Brucella Flashcards
General characteristics
- small, GN coccobaciclli
- no capsules, flagella, or spores
- colonies not apparent until 3-5 days of incubation (up to 21 days)
- obligate parasites
Infections localized to the ______
Reticuloendothelial system and genital tract
- abortions in females
- epididymitis and orchitis in males
- zoonotic pathogen
Is brucella eradicated in the US?
Yes
- also B. suis and abortus
B. abortus
Prefers cattle
- bison, camels, yaks infected as well
- still present in bison in Yellowstone
S. suis
Prefers swine, some strains have other hosts
B. melitensis
Goats and sheep
- also camels, alpacas, llamas
- most zoonotic
- most severe
B. ovis
Sheep only
B. canis
Dogs only
Transmission
Can survive up to 4 months in the environment
- cold weather extends survival time
- exists in milk, urine, water, damp soil
- ingestion is most common
- exposure thru conjunctival, genital mucosa, respiratory routes occurs
Source of exposure to B. abortus and B. melitensis
Through aborted fetuses, placenta, postabortion uterine fluids
- common for B. suis
Genital infections in cows
Clear within 30 days after calving
- cows are not considered infectious after that time
Vertical transmission of ____ and ____ through infected milk can occur
B. melitensis and B. abortus
Infection of accessory sex glands in males allows for venereal transmission of
- B. suis
- B. ovis
- B. canis
____ and _____ transmitted thru urine or milk
B. canis, B. suis
Dogs shed B. canis ____ in vaginal discharge after abortion
4-6 weeks
What is an important reservoir for B. suis?
Feral swine
- B. suis has been eradicated from domestic swine
Pathogenesis
Can penetrate intact mucosa
- preferred site is epithelium covering Peyer’s patches
- localizes in lymph nodes –> either proliferates or is killed
- phagocytosed bacteria survive intracellularly –> phagosome is acidified = virulence gene expression
Respiratory burst in phagocytic cells
Less effective at killing Brucella
- suppresses production of oxygen radicals
- expresses catalase and superoxide dismutase = increased resistant to oxygen radicals
- inhibits apoptosis of infected macrophages to allow persistence
Spread through reticuloendothelial system
Hematogenous spread to repro tract of males and females
- preference for pregnant females
- localized to RER of trophoblasts of the placentome
- infection spreads to the fetus and causes abortion
Disease
No systemic illness
- females abort once, due to acquired immunity
Abortion times
- B. abortus: cattle, 5th month or later
- B. melitensis: late term abortion, acute mastitis in goats
- B. suis: any time in gestation
- B. canis: abortion usually around 50 days of gestation
- B. ovis: rarely causes abortion
Males
Epididymitis, orchitis, usually unilateral
- epididymis enlarged
- dogs have scrotal swelling and dermatitis
- decreased fertility, sometimes sterility
Extragenital infections
- swine: B. suis = arthritis or lumbar spondylitis
- dogs: B. canis = meningoencephalitis, osteomyelitis, discospondylitis, anterior uveitis
Effects on herd health
- B. abortus: decreased fertility, reduced milk production, abortions in replacement animals, testicular degeneration in bulls
- B. suis: abortion, stillbirths, neonatal mortalities, temporary sterility
- B. canis: abortions, decreased fertility, reduced litter sizes, neonatal mortality
