title: Human helminth co-infection: no evidence of common genetic control of hookworm and Schistosoma mansoni infection intensity in a Brazilian community.
abstract: Strong statistical associations between soil-transmitted helminths and schistosomes are frequently observed in co-endemic human populations, although the underlying explanations remain poorly understood. This study investigates the contribution of host genetics and domestic environment to hookworm and Schistosoma mansoni infection intensity and evaluates the role of genetic and non-genetic factors in co-variation of infection intensity. Detailed genealogical information allowed assignment of 1303 individuals living in the Brazilian community of Americaninhas, Minas Gerais state, to 25 pedigrees (containing between two and 1159 members) residing in 303 households. The prevalence of co-infection with both hookworms and schistosomes was high (38.5%), with significant correlation between Necator americanus and S. mansoni faecal egg counts. Bivariate variance component analysis demonstrated a modest but significant species-specific heritability for intensity of N. americanus (h(2)=0.196) and S. mansoni infection (h(2)=0.230). However, after accounting for demographic, socio-economic and household risk factors, no evidence for common genetic control of intensity of hookworm and schistosome infection was observed. There was some evidence for residual clustering within households but the majority (63%) of the covariance between N. americanus and S. mansoni infection intensity remained specific to the individual and could not be explained by shared genes, shared environment or other shared demographic, socio-economic or environmental risk factors. Our results emphasize the importance of exposure to hookworm and schistosome infection in driving the association between levels of infection with these species in hosts resident in areas of high transmission and suggest that much of this common exposure occurs outside the home.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK. rachel.pullan@lshtm.ac.uk
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Pullan
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Bethony
authors.forename: Stefan M
authors.initials: SM
authors.lastname: Geiger
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Correa-Oliveira
authors.forename: Simon
authors.initials: S
authors.lastname: Brooker
authors.forename: Rupert J
authors.initials: RJ
authors.lastname: Quinnell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D019353:Endemic Diseases; D005243:Feces / Q000469:parasitology; D005260:Female; D006725:Hookworm Infections / Q000453:epidemiology* / Q000469:parasitology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D017221:Necator americanus / Q000302:isolation & purification; D010270:Parasite Egg Count; D012550:Schistosoma mansoni / Q000302:isolation & purification; D012555:Schistosomiasis mansoni / Q000453:epidemiology* / Q000469:parasitology; D055815:Young Adult
references.citation: Soc Sci Med. 1988;26(2):209-13
references.pmid: 3347848
references.citation: Trop Med Int Health. 2003 Nov;8(11):975-86
references.pmid: 14629763
references.citation: Am J Trop Med Hyg. 1998 Sep;59(3):370-5
references.pmid: 9749627
references.citation: PLoS Negl Trop Dis. 2008;2(12):e352
references.pmid: 19104658
references.citation: Lancet. 2009 Jan 17;373(9659):234-9
references.pmid: 19150704
references.citation: J Exp Med. 1995 Feb 1;181(2):769-74
references.pmid: 7836929
references.citation: Trop Med Int Health. 1998 Nov;3(11):904-12
references.pmid: 9855404
references.citation: Proc Natl Acad Sci U S A. 2002 Apr 16;99(8):5533-8
references.pmid: 11960011
references.citation: Vet Parasitol. 2004 Jan 5;119(1):51-8
references.pmid: 15036576
references.citation: East Afr Med J. 2000 Mar;77(3):157-61
references.pmid: 12858892
references.citation: Soc Sci Med. 1998 Mar;46(6):755-65
references.pmid: 9522434
references.citation: Parasitology. 2002;125 Suppl:S51-9
references.pmid: 12622328
references.citation: Acta Trop. 2008 Nov-Dec;108(2-3):166-74
references.pmid: 18207118
references.citation: Hum Hered. 2006;61(4):222-8
