Dengue – An underestimated risk in rural Africa

A pril 2019: a sudden outbreak of dengue fever tears through Tanzania. More than 1200 people in Dar es Salaam, Tanga and the Singida region seek medical care. It was the worst dengue outbreak in five years. The disease affected 2000 people at that time. The Ifakara Health Institute (IHI), based in rural Ifakara, is at the front line of efforts to research and combat the infectious disease, which is transmitted by the Aedes mosquito. The research facility

is one of the most cutting-edge in Africa and is worth a closer look.

Part of the Ifakara Health Institute in Ifakara, it is called Vectorspheres. The name says it all. Inside the building complex, scientists research a variety of vectors – organisms that transmit disease. State-of-the-art, Silicon Valleytype technology reigns supreme here. Mosquitoes at different life stages can be seen being reared under hot lamps in breeding rooms. A peculiar apparatus tests whether human sweat secretions attract the Anopheles mosquito, the carrier of malaria. New mosquito traps and mosquito nets impregnated with insecticide are tested for their effectiveness against the mosquitoes.

A picture on the wall shows two confident Tanzanian women. The slogan beneath says: “We are not women in science. We are scientists.” One of these scientists is Najat Kahamba. She is working on a research project about the Aedes mosquito (Aedes aegypti), which transmits the dengue virus in rural Tanzania. “Many people still think that the dengue virus only occurs in large towns, but that is a fallacy”, says Najat Kahamba.

Every morning, she and her team drive to the nearby villages. Using a ladle, she takes water samples from the mosquitoes’ potential breeding grounds. Unlike Anopheles, which transmits the deadly disease malaria, the Aedes mosquito only requires a very small and shallow body of water to lay its eggs. A knothole filled with water, an empty can, or half a coconut shell are all this humble insect needs. “Out here in the country, the Aedes mosquito has a much wider variety of breeding places than it has in Dar es Salaam”, says Kahamba. In the city, the mosquito only has rain gutters or old car tires. In addition, President John Magufuli encourages the city’s inhabitants to tidy up their surroundings every Saturday. “This is a practice that is less frequently observed in rural areas.”

Kahamba counts the larvae and meticulously describes the location where they were found. Her investigations are frequently guided by the village council. Close cooperation with local people is key for this kind of study. Most people do not realise they have contracted dengue fever when they fall ill. To this day, any kind of fever will be interpreted as malaria, and the illness is treated accordingly. It is unclear how many people around Ifakara actually contract dengue. Thus far, the district’s hospitals and health centres are unable to provide a diagnostic confirmation of the virus. Furthermore, there is no specific treatment for dengue.

Treatment options are limited to alleviating the symptoms with medicines to reduce fever and pain. If patients contract a severe form of the illness, they have to be hospitalised and

rehydrated. The available vaccine (Dengvaxia), which was approved in 2016, is not without its problems. In people who never have come into contact with the virus, the vaccine acts like a first infection. If they then are reinfected naturally, the body reacts to this as to a secondary illness and with much more pronounced symptoms. “The best way to prevent the illness is to protect against the mosquito bites”, says Kahamba. In order to achieve this, the public need to be educated about how to protect themselves against mosquitoes that bite during the day. This is particularly crucial in rural areas of the country because there, the mosquitoes have far more opportunities to breed than they have in Dar es Salaam.