Distribution and evolution of plasmodial infection in Madagascar according to incidence per 100,000 inhabitants

doi:10.21203/rs.3.rs-3237264/v1

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Distribution and evolution of plasmodial infection in Madagascar according to incidence per 100,000 inhabitants

https://doi.org/10.21203/rs.3.rs-3237264/v1

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Background

Malaria is still a public health problem in Madagascar. The infection remains difficult to eliminate. The objective of this study is to establish the spatio-temporal distribution of malaria in Madagascar by considering the incidence profile.

Methods

This is a cross-sectional study that identifies the temporal-spatial evolution of malaria. The study period extends from 2019 to 2021. The analysis of the trend of malaria is analyzed through the evolution of the incidence and the spatial distribution using a thematic cartography.

Results

The present study revealed that the trend of malaria infection increased from 2019 to 2021. Spatially, malaria infection still experiences a heterogeneous distribution according to the epidemiological facies. The study was also able to highlight the importance of reliable data for disease surveillance. Control strategies must prioritize the entire pediatric age group for prevention and treatment but not only those under 5 years of age.

Conclusion

the fight against malaria must take into account the seasonality of the infection and the distribution of resource necessary for the fight against malaria must consider the heterogeneity of the spatial distribution of the infection.

Incidence

Madagascar

Malaria

Spatio-temporal analysis

Malaria is an infection caused by the Plasmodium falciparum species and not falciparic. The infection is transmitted by Anopheles mosquitoes, with Anopheles gambiae sensu stricto, Anopheles funestus and Anopheles arabiensis being the most common in Africa [1]. In 2020, almost half of the world's population is exposed to the risk of malaria with 87 endemic countries. There are an estimated 241 million cases and 627,000 deaths from malaria. Estimates point to 14 million more cases of malaria in 2020 than in 2019 and 69,000 more people died from malaria in 2020 than in 2019. Children under 5 are the most vulnerable group accounting for 77% of death cases. For Madagascar, the 90% of malaria cases are caused by the species P. falciparum, it is a deadliest species requiring correct and early management. Nearly two-thirds (2/3) (47,000) of additional malaria deaths resulted from disruptions in malaria prevention, diagnosis and treatment services during the COVID-19 pandemic [1–5].

Despite efforts to increase resources allocated to the fight against malaria at the international level for both low- and middle-income countries from the year 2000 to 2020, malaria infection remains difficult to eliminate [2]. African modeling studies predict that the burden of malaria cases will shift to older children as transmission declines, despite this the most severe consequences of the disease will continue to affect mainly the youngest children under 5 years of age [6–7]. According to studies in Africa, children aged 5 years through adolescence are highlighted as having a high level of risk for uncomplicated malaria. They have more episodes with progressively decreasing transmission [8–9], more than their younger counterparts under 5 years of age [10–11].

According to other literature, adults are also subjects exposed to an increased risk of clinical episodes of malaria, probably due to the decrease in antimalarial immunity that follows a reduced exposure to parasites [11]. Additionally, adults can put those around them at risk by continuing to harbor chronic low-density infections even as transmission declines [8, 12]. In Africa, reductions in malaria disease burden are attributed mainly to an intensification of combinations of control strategies: insecticide-treated bed nets, indoor residual spraying and intermittent preventive treatment for pregnant women for prevention, better diagnostics for case ascertainment and effective treatments using artemisinin-based combination therapy (ACT) [4].

Despite malaria elimination efforts, latent reservoirs of infection may persist such as chronic infections and low parasite density infections [13] and may serve as a neglected reservoir for continued transmission making malaria elimination difficult. Madagascar is a malaria endemic country. In Madagascar, malaria is a major public health problem with an incidence of 81.72% and hospital lethality of 0.3% in 2021 according to the Directorate of Planning and Information System Studies in Madagascar. In 2020, malaria was the most common cause of hospital mortality and the leading cause of morbidity. In 2021, malaria represents the 8th most frequent cause of hospital mortality and the 5th cause of morbidity. Despite progress in eliminating malaria, seasonal upsurges have occurred in various parts of the island.

Faced with the low availability of resources in Madagascar for the diagnosis and the persistence of the infection, the present study aims firstly to assess the incidence of malaria according to the characteristic of the population, secondly identify the spatial location and the temporal evolution of the infection and to identify priority areas for intervention, then to propose recommendations to the competent authorities based on the results of the study.

