Enzymatic changes in serum and tissues in fowl infected with a neurotropic-mesogenic strain of Newcastle disease virus.

Chickens aged 6 weeks were inoculated intravenously with two strains of Newcastle disease virus: a mesogenic strain (MAJ) with relatively high neurotropism and a lentogenic strain (V5K7E1). The levels of several enzymes were determined in serum and in various tissues of the infected birds. A marked increase in lactic dehydrogenase (LDH) level in skeletal muscles and a decrease of LDH activity in liver were found in chickens infected with the MAJ strain. Differentiation of LDH isoenzymes by either heating or electrophoresis indicated a significant elevation of LDH 5 iso-enzyme in breast muscle and of LDH 1 in leg muscle, while the activity of LDH 1 in liver decreased. Similar changes were found in the activity of hydroxy butyrate dehydrogenase. Infection with the MAJ strain caused an increase of acid phosphatase activity in breast muscle, a marked decrease of alkaline phosphatase and malate dehydrogenase and an increase of glutamate-oxaloacetate transaminase activities in the intestine. These findings indicate the origin of the changes in enzyme levels found in serum. The possibility of metabolic changes in muscles and liver resulting from damage to the central nervous system is discussed. Inoculation of chickens with the lentogenic strain produced no significant change in the enzyme profile of tissues and serum.