Brucella, Campylobacter, Lawsonia Intracellularis

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Characteristics of Brucella

Back 1

-All Brucella genetically highly related
-Small, non-motile Gram- rods
-MZN+
-Has 2 chromosomes
-Obligate parasites: intracellular multiplication; predilection for repro organs
-Selective media: CO2 enhances growth
-Commonest zoonotic infection in the world -- usually lab acquired

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Brucella abortus characterisitics

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-Cattle mainly affected
*Zoonosis: humans get intermittent fever
-Aborting cow = 10^9 - 10^10 CFU/g fetal fluids of B. abortus
-Survive up to 4-6 months in the environment
-Ingestion most common route (10^4 = infectious dose)
-Abort at >20 wks

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Brucella abortus pathogenesis

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-Chronic disease, persists for life
-Pregnant animals abort only after initial infection; will shed Brucella during parturition in subsequent pregnancies
-Non-pregnant animals: organisms localize to spleen, mammary gland, and lymphatics
-Bulls: Organisms localize to vesicles, testes, epididymus; causes orchitis; transmission via contaminated semen

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Brucella abortus clinical signs

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-Pregnant animals: abortion at >20wks; abortion storms in herds with many susceptible cows
-Infected cows usually abort once; Calves born from later pregnancies may be weak and unhealthy
-Calves become susceptible to infection as the approach the breeding age
-Affected herds: decreased fertility, reduced milk production, abortions in replacement animals, testicular degeneration in bulls

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Diagnosis of Brucella abortus

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-Serology (buffered B. abortus Ag tests), microscopy (MZN) and isolation of the organism (10% CO2)
-Specimens:
*Fetus - whole fetus, fetal abomasal contents, fetal lesions, placenta
*Dam - uterine discharges, colostrum, milk, paired serum samples
*Bull - semen
-Typing of the organism: biochemical and molecular (PCR)
-Antibody tests
-Milk ring test or ELISA

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Control of Brucella abortus

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-National eradication: test and slaughter
-Reactors: isolate, disinfect, discard milk, depopulate
-Abortions: notify, isolate, fetus to lab
-Vaccination: live attenuated vaccines (RB51 and B. abortus 19)
*B. abortus 19 compromises serological tests (can't tell btw infected and vaccinated animals)
*RB51 preferred in many countries

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Where are remaining cases of B. abortus found in USA?

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In free ranging bison in Yellowstone National Park

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Brucella melitensis

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-Affects goats and sheep (goats probably more susceptible) in the Mediterranean/Middle East/South America
-Infection in goats resembles B. abortus in cattle --> high abortion rates, orchitis in rams, arthritis
-Persistent infection: shedding of organisms in milk --> public health risk
-Control:
*test and slaughter
*Rev.1 B melitensis live attenuated vaccine: lambs/kids <6mo (life long immunity); still retains some virulence (abortions in pregnant goats, risk to humans)

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Brucella melitensis as a human pathogen

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-Occupational hazard
-Difficult to treat: doxycycline or in combo with streptomycin
-No vaccine for humans
-1st weaponized pathogen!
*resistant to drying, survives well in environment
*B. melitensis causes the most severe disease follow by B. suis > B. abortus > B. canis

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Brucella ovis

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-In sheep only
-Epididymitis in rams, placentitis in ewes
-Venereal transmission
-Reduced fertility, abortion, increased perinatal morality
-Control: Rev 1 vaccine
-NOT zoonosis

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Brucella suis

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-Affects pigs in Central/South America/Asia
-Causes abortion in sows, orchitis in boars
-Oral and venereal transmission
-Prolonged bacteremia: localizes in wide range of tissues
-Control: test and slaughter; NO vaccine!!

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Brucella canis

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-Affects dogs in USA/Japan/Central & South America
*Possibly exotic in Ireland: serologically + animals found here
-Rough/weaker pathogen
-Oral and venereal transmission
-Enlarged lymph nodes
-Causes abortion in females, orchitis/epididymitis in males
-Treatment: prolonged antiobiotic treatment, difficult to clear infection (don't treat breeding animals), NO vaccine

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Campylobacter characteristics

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-Gram - curved rods; small colonies
-Normal flora of many animals
-Motile
-Microaerophilic
-C. jejuni is thermophilic
-Selective medium

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Camplylobacter fetus subsp. venerealis

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-Bovine Genital Camplylobacteriosis = infertility in cattle!!
-Asymptomatic carrier bulls >4yrs old
-Transmitted during coitus
-Heifers mostly affected: develop an Ab-mediated immunity after infection lasting 2-4yrs
-Clinical signs: abortion in heifers, infertility, long estrus cycles
-Pathogenesis: S-layer = virulence factor
*S-layer can switch on/off allowing Ag shifts
*Promotoes perisistence/carrier states
-Diagnosis:
*cervo-vaginal mucus ]
*preputial washings/smegma ]--FAT
*fetal abomasal contents ]
*PCR
-Control: vaccine (Bacterin) for problem herds (not available in Ireland), antibiotics in bulls
*Limited efficacy in clearing organisms from vagina/cervix

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Campylobacter fetus subsp. fetus

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-Ovine Genital Campylobacteriosis
-Affects sheep (and cattle)
-Causes sporadic abortions
-Intestinal commensal
-Pathogenesis: bacteremia, localization in the uterus, placentitis, abortion in the 2nd-3rd trimester
-Recovered ewes immune (~3yrs)
-Diagnosis: clinical signs, fetal hepatic lesions, culture
-Control: isolation of aborting ewes, antibiotic treatment (chlorotetracycline), vaccination (dead vaccine- Bacterin)
-C. jejuni is a similar syndrome that leads to abortion
*more common in Ireland than C. fetus subsp. fetus
*Vaccine does NOT protect against C. jejuni

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Enteric Campylobacteriosis

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-Caused by Campylobacter jejuni, C. coli, and C. lari
-Normal flora of birds and animals so attributing cause/effect is difficult
-Causes occasional diarrhea in animals: most cases reported in dogs
-Major public health significance: C. jejuni is most frequent cause of human bacterial diarrhea
-Diagnosis: direct microscopy (DCF stained smears), isolation on charcoal based selective medium
*interpretation of findings difficult: healthy animals can shed Campylobacter!!

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Lawsonia intracellularis

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-Slender, curved, Gram- rods
-CANNOT be grown on an agar plate
-Grown in enterocyte cell lines
-Porcine proliferative enteropathy: inflammation of terminal small and large intestine, chronic diarrhea to hemorrhagic enteropathy
-Diagnosis: immunofluorescent staining of feces or ileal mucosa, PCR
-Treatment/control: antibiotics, vaccine available; disinfection/cleaning after outbreak