Fenbendazole and Albendazole Toxicity in Pigeons and Doves

Presumptive Albendazole Toxicosis in 12 Alpacas

“…Similar sensitivity has been reported in columbiform birds. 4 In 36 pigeons and doves treated with albendazole, clinical, and postmortem changes were comparable with those observed in these alpacas, despite the birds being treated with a recommended avian dose of 50-100 mg/kg PO once daily for 2-9 days. Treated birds had leukopenia (o1,000 cells/mL), weight loss, and decreased survival compared with untreated animals.…”

“…Histopathologic findings included small intestinal crypt epithelial necrosis as well as bone marrow hypoplasia, suggesting that birds might be more susceptible to the antimicrotubule activity of the albendazole, with the drug essentially acting as a radiomimetic, leading to the death of rapidly dividing cells. 4 It was speculated that sensitivity in birds might be a result of increased intestinal absorption compared with mammalian species, 4 although the dose administered was also 2-10 times higher than that recommended for mammals. Toxicity as a result of albendazole's antitubulin action is consistent with the changes observed in these alpacas, with the most rapidly dividing cells apparently affected first, including neutrophils (lifespan 6-8 hours), enterocytes (lifespan 2-8 days), platelets (lifespan 7-9 days), and possibly cells of the hair follicle (lifespan variable).…”

“…Columbiform birds have similar, although less severe and consistent, lesions with fenbendazole administration. 4 Anecdotally, camelids are often treated with high doses of fenbendazole (50 mg/kg PO for 5 days) as therapy for Parelaphostrongylus tenuis infections without report of adverse effects. One study examining the pharmacokinetics of a 5 mg/kg dose of fenbendazole in llamas showed similar rates of absorption to that seen in other ruminant species, but a slower rate of clearance.…”

“…3 Although generally considered a safe class of drug, this interference with tubulin function is thought to be the mechanism behind the benzamidazoles' rare toxic effects on rapidly dividing cells including fetal, bone marrow, and intestinal cells. 3,4 Certain species such as columbiform birds (pigeons and doves) develop toxicosis with the administration of either albendazole or fenbendazole, exhibiting bone marrow hypoplasia and intestinal crypt epithelial necrosis, even at doses suggested for avian species (50-100 mg/kg PO once daily for 2-9 days). 4 Idiosyncratic intoxication in response to benzamidazole administration occurs in humans, dogs, cats, storks, porcupines, and swine at recommended dosages.…”

“…3,4 Certain species such as columbiform birds (pigeons and doves) develop toxicosis with the administration of either albendazole or fenbendazole, exhibiting bone marrow hypoplasia and intestinal crypt epithelial necrosis, even at doses suggested for avian species (50-100 mg/kg PO once daily for 2-9 days). 4 Idiosyncratic intoxication in response to benzamidazole administration occurs in humans, dogs, cats, storks, porcupines, and swine at recommended dosages. [5][6][7][8][9][10] Albendazole administration to humans causes clinical abnormalities including pancytopenia, neutropenia, and thrombocytopenia, occasionally resulting in death from sepsis secondary to severe neutropenia.…”