1.1 Introduction
An invasive species is generally defined as an organism that is not native to a particular ecosystem and whose introduction is likely to cause harm to human health, the environment, or the economy (Simberloff et al., 2013). in the context of vector-borne diseases, invasive mosquito species are of particular concern because they have the potential to alter patterns of transmission, complicate control efforts, and intensify disease burden in affected regions. Nigeria, which already carries one of the heaviest malaria burdens globally, is increasingly confronted with the threat posed by invasive mosquito species such as Anopheles stephensi (Sinka et al., 2020). Malaria remains a major public health issue in Nigeria, accounting for nearly 27% of global malaria cases and 32% of malaria-related deaths worldwide, according to the World Health Organization (WHO, 2023).
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitation of the study and Definition of terms.
1.2 Background of Study
Historically, invasive mosquito species and their role in malaria transmission is closely tied to the global spread of mosquitoes beyond their native habitats through trade, travel, and ecological changes. According to Tatem et al. (2006), the globalization of commerce and human mobility has facilitated the introduction of mosquito species into new regions, where they establish and adapt to local environments. Historically, malaria transmission in Nigeria has been primarily associated with indigenous species such as Anopheles gambiae and Anopheles funestus, which have long been recognized as the dominant vectors of the disease in sub-Saharan Africa.
Mosquitoes are among the most important vectors of human diseases globally, responsible for the transmission of malaria, dengue, yellow fever, Zika virus, and other vector-borne infections. According to the World Health Organization (2023), malaria remains a major public health burden in sub-Saharan Africa, with Nigeria accounting for nearly 27% of global malaria cases and over 30% of malaria-related deaths. Traditionally, malaria transmission in Nigeria has been dominated by native vectors such as Anopheles gambiae and Anopheles funestus. However, the emergence of invasive mosquito species is reshaping the epidemiological landscape and raising new concerns about malaria control and elimination.
Sinka et al. (2020) reported that Anopheles stephensi, an invasive mosquito species originally restricted to South Asia and the Middle East, has now been detected in several African countries including Ethiopia, Djibouti, and Sudan. The authors further asserted that this species is particularly dangerous because of its ability to adapt to urban environments and thrive in man-made water containers, which significantly increases the risk of urban malaria outbreaks. Moyes et al. (2016) stated that invasive species not only overlap with local vectors but also alter existing transmission dynamics, thereby complicating control strategies that were previously effective against indigenous mosquito populations.
Takken and Lindsay (2019) affirmed that invasive mosquito species possess biological and ecological advantages that enable them to spread rapidly across regions with limited resistance from local ecosystems. These advantages include insecticide resistance, a high reproductive rate, and the ability to exploit diverse breeding sites. Nigerian Institute of Medical Research (2022) contends that the presence of invasive mosquito species in Nigeria is not just a theoretical possibility but a practical reality, as early entomological surveys have suggested traces of new vector populations in certain urban centers. This development is troubling because Nigeria’s malaria control strategies have historically been designed to target native Anopheles species, leaving a gap in preparedness for invasive vectors.
On the other hand, researchers have observed that inadequate urban planning, poor waste management, and rapid population growth create favorable conditions for invasive mosquitoes to thrive in Nigeria. Githeko et al. (2012) reported that the rise of invasive species in Africa has coincided with environmental and climatic changes, which facilitate their survival and expansion. This trend implies that the threat posed by invasive mosquitoes is not isolated but interconnected with broader socio-environmental factors. This study is set against the backdrop of understanding these emerging threats, evaluating their potential impact on malaria transmission, and identifying effective strategies for mitigation through the Nigerian Institute of Medical Research.
1.3 Statement of Problems
Investigation revealed that invasive mosquito species is reshaping the dynamics of malaria transmission in Nigeria. These species is not only spreading to areas where malaria was previously less endemic but is also overlapping with existing local mosquito populations, creating a more complex transmission cycle. On the other hand, the invasive mosquitoes is exhibiting behavioral patterns such as biting during unusual hours and breeding in unconventional sites, which reduces the effectiveness of current control measures that were designed primarily for local vectors. This situation raises serious concerns for public health researchers, policymakers, and communities.
