1921
Volume 71, Issue 2_suppl
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645

Abstract

Establishing the relationship between transmission intensity and health outcomes is crucial for the planning of long-term malaria control programs. Unfortunately this is fraught with methodologic difficulties. In this report, we address some of these problems by considering some important parameters that have previously been ignored. One important consideration is that the incidence of infection for malaria is much lower than entomologic inoculation rates (EIRs), especially at higher transmission levels. Moreover, biting rates of malaria vectors per host depend on his or her biomass and thus age. We propose an algorithm for estimating human infection rates from the EIR with allowance for these two factors. We then re-analyzed 1) data on EIR and age-specific incidence of clinical malaria in two villages in Senegal and 2) a survey of infant and child mortality rates across Africa. In each case, we review analyses of incidence in relation to the EIR and carry out a new analysis of morbidity and mortality rates in relation to the estimated incidence of infection (). Reduction in malaria transmission may result in a shift of acute malaria attacks to older ages, and thus have little impact on life-time risk of clinical attacks. However, our analysis of the Senegalese data indicates that the peak incidence rate of disease relative to infection rates is in the youngest age groups in both the villages of Dielmo (EIR = 200 infectious bites per year) and Ndiop (EIR = 20). This suggests that simple models of acquired clinical immunity can explain age-incidence profiles better when incidence is expressed in relation to , than when expressed in relation to the EIR. Relationships of malaria transmission intensity (in endemic areas) with overall mortality are very different from those with acute morbidity. Infant mortality rates (IMRs) decrease substantially when the EIR is reduced, probably largely because of prevention of indirect mortality. However, we were are not yet able to draw strong conclusions about the shape of relationships between the IMR and because many of the available data points have similar values of . The effects of transmission reduction on mortality rates in older age groups are also uncertain. However, it is clear that reduction of exposure during infancy is not reflected in increased mortality at older ages.

Loading

Article metrics loading...

The graphs shown below represent data from March 2017
/content/journals/10.4269/ajtmh.2004.71.80
2004-08-01
2019-11-14
Loading full text...

Full text loading...

/deliver/fulltext/14761645/71/2_suppl/0700080.html?itemId=/content/journals/10.4269/ajtmh.2004.71.80&mimeType=html&fmt=ahah

