Malaria is a parasitic disease caused by an obligate intracellular protozoan of the genus Plasmodium. The disease is systemic, acute and sometimes severe,it is usually characterised by shivering, chills alternating with fever, headache, nausea and sometimes vomiting. After an interval free of fever, the cycle is repeated either daily or every third day depending on the malaria parasite species.
Malaria is the one of the leading causes of morbidity and mortality in Kenya. It accounts for 15% of all out-patient attendance in the country's health facilities admissions (DHIS 2015). However, there has been a steady decline of malaria cases in the last five years (DHIS 2015). In Kenya, malaria distribution is not uniform due to geographical differences in altitude, rainfall and humidity.
These geographical factors influence the transmission patterns as they determine the vector densities and biting intensity. The higher the ambient temperature, the shorter the sporogonic cycle of the mosquito parasite hence shorter duration of the gonotrophic cycle.
There are four various human plasmodium species that occur in Kenya. They include; plasmodium falciparum, malariae, ovale and vivax. Plasmodium falciparum accounts for 98% of all malaria infections and it’s the most severe.
The principal vectors of malaria parasites in Kenya are members of the Anopheles gambiae complex and An funestus. The An Gambiae complex species found in Kenya are; An gambiae s.s., An Arabiensis that is usually predominant during and after the rainy seasons, An merus, which is mainly restricted to the coastal strip and An funestus exist in low densities throughout the year.
These vectors are among the most efficient in the world as they feed predominantly on humans. Although a decrease in susceptibility to permethrin was reported from an area of insecticide treated bed nets in western Kenya in 1994, these malaria vectors are susceptible to all pyrethroid insecticides.
Several studies that have been carried out on malaria vectors in Kenya have shown that they are indoor feeders. They prefer human blood, apart from An arabiensis which prefer animals and some feed outdoor. The malaria vectors rest indoors after feeding.
The biting activities for most An ophelines occur between 20.00 hours and 06.00 hours, with a peak biting rate from midnight to 04.00 hours when most people are in bed and are susceptible to insecticide treated bed nets. Based on these biological characteristics, the Kenyan Government has promoted the use of insecticide treated bed nets as the main malaria control intervention measure.
Malaria is the one of the leading causes of morbidity and mortality in Kenya. It accounts for 15% of all out-patient attendance in the health facilities admissions (MOH, DHIS 2015). However, there has been a steady decline of malaria cases in the last five years (MOH, DHIS 2015).
Kenya has four malaria epidemiological zones. They include:
a) Endemic zones
Areas where malaria is present have altitudes ranging from 0 to 1300 meters, these areas are around lake victoria in western Kenya and in the coastal regions. Rainfall, temperature and humidity are the determinants of the perennial transmission of malaria. The vector life cycle is usually short with high survival rate due to the suitable climatic conditions. Transmission is intense throughout the year with annual entomological inoculation rates between 30 and 100.
b) Seasonal transmission zones
These epidemiological zones are found in the arid and semi-arid areas of northern and south-eastern parts of the country. They experience short periods of intense malaria transmission during the rainy seasons. Temperatures are usually high and water pools created during the rainy season provide the malaria vectors breeding sites. Extreme climatic conditions like El Niño and southern oscillation lead to flooding in these areas thus epidemic outbreaks with high morbidity rates due to low immune status of the population.
c) Epidemic zones
Malaria transmission in the western highlands of Kenya is seasonal, with considerable year-to-year variation. The epidemic phenomenon is experienced when climatic conditions favour sustainability of minimum temperatures of around 1800C. This increase in minimum temperatures during the long rains period favours and sustains vector breeding resulting in increased malaria transmission. The whole population is vulnerable and case fatality rates during an epidemic can be up to ten times greater than what is experienced in regions where malaria occurs regularly.
d) Low risk zones
These zones cover the central highlands of Kenya including Nairobi. The temperatures are usually low to allow completion of the sporogonic cycle of the malaria parasite in the vector. However, with increasing temperatures and changes in the hydrological cycle, there is likelihood of increased vector breeding areas and new areas getting vulnerable.
There has been a series of such epidemics in Kenya's highland region. A significant adult and child mortality was reported in 1988, 1990, 1994, 1999 and 2002 by the Ministry of Health Annual Reports.
Malaria control activities were undertaken in Kenya between 1955 and 1974 with the advent of DDT as a residual insecticide and a number of antimalarial drugs such as chroloquine and pyrimethaine. These efforts were hampered by a number of factors. They include:
The development of insecticide resistant vectors.
Parasite resistance to antimalarial drugs.
Inadequate national resources for sustaining vertically organised malaria control programmes.
Attitudes of the local population towards malaria control.
A high degree of malaria endemicity encountered in most areas of the country.
In 1978, the WHO assembly approved a malaria control strategy based on the principles of Primary Health Care (PHC). According to the PHC approach, large vertical malaria control programmes were replaced by community based programmes integrating other aspects of PHC with active community participation.
It was accepted that malaria eradication was not a feasible option for many parts of Sub-Saharan Africa such as Kenya. Emphasis was placed on control strategies which could be effective in reducing morbidity and mortality.
After the malaria eradication era of 1955-1974, the Kenyan government re-oriented it’s malaria control strategies. The country adaptation prompted diagnosis and adequate treatment of the disease as the basis for malaria control, with the aim of preventing morbidity and mortality due to malaria.
The emergence of drug-resistant plasmodium falciparum, particularly to chloroquine, made this method difficult since treatment had to be done with more expensive or more toxic antimalarial drugs. In 1998, the country changed her treatment policy from chloroquine to SP.
Realising that malaria was becoming increasingly difficult to manage and following WHO recommendations for tropical countries affected by malaria to formulate their own malaria control strategies. The Kenyan government launched a five year National Plan of Action for Malaria Control in 1994. The objective of the plan was to develop an infrastructure that would ensure access to malaria prevention and curative services to those at risk with the aim of substantially reducing illness and death.
The specific objectives of the plan, among others, were to improve and sustain services within the community for reducing malaria morbidity and mortality, and to co-ordinate and focus the malaria control efforts of ministries, divisions, international agencies and the private sector in recognising malaria as a national health problem.
National malaria control program was further strengthened by the interest generated by the Global communities, with the introduction of Roll Back Malaria (RBM) initiative by WHO. In line with RBM movement and to co-ordinate partners, the Kenyan Government created Division of Malaria Control, now NMCP, within the Ministry of Health a commitment to reducing the malaria burden in Kenya.