Anopheles gambiae s.s. was the dominant anopheline mosquito and the main sibling species of the An. gambiae complex in the surveyed area. This concurs with findings in coastal savanna areas of Ghana [30, 31] and elsewhere in Africa . Anopheles melas was absent amongst the human biting populations of the An. gambiae complex, although it is known to be a vector along the coast of West Africa [33–35]. This species therefore, appears not to play a role in malaria transmission in the coastal areas of Ghana. Other anophelines recorded but in reduced numbers included An. funestus and An. pharoensis, a finding which is similar to earlier work in the nearby coastal savanna area of Prampram .
The Anopheles gambiae s.s. M molecular form was dominant and the main malaria vector identified. The molecular M-form has been reported to have a higher vectorial capacity . This fact is corroborated in our findings where a high circumsporozoite antigen rate was recorded and which was relatively higher compared to earlier studies in coastal savanna areas of Ghana [30, 31]. The M-form is known to breed in permanent and semi-permanent water swamps in floodable river banks favorable to its development . The low occurrence of the molecular S-form in our study during the dry season is also not surprising as this form is known to be well adapted to rainfall breeding sites [38, 39]. Although these molecular forms are thought to represent incipient species [40, 41] the factors underlining their co-existence in this area are still unclear, and deserve further investigation.
Peak indoor infective bites were also observed between the hours of 12.00 - 01.00 am when most of the inhabitants were in bed; hence suggesting that if inhabitants slept under impregnated bednets, human-vector contact and thus the risk of infective bites could be reduced. However, the majority of the infective bites occurred outdoors between the hours of 12.00-01.00 am and 03.00-04.00 am which coincides with peak biting densities of this vector. An interesting finding was the distribution of sporozoite-laden bites during the night, which indicated that malaria transmission in the study site occurred in the evenings after 09.00 pm till near daybreak (04.00 - 05.00 am). This has important epidemiologic implications as some of the inhabitants, involved in domestic and other activities are already out of bed (by 04.00 am) so therefore, increases their exposure to infective inoculations.
The high degree of outdoor behavior contrasts with a greater endophilic tendency displayed by this species in earlier studies in nearby coastal area of Ghana . This observation is however, not surprising as heterogeneity in biting pattern is common place even within local scales. Equally, early evening biting activity by An. gambiae s.s. was evident, a pattern which contrasts with that reported by  where no biting occurred during the early hours of the morning. The basis for the combined high degree of outdoor biting and early biting populations remains unclear, but could be in response to prolonged use of insecticides indoors . Such characteristics would tend to reduce the impact of control strategies directed towards the indoor biting fraction of the population.
This variation in feeding behavior within vector species may have a genetic basis , which raises the possibility that vector control measures using insecticides could select for genotypes which are least likely to encounter the intervention. The early and outdoor biting populations may represent behavioral shifts as a consequence of phenotypic plasticity or evolutionary change within vector populations which remains unclear . Regardless of the mechanism, such behavioral plasticity limits contact between vectors and insecticides, thus diminishing the effectiveness of the interventions that use them [9, 43]. This outdoor biting activity has been linked to persistent malaria transmission in the face of mounting control measures indoors . Thus there have been calls for innovative measures to develop new tools to fight malaria transmission by exploiting the ecology of the vector through an integrated approach to complement current vector control strategies [19, 42, 44].
No infected An. funestus was recorded during the study period. Previous studies in other coastal areas of Ghana [30, 31] have implicated this species as the second most important vector after An. gambiae s.l. Therefore, the absence of infection in An. funestus might be attributable to the low numbers caught biting; hence a longer period of survey in the rainy season is required to ascertain whether An. funestus is a significant vector at Kpone-on-Sea.
The observed parity rates for the anophelines were high. This indicates that older populations of mosquitoes tend to accumulate with time. This allows for increased feeding frequencies and thus, increased chances of the vectors becoming infected or even re-infected during subsequent feeding [45, 46]. Our analysis showed that a higher proportion of the engorged An. gambiae had fed on humans. This finding confirms the anthropophilic tendencies displayed by this species throughout most of its distribution , making it the most efficient malaria vector in Africa. Host blood meal detection assay was, however, conducted on only the few number of anophelines sampled using PSC. Inefficiencies of collectors could introduce bias in the number of mosquitoes that have fed on humans using human landing catches. As such, only anopheline mosquitoes collected by PSC were assayed for blood meal analyses. Few anophelines were captured using this strategy although the reason for the low captures is unclear given adequate sampling regimes that were conducted. It has been noted however, that during the dry season, as a survival strategy, adults may hide in shelters such as rodent burrows, abandoned houses and wells, thereby minimizing the chances of their detection through pyrethrum spray collections .
Malaria transmission dynamics have been shown to vary greatly across Africa with inoculation rates varying from as low as 0.1 to over 1000 infective bites/person/year (ib/p/y) [7, 49]. Generally in Africa, when the EIR <10, the area is considered to have unstable malaria and where EIR > 100, malaria is said to be stable . Our results therefore suggest that malaria endemicity at Kpone-on-Sea remains variable, which depends on environmental and demographic conditions such as rainfall, vegetation cover, human population density and land use patterns. The observed annual inoculation rates in Kpone-on-Sea is, however, higher relative to other coastal areas of Ghana [30, 31] probably due to a multiplier effect of the density and high biting rate of this species.