Entomology and Vectorborne Diseases, USAMRU-K Sand Fly Surveillance in Kenya: the Need to Update Vector and Pathogen Distributions CPT Jeffrey Clark Elizabeth

Entomology and Vectorborne Diseases, USAMRU-K

Sand Fly Surveillance in Kenya: the Need to Update Vector and Pathogen Distributions

CPT Jeffrey Clark

Elizabeth Kioko

Unclassified


Disclaimer

The opinions or assertions contained herein are the private views of the author, and are not to be construed as official, or as reflecting true views of the Department of the Army or the Department of Defense.


Introduction

• Background– Leishmaniasis and known distribution

• Project overview• Snapshot of current results

– Leishmanial assay results– Phlebotomus orientalis in Kenya

• Conclusions

Acronyms: CL = cutaneous leishmaniasis VL = visceral leishmaniasis


Background

• Leishmaniasis is a diverse group of disease caused by Leishmaniasis is a diverse group of disease caused by protozoan parasites; protozoan parasites; Leishmania.Leishmania.

• Estimated 12 million people in 88 countries affected. Estimated 12 million people in 88 countries affected. – 350 million at risk.350 million at risk.

• Disease spectrum: cutaneous, muco-cutaneous and visceral Disease spectrum: cutaneous, muco-cutaneous and visceral leishmaniasis.leishmaniasis.

• Transmission is by infective bite of a female sand fly.Transmission is by infective bite of a female sand fly.--Phlebotomus Phlebotomus (old world) and (old world) and LutzomyiaLutzomyia (new world) (new world)

• Etiological agents found in Kenya.

– L. donovoni, L. major, L. tropica, L. aethiopica


Disease distribution: the literature

• Historical distribution of leishmaniasis in Kenya (Schaefer et al. 1994 based on Lawyer et al. 1989).


Disease distribution: the literature

VL: Wajir (Marlet et al. 2003)

Dadaab(Boussery et al. 2001)

Sudan border(Elnaiem et al. 1998)

Kekonyokie (Johnson et al. 1993)


Project Overview

• Sand fly collections from several regions in Kenya.– Over 200 trap sites to date.

• Subset of specimens from each trap mounted, cleared and identified.

• Specimens tested for infection with Leishmania spp. parasites.– Conventional/real-time PCR.


Trap Sites

• Originally focused on where CJTF-HOA assets were operating.

• Adding more sites to complete the risk picture.


Snapshot of Current Progress

• Over 3000 specimens identified

• Over 6000 tested for infection

• 14 pools tested positive with conventional PCR

• 4 Pools positive for L. major using RT-PCR probes (Wortmann et al. 2005).


Origin of L. major positive pools

=L. major positive pools

Isiolo Aug 08 Count of Spp Sub Site

Spp Korbessa Malkafunan Grand Total

P. orientalis 109 23 132 S. adleri 1 2 3 S. africanus 1 1 S. antennatus 2 2 S. clydei 5 26 31 S. graingeri 4 4 S. schwetzi 2 9 11 S. squamipleuris 8 12 20 Sergentomyia spp 1 6 7 Grand Total 126 85 211

Lamu Feb/Mar 09

Count of spp Sub site

spp Farm Grand Total

S. africana 5 5 S. antennatus 1 1 S. bedfordi 2 2 S. squamipleirus 30 30 Grand Total 38 38


Importance

• All L. major positive pools collected in non-endemic areas.– CL likely severely

underreported due to lack of morbidity & recognition

• The known Kenyan vector (P. duboscqi) has not been collected at these sites.– Multiple vectors?

• Bottom line: risk area for contracting CL in Kenya likely far more widespread than the literature indicates.


Sand flies & Visceral Leishmaniasis Risk

P. orientalis


P. orientalis distribution

• Historical P. orientalis reports: (Killick Kendrick et al. 1994)

– Wajir: (1943)

– Sericho: 3 specimens (1953)

– Tseikuru: 1 specimen (1956)

– Kekonyokie: 4 specimens (1993)

• To date (March 2009) 729 P. orientalis specimens identified

– 683 from Isiolo district• 621 (Aug 08)

• 62 (Mar 09)

– 46 from Tana River district• 0 (Jul 08)

• 46 (May 09)


Importance• P. orientalis is the main VL vector in Sudan and a major

vector in Ethiopia.– 1000 cases reported per year in Eastern Sudan and a recent outbreak

in Southern Sudan claimed 100,000 lives (Elnaiem et al. 1998).

• Ethiopia reports on average 2000 cases per year (Alvar et al. 2007).

• Kenyan outbreaks historically have consisted of 100-1000 cases over the last 60 years (Tonui 2006).– Only 2 outbreaks eclipsed 1000 cases in the 1950s– Known vector P. martini

• Bottom line: should P. orientalis become a major vector in Kenya outbreaks could become more widespread and severe.


Conclusions

• CL: Distribution of L. major may be more widespread than previously thought.– Cutaneous Leishmaniasis is likely a significant but

underreported problem.

• VL: P. orientalis, the major sand fly vector of VL in Sudan, is now present in large numbers in Kenya.– Unclear if this is a permanent or cyclical phenomenon.

– Important to note that we have not found sand flies infected with L. donovoni to date.


Next Steps

• Much work to be done before a reliable risk map for leishmanial disease can be developed for Kenya.– Continue sampling and expand coverage to areas where

historical data is lacking to include Tanzania and Uganda.

– Explore possible link between El Nino rains, severe drought, and VL outbreaks.

• Work to improve CL and VL risk estimates in Kenya


Acknowledgements

• Funding partners– GEIS

– NCMI

• KEMRI/USAMRU-K team– John Kamanza

– Nicholas Odemba

– Francis Ngere

– Santos Yawala

– Gladys Kerich

– Erick Oyugi


Questions?

Documents

Entomology and Vectorborne Diseases, USAMRU-K Sand Fly Surveillance in Kenya: the Need to Update Vector and Pathogen Distributions CPT Jeffrey Clark Elizabeth