Page 387 - The Veterinary Laboratory and Field Manual 3rd Edition

356 Susan C. Cork, Willy Schauwers and Roy Halliwell

wildlife is less susceptible than domestic spe- something unusual. Heavy metals, although they
cies, to these natural toxins because of two are naturally occurring elements in the earth’s
main factors; they have evolved to avoid eating crust, generally cause toxicity only after we have
things that make them sick, and because they concentrated them through industrial practices
can move to other food sources if they detect that contaminate water or landscapes, or, added
them to products that animals can eat. Vitamin/
mineral mixes are not an uncommon source of
toxicity in livestock. Many pesticides that we
have developed to improve food production
for humans or animals, like organochlorines,
organophosphates and carbamates, and more
recently neonicotinoids (imidacloprid being the
principal example), have a broad range of toxicity
to vertebrate and non-target invertebrate species,
as well as the targeted invertebrate pests. The
neonicotinoids deserve special attention being
the fastest growing class of pesticides worldwide
(Morrissey et al., 2015). They are persistent,
have high potential for run-off and leaching, and
are highly toxic to a wide range of invertebrates,
notably beneficial ones such as pollinators.
Organophosphates are among the most widely
used insecticides in the world and are respon-
sible for much of the poisoning of wildlife, with
birds being most severely affected (Smits and
Naidoo, 2018). There is a diagnostic method
available that can be carried out in diagnostic
laboratories with modest facilities (Figure 7.14).
Medicinal products and food additives such
as mineral mixture supplements, are meant
to improve the health of animals and people.
However, overdoses or poor mixing, or carcass
residues can cause large scale toxicity problems
to entire herds or wildlife populations (Jones,
2001; Kart and Bilgili, 2008; Naidoo et al., 2010;
Smits and Naidoo, 2018). Plants may be toxic in
small amounts, for example, yew (Burcham et
al., 2012), or may require long term ingestion
Figure 7.14 (a) Organophosphate or carbamate (for example, bracken fern, acorns or leaves from
poisoning can be diagnosed from a serum sample oak trees and star thistle) (Welch et al., 2012)
of the patient using basic laboratory supplies and before clinical signs will be seen. Heavy metals
reagents, (b) glass slides with positive and nega- such as lead, mercury and cadmium may cause
tive serum samples are shown in the insert. See clinical signs in a group of animals or an individ-
also Plate 33. ual depending on the source of poisoning. Cattle,

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