Genetic diversity and population structure of Plasmodium falciparum in the Philippines

Abstract

Background: In the Philippines, malaria morbidity and mortality have decreased since the 1990s by effective malaria control. Several epidemiological surveys have been performed in the country, but the characteristics of the Plasmodium falciparum populations are not yet fully understood. In this study, the genetic structure of P. falciparum populations in the Philippines was examined.

New Insights into Clonality and Panmixia in Plasmodium and Toxoplasma

“…In some populations, restrained recombination manifests itself, not only by LD and ubiquitous MLGs but also by a tendency of natural populations to be structured into lasting, stable clusters, which cannot be accounted for by isolation by distance and time. This has been observed in P. falciparum (Branch et al, 2011;Griffing et al, 2011) and P. vivax (Gupta et al, 2012;Iwagami et al, 2009;Orjuela-Sánchez et al, 2010;Rezende et al, 2010). However, Plasmodium clusters cannot be equated to near-clades similar to the ones observed in T. cruzi and Leishmania (Tibayrenc and Ayala, 2013), because their stability is limited in time and is blurred by genetic recombination from 1 year to another.…”

“…However, (i) it is the very and only statistic appropriate for testing rarity or absence of recombination, on which the definition of PCE is based; (ii) when enough loci are surveyed, its power of resolution is high (Tibayrenc and Ayala, 2012;Tibayrenc et al, 1990); and (iii) it is widely used as a circumstantial evidence for clonality by many authors working on Plasmodium (Anderson et al, 2000;Arnott et al, 2012;Branch et al, 2011;Chenet et al, 2012;Conway, 2007;Ferreira et al, 2007;Imwong et al, 2007;Iwagami et al, 2009Iwagami et al, , 2012Karunaweera et al, 2008;Mu et al, 2005;Nkhoma et al, 2013;Orjuela-Sánchez et al, 2010;Rezende et al, 2010;Volkman et al, 2007Volkman et al, , 2012a and Toxoplasma (Khan et al, 2011;Lehman et al, 2004;Rajendran et al, 2012;Su et al, 2006), as well as on other pathogens (Tibayrenc and Ayala, 2012). As asserted here, only the LD approach has been able to refute the panmictic prejudice in Plasmodium and Toxoplasma (Tibayrenc et al, 1990(Tibayrenc et al, , 1991.…”

“…We will call it here the "starving sex hypothesis". It has been accepted by many authors in order to account for the observed population structure of Plasmodium (Arnott et al, 2012;Branch et al, 2011;Chenet et al, 2012;Conway, 2007;Ferreira et al, 2007;Gupta et al, 2012;Imwong et al, 2006Imwong et al, , 2007Iwagami et al, 2009;Mobegi et al, 2012;Mu et al, 2005;Mzilahowa et al, 2007;Neafsey, 2013;Neafsey et al, 2008;Nkhoma et al, 2013;Schultz et al, 2010;Volkman et al, 2012a,b). It can be challenged, as we will further see, since many observations are at odds with it, both in P. falciparum and in Plasmodium vivax.…”

“…Many studies have ascertained evidence for clonality and restrained recombination, based on the analysis of LD in many populations of P. falciparum (Annan et al, 2007;Branch et al, 2011;Chenet et al, 2012;Griffing et al, 2011;Iwagami et al, 2009;Manske et al, 2012;Nkhoma et al, 2013;Razakandrainibe et al, 2005;Volkman et al, 2007Volkman et al, , 2012a and P. vivax (Chenet et al, 2012;Imwong et al, 2007;Iwagami et al, 2012;Karunaweera et al, 2008;Rezende et al, 2010). Consequently, the panmictic model was considered to be "oversimplified" in Plasmodium (Heitman, 2006).…”

Evolution of Plasmodium falciparum drug resistance: implications for the development and containment of artemisinin resistance

“…In this region, the transmission intensity of malaria is much lower than that in highly endemic regions in Africa. The parasite population is small in size and well structured, as compared to that African endemic regions (99,100). Drugresistant parasites are more readily selected under such ecological and population genetic conditions (101)(102)(103).…”