Madagascar is an island located in the southern part of the African continent, in the southwest of the Indian Ocean. With an area of 587,401 km2, Madagascar is a large island that extends over 1,600 km long and 570 km wide. The country has 23 regions subdivided into 119 administrative districts which are divided into 1,693 communes and 18,251 Fokontany.

Due to regional variations in rainfall, temperature and altitude, malaria transmission is heterogeneous in Madagascar. Two main profiles are thus identified, firstly a stable and perennial malaria along the coasts, where nearly half of the Malagasy population lives and secondly an unstable malaria in the Central Highlands and the sub-desert South.

The Malagasy population is estimated at 26,251,309 inhabitants in 2020 according to the National Institute of statistic in Madagascar. It is mainly characterized by a young population with 42% of people aged under 15. Children under 5 represent 18% of the population. The average density is 43.7 inhabitants/km2, but the population is mainly concentrated in the central highlands which contain nearly 62% of the total population. This is a cross-sectional and descriptive study and the study period extends from 2019 to 2021.

The data was collected from the District Health Information Software-RMA (DHIS2-RMA). The data first undergoes a quality control by purification: of input error, aberration, inconsistency. It is only after the checks that the analysis is carried out. The first quality control of the data is carried out with the tools at the DHIS2 level (monthly). The second data quality control: Excel tools available at the level of the National Program fighting against Malaria. For data analysis, it is a retrospective analysis from the national information system. For this analysis, the data from the health center are aggregated by district on the number of malaria cases. The malaria incidence is obtained by taking into account the number of the population taken from the general census of the population in 2020 from the National Institut of Statistic of Madagascar. The malaria incidence per hundred thousand inhabitants is calculated. Analysis of the distribution of the infection according to the characteristics of the population, the diagnostic by Rapid Diagnostic Test, the temporal and spatial evolution.

Microsoft Excel software, R software are used for data management and statistical analysis of data and QGIS 3.14.16 software is used for mapping. The data used for this study is anonymous data. No information allowing the recognition of individual persons is possible. This study is exempt from authorization by the ethics committee. The study will be conducted with the authorization of the Secretary General of the Ministry, Director of Communicable Disease Control and the Director of Studies, Planning and Information System to access data in the DHIS2 system. Researchers are required to respect professional secrecy, to respect the confidentiality of the data used. For data security, computers and files relating to the study will be locked with a password that only researchers can possess.

This is a spatial and temporal analysis of malaria cases. The analysis of malaria cases is thus carried out according to the overall incidence during the period studied, the incidence according to the age category, the incidence according to the geographical distribution, the temporal evolution incidence, hospital morbidity and positivity rate.

The results of the analysis (Fig. 1) carried out on malaria morbidity demonstrated an increase in the epidemiological trend of malaria taking into account the incidence per 100.000 inhabitants for malaria from 2019 to 2021.

The figure (Fig. 2) below shows several districts whose incidence per 100,000 inhabitants remains very high. The Highland part of Madagascar shows its low incidence status.

The figure (Fig. 3) below shows that the positivity by district.

The figure below shows that malaria rapid diagnostic test positivity is highest in 6 to 13 ages with peak positivity in April 2020 and April 2021.

This study was able to highlight the importance of having a reliable information system in order to make decisions for a better policy towards the elimination of malaria. The availability of routine and epidemiological surveillance data is necessary in order to carry out timely and effective responses in order to limit the burden of disease caused by malaria. The analysis of the distribution of malaria infection is also more precise with a stratification of administrative units according to the health district level.

Spatial and temporal malaria incidence

The results of the analysis carried out on malaria morbidity demonstrated an increase in the epidemiological trend of malaria taking into account the data on the positivity of rapid diagnostic tests for malaria from 2019 to 2021. The results could be explained by the appearance of Covid19 cases in Madagascar which could have increased the investigation of fever cases at the health facility level. This study has shown several districts whose incidence per 100,000 inhabitants remains very high. The Highland part retains its low incidence status. The profile of malaria in Madagascar from 2020 to 2021 does not change significantly.

A study conducted in Burkina Faso has shown the importance of spatial analysis and the consideration of several variables in order to detect the source that perpetuates the infection and to predict the appearance of new cases. More elaborate studies are needed to refine the strategy to fight against malaria in Madagascar [14]. Another study conducted in Zimbabwe demonstrated a result similar to the present study concerning the spatial distribution of malaria with spatial heterogeneity in the distribution of infection by the existence of spatial groups with an evolution according to a temporal pattern that reflects seasonality of the infection [15].

