The effect of timing of copper oxide wire particle treatment on establishment of Haemonchus contortus in lambs

Abstract

The interrelationship between copper oxide particle (COWP) treatment and H. contortus infection in lambs was investigated. Particular emphasis was placed on the effect of timing of the COWP adminstration on the establishment of H. contortus. There were 3 treatment groups. Control (CO) was infected with 7160 H. contortus larvae with no COWP administered. The second group, 'copper early' (CE) was given 2.5g COWP and infected with 7160 H. contortus larvae over a 10 day period commencing 4 days after COWP administration. The third group,'copper late' (CL) was infected with 7160 H. contortus larvae over a 10 day period and 28 days after start of infection, 2.5g COWP was administered. The treatment groups were designed to examine the efficacy of COWP on both larval and adult H. contortus. CE was to test the efficacy of COWP against ingested larvae while CL was to test the efficacy of COWP against established adults. The CO group was needed to compare the results from the other groups and to calculate efficacy of COWP. Thirty 7 month old Coopworth lambs were allocated to the 3 groups on the basis of liveweight and liver copper status. Faecal egg counts were taken during the 40 day trial. Post-mortem examinations were performed at the end of the trial to recover COWP, parasites and to determine abomasal pH and liver copper levels. Parasites recovered were counted, separated into male and females and the eggs in utero of the females counted. The timing of administration of COWP had no effect on the efficacy against H.contortus with a 97.4% and 98.5% efficacy for groups CL and CE respectively. COWP treatment increased the mortality of females by 47.9% and 52.3% for groups CE and CL respectively when compared to CO. COWP treatment reduced the fecundity of the remaining females by 39% and 46% for groups CL and CE respectively compared to CO. Abomasal pH of the COWP treated groups (CE and CL) at slaughter was significantly higher than that of CO but this is suggested to be due to timing of the last meal before slaughter. Faecal egg count results were variable but reflected the poor timing of the sampling. It was concluded that COWP have a high anthelmintic efficacy against adult and larval H. contortus in lambs. Other significant results were the increased mortality of the females and the reduced fecundity of the remaining females. The dose used (2.5g COWP) was half that used in a previous trial with similar results being achieved. 2.5g is the recommended dosage used to prevent the development of, or to treat copper deficiency in lambs and as such has a high safety margin. It is suggested that the administration of 2.5g COWP to copper sufficient sheep to control H. contortus infection is unlikely to cause copper toxicity.