German Federal Institute for Risk Assessment • Max-Dohrn-Straße 8-10 • 10589 Berlin, GERMANY • Phone +49 30-18412-0 • Fax +49 30-18412-99 0 99 • bfr@bfr.bund.de • www.bfr.bund.de/en
GERMAN
FEDERAL
INSTITUTE
FOR
RISK
ASSESSMENT Disease frequency of selected bacterial zoonoses in
small ruminants in Tana River County, Kenya
Martin Wainaina1,2,3, Johanna Lindahl3,4,5, Anne Mayer-Scholl1, Kristina Roesel3,
Deborah Mbotha2,3, Uwe Roesler6, Delia Grace3,7, Bernard Bett3, Sascha Al Dahouk1,8
1. German Federal Institute for Risk Assessment,Berlin, Germany, 2. Dahlem Research School of Biomedical Sciences, Freie Universität Berlin (FUB), Berlin, Germany,
3. International Livestock Research Institute,Nairobi, Kenya, 4. Swedish University of Agricultural Sciences, Uppsala, Sweden, 5. Uppsala University, Uppsala, Sweden,
6. Institute for Animal Hygiene and Environmental Health, FUB, Berlin, Germany, 7. Natural Resources Institute, University of Greenwich, United Kingdom, 8. RWTH Aachen University Hospital, Aachen, Germany
SAMPLE COLLECTION SITES
Bacterial infections are the leading causes of non-malarial fevers in Africa.
Brucellosis, leptospirosis,and Q fever are priority zoonoses in Kenya, but little
information on their epidemiology is available to date. Changes in land use such
as irrigation can influence the pattern of vector-borne viral and parasitic
diseases. Less is known about bacterial diseases.
Therefore, we implemented this longitudinal study by following up 316 small
ruminants from September 2014 to June 2015. Sampling was done in pastoral,
irrigated, and riverine settings in Tana River County. We aimed at estimating the
disease burden, disease frequency, and associatedrisk factors for both
exposure and seroconversion.
Sampling ecosystems:
1. Irrigated – Bura
irrigation scheme
2. Pastoral – Chifiri village
3. Riverine – Husingo
village
Irrigation may influence the occurrence of bacterial zoonoses such as C.
burnetii. However, we did not observe this for both Leptospira spp. and
Brucella spp. We also observed the possibility of prolonged periods of
transmission of Brucella spp. to humans and animals. Additionally, despite
determining prevalent leptospiral serovars by MAT, determining infective
serovars can only be proven by bacterial cultures due to paradoxicalreactions.
The high number of seropositive and seroconverting animals in the study area
shows the need for surveillance and control measures to reduce animal
disease burden and possible human exposure.
LABORATORY ANALYSIS
Serological testing:
1. Brucella spp. – Screening by ELISA and Rose Bengal tests. Confirmation by
complement fixation test
2. Coxiella burnetii – phase I & II ELISA test
3. Leptospira spp. – microscopic agglutination test (MAT)
Real-time PCR testing of serologically-positive animals
DATA ANALYSIS
First negative, later positive = seroconversion
First sampling time points:
1. Seroprevalence estimations
2. Risk factors for seropositivity
First time points varied
Seroconversions:
1. Survival analyses
2. Serological incidence rate estimations
Kenya with Tana River County in yellow
and households sampled as red dots
Distribution of seropositivity at first sampling time points
ONE HEALTH RELEVANCE
Martin Wainaina
markimwa@gmail.com ● Diedersdorfer Weg 1, 12277 Berlin ● Tel: +49 30 18412-24703
BACKGROUND
Leptospira spp. Coxiella burnetii Brucella spp.
positive/total positive/total positive/total
Total 50 /313 † 66/316 4/316
Irrigated 15/138 34/139 3/139
Pastoral 8/68 25/69 0/69
Riverine 27/107 7/108 1/108
Leptospira spp. Coxiella burnetii
positive/total positive/total
Total 27/263 ‡ 10/250 ‡
Irrigated 10/123 7/105
Pastoral 4/60 3/44
Riverine 13/80 0/101
Kaplan-Meier analyses: Differences in survival probabilities with time
(in months) were observed for Coxiella burnetii (p=0.012), but not for
Leptospira spp. (p=0.5)
PCR testing:
Three animals tested positive for Brucella spp. either consistently or
intermittently for entire study period. One animal was also positive for
C. burnetii at one time point. We detected no pathogenic leptospires.
Leptospiral serovars:
Serovar Ballum was the most prevalent. Evidence of paradoxical
reactions was also observed.
Ongoing: Estimation of seroprevalence and incidence rates using survey
methods. Risk factor analyses for both seropositivity and
seroconversion.
Distribution of seroconversions. We observed none for Brucella spp.
Animal metadata collected: species, age, sex, reproductive status
A. Coxiella burnetii B. Leptospira spp.
RESULTS
Time
† doubtful results excluded; ‡ total number depended on how many animals
tested negative from the beginning