Toxic effects of aflatoxin B1 in male Holstein calves with prior infection by flukes (Fasciola hepatica).

This experiment was designed to compare 3 dose levels of aflatoxin B1 (0.0, 0.5, and 1.0 mg/kg of body weight) and 2 infection levels of Fasciola hepatica metacercariae (0 and 220) to determine whether an additive effect from aflatoxin B1 occurs when fascioliasis is present in dairy calves. Twenty-four male, Holstein calves, 4 weeks old, and averaging 45.8 kg each, were assigned at random to 6 treatment groups, 4 calves per group: group 1--negative control; group 2--0.5 mg of aflatoxin B1/kg; group 3--1.0 mg of aflatoxin B1/kg group 4--220 metacercariae; group 5--220 metacercariae plus 0.5 mg of aflatoxin B1/kg; and group 6-220 metacercariae plus 1.0 mg of aflatoxin B1/kg. The single oral dose of 220 metacercariae was given (groups 4, 5, and 6) at the start of the 10-week experiment, and 5 weeks later, the single oral dose of aflatoxin B1 was given (groups 2, 3, 5, 6). Results from the principals, as compared with that from the controls (group 1), included significant decreases of dry matter intake (P less than 0.006), body weight (P less than 0.024), and serum albumin (P less than 0.04), and in groups 4, 5, and 6 infected with 220 flukes, there were significantly increased values of prothrombin time (P less than 0.014), serum alkaline phosphatase (P less than 0.04), and serum sorbitol dehydrogenase (P less than 0.007). Significant differences in number of flukes recovered from liver were seen in groups 4 to 6 given 0, 0.5, and 1.0 mg of aflatoxin B1/kg (P less than 0.046). The single oral dose of 22* fluke metacercariae in groups 4, 5, and 6 resulted in significantly increased concentrations of serum total protein (P less than 0.003) and globulins (P less than 0.01). Results from the development of the flukes from metacercariae to the mature state with sizes, numbers, feeding habits, and pathologic lesions were described. Differences in numbers of flukes recovered from liver of groups 4 to 6 and the presence of pneumonia in calves of group 6 indicated aflatoxin B1 produced persisting, lowered resistance. In all animals necropsied, the liver was the organ most affected by aflatoxin B1 as well as with flukes. Periportal fibrosis, monocytic infiltration, fatty infiltration, and bile duct proliferation were the usual lesions induced by aflatoxin B1. Additive toxic effects were observed in the groups 5 and 6 dosed with flukes and aflatoxin B1, with significant variations of serum and plasma values, as well as increased severity of histopathologic changes.