Fox control using a para-aminopropiophenone formulation with the M-44 ejector
The M-44 ejector ('ejector') has proven to be a highly target-specific means of delivering toxicants to the exotic European red fox (Vulpes vulpes) in south-eastern Australia. Para-aminopropiophenone (PAPP) is a potent methaemoglobin (MetHb) forming compound in canids. A formulation
of PAPP, dimethylsulphoxide (DMSO) and condensed milk was investigated as a new toxicant formulation for delivery by the ejector. Dosage of eight foxes in the laboratory with a sequential dose demonstrated that the formulation caused a dose-dependent and rapid elevation of MetHb. A strong
inverse correlation between MetHb and oxyhaemoglobin concentrations was detected in each case. The symptoms of the toxicosis in the laboratory included progressive cyanosis, lethargy and then collapse when MetHb levels reached 56–76%. A polynomial model was a good fit for describing
the relationship between sub-lethal doses of PAPP and the resulting peak MetHb levels. In a pen trial, an ejector was fitted with a bait and loaded with a standard dose of 226 mg PAPP in the same formulation and set at one end of a pen. After voluntarily triggering the ejector, all five foxes
in this trial became progressively more lethargic and either lay prostrate or collapsed after 14–25 min, and death was confirmed after a mean of 43 min. We compared some clinical features of PAPP toxicosis with 15 cases of lethal sodium fluoroacetate (1080) poisoning using 0.5 mg kg−1
1080. PAPP produced a mean time to death that was 7.7 times faster than 1080, with the onset of first symptoms being 15 times faster. It was associated with much less activity prior to death and convulsions, spasms and paddling commonly associated with 1080 poisoning after collapse were not
detected during PAPP toxicosis. We conclude that the PAPP formulation appears to be a rapidly acting and apparently humane lethal agent for fox control when used in conjunction with the ejector.