SOURCE:

Faculty: Biosences
Department: Parasitology And Entomology

CONTRIBUTORS:

Egbuche, C.M;
Onyido, A.E;

ABSTRACT:

Malaria is still a major public health problem despite decades of control efforts. This is largely due to variations in malaria parasite transmission dynamics in different places. The differences in malaria risk can be explained by Anopheles species of local importance and their ecology, hence this study.The aim was to investigate the ecology of Anopheles mosquitoes and malaria endemicityin Anambra East LGA of Anambra State.The objectives were to determine: malaria vector species composition and the climatic factors influencing their survival; breeding ecology, physicochemical and biological factors operating in Anophelesspecies habitats; biting and resting behavior of the Anopheles mosquitoes; human blood index and sporozoite rate of Anopheles mosquitoes; malaria parasite prevalence and intensity. The research was a 12 months longitudinal study in systematically selected towns (Aguleri, Igbariam and Nsugbe). Adult Anophelesmosquitoeswere collected monthly from 10 indoor and outdoor locations using Pyrethrum Knockdown Collectionand Human Bait collection Methods respectively. Larvae of Anopheles mosquitoeswere collected from their potential breeding sites using dipping method.The Anopheles speciescollected were identified using morphological and molecular techniques. Data on climate was obtained from Nigerian Meteorological Agency.The water quality in the breeding sites was analyzed for biological, physical and chemical characteristics. Abdominal conditions and WHO indices were used to determine their biting and resting behaviour. ELISA was used to determine the human blood index and sporozoite rates of the Anopheles species. Giemsa stained thick and thin blood films were used to determine malaria parasite prevalence and intensity. Statistical analysis was done at 5% level of significance. A total of 8181 female Anopheles mosquitoes consisting of 4127 (50.4%) larvae and 4054 (49.6%) adults were collected. Four Anopheles species namely 5734 (70.1%) An. gambiaes. s, 1493 (18.2%) An. funestus, 513 (6.3%) An. moucheti and 441 (5.4%) An. nili were identified (P < 0.05). The correlation between rainfall and An. gambiaes. s. abundance was significantly strong (r = 0.66). The Anopheles mosquitowere found to breed in basin (2.8%), clay pots (8.8%), canoes (11.4%), drainage channels (14.2%), head pans (0.4%), plastic drum/container (13.4%), puddle (10.2%), river banks(26.8%) and swamps (12.0%); (P < 0.05). Canoe, plastic containers and river banks showed 100% monthly availability. Biotic factors in the breeding habitats included: six bacterial isolates, six fungal isolates, earthworm, other mosquito larvae, fish, tadpole, algae and vegetations. Larval abundance of some Anopheles species showed significant correlation with chemical oxygen demand, salinity, and iron concentration. An. gambiaes. s., was the most abundant species in indoor 2582 (81.3%) and outdoor 658 (74.9%)locations (P < 0.05). Overall proportion of Anopheles mosquitoes biting was 66.2% indoor and 33.8% outdoor (P < 0.05). The overall proportion of gravid Anopheles mosquitoes was 60.8% outdoor and 39.2% indoor (P > 0.05). Their peak biting time ranged from 10.00 pm - 3.00 am.Human Blood Index of 95.0%, overallP. falciparum sporozoite rate of 2.5% and EIR of 0.123 bites/person/nightwere observed. The prevalence of malaria parasite in the study area was 61.2% with overall mean malaria parasite intensity of 263.4±3.2 malaria parasites / µl of blood. An. gambiaes. s., An. funestus, An. mouchetiand An. nili transmit malaria parasites in the area. They bite and rest both indoor and outdoor. Riverbanks, swamps and parked canoe sustained their population throughout the year, leading to stable malaria transmission in the area. Adequate use of protective measures throughout the year is therefore recommended.