Toxicity in New Zealand cattle following the administration of copper containing
products
Diploma of Veterinary Clinical Science
in Veterinary Pharmacology and Veterinary Medicine
1982
David Edward Easingwood
Abstract
The advent of Coprin Multidose, Glaxo’s new copper injection for cattle, was
welcomed since it appeared that the undesirable features associated with many of its
competitors had been overcome. However in the month after its release onto the
market the first of a number of unexpected reactions was reported. This and
subsequent similar reactions were of a type hitherto unrecorded following copper
treatment of cattle in New Zealand. All reactions involved whole groups of young
cattle soon after treatment and resembled acute systemic hypersensitivity. Other
similar groups treated on the same properties and on the same day did not necessarily
react.
It was these reactions, which on occasion were serious enough to cause death, that
prompted this inquiry into their cause.
A review of copper deficiency as it occurs in New Zealand cattle and an account of
the various forms of copper poisoning which may occur served as a starting point for
the investigation.
Attention was then turned to the geographic distribution of the reactions and this
revealed that they had occurred predominantly in areas of high temperature and
rainfall rather than where Coprin Multidose had been most used.
Since these climatic conditions are conducive to lungworm infection it was postulated
that such infection may constitute a predisposing cause for the reactions. This was
supported by the knowledge that the lungs are the main organs involved in systemic
hypersensitivity reactions in cattle and that it is the release of certain substances from
the mast cells in the lungs which produce the clinical reaction. Furthermore it is
known that mast cell numbers in the lungs increase in response to lungworm invasion.
The next step was to determine if any of the components of Coprin Multidose were
capable of causing the degranulation of these cells with the consequential release of
the mediators of hypersensitivity reactions.
A study of the literature revealed that polyvinyl pyrrolidone, a long chain polymer of
high molecular weight, incorporated for the first time in any copper injection and
giving Coprin Multidose some of its desirable qualities, could cause hypersensitivity
reactions in some other species. It was also found that another similar polymer could
cause hypersensitivity reactions in cattle.
Experiments were performed, using both live cattle and isolated bovine tissues, in an
attempt to determine the component of Coprin Multidose responsible for the
reactions. These experiments proved to be inconclusive but nevertheless pointed the
way to further investigation.
Following a study of their pharmacological actions, a number of drugs are suggested
which could constitute a rational approach to the treatment of hypersensitivity-like
reactions in cattle.
Finally, the similarity between the clinical signs and autopsy findings in these
reactions are compared with those found in three other conditions. It is suggested that
they may all be due, at least in part, to an interference with the autonomic control
necessary to maintain bodily homeostasis and that copper itself may be a contributing
factor in the hypersensitivity-like reactions occasionally caused by Coprin Multidose.