Epidemiology of tree-hole breeding mosquitoes in the tropical rainforest of Imo State, south-east Nigeria.

The study of tree-hole breeding mosquitoes was carried out in the tropical rainforest of Imo State Nigeria (two rural areas and two forest reserves in some parts of Orlu Senatorial Zone) between May-October 2002. Using standard entomological procedures, two macrohabitats (natural tree-holes and bamboo traps) and two microhabitats (leaf axils of cocoyams/pineapples and leaf axils of plantain/banana) were sampled for various mosquito species. Mosquitoes were recovered from all the various biotypes sampled. Types of mosquitoes species encountered, their relative abundance, as well as genera varied significantly during the study (p<0.05). Four genera of mosquitoes: Aedes, Culex, Anopheles and Toxorhynchites were recovered while 16 species of mosquitoes encountered include: Aedes aegypti, Ae. africanus, Ae. simpsoni, Ae. albopictus, Ae. stokesi, Ae. taylori, Ae. apicoargenteus, Culex quinquefasciatus, Cx. nebulosus, Cx. trigripes, Cx. decens, Anopheles gambiae, An. funiestus, An. coustani and Toxorhynchites viridibasis. Most of the mosquitoes showed oviposition preferences for one or more habitats. The presence of Ae. africanus, Ae. simpsoni and Ae. aegypti indicate that the study areas were at risk of yellow fever epidemic. The presence of Anopheles and Culex species ensured endemicity of malaria and filariasis, while the recovery of Ae. albopictus in this region suggests a possible outbreak of dengue fever in future if not properly controlled.

Lymphatic filariasis among the Ezza people of Ebonyi State, eastern Nigeria.

A total of 1,243 Ezza people living in 10 communities of Ebonyi State, eastern Nigeria were examined between July 2002-January 2003 for lymphatic filariasis. This is the first time a filariasis survey due to Wuchereria bancrofti has been carried out in this state. Of the 1,243 persons examined, 210 (16.9 %) had W. bancrofti microfilariae. Infection varied significantly among communities and ages (p < 0.05) but not sex-related (p > 0.05). The Ezza people are predominantly farmers and professional hired labourers. There was a close association between microfilaria rate and microfilaria -density in various age groups (r = 0.812; p < 0.01). Microfilaria density is an important measure in the epidemiology, treatment and control of human filarisis in this endemic foci. Clinical signs and symptoms of the disease include elephantiasis, hydrocoele, dermatitis and periodic fever. Clinical symptoms without microfilaraemia and microfilaraemia without clinical symptoms were also observed. Of 1,603 mosquitoes dissected, Anopheles gambiae, An. funestus and Culex quinquefasciatus showed infectivity rates of 6.3 %, 5.1 % and 6.0 % respectively. The affected persons and other key informants are unaware of the cause of the disease and attributed it to witchcraft, violation of taboo, bad water and food. Intervention strategies to be integrated into the on-going Community-Directed Treatment with Ivermectin (CDTI) project are discussed.