Malaria in the Peruvian Amazon - Background of the Project

The Iquitos region constitutes a heterogeneous ecological and social matrix, encompassing rural, urban, and peri-urban communities. The entire region experienced a malaria epidemic in the 1990's, particularly along the Iquitos-Nauta road (Branch et al., 2005). Local health authorities have declared malaria to be endemic in the region since 1999, when the epidemic was controlled (Roshanravan et al., 2003). However, the social and landscape dynamics underlying the malaria epidemic and its transition to endemism are not well understood (Vinetz and Gilman, 2002).

The construction of the Iquitos-Nauta road began in the 1970s, connecting the two largest urban centers in the region, enabled both high rates of deforestation and the massive migration of the rural poor. The landscape surrounding the road then changed from rural to peri-urban, with the construction of weekend houses by urban migrants, and permanent homes by rural settlers.

Housing, agricultural plots, ponds, and isolated forest fragments are all part of the peri-urban landscape. The effect of these changes on the distribution, dispersal, and reproduction of malaria mosquito vectors remains largely unexplored. We will identify the mechanisms behind the spread of malaria centered in peri-urban communities by complementing data on malaria vectors currently available at Universidad Nacional de la Amazonia Peruana (UNAP)(Chalco, 1998; Fachin and Fernandez, 2002; Pinedo, 2002) with our social and landscape data.

The Peri-Urban area

The peri-urban communities are characterized by socioeconomic inequality: while there are a few wealthy visitors, the majority of permanent settlers are among the poorest in the region (Pyhala, 2004). The risk of malaria infection is not evenly distributed among these groups: our survey of fifty permanent residents uncovered a minimum of four malaria infections each, compared to none among weekend visitors during the same period. Peri-urban residents are highly mobile. Men work temporarily in the cities and spend part of the year fishing, cutting timber, and farming in rural areas, while women work as domestic helpers in the urban centers. In addition, most peri-urban residents belong to multi-sited households that maintain strong links to rural life (Pinedo-Vasquez and Padoch, in press; WinklerPrins, 2002).

The Fish Ponds

Accessibility and proximity to Iquitos and Nauta have attracted several nongovernmental organizations (NGOs) to the peri-urban settlements along the road. Aiming to reduce poverty and control deforestation and environmental degradation (Roshanravan et al., 2003), some of these NGOs, backed by international donors, began promoting fish farming in ponds beginning in the 1990s (Pyhala, 2004; Alcántara et al. 2001). On average, 200 hectares of ponds were built each year from 1992 to 1999, increasing the pond surface along the road almost fivefold (Salas and Sanchez, 2000). These development programs coincide with an explosion of malaria: from 1992 to 1997 malaria incidence increased 50-fold in the Iquitos region, in contrast with a national 4-fold increase for Peru (Guthmann et al. 2002). The severity of the disease also increased during this period: the proportion of malaria cases caused by Plasmodium falciparum rose from 1.6% to 28.3%, and Iquitos reported 87% of all malaria-related deaths in Peru (Aramburú et al. 1999).

Drastic changes in the productivity of the region also accompanied the pond construction boom. Given the cost of maintaining a working fish pond (~$350/month), most peri-urban residents could not operate the ponds without NGO subsidies, and the ponds were eventually sold to urban visitors. These ponds are not economically productive: they are used as swimming pools and for other weekend recreational activities. Our preliminary survey indicates that families from Iquitos currently own ca. 90% of NGO-built fish ponds. For peri-urban residents the boom in pond construction has thus produced only one income opportunity: to work as property keepers for the pond owners. The burden of disease and the labor relationships arising from the NGO-promoted pond construction seem to have increased, not alleviated, poverty in the region. Data analysis from our preliminary survey shows a significantly greater risk of malaria infection among households with lower socioeconomic status (p-value<0.01).

Background

Background - Malaria in Iquitos

The Peri-Urban area

The Fish Ponds