Analysis of trends of malaria from 2010 to 2017 in Boricha District, Southern Ethiopia

The study was conducted in Boricha district (Fig. 1), which is in the Sidama zone, Southern Ethiopia, located at 304 km from capital city of Ethiopia, Addis Ababa. It covers a total area of 588.1 km². The altitude of the district ranges from 1001 to 2076 metres above sea level, with a mean annual rainfall ranging from 801 to 1000 millimetres and the mean annual temperature ranges from 17.6 to 22.5 °C [15].

At the last census, there were 325,161 populations in the district. Most of them live in rural areas, and agriculture is the major livelihood of the community. The common agricultural crops in the district where maize, teff, sweet potato and cabbage, while perennials includes banana, coffee, khat and sugarcane [16].

Administratively, the district has 39 rural and 3 urban kebeles (the lowest administrative unit). Both public and private health facilities provide healthcare service to the community. The public facilities include one primary hospital, ten health centres and 39 health posts. The private health facilities in the district include one non-governmental clinic, one medium clinic, five primary level clinics, three drug stores and eleven drug vendors [17].

A diagnosis and treatment service of malaria has been provided in all public health facilities and one private clinic (non-governmental clinic in the district). Diagnosis is either clinical or parasitological as per national guideline recommendation. A clinical diagnosis is based on signs and symptoms of patients, with a history of having fever in the last 48 h or if patients had gone to malaria-endemic areas within the last 30 days. Parasitological diagnosis is based on multi-species RDTs or light microscopy. Treatment using clinical diagnosis is the only option to diagnose malaria if there is no RDT and microscope. Artemether-lumefantrine and a single dose of primaquine is the recommended first-line treatment for confirmed P. falciparum or mixed infection (P. falciparum + P. vivax), and chloroquine plus 0.25 mg/kg primaquine for P. vivax. Oral quinine is recommended to first trimester pregnant women and underweighted children with P. falciparum, otherwise chloroquine is a safe treatment for pregnant women and infants. Intravenous or intramuscular artesunate is the preferred first-line treatment for severe malaria, and if this is not available intramuscular artemether is the alternative treatment. Intravenous quinine infusion is given when there is no artesunate or artemether [18].

A health facility-based retrospective study was conducted to determine the trends of malaria morbidity over the 8 years (2010–2017) in Boricha district, Southern Ethiopia.

The source of information was malaria laboratory register logbook. All public health facilities (hospital, health centre and health posts and clinic) and one private clinic, the only private clinic that provides malaria diagnosis and treatment service were included in the study. All facilities use the same kind of malaria laboratory register, so that the variables captured were similar irrespective of type of health facilities.

All laboratory registers of malaria morbidity were collected from all health facilities. Then the malaria morbidity data were transferred from the registers on the prepared Excel spreadsheet. The study variables included were date of diagnosis, address of patient, gender, age, tools used for diagnosis, result of diagnosis and species of parasite. The records which missed one or more of these variables were excluded from the study.

Prior to the study, data collectors and supervisor were trained for 2 days to insure the quality of data. They were trained on the data collection tools, variables of interest, rational, objective and significance of the study as well. Similarly, the data entry clerks were trained on the same points. The whole process, data capturing and data entry was daily supervised by principal investigator to ensure the completeness and consistency.

Data were entered using EpiData 3.1 and analysed using Statistical Package for the Social Science (SPSS 20.0). Descriptive statistics was used to show the trends of malaria transmission in terms of seasons, years, gender, age and species of malaria parasite. Data were presented in percentage, tables and figures. The Pearson’s Chi square test was used to describe the associations of variables. Test of significance was estimated assuming \(\alpha\) at 0.05 and a p-value less than 0.05 was considered significant. A seasonal index was analysed for each month to obtain the seasonal pattern of malaria transmission during the study period. A seasonal index is a measure of how a particular season compares with the average season. In this study, the season is a month. The malaria incidence rate per 1000 population at risk was computed using the total population of each year as a denominator and confirmed cases of malaria as a numerator.

A total of 135,607 malaria suspected cases were examined during 2010 to 2017, of these 29,554 (21.8%) were positive for malaria. Of the total suspected cases, 85,632 (63.1%) were diagnosed by microscope and the remaining 49,975 (36.9%) by RDT. The overall positivity rate was 24,168 (28.2%) and 5386 (10.8%), respectively.

