Malaria is a major public health problem in most countries of Africa. Over the past two decades, epidemics of plasmodium falciparum malaria often with high case fatality rates have been common in areas of unstable transmission in Africa. A large number of epidemics were reported in highland areas in East and Great lakes countries during the period 1985-1995.
In 1997-1998 when all countries in the sub-region Africa experienced malaria epidemic due to El Nino, Southern Oscillation (ENSO) now occurs at least yearly in several East Africa and Great lakes countries during the malaria transmission season.
Malaria epidemics occur in the western highlands, the arid and semi-arid lowlands of northern epidemiological zones in Kenya. The epidemics are associated with unusual climatic conditions especially rainfall and other factors such as suitable temperatures that favour breeding and longer survival of the malaria vectors.
Prediction methods for epidemics to alert implementers to either undertake epidemic prevention measures like Indoor Residual Spraying (IRS) or prepare to control the epidemic are still at developmental stages. Resources are scarce in developing countries finding it difficult to keep buffer stocks especially drugs to respond to outbreaks when routine services are without.
Once the epidemic has been detected the only cost effective measure is to institute case management activities. In the highlands, malaria prevalence above the epidemic threshold level last 4-6 weeks. Since the year 2000, major epidemics have been observed in the malaria epidemic prone districts. Malaria epidemics are some of the most serious public health emergencies with which health officials have to deal.
Malaria epidemics occur unexpectedly in areas where the health system is often unprepared to deal with the problem. They affect highly vulnerable populations (all age groups) with only limited immunity to malaria. This situation is exacerbated by public outcry and intense political pressure to intervene rapidly and decisively.
Epidemic conditions take few weeks to build up allowing time for preventive action. When it occurs, it takes several weeks to reach to its peak, effective control maybe possible if implemented in the early stages of development. The most important factor in reducing the impact of an epidemic is a timely response implementation of effective control measures as soon as it has been detected.
The longer an epidemic goes undetected with no measures for its control, the higher the cost of morbidity and mortality (Delacollette, 1999). Control measures are inherently costly. Implementation of control measures within a short delay after the epidemic has been detected might have some benefit. The maximum impact is however, when measures are implemented at the very early stages, usually within two weeks of onset, when deaths can be minimised.
Epidemics the western highlands
Malaria upsurge is an annual event in the western highlands of Kenya which generally occurs between June and August. In some zones, the upsurges outdo the epidemic threshold. Widespread outbreaks of malaria epidemic involving the western highlands occur periodically and have been recorded between 1918 and 1950s when epidemic malaria was a scourge of the economically important Kenyan highlands.
Between 1950s and late 1980s the highlands enjoyed a free malaria epidemics period. This was as due to WHO driven eradication programme of the late 1950s which was terminated in the late 1960s (Republic of Kenya, MOH, 2001).
The most spectacular observed event in many occasions had been a dry spell preceding the outbreaks. The long rain season starts in April or May but the heat wave prevailing during the dry spell persists up to June or July. This is the most important factor that facilitates massive build up of vector density thus increasing the vectorial capacity.The increased transmission level of malaria in an area of susceptible population usually results in malaria epidemics.
The table below shows the association of anomalous weather conditions with malaria epidemics in Nandi District, Kenya. (Correlation of a 10-year retrospective data study- DOMC/WHO 2002)
|Year||Epidemic||Unusually High Temperature||Unusual Rainfall||Unusual Humidity|
Epidemics in the northern arid, semi-arid lowlands
Kenya northern arid and semi-arid lowlands are low malaria transmission areas. Malaria epidemics occur only during prolonged periods of flooding as observed during the EL Nino in 1998.
The temperatures are always right for the malaria vectors to breed when water is available and prolonged flooding makes such conditions to prevail. Other periods have short rain spells that do not enable build up of malaria vectors to levels that can result in malaria upsurge reaching the epidemic threshold proportions.
The national policy advices IRS in the epidemic prone Western highlands of Kenya in order to prevent the malaria upsurge.
Malaria epidemic control in Kenya
This will either lead to early recognition of epidemics and immediate implementation of control measures or the implementation of preventive measures before the epidemic starts. These efforts will improve the management of epidemics and reduce morbidity and mortality during epidemics.
|Rift Valley||West Pokot|
Due to the heavy resource needs for the IRS campaigns, the Government of Kenya opted to scale up coverage in the 16 counties. The initial approach was to prioritise high risk areas within the counties and eventually progressively spiral to the entire counties. Due to increased support from the WHO, Global Fund and USAID, tremendous progress in terms of coverage has been realised. This is depicted in the IRS figure alongside.