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

2

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

Presentation Outline

3

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

4

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

5

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

6

Brucella in Africa Wildlife

Reservoirs of Brucellosis

Bovidae*African buffalo*BushbuckEland ImpalaKobLechwe

Bovidae (cont).WaterbuckWildebeeste

Others: GiraffeZebraHippopotamus

* - high potential for reservoir status

7

Primary Routes of Shedding for Brucellosis Urogential system

Uterine discharges: HIGHLY INFECTIOUS MilkSemen

Shedding not constant, consistent

Routes of Transmission

8

Routes of Transmission for Brucellosis Ingestion of contaminated materialsContact through

Mucous membranes Open woundsConjunctiva

Vertical transmission – questionable

Routes of Transmission

9

SheddingAbortion – reproductive fluidsMilk

After abortionContinue through life of the animal

Transmission Ingestion of milk Ingestion of contaminated materials

Maintenance of Brucellosis

10

Steps for conducting outbreak investigationsEstablish and verify existence of outbreak

Reported casesRoutine surveillance

Define and identify casesConsistent case definitionLaboratory confirmation

Outbreak Investigations

11

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

12

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

13

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

14

1. Brucella spp. have many domestic and wildlife reservoirs

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

Summary

15

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.)

16

THANK YOU!