A simplified model for predicting malaria entomologic inoculation rates based on entomologic and parasitologic parameters relevant to control.

Abstract

Malaria transmission intensity is modeled from the starting perspective of individual vector mosquitoes and is expressed directly as the entomologic inoculation rate (EIR). The potential of individual mosquitoes to transmit malaria during their lifetime is presented graphically as a function of their feeding cycle length and survival, human biting preferences, and the parasite sporogonic incubation period. The EIR is then calculated as the product of 1) the potential of individual vectors to transmit malaria during their lifetime, 2) vector emergence rate relative to human population size, and 3) the infectiousness of the human population to vectors. Thus, impacts on more than one of these parameters will amplify each other's effects. The EIRs transmitted by the dominant vector species at four malaria-endemic sites from Papua New Guinea, Tanzania, and Nigeria were predicted using field measurements of these characteristics together with human biting rate and human reservoir infectiousness. This model predicted EIRs (Ϯ SD) that are 1.13 Ϯ 0.37 (range ϭ 0.84-1.59) times those measured in the field. For these four sites, mosquito emergence rate and lifetime transmission potential were more important determinants of the EIR than human reservoir infectiousness. This model and the input parameters from the four sites allow the potential impacts of various control measures on malaria transmission intensity to be tested under a range of endemic conditions. The model has potential applications for the development and implementation of transmission control measures and for public health education.

The availability of potential hosts as a determinant of feeding behaviours and malaria transmission by African mosquito populations

“…As previously, we assume that each malaria transmission focus is a discrete entity within which the vector, human and parasite populations interact with each other and we ignore exchanges with other nearby foci (Killeen et al, 2000b). For ease of reference and clarity, all symbols and definitions are listed in Table 1.…”

“…Vector species abundance, longevity, feeding cycle length and bloodmeal host choice are key predictors for the transmission intensity of insect-borne diseases such as malaria (Onori & Grab, 1980;Killeen et al, 2000b), dengue (Focks et al, 1995) and sleeping sickness (Rogers & Randolph, 1991). These parameters undoubtedly depend on the effort expended by the vector in the pursuit of bloodmeals and the relative availability of different species for bloodmeal acquisition.…”

“…Because the entomological inoculation rate (EIR) of malaria is proportional to the square of the proportion of bloodmeals taken from humans (Q h ), it is very sensitive to changes in vector host choice (Koella, 1991;Killeen et al, 2000b). The practice of using domestic animals, which cannot act as reservoirs, as decoy hosts for pathogentransmitting vector populations is referred to as zooprophylaxis (Service, 1991).…”

Rapid assessment of malaria risk using entomological techniques: taking an epidemiological snapshot

“…For example, the ratio of human to mosquito population densities, mosquito lifetime infectiousness and human infectious reservoir can be used in a relatively simple model for estimating EIR and the impacts of control measures upon it (Killeen et al 2000b;2000a). All of these parameters are measurable in the described RA approach.…”

“…Models for malaria transmission place great emphasis on the mosquito (Killeen et al 2000b;Koella 1991), so information gathered about the vector is crucial. Gathering vector data is also less dependent upon human compliance.…”