Flocoumafen, a new rodenticide for the control of rattus argentiventer.

Flocoumafen, a new anticoagulant rodenticide from Shell, was evaluated against Rattus argentiventer in the laboratory. Oral intubation studies were conducted, with doses ranging from 0.1-0.5 mg/kg using corn oil as carrier, against non-starved rats of both sexes. The volume introduced by gavage per rat was set within the limits of 0.5-1.5 ml governed by the desired dose and the weight of the rat. Groups of 10 males and 10 females were used for each dose. The median lethal doses (LD5o) of flocoumafen were 0.25 mg/kg for the males and 0.37 mg/kg for the females. There was significant difference between the sexes in the susceptible to flocoumafen. Feeding tests were conducted with flocoumafen under no-choice and choice conditions ad libitum. In no-choice feeding tests, the concentrations used were 0.0005 percent, 0.001 percent, 0.002 percent, 0.003 percent and 0.005 percent. Flocoumafen at 0.002 percent, 0.003 percent and 0.005 percent elicited 100 percent mortality in both sexes in one-day no-choice tests. The lowest lethal dose was 0.17 mg/kg and the highest dose survived was 0.34 mg/kg in males. In females, the lowest lethal dose was 0.21 mg/kg and the highest dose survived was 0.50 mg/kg. Mean days to death in rats succumbing to a lethal dose were 7.2 days (with a range of 4-14 days) in males and 7.9 days (range 4-14 days) in females. The median lethal feeding periods (LFP50) for 0.0005 percent flocoumafen were 1.43 days for males and 1.86 days for females. The corresponding LFP99 were 3.44 days and 5.00 days for males and females respectively. Males appeared more susceptible to flocoumafen in the no-choice feeding tests but there was no significant difference in the LFP 50 between the sexes. The relative potency ratio of flocoumafen in no-choice feeding tests with males as reference was 0.75. The feeding period/mortality data were pooled for analysis. The pooled LFP50 and LFP99 for 0.0005 percent flocoumafen against R. argentiventer were 1.63 days and 4.41 days respectively. Palatability studies (two-day choice feeding tests) indicated that flocoumafen at 0.005 percent was the most suitable concentration in baits for use against R. argentiven.