SUMMARY OF RODENTICIDES
Anticoagulants work by preventing the assimilation of vitamin K1, one of 12 ‘blood clotting factors’ within vertebrates. Once a lethal dose of poison has been eaten by the rodent, there is a lag period while the existing vitamin K1 in the body is used up. This normally takes three to four days, after which the blood will no longer be able to clot, and any haemorrhaging inside the body will lead to death. The great advantage of the lag period is that rodents never associate the bait they have eaten, with the symptoms of poisoning they go through. This means it is possible to attain 100% control of the population, as the rats will continue to feed on the bait ignorant of the fact it is killing them. ‘Sub-acute’ rodenticides containing Cholecalciferol (vitamin D3) offer a resistance breaking alternative to anticoagulant rodenticides. They also present a relatively low risk of secondary poisoning to non- target species. Once ingested the time taken to kill the target species can be similar to that of anticoagulants, but generally around three days. The ingestion of baits containing Cholecalciferol causes hypercalcemia which leads to the calcification of blood vessels and ultimately death from heart, kidney or multi-organ failure. ‘Acute’ poisons which work more quickly (within minutes of being eaten), have several disadvantages over anticoagulants. Firstly, if a sub-lethal dose is consumed, rats and mice may become ill but not die. Such illness is remembered and the rodents will avoid eating the bait again, compromising the control programme. Typically only 55-65% of the population will be killed when acute poisons are used. Active ingredients The most widely used anticoagulant active ingredients used in the UK as rodenticides are: • Difenacoum
• Bromadiolone • Brodifacoum
First generation
Second generation
Sub-acute
Acute rodenticides
Warfarin Coumatetralyl
Difenacoum Bromadiolone Difethialone Flocoumafen Brodifacoum
Cholecalciferol
Alphachloralose
Each has a different level of toxicity to mice, rats and non-target animals such as birds and dogs.
NON-TARGET TOXICITY - LD50 GRAMS OF BAIT PER KILO OF ANIMAL
RODENTICIDE
50 PPM Bromadiolone Baits
50 PPM Difenacoum Baits
50 PPM Brodifacoum Baits
50 PPM Flocoumafen Baits
250 PPM Warfarin Baits
750 PPM Cholecalciferol Baits
ANIMAL
RABBIT
20.0
40.0
5.8
14.0
3200.0
12
PIG
60.0
1600.0
10.0
4.0
4.0
DOG
200.0
200.0
5.0
1.5
80.0
13.4
CAT
500.0
2000.0
500.0
200.0
40.0
166.7
CHICKEN
1000.0 1000.0
200.0
4000.0
2000.0
60.0
SHEEP
DATA TAKEN FROM VARIOUS INDUSTRY REFERENCES
RODENT CONTROL | 17
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