Malaria prevalence, management trends and the knock down resistance profile of Anopheles gambiae in Mbakong, Cameroon
Cheng, Ndong Ignatius
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Malaria remains a scourge in the world. Recent efforts to combat malaria combine chemotherapy and vector control. Cameroon in 2004 adopted WHO 2001 recommendations and changed her malaria treatment guidelines from monotherapy to artemisinin combination therapy (ACT) as the first-line treatment for uncomplicated malaria and scaled up use of pyrethroid treated nets. Here, we report an investigation into the malaria admissions, management trends and knock down resistance of Anopheles gambiae s.s. and An. coluzzii under the new policy from 2006-2012. Data was collected from hospital registers and analysed using Statistical programmes (SPSS and SAS). Mosquitoes were caught using human landing catches and kdr mutations were detected using PCR. Of the 4,230 febrile patients received from 2006-2012, 29.3% were confirmed malaria positive with males having a slightly higher risk of having malaria than females (OR=1.08, 95% CI 0.94-1.25). Malaria prevalence fluctuated with a major peak in 2006 and a minor peak in 2011. A practically visible and significant association was observed between age group, gender and having a malaria positive result (Pearson X2=153.675, p<0.00001, Cramer’s V=0.352). The age groups most affected were 5-<14 years and 1-<4 years. Using the Cubic model, malaria prevalence revealed a fluctuating but declining trend over time which was statistically significant and practically visible (R2=0.638, p<0.0001). Treatment data demonstrate that from 2006-2012, a total of 2,556 (60.43%) of the prescriptions dispensed to patients were for an anti-malarial, 1,989 (47.02%) for antibiotics and 1,935(45.74%) were for antipyretics. The anti-malarials prescribed were ACT 1,216 (47.56%), quinine 1,044 (40.83%) or SP 296(11.62%). Of those prescribed an ACT, only 441(36.27%) had a positive malaria result while quinine intake was recorded in 566 (54.21%) patients positive for plasmodium. ACT prescription increased from 23% in 2007 to between 44%-45% in 2008-2009 while quinine prescription dropped from 38% in 2007 to13% in 2009 (r=-0.43, p>0.05). In terms of the kdr mutations, 41.18% of analysed specimens were found to carry the L1014F mutation; 20.59% specimens carried the homozygous susceptible genotype, 19.12% the heterozygous and 1.47% specimen carried the homozygous resistant; 20.83% specimens carried the heterozygous genotype, 2.08% the homozygous resistant genotype while 2.70% carried the homozygous susceptible genotype. This was consistent with Hardy Weinburg equilibrium. The frequency of the L1014S mutations was 31% within the sampled population with 31% within An. coluzzii and 24% within An. gambiae. The frequencies of both the heterozygous and susceptible genotypes were 11% each, while the homozygous genotype was 2% in An. gambiae samples. The frequency of the L1014S mutation in An. coluzzii was 19% in the homozygous susceptible and 12% in the heterozygous state. The changes in the treatment guidelines probably resulted in fluctuating but declining malaria admissions from 2006 to 2012. Over diagnoses and over treatment was common. Control efforts need to be stepped up, with specific focus on the vulnerable groups. In Mbakong the kdr mutation frequencies are higher in An. coluzzii than in An. gambiae. This could negatively affect the success registered under the new policy.
- Health Sciences