References

  1. Trape JF, Rogier C, 1996. Combating malaria morbidity and mortality by reducing transmission. Parasitol Today 12 : 236–240. [Google Scholar]
  2. Smith T, Leuenberger R, Lengeler C, 2001. Child mortality and malaria transmission intensity in Africa. Trends Parasitol. 17 : 145–149. [Google Scholar]
  3. Boreham PFL, Chandler JA, Jolly J, 1978. Incidence of mosquitos feeding on mothers and babies at Kisumu, Kenya. J Trop Med Hyg 81 : 63–67. [Google Scholar]
  4. Carnevale P, Frezil JL, Bosseno MF, Lepont F, Lancien J, 1978. Study of agressivity of Anopheles gambiae A in relation to age and sex of human subjects. Bull World Health Organ 56 : 147–154. [Google Scholar]
  5. Port GR, Boreham PFL, Bryan JH, 1980. The relationship of host size to feeding by mosquitoes of the Anopheles gambiae Giles complex (Diptera, Culicidae). Bull Entomol Res 70 : 133–144. [Google Scholar]
  6. Beier JC, Oster CN, Onyango FK, Bales JD, Sherwood JA, Perkins PV, Chumo DK, Koech DV, Whitmire RE, Roberts CR, 1994. Plasmodium falciparum incidence relative to entomologic inoculation rates at a site proposed for testing malaria vaccines in western Kenya. Am J Trop Med Hyg 50 : 529–536. [Google Scholar]
  7. Beier JC, Killeen GF, Githure JI, 1999. Short report: entomologic inoculation rates and Plasmodium falciparum malaria prevalence in Africa. Am J Trop Med Hyg 61 : 109–113. [Google Scholar]
  8. Charlwood JD, Smith T, Lyimo E, Kitua AY, Masanja H, Booth M, Alonso PL, Tanner M, 1998. Incidence of Plasmodium falciparum infection in infants in relation to exposure to sporozoite-infected anophelines. Am J Trop Med Hyg 59 : 243–251. [Google Scholar]
  9. Killeen GF, McKenzie FE, Foy BD, Schieffelin C, Billingsley PF, Beier JC, 2000. A simplified model for predicting malaria entomologic inoculation rates based on entomologic and parasitologic parameters relevant to control. Am J Trop Med Hyg 62 : 535–544. [Google Scholar]
  10. Keiser O, 2001. Einfluss von Morbidität auf Kinderwachstum in Papua Neu Guinea und Tansania. Diploma Thesis. Swiss Tropical Institute, Basel, Switzerland.
  11. Fontenille D, Lochouarn L, Diatta M, Sokhna C, Dia I, Diagne N, Lemasson JJ, Ba K, Tall A, Rogier C, Trape JF, 1997. Four years’ entomological study of the transmission of seasonal malaria in Senegal and the bionomics of Anopheles gambiae and A. arabiensis. Trans R Soc Trop Med Hyg 91 : 647–652. [Google Scholar]
  12. MARA Collaboration, 1998. Towards an Atlas of Malaria Risk in Africa. Durban, South Africa: MARA/ARMA.
  13. Contamin H, Fandeur T, Rogier C, Bonnefoy S, Konate L, Trape JF, Mercereau-Puijalon O, 1996. Different genetic characteristics of Plasmodium falciparum isolates collected during successive clinical malaria episodes in Senegalese children. Am J Trop Med Hyg 54 : 632–643. [Google Scholar]
  14. Lines J, Armstrong JRM, 1992. For a few parasites more: inoculum size, vector control and strain-specific immunity to malaria. Parasitol Today 8 : 381–382. [Google Scholar]
  15. Gupta S, Day KP, 1994. A theoretical framework for the immunoepidemiology of Plasmodium falciparum malaria. Parasite Immunol 16 : 361–370. [Google Scholar]
  16. Smith T, Charlwood JD, Kitua AY, Masanja H, Mwankusye S, Alonso PL, Tanner M, 1998. Relationships of malaria morbidity with exposure to Plasmodium falciparum in young children in a highly endemic area. Am J Trop Med Hyg 59 : 252–257. [Google Scholar]
  17. Druilhe P, Perignon JL, 1994. Mechanisms of defense against P. falciparum asexual blood stages in humans. Immunol Lett 41 : 115–120. [Google Scholar]
  18. Smith T, Felger I, Tanner M, Beck HP, 1999. Premunition in Plasmodium falciparum infection: insights from the epidemiology of multiple infections. Trans R Soc Trop Med Hyg 93 (Suppl 1): 59–64. [Google Scholar]
  19. Kitua AY, Smith T, Alonso PL, Masanja H, Urassa H, Menendez C, Kimario J, Tanner M, 1996. Plasmodium falciparum malaria in the first year of life in an area of intense and perennial transmission. Trop Med Int Health 1 : 475–484. [Google Scholar]
  20. Snow RW, Marsh K, 1995. Will reducing Plasmodium falciparum transmission alter malaria mortality among African children? Parasitol Today 11 : 188–190. [Google Scholar]
  21. Lengeler C, 1997. Focus on the effect of bednets on malaria morbidity and mortality. Parasitol Today 13 : 123–124. [Google Scholar]
  22. Snow RW, Armstrong JR, Forster D, Winstanley MT, Marsh VM, Newton CR, Waruiru C, Mwangi I, Winstanley PA, Marsh K, 1992. Childhood deaths in Africa: uses and limitations of verbal autopsies. Lancet 340 : 351–355. [Google Scholar]
