The aim of this study was to evaluate the purine levels of lambs experimentally infected with Haemonchus contortus. A total of 12 healthy lambs were divided into two groups, composed of 6 animals each: Group A represented the healthy animals (uninfected), while in Group B the animals were infected with 15 000 larvae of H. contortus. Blood was drawn on days 15, 45 and 75 post-infection (PI) in order to perform the purine analysis (ATP, ADP, AMP, adenosine, inosine, hypoxanthine, xanthine and uric acid) by high pressure liquid chromatography (HPLC) in serum. On day 15 PI a significant (P<0·05) increase in the levels of ATP and inosine was observed in the infected animals, unlike the levels of ADP, adenosine, xanthine and uric acid which were reduced. On day 45 PI a significant (P<0·05) increase in the ATP and xanthine levels in infected animals was observed, contrasting with reduced levels of ADP and uric acid. Finally, on day 75 PI an increase occurred in the levels of ATP, adenosine and hypoxanthine in infected lambs, concomitant with a reduction in the levels of ADP and uric acid (P<0·05). These changes in purine levels may influence the inflammatory process and the pathological events.

Artificially prepared cow pats containing Ostertagia ostertagi eggs were deposited on two pasture plots in May, June and July 1986. Half of the cow pats, placed on one plot, were inoculated with 2000 conidia per gram faeces of the predacious fungus Arthrobotrys oligospora. On the other plot fungus-free control cow pats were placed at the same time. In the faeces generally fewer infective O. ostertagi larvae developed in the inoculated than in the control cow pats. On the herbage around the control cow pats deposited in May, June and July a maxium concentration of infective larvae was found at the same time on the 6th of August 1986. At that time the herbage larval infectivity around inoculated cow pats deposited in May, June and July was subject to a reduction of 48%, 89% and 46%, respectively, compared with fungus-free control cow pats. This experiment indicates that a concentration of 2000 A. oligospora conidia per gram faeces results in a significant lowering of the herbage larval infectivity during the grazing season in Denmark.

Artificially prepared cow pats containing Ostertagia ostertagi eggs were deposited on two comparable grazing plots at weekly intervals during June and July 1987. Before deposition the cow pats, on the one plot, were inoculated with 0·250 g mycelial fragments per kg of faeces of the predacious fungus Arthrobotrys oligospora. On the other control plot comparable numbers of non-inoculated cow pats were placed at the same time. Subsequently, in July, two equal groups of calves were turned out one on each plot to graze for two months after which they were necropsied. The number of infective O. ostertagi larvae in inoculated cow pats was reduced by 42% and herbage larval infectivity around them by 50–71% as compared with the corresponding parameters in control pats and surrounding herbage. After a grazing period of two months the calves on the plot with inoculated cow pats had acquired worm burdens that were on average 37% lower than those of calves on the control plot. The lower degree of parasitism in these calves was also reflected in lower egg counts, lower serum pepsinogen levels and higher body weight.