Page 1057 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

Aflatoxins Chapter | 69 989

VetBooks.ir reported. Young birds require longer to clear AFB 1 from increased occurrences and severity of common infectious
disease. Recovery from infectious disease may be pro-
tissues. Laying hens (Hy-Line Brown) were feed a diet
longed and require additional treatments. A clue to immune
for 6 weeks containing peanut meal naturally contami-
nated with AFs (Jia et al., 2016). The mixed diets aver- dysfunction can be infections caused by organisms that are
aged 89.5, 20.2, 9.6, and 3.7 mg/kg of AFB 1 , AFB 2 , not generally considered to be hard hitting pathogens.
AFG 1 , and AFG 2 , respectively. The average egg weighed Studies have shown that the immunotoxicity of AFs could
39.9 g and the mean AFB 1 , AFB 2 , and AFM 1 were 0.02, be a teratogenic effect of prenatal or pre-hatching exposure
0.11 and 0.02 μg/kg of egg, respectively. No AFG 1 and to AFs. As a general summary, AFB 1 lowers lymphoid cell
AFG 2 were identified in the eggs. populations especially circulating activated lymphocytes,
The translocation of AFs into edible tissues of pigs has suppresses lymphoblastogenesis and decreases both cutane-
been studied. Jacobson et al. (1978) fed feeder pigs ous delayed-type hypersensitivity, and graft versus host
(54 72 kg body mass) diets containing pure AFB 1 at 100, reaction and suppresses innate immunity. AFB 1 reduces
natural killer cytolysis and macrophage functions including
200, and 400 ppb. The basal diet contained 0.1 ppb AFB 1
and 0.1 ppb AFB 2 . These diets were fed for 4 weeks. Liver, phagocytic activity and production of oxidative radicals.
kidney, and skeletal muscle contained levels of AFB 1 that AFB 1 alters genetic expression of immune responses of
were correlated with the feeding level. In decreasing dietary innate and acquired immunity. A brief literature review is
level, AFB 1 levels in liver were 1.5, B0.5, and B0.2 ppb; provided for the immunotoxic effects of AFs in different
levels in skeletal muscle were B1, B0.5 and B0.2 ppm; species. The immunotoxic effects of AFs have been studied
and levels in kidney were 4.4, B0.7, and B0.2 ppb. in pigs. Treatment with AFB 1 has been shown to shorten
Steers were fed rations containing 0, 60, 300, and the incubation period of Serpulina (Treponema) hyodysen-
teriae in pigs (Joens et al., 1981). Pigs given AFB 1 and
600 ppb AFB 1 (Helferich et al., 1986). FB 1 and AFM 1
were detected in the liver in the animal receiving the 300 infected with S. hyodysenteriae also had a longer period of
and 600 ppb AFB 1 and these residues cleared in 7 days. diarrhea. Feeding weanling piglets a diet containing 140 or
280 ppb AFs (B70% AFB 1 ) for 4 weeks caused an
increase in serum γ-globulin (Marin et al., 2002). At the
TOXICODYNAMICS 280 ppb level, a reduced immune response to vaccination
Mechanisms of Action for Mycoplasma agalactiae was observed. There were indi-
cations that expression of interleukin-1β and tissue necrosis
The metabolism of AFs is linked with toxication (Eaton factor-α was decreased by exposure at the 280 ppb level.
and Gallagher, 1994). AFB 1 is metabolized in a CYP- The white blood cell numbers responded by a decrease at
dependent reaction to AFB 1 -8,9-epoxide that forms the 140 ppb level and increased at the 280 ppb level. Sows
adducts with macromolecules in the cell. The affinity of were fed diets containing 800 ppb AFB 1 or a diet contain-
AFB 1 -8,9-epoxide in decreasing order for macromole- ing 400 ppb AFB 1 1 400 ppb AFG 1 for the entire gestation
cules is DNA . RNA . protein. The DNA adduct is and lactation period (Silvotti et al., 1997). At 25 days of
7
formed with N -guanine and this adduct is relatively age the piglets born to the sows were found to have
resistant to DNA repair processes. Upregulation of the decreased immune functions in lymphoproliferative
CYP system increases the toxicity of AFs. AFB 1 alters response to mitogens, monocyte-derived macrophages
genetic expression in the immune system, liver and likely failed to have induced oxygen bursts and granulocytes had
all organ systems in the body. Species sensitivity to AFs reduced chemotactic response. AFs have been shown to be
is linked to the rate of bioactivation and the rate of detox- immunotoxic in ruminants. Feeding a diet containing
ification. AFB 1 -8,9-epoxide is primarily detoxified in 2ppm AFs (83.4% AFB 1 , 12.3% AFB 2 and AFG 1 and
Phase II synthetic reactions by GSH. In mammals, gluta- AFG 2 ) to lambs for 37 days increased serum γ-globulin,
thione S-transferase mediated conjugation is an important decreased bacteriostatic activity in serum and decreased
detoxification pathway, and species differences in enzyme cellular immunity (Fernandez et al., 2000). AF inhibits thy-
activity in part account for differences in species suscepti- midine uptake by phytohemagglutinin-stimulated lympho-
bility. Other Phase II pathways that decrease the toxicity cytes. Holstein steers (183 kg), fed a diet containing
of AFs include formation of glucuronide and sulfates. B375 ppb AF for 17.5 weeks, were observed to have a
decrease in delayed cutaneous hypersensitivity (Richard
et al., 1983). Changes were not observed in antibody pro-
Immunotoxic Effects
duction (Brucella abortus antigen) and lymphoblastogen-
AFs are immunotoxic and reduce the native resistance to esis. AFs reduce the native resistance of the mammary
disease and vaccine protection is also impaired. The appar- gland to disease. The immunotoxic effects of AFs on
ent clinical signs of aflatoxicosis may be limited to native resistance of poultry to infectious diseases have