The copper status of some helminth parasites, with particular reference to host-helminth relationships in the gastro-intestinal tract of cattle

Abstract

The copper content was determined in samples of 12 nematode, four cestode, and two trematode species collected from a variety of hosts infected either naturally or experimentally. Copper concentrations varied considerably from species to species, the lowest value recorded being 2 p.p.m. copper (dry weight basis) in the cestode Moniezia benedeni and the highest 604 p.p.m. in the nematode Haemonchus placei, both from cattle. Both the total content and the concentration of copper varied among mature individuals of the same population of the liver fluke, Fasciola hepatica, collected from cattle. Copper levels varied greatly in samples of H. placei and Oesophagostomum radiatum from cattle drawn from different host individuals, whereas values for Bunostomum phlebotomum and M. benedeni also from cattle varied little from host to host. Copper concentrations in samples of H. placei and O. radiatum, recovered from the abomasum and large intestine respectively of experimentally infected calves supplemented daily with copper sulphate, were considerably higher than those in samples from unsupplemented calves. With both species, the increases in worm copper levels were associated with increases in concentrations of soluble copper in the environment. It is suggested that soluble copper in environmental fluids can be absorbed through the cuticle of these helminths. Copper supplementation of the host's diet, on the other hand, had no effect on the copper content of B. phlebotomum Furthermore, the concentration of copper in solution in the contents of the duodenum and jejunum was not elevated significantly by the supplementatlon. The hypothesis that the intestinal helminths of bovines compete with the host for copper was examined, and it is concluded that in dairy calves in southeastern Queensland parasitic gastro-enteritis has a far greater significance as a disease entity in itself than as a factor contributing to the expression of a clinical state of copper deficiency.