Presentation at 3rd GRF One Health Summit 2015 Session Wildlife, Livestock and Pets

1. Landscape heterogeneity & Taenia spp.
distributions: evidence of environmental
influences on disease transmission
Dr Nicola Wardrop

2. Pork Tapeworm
Taenia solium

3. Background
• Scarcity of data
– Burden not well understood
• Increasing incidence
– Growing pig populations in many regions
• Common in many developing countries
– Poor meat inspection practices
– Poor sanitation
– Pig keeping practices
– Potential environmental influences?

4. Background
• Previous detection of spatial clustering
– Possible environmental drivers?

5. Background
Potential environmental influences
• Egg survival/viability in environment
dependent on
– Temperature
– Humidity
• Eggs can be moved via rivers, flood waters etc
• Exposure of humans/pigs to eggs may vary in
different landscapes

6. Background
Potential environmental influences
• Transmission cycle similar to soil transmitted
helminths (e.g. hookworm, whipworm)
– Environmental drivers widely studied
• Rainfall
• Temperature
• Landcover
• Soil type
• Elevation
• Vegetation
Potential for similar
relationships with
tapeworm distributions

7. Aims
Assess the potential role of environmental
factors in the spatial distribution of human
and pig cyticercosis

8. Methods - data
Study area
• Area of (mainly rural) W Kenya
• Subsistence farming
• People live closely with
livestock

9. Methods – data
• Household level survey (clustered
sample design)
• Questionnaires administered for
each unit (HH, human, pig)
416 households
2113 humans
(blood &
stool)
93 pigs
(blood)

10. Methods - analysis
Regression analysis
– Assess importance of individual and household
level factors (including environment)
– Multilevel modelling

11. Results
Human seroprevalence:
6.6% (95% CI 5.6%–7.7%)
Porcine seroprevalence:
17.2% (95% CI 10.2%–26.4%)

12. Gender
Female ref
Male -
Education
None ref
Primary -
Secondary -
Above -
Well water
No ref
Yes +
Environment
Flooding crops &
grassland
+
Precipitation -
Human cysticercosis
Behaviour and
exposure
Related to knowledge
& practices
Contamination
Egg survival or
probability of exposure

13. Breeding sows
Male ref
Non breeding sow -
Breeding sow +
Environment
Flooding crop &
grassland
+
Porcine cysticercosis
Length of exposure
Egg survival or
probability of exposure

14. Discussion
• Egg survival/viability depends on
– Temperature
– Humidity
• Infection probability depends on
– Exposure
• Egg presence attenuated by
– Flooding
Can be influenced by
vegetative cover
Potentially influenced
by land cover
Influence of flooding
land cover class

15. Discussion
Pig movements
• Spend on average 47% of time outside of
home and utilise ~ 1 km2
– Exposure may occur outside of the home
• Pork consumed often comes from outside the
home
Human movements
• Less restricted than pig movements

16. Limitations
• Small sample size for pig infections
• Variable sensitivity/specificity of assays
• Problems with taeniasis results
• Movements not considered

17. Discussion & conclusions
Evidence of environmental influences
Scope for future research into environmental
drivers of Taenia spatial distributions

18. Acknowledgements
Authors: Nicola A. Wardrop, Lian Thomas, Peter M. Atkinson,
Elizabeth A Cook, Will De Glanville, C Njeri Wamae, Eric M. Fèvre
Medical Research Council
Wellcome Trust & BBSRC Contact:
Nicola.Wardrop@soton.ac.uk
@DiseaseMapper
www.nicolawardrop.co.uk
Thank you for
your attention!