Larval ecology of Anopheles coluzzii in Cape Coast, Ghana: water quality, nature of habitat and implication for larval control

Abstract

BackgroundThere is a growing interest in larval control intervention to supplement existing malaria control strategies, particularly in urban areas. However, effective implementation requires a good understanding of habitat ecology of Anopheles mosquitoes. Clean water bodies have long been reported by several studies as a preferred breeding habitat for Anopheles gambiae. Other studies have also reported the breeding of An. gambiae in polluted water bodies. However, the term clean or polluted is mostly based on visual examination and is not well defined. This study was conducted with the aim of assessing water quality in Anopheles breeding habitats and the practicability of larval control in Cape Coast, Ghana.MethodsA larval survey was conducted for 15 months in Cape Coast. In individual breeding habitats, habitat characteristics, physicochemical parameters and bacterial fauna were measured in both Anopheles positive breeding (APL) habitats and habitats colonized by only Culex species. The sibling species of An. gambiae were identified using PCR assay.ResultsAnopheles coluzzii dominated in almost all the APL habitats found in this study. The habitats had high levels of salinity and ammonium ions. However, ammonium ions were significantly higher (p = 0.001) in habitats colonized by only Culex larvae compared to APL habitats. About 47 % of the habitats that were colonized by only Culex larvae had no measurable dissolved oxygen while An. coluzzii was absent in such habitats. High concentration of faecal bacteria confirmed faecal contamination in both groups of breeding habitats.ConclusionsFrom the results, it was evident that larval stages of An. coluzzii have tolerance to high levels of salinity and organic pollution in breeding habitats. However, its level of tolerance to organic pollution is probably lower than Culex larvae. The nature of breeding habitats found in the city demonstrates the opportunistic behaviour of An. coluzzii and how its breeding requirements are so intimately intertwined with the haphazard and uncontrolled human activities in the urban area. Considering the nature of APL habitats, larval control intervention could greatly reduce Anopheles population. However, improving basic hygiene and sanitation in the city could even make larval control intervention more practical and cost effective.

Natural variation in physicochemical profiles and bacterial communities associated with Aedes aegypti breeding sites and larvae on Guadeloupe and French Guiana

“…Our results confirm that Ae. aegypti does not breed only in clear water, as it can breed in containers with high turbidity (> 133 FNU), high DCO (> 242 mg/L) and low dissolved oxygen, nearly reaching anoxia, like Culex quinquefasciatus mosquitoes [53]. These findings are consistent with reports of successful Ae.…”

Reusing larval rearing water and its effect on development and quality of Anopheles arabiensis mosquitoes

“…The availability of sufficient water of a reliable quality is an essential requirement for mosquito mass rearing in support of SIT programmes and others relying on large-scale production of mosquitoes. An extensive literature exists describing the characteristics of mosquito larval habitats in nature (e.g., [ 33 – 36 ]). Every Anopheles species has its preferred water bodies for oviposition, depending on climate, physical geography and human activities, among other factors.…”

“…gambiae complex. Anopheles coluzzii was found cohabiting with Culex species in choke gutters and other organically polluted habitats [ 36 ], and it is reported that in some West African cities in the savanna, An. arabiensis has developed the ability to breed in larval habitats contaminated by waste waters [ 41 , 42 ].…”

Bacterial populations of mosquito breeding habitats in relation to maize pollen in Asendabo, south western Ethiopia

“…The concentration of ammonia nitrogen was lower and this might be the result of the transfer of volatile and semi volatile compounds (ammonia) from water bodies to the atmosphere (Schindler, 2001). The amount of ammonium concentration was low as compared to finding report by Kudom (2015). The small amount of ammonium concentration in the habitat of larvae suggests that larval excretion of NH 4 + was being balanced by its removal through microbial metabolism.…”