For Mwashamba Idi and Juma Ali Juma, both residents of Zanzibar Island, malaria, is not a common part of their disease vocabulary.

As a matter of fact, malaria, a disease that kills a child every two minutes in Africa, is unheard of among many residents of the Unguja (Zanzibar Island). Many haven’t been infected for a long time, others have never had an infection.

This is because the island has managed to reduce its prevalence of malaria to below one per cent, meaning that extremely few people, mostly travellers and migrant workers, test positive for the mosquito-borne disease.

Zanzibar is made up of a series of islands in the Indian Ocean off the coast of Tanzania. Until 2003, the transmission of malaria here was more common. Over the last two decades, however, the island has maintained malaria prevalence below one per cent.

In 2020, an estimated 627,000 people died of malaria—most were young children in sub-Saharan Africa. According to the latest WHO World malaria report, there were an estimated 241 million malaria cases worldwide in 2020.

According to the Zanzibar Malaria Elimination Programme (Zamep), the island aims to eliminate malaria by 2023.

In this island, science has worked well to deliver the miracle of low malaria transmission.  Indoor spraying, provision of insecticide-treated mosquito nets and community sensitisation have all been efficient in the fight against the disease. There have also been coordinated international effort and investment, including early detection and treatment interventions, all that have quelled the spread of Plasmodium falciparum, the deadliest malaria parasite globally and the most prevalent in Africa.

These interventions, with sustained high-community uptake, have been temporally associated with a major malaria decline, most pronounced between 2004 and 2007 and followed by a sustained state of low transmission.

“Initially, the methods for diagnosing malaria were less accurate and not always available back then. So children with fever were commonly treated as if they had malaria,” recounts Mohamed Ali, the programme manager at Zamep.

The most crucial lesson the team at Zamep has learned is that targeting malaria interventions effectively is critical and should be informed by consistency. Between 2005 and 2012, Zamep’s deputy programme manager Faiza Bwanakheri Abbas, explains, Zanzibar began a mass combination of interventions including the use of artemisinin-based combination therapy (ACT) for malaria treatment and indoor/outdoor residual spraying to reduce mosquito-breeding areas.

These and insecticide-treated mosquito nets for malaria prevention, combined with community education, have made a significant impact.

“In 2006, we introduced blanket indoor spraying followed by mass campaigns for use of bed nets. Again, in 2008 we introduced a weekly surveillance system to detect malaria transmission patterns. This has allowed us to maintain the numbers low,’’ Abbas explains.

Additionally, a malaria case notification system introduced in 2012 has made it possible to track cases from the point of detection and to figure out the source of transmission. Consequently, it’s become easier to map all infected people, says Abbas.

By 2013, any resident of Zanzibar suspected to be infected with malaria was followed up, tested, and put on treatment early enough.

Meanwhile, the use of rapid diagnostic tests (RDTs) allow trained community members to perform malaria diagnosis accurately and to prescribe appropriate treatment. This substantially reduces delays between the onset of fever and treatment, according to Fredros Okumu, director of science at the Ifakara Health Institute (IHI) in Tanzania.

The island’s roll-out of community-based interventions free of charge helped to cut new cases of malaria recorded in the island’s health facilities by 94 per cent between 2003 and 2015. Today, Zanzibar provides a basic public health service package for its residents free of charge. Ms Mwashamba and Mr Juma are some of the beneficiaries of this provision.

As part of this package, all people on the island have access to affordable services for the diagnosis and treatment of malaria, regardless of their status.

Adds Ms Abbas: “We’ve ensured that we have universal, standardised and high quality coverage of testing and treatment services in both public and private health facilities.’’

According to her, vector control strategies on the island are not only dynamic but informed by the mosquito behaviour, trends, and response to the repellents used as well. Vector control is any method used to limit or eradicate the insects which transmit disease pathogens. The most frequent type of vector control is mosquito control. Finally, Ms Abbas adds, tracking insecticide and drug resistance is key and for that reason, the Zanzibar malaria elimination programme also hosts an insectary for the rearing of living mosquitoes to track resistance before it occurs.

Globally, malaria treatment efforts are hindered by rapid emergence and spread of drug-resistant parasites. In recent years, reports of sporadic resistance to modern anti-malarial drugs began appearing, and are now confirmed in Rwanda and Uganda.

“Just like human beings, mosquitoes have a behavioural pattern which we monitor to determine the type of intervention strategy we need to deploy at any particular time,” Ms Abbas notes.

A 2019 study published in BMC Medicine indicates that Zanzibar represents a unique case study of such an attempt, where modern tools and strategies for malaria treatment and vector control, have been deployed since 2003.

“Zanzibar’s case is unique because they have been able to achieve consistent commitment by the national malaria elimination programme and participation by community residents,” says Dr Okumu.

Whereas Zanzibar provides evidence of the feasibility of reaching significant and sustainable malaria reduction (pre-elimination) in a previously high endemic region, scientists say that new challenges call for novel tools and reoriented strategies to prevent a rebound effect and achieve elimination.

But replicating what the island has achieved may not be as easy elsewhere in the region, especially in countries with large populations such as Tanzania, Uganda and Rwanda and western parts of Kenya and other sub-Saharan African countries.

To eliminate Malaria by 2023, Zanzibar must tackle a new set of challenges, including outdoor transmission, a large asymptomatic parasite reservoir and imported infections.

In 2019, researchers found that although more people used insecticide-treated bed nets, there were gaps in protection, particularly while outdoors or away from home. According to the study published July in BMC Malaria journal, people had difficulty preventing mosquito bites while outdoors, travelling, or away from home, and perceived a higher risk of malaria infection during these times.

Travel and migration also emerged as crucial factors. Participants in the survey viewed seasonal workers coming from mainland Tanzania as more likely to have a malaria infection and less likely to be connected to prevention and treatment services in Zanzibar.

“For Zanzibar, focus is on preventing transmission while outdoors, travellers and migrant workers, which happen to be real problems in their pre-elimination phase where they angling to control residual transmission,” notes Dr Okumu.