following

Domestication has dramatically reduced T. gondii diversity. The few clonal lineages prevailing in the domestic environment today are those that are specifically adapted to domestic cats. Indeed, domestic cats infected by wild strains may not be shedding oocysts following their infection. In the wild, available ecological niches are much more abundant and diversified (mainly diversity of feline hosts), and this may explain the substantial diversity of strains in this environment.

Khan, A., Ajzenberg, D., Mercier, A., Demar, M., Simon, S., Dardé, M.L., Wang, Q., Verma, S.K., Rosenthal, B.M., Dubey, J.P., Sibley, L.D., 2014. Geographic separation of domestic and wild strains of Toxoplasma gondii in French Guiana correlates with a monomorphic version of chromosome1a. PLoS Negl Trop Dis 8, e3182. https://doi.org/10.1371/journal.pntd.0003182

Khan, A., Fux, B., Su, C., Dubey, J.P., Darde, M.L., Ajioka, J.W., Rosenthal, B.M., Sibley, L.D., 2007. Recent transcontinental sweep of Toxoplasma gondii driven by a single monomorphic chromosome. Proc. Natl. Acad. Sci. U.S.A. 104, 14872–14877. https://doi.org/10.1073/pnas.0702356104

Khan, A., Miller, N., Roos, D.S., Dubey, J.P., Ajzenberg, D., Dardé, M.L., Ajioka, J.W., Rosenthal, B., Sibley, L.D., 2011. A monomorphic haplotype of chromosome Ia is associated with widespread success in clonal and nonclonal populations of Toxoplasma gondii. MBio 2, e00228-00211. https://doi.org/10.1128/mBio.00228-11

Mercier, A., Ajzenberg, D., Devillard, S., Demar, M.P., de Thoisy, B., Bonnabau, H., Collinet, F., Boukhari, R., Blanchet, D., Simon, S., Carme, B., Dardé, M.-L., 2011. Human impact on genetic diversity of Toxoplasma gondii: example of the anthropized environment from French Guiana. Infect. Genet. Evol. 11, 1378–1387. https://doi.org/10.1016/j.meegid.2011.05.003

Rosenthal, B.M., 2009. How has agriculture influenced the geography and genetics of animal parasites? Trends Parasitol. 25, 67–70. https://doi.org/10.1016/j.pt.2008.10.004

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Another explanation could be the ability of T. gondii to be transmitted asexually only between intermediate hosts (mainly rodents) through vertical transmission, bypassing sexual reproduction in the final host (cat).

Worth, A.R., Lymbery, A.J., Thompson, R.C.A., 2013. Adaptive host manipulation by Toxoplasma gondii: fact or fiction? Trends Parasitol. 29, 150–155. https://doi.org/10.1016/j.pt.2013.01.004

Toxoplasma gondii is one of the most widespread zoonotic pathogens known today. Whereas only a few genotypes of T. gondii dominate in the Northern Hemisphere, many genotypes coexist in South America. Furthermore, T. gondii strains from South America are more likely to be virulent than those from the Northern Hemisphere. However, it is not clear what factor(s) shaped modern-day genetic diversity and virulence of T. gondii.

1. Here, they analysis suggests that the rise and expansion of farming in the past 11,000 years established the domestic cat/mouse transmission cycle for T. gondii, which has undoubtedly played a significant role in the selection of certain linages of T. gondii (Shwab et al., 2018)

2. They mathematical simulations showed that within the domestic transmission cycle, intermediately mouse-virulent T. gondii genotypes have an adaptive advantage and eventually become dominant due to a balance between lower host mortality and the ability to superinfect mice previously infected with a less virulent T. gondii strain (Shwab et al., 2018)

3. They analysis of the global type II lineage of T. gondii suggests its Old World origin but recent expansion in North America, which is likely the consequence of global human migration and trading. These results have significant implications concerning transmission and evolution of zoonotic pathogens in the rapidly expanding anthropized environment demanded by rapid growth of the human population and intensive international trading at present and in the future (Shwab et al., 2018).

Actually, Toxoplasma gondii can clonal in nature, and wild and domestic animals can infected T. gondii even more times. However, at another angle, asexual Toxoplasma gondii strain can keep a better opportunity to reproduce sexually.

Shwab, E.K., Saraf, P., Zhu, X.Q., Zhou, D.H., Mcferrin, B.M., Ajzenberg, D., Schares, G., Hammondaryee, K., Helden, P.V., Higgins, S.A., 2018. Human impact on the diversity and virulence of the ubiquitous zoonotic parasiteToxoplasma gondii. Proceedings of the National Academy of Sciences of the United States of America 115, E6956-E6963.

Here is a recent review addressing this topic

https://www.sciencedirect.com/science/article/pii/S2405676618300489

Well Lokman, I was surprised to learn that Toxo might be transmitted horizontally between IHs through sexual intercourses... Article Protozoan Parasite Toxoplasma gondii Manipulates Mate Choice...

You're right Valentin :) , we can also add a role of predation/scavenging/cannibalism (cannibalism being common in rodents) in the asexual transmission of T. gondii