The Pattern of Severe Malaria in Plateau State of Nigeria: A Five-Year Review of Severe Malaria Case-Based Surveillance Data from 2013 to 2017

There is a decline in the global incidence, morbidity, and mortality of malaria. However, approximately 20% of hospital admissions and 10% of hospital deaths in Nigeria have been attributed to malaria. This secondary data analysis was conducted to examine the pattern severe malaria in Plateau State in the face of declining global malaria infection. Severe malaria-specific Integrated Disease Surveillance and Response (IDRS) records of Plateau State of Nigeria over a five-year period were reviewed. A total of 38,467 cases of severe malaria were reported between January 2013 and December 2017. The highest number of cases 14098 (36.65%) was reported in 2016 and the least number of cases 950 (2.47%) were reported in 2014. A total of 362 severe malaria deaths was reported within the same period with a case fatality rate (CFR) of 0.94%. The highest CFR 1.43% was recorded in 2015 while the least CFR 0.00% was recorded in 2014. The 0-28 days age group had the highest CFR (3.13%). The comparative monthly trend of severe malaria cases did not follow any consistent pattern during the 5 years under review. However, as of 2017, the trends of total cases per year and CFRs were on the decline. In conclusion, the overall number of cases and deaths of severe malaria is declining in Plateau State but the CFR among neonates remains high. Therefore, prevention and control efforts should be intensified in Plateau State, in order to achieve malaria elimination in the State.


Introduction
Malaria is a protozoan infection of the red blood cells transmitted by the bite of a blood-feeding female anopheline mosquito [1]. Five species of Plasmodium have been known to infect humans: Plasmodium malariae, Plasmodium vivax, Plasmodium ovale and Plasmodium falciparum and Plasmodium knowlesi. Ninety-five percent of malaria infections in Nigeria are caused by Plasmodium falciparum and five percent by Plasmodium malariae [2]. P. falciparum is responsible for the highest morbidity and mortality attributed to malaria infection. This parasite exhibits characteristics like cytoadherence, sequestration, resetting, and aggregation, which leads to micro-circulatory obstruction in falciparum malaria [3,4]. This obstruction in the microcirculation ultimately leads to end-organ dysfunction [5][6][7][8][9].
The clinical manifestations of malaria are divided into uncomplicated malaria and severe malaria. The clinical features of uncomplicated malaria are non-specific and include fever, chills and rigors headache, malaise, muscular discomfort, lack of appetite and bitter taste in the mouth [1,10]. Severe falciparum malaria has specific diagnostic criteria [1,10]. These criteria are divided into clinical and laboratory criteria. Acute kidney injury (creatinine >3 mg/dL or urea >20 mmol/L) Asexual parasitemia>10% of infected red blood cells or >250,000/µL of blood Adults living in areas of high transmission generally come down with uncomplicated malaria, while non-immune individuals and children below three years of age are more likely to suffer from severe malaria [1].
The incidence rate of malaria declined globally between 2010 and 2017, from 72 to 59 cases per 1000 population at risk [11]. In 2017, an estimated 219 million cases of malaria occurred worldwide compared with 239 million cases in 2010 and 217 million cases in 2016 [11]. Fifteen countries in sub-Saharan Africa and India carried almost 80% of the global malaria burden and Nigeria accounted for 25% of cases worldwide [11]. In 2017, there were an estimated 435 000 deaths from malaria globally, compared with 451,000 estimated deaths in 2016, and 607 000 in 2010 [11]. Children below 5 years accounted for 61% of all malaria deaths worldwide in 2017. Africa accounted for 93% of all malaria deaths in 2017 and Nigeria accounted for 19% of all global malaria deaths [11]. All World Health Organization (WHO) Regions except the WHO Region of the Americas recorded reductions in mortality in 2017 compared with 2010. The largest declines occurred in the WHO Regions of South-East Asia (54%), Africa (40%) and the Eastern Mediterranean (10%). About 3.2 billion people remain at risk of malaria and malaria still causes an unacceptably high number of deaths in children under the age of five [12]. In Nigeria, malaria is responsible for 60% of outpatient visits to health facilities, 30% of childhood deaths of children under 1 year and 11% of maternal deaths [13]. Approximately 20% of hospital admissions and 10% of hospital deaths in Nigeria have been attributed to malaria [14]. This secondary data analysis was carried out to epidemiologically describe severe malaria in Plateau State of Nigeria, highlight the burden of the disease in the State and make recommendations for improvements on control in the face of declining global incidence of malaria infection.

