Correlation between egg-shedding and uterus development in Fasciola hepatica human and animal isolates: applied implications

The emission of Fasciola hepatica eggs in faeces is usually subject to oscillations along time in animals as well as humans. Thus, looking for alternative biological markers reflecting eggs shed per gram of faeces (epg) with lower oscillations may be useful. This study analyzes the possible relationship between liver-fluke uterus area and epg. Uterus area (UA) development of adult F. hepatica obtained at different days post infection (dpi) in a Wistar rat model with isolates obtained from cattle, sheep, pigs and humans from the endemic human fascioliasis zone of the Northern Bolivian Altiplano was analyzed and compared with the number of eggs shed per gram of faeces as obtained through the Kato–Katz technique. The morphometric study of the UA of liver flukes was carried out using image analysis software. The multiple regression model shows that UA is dependent on dpi and isolate. The evolution of UA vs dpi followed a damped model. This work shows a positive relationship between liver-fluke UA and egg production. The complete absence of eggs in the uteri of some parasite individuals at 300dpi was observed, which corresponds to the cessation of egg shedding in the advanced chronic stage. The results obtained suggest the necessity to characterize the isolates employed with regard to geographical as well as host origin in fascioliasis studies in which egg production is used as a biological tag.