The pathology of Babesia hylomysci infection in mice II. Kidney lesion

Interactions between Babesia microti merozoites and rat kidney cells in a short-term in vitro culture and animal model

Babesiosis is one of the most common infections in free-living animals and is rapidly becoming significant among human zoonoses. Cases of acute renal failure in humans caused by Babesia spp. have been described in the literature. The kidneys are characterised by intense blood flow through the blood vessels, which increases the likelihood of contact with the intra-erythrocyte parasite. The aim of this study was to observe the influence of B. microti (ATCC 30221) on renal epithelial cells in vitro cultured (NRK-52E line) and Wistar rats' kidney. Both NRK-52E cells and rats' kidney sections were analysed by light microscopy, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH). Necrotic changes in renal epithelial cells have been observed in vitro and in vivo. In many cross-sections through the rats' kidney, adhesion of blood cells to the vascular endothelium, accumulation of erythrocytes and emboli were demonstrated. In NRK-52E culture, elements with a distinctly doubled cell membrane resembling B. microti were found inside the cytoplasm and adjacent to the cell layer. The study indicates a chemotactic tendency for B. microti to adhere to the renal tubules' epithelium, a possibility of piroplasms entering the renal epithelial cells, their proliferation within the cytoplasm and emboli formation.

Babesia divergens infections in the Mongolian gerbil: characteristics of a human strain

A strain of the cattle piroplasm Babesia divergens isolated from a fatal human infection was propagated in the Mongolian gerbil through 150 semi-continuous intraperitoneal passages. The infection was normally fatal; death, accompanied by profuse haemoglobinuria and debilitation, occurred as early as 44 h after intraperitoneal inoculation of heavily parasitized blood with precipitous drops in red blood cell and platelet counts. The average maximum parasitaemia achieved increased on continuous passage reaching 80% by the 150th stage. Twenty-four hours after infection erythrophagocytosis and splenic congestion were apparent by light and electron-microscopical examination and by 48 h hepatic necrosis, renal tubular damage with haemoglobin cast accumulation and ischaemic necrosis of ileal mucosa had developed. Gerbils were highly susceptible to small numbers of parasites when the inoculum was either fresh parasitized blood in high dilution or erythrocytes concentrated from animals showing minimal parasitaemia. Animals inoculated with parasites preserved in dimethyl sulphoxide at low temperatures usually developed fatal infections. However, occasionally animals suffered at most a low grade parasitaemia subsequent to recovery with parasite elimination. These animals were immune to further challenge, and no chronic infections developed. A field strain of B. divergens isolated locally from a case of bovine redwater behaved similarly to the human strain on continuous passage in gerbils.