5 Bait intake in mice
In the report published by the Norwegian Veterinary Institute (6), a calculation was made on possible intake of AC in mice to assess the possibility of secondary poisoning in cats and dogs. It was suggested that the mice (about 20 g body weight) ingest at least 1 g of bait before they die, possibly up to 2 g. One gram of bait contains 40 mg AC. A mouse that has ingested 40 mg AC, would give a 3 kg cat an oral dose of 13 mg/kg. If a cat ingests 4 mice, this will result in an oral dose of 50 mg/kg cat. These figures were considered conservative: If the mice ingested 2 g of the bait, the doses would double.
In the later study by Windahl et al. (1), bait intake and amount of AC of the formulation Trinol dry "No mouse korn" consumed by wild mice was studied. The mice were observed individually during an extermination of a rodent infestation. The calculated amount of AC ingested by each mouse was 33 to 106 mg with a mean of 61 mg (table 2). Thus, the real intake of bait in wild mice corresponded well with the doses calculated by Bernhoft et al. (6) The amount of ingested bait related to body weight varied from 3.9 to 13.7%, with a mean of 8.4%. A 3-kg cat that ingests a mouse containing the mean amount of bait with 61 mg AC, would result in a dose of 20 mg/kg cat, and four of such mice would give 80 mg/kg cat. If the 3-kg cat ingests a single mouse with the maximum amount of bait, 106 mg AC, the dose would be 35 mg/kg cat.
Table 2: Amount of consumed rodenticide bait Trinol No mouse korn® alpha-chloralose 40 mg/g in 14 wild mice (Apodemus flavicollis; Yellow-necked fieldmouse) caught in mousetraps, and calculated intake of AC for each mouse (1)
Mouse ID (number) | Body weight (g) after death | Bait placed in mousetrap (g) | Bait left in trap (g) | Bait consumed by mouse (g) | Bait consumed: Mouse body weight (%) | AC consumed (mg/mouse) |
|---|---|---|---|---|---|---|
1 | 16.2 | 2.02 | 0 | 2.02 | 12.5 | 80.8 |
2 | 15.8 | 2.04 | 0 | 2.04 | 12.9 | 81.6 |
3 | 22.5 | 1.81 | 0 | 1.81 | 8.0 | 72.4 |
4 | 16.8 | 10.24 | 8.01 | 2.23 | 13.3 | 89.2 |
5 | 20.8 | 10.47 | 9.65 | 0.82 | 3.9 | 32.8 |
6 | 23.1 | 10.18 | 8.90 | 1.29 | 5.6 | 51.6 |
7 | 14.5 | 10.04 | 9.14 | 0.90 | 6.2 | 36.0 |
8 | 15.5 | 2.13 | 0 | 2.13 | 13.7 | 85.2 |
9 | 18.3 | 1.98 | 1.12 | 0.86 | 4.7 | 34.4 |
10 | 15.1 | 2.34 | 1.19 | 1.15 | 7.6 | 46.0 |
11 | 21.6 | 10.14 | 7.50 | 2.64 | 12.2 | 105.6 |
12 | 24.0 | 10.09 | 8.51 | 1.58 | 6.6 | 63.2 |
13 | 21.8 | 10.03 | 9.16 | 0.88 | 4.0 | 35.2 |
14 | 12.3 | 9.80 | 8.93 | 0.86 | 7.0 | 34.4 |
Mean | 17.7 | - | - | 1.51 | 8.4 | 60.6 |
In an unpublished study by NVI, the intake of AC (Rodicum Express-green bait, 40 mg/g alpha-chloralose) was qualitatively studied by photo of the stomach in six mice. The stomach was filled with green coloured AC-bait (fig 5). All six mice in the study had similar findings.
Figure 5: The picture shows a mouse with its stomach filled with the green bait formulation "Rodicum Express" containing alpha-chloralose 40 mg/g. Photo: Christin Plassen, NVI.