Date Published: March 7, 2019
Publisher: Public Library of Science
Author(s): César Camilo Prado, Luis Antonio Alvarado-Cabrera, Paola Andrea Camargo-Ayala, Diego Garzón-Ospina, Milena Camargo, Sara Cecilia Soto-De León, Juan Ricardo Cubides, Carmen Teresa Celis-Giraldo, Manuel Elkin Patarroyo, Manuel Alfonso Patarroyo, David J. Sullivan.
In the past few years, relative frequencies of malaria parasite species in communities living in the Colombian Amazon riverside have changed, being Plasmodium vivax (61.4%) and Plasmodium malariae (43.8%) the most frequent. Given this epidemiological scenario, it is important to determine the species of anophelines involved in these parasites’ transmission. This study was carried out in June 2016 in two indigenous communities living close to the tributaries of the Amazon River using protected human bait. The results of this study showed a total abundance of 1,085 mosquitos, of which 99.2% corresponded to Anopheles darlingi. Additionally, only two anopheline species were found, showing low diversity in the study areas. Molecular confirmation of some individuals was then followed by evolutionary analysis by using the COI gene. Nested PCR was used for identifying the three Plasmodium species circulating in the study areas. Of the two species collected in this study, 21.0% of the An. darlingi mosquitoes were infected with P. malariae, 21.9% with P. vivax and 10.3% with Plasmodium falciparum. It exhibited exophilic and exophagic behavior in both study areas, having marked differences regarding its abundance in each community (Tipisca first sampling 49.4%, Tipisca second sampling 39.6% and Doce de Octubre 10.9%). Interestingly, An. mattogrossensis infected by P. vivax was found for the first time in Colombia (in 50% of the four females collected). Analysis of An. darlingi COI gene diversity indicated a single population maintaining a high gene flow between the study areas. The An. darlingi behavior pattern found in both communities represents a risk factor for the region’s inhabitants living/working near these sites. This highlights the need for vector control efforts such as the use of personal repellents and insecticides for use on cattle, which must be made available in order to reduce this Anopheline’s abundance.
Malaria is the parasitic disease with the greatest worldwide impact. Reports of cases increased by 2 million in 2017 with respect to the previous year, for a total of 219.000 million cases worldwide. In the Americas, case number increases have been reported in the past three years with respect to 2015, largely due to an increase in malaria transmission in Venezuela, Brazil and Nicaragua . Up to the year 2010, Plasmodium vivax had been reported as the most prevalent malaria parasite in Colombia . However, there has been an increase in P. falciparum and P. malariae prevalence since 2014 in some parts of the country . Four regions have been recognized as being the main focal points of malarial transmission in Colombia: the region between the lower Cauca, Sinú and Urabá river basins in the northeast, the Pacific coast in the west, part of the Orinoquía region in the east of the country and the Amazon region in the south . There has been an increase in cases in the latter region in the past four years [5–7]. Recent studies highlighted high P. malariae circulation along the banks of the Amazon and Loretoyacu rivers, in addition to P. vivax and P. falciparum [8,9].
The diversity of mosquitoes from the Anopheles genus in Colombia is mainly favored by a wide variety of habitats, providing environmental conditions for mosquito development, dispersion and persistence . Although some primary vectors are widely distributed throughout Colombia’s five regions, their biting patterns and ecology may vary; this means that such aspects must be studied to improve the efficiency of currently used control methods [29,36].