Epidemiology of brucellosis in ruminants: the basics and dynamics of the disease

Epidemiology of Brucellosis in Ruminants: the Basics and Dynamics of the Disease

Professor John B. KaneeneDVM, MPH, PhD, FAES

Center for Comparative EpidemiologyMichigan State University

Workshop: An Integrated Approach to Controlling Brucellosis in Africa, Addis Ababa,

29-31 January 2013

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Basic Epidemiology of Brucellosis Reservoirs and Routes of Transmission Outbreak Investigations Surveillance and Control Programs Summary

Presentation Outline

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Host-Agent-Environment Host species: most mammals

Hoofstock: cattle, goats, sheepSwine and other mammals

Agents: Brucella spp.Host preferences, but not specific

Environmental conditions:Allows direct contact with materials contaminated

when Brucella are shed

Basic Epidemiology of Brucellosis

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Reservoir hosts:Host allows pathogen to survive, grow, and

multiply without compromising significantly reproduction and survival

Maintains infection within their species population

Capable of transmitting infection to other species

Reservoirs of Brucellosis

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Wildlife Reservoir of Brucella in Africa

Primary Livestock Reservoirs of Brucella

Reservoirs of Brucellosis

B. abortus:Cattle, Buffalo

B. melitensisGoatsSheep

B. abortus:African Buffalo

B. ovisSheep

B. suisSwine

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Brucella in Africa Wildlife

Reservoirs of Brucellosis

Bovidae*African buffalo*BushbuckEland ImpalaKobLechwe

Bovidae (cont).WaterbuckWildebeeste

Others: GiraffeZebraHippopotamus

* - high potential for reservoir status

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Primary Routes of Shedding for Brucellosis Urogential system

Uterine discharges: HIGHLY INFECTIOUS MilkSemen

Shedding not constant, consistent

Routes of Transmission

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Routes of Transmission for Brucellosis Ingestion of contaminated materialsContact through

Mucous membranes Open woundsConjunctiva

Vertical transmission – questionable

Routes of Transmission

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SheddingAbortion – reproductive fluidsMilk

After abortionContinue through life of the animal

Transmission Ingestion of milk Ingestion of contaminated materials

Maintenance of Brucellosis

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Steps for conducting outbreak investigationsEstablish and verify existence of outbreak

Reported casesRoutine surveillance

Define and identify casesConsistent case definitionLaboratory confirmation

Outbreak Investigations

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Steps for conducting outbreak investigationsEpidemiological Investigation

Data collection: demographics, clinical data, risk factors

Examination of cases and premisesCharacterize outbreak

Populations affected Geographic extent Dates and Trends over Time

Outbreak Investigations

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Steps for conducting outbreak investigationsFormulate & evaluate hypotheses

Source of infection Primary case Imported cases

Modes of Transmission and Exposures ‘Abortion storms’ Venereal exposure

Outbreak Investigations

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Outbreak ControlControl measures

Control source of pathogen – Identify infected animalsInterrupt transmission – Quarantine, cullingControl host response to exposure – vaccination

Monitoring to evaluate effectiveness of control measures

Directed Surveillance Passive and Active Surveillance

Outbreak Investigations

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1. Brucella spp. have many domestic and wildlife reservoirs

2. Outbreak Investigation is an important tool for studying disease dynamics

Summary

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3. Establishing surveillance systems is a key to monitoring disease status and planning for control measures

4. In both outbreak investigation and surveillance, use of appropriate diagnostic tests is critical

Summary (cont.)

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THANK YOU!