"No-
blood disease" is a severe, feed-related
anemia of channel catfish. Pathological features in advanced cases include almost total absence of circulating red blood cells, hepatic fatty change, megaloblastic arrest of hematopoiesis, and
intussusceptions of the small intestine. In view of similarities to
folate deficiency in man studies were made regarding the intake and metabolism of
folic acid. When a bacterial culture medium, containing inorganic
salts and
folic acid as the sole
carbon source, was inoculated with a small sample of
anemia-producing feed, over 95% of the
folate was destroyed. A yellow precipitate formed and had the characteristic uv spectrum of
pteroic acid; it represented 32% of the
folate originally present. Differential microbiological assays revealed that the same
anemia-producing feed contained 20 times as much
folate activity for Streptococcus fecalis as for Lactobacillus casei (59 micrograms/g vs 2.6 micrograms/g). This growth response is compatible with an excess of
pteroic acid and/or formyl-
pteroic acid which support the former but not the latter organism. Plasma
folate activity (mean +/- SD, ng/ml) assayed with L. casei and S. fecalis in 22 normal catfish (hematocrit range 32-43) was 17.2 +/- 6.2 and 23.4 +/- 13.8, respectively. Comparable values in 15 anemic catfish (hematocrit range 0 to 30) were 35.5 +/- 33.7 and 58.7 +/- 76.5. The mean plasma pteroate activity, estimated by subtraction, was 6.2 and 23.2 ng/ml, respectively, in normal and anemic fish. Fingerling catfish raised under controlled conditions on feed containing 130 mg/kg of
pteroic acid failed to
gain weight and developed
anemia with the characteristic red cell morphologic features that are seen in the naturally occurring disease. We conclude that severe
anemia in channel catfish can be caused by abnormal
folate metabolism and may be due to ingestion of
folic acid-breakdown products, such as
pteroic acid. It is postulated that microorganisms in contaminated feed synthesize
folate which, in turn, is converted to pteroate by a pseudomonad or similar organism.