Malaria in Nigeria is predominantly caused by Plasmodium falciparum and the country experiences varied endemicity due to the different ecological zones across different states, supporting uneven parasite transmission. Moreover, of the estimated 241 million cases and 627,000 deaths reported in 2021, sub-Saharan Africa (SSA) contributes 95%, while Nigeria is responsible for 24% of the global cases and mortality within the same period (1). Nigeria, a country that is 62 years post-independence on the 1st of October 2022, continues to be the most overburdened in terms of morbidity and mortality. Since the last decade, Nigeria and the Democratic Republic of Congo have topped the number of malaria cases and deaths. However, Nigeria has taken the lead in contributing approximately a quarter (25%) of the total cases and deaths, except in 2017 (2), 2018 (3), 2019 (4), and 2020 (5), where it contributed 24%, 19%, 24%, and 23% respectively.

The Federal Ministry of Health, Nigeria through the National Malaria Elimination Program has instituted various control measures (6) amidst this gloomy report. The different control strategies being implemented include indoor residual spraying of wall surfaces with dichlorodiphenyltrichloroethane (DDT) and pyrethroids, distribution of long-lasting insecticide-treated nets, and larviciding in different parts of the country at different rates (6, 7). On the other hand, seasonal malaria chemoprevention, intermittent preventive treatment (in pregnant women and infants) with sulphadoxine-pyrimethamine and the use of artemisinin-based combination therapy (ACT) is being used to treat, and prevent malaria infections in susceptible individuals (8). Despite these control initiatives, however, Nigeria is still the most burdened malaria country. Published reports have underlined possible reasons discussed below responsible for the sustenance of malaria transmission.

Vector control interventions are sparingly contextualized to the different ecological zones of the country. In Nigeria, there are six ecotypes: Sahel, Sudan, Guinea savannah, Rainforest, mangrove forest, and freshwater. Peripherally, these ecological zones fall on the northern (Sahel, Sudan, and Guinea Savannah), and southern belts (rainforest, mangrove forest, and freshwater (9). Precipitation, which is a major driver of vector breeding and abundance varies significantly across these zones. For example, the Sahelo-Sudan-Guinea savannah has low precipitation (<2000 mm) (9, 10), while precipitation in the rainforest, mangrove forest and freshwater can be as high as 4000 mm per annum. An in-depth and adequate understanding of vector dynamics across these various zones would positively impact malaria control efforts in Nigeria.

In addition, several anopheline vectors abound in Nigeria from An. gambiae s.l, An funestus, An. arabiensis (11). However, some of these vectors can sometimes be geographically localized: for instance, An. moucheti, and An. melas has been found to be present and transmit malaria in the rainforest and mangrove forest ecotypes predominantly covering southern Nigeria, but absent in the guinea savannah (northwestern Nigeria) zone (10, 12).

Most studies have principally focused on the composition of vectors, sporozoites rate, entomological inoculation rate, biting behaviors, or insecticide resistance genes (11, 13, 14). The differences in the ecotypes present an opportunity to design vector-tailored control initiative that is peculiar to each zone: for instance, in the rainforest, mangrove forest, and freshwater zones where precipitation can be up to 4000 mm per annum, vector control initiatives such as larviciding would have to be implemented just before the rainy season (January –March in rainforest and mangrove forest; December –May in freshwater ecological zones) and not during the period of heavy rains when larvicides can be easily washed off. In addition, the behavior of ecotype-specific vectors and how they manifest when there is a change of season will be impactful in implementation of control strategies. Though a long-term goal, a deep and focused study to understand how each vector species contributes to, or evaluation of vector microbiome that can be employed to inhibit malaria transmission will provide valuable insights into vector capacity.

