CIAS detection of Fasciola hepatica/F. gigantica intermediate forms in bovines from Bangladesh.

Fascioliasis is an important food-borne parasitic zoonosis caused by two trematode species, Fasciola hepatica and Fasciola gigantica. The characterisation and differentiation of Fasciola populations is crucial to control the disease, given the different transmission, epidemiology and pathology characteristics of the two species. Lineal biometric features of adult liver flukes infecting livestock have been studied to characterise and discriminate fasciolids from Bangladesh. An accurate analysis was conducted to phenotypically discriminate between fasciolids from naturally infected bovines (cattle, buffaloes) throughout the country. Morphometric analyses were made with a computer image analysis system (CIAS) applied on the basis of standardised measurements and the logistic model of the body growth and development of fasciolids in the different host groups. Since it is the first ever comprehensive study of this kind undertaken in Bangladesh, the results are compared to pure fasciolid populations of F. hepatica from the European Mediterranean area and F. gigantica from Burkina Faso, geographical areas where both species do not co-exist. Principal component analysis showed that the biometric characteristics of fasciolids from Bangladesh are situated between F. hepatica and F. gigantica standard populations, indicating the presence of phenotypes of intermediate forms in Bangladesh. These results are analysed by considering the present emergence of animal fascioliasis, the local lymnaeid fauna, the impact of climate change, and the risk of human infection in the country.

Distribution of Fasciola hepatica and F. gigantica in the endemic area of Guilan, Iran: Relationships between zonal overlap and phenotypic traits.

Fascioliasis is a zoonotic disease emerging in numerous parts of the world. In any endemic area, the characterisation of scenarios and patterns of infection must always be considered the starting point before implementing any control measure. Fascioliasis is a parasitic disease of different epidemiological, pathological and control characteristics depending on the endemic area and the causal agent, Fasciola hepatica and Fasciolagigantica. Classically it has been accepted that F. hepatica is present worldwide, while the distribution of the two species overlaps in many areas of Africa and Asia. Fascioliasis caused by F. hepatica, F. gigantica and intermediate forms is present in Guilan province, a complicated epidemiological situation where the highest human infection rates have been described in Iran. Morphometric tools were used to analyse the possible relationship between liver-fluke metric traits and geographical and altitudinal distribution. This is the first study in which a detailed distribution of both Fasciola species is analysed in a human fascioliasis endemic area with a zonal overlap transmission pattern. An accurate analysis was conducted to phenotypically discriminate between fasciolids from naturally infected livestock (cattle, buffaloes, sheep and goats). The distribution of the % F. hepatica-like (F.h.) and F. gigantica-like (F.g.) flukes detected in each liver versus altitude (m) in each group was analysed. The presence of F.g. specimens mainly in locations below sea level (average: 11.23% F.h., 88.77% F.g.), the presence of both species with similar intensity at 1-99m (average: 56.95% F.h., 43.05% F.g.) and the presence of F.h. specimens mainly from 100 to 999m (average: 71.69% F.h., 28.31% F.g.) as well as in locations with an altitude above 1000m (average: 97.48% F.h., 2.52% F.g.) are noteworthy. A significant positive correlation was obtained between altitude and % F.h., and a significant negative correlation was obtained between altitude and % F.g. The results show that F.g. populations in cattle, buffaloes and sheep share larger size values, but smaller specimens are present mainly in lowland populations located below sea level, independently of the host species (cattle, buffalo). F.g. from lowland cattle presented larger worm size variability. Four different fascioliasis transmission areas may be distinguished in Guilan: (a) lowland coastal areas neighbouring the Caspian Sea shore, below sea level, where basically F. gigantica-like specimens are found; (b) a coastal plain with an altitude between 1 and 100m where both species co-exist; (c) areas with altitude values of 100-999m where mainly F. hepatica-like specimens are found; (d) highland mountainous areas, where basically F. hepatica-like specimens are found. The study of the influence of the host species on the liver fluke was also carried out by a size-out analysis. This is the first report concerning the decisive influence exercised by the host species on the metric traits of F. gigantica adults.

Fasciola hepatica phenotypic characterization in Andean human endemic areas: valley versus altiplanic patterns analysed in liver flukes from sheep from Cajamarca and Mantaro, Peru.

Fascioliasis is a zoonotic parasitic disease caused by Fasciola hepatica and Fasciola gigantica. Of both species, F. hepatica is the only one described in the Americas, mainly transmitted by lymnaeid snail vectors of the Galba/Fossaria group. Human fascioliasis endemic areas are mainly located in high altitude areas of Andean countries. Given the necessity to characterize F. hepatica populations involved, the phenotypic features of fasciolid adults infecting sheep present in human fascioliasis endemic areas were analysed in the Cajamarca Valley and Mantaro Valley (valley transmission patterns) and the northern Bolivian Altiplano (altiplanic transmission pattern). A computer image analysis system (CIAS) was applied on the basis of standardized measurements. The aforementioned highland populations were compared to standard lowland natural and experimental populations of European origin. Liver fluke size was studied by multivariate analyses. Two phenotypic patterns could be distinguished in F. hepatica adult size: the valley pattern (Cajamarca and Mantaro, Peru) and the altiplanic pattern (northern Altiplano, Bolivia). Results showed that the Andean valley population and European standard populations presented a phenotypic homogeneity. The Altiplano population showed a large size range with a pronouncedly lower minimum size indicating that uterus gravidity is reached at a smaller size than in valley populations. The results of this study demonstrate that there is no apparent relationship between the shape of fasciolid adults with regard to altitudinal difference or geographical origin and that allometry-free shape appears as a more stable trait than size in fasciolid species. Results are analysed in terms of intensity/crowding effect aspects and permanent/seasonal transmission characteristics.

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 300 dpi 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.

Patterns in size and shedding of Fasciola hepatica eggs by naturally and experimentally infected murid rodents.

Using samples collected on the island of Corsica, a comparative study was done of the morphometry of Fasciola hepatica eggs shed by cattle and by naturally and experimentally infected murid rodents (wild Mus musculus and Rattus rattus and Rattus norvegicus Wistar laboratory strain). Eggs shed by murids are smaller in size than those shed by naturally infected cattle. A second study analyzed the number of F. hepatica eggs shed in murid feces at different time intervals, i.e., months, days, and 6-hr periods, by the Kato-Katz technique. Both experimentally and naturally infected black rats (R. rattus) were used, and Wistar rats were experimentally infected and included for comparison. The present studies prove that black rats R. rattus are able to shed eggs independently from the liver fluke isolate and that egg shedding occurs throughout the life of this host species, uninterrupted during all the months analyzed in a 2-yr period. Moreover, the results suggest that this shedding is continuous, with eggs appearing in the feces daily. The results on egg shedding by wild black rats R. rattus reach their maximum shedding in spring and autumn and a maximum during twilight hr. These chronobiological patterns appear to favor parasite transmission, both seasonally and daily.