Heterogeneity in the prevalence and intensity of loiasis in five contrasting bioecological zones in Cameroon

• Published in: Transactions of the Royal Society of Tropical Medicine and Hygiene 2003-03, Vol.97 (2), p.182-187
• Main Authors: Wanji, Samuel, Tendongfor, Nicholas, Esum, Mathias, Atanga, Sali Ndindeng, Enyong, Peter
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Age Distribution; Aged; Biological and medical sciences; Cameroon; Cameroon - epidemiology; Child; Child, Preschool; Chrysops spp; Cross-Sectional Studies; Diseases caused by nematodes; epidemiology; Female; Filariases; Helminthic diseases; Humans; Infant; Infant, Newborn; Infectious diseases; Loa loa; Loaiasis; loiasis; Loiasis - epidemiology; Male; Medical sciences; Middle Aged; Parasitic diseases; Prevalence; Residence Characteristics
• ISSN: 0035-9203; 1878-3503
• DOI: 10.1016/S0035-9203(03)90114-3

The prevalence and intensity of loiasis were studied in 4532 individuals selected from 42 villages from 5 contrasting bioecological zones in Cameroon from February to July 2001. The individuals were examined for Loa loo microfilaraemia using the thick blood film method. Loiasis was heterogeneously distributed from one bioecological zone to another. The occurrence of the infection was largely related to environmental factors favouring the breeding of Chrysops vectors. The mean prevalence of infection varied from 0% in the grassland savannah, 6.6% in the deciduous equatorial rainforest, 9.7% in the dense-humid equatorial rainforest, to 33.3% in the forested savannah. Loiasis was totally absent in the grassland savannah. The intensity of loiasis infection (L. loa microfilariae per millilitre [mf/mL] of blood) increased with an increase in prevalence, varying from 0 mf/mL in the grassland savannah, 325 mf/mL in the deciduous equatorial rainforest, 433 mf/mL in the dense-humid equatorial rainforest, to 3125 mf/mL in the forested savannah. The proportion of individuals with high (> 8000 mf/mL) and very high (> 30 000 mf/mL) L. loa microfilaraemia was greater in bioecological zones with a higher prevalence of L. loa. These results will be valuable for the prediction of loiasis endemicity in different ecological zones of Central Africa and for the refinement of the existing geographical model for the mapping of loiasis.