Comparative morphometry of Fasciola gigantica (Cobbold, 1855) and Fasciola hepatica (Linnaeus, 1758) coexisting in Philippine Carabao (Bubalus bubalis)

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Coexisting individuals of Fasciola hepatica and Fasciola gigantica in livers of slaughtered carabaos grazed in Tacurong City, Sultan Kudarat, Mindanao, Philippines were compared based on their body length and widest body width, body width at ovary level, cone width along the proximal end of acetabulum, the distance from the anterior body to the proximal end of the acetabulum; and the distance from the posterior end of the acetabulum to the posterior body end. Flukes were relaxed in phosphate buffered saline solution containing MgCl2 crystals, and were fixed in alcohol formalin acetic acid. In the four infected livers, F. gigantica was the dominant species (66.7-83.3%) relative to F. hepatica (16.7-33.3%). While F. gigantica was longer (16-39 mm), with 64.0% of the flukes in the range 30-39 mm, they had narrower bodies (4-10 mm) compared to F. hepatica (7-11 mm). Body width measurements at the ovary level revealed a wider range in F. gigantica (2-9 mm) compared to F. hepatica (4-8 mm). Cone width ranged 2-4 mm and overlapped between the species. The distance from the anterior body end to the proximal end of the acetabulum of almost 96.0% of the flukes was 2-3 mm. The measurement from the distal end of the acetabulum to the posterior end of the body in 65% individuals of F. gigantica ranged 26-37 mm, and the other worms overlapped with those of F. hepatica. Although there were overlaps in body measurements between the two species, only the differences in the mean body length; mean widest body width; and mean of the distance from the posterior end of the acetabulum to the posterior end of body were significant (p ≤ 0.05). While the significant difference in the morphometrical values noted in the current study alongside marked difference in the appearance/shape are clearly useful in the identification of Fasciola spp., the commonly reported coexistence of both forms together with the existence of intermediate forms in the liver of any susceptible mammalian host species may point to seem to these merely as polymorphic populations, and not necessarily as separate species. It would be interesting to examine various aspects of the reproductive organs of flukes in view of the recognized differences in testicular and ovarian patterns (Bergeon and Laurent, 1970) between the species.