Inland valley rice production systems and malaria infection and disease in the savannah of Côte d'Ivoire

Abstract

SummaryIn sub-Saharan Africa, lowlands developed for rice cultivation favour the development of Anopheles gambiae s. l. populations. However, the epidemiological impact is not clearly determined. The importance of malaria was compared in terms of prevalence and parasite density of infections as well as in terms of disease incidence between three agroecosystems: (i) uncultivated lowlands, ÔR0Õ, (ii) lowlands with one annual rice cultivation in the rainy season, ÔR1Õ and (iii) developed lowlands with two annual rice cultivation cycles, ÔR2Õ. We clinically monitored 2000 people of all age groups, selected randomly in each agroecosystem, for 40 days (in eight periods of five consecutive days scheduled every 6 weeks for 1 year). During each survey, a systematic blood sample was taken from every sick and asymptomatic person. The three agroecosystems presented a high endemic situation with a malaria transmission rate of 139-158 infective bites per person per year. The age-standardized annual malaria incidence reached 0.9 malaria episodes per person in R0, 0.6 in R1 and 0.8 in R2. Children from 0 to 9-year-old in R0 and R2 had two malarial attacks annually, but this was less in R1 (1.4 malaria episodes per child per year). Malaria incidence varied with season and agroecosystem. In parallel with transmission, a high malaria risk occurs temporarily at the beginning of the dry season in R2, but not in R0 and R1. Development of areas for rice cultivation does not modify the annual incidence of malarial attacks despite their seasonal influence on malaria risk. However, the lower malaria morbidity rate in R1 could be explained by socio-economic and cultural factors.

Occupational Activities Associated with a Reported History of Malaria among Women Working in Small-Scale Agriculture in South Africa

“…27 Associations between agricultural activities such as land clearing and production of crops such as cotton and sugar cane and having malaria have been reported. [11][12][13][14][15] Sugar cane and cotton cultivation have been associated with having malaria.…”

“…11 Cultivation of crops that require considerable irrigation, such as rice, cotton, maize, and sugar cane, have been associated with an increased risk for developing malaria. [12][13][14][15] Studies in central Côte d'Ivoire reported an association between an interruption in irrigated-rice cultivation and changes in malaria transmission, decreases in Plasmodium prevalence, and the number of malaria cases. 16,17 With the goal of increasing agricultural production in several developing countries, arid land has been reclaimed and artificial irrigation schemes have been created.…”

Impact of dams and irrigation schemes in Anopheline (Diptera: Culicidae) bionomics and malaria epidemiology

“…This phenomenon can be explained due to the better economic and social conditions of the communities living near the irrigation schemes, where more reliable health structures, better housing conditions and more resources to be spent in vector control and efficient treatments and preventive measures exist. This was verified in stable transmission areas of paddy fields in the Ivory Coast 40 , Cameroon 4 , and in northern Tanzania 45 . In the last example, although An.…”

“…Brazil, China, Colombia, India, Peru and Congo are the countries with the greatest hydroelectric potential unexploited, with the Amazon, Congo and Mekong basins being the ones that can be exploited best for this purpose 42 . 40,000 large dams and other 800,000 man-made lakes of smaller size were estimated to have been built by 2001 49 .…”

Therapy of Falciparum Malaria in Sub-Saharan Africa: from Molecule to Policy

“…In most settings of endemic infection, adults have developed a functional immune response to infection, and the incidence of measured elevated body temperatures associated with significant increases in parasite density is low compared to that in pediatric populations (57,93,113,121). Nevertheless, the term "fever" is often used by adults to describe clinical conditions subsequently managed as malaria.…”