Anaemia in advanced chronic fasciolosis.

The association between fasciolosis-induced anaemia and related factors has been quantified in a rodent model. Haematological parameters were analysed in Wistar rats at 20 and 60 weeks post-infection (p.i.). Pigment stones and bile specimens were collected. Serum IgG1, IgG2a and IgE were determined in rat serum samples. Cytokine levels have been correlated with haematological parameters. The screening for gastrointestinal bleeding was carried out. Bacteriological bile cultures revealed viable bacteria in 53.8% of specimens at 60 weeks p.i. The results show that the type of anaemia in fasciolosis might be considered a biomarker of the chronicity period of the disease, changing from normocytic to macrocytic in the early chronic period (20 weeks p.i.) and to microcytic in the advanced chronic period (60 weeks p.i.). Likewise, changing from normochromic in the early chronic period to hypochromic in the advanced chronic period. Multivariate analysis suggested an association between anaemia and the following factors: fluke burden, eggs per gram of faeces, body area of parasite, presence of blood in faeces, IgG1 and eosinophil levels, and % of splenic weight. Of all variables analysed, the fluke burden is the one which presents the highest anaemia risk, even exceeding the variable presence of blood in faeces. The development of anaemia appears to be complex and may involve multiple mechanisms. However, to the mechanisms that until now explain Fascioliosis-related anaemia (compensatory increase in erythrocyte production and a continuous drain on iron stores resulting from the parasites' blood-sucking activities) the following causes ought to be added: haemolysis of red blood cells, the general effects of inflammation on erythropoiesis, concomitant parasitic and bacterial infections and pre-morbid nutritional abnormalities. Extrapolation to human fasciolosis is discussed. The results of the rodent model lead to the assumption that a high risk of anaemia in subjects with a heavy parasitic burden in human hyperendemic areas of fasciolosis is to be expected.

High risk of bacterobilia in advanced experimental chronic fasciolosis.

Fasciolosis is recognized as an important human disease. Wistar rats experimentally infected with Fasciola hepatica were examined using data obtained in the advanced chronic state of the disease (200, 300 and 400 days post-infection, dpi). Pigment stones (PS) and bile specimens were collected. The same procedure was applied in control rats. Liver tests were determined using stored serum samples. Bacteriological bile culture revealed viable bacteria (Escherichia coli, 45% of cases, Enterococcus faecalis, 45% and Klebsiella pneumoniae, 10%). The presence of bacterobilia was associated with liver serum enzymes, including aspartate aminotransferase (AST or SGOT), alanine aminotransferase (ALT or SGPT), alkaline phosphatase (AP) and total bilirubin levels. Multivariate analysis suggested an association between bacterobilia and the following factors: duration of parasitic infection and intensity of parasitic infection supported the impression that the obstruction caused by advanced chronic fasciolosis in the rat may be related to biliary sepsis. Extrapolation to human infection in fasciolosis hyperendemic areas is discussed. In conclusion, the results of the rodent model should lead to a reconsideration of treatment features in human disease, i.e. therapeutic strategies should not only include a parasitic treatment but also consider the possibility of bacterial co-infection.

Crowding effect on adult growth, pre-patent period and egg shedding of Fasciola hepatica.

Fascioliasis pathogenesis depends on fluke burden. In human hyperendemic zones, individual infection intensities reach very high levels and the majority of infected subjects should be in the advanced chronic phase. The rat model offers a useful approach for pathological research in the advanced chronic period. The influence of infection intensity per rat on fluke development, pre-patent period and egg shedding (eggs/g faeces/worm) was analysed in 3 groups (I: 1-3 worms/rat; II: 4-6; III: 7-9). Ontogenetic trajectories of fluke body measures followed a logistic model. Results showed that when the burden increases, the maximum values of fluke measures decrease. The crowding effect is manifest when fluke measures approximate their maximums in the advanced chronic stage. The pre-patent period and egg production decrease when the burden increases. This means that measurements of eggs per gramme of faeces tend to underestimate the fluke burden. The present study demonstrates how to quantify the fascioliasis experimental rat model crowding effect on adult growth, pre-patent period and egg production. This quantification may be of great interest in epidemiological studies and in experimental research on the in vivo actions of different anthelminthic drugs and vaccines, pathology, immunology and resistance studies.