The dual burden of animal and human zoonoses: A systematic review

Zoonoses can cause a substantial burden on both human and animal health. Globally, estimates of the dual (human and animal) burden of zoonoses are scarce. Therefore, this study aims to quantify the dual burden of zoonoses using a comparable metric, "zoonosis Disability Adjusted Life Years" (zDALY).

We systematically reviewed studies that quantify in the same article zoonoses in animals, through monetary losses, and in humans in terms of Disability Adjusted Life Years (DALYs). We searched EMBASE, Web of Science, Scopus, PubMed, and Google Scholar. We excluded articles that did not provide the data to estimate the zDALY or those for which full text was not available. This study was registered at PROSPERO, CRD42022313081.

We identified 512 potentially eligible records. After deduplication and screening of the title and abstract, 23 records were assessed for full-text review. Fourteen studies were included in this systematic review. The data contains estimates from 10 countries, a study at continental level (Asia and Africa), and 2 studies on a global scale. Rabies was the most frequently reported zoonosis where zDALYs were calculated, based on the following included studies: for Kazakhstan 457 (95% CI 342-597), Viet Nam 5316 (95% CI 4382-6244), Asia 1,145,287 (90% CI 388,592-1,902,310), Africa 837,158 (90% CI 283,087-1,388,963), and worldwide rabies 5,920,014 (95% CI 1,547,860-10,290,815). This was followed by echinococcosis, the zDALYs in Peru were 2238 (95% CI 1931-2546), in China 1490 (95% CI 1442-1537), and worldwide cystic echinococcosis 5,935,463 (95% CI 4,497,316-7,377,636). Then, the zDALYs on cysticercosis for Mozambique were 2075 (95% CI 1476-2809), Cameroon 59,540 (95% CR 16,896-101,803), and Tanzania 34,455 (95% CI 12,993-76,193). Brucellosis in Kazakhstan were 2443 zDALYs (95% CI 2391-2496), and brucellosis and anthrax in Turkey 3538 zDALYs (95% CI 2567-6706). Finally, zDALYs on leptospirosis in New Zealand were 196, and Q fever in Netherlands 2843 (95% CI 1071-4603). The animal burden was superior to the human burden in the following studies: worldwide cystic echinococcosis (83%), brucellosis in Kazakhstan (71%), leptospirosis in New Zealand (91%), and brucellosis, and anthrax in Turkey (52%). Countries priorities on zoonoses can change if animal populations are taken into consideration.