The onset and development of anaemia and hypoalbuminaemia in rabbits infected with Fasciola hepatica

Abstract The turnover of certain blood constituents using rabbit albumin trace-labelled with 125 I, and simultaneously erythrocytes labelled with 51 Cr, was studied in rabbits over a 10-week period following infection with 50 metacercariae of Fasciola hepatica . No abnormal leak of either albumin or red cells into the gut occurred until about 6 weeks after infection, i.e. at about the time the parasites enter the bile ducts; from this time onward the infected rabbits showed progressive hypercatabolism and increased gut leak of both albumin and red cells. These losses were followed by a marked reduction in the polyvinylpyrrolidone (PVP) values of the infected rabbits. Confirmation of the onset of a significant transfer of plasma macro-molecules into the gut of infected rabbits at 6 weeks after infection was obtained from studies on the faecal excretion of labelled PVP. The extent to which the pathogenic effects of the parasite increase, following establishment within the bile ducts, was assessed by comparing in the same animals albumin degradation rates and loss of red cells into the gut at 18 weeks after infection with those measurements 10 weeks previously. Hypercatabolism of albumin and intestinal loss of red cells were much more pronounced in the longer established infection. The aetiology of this further increase in albumin catabolism and the relationship between plasma and red cell loss was determined by comparing the faecal “clearances” of plasma and red cells between 6 and 8 weeks with those obtained between 18 and 19 weeks after infection by the simultaneous use of 95 Nb-labelled albumin and 51 Cr-labelled red cells. “Clearance” values of both plasma and red cells were significantly greater in the infected rabbits at 18 weeks than at 8 weeks after infection, suggesting that blood loss suffered by the host is determined not only by the number of parasites present within its bile ducts, but also by their size and nutritional requirements.