Duck Deaths from Accidental Ingestion of Anthelmintic

DDVP (2,2-dichlorovinyl dimethyl phosphate) is an organophosphate, anticholinesterase compound used widely as an insecticide (1). It is also prescribed as an anthelmintic for farm animals, including horses (Equigard 3, Shell Chemical Company). DDVP has an acute oral LD5o (dose required to kill 50% of the test population) of 62 mg/kg in adult male rats (1) and 7.78 mg/kg in 5-to7-month-old mallard drakes (4). In June 1975, eight adult mallards (Anas platyrhynchos) were found dead less than 1 hour after they were noticed feeding near horse mangers containing DDVP-treated feed. The dead mallards were collected and sent to Patuxent Wildlife Research Center for necropsy and chemical analysis. Necropsy findings indicated that the birds had been in good condition and had good deposits of fat. Excessive amounts of mucus covered the mucosa of the proventriculus, and scattered petechiae were present along medial edges of liver lobes. The small and large intestines were markedly distended, and in 2-to-3-cm alternate sections were yellowish and greenish-brown or red. Bacteriological cultures of livers were negative. Crystals resembling those obtained from a packet of Equigard 3 and grain were noted in the gizzard. Heads of birds were removed and saved for analysis of brain cholinesterase activity.