Abstract
Toxoplasma gondii (T. gondii) is a ubiquitous protozoan parasite with a complex life cycle involving various intermediate hosts, including dogs. Dogs can act as intermediate hosts for T. gondii, allowing the parasite to undergo asexual reproduction within their tissues. This can lead to the formation of tissue cysts containing bradyzoites, which can be transmitted to other hosts. Therefore, the infectious strains of T. gondii in dogs could reflect the primary genotypes infecting the environment, humans, and animals. This comprehensive research aims to assess the genetic diversity of T. gondii isolates collected from dogs worldwide. A thorough search of four academic databases (PubMed, Scopus, ScienceDirect, and Web of Science) and Google Scholar was conducted for literature published from January 1990 to March 2024. In the present study, a total of 26 papers met the criteria for inclusion. The results revealed that atypical genotypes were the most prevalent, accounting for 78.2 % of the total isolates (151 out of 193). Clonal Types III, II, and I were less frequent, with prevalence rates of 9.8 % (19 out of 193), 7.8 % (15 out of 193), and 3.1 % (6 out of 193), respectively. Type I clonal isolates have been documented in regions including Asia, Europe, and North America. Type II isolates have been identified in Africa, Europe, Oceania, and North America. Furthermore, Type III isolates, along with atypical genotypes, have been reported across Africa, Asia, North America, and South America. According to an analysis of 159 ToxoDB genotypes found in dogs worldwide, ToxoDB #2 (Type III) was the most prevalent genotype (18/159), followed by ToxoDB #1 or #3 (Type II) (15/159), ToxoDB #9 (15/159), and ToxoDB #20 (15/159). Overall, our study revealed low genetic diversity of T. gondii in dogs from Europe, Oceania, and Africa, with circulating clonal strains. Conversely, despite the higher number of isolates in Asia, North America, and South America, non-clonal parasites with extensive genetic diversity were prevalent.