Epidemiology of Balkan endemic nephropathy.

The first outbreak of Balkan endemic nephropathy (BEN) was reported between 1955 and 1957, initially in Serbia and soon afterwards in Croatia and in Bosnia and Herzegovina. The disease appears to be of a focal nature. In Yugoslavia at least six foci are known, generally along major rivers of the Danubian river basin, in areas that have often been flooded in the past and even today suffer from high ground waters. The prevalence rate of the disease is reported to be between 2 and 10%. In the endemic area of Croatia, a systematic survey of 'in-the-field' cases of the disease since 1975 has shown a prevalence between 0.5 and 4.4%. When suspected cases are also included the prevalence rises to 20% or more. Specific mortality (based on official statistics) during the period 1957-1984 averaged 1.54/1000 per annum, but some studies have shown that mortality is actually more than twice as high as this figure. More women are affected than men; women also more frequently die of BEN than men. Lethality is extremely high. A striking feature of BEN is the familial occurrence of the disease. Incidence does not seem to be connected with ethnic group differences. Immigrants into the endemic area may also contract the disease. An increased incidence of malignant tumours of the urinary tract has been recorded in populations living in endemic areas. Epidemiological characteristics suggest that the disease is contracted in the domestic situation, or possibly from other family members. Factors to be considered are food, water or long close contact. It is also possible that the disease is contracted outside the house, in connection with farming activities, since the affected persons are almost exclusively farmers.     

Clinical features of Balkan endemic nephropathy.

This paper describes the clinical symptoms and signs of Balkan endemic nephropathy (BEN). The initial asymptomatic period followed by weakness and lassitude during renal insufficiency is emphasized. Non-characteristic lumbar pain may be present and episodes of macrohaematuria may occur. There is no fever, no severe dysuria, and no general disease preceding the symptoms. No oedema of the nephrotic type is recognized. Working capacity is unaffected until the late stage of the disease. In the advanced stages pallor of the skin and xantochromia of palms and soles are noticeable. Blood pressure is normal, but in the advanced phase may be elevated. In the uraemic phase a full uraemic syndrome is found. Urothelial tumours are frequent, occurring in 2-47% of cases; tumour cells may be found in the urine. Proteinuria of tubular type may be found early; in the uraemic phase it is constant. In the urinary sediment there are scarce white and red blood cells (the latter episodically abundant). Bacteriuria is present in about 20% of women patients. Glucosuria (less than 10%) and aminoaciduria (less than 10%) have been reported. In the early stages of BEN the urine concentration capacity is impaired earlier than renal blood flow and glomerular filtration rate. Enzymuria is present in the early phases. Tamm-Horsfall protein may be increased in the urine. Normo- or hypochromic normocytic hyporegenerative anaemia is a frequent finding. Bone marrow and leucocytes are normal. Serum proteins and immunoglobulins are not altered. Complement is normal; anti-glomerular basal membrane and anti-tubular basal membrane are negative. On radiography, kidney size varies from normal to the size of a small contracted kidney. The clinical picture of the disease is that of a slowly progressing tubulo-interstitial chronic nephritis.     

Some features of Balkan endemic nephropathy.

This paper presents a brief review of the initial investigative efforts in three countries--"Yugoslavia", Bulgaria and Romania--on Balkan endemic nephropathy. There is now expert agreement that the disease represents an unusual type of chronic interstitial nephropathy of unknown aetiology. The epidemiological and histopathological data are summarized very briefly. The clinical symptoms and signs and the diagnostic approach to the disease are presented in greater detail. The possibilities of an early diagnosis in the latent, subclinical and early phases of the disease are discussed, together with the importance of the detection of a tubular type of proteinuria and enzymuria as a diagnostic aid.     

Laboratory investigations in Balkan endemic nephropathy

Serum samples from three patients with Balkan endemic nephropathy (BEN) were inoculated intraperitoneally to guinea pigs. After a very long incubation period (58-273 days) the animals developed an experimental disease characterized by apathy, tremor, convulsions and a fatal outcome. The disease could be serially propagated, the same clinical symptoms being recorded at each of the three passages performed. The morphological features of the experimental disease included glomerular and tubular lesions and the presence of interstitial fibrous and lymphoplasmocytic reactions. Different hypotheses on the etiology of BEN are discussed.     

Ochratoxin A in human blood and Balkan endemic nephropathy

The etiology of Balkan endemic nephropathy, a kidney disease encountered among the rural population living in regions along several big rivers on the Balkan Peninsula, remains unknown in spite of many hypotheses put forward and tested. One hypothesis involves mycotoxins as the causal agent. The mycotoxin ochratoxin A has been demonstrated to have a potent nephrotoxic effect in all mammalian species tested so far.The results of analysis of ochratoxin A in human blood samples by an analytical method based on the measurement of fluorescence spectra, before and after incubation with carboxypeptidase A, is described. For a 2-g-sample the detection limit of the method is 1–2 ng/g serum. High performance liquid chromatography used for the confirmation of ochratoxin A identity by means of several derivatives of the molecule is also described. Out of more than 600 samples collected in an endemic region in Yugoslavia about 7% were positive for ochratoxin A. The highest concentration found was 40 ng ochratoxin A/g serum.     

Virological and immunological study of 20 patients with Balkan endemic nephropathy

A virological and immunological study was carried out in 20 cases of Balkan endemic nephropathy (BEN) belonging to two distinct geographical areas of a Romanian county. Cytopathogenic agents could be isolated in the BHK-21 cell line from 14 urine samples and from one kidney biopsy specimen. Sera from BEN patients gave autologous and heterologous neutralization reactions against several cytopathogenic agents, within the same or from the other geographical area. Humoral and cell-mediated immunity tests against standard antigens and one of the cytopathogenic agents revealed a general preservation of immune reactivity in BEN patients.     

