Five years of malaria control in the continental region, Equatorial Guinea

Abstract

Background: A successful malaria control programme began in 2004 on Bioko Island, Equatorial Guinea. From 2007, the same multiple malaria interventions, though reduced in scope for funding reasons, were introduced to the four mainland provinces of Equatorial Guinea (the continental region) aiming to recreate Bioko's success. Two provinces received long-lasting insecticidal nets (LLINs) and two provinces received biannual indoor residual spraying (IRS). Enhanced case management and communications were introduced throughout.

Methods: Estimates of intervention coverage and indicators of malaria transmission for 2007 to 2011 were derived from annual malaria indicator surveys (MIS). Results were complemented by health information system (HIS) and entomological data. The personal protection offered by LLINs and IRS against Plasmodium falciparum infection was estimated with logistic regression.

Results: The estimated proportion of children aged 1-4 using either an LLIN the previous night or living in a house sprayed in the last six months was 23% in 2007 and 42% in 2011. The estimated prevalence of P. falciparum in children aged 1-4 was 68% (N=1,770; 95% confidence interval [CI]: 58-76%) in 2007 and 52% (N=1,602; 95% CI: 44-61%) in 2011. Children 1-4 years had lower prevalence if they used an LLIN the previous night (N=1,124, 56%; adjusted odds ratio [aOR] 0.64, 95% CI: 0.55-0.74) or if they lived in a sprayed house (N=1,150, 57%; aOR 0.80, 95% CI: 0.62-1.03) compared to children with neither intervention (N=4,131, 66%, reference group). The minority of children who both used an LLIN and lived in a sprayed house had the lowest prevalence of infection (N=171, 45%; aOR 0.52, 95% CI: 0.35-0.78). High site-level intervention coverage did not always correlate with lower site-level P. falciparum prevalence. The malaria season peaked in either June or July, not necessarily coinciding with MIS data collection.

Conclusions: Though moderate impact was achieved after five years of vector control, case management, and communications, prevalence remained high due to an inability to sufficiently scale-up coverage with either IRS or LLINs. Both LLINs and IRS provided individual protection, but greater protection was afforded to children who benefitted from both.

Figure 1

Timing of malaria interventions, Equatorial Guinea 2007 to 2011. A malaria indicator survey (MIS- blue solid lines) was carried out prior to implementation of any interventions in 2007 and then annually. Subsequently two provinces received interventions in 2007. Indoor residual spraying (IRS- lines with a long dash and two dots) commenced in Litoral (L, the coastal province) and long lasting insecticide treated bed nets (LLINs- dashed lines) were distributed in Centro Sur (CS, the province immediately east of Litoral). After the second MIS Artemisin combination therapy (Artesunate 50 mg + Amodiqaquine Hydrochloride 200 mg: denoted as ACT- green lines) was introduced region-wide and the remaining two provinces commenced vector control. Kie-Ntem (KN, the province in the far north east of the region) received IRS and Wele-Nzas (WN, the province in the south east of the region) received LLINs. Pregnant women attending ante-natal clinics region-wide received LLINs from 2009. Intervention activity stopped in August 2011. Information, education and communication campaigns ran throughout the intervention period as described in the text. Training for laboratory staff was carried out from 2009 until June 2011. *In water locked communities where IRS was not feasible.

Figure 2

Prevalence of P. Falciparum malaria and 95% confidence intervals by age in children under 15 years, Equatorial Guinea. The prevalence of infection was highest among eight year olds in both 2007 and 2011.

Figure 3

Cases of outpatient attendances and inpatient admissions for malaria in children aged one to four, Equatorial Guinea. Case numbers are those with diagnosed outcome of malaria recorded and may include repeat admissions for the one child. The grey vertical lines denote the period during which the annual malaria indicator survey (MIS) was carried out. In 2009 the MIS took place prior to the peak in case numbers, whereas in 2010 the MIS took place during the peak in case numbers. The figure shows the seasonality in case numbers.

Figure 4

Sporozoite rate by month and year for mosquitoes collected at 17 sentinel sites, Equatorial Guinea. The grey vertical lines denote the period during which the annual malaria indicator survey (MIS) was carried out. The peak sporozoite rate in 2007 occurred during the MIS. Sporozoite rates in late 2009 and 2010 were very high. By 2011 the sporozoite rates had dropped down to 2007 levels again.