Annual variations of the sodium channel blocking toxin in Venezuelan cattle prone to develop the bovine paraplegic syndrome: its dependence on rain

RESUMO

A characteristic of the bovine paraplegic syndrome (BPS) is ventral or sternal decubitus in animals that make unsuccessful efforts to stand when stimulated. Death occurs after a few days. In a previous work we showed the existence of a sodium channel blocking toxin (SCBT) produced by ruminal bacteria in cattle with or liable to develop BPS. The presence of SCBT in bovine plasma sampled monthly during the rainy and dry seasons in animals without BPS has now been observed. A positive correlation between rain precipitation and plasma toxin levels (Spearman's rank correlation coefficient=0.457, n=135, p<10(-5) was found. Precipitation was 194 (121-289) mm water/month (n= 162 months in 27 years, median and its 95 per cent confidence interval) during the rainy season and 7 (0-35) mm water/month (n=109 months in 28 years) during the dry season [p < 10(-6), Mann-Whitney (Wilcoxon) test]. Plasma toxin levels were determined by high performance liquid chromatography (HPLC). Toxin levels, expressed as peak units of area (PUA) at 340 nm, (1 PUA = 2.5 x 10(-6) units of absorbance/cm) were 5.5 (0.0 - 23.3) PUA/nl (n = 133) in the rainy season and 0.0 (0.0 - 1.1) PUA/nl in the dry season (n=88, p=2x10(-6)). The distribution of toxin concentration in both groups was also different (X² test, p=0.024,7, 7 degrees of freedon). It is then determined that toxin was not detectable in 84.1 per cent of the cows in the dry season (n = 88) and in only 38.3 per cent of the cows in the rainy season (n = 133) (X² test, p < 10(-6)).