jacksonville, fl 9 – 12th february 2004 triennial gis symposium mapping of potential habitats for...

9 – 12th February 2004 Triennial GIS Symposium Jacksonville, FL

Mapping of potential habitats for vectors of African Tick Bite Fever (ATBF) in the

Maasai Mara region of Kenya1C. Tungwony, 2M. Sardelis, 1S. Kasili, 1V. Sherwood, 1J Indiazi,

1S. Kelempu, 3A. Anyamba, 4A. Azad, 4K. Macaluso1 U.S. Army Medical Research Unit – Kenya 2 Uniformed Services University of Health Sciences 3 NASA 4University of Maryland


African Tick Bite Fever (ATBF) is a spotted fever caused by Rickettsiae africae and vectored by ticks

Rickettsiae africae was first reported in ticks in Maasai Mara, in 2003, following fatal tourist case

Maasai Mara is a national game reserve and popular tourist destination

Maasai Mara is characterized by diverse vegetation

GIS employed to help identify prevalent tick habitat

Introduction


The Maasai Mara Game Reserve and adjacent Conservation area totals 750 square miles

It is 2000m (5,200 ft) above the sea level

Inhabited by the Maasai community (livestock keepers)

It is characterized by shrubby grassland and riverine forest

Study Area: People and Vegetation

Maasai Mara National Game Reserve


Study Area: Rainfall and Temperature

Average Monthly Temperature

0

5

10

15

20

25

30

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Tem

per

atu

res

(o

C)

Maximiun Minimum

Average Monthly Rainfall

0

20

40

60

80

100

120

140

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

Ra

infa

ll (

mm

)


Six Different vegetation types selected for tick collection

50 collection sites

GPS recorded locations of each collection site

Three collections: April, September, December (2002)

Collection methods: drags and picking off animals

Tick Collection


Sept 2002Apr 2002

1. LANDSAT images (Enhanced Thematic Mapper, Satellite 7) from USGS

Vegetation Classification – 3 Steps


2. Image processing

- Export to Idrisi 32

- Georeference

- Subset

- Natural Color composite

- Overlay GPS points

April



3. Supervised Classification (Maximum Likelihood) used to identify land cover types

September


April


Vegetation Classes


Results: April

KeyApril Collection

Village-density

1 - 10

11 - 20

21 - 40

40 - 60

60 - 100

1

2

3

4


Results: September


Results: December


Results: Combined


Any stage

0

20

40

60

80

100

FOR GA GG TG TG&B ALL

% o

f si

tes

po

siti

ve

Sep Dec Larvae

0

20

40

60

80

100


% o

f si

tes

po

siti

ve

Sep Dec

Nymphs

0102030405060708090

100


Habitat

% o

f si

tes

po

siti

ve

Sep Dec

Adults

0102030405060708090

100


Habitat

% o

f site

s po

sitiv

e

Sep Dec

Adult ticks were only collected in December and were Observed at all other habitats.

Summary of locations and life stages.

Ticks collected in all habitat types except Grazed grass

For habitats positive for ticks larvae was likely to be Encountered in other habitats.

Fewer Nymphs were collected compared to Larvae in all habitats

Summary


Density: Cattle, Goat and Sheep

KeySheep & Goat

0 - 41

42 - 137

138 - 258

259 - 500

501 - 1100

Cattle

0 - 26

27 - 83

84 - 180

181 - 350

351 - 600


Vegetation Index

• High index values characterizes dense vegetation

April

September


Conclusion

GIS can help visualize risk areas and, with identification of tick populations, map areas for control programs

Identify spatial and temporal relationships important in disease transmission

Model risk of contracting vector borne diseases

The study has indicated that this area is rich ground for further studies of ATBF


• Tanser, F.C; and Le Sueur, D. (2002) The application of geographical information systems to important public health problems in Africa. International journal of health geographics. Available from; http://www.ij-healthgeographics.com/content/1/1/4

• Lobitz, B. et al (1999) Climate and Infectious diseases: Use of remote sensing for detection of vibrio cholerae by indirect measurement. John Hopkins University

• Anno, S. et al (2000) Analysis of relationship between Anopheles subpictus larval densities and environmental parameters using remote sensing (RS), a global positioning system (GPS) and geographic information system (GIS). Kobe J. Med. Sci. 46, 231/243.

• Macaluso, K.R. et al (2003) Spotted Fever Group Rickettsiae in ticks from the Maasai Mara Region of Kenya. The society of Tropical Medicine and Hygiene. Am J. Trop. Med. Hyg., 68(5), 2003, PP. 551-553

• Rutherford, S.J. et al (2002) Spotted fever rickettsioses in Kenya (un published data)

References


Kenya Medical Research Institute

Mara Safari Club

Kenya Meteorological Department

International Livestock Research Institute

U.S. Geological Survey

Assaf Anyamba & Ed: GSFC - NASA

Acknowledgements

jacksonville, fl 9 – 12th february 2004 triennial gis symposium mapping of potential habitats for...

Documents

triennial gis symposium

temperature slide

combined slide

diverse vegetation gis

animals tick collection

university of maryland

usgs vegetation classification

maasai mara game reserve