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<img SRC="http:/img/fbpe/jvat/v4n1/image522.gif"> ) was found. Precipitation was 194 (121-289) mm water/month (n= 162 months in 27 years, median and its 95% 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<img SRC="http:/img/fbpe/jvat/v4n1/image523.gif"> , 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 = 2.5x10<img SRC="http:/img/fbpe/jvat/v4n1/image523.gif"> 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<img SRC="http:/img/fbpe/jvat/v4n1/image523.gif"> ). The distribution of toxin concentration in both groups was also different (<img SRC="http:/img/fbpe/jvat/v4n1/image524.gif"> test, p=0.024, 7 degrees of freedom). It is then determined that toxin was not detectable in 84.1 % of the cows in the dry season (n = 88) and in only 38.3% of the cows in the rainy season (n = 133) (<img SRC="http:/img/fbpe/jvat/v4n1/image524.gif"> test, p<10<img SRC="http:/img/fbpe/jvat/v4n1/image523.gif"> ).
bovine paraplegic syndrome (BPS); cattle; sodium channel blocking toxin (SCBT); annual variation; rain dependence
