title: Complexities and Perplexities: A Critical Appraisal of the Evidence for Soil-Transmitted Helminth Infection-Related Morbidity.
abstract: Soil-transmitted helminths (STH) have acute and chronic manifestations, and can result in lifetime morbidity. Disease burden is difficult to quantify, yet quantitative evidence is required to justify large-scale deworming programmes. A recent Cochrane systematic review, which influences Global Burden of Disease (GBD) estimates for STH, has again called into question the evidence for deworming benefit on morbidity due to STH. In this narrative review, we investigate in detail what the shortfalls in evidence are.
  
  
  
  We systematically reviewed recent literature that used direct measures to investigate morbidity from STH and we critically appraised systematic reviews, particularly the most recent Cochrane systematic review investigating deworming impact on morbidity. We included six systematic reviews and meta-analyses, 36 literature reviews, 44 experimental or observational studies, and five case series. We highlight where evidence is insufficient and where research needs to be directed to strengthen morbidity evidence, ideally to prove benefits of deworming.
  
  
  
  Overall, the Cochrane systematic review and recent studies indicate major shortfalls in evidence for direct morbidity. However, it is questionable whether the systematic review methodology should be applied to STH due to heterogeneity of the prevalence of different species in each setting. Urgent investment in studies powered to detect direct morbidity effects due to STH is required.
authors.affiliation: Research School of Population Health, College of Medicine, Biology, and Environment, The Australian National University, Canberra, Australian Captial Territory, Australia.
authors.forename: Suzy J
authors.identifier: 0000-0001-5540-1360
authors.initials: SJ
authors.lastname: Campbell
authors.affiliation: Research School of Population Health, College of Medicine, Biology, and Environment, The Australian National University, Canberra, Australian Captial Territory, Australia.
authors.forename: Susana V
authors.initials: SV
authors.lastname: Nery
authors.affiliation: Research School of Population Health, College of Medicine, Biology, and Environment, The Australian National University, Canberra, Australian Captial Territory, Australia.
authors.forename: Suhail A
authors.initials: SA
authors.lastname: Doi
authors.affiliation: Research School of Population Health, College of Medicine, Biology, and Environment, The Australian National University, Canberra, Australian Captial Territory, Australia.|Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Gray
authors.affiliation: Children's Health and Environment Program, Queensland Children's Medical Research Institute, The University of Queensland, Brisbane, Queensland, Australia.|School of Veterinary Science, The University of Queensland, Gatton, Queensland, Australia.
authors.forename: Ricardo J
authors.initials: RJ
authors.lastname: Soares Magalhães
authors.affiliation: School of Population Health, University of Queensland, Brisbane, Queensland, Australia.|Clinical Tropical Medicine Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: James S
authors.initials: JS
authors.lastname: McCarthy
authors.affiliation: Faculty of Veterinary and Agricultural Science, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Traub
authors.affiliation: Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.
authors.forename: Ross M
authors.initials: RM
authors.lastname: Andrews
authors.affiliation: Research School of Population Health, College of Medicine, Biology, and Environment, The Australian National University, Canberra, Australian Captial Territory, Australia.
authors.forename: Archie C A
authors.initials: AC
authors.lastname: Clements
mesh_terms: D000740:Anemia / Q000209:etiology; D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D001196:Ascariasis / Q000453:epidemiology / Q000469:parasitology / Q000517:prevention & control / Q000635:transmission*; D017164:Ascaris lumbricoides / Q000302:isolation & purification; D002908:Chronic Disease / Q000453:epidemiology / Q000517:prevention & control; D017281:Cost of Illness; D006373:Helminthiasis / Q000453:epidemiology* / Q000469:parasitology / Q000517:prevention & control / Q000635:transmission*; D006801:Humans; D015995:Prevalence; D012987:Soil / Q000469:parasitology*
chemical_list: D000871:Anthelmintics; D012987:Soil