Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

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Chapter | 27 Clinical Biochemistry in Toxicology
Cardiac glycosides disrupt cardiac ion channels producing
sudden dysrhythmias and often death ( Cheville, 1988 ).
Plants containing cardiac glycosides include Bryophyllum
tubiflorum, Digitalis spp. (foxglove), Homeria spp. (cape
tulip), Nerium oleander (oleander), Thevetia peruviana
(yellow oleander), and Tylecodon spp. ( Robinson and Maxie,
1993 ). Most intoxications occur in herbivores, although the
cat is reported to have increased CK levels after ingestion of
Easter lily plant. ( Rumbeiha et al. , 2005 ) . Amphibians producing
cardiac glycosides include Bufo alvarius, B. marinus,
and Dendrobates spp. (poison dart frog). Most intoxications
occur in cats and dogs that become curious about these animals.
Neurological signs may be the presenting complaint
in intoxication from B. marinus (Roberts et al. , 2000 ).
Fluoroacetate containing plants include Acacia georginae,
Dichapetalum cymosum, Gastrolobium spp., and
Oxylobium spp. Fluoroacetate (compound 1080) also has
been utilized as a rodenticide. It is not directly toxic, but
combines with oxaloacetic acid to form fluorocitrate that
inhibits cis -aconitase and succinic dehydrogenase of the
citric acid cycle thus reducing ATP generation. Animals
intoxicated with fluoracetate are reported to have hyperglycemia
and hypocalcemia, along with increased serum
citrate levels ( Parton, 2003 ).
Glycosides and fluoroacetate may produce sudden
death that precedes alterations of clinical chemistry or morphological
changes. Hypercalcemia may induce cardiac
calcinosis and nephrotoxicity as discussed earlier.
Hyperkalemia from myotoxicity (especially gossypol)
( Albrecht et al. , 1969 ) , nephrotoxicity, or adrenal necrosis
(hypoaldosteronism) may exert a dysrhythmogenic (Q-T
prolongation and high amplitude T waves) effect on the
heart. Potassium chloride injection also has been used for
lethal poisoning by individuals attempting to circumvent
detection by insurance adjusters ( Casteel et al. , 1989 ).
Cardiotoxic metals include lithium, cadmium, nickel,
barium, lanthanum, manganese, vanadium, lead, and cobalt
( Van Vleet and Ferrans, 1986 ). Iron-dextran toxicity in pigs
may produce necrosis of skeletal muscle and hyperkalemia,
sparing the myocardium ( Kelly, 1993 ).
Quinolizidine alkaloids in Lupinus spp., Laburnum
anagyroides, and Thermopsis montana have been shown to
produce skeletal muscle necrosis in cattle with elevations
of serum CK and AST in the absence of myoglobinuria
( Keeler and Baker, 1990 ). Quinolizidine alkaloids are also
teratogenic.
Elevations in serum creatine kinase have been reported
in association with viper envenomation in dogs ( Aroch
et al. , 2004 ) .
The numerous chemotherapeutic agents that have been
associated with cardiotoxicity have been reviewed elsewhere
( Van Vleet and Ferrans, 1986 ).
Cardiotoxins may produce serum enzyme elevations
suggestive of hepatic or renal disease secondary to
ischemia/hypoxia.
V . TOXINS AFFECTING THE LUNG AND
RESPIRATORY TRACT
Disease affecting the respiratory tract is often clinically
apparent on the basis of dyspnea. Dyspnea in veterinary
medicine is more often the result of pneumonia rather than
intoxication. However, when body temperature is normal,
the possibility of pulmonary edema induced by toxins
affecting the lung and respiratory tract ( Table 27-4 ) or cardiovascular
system should be considered. Because, with the
exception of the horse, domestic mammals remove excess
heat by panting, reduced respiratory capacity secondary to
intoxication also may result in elevated body temperature.
TABLE 27-4 Toxins Affecting the Lung and Respiratory Tract
Toxins Disease Onset Geography Species Affected
Eupatorium adenophorum Chronic AUS E
Fumonisin (Fusarium moniliforme) Acute to chronic Worldwide P
4-ipomeanol ( Fusarium solanii) Acute Worldwide B
Kerosene/Petroleum Acute Worldwide All
3-methylindole Acute Worldwide B
Myoporaceae Acute AUS, NZ B, O
Organobromines/organochlorines Chronic Worldwide All
O 2 Acute to chronic Worldwide All
Paraquat Acute to chronic Worldwide All
Perilla frutescens Acute US B, E, O
Pyrrolizidine alkaloids Chronic Worldwide B, Cp, E, O, P
Abbreviations: B, bovine; Cn, canine; Cp, caprine; E, equine; F, feline; O, ovine; P, porcine.