Furthermore, laboratory and field-based studies within the Nigerian Institute of Medical Research have shown the need for continuous surveillance to track not just the spread of these species but also their role in sustaining malaria transmission despite existing control interventions. If this issue is not adequately addressed, invasive mosquito species is likely to exacerbate the malaria burden, undermine years of investment in malaria control programs, and complicate the achievement of global health targets, including the Sustainable Development Goals (SDGs). The potential for increased urban malaria outbreaks, drug-resistant parasite spread, and resistance to insecticides further compounds the challenge. It is against this backdrop that this study seeks to investigate the invasive mosquito species in Nigeria and their potential impact on malaria transmission, using the Nigerian Institute of Medical Research as a case study.
1.4 Aim and Objectives of Study
The aim of this study is to assess the invasive mosquito species in Nigeria and their potential impact on malaria transmission using the Nigerian Institute of Medical Research as a case study. In achieving this aim, the following specific objectives were laid out as follows:
- To examine the ecological and behavioral characteristics of invasive mosquito species that influence malaria transmission.
- To evaluate the potential contribution of invasive mosquito species to malaria prevalence in urban and peri-urban areas.
- To identify the presence of invasive mosquito species within Nigeria.
- To assess the effectiveness of existing malaria control strategies in addressing invasive species.
- To provide recommendations for improving surveillance and control measures targeting invasive mosquito populations.
1.5 Research Questions
The study came up with research questions so as to be able to ascertain the above stated objectives. The specific research questions for the study are stated below as follows:
- What ecological and behavioral characteristics of invasive mosquito species influence malaria transmission?
- How do invasive mosquito species contribute to malaria prevalence in urban and peri-urban areas?
- What invasive mosquito species are present in Nigeria?
- How effective are existing malaria control strategies in addressing invasive mosquito species?
- What measures can be recommended to improve surveillance and control of invasive mosquito populations?
1.6 Significance of Study
The outcome from the findings of this research will hold significant relevance in the following ways.
- The study will benefit the government by providing evidence to strengthen national malaria control policies.
- It will help researchers by expanding the body of knowledge on invasive mosquito species and their epidemiological significance.
- It will assist public health institutions like the Nigerian Institute of Medical Research by guiding surveillance and intervention strategies.
- It will support communities by increasing awareness of the risks posed by invasive mosquitoes and the importance of environmental management.
- It will benefit international health organizations by contributing data that will aid in regional and global efforts toward malaria elimination.
1.7 Scope of Study
The scope of this study is limited to Lagos State, with particular focus on the Nigerian Institute of Medical Research (NIMR). The study will concentrate on assessing the presence of invasive mosquito species in urban environments and examining their potential role in malaria transmission dynamics.
1.8 Limitations of the Study
A study of this nature is bound to experience certain problems as such the constraints imposed on the research include:
- Time Constraints: A study of this nature needs relatively long time during which information for accurate or at least near accurate inference could be drawn. The period of the study was short, time posed as constraints to the research.
- Financial Constraints: The research would have extended the survey to other area at the empirical level, but limitation as included cost of transportation to the source of material and the cost of time setting of the already completed work.
1.9 Definition of Terms
Invasive Species:
According to Simberloff et al. (2013), invasive species refers to non-native organisms that spread into new areas and cause harm to human health, the environment, or the economy. In this study, it specifically refers to mosquito species like Anopheles stephensi that have spread into Nigeria.
Malaria Transmission:
World Health Organization (2023) defined malaria transmission as the spread of malaria parasites to humans through the bite of infected female Anopheles mosquitoes. In this context, it relates to how invasive mosquito species influence the prevalence of malaria in Nigeria.
Vector:
Takken and Lindsay (2019) described a vector as an organism that transmits pathogens from one host to another. In this study, mosquitoes are vectors responsible for transmitting malaria parasites.
Surveillance:
Githeko et al. (2012) stated that surveillance involves the continuous monitoring of vector species to understand their distribution, population dynamics, and role in disease transmission. It is crucial in detecting invasive species.
…