Immunological investigations in inbred mice chronically infected with cytopathogenic agents isolated from human cases of Balkan endemic nephropathy

An experimental chronic infection was induced in inbred A2G and CBA mice by repeated administration of four cytopathogenic agents isolated from human cases of Balkan endemic nephropathy (BEN). The slight humoral and cell-mediated immune responses to the BEN agents recorded in A2G mice were associated with autoimmunity and hypersensitivity phenomena. In contrast, the normal, intense immune response observed in CBA mice was not accompanied by any immunopathological changes. In both mouse lines the chronic infection with human BEN agents led to a secondary immune deficiency against sheep red blood cells or tuberculin.     

The role of lecithin cholesterol acyltransferase and organic substances from coal in the etiology of Balkan endemic nephropathy: a new hypothesis.

Balkan endemic nephropathy (BEN) occurs in Serbia, Bulgaria, Romania, Bosnia and Herzegovina, and Croatia. BEN has been characterized as a chronic, slowly progressive renal disease of unknown etiology. In this study, we examined the influence of soluble organic compounds in drinking water leached from Pliocene lignite from BEN-endemic areas on plasma lecithin-cholesterol acyltransferase (LCAT) activity. We found that changes for all samples were the most prominent for the dilution category containing 90% plasma and 10% of diluting media. Water samples from BEN villages from Serbia and Romania showed higher LCAT inhibiting activity (p=0.02) and (p=0.003), respectively, compared to deionised water and non-endemic water. A secondary LCAT deficiency could result from this inhibitory effect of the organic compounds found in endemic water supplies and provide an ethiopathogenic basis for the development of BEN in the susceptible population.     

Serum antibodies to papova viruses (BK and SV 40) in subjects from the area with Balkan endemic nephropathy

The presence of antibodies to BK virus and SV40 was investigated in 63 patients with Balkan endemic nephropathy (BEN) and in 83 apparently healthy subjects from the endemic area. Serum antibodies to BK virus were detected in 95.2% of the former and in 74.7% of the latter, high antibody levels being prevalent in the age groups 41-60 years. Antibodies to SV40 were absent in the BEN patients and their frequency in the healthy subjects (27.7%) was much lower than that previously recorded in healthy persons from other zones of Romania (40%). The results obtained plead for a prevalence of BK virus infection in the endemic area with BEN.     

Relevance of a rat model of papillary necrosis and upper urothelial carcinoma in understanding the role of ochratoxin A in Balkan endemic nephropathy and its associated carcinoma.

Ochratoxin A is nephrotoxic and has been implicated in the genesis of Balkan endemic nephropathy (BEN), a condition that leads to end-stage renal disease and upper urothelial tumours. This compound induces renal parenchymal carcinoma in male mice only, and is not considered to be a potent carcinogen nor is there experimental evidence of its propensity to cause upper urothelial carcinoma. There is, however, evidence that exposure to more than one mycotoxin may be an important factor in the clinical spectrum of BEN. Analgesic nephropathy is clinically different, but is also associated with an upper urothelial carcinoma. The combination of urothelial initiation and an acute papillary necrosis in rats produces upper urothelial carcinoma. This two-stage experimental model offers the potential to assess the role of ochratoxin A in BEN-associated upper urothelial carcinoma under experimental conditions.     

Ochratoxin A as a potential etiologic factor in endemic nephropathy: lessons from toxicity studies in rats.

Various reports suggest that chronic dietary exposure to ochratoxin A (OTA), a mycotoxin frequently detected in various food items may be linked to the pathogenesis of endemic nephropathy, a chronic tubulointerstitial kidney disease which occurs in geographically limited areas of the Balkan region. OTA is a potent nephrotoxin and renal carcinogen. However, the pathological lesions observed in kidneys of rats treated with OTA appear be rather different from the clinical and pathological characteristics of endemic nephropathy. Moreover, increasing evidence suggests that OTA does not bind to DNA but induces tumors by an epigenetic, thresholded mechanism. This implies that there is a dose below which no adverse health effects are expected to occur. Based on food consumption data and OTA serum concentrations, it appears that human exposure - even in areas with relatively high dietary exposure to OTA such as endemic villages - is several orders of magnitude below doses known to cause nephrotoxicity and tumor formation in laboratory animals. While it is undoubtedly important to encourage prevention of food contamination by OTA and other mycotoxins, these observations suggest that OTA is not likely to be an etiological factor involved in BEN and indicate a need to search for new clues for the etiology of this endemic kidney disease.     

Ochratoxin A in human sera in the area with endemic nephropathy in Croatia

Ochratoxin A (OA) is nephrotoxic fungal metabolite (mycotoxin) occurring in foodstuffs. The compound is causally associated with mycotoxin porcine nephropathy, a disease comparable with a human kidney disease called endemic nephropathy (EN). In this paper we presented results obtained over a 10-year period in the hyperendemic village Kaniža, and in control villages where no clinical cases of nephropathy had been found. In the hyperendemic village Kaniža and non-endemic villages the incidence of OA in human blood was up to 4.5% (range 2–50 ng/ml) and up to 2.4% (range 2–10 ng/ml), respectively. Almost all samples of food and feed, collected randomly in the hyperendemic village were found to contain OA. Considering marked exposure to OA in Kaniža, it was assumed that incidence of EN in this population could be related to OA contamination of food and feed. Ireland Ltd.