The latest findings from the “Research on Climate and Malaria” show that uncharacteristically for an area in the south, Kgatleng District is prone to this disease. Radithupa Radithupa, who conducted this particular aspect of the study, says that the district has suitable humidity (80 percent), suitable temperatures (18 degrees Celsius minimum and 32 degrees Celsius maximum) and suitable rainfall (400 millimetres).
He explains that malaria needs minimum temperatures of 18 degrees Celsius and maximum of 32 degrees Celsius to breed and that an accumulated rainfall total of 400 mm is likely to bring about an epidemic. In Botswana, incidences of malaria peak during the months of March and April after a two-month lag during the malaria vector populations would have been breeding.
Radithupa, a principal meteorologist at the department of meteorology who is also a Btv weather presenter, says that colleagues that he interacts with professionally and those he is involved with in the study confirmed that Kgatleng is indeed prone to malaria.
“Kgatleng has some significant incidences. With rainfall and maximum temperature and the high humidity, it becomes suitable. There could also be a local influence from the Notwane River that is always flowing and providing a good environment for the vector. The other interesting place to analyse in detail is Bobirwa, which also has good correlations with rainfall and temperatures,” he says.
This research is ongoing and has been narrowed down to districts. It was this refined focus that revealed the uniqueness of Kgatleng District vis’ a vis’ its suitability for malaria. All told, there are 17 malaria districts that have been mapped for research.
Malaria is mostly prevalent in the northern districts. The districts of Chobe, Gumare, Ngami, Tutume, North-East and Boteti account for 95 percent of the cases and incidence on average. Of these districts, the southern-most have high co-efficients of variability.
The annual average rainfall by district varies from 300 to 600 mm with low values in the south-western districts and higher values in the north, east and in the south-eastern region around Gaborone. Malaria incidence is higher in wetter regions except in the south-eastern region.
The annual maximum temperature by district varies between 28oC and 34oC with higher values to the north-west and lower values to the south-east. The annual minimum temperature by district varies between 12oC and 16oC with higher values to the north-west and lower values to the south-east.
“We focussed our analysis on the main transmission season between January and April and considered the relationship of meteorological variables in the same season and with a lag of one and two months by inspecting time series, scatter plots and using correlation analysis,” Radithupa says.
The study has also found that increases in rainfall increase breeding site availability and, therefore, increase malaria vector populations and that increases in rainfall are associated with increases in humidity, which result in higher adult vector survivorship ÔÇô and therefore a greater probability of transmission.
According to Radithupa, Botswana is far ahead of some countries in the region in terms of how it manages its malaria programme. Botswana’s preparedness plans include training plans for health workers, spraying exercise and awareness campaigns. The Malaria Epidemic Preparedness and Response Committee meets regularly to monitor the situation and is responsible for coordination and implementation of the contingency plan. Intensified surveillance of malaria cases and deaths are reported on a weekly basis to the ministry where they are monitored on a graph that depicts the disease trend and raises alarm when more than expected cases are recorded.
In the latest phase of the study, Radithupa studied data from 1996 to 2007.
What sets Botswana apart from other African countries is that here malaria is a notifiable disease; laboratory-confirmed cases are recorded; and, dates of changes in drug policies in Botswana are known. The Ministry of Health has compiled consistent statistics on malaria incidence since the early 1980s that include national and district data on cases of laboratory-confirmed malaria. The ministry has maintained a relatively good national case reporting system with weekly records available for all districts from 1982.
Radithupa says that the next step of the research would be to expand focus beyond malaria.
“We would look at other diseases like meningitis, dague and heat stress to determine whether their occurrence is weather-related,” he says.