Study Design
This was a retrospective secondary data analysis of severe malaria-specific Integrated Disease Surveillance and Response (IDRS) records.

Study Population
All reported severe malaria cases in the IDSR records for the period of 2013 to 2017 were reviewed. IDSR monthly epidemiological data for the years under review was obtained from the Plateau State Ministry of Health. The document contained recorded severe malaria cases from the 17 Local Government Areas of the State.

Severe Malaria Surveillance in Nigeria
Severe malaria surveillance in Nigeria is through the IDSR platform. Information flows from the health facilities, through the ward focal persons to the local government areas (LGA) disease surveillance and notification officers (DSNOs), to the States DSNOs, and then to the Federal Ministry of Health. Feedback goes through the opposite direction.

Laboratory Investigations
Capillary blood samples were used in making malaria diagnosis by microscopy or rapid diagnostic test. For microscopy, thick and thin blood smears were made on microscope slides and stained with Giemsa. For rapid diagnostic testing, capillary blood was used to make the diagnosis by immunochromatographic methods following the manufacturers' instructions.

Data Management
Relevant data from the IDSR line list were sorted, extracted, and cleaned. These included the number of cases, number of deaths and location. The data were analyzed for frequencies and proportions.  (table 1). A total of 362 severe malaria deaths were reported within the same period with a case fatality rate (CFR) of 0.94%. The highest CFR 1.43% was recorded in 2015, followed by 1.00 % in 2016. The least CFR 0.00% was recorded in 2014 (table 1). The highest CFR according to age was 3.13% among those aged 0-28 days (neonates) while the least CFR 0.05% was among those older than 40 years (table 2).

Results
The comparative monthly trend of severe malaria cases did not follow any consistent pattern during

Discussion
This study found the case fatality rate of severe malaria to be highest among neonates.
Although it is well known that malaria is an important cause of infant morbidity and mortality in sub-Saharan Africa, neonatal malaria was considered a rare condition [18]. It was believed that the fetal hemoglobin provided some protection to the newborn against malaria [19]. This, however, is not the case as studies across Africa including Nigeria have shown neonatal malaria rates ranging from 0 to 54.2% [18][19][20][21].
Whether the neonatal mortality in this review was due to severe malaria alone could not be ascertained. In any case, there is a need to intensify the administration of intermittent presumptive treatment of malaria in pregnancy and the use of long-lasting insecticide-treated bed nets among pregnant women and newborn babies. This will help in reducing cases of neonatal deaths that are caused by severe malaria in Plateau State.
The total number of cases and the CFRs of severe malaria in Plateau State has been on the downward trend since 2015 and 206 respectively. This is in keeping with the global downward trend in the morbidity and mortality of malaria in Africa [11]. In 2008, the National Malaria Control Programme in Nigeria adopted the goal of reducing to 50% the country's malaria burden by 2013 by achieving at least 80 % coverage of long-lasting impregnated mosquito nets, 20 % of houses in targeted areas receiving indoor residual spraying and treatment with two doses of intermittent preventative therapy (IPT) for 100 % of pregnant women who visit antenatal care clinics [22]. These efforts may have contributed to these downward trends.

Conclusion
Severe malaria remains a major cause of childhood mortality in Plateau State. Though the overall number of cases and deaths are declining, the CFR among neonates remains high. Case-based surveillance provided insight into understanding the epidemiology of severe malaria in Plateau State.

Recommendations
Currently, Nigeria is implementing its malaria elimination programme. Therefore, prevention and control efforts should be intensified and cased based surveillance of malaria should be enhanced in Plateau State, in order to achieve the elimination of malaria in Nigeria.