In a recent study, researchers explore and discuss the development and implementation of a new insecticide resistance management plan in Zambia between 2009 and 2014.
In a recent article in Emerging Infectious Diseases, Emmanuel Chanda, PhD, Ministry of Health, Lusaka, Zambia, and colleagues discuss the development and implementation of a new insecticide resistance management plan in Zambia between 2009 and 2014.
Vector control plays a critical role in the continued fight against the transmission of mosquito-borne diseases in humans, including malaria. However, despite being a central component of vector-control programs, repeated insecticide use has led to the development of insecticide resistance among mosquitoes in many countries with ongoing malaria transmission.
As a consequence, in 2012, the World Health Organization (WHO) published the Global Plan for Insecticide Resistance Management (GPIRM) in malaria vectors. This document called for governments of malaria-endemic countries and other stakeholders to implement a strategy to combat the growing threat of insecticide resistance and to facilitate the development of innovative vector control tools and strategies.
However, “no country has documented how it formulated or executed these policies and addressed challenges,” the authors write. “To realize fully the vision of the GPIRM, national malaria control programs must share experiences regarding policy-making processes.”
Dr. Chanda and colleagues therefore reported on the formulation and implementation of a new insecticide resistance management plan (IRMP) in Zambia between 2009 and 2014.
According to the authors, Zambia’s National Malaria Control Centre (NMCC) formed the Insecticide Resistance Management Technical Working Group (IRMTWG) in 2010. This multisectoral group comprises members of government, nongovernment, and private organizations that have a vested interest in vector control.
In 2011, the IRMTWG outlined a set of step-wise policy objectives for their management plan:
Objective 1: Collect more insecticide resistance data
Through efficient collaboration of various stakeholder sectors, the IRMTWG was able to acquire more data about insecticide resistance throughout the country. Each year, the IRMTWG interprets all available resistance data and provides guidance about which regions require focused monitoring efforts during the following year. “This work has resulted in a better understanding of the resistance profiles of the major malaria vectors throughout the country,” the authors note. However, they acknowledge that monitoring is a large task that is challenged by the limited financial and human resources that are available to any single organization.
Objective 2: Determine the mechanisms involved in insecticide resistance
Data from rapid molecular assessment of local vectors was used to guide decision making in the management plan. In Anopheles gambiae mosquitoes, resistance was shown to be associated with mutations in the DDT/pyrethroid target site—known as knockdown resistance (kdr) alleles—as well as with elevated levels of activity of P450 and glutathione S-transferase detoxification enzymes. In Anopheles funestus mosquitoes, resistance to carbamates and pyrethroids was shown to be associated with elevated levels of activity of P450. These findings confirmed that pyrethroids should no longer be used in insecticide rotations because of the metabolic mechanism of resistance.
Objective 3: Establish a database for insecticide resistance data
According to the authors, “[r]eliable and available resistance-monitoring data are essential for evidence-based decision making.” The Disease Data Management System (DDMS) entomology module was the tool used to meet the data management needs of the program in Zambia. However, the authors highlighted that it was challenging to adopt this system because of the lack of data management capacity—in the form of financial and human resources—within the NMCC. Nevertheless, the NMCC sought technical training for users, to ensure that they were competent using the system.
Objective 4: Develop an IRMP
The IRMTWG holds annual meetings, the main goal of which is to evaluate resistance data to guide decisions about which insecticides to use for indoor residual spraying (IRS) during the next spray season. By 2014, the resistance profile in all areas of the country was known, the resistance database was in use, and regular IRMTWG and Technical Advisory Committee (TAC) meetings were being held. Thus, the first IRMP was released, and was subsequently revised and modified. In addition to emphasizing the need to avoid pyrethroids for IRS because of widespread resistance, it recommends the use of organophosphates in rotation with DDT (where Anopheles funestus or Anopheles arabiensis mosquitoes are the main vectors) to control vector populations and reduce selection pressure of any particular active ingredient.
However, according to the authors, the lack of options for insecticide rotation has been the biggest challenge in developing the plan—only 4 classes of insecticides with 2 modes of action are currently recommended for IRS. They emphasized the need for industry to develop new classes of insecticides that are suitable for public health purposes.
“Resistance monitoring and management must be integrated into all vector-borne disease control programs so that available insecticides can be used judiciously and the efficacy of chemical-based control can be sustained for the long term,” the authors conclude.
Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.