2 METHODS

2.1 Protocols

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) were followed in order to systematically review 30 cross-sectional studies. The whole methodological protocol of this study was registered on OSF with DOI 10.17605/OSF.IO/FJU94 and might be accessed by the link https://osf.io/fju94/.

2.2 Systematic search strategy

Four English Databases were used including Scopus , PubMed ,ScienceDirect and Web of Science , for literature searching of articles published prior to September 21st, 2020. All scientific publications related to genetic characterization ofT. gondii isolated from free-range chickens (Gallus gallus domesticus ) were sought.
The terms used in the searching process were “toxoplasmosis”, “Toxoplasma gondii ”, “T. gondii ”, “type”, “typing”, “genotype”, “genotyping”, “molecular characterization”, “chicken”, “fowl”, “pould” and “RFLP”. Only studies published in English were considered. All citations were imported to Mendeley (by Elsevier) and the studies were tabulated on Sheets (by GSuite – Google). Further studies were checked by scanning the reference list of the selected papers to prevent missing valuable data.

2.3 Study selection criteria

The papers were screened independently by three reviewers. The studies were selected as they corresponded to inclusion criteria, and those which did not contemplate the requirements were excluded. Duplicated articles and review works were excluded from the process. The main inclusion criteria was the presence of genotypes of T. gondiiisolated strictly from free-range chickens (Gallus gallus domesticus) in experimental works, which was observed in the titles and abstracts or full texts, if necessary.
Thus, articles about seroprevalence, diagnostic methods, or those which did not perform the genotyping of their isolates using RFLP-PCR and did not present a table showing their markers along the result of ToxoDB # genotype or clonal type, were excluded. Studies that used less than 5 markers were not included (Amouei et al., 2020).

2.4 Data extraction

Data from all of the selected articles were extracted independently according to PRISMA checklist standardized form developed for molecular studies by trained data extractors. Data contemplated general characteristics: first author, year of publication and country; and methodological characteristics: sample size, tissue location, host (only free-range chickens), examination techniques used to identify infected hosts (MAT, IFAT, ELISA, PCR, Nested-PCR, bioassays), number of DNA isolates, number of genotypes/types/clonal types, and ToxoDB # evidenced.