <2% by vaccination
- cattle: B.abortus S19 (smooth) or RB51 (rough)
- sheep and goats: B.melitensis Rev1 (smooth)
- no vaacine for swine/ humans
- protective efficiency of smooth strains = 80%
- protective efficiency of rough B.abortus RB51 is lower
- all exert insufficient pressure for disease eradication
When should you not use a live vaccine?
- in pregnant animals
What are the costs to the world economies?
- africa - >10%
- India - 16%
- asia - $3.4 billion
- Argentina - B.abortus - $60 million
- Brazil - $450 million/year
What is Brucella linked to?
- goats milk
WWho identified small cocci in spleen?
- Sir David Bruce
- cultured bacteria
- reproduced the disease
- named micrococcus melitensis
What did Bernhard Bang discover in 1897?
- causative agent of contagious abortion
- milk pasteurized in 1930
Historical timeline of Brucella?
- 1930 - 40% of cattle infected
- 1962 - free calf vaccination (live S19)
- 1967 - herd scheme - slaugher, incentives
- 1971 - compulsory areas, replace with Brucella free animals
- 1979 - eradicated
- 1991 - OBF region of EU
- 1993 - reintroduced to Wales from France
Describe the microbiology of brucella?
- gram -ve
- small
- coccobacilli
- aerobic
- facultative intracellular
- catalase +ve
- non-sporulating
- non-motile
- capnophilic
- urease +ve - not B.ovis
- environmentally persistent
WHich species does B.abortus infect?
- cattle
- bison
- buffalo
- HUMAN
Which species does B.melitensis infect?
- sheep
- goats
- HUMAN
Which species does B.suis infect?
- swine
- European hares
- reindeer
- rodents
- HUMAN
Which species does B.canis infect?
- dogs
- HUMAN
Which species does B.ovis infect?
- sheep
WHich species does B.neotomae infect?
- rodents
B.maris, B.pinnipediae, B.cetaceae?
- marine mammals (seals, walruses, whales, dolphins)
- maybe humans
