An extensive multidisciplinary study developed by scientists from the University of Valencia and the University of Limpopo (South Africa) has led to the deduction that F. gigantica originated in South-East Africa by speciation resulting from the phenomenon of capture from hippopotamuses to archaic bovids during the Miocene, about 13.5 million years ago. For its part, F. hepatica originated in the Near East also due to the phenomenon of capture from hippopotamuses to ovicaprines at the end of the Miocene or beginning of the Pliocene, between 6 and 4 million years ago, in the region that later constituted the so-called “Fertile Crescent”, where the first steps of domestication took place and with it the beginning of the Neolithic Period.

This disease is a vector-borne zoonosis by small amphibian freshwater snails and causes innumerable economic losses in livestock. Its important impact on public health is due to its great pathogenicity, with post-treatment sequelae, extreme neurological and ocular effects, including irreversible blindness, and facilitating immunosuppression of coinfections leading to high morbidity and even death. It gives rise to situations of marked underdevelopment in the affected rural communities. It is the only human trematodiasis with worldwide distribution and shows great heterogeneity in transmission patterns and epidemiological situations, which make it difficult to define preventive measures and effective control initiatives.

Santiago Mas-Coma, professor emeritus of the Department of Pharmacy and Pharmaceutical Technology of the UV, points out that the numerous genetic studies aimed at clarifying the evolution of this disease in the different regions of the world “demonstrate the existence of a founder effect and suggest a dissemination of human and animal fascioliasis from one or a few centres of origin. Hence the transcendental importance of being able to establish the origin of the two causal agents and understand the strategies used by these parasites to have been able to expand worldwide”.

To date, the origin of fasciolas was based on mere hypotheses, due to the difficulties in unravelling what happened in the remote past. But, unexpectedly, the opportunity to molecularly characterise hippopotamus-specific flukes in South Africa and their genetic analysis compared with F. hepatica and F. gigantica from around the world, as well as other flukes from Asian elephants and North American cervids, has provided the proper evolutionary basis and molecular clock to unravel this multidisciplinary gibberish. Adela Valero, professor of the same Department of Pharmacy at the UV highlights: “sometimes the answer is found where it is least expected. It had never occurred to anyone that the key was found in hippos”.

María Dolores Bargues, also a professor in the same Department of Pharmacy at the UV, ends by referring to the fact that “these discoveries offer the starting point to be able to reconstruct the global expansion of this disease and establish what strategies these two parasites use to be able to spread to cover almost the entire world, including very extreme areas of human endemicity both at high altitudes such as the Bolivian highlands at 3800-4100 m, as well as in the Nile Delta at sea level in Egypt, and from southern Patagonia to the Sahara desert and almost all Asia and Oceania”.

Article:

Bargues M. D., Halajian A., Artigas P., Luus-Powell W. J., Valero M. A. & Mas-Coma S., 2022. «Paleobiogeographical origins of Fasciola hepatica and F. gigantica in light of new DNA sequence characteristics of F. nyanzae from hippopotamus». Frontiers in Veterinary Science. 9: 990872 (28 pp.). doi: 10.3389/fvets.2022.990872.