Of all confirmed cases, 15,250 (51.6%) were adults of 15 years and above, and the remaining 7230 (24.5%) and 7074 (23.9%) were children of age 5–14 and < 5 years, respectively. Children < 15 years accounted for 48.4%. Regarding the gender distribution, 51.4% of overall confirmed cases were males and 48.6% were female. The proportion of childhood malaria was high in male than female, and the reverse was seen in adults. In general, malaria infection was significantly associated with age (x² = 446.294, df = 6, p < 0.001) and gender (x² = 348.001, df = 3, p < 0.001) (Fig. 2).

The number of malaria suspected cases were increased from 2010 to 2017 with the significant fluctuations from year to year. It was sharply raised during 2010 to 2013 and then declined gradually to 2017. Unlike suspected cases, the confirmed cases were declined over the last 8 years with considerable inter-annual variations. Generally, 87% reduction of malaria morbidity was observed in 2017 compared to 2010 (Table 1).

Overall positivity rate was declined from 54.6% in 2010 to 5.0% in 2017. However, while insignificant variations of confirmed cases were observed during 2010 to 2013, the number of suspected cases during the same time period was sharply raised. Thus, the positivity rate was declined in the same time period, from 54.6 to 22.7%. The numbers of suspected and confirmed cases were declined relatively during 2014 and 2017 and so did for positivity rate (Table 1).

Plasmodium falciparum and P. vivax were the only species in study area, where P. falciparum accounted for 16,647 (56.3%) and P. vivax was 11,360 (38.4%), and the rest 1547 (5.2%) were mixed (P. falciparum + P. vivax) infection. Plasmodium falciparum was found to be the predominant species over P. vivax, except in 2013 and 2014 when P. vivax dominated. Plasmodium falciparum declined from 74.6 to 48.2% during 2010–2013, while P. vivax increased from 22.7% to 50.4% during the same period. However, from 2015 to 2017, P. falciparum again became the predominant species of the area (Table 1, Fig. 3).

Regarding the distribution of parasite species in relation to age, children in the 5–14 years age group and adults (≥ 15 years) were most affected by P. falciparum. However, P. falciparum and P. vivax were evenly distributed in children < 5 years of age (Fig. 4).

Overall malaria incidence was declined from 18.9 in 2010 to 2.2 in 2017 (mean = 12.12) per 1000 population at risk with a significant inter-annual variations. The incidence rate was high during the first 4 years, 2010 to 2013 (18.7–16.7 per 1000 population at risk). However, it was sharply declined from 11.4 in 2014 to 2.2 in 2017 per 1000 population at risk) (Fig. 5).

Remarkable variations of disease incidence were also observed in different age groups. It declined from 33.8 to 2.3 in children < 5 years of age, 13.5 to 1.7 in children 5–14 years of age and from 20.1 to 2.6 in adults ≥ 15 year age (Fig. 6).

Table 2 displays the malaria cases from 2010 to 2017. The highest number of malaria cases was recorded in 2010 (5538 cases) while the lowest was in 2017 (717 cases). The highest standard deviation was seen in 2012, which implies that, the reported cases in that year had the highest monthly variations, whereas the lowest standard deviation was recorded in 2017, implying that the monthly reported cases did not vary significantly.

The monthly analysis of malaria cases consisted of 96 months. That is, 12 month each for the 8 year period. The seasonal indices are obtained and shown in Fig. 7. The seasonal indexes plot indicates that, malaria cases in September, October, November, May, June, and July are above the average malaria cases (307.85), whiles those of March, January, February, December, August and April are below the average. From this malaria transmission in the months of November, September and October had the highest transmission whilst April had the lowest. In addition, the result of Pearson’s Chi-square analysis showed statistically significant association of malaria transmission with the seasons (x² = 325.349, df = 22, p < 0.0001).

Both, P. falciparum and P. vivax were reported in all seasons during the study period. Plasmodium falciparum peaked in September, November and May where 30.1% of overall P. falciparum was reported. On the other hand, P. vivax peaked during October, November and December where 30.3% of total P. vivax was reported (Fig. 8).