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Emerging Infectious Diseases

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Volume 12, Number 10–October 2006

Perspective

Malaria Epidemics and Interventions, Kenya, Burundi, Southern Sudan, and Ethiopia, 1999–2004

Francesco Checchi,*† Jonathan Cox,† Suna Balkan,‡ Abiy Tamrat,§ Gerardo Priotto,* Kathryn P. Alberti,* Dejan Zurovac,‡¶# and Jean-Paul Guthmann*
*Epicentre, Paris, France; †London School of Hygiene and Tropical Medicine, London, United Kingdom; ‡Médecins Sans Frontières, Paris, France; §Médecins Sans Frontières, Geneva, Switzerland; ¶Kenya Medical Research Institute/Wellcome Trust Research Laboratories, Nairobi, Kenya; and #University of Oxford, Oxford, United Kingdom

Appendix

Additional Information on Climate and Other Possible Epidemic Determinants

We characterized climatic and ecologic conditions during each epidemic by using meteorologic indexes obtained by remote sensing (station data were incomplete or unavailable). Dekadal (10-day) rainfall estimates for July 1981 through December 2005 and normalized difference vegetation indexes for July 1995 through December 2005 were obtained at 8-km spatial resolution from the Africa Data Dissemination Service (http://igskmncnwb015.cr.usgs.gov/adds/index.php). Data for daytime and nighttime land-surface temperature (LST) were obtained through the Epidemio project (http://www.epidemio.info/index.php?section=homepage) for January 1995 through September 2005 at 2.5-minute spatial resolution. For each site, administrative boundaries were overlaid with remotely sensed datasets in a geographic information system with Arc/Info workstation software (version 8.1, ESRI, Redlands, CA, USA). We extracted summary statistics for each parameter and dekad (10-day period) and compared these with long-term averages for the same season. Our aim was to identify obvious climate anomalies either during or before the epidemics; therefore, we limited ourselves to descriptive analysis rather than establishing causality between climate and epidemic onset.

Climate

In Kisii, estimated rainfall from September 1998 through January 1999 was 59% below the expected (536 mm), according to the 10-year rainfall estimate dataset. The long rains of March and April 1999 (1 month before epidemic onset) were unusually heavy (704 mm compared with a long-term average of 401 mm). Land-surface temperature for 1998 and 1999 generally fell within the normal range from 1995 through 2005, except during the preepidemic period, November 1998 through February 1999, when average maximum land-surface temperature (33.1°C) was 14% higher than the corresponding long-term average.

In Kayanza, unusually heavy rains occurred between the second dekad of February and the first dekad of April 2000 (460 mm vs. a 1995–2005 average of 304 mm), and an additional peak occurred during the last dekad of May (137 mm vs. 22 mm), 3 months before epidemic onset. Data from neighboring Ngozi Province suggested a rise in temperature (1), but no land-surface temperature anomalies are evident for this period.

In East Wollega Region, including Gutten Locality, 2002 and 2003 show similar drought patterns from the last dekad of April to the end of May (61 mm and 33 mm, respectively, compared with an average of 192 mm from 1995 through 2005), followed by above-average rainfall throughout June (preepidemic month), especially in 2003. Annual rainfall estimate averages for 2001 through 2003 (962 mm) seem markedly drier than preceding years (1996–2000, 1,431 mm). Drought conditions in the 2003 preepidemic months are also captured by mean normalized difference vegetation index data (0.38 from the last dekad of April to end of June 2003 vs. 0.5 average for the same period [1995–2005]). No land-surface temperature anomalies were apparent.

In Damot Gale, annual rainfall estimate averages from 2001 through 2003 (940 mm) were lower than for 1996 to 2000 (average 1,204 mm). In the preepidemic months of April, May, and June, rainfall estimate was 268 mm in 2002 (preepidemic year), compared with 376 mm in 2003 (epidemic year) and the 1996–2004 mean of 416 mm. land-surface temperature for this period seemed within normal range.

In Aweil East, 2000–2002 was relatively dry, particularly in 2002 when annual rainfall estimate was 40% below the long-term average (963 mm). Rainfall totals for 2003, however, were ≈20% higher, with a particularly rainy season leading up to May (preepidemic month). Land-surface temperature data suggest that temperatures in the second half of 2002 and first part of 2003 were within normal range, but during the epidemic period itself (June–November), mean maximum land-surface temperature (34.1°C) was 3.5°C below the period average.

Other

All sites but Kenya were affected by conflict and displacement. Burundi's and southern Sudan's conflicts had lasted 7 and 20 years, respectively; Aweil East's population had been repeatedly displaced by militia incursions. Both Gutten and Damot Gale had received immigrants resettled from drought-stricken, nonmalarious areas.

Parasite resistance to first-line treatments was high in Kayanza (chloroquine [CQ]), Sudan (CQ), and Ethiopia (sulfadoxine-pyrimethamine [SP] at the peripheral level and the combination CQ+SP in better-equipped centers). SP was prescribed as first-line in Kenya and Ethiopia (primaquine coadministration was mandated by Ethiopian guidelines, but this drug was not supplied to Gutten and Damot Gale during the epidemic).

Appendix Reference

Bonora S, De Rosa FG, Boffito M, Di Perri G, Rossati A. Rising temperature and the malaria epidemic in Burundi. Trends Parasitol. 2001;17:572–3.