title: Molecular and epidemiological characterization of Plasmodium vivax recurrent infections in southern Mexico.
abstract: BACKGROUND
  In southern Mexico, malaria transmission is low, seasonal, and persistent. Because many patients are affected by two or more malaria episodes caused by Plasmodium vivax, we carried out a study to determine the timing, frequency, and genetic identity of recurrent malaria episodes in the region between 1998 and 2008.
  
  
  METHODS
  Symptomatic patients with more than one P. vivax infection were followed up, and blood samples were collected from primary and recurrent infections. DNA extracted from infected blood samples was analyzed for restriction fragment length polymorphism (RFLP) in genes encoding csp and msp3α, as well as size variation in seven microsatellites.
  
  
  RESULTS
  One hundred and forty six parasite samples were collected from 70 patients; of these, 65 patients had one recurrent infection, four had two, and one had three recurrent infections. The majority of recurrent infections occurred within one year of the primary infection, some of which were genetically homologous to the primary infection. As the genetic diversity in the background population was high, the probability of homologous re-infection was low and the homologous recurrences likely reflected relapses. These homologous recurrent infections generally had short (< 6 months) or long (6-12 months) intervals between the primary (PI) and recurrent (RI) infections; whereas infections containing heterologous genotypes had relatively longer intervals. The epidemiological data indicate that heterologous recurrences could be either relapse or re-infections.
  
  
  CONCLUSIONS
  Genetic and temporal analysis of P. vivax recurrence patterns in southern Mexico indicated that relapses play an important role in initiating malaria transmission each season. The manifestation of these infections during the active transmission season allowed the propagation of diverse hypnozoite genotypes. Both short- and long-interval relapses have contributed to parasite persistence and must be considered as targets of treatment for malaria elimination programs in the region to be successful.
authors.affiliation: CRISP, National Institute for Public Health, Tapachula, Chiapas 30700, Mexico. lgonzal@insp.mx
authors.forename: Lilia
authors.initials: L
authors.lastname: Gonzalez-Ceron
authors.forename: Jianbing
authors.initials: J
authors.lastname: Mu
authors.forename: Frida
authors.initials: F
authors.lastname: Santillán
authors.forename: Deirdre
authors.initials: D
authors.lastname: Joy
authors.forename: Marco A
authors.initials: MA
authors.lastname: Sandoval
authors.forename: Gerardo
authors.initials: G
authors.lastname: Camas
authors.forename: Xinzhuan
authors.initials: X
authors.lastname: Su
authors.forename: Elena V
authors.initials: EV
authors.lastname: Choy
authors.forename: Rene
authors.initials: R
authors.lastname: Torreblanca
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001769:Blood / Q000469:parasitology; D002648:Child; D016172:DNA Fingerprinting; D016054:DNA, Protozoan / Q000235:genetics / Q000302:isolation & purification; D005260:Female; D005838:Genotype; D006801:Humans; D016780:Malaria, Vivax / Q000453:epidemiology* / Q000469:parasitology*; D008297:Male; D008800:Mexico / Q000453:epidemiology; D018895:Microsatellite Repeats; D008875:Middle Aged; D017720:Molecular Epidemiology; D010966:Plasmodium vivax / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D012150:Polymorphism, Restriction Fragment Length; D012008:Recurrence; D055815:Young Adult
chemical_list: D016054:DNA, Protozoan