Abstract
Toxoplasma gondii was initially classified in three main lineages
related to its virulence: Types I, II and III. The recombination of
genes during sexual cycle in felids gut led to more than 200 genotypes,
found in ToxoDB database, using 11 RFLP markers. Free-range chickens are
good bioindicators of soil contamination with T. gondii oocysts.
In this sense, there are systematic reviews regarding data of genetic
characterization of this parasite in felines and ruminants, but not in
chickens heretofore, what makes this work necessary. A systematic review
in the literature was performed with papers published prior to September
21st, 2020. The main inclusion criteria was the presence of T.
gondii genotypes, isolated strictly from free-range chickens, in
experimental works. Initially, a total of 1,343 studies related to the
terms were identified on databases and 30 studies were selected to be
systematically reviewed. A total of 561 isolates of T. gondii from 6,356
free-range chickens were analyzed for genotyping, revealing 190
genotypes. ToxoDB #59 and #2 were the most frequent in America, #1
was the most frequent in Africa and 3 atypical isolates from genotype
ToxoDB #9 were found in Asia. There is not data from Europe and
Oceania. The majority of studies were Brazilian (16/30). A total of 68
RFLP genotypes were recognized among the 561 isolates’ DNAs analyzed
from the 30 studies. Some studies show new genotypes never described
before, which reinforces the idea that some years from now, even more
new genotypes will be isolated, due to progressive genetic
recombination. The large amount of undefined genotypes makes it
necessary to perform Nested PCR technique when genotyping. Moreover, the
lack of data in Continents such as Europe, Asia and Oceania makes it
necessary to perform new isolating and genotyping studies in these
places.