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impetus
 

Human-to-mosquito transmission efficiency
observed human-to-mosquito transmission efficiencies
Fig.: Frequency distribution of mosquito human-to-mosquito transmission efficiencies (in %) determined by various malaria studies (cp. table).

Measuring human-to-mosquito transmission efficiencies

The human-to-mosquito transmission efficiency rate is the proportion of mosquito bites on infectious humans which infect susceptible mosquitoes with sexual malaria parasites. The infectiousness of mosquitoes can be determined by using blood from gametocyte carriers, it is either measured by direct skin feeding or by membrane feeding (Bonnet et al. 2002). However, the best method for estimating the infectiousness of a human population is to feed laboratory-reard Anopheles on a representative population sample without regard to the presence of gametocytes (Boudin et al. 1991a).

Observations

Obviously not all Anophelines feeding on gametocyte-infected hosts become infected. Human-to-mosquito transmission efficiencies are generally lower than 40%, and for the majority of the trials the infectiousness is higher than 20% (Fig.). Muirhead-Thomson (1954) observed that not all anophelines feeding on gametocyte-infected hosts are infected. The 'best infectors' infected only about 30% of the mosquitoes feeding on them. On the other hand cryptic gametocytemia can result in mosquito infections (Ross et al. 2006).

Age dependence

Children are most likely to infect mosquitoes (e.g. Bonnet et al. 2003). There is a general decrease with age in the infectiousness but even highly immune hosts contribute to the infectious reservoir (Ross et al. 2006). A large proportion of infections results on feeding on adults. That is due to their greater attractiveness and therefore most blood meals to vector mosquitoes are provided by this age group (Killeen et al. 2006).

Transmission blocking immunity

One factor reducing the infectivity of gametocytes to mosquitoes is transmission blocking immunity, i.e. a specific immunity acquired in humans. Immune factors, ingested with the blood meal, inhibit or block the development of the free sexual stages: gamete, zygote, and ookinete, which have common antigens with gametocytes (Boudin et al. 2005).
  • Raw data: colon separated values (ASCII file)

