brucellosis in cattle, sheep & goats: fundamentals of

Brucellosis in Cattle, Sheep & Goats:

Fundamentals of surveillance and eradication programs

B. Garin-BastujiEU / OIE & FAO Reference Laboratory for Brucellosis

ANSES – Maisons-Alfort, France

Thailand-Japan Conference on Animal HealthThe 25th Year Anniversary of National Institute of Animal Health

Rama Gardens Hotel, Bangkok, ThailandMay 30-31, 2012

1

Bovine brucellosisNever reported EradicatedInfected Reported in the past

Data not available

3

Sheep & Goats brucellosisNever reported EradicatedInfected country Reported in the past

Data not available

4

Porcine BrucellosisNever reported

Infected countries

Infection reported in the past

Data not available

5

Human brucellosis global incidence

Incidence <2/millionIncidence >2/million Data not available

Incidence >50/million

Epidemiology & diagnosis of Brucellosis….

�Key elementsfor a sound strategy…

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Epidemiology of Brucellosis….

�Brucellosis is a "multi-species"infectious disease…

� different animal species� different Brucella species

…..to be considered

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B. melitensis

B. abortus

B. suis

Wild Ruminants, Rodents, Carnivores

Swine

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�Cattle, sheep, goats or pigs,.. …and wildlife

� frequently in contact…in many areas

Epidemiology of Brucellosis….

Thailand-Japan Conference on Animal Health -25 th Anniversary of NIAH, Bangkok, Thailand - May 30-31, 2012 9

Epidemiology of Brucellosis

�Abortion is the main sign of brucellosis…

�But, most infected females give birth normally ...

�In both cases, huge and durable excretion of Brucella

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�Survival of Brucella out of their host is long (compared with most other non-sporing pathogenic bacteria, under suitable conditions)

� Brucella may survive on / in many materials

Epidemiology of Brucellosis

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�Brucella are excreted primarily in:– Abortion & normal birth materials

– Vaginal secretions– Semen

– Milk and colostrum

Epidemiology of Brucellosis

Thailand-Japan Conference on Animal Health -25 th Anniversary of NIAH, Bangkok, Thailand - May 30-31, 2012 12

Entry point Mucous membranes & skinConjunctivae, nasopharynx & respiratory tract, oral route, genitalia

�Vertical transmission (in utero): congenital infection

�Horizontal transmission– Direct

Infected aerosolsConsumption (or licking) of infected materials and milkContactSexual transmission

– Indirect (water, manure, materials, shoes,...)

Epidemiology of Brucellosis

Transmission (in animals)

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Neighbouring /transhumance

Purchase

Resurgence(partial depopulation)

Transmission away(Water, manure, materials, shoes, vehicles)

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Epidemiology of Brucellosis….

�Epidemiology of Brucellosis is complex…

�Lots of transmission routes, most of them being almost impossible to control…

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Diagnosis of Brucellosis….

�No single test able to…– identify all infected animals, or

– certify all free animals

�Tests repetitions needed

�Tests associations (parallel/series), modify considerably the results predictive values (-ve/+ve)

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Diagnosis of Brucellosis

�Serological tests– Early,sensitive but low specificity (RBT/FPA))– Sensitive but low specificty (iELISA)– Late, more specific but less sensitive (CFT)– Highly specific but lower sensitivity (cELISA)– Highly sensitive/specific (iELISA on milk, but..)≠ tests: ≠ antibodies detected

�Cell tests: BST (highly specific, but..)

� Frequent discrepancies between tests� Associations usually needed� Predictive values (-ve/+ve) linked to prevalence.

� Choice of tests and interpretation should always be based on epidemiological reality.

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Epidemiology & diagnosis of Brucellosis….

�Brucellosis is a herd/flock disease…

– the epidemiological unit is the herd , the flock or the group including all epidemiologically-related sensitive animals

– the individual prevalence has no significancefor control monitoring

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Brucellosis Control /eradication strategies ….

�Tools &strategies…

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Control/elimination of animal brucellosis: the tools

�Test and isolation/slaughter– Partial or full depopulation

� Control of animal movements� Vaccination

…and adequate– Political will– Budget– Vet. Services / Lab. infrastructure– Animal/herd identification– Good quality vaccines

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Vaccination (Rev.1 & S19)�Vaccination increases resistance to infection and decreases

abortion risk– Thus, decreases the spread of infection– Thus, decreases individual and herd/flock prevalence– Thus, decreases incidence in human populations– But,

� insufficient on its own to eradicate� vaccine-induced serological/cell-immune reactions

�Sub-cutaneous or conjunctival route at standard dose– Cattle (females): S19

• 3-6 months SC 5-10x1010 CFU/dose

• Adults SC 0.3-3x109 CFU/dose (non pregnant, lactating or late pregnancy)

• Both CR 5-10x109 CFU/dose (twice)

– Sheep & Goats: Rev.1• 3-6 months SC 0.5-2x109 CFU/dose

• Both CR 0.5-2x109 CFU/dose (non pregnant, lactating or late pregnancy)

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RB51 Vaccine in Cattle (Moriyon et al. Vet. Res. 2004)

• Sub-cutaneous route (10-30 x109/ dose)• Increasingly used in place of S19• Effectiveness is much debated• Experiments and field trials:

– Some better than S19– Other:

• reduced doses: ineffective• full doses: only partially effective• or RB51 less effective than S19 against severe

challenges.• other observations suggest that RB51 is ineffective

when prevalence is high. • RB51 is not useful in sheep and evidence in goats is

preliminary and contradictory. • Azores: effective only when vaccine coverage and

eradication scheme fully & duly appliedThailand-Japan Conference on Animal Health -25 th Anniversary of NIAH, Bangkok, Thailand - May 30-31, 2012 22

Brucellosis Control /eradication strategies ….

�Which tools…Which strategy…

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Preliminary considerations

The epidemiological situation is almost never homogeneous in a given country/region

Different epidemiological / livestock contextswithin a country/region

�

Different & adaptedcontrol / eradication strategies

to be implemented�

Primary goals of a control programme:Knowledge of situation & definition of Epidemiological units of intervention

Thailand-Japan Conference on Animal Health -25 th Anniversary of NIAH, Bangkok, Thailand - May 30-31, 2012 24

Strategy / objectives

� First objective in endemic areas� Control of the infection

� Final objective � Eradication

� Mid / short-term objective �Regularly decrease the prevalence

�Progressive strategy

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Decision tree for brucellosis control in animals

test/slaughterCombined young animal

vaccination and test/slaughter

high prevalence Intermediate prevalence Low prevalence

Is brucellosis present in a certain area/country?

Yes

Are there adequate means / expertise / vet. services?

Mass vaccination

NoYes (survey/prevalence/epidemiological units)

NoSurveillance/test-and-slaughter/

movement control

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In conclusion….

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Control, surveillance & Eradication of Brucellosis…

�Epidemiology is the main key…– A sound knowledge of the situation is required before

deciding of a strategy– Adequate epidemiological parameters are required for

evaluating the results and monitoring the program…– Changes in strategy should always be based on

epidemiological evidences

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Control, surveillance & Eradication of Brucellosis…

�Diagnosis is the 2nd key…– Tests associations (series or parallel)

� to increase the result predictive values

– Test result interpretation…always in relation with: • risk-factors• status of the herd, the area, the country

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Don’t forget the iceberg!

Diagnostic testsVaccines

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Thanks for your attention…

Acknowledgments: Dr. Anastasios MINAS (Greece) for the Brucellosis Global status maps

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