L3 and adult Ostertagia (Teladorsagia) circumcincta exhibit cyanide sensitive oxygen uptake

Abstract Oxygen consumption by L 3 and adult Ostertagia ( Teladorsagia ) circumcincta was examined in vitro to determine whether oxygen can be utilised in metabolism. The oxygen concentration in the abomasal fluid of sheep infected with O. circumcincta was also measured. Rates of consumption (in nmol O 2 /h/1000 worms) were 13 ± 1 in sheathed L 3 , 34 ± 6 in exsheathed L 3 , and 1944 ± 495 in adult worms. Constant rates of consumption were maintained until media oxygen concentration dropped to between 10 and 20 μM. Consumption was inhibited 95% by cyanide in L 3 and 74% in adults. Oxygen concentration in abomasal fluid varied between 10 and 30 μM in both infected and uninfected animals. During infection, oxygen concentration decreased slightly with increased abomasal pH, though the correlation between the two was poor ( r  = −0.30). In conclusion, O. circumcincta can consume oxygen and oxygen concentration at the infection site is sufficient to support at least some aerobic metabolism.