The Zanzibar archipelago, a popular destination off the coast of East Africa, has achieved global recognition for its success in reducing malaria transmission. The islands moved from high endemicity to near-elimination status through sustained public health campaigns. This achievement stands as a significant case study in disease control for regions pursuing malaria elimination. Focused governmental effort, supported by international partners, fundamentally altered the epidemiological landscape of this mosquito-borne illness.
The Current State of Malaria in Zanzibar
The islands of Zanzibar have successfully pushed the overall prevalence of malaria to below one percent, a figure substantially lower than on the Tanzanian mainland. This low prevalence means that local transmission is significantly controlled, though the risk has not been eliminated entirely. Transmission risk peaks during the two main rainy seasons, which typically occur from March to May and again from October to December.
A major challenge to achieving full elimination is the continuous influx of imported malaria cases, primarily from mainland Tanzania. These cases account for a large proportion of the malaria burden, serving as a persistent reservoir for the parasite. The primary mosquito vector is Anopheles arabiensis, which has shifted its behavior toward biting outdoors, especially during the early evening. Despite the overall success, the archipelago experienced a surge in cases in 2023, recording over 19,000 infections, which highlighted the fragility of the progress.
Key Strategies for Malaria Control
Zanzibar’s success is rooted in the multi-faceted approach implemented by the Zanzibar Malaria Elimination Program (ZAMEP), which systematically targeted both the parasite and the vector. The strategy included the mass distribution of Long-Lasting Insecticidal Nets (LLINs) to the population. The goal was to ensure that nearly every two people had access to one net, providing a constant chemical barrier against nighttime-biting mosquitoes.
ZAMEP also utilized targeted vector control through Indoor Residual Spraying (IRS). This method involves coating the internal walls of homes and structures with long-acting insecticide, killing mosquitoes that rest indoors. Analyses of the 2023 case surge suggested that temporary gaps in IRS and LLIN coverage contributed to the rebound in transmission, underscoring the need to maintain high coverage rates.
The program also emphasized “Test and Treat,” ensuring that malaria diagnosis and treatment are readily available and accurate. This involved equipping all public health facilities with Rapid Diagnostic Tests (RDTs) and microscopy capabilities to confirm infections. Confirmed cases are treated promptly with appropriate Artemisinin Combination Therapy (ACT), which is highly effective against the Plasmodium falciparum parasite.
The Intensive Surveillance and Response (ISR) system, also known as Reactive Case Detection (RACD), is a key strategy. When a malaria case is confirmed at a clinic, ZAMEP teams are dispatched to the patient’s home and surrounding houses within a defined radius. These teams actively test and treat individuals in the immediate vicinity, creating a containment ring to prevent further spread from the source. This targeted, rapid response approach has been effective in isolating and eliminating small pockets of local transmission.
Essential Prevention Measures for Travelers
Even with the low overall prevalence, travelers to Zanzibar should take comprehensive precautions against malaria. The risk is considered high enough that international health authorities recommend chemoprophylaxis for all travelers visiting areas below 1,800 meters, which includes the entire archipelago. Travelers should consult a physician or travel medicine specialist several weeks before the trip to discuss the most appropriate medication, such as atovaquone/proguanil (Malarone), doxycycline, or mefloquine.
Malarone is often the preferred choice for short trips because it requires starting the medication only a day or two before arrival and continuing for just seven days after departure. Beyond medication, personal bite prevention measures are important, especially considering the local vector’s tendency to bite outdoors in the early evening. Applying insect repellent containing an active ingredient like DEET to exposed skin provides an effective barrier.
Wearing long sleeves and trousers, particularly between dusk and dawn, reduces the surface area available for mosquito bites. Travelers should also ensure their accommodation is well-screened or that they sleep under an insecticide-treated bed net. If any symptoms develop, such as fever, chills, or severe headaches, the traveler must seek immediate medical attention, even up to a year after returning home, as prompt diagnosis is necessary for successful treatment.