The vector
The aggravating factor contributing to a rise in malaria prevalence around Iquitos, apart from road construction, deforestation and human migration, includes the introduction of a new and more efficient mosquito vector.
 
The most important vector transmitting malaria in Amazon regions of South America is Anopheles darlingi. Between 1988 and 1991, however, mosquito collections were made at three separate locations near Iquitos and of 35,000 mosquitoes collected, representing 13 genera and 25 species, A. darlingi was absent.
 
Larvae of this invasive species are thought to have been introduced to the Iquitos region in the 1990’s by boats transporting tropical fish for the aquaculture industry, and the increased spread of malaria, particularly P. falciparum, in the Peruvian Amazon has been attributed to its introduction.
Anopheles darlingi
 
Image from http://fmel.ifas.ufl.edu/gallery.htm
A. darlingi is considered to be an efficient vector because it is highly anthropophilic, readily enters homes to feed, has a wide range of feeding times, and is susceptible to both P. vivax and P. falciparum.
 
Since its introduction in the Departmento of Loreto A. darlingi has continued to invade previously uninfested areas. It is now the most abundant mosquito species during the wettest parts of the year, making up nearly 90% of the mosquito population, and still remains a major anopheline species through the dry season as well.  A. darlingi has a heterogenous distribution, so while it is not the most abundant species at all sites within Loreto, it has been found to be the most widespread. A. darlingi breeds in partially shaded, unpolluted, relatively still waters. Suitable breeding sites include shallow pools left after floods recede, pits after road construction, fish farms, edges of small rivers, swamps, and small pools on cleared land. The diversity of suitable habitat also vboosts the species’ ability to colonize an area even in the absence of deforestation.
Abandoned ponds: A. darlingi breeding site par excellence!