    • country place long [°E] lat [°N] M1 YYY1 M2 YYY2 c Ub Ua Up note Refs
    Burkina Faso near Bobo-Dioulasso -999.00 -99.00 NA 1985 NA 1987 37.2 R R2 R all ages; after experimental feeding on heavy carriers of gametocytes Boudin et al. 1991a
    Cameroon Bondi 12.19 3.86m NA 1998 NA 2000 11.8 NA NA R adults (>14 years); area: degraded forest Bonnet et al. 2003
    Cameroon Bondi 12.19 3.86m NA 1998 NA 2000 36.9 NA NA R children (0-14 years); area: degraded forest Bonnet et al. 2003
    Cameroon district of Mengang -999.00 -99.00 NA NA NA NA 12.1 NA NA R children and adults (>5 years); membran feeding Bonnet et al. 2002
    Cameroon district of Mengang -999.00 -99.00 NA NA NA NA 19.4 NA NA R children and adults (>5 years); direct skin feeding Bonnet et al. 2002
    Cameroon Mengang 12.05 3.88i NA 1998 NA 2000 15.5 NA NA R children (0-14 years); area: degraded forest Bonnet et al. 2003
    Cameroon Mengang 12.05 3.88i NA 1998 NA 2000 7.7 NA NA R adults (>14 years); area: degraded forest Bonnet et al. 2003
    Cameroon Mengang district -999.00 -99.00 NA NA NA NA 33.0 NA NA R age over 4 years Boudin et al. 2005
    Cameroon Yaoundé, Messa quarter -999.00 -99.00 10 1990 01 1993 18.6 NA NA U children and adults (4-60 years) Tchuinkam et al. 1993
    Cameroon Yaoundé, Messa quarter -999.00 -99.00 NA NA NA NA 12.8 NA NA U membran feeding with blood of 65 Plasmodium falciparum gametocyte carriers (6-36 years) Mulder et al. 1994
    Cameroon Yaoundé, Messa quarter -999.00 -99.00 NA NA NA NA 12.8 NA NA U membran feeding with blood of 65 Plasmodium falciparum gametocyte carriers (6-36 years) Mulder et al. 1994
    Cameroon Yaounde, urban district -999.00 -99.00 NA NA NA NA 20.0 NA NA U age over 4 years Boudin et al. 2005
    Gambia, The 5 villages around Farafenni -16.57 13.47p 05 2003 10 2003 43.0 NA NA R membrane feedings on blood from patients following drug treatment Nwakanma et al. 2006
    Gambia, The 5 villages around Farafenni -16.57 13.47p 05 2003 10 2003 6.4 NA NA R 47 trials of membran feeding on blood from gametocyte carriers (5-45 years) Nwakanma et al. 2006
    Gambia, The near Farafenni, north bank villages -999.00 -99.00 NA NA NA NA 56.5 NA NA NA children (1-19 years) Drakeley et al. 2000
    Gambia, The near Farafenni, north bank villages -999.00 -99.00 NA NA NA NA 80.0 NA NA NA adults (>19 years) Drakeley et al. 2000
    Ghana ? -999.00 -99.00 01 1952 10 1952 0.0 NA NA ? two adults (>14 years) Muirhead-Thomson 1954
    Ghana ? -999.00 -99.00 01 1952 10 1952 30.0 NA NA ? 40 children (0-14 years) Muirhead-Thomson 1954
    Ghana Accra -999.00 -99.00 NA NA NA NA 50.9 NA NA U all ages Draper 1953
    Ghana Weija -99.00 -999.00 01 1952 10 1952 26.6 NA NA R children (0.8-10 years) Muirhead-Thomson 1954
    Liberia ? -999.00 -99.00 ? ? ? ? 20.1 NA NA ? adults (>14 years) Muirhead-Thomson 1957
    Liberia ? -999.00 -99.00 ? ? ? ? 21.6 NA NA ? children (0-14 years) Muirhead-Thomson 1957
    Liveria village -99.00 -999.00 12 1955 11 1956 19.1 NA NA R children(0-4 years) Muirhead-Thomson 1957
    Liveria village -99.00 -999.00 12 1955 11 1956 20.1 NA NA R children(>14 years) Muirhead-Thomson 1957
    Liveria village -99.00 -999.00 12 1955 11 1956 23.3 NA NA R children(5-14 years) Muirhead-Thomson 1957
    Nigeria Kaduna area -999.00 -99.00 05 1963 08 1963 20.0 NA NA R low gametocyte density Service 1965
    Nigeria Kaduna area -999.00 -99.00 05 1963 08 1963 50.0 NA NA R high gametocyte density Service 1965
    Nigeria Lagos -999.00 -99.00 NA NA NA NA 46.6 NA NA U children Draper 1953
    Nigeria village in Yoruba country -999.00 -99.00 11 1951 12 1951 9.0 NA NA R children (0-10 years) Draper 1953
    Papua New Guinea Buksak -999.00 -99.00 02 1986 12 1986 48.1 NA NA R - Burkot et al. 1990
    Papua New Guinea Butelgut, Mebat, Sah, Buksak -999.00 -99.00 NA 1985 NA 1985 37.9 NA NA R all ages Graves et al. 1988
    Senegal Thies -16.93 14.80i NA NA NA NA 25.0 NA NA R age over 4 years Boudin et al. 2005
    Tanzania Kisegese -999.00?? -99.00 NA NA NA NA 26.7 NA NA NA adults (>19 years) Drakeley et al. 2000
    Tanzania Kisegese -999.00?? -99.00 NA NA NA NA 44.1 NA NA NA children (1-19 years) Drakeley et al. 2000
    Thailand Phra Phutthabat 100.8 14.72i 06 1965 10 1967 23.2 NA NA NA children and adults (12-60 years); rainy season Rutledge et al. 1969
    Thailand Phra Phutthabat 100.8 14.72i 06 1965 10 1967 37.9 NA NA NA children and adults (12-60 years); cool season Rutledge et al. 1969
    Thailand Phra Phutthabat 100.8 14.72i 06 1965 10 1967 9.7 NA NA NA children and adults (12-60 years); hot season Rutledge et al. 1969

    Abbreviations

    countrycountry of the study site
    placename of the location of the study site
    longlongitude [°E]; -999.00: position unknown
    latlatitude [°N]; -99.00: position unknown; sources of latitude/longitude: a: Hay et al. 2005a, b: Hay et al. 2000b, p: taken from the paper, m: published map, i: http://www.heavens-above.com/countries.aspx
    M1month of the study start
    YYY1year of the study start
    M2month of the study end
    YYY2year of the study end
    chuman-to-mosquito transmission efficiency, i.e. the proportion of mosquito bites on infectious humans which infect susceptible mosquitoes [%]
    UbR=rural, I=irrigated rice, U= urban area; source: Hay et al. (2000b)
    Uaas defined by Hay et al. (2005a): PU=peri-urban (population densities of 250-1,000 persons per km2), R1=rural 1 (population densities of 100-250 persons per km2), R2=rural 2 (population densities of < 100 persons per km2), U=urban (population densities of > 1,000 persons per km
    UpR=rural area, I=irrigation/permanent stream or river, U= urban area; derived from the particular reference
    notenotes
    Refsreferences
    NArefers to data that was not available in the reference
    ?the question mark refers to references that were not checked, since they were not available