Page 265 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

232 SECTION | II Organ Toxicity

VetBooks.ir 1 g/kg b.w. will kill sheep and 230 g will kill a horse or cat- warmer climates. An economically important member of
the family is Coffea arabica, the source of coffee beans.
tle. Due to its severe toxicity in cattle, it is also called
Alkaloids derived from the bark of Cinchona yield qui-
“cowbane.”
Cardiovascular effects include alterations in blood pres- nine; others are antihypertensive and antiinflammatory.
sure, heart rate, a widening of the PR interval on the ECG, Gardenia (Gardenia jasminoides) is a garden plant of the
supraventricular tachycardia, and ventricular fibrillation frost-free zones planted worldwide.
(Schep et al., 2009). Degeneration and fibrosis in the heart On the other hand, 4 6weeksafter ingestionof
is observed, and the blood serum shows increases in aspar- plants of the Rubiaceae family (Kellerman, 2005), rumi-
tate aminotransferase (AST) and lactic dehydrogenase nants, without forewarning, drop dead with heart failure.
(LDH), enzymes released upon injury to the heart or liver. Called gousiekte (Afrikaans name meaning quick sick-
Treatment, though difficult and usually not in time ness), the disease affects sheep and cattle and is charac-
due to the rapidity of the poisoning, includes intravenous terized by myocardial necrosis consisting of a loss of
administration of sodium pentobarbital to control seizure. myofilaments, cardiac dilations, and replacement of
Eupatorium rugosum spp. (White Snakeroot) is a mem- myocytes with collagenous tissue. In the terminal phase
ber of the daisy family native to the eastern United States of the disease, the heart has a rounded, flabby appear-
(Kingsbury, 1964). It is an erect plant that is up to 1.5 m tall ance without an apex and has attenuated papillary mus-
with the leaves resembling those of the nettle. Consumption cles. In the subendocardial region of the apex and the
of plants at 0.5% 2.0% b.w. causes poisoning in livestock left ventricular wall, the principal lesions are degenera-
(Doyle and Walkey, 1949). The plants are poisonous to tion of myofibers.
horses, goats, and sheep. White snakeroot contains the toxin The toxic principle is pavetamine from Pavetta har-
tremetol. Tremetol passes through the milk in cows, and borii which inhibits myocardial protein synthesis with-
thus contaminated milk causes sickness in suckling calves out affecting myocardial fibers or other organs. The
and humans. It is important to mention that tremetol is disease is characterized by cellular injury and is not a
cumulative in that repeated exposure leads to intoxication. specific heart disease and terminates in dilated cardio-
The onset of clinical signs begins 2 3 weeks postin- myopathy and congestive heart failure (Hay et al., 2008;
gestion. In horses, it causes congestive heart failure Prozesky, 2008). Sheep dosed daily at 25 mg/kg b.w.
(Maratea, 2003). The enzymes CK, alkaline phosphatase after 4 weeks showed typical signs of cardiac failure
(ALP), and AST are elevated, and cardiac muscle degen- with galloping heart rhythm, decrease of ejection frac-
eration occurs. Pale linear streaks in the myocardium as tion of the left ventricle (from 60% to 30%), and
well as fluid in the pericardial sac have been observed. In decrease in the pumping efficiency of the left ventricle
horses, swelling in the neck area is also noted. Rapid with respect to the right ventricle (van der Walt and van
heart rate, elevation of ST, and variable QRS complexes Rooyen, 1977). Goats fed pavetamine showed ECG
in the ECG and cardiac arrhythmias may be present. changes and tachycardia. The electrophysiology of the
Treatment consists of supportive care. pacemaker cells was affected. In sheep T-wave inversion
Astragalus spp. (Locoweed) is found throughout the was common as was hypokalemia. In addition, calcium
western United States and Canada. This perennial plant abnormalities were noted.
contains the toxic principle indolizidine alkaloid swainso-
nine (Turner et al., 2012). Animals grazing on Locoweed OXALATE-CONTAINING PLANTS
develop lysosomal storage disease when the lysosomal
enzyme alpha mannosidase is inhibited. A toxic content Many oxalate-containing plants, such as Philodendron
of Locoweed greater than 0.001% can cause poisoning. (Philodendron bipinnatifidum), are kept for their orna-
Cytoplasmic vacuolation of cells of the CNS occurs. It mental beauty and are often easily accessible to pets. If
increases the severity of “high mountain disease,” a ingested in large quantities, it cannot be metabolized, and
hypoxia-induced pulmonary hypertension and hypertrophy the salts are absorbed into the bloodstream. Oxalic acid
of the right ventricle of animals living at elevated altitudes. combines with calcium and forms the crystals. Although
Sheep, cattle, and horses are affected. Some of the these crystals are primarily deposited in the kidneys, they
Astragalus species also accumulate large amounts of sele- can also be deposited in other organs, including the heart.
nium complicating the effect on the heart when ingested. In humans, oxalosis can lead to cardiac abnormalities cor-
Pathological effects include neurological damage and related with decline in renal function (Mookadam et al.,
congestive right-heart failure. Treatment includes fluid 2010). Oxalosis also causes heart block (Coltart and
therapy with potassium supplementation, dopamine, and Hudson, 1971). Sheep and cattle grazing on Rumex cris-
diazepam. pus (Curled Dock), native to Europe and Western Asia,
Rubiaceae spp. (Madder) is the fifth-largest flowering experienced tetany, recumbency, and death. Some grass
plant family spread worldwide but found mostly in the varieties, including Buffelgrass (Pennisetum ciliare),