references.pmid: 16877869
references.citation: Int J Appl Earth Obs Geoinf. 2004 Nov;6(1):33-46
references.pmid: 22545030
references.citation: Am J Hum Genet. 1998 May;62(5):1198-211
references.pmid: 9545414
references.citation: Am J Trop Med Hyg. 2002 Oct;67(4):336-43
references.pmid: 12452486
references.citation: Ann N Y Acad Sci. 2008;1136:38-44
references.pmid: 17954674
references.citation: Parasitol Int. 1999 Mar;48(1):73-9
references.pmid: 11269328
references.citation: Am J Trop Med Hyg. 1996 Sep;55(3):338-43
references.pmid: 8842126
references.citation: Am J Trop Med Hyg. 1999 Jun;60(6):921-6
references.pmid: 10403321
references.citation: Am J Trop Med Hyg. 2005 Dec;73(6):1145-50
references.pmid: 16354828
references.citation: Trop Med Int Health. 2005 Jan;10(1):42-57
references.pmid: 15655013
references.citation: Am J Med Genet. 1983 Mar;14(3):513-24
references.pmid: 6859102
references.citation: Heredity (Edinb). 2009 Apr;102(4):357-64
references.pmid: 19142203
references.citation: Nat Genet. 1996 Oct;14(2):181-4
references.pmid: 8841190
references.citation: Trends Parasitol. 2006 Aug;22(8):359-62
references.pmid: 16797235
references.citation: Clin Rev Allergy Immunol. 2004 Apr;26(2):85-92
references.pmid: 15146105
references.citation: Ann Hum Genet. 1982 Oct;46(4):373-83
references.pmid: 6961886
references.citation: Int J Parasitol. 2004 Apr;34(5):595-601
references.pmid: 15064124
references.citation: Behav Genet. 1988 May;18(3):329-38
references.pmid: 3219111
references.citation: Hum Mol Genet. 2004 Oct 1;13 Spec No 2:R187-94
references.pmid: 15358724
references.citation: Trop Med Int Health. 2007 Jun;12(6):709-23
references.pmid: 17550468
references.citation: Int J Parasitol. 2006 Sep;36(10-11):1143-51
references.pmid: 16814294
references.citation: Genet Epidemiol. 2002 Mar;22(3):254-64
references.pmid: 11921085
references.citation: Am J Trop Med Hyg. 2004 Apr;70(4):443-8
references.pmid: 15100462
references.citation: Acta Trop. 2008 Nov-Dec;108(2-3):118-23
references.pmid: 18582842
references.citation: Trop Med Int Health. 2004 Mar;9(3):381-9
references.pmid: 14996368
references.citation: Am J Trop Med Hyg. 2007 Dec;77(6 Suppl):88-98
references.pmid: 18165479
references.citation: FEMS Immunol Med Microbiol. 2005 Feb 1;43(2):115-24
references.pmid: 15681140
references.citation: Mol Ecol. 2001 Jun;10(6):1433-7
references.pmid: 11412366
references.citation: Hum Hered. 2003;55(1):46-50
references.pmid: 12890925
references.citation: J Infect Dis. 2008 Apr 15;197(8):1198-203
references.pmid: 18462166
references.citation: Trans R Soc Trop Med Hyg. 1985;79(6):812-25
references.pmid: 3832493
references.citation: Parasitology. 2008 Oct;135(12):1407-15
references.pmid: 18937884
references.citation: Trans R Soc Trop Med Hyg. 2007 Feb;101(2):146-54
references.pmid: 17027054
references.citation: Nat Rev Immunol. 2002 Jul;2(7):499-511
references.pmid: 12094224
references.citation: Parasitol Today. 1998 Jan;14(1):23-6
references.pmid: 17040685
references.citation: Parasitology. 1987 Dec;95 ( Pt 3):623-35
references.pmid: 3320892
references.citation: Trop Med Int Health. 2001 Feb;6(2):136-45
references.pmid: 11251910
references.citation: Trop Med Int Health. 2006 Jan;11(1):56-64
references.pmid: 16398756
references.citation: J Infect Dis. 1999 Nov;180(5):1665-73
references.pmid: 10515830
references.citation: Am J Trop Med Hyg. 2004 Jan;70(1):57-62
references.pmid: 14971699
references.citation: Arterioscler Thromb Vasc Biol. 1999 Oct;19(10):2456-64
references.pmid: 10521376
references.citation: Int J Parasitol. 2003 Sep 30;33(11):1219-31
references.pmid: 13678637
references.citation: Hum Biol. 1997 Apr;69(2):201-8
references.pmid: 9057344
references.citation: Ann Trop Med Parasitol. 2006 Oct;100(7):551-70
references.pmid: 16989681
references.citation: Parasitology. 1998 Jan;116 ( Pt 1):85-93
references.pmid: 9481778
references.citation: Int J Parasitol. 2006 Jan;36(1):71-7
references.pmid: 16321389
references.citation: J Infect Dis. 2010 Sep 15;202(6):954-61
references.pmid: 20681887
references.citation: Int J Parasitol. 2007 Aug;37(10):1153-61
references.pmid: 17407778