Occurrence of Echinococcus felidis in Apex Predators and Warthogs in Tanzania: First Molecular Evidence of Leopards as a New, Definitive Host and Implications for Ecosystem Health

(1) Background: Limited information on Echinococcus species among the wildlife in Tanzania has created a significant knowledge gap regarding their distribution, host range, and zoonotic potential. This study aimed to enhance the understanding of Echinococcus felidis transmission dynamics within the great Serengeti ecosystem. (2) Methods: A total of 37 adult Echinococcus specimens were collected from a leopard (Panthera pardus) (n = 1) in Maswa Game Reserve and 7 from a lion (Panthera leo) (n = 1) in Loliondo. Two hydatid cysts were also obtained from warthogs (n = 2) in the Serengeti National Park. (3) Results: Morphological examination revealed infertile cysts in warthogs that were molecularly identified as E. felidis. This marks the first molecular evidence of E. felidis in leopards and warthogs in Tanzania. Pairwise similarity analysis showed 98.7%–99.5% identity between Tanzanian, Ugandan, and South African isolates. Thirteen unique haplotypes were identified, with a haplotype diversity of (Hd = 0.9485) indicating genetic variability. Phylogenetic analysis grouped E. felidis into a single lineage, with the leopard isolate forming a distinct haplotype, suggesting leopards as an emerging host. Lion and warthog isolates shared multiple mutational steps, suggesting possible genetic divergence. (4) Conclusions: This study confirms African lions and leopards as definitive hosts and warthogs as potential intermediate hosts of E. felidis in the Serengeti ecosystem. Our findings highlight disease spillover risks and stress the importance of ecosystem-based conservation in wildlife–livestock overlap areas. Although E. felidis is believed to be confined to wildlife, the proximity of infected animals to pastoralist communities raises concerns for spillover. These findings highlight the importance of ecosystem-based surveillance, especially in wildlife–livestock–human interface areas.