Limpopo – another river to cross in controlling malaria

limpopo-river-crosses-4-countries.jpgThe countries of southern Africa are more often known for their HIV problems than for malaria, but as Korenromp and colleagues point out, “… in Botswana, Zimbabwe, Swaziland, South Africa, and Namibia, the incidence of clinical malaria increased by < 28% (95% confidence interval [CI] 14%–47%) and death increased by < 114% (95% CI 37%–188%) … due to high HIV-1 prevalence in rural areas and the locally unstable nature of malaria transmission that results in a high proportion of adult cases.” Three of these countries, South Africa, Botswana and Zimbabwe, along with Mozambique, lie along the course of the Limpopo River, where malaria is seasonal but endemic.

Interest in another larger river, the Zambezi, this year has drawn attention to the cross-border challenges to malaria control.  The Limpopo provides another key example of the disease that knows no borders.

limpopo-river-sm.gifThe Global Fund malaria overviews of these four Limpopo countries varies widely from 13,400 and 22,400 annual cases in South Africa and Botswana to 1.3m and 5m cases in Zimbabwe and Mozambique.  The latter two countries of course share the malaria endemic Zambezi watershed, while the former two do not even have a malaria grant from the Global Fund. And yet, malaria is endemic along two-thirds of its 1,750 kilometer long arc of a course that starts in South Africa, heads north, then northeast, east and finally south to empty into the Indian Ocean in Mozambique (as seen in the map from Encarta).

A recent study examining malaria in South Africa’s Limpopo Province found that the three eastern districts had the highest incidence over a ten-year period, and although the incidence appeared to be reducing, the authors cautioned that more understanding is needed about the nature of malaria in seasonal and epidemic-prone areas (Gerritson et al., 2007). They quote Cox et al., in calling for better estimates for malaria disease burden in countries where malaria epidemics occur to aid in better policy formulation, strategic planning and early warning measures.

The Limpopo experience stresses the importance of understanding both the epidemic nature of the disease and its interactions with HIV. Each river in malaria endemic regions may have its own lessons to teach, and we should be ready to learn.

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