4/12/2013 10:30:00 AM

Challenges for malaria elimination in Zanzibar

A recently published paper in the scientific journal Parasites and Vectors highlights some of the challenges to achieving elimination of malaria on the island of Zanzibar.
The combination of indoor spraying with residual insecticides (IRS), high coverage with long-lasting insecticide treated nets (LLINs), case management and surveillance and monitoring has resulted in a reduction in malaria prevalence in Zanzibar from 40% in 2005 to between 0.2 to 0.5% in 2011 to 2012; according to an unpublished report from the Tanzanian Health Ministry Information System.

However, the complete elimination of malaria from the island, or even the maintenance of the 2011 to 2012 malaria prevalence levels is threatened by the increasing levels of resistance to the pyrethroid insecticide group used in LLINs (and within the historical IRS program) and the short lived efficacy of the LLINs. Physical examination of 150 permethrin-treated LLINs showed that two thirds were damaged after only three years of use and tests showed significant insecticide loss after washing. The study also highlights a concerning aspect that, regardless of the number of washes, the LLINs used in the program failed every criteria for efficacy within three years of use.

The malaria control program in Zanzibar is regarded as a well-resourced and well-managed program; this paper highlights key challenges to achieving elimination goals with these current intervention tools. The challenges observed from this island are equally applicable elsewhere.

It was not discussed within this paper but rotation of insecticide types used in IRS programs is an important step which can help in the management of insecticide resistance in malaria control programs. There are also LLIN options available which have been recently developed to help address the problem of insecticide loss from washing and fabric strength and lifespan. There are even some combination LLIN products which may play a role in slowing down the development of resistance. However all these new product technologies cost more than traditional LLINs and there is not yet a system in place which allows LLIN procurement programs to recognise the added benefit of these products within tenders.