Conventional control measures must be intensified considering the distribution of the infection at the district level, taking into account the use of mosquito nets impregnated with long-lasting insecticide, the provision of rapid diagnostic tests and artemisinin-based treatment for cases diagnosed by the care unit and vector control within the malaria program in Madagascar.

The results suggest carrying out more elaborate spatial analyzes by considering several variables such as meteorological parameters, seasonal variations in malaria by program managers within the malaria program in Madagascar in order to prioritize areas where malaria infection persists with high incidences and in order to anticipate the identification of areas where epidemic peaks will appear.

Epidemiological distribution according to age group and according to time

The distribution of malaria infection according to epidemiological stratification showed that a large number of districts are classified in the control zone status. Only the Central Highland part of Madagascar is located in the status of zone towards elimination. Positivity by district is quite similar for 2021 and 2022 but with slight variations for areas where there is high positivity (54–67%). The heterogeneous distribution of malaria infection can be explained by several parameters, a study conducted in Nigeria concerning between an associative model between malaria incidence and several geographical, climatic and meteorological parameters demonstrated an increase in incidence in correlation with the increase in temperature, aridity and proximity to water sources [16].

The results suggest considering the environmental profile of each district in the development of a local strategy for the fight against malaria. Spatio-temporal analysis is an essential way of discerning priority districts in the allocation of resources for diagnosis, management and vector control by those responsible for the malaria program. Integrating multivariate analysis into routine malaria control activities is important to address the determinants of infection persistence.

The present study shows that malaria rapid diagnostic test positivity is seen highest in 6 to 13 year olds with peaks of positivity in April 2020 and April 2021. Malaria infection in Madagascar is known to have a seasonal pattern. A study in East Africa found a predominance of malaria infection in children aged 3 to 59 months [17]. Another study conducted in Niger found a greater burden of malaria disease among 5 to 9 year olds [18]. Knowledge of the distribution of malaria infection according to age group is necessary in order to determine the presentations and forms of drugs most used and to target the age group that requires the most intervention in terms of chemotherapy. Vector prevention and protection.

In the literature, it has also been noted in Madagascar that the introduction of the rapid diagnostic test for malaria can lead to an increase in notified cases because since the introduction of the RDT in the national malaria control program in Madagascar, it has been found an increase in malaria incidence from 2007 to 2015 [19]. In the case of the present study, the results suggest prioritizing the age group of 6 to 13 and 1 to 5 years instead of the classic target of children under 5 years of age in the fight against malaria in terms of prevention and vector control for the case of malaria for malaria program managers at district level and within the Ministry of Health.

The present study was able to highlight the persistence of the plasmodial infection in Madagascar with a heterogeneous distribution of the infection by the existence of spatial and temporal group. The analysis of the distribution of the plasmodial infection by considering the district level made it possible to precisely target the priority intervention zones. The areas where the elimination of malaria is close, like the Highland part of Madagascar, should be given less priority in terms of resource distribution for the fight against malaria. The results of this study underline the importance of knowledge of the spatio-temporal character of malaria in Madagascar. A more in-depth analysis considering the meteorological, climatic, geographical characteristics, hydrographic characteristics is necessary in order to find determinants that could facilitate the path towards the elimination of malaria in Madagascar.

Acknowledgements

I aknowledge the Ministry of Public Health, the Faculty of Medicine and Persuade Project for the contribution on the conception, redaction and validation of this manuscript

Authors contributions

The authors wrote read and approved the final manuscript.

Funding

No specific funding

Availability of data and materials

Data available on the District health Information Software 2 of the Ministry of Public of Madagascar

Ethics approval and consent to participate

Not relevant.

Consent for publication

Authors declare their consent for publication

Competing interests

The author declares no competing interests.

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No competing interests reported.

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Distribution and evolution of plasmodial infection in Madagascar according to incidence per 100,000 inhabitants

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Abstract

Background

Methods

Results

Conclusion

Figures

Introduction

Methods

Results

Discussion

Spatial and temporal malaria incidence

Epidemiological distribution according to age group and according to time

Conclusion

Declarations

References

Additional Declarations

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