Page 1059 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Aflatoxins Chapter | 69 991

VetBooks.ir parameters. Thus, the expression of clinical signs and pattern may be either or both periportal and centrilobular,
while in the rabbit the pattern is reported to be midzonal
pathology can vary with each incidence and this may be
(Newberne et al., 1966a; Chaffee et al., 1969; Clark et al.,
due to exposure, under field conditions, to multiple myco-
toxins. Animals infected with aflatoxicosis can have con- 1980). Hyperplasia of the bile duct cells occurs rapidly in
current infectious diseases. The clinicopathology of ducklings and may be present in horses, dogs, and chick-
aflatoxicosis have been presented in more detail in the sec- ens, and mild bile duct cell hyperplasia may be seen in cat-
ond edition of Veterinary Toxicology: Basic and Clinical tle and pigs (Newberne and Butler, 1969; Ketterer et al.,
Principles (Coppock et al., 2012). 1975; Coppock et al., 1989). Multinucleated hepatocytes
have been observed in dogs, cattle, and other species.
Reactive fibroblasts have been observed in dogs. Humans
Macroscopic and Microscopic Pathology
infected with hepatitis B virus appear to be at greater risk
Edema and Hemorrhage for hepatic neoplasia when they are exposed to AFs.
Chronic liver injury and regenerative hyperplasia are con-
The pathology of aflatoxicosis has been described in several
sidered critical for the development of liver neoplasia.
species. Edema including anasarca and edema fluid in the
Dividing liver cells are more likely to form DNA adducts.
peritoneal and thoracic cavities can be observed (Osweiler
In sub-Saharan Africa, consumption of corn is associated
and Trampel, 1985; Bastianello et al., 1987; Coppock et al.,
with increased HIV and consumption of rice is associated
1989; Hall et al., 1989). The gall bladder, bile duct, aboma-
with increased liver cancer (Williams et al., 2010).
sal wall, and colonic mesentery may be edematous. There
may be edema of the omentum near the stomach or aboma-
sum and in the colonic mesentery. Gall bladder and perire- Other Lesions
nal edema may be marked in cattle and pigs. Edema of the
Renal lesions of protein in proximal tubules and glomeru-
brain has been reported for horses (Angsubhakorn et al.,
lar spaces are recorded in horses and rats (Butler, 1964;
1981). Hemorrhage into the gastrointestinal tract, into body
Newberne and Butler, 1969; Bortell et al., 1983).
cavities and on body organs has been reported. Hemorrhage
Hemosiderin deposition in tubule cells occurs in horses
is due to decreased production of clotting factors by the
(Angsubhakorn et al., 1981). Cardiac myofiber degenera-
liver. Acute aflatoxicosis in cattle, horses, pigs, and dogs
tion is recorded in horses and rats (Butler, 1964;
may result in serious hemorrhages in the gastrointestinal
Angsubhakorn et al., 1981). Brain lesions described as
tract, on serosal surfaces, on the epicardium and endocar-
focal malacia in the cerebral hemispheres in horses were
dium, in skeletal muscle, perirenal and in the urinary blad-
reported and for other species (Angsubhakorn et al.,
der (McKenzie et al., 1981; Bortell et al., 1983; Jakhar and
1981). Hepatic encephalopathy can occur because of liver
Sadana, 2004; Bruchim et al., 2012). Pigs can also have
damage. Subacute lesions observed at necropsy include
hemorrhage occurring in the pleural and peritoneal cavity.
firm, pale livers in all species and clear yellow ascites
Theurine maybedark red colored.
and pleural fluid accumulation especially in pigs and dogs
(Newberne and Butler, 1969). Icterus is usually present.
Hepatic Lesions Pneumonia is reported in calves as likely secondary to
Histopathology includes bile duct proliferation, hepatocyte edema and the effects of AF on the immune system.
necrosis, and early fibrosis of the liver (Newberne and Lesions of photosensitization have been reported in cattle.
Butler, 1969). Regeneration of hepatocytes may be found
in dogs, and nodular hyperplasia may be present in turkeys,
trout, and ducklings (Newberne et al., 1966b; Newberne Differential Diagnosis
and Butler, 1969; Bastianello et al., 1987). Variation in the The lesions of aflatoxicosis and those of pyrrolizidine
size of hepatocytes, with some megalocytes and binucleate alkaloid toxicosis have been observed to be very similar
cells, is recorded in many reports. Chronic liver lesions are especially in cattle (Loosmore and Markson, 1961). Cattle
characterized by firm, fibrous pale livers, by nodular are generally considered to be more susceptible to pyrroli-
hyperplasia, and in some cases, neoplasia. Icterus is pres- zidine alkaloids. When AFs and pyrrolizidine alkaloid are
ent. The liver may be swollen, friable, and congested. at issue, it is important to examine pasture, forage, con-
Histologically, the liver may have necrosis in variable pat- centrate feeds, and gastrointestinal contents to determine
terns. In the rat, monkey, and duckling, the necrosis is the presence of poisonous plants that may contain pyrroli-
reported to be periportal, while in cattle, pigs, horses, zidine alkaloids. In some geographic areas seeds contain-
goats, and sheep, the pattern is recorded to be centrilobular ing pyrrolizidine alkaloids can be present in grain
(Butler, 1964; Newberne et al., 1966a; Samarajeewa et al., screenings, and their identity lost in the grinding and pel-
1975; Carlton and Szczech, 1978; Abdelsalam et al., 1989; leting processes. Finished feeds and screenings can be
Coppock et al., 1989; Mathur et al., 1991). In the dog the assayed for pyrrolizidine alkaloids.