Malaria transmission pattern in Nigeria is largely and remarkably heterogeneous, hence control measures must take this uniqueness into consideration while designing intervention strategies. Healthcare accessibility differs between rural and urban areas, where it has been reported that individuals are more likely to embrace control measures, especially the use of insecticide-treated nets in urban as opposed to rural areas (15). Moreover, it has been reported that there is high probability of indiscriminate use of proscribed antimalarials (16–18) that could potentially contribute to drug-resistant parasites in circulation (19, 20). In addition, living in housing patterns that are conducive to mosquito breeding would strongly ensure continuous malaria transmission. Adding to the litany of factors ensuring the high and continuous transmission of malaria is the obvious change in climatic conditions. Different epidemiological and modeling studies (9, 21–23) have attributed a correlation between increased precipitation and temperature with vector abundance and hence malaria transmission. Some of the states in Nigeria sit along coastal lines where the excessive flow of water from dams in neighboring countries leads to flood; a situation that is almost an annual occurrence.

What course of action must then be taken to alleviate Nigeria from this perpetual malaria burden, and achieve a pre-elimination status? First, an increased political commitment at all levels of government, within and between various parastatals, is urgent and imperative. This will ensure that Nigeria, a signatory to the United Nations’ sustainable development goal, which seeks to ensure healthy lives and promote well-being for all ages among other things, meets the World Health Organization 2030 Malaria Elimination Plan, or at least is on track to attaining a pre-elimination status. Therefore, adequate planning to prevent the frequent flooding that occurs in some states must be instituted. Drainages along those coastal areas should be dredged to ensure the free flow of water. Additionally, structured and strategic research plans need to be established. Such will include continuous monitoring of vectorial capacity, and strengthening of ongoing vector susceptibility tests to insecticides in use (13), identifying hotspots of malaria transmission, understanding the genetic structure and architecture of P. falciparum within and between Nigerian groups, and geographical regions, delineating the inter/intra-regional migration of parasite populations. Furthermore, it will also be geared towards identifying the extent, dynamics, and heterogeneous nature of non-falciparum malaria transmission within the country. It is equally crucial for national policymakers to quickly align and identify with recent policies evidenced to reduce malaria morbidity within the country. The post-discharge malaria chemoprevention (PDMC) initiative is recommended to reduce hospital readmission and death in children who have been treated for severe malarial anemia (SMA). Children admitted for SMA do not regain full hematological function until 2-3 months. Hence, treatment of these children with approved ACTs 3- 6 months post-discharge has been found to be very effective in Kenya, Uganda (24), and Malawi (25). Data from modeling studies have also shown that PDMC can reduce malaria readmission by 37,000 annually in Africa (26). If implemented in Nigeria, PDMC may provide considerable protection against malaria and anemia in young children. As immunization is one of the most effective disease control strategies, it is crucial that the government through the Ministry of Health make prudent plans for the acquisition and deployment of the newly approved RTS S/ASO1 vaccine (27) to the most vulnerable group - children. The provision of an added 30% protection against malaria episodes will undoubtedly reduce the number of country-wide cases and ultimately mortality. Moreover, the approval of the promising R21/Matrix M malaria vaccine will provide an additional tool for prophylaxis. Due to reports of P. falciparum histidine-rich protein II gene deletion in some parts of the country (28), we recommend that a non-hrp2 pan-specific malaria rapid diagnostic test (mRDT) be deployed. This will provide the added benefit of being able to detect non-falciparum species that may be present even though their contribution to malaria in Nigeria is insignificant.

As Nigeria remains the highest global contributor of malaria cases and mortality, attaining the global malaria elimination 2030 target will require, on the one hand, a combination of various effective control strategies that will target the different factors sustaining malaria transmission in the various ecological zones; and on the other hand, a focused, calculated, and conscious research efforts to gain a better understanding of the parasite and their behavior to different control measures.

The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.

MO conceptualized and wrote the first draft. KO, OA and BT provided critical review. All authors contributed to the article and approved the submitted version.

We acknowledge ongoing support and funding from the College of Health Sciences and Technology, Rochester Institute of Technology (BNT). MAO is supported through the American Association of Immunologists Intersect Fellowship Program for Computational Scientists and Immunologists.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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