  23. Todd JE, de Francisco A, O’Dempsey TJ, Greenwood BM, 1994. The limitations of verbal autopsy in a malaria-endemic region. Ann Trop Paediatr 14 : 31–36. [Google Scholar]
  24. Quigley MA, Armstrong S Jr, Snow RW, 1996. Algorithms for verbal autopsies: a validation study in Kenyan children. Bull World Health Organ 74 : 147–154. [Google Scholar]
  25. Mobley CC, Boerma JT, Titus S, Lohrke B, Shangula K, Black RE, 1996. Validation study of a verbal autopsy method for causes of childhood mortality in Namibia. J Trop Pediatr 42 : 365–369. [Google Scholar]
  26. Molineaux L, 1997. Nature’s experiment: what implications for malaria prevention? Lancet 349 : 1636–1637. [Google Scholar]
  27. Molineaux L, 1985. The impact of parasitic diseases and their control, with an emphasis on malaria and Africa. Vallin J., Lopez AD, eds. Health Policy, Social Policy and Mortality Prospects. Liege, Belgium: Ordina Editions, 13–44.
  28. Marsh K, Snow RW, 1999. Malaria transmission and morbidity. Parassitologia. 41 : 241–246. [Google Scholar]
  29. Bradley DJ, 1991. Morbidity and mortality at Pare-Taveta, Kenya and Tanzania, 1954–66: the effects of a period of malaria control. Feachem RG, Jamison DT, eds. Disease and Mortality in Sub-Saharan Africa. Washington, DC: The World Bank, 248–263.
  30. Giglioli G, 1972. Changes in the pattern of mortality following the eradication of hyperendemic malaria from a highly susceptible community. Bull. World Health Organ 46 : 181–202. [Google Scholar]
  31. Alonso PL, Lindsay SW, Armstrong JR, Conteh M, Hill AG, David PH, Fegan G, de Francisco A, Hall AJ, Shenton FC, 1991. The effect of insecticide-treated bed nets on mortality of Gambian children. Lancet 337 : 1499–1502. [Google Scholar]
  32. D’Alessandro U, Olaleye BO, McGuire W, Thomson MC, Langerock P, Bennett S, Greenwood BM, 1995. A comparison of the efficacy of insecticide-treated and untreated bed nets in preventing malaria in Gambian children. Trans R Soc Trop Med Hyg 89 : 596–598. [Google Scholar]
  33. Binka FN, Kubaje A, Adjuik M, Williams LA, Lengeler C, Maude GH, Armah GE, Kajihara B, Adiamah JH, Smith PG, 1996. Impact of permethrin impregnated bednets on child mortality in Kassena-Nankana district, Ghana: a randomized controlled trial. Trop Med Int Health 1 : 147–154. [Google Scholar]
  34. Nevill CG, Some ES, Mung’ala VO, Mutemi W, New L, Marsh K, Lengeler C, Snow RW, 1996. Insecticide-treated bednets reduce mortality and severe morbidity from malaria among children on the Kenyan coast. Trop Med Int Health 1 : 139–146. [Google Scholar]
  35. Habluetzel A, Diallo DA, Esposito F, Lamizana L, Pagnoni F, Lengeler C, Traore C, Cousens SN, 1997. Do insecticide-treated curtains reduce all-cause child mortality in Burkina Faso? Trop Med Int Health 2 : 855–862. [Google Scholar]
  36. Phillips-Howard P, Nahlen B, Kolczak MS, Hightower AW, ter Kuile F, Alaii JA, Gimnig JE, Arudo J, Vulule JM, Odhacha A, Kachur SP, Schoute E, Rosen DH, Sexton JD, Oloo AJ, Hawley WA, 2003. Efficacy of permethrin-treated bed nets in the prevention of mortality in young children in an area of high perennial malaria transmission in western Kenya. Am J Trop Med Hyg 68 (Suppl. 4): 23–29. [Google Scholar]
  37. Snow RW, Marsh K, 2002. The consequences of reducing transmission of Plasmodium falciparum in Africa. AdvParasitol 52 : 235–264. [Google Scholar]
  38. Binka FN, Hodgson A, Adjuik M, Smith T, 2002. Mortality in a seven-and-a-half-year follow-up of a trial of insecticide-treated mosquito nets in Ghana. Trans R Soc Trop Med Hyg 96 : 597–599. [Google Scholar]
  39. Molineaux L, Gramiccia G, 1980. The Garki Project. Geneva: World Health Organization.
  40. Guyatt HL, Snow RW, 2001. Malaria in pregnancy as an indirect cause of infant mortality in sub-Saharan Africa. Trans R Soc Trop Med Hyg 95 : 569–576. [Google Scholar]
  41. Goodman CA, Coleman PG, Mills A, 2000. Economic Analysis of Malaria Control in Sub-Saharan Africa. Geneva: Global Forum for Health Research; 2000.
  42. Spiegelhalter DJ, Thomas A, Best N, 2000. WinBUGS. (1.3). Cambridge, United Kingdom: Medical Research Council Biostatistics Unit.
http://instance.metastore.ingenta.com/content/journals/10.4269/ajtmh.2004.71.80
Loading
/content/journals/10.4269/ajtmh.2004.71.80
Loading

Data & Media loading...

  • Received : 21 Aug 2003
  • Accepted : 09 Jan 2004

Most Cited This Month

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error