Rodenticide
Rodenticides ( lat. Rodent rodents and caedere kill) are chemical agents for combating of rodents . They are used for the production of feeding bait and for the fumigation of storage rooms and underground rodent tunnels.
Active ingredients
Vitamin K antagonists
Anticoagulants from the group of vitamin K antagonists inhibit blood clotting . These active ingredients are also known as coumarins . A distinction is made between active ingredients of the first generation (FGAR) and active ingredients of the second generation (SGAR). Second generation active ingredients are more toxic and more difficult to biodegrade than first generation active ingredients.
warning
All information on anticoagulation in this article relates to the ready-to-use preparations. Pure or technical anticoagulants are very toxic (T +).
General
Food bait next to which dead rats lie are generally no longer accepted by conspecifics. Anticoagulants are suitable for use as rodenticides because they have only a relatively low acute toxicity for humans in the feeding bait . The common coumarins are classified as ready-made bait only as harmful (Xn), unlike many other rodenticides as toxic (T) or very toxic (T +). Coumarins are often combined with sulfonamides such as sulfachinoxaline as enhancers that inhibit the body's own vitamin K synthesis.
EU authorities are now very critical of anticoagulants as rodenticides, as either resistance or environmentally hazardous properties such as persistence or bioaccumulation have been demonstrated. These substances are therefore potential environmental chemicals . In addition, due to bleeding, anticoagulants can cause severe animal suffering lasting several days.
It was also found that not only the target organisms (rodents) are killed by the active ingredients, but also predators such as owls, buzzards, golden eagles, foxes and polecats are affected. However, seed and grain-eating birds can also be affected, as they eat the bait, which is often made of grain, directly.
Conventional rodenticides are no longer allowed to be sold in retail stores since January 1, 2013. Since then, it has only been sold through specialist dealers, and only qualified persons are allowed to use it (proof of competence required). In addition, the predicted environmental concentration (PEC) is usually far above the predicted concentration without any effect on environmental organisms ( PNEC ), so that these substances would actually no longer be eligible for approval in the EC. The mere lack of substitute substances leads to a temporary approval taking into account risk reduction measures.
effect
Both when used as a medicament and as a rodenticide, the fact that 4-hydroxycoumarins are structurally similar to vitamin K is exploited . This vitamin is needed in the liver for the synthesis of various coagulation factors such as prothrombin , factor VII and factor IX .
Instead of vitamin K, the coumarins attach themselves to the respective enzyme , block it and stop the formation of the relevant factors through competitive inhibition . Due to the changed structure of the coagulation factors, the calcium, which is indispensable for coagulation, can no longer be bound to the factors, which is why the factors themselves can no longer bind to the wound surfaces. The effect ( liver damage , bleeding to death ) therefore only occurs after the coagulation factors circulating in the blood at the time the anticoagulant agent is administered have been partially used up. This is only the case after approx. 6 hours. The maximum effect is reached after 36 to 48 hours. Due to the delayed onset of action, rodenticides are among the most effective control agents.
The behavior, which has been mentioned since around 1954, that rats would supposedly send out a taster with every new food offer to test the food for tolerance is a misinterpretation of the natural social and eating behavior of rats. Rats show very complex behavior when eating, for example to avoid food phobias that could prevent or limit the development of new food reserves. So far unknown food - there is little highly toxic food in nature, but potentially nutritious material that is occasionally bacterial, viral or otherwise contaminated - is often eaten first by curious and inexperienced young animals and is in most cases harmless and without negative effects Consequences for the animal. But rats generally perceive each other as social animals, also during and after the eating behavior, and wellbeing, or unusual behavior, or in extreme cases death - possibly associated with a certain smell, is accordingly registered either positively (reinforcing) or negatively (warning) , which is why rat poisons were developed in such a way that their deadly effect only manifests itself long after ingestion (time-delayed effect, second generation rodenticides).
Warfarin and coumatetralyl
Warfarin and Coumatetralyl are first generation rodenticides. In the late 1970s and early 1980s, rodents developed some resistance to warfarin. In the meantime, the active ingredient could be used again, but in March 2007 a renewed resistance was found.
Warfarin is a coumarin derivative and has a structural similarity to vitamin K. Like all therapeutically used coumarin derivatives, it belongs to the group of indirectly acting anticoagulants (coagulants). These do not intervene directly in the coagulation process, but indirectly. When rodents eat bait prepared with warfarin, they perish a few days later on even the smallest wounds, as the warfarin prevents coagulation.
Symptoms after ingestion of warfarin are
- Bleeding in the urinary tract or gastrointestinal tract
- intracranial ( Latin for: 'in the skull') bleeding
- Damage to embryos.
Depending on the amount of warfarin ingested, death occurs after a while. The common antidote of warfarin is vitamin K .
Bromadiolone
Chemical name: 3- [3- (4'-Brombiphenyl-4-yl) -3-hydroxy-1-phenylpropyl] -4-hydroxycoumarin.
Bromadiolone is a second generation anticoagulant and is mainly used as a feeding bait in municipal and agricultural rat control.
Safety, health and environmental protection (SHE)
It is absorbed orally, through the skin or by breathing. As with warfarin, a teratogenic effect is to be assumed after prolonged intake by pregnant women. The route of absorption through the skin must also be taken into account. Long-term studies are not available. As a pure or technical substance, bromadiolone is toxic to aquatic organisms. Predatory animals are at risk from secondary poisoning if they feed primarily on poisoned animals.
Difenacoum
Chemical name: 3- (3-Biphenyl-4-yl-1,2,3,4-tetrahydro-1-naphthyl) -4-hydroxycoumarin.
Difenacoum is a second generation anticoagulant. It is used against mice and rats.
Safety, health and environmental protection (SHE)
It is absorbed orally, through the skin or by breathing. As with warfarin, a teratogenic effect is to be assumed after prolonged intake by pregnant women. The route of absorption through the skin must also be taken into account. Long-term studies are not available. Difenacoum is practically insoluble in water. Effects on aquatic organisms have not yet been published. Predatory animals are at risk from secondary poisoning if they feed primarily on poisoned animals.
Brodifacoum
Chemical name: 3- [3- (4'-Brombiphenyl-4-yl) -1,2,3,4-tetrahydro-1-naphthyl] -4-hydroxycoumarin
Brodifacoum is a second generation anticoagulant. This rodenticide is only suitable for indoor use. Poisoned animals must not be allowed outside.
Safety, health and environmental protection (SHE)
It is mainly absorbed orally or through the skin. A teratogenic effect can be assumed. The route of absorption through the skin must also be taken into account. Long-term studies are not available. Brodifacoum is practically insoluble in water. The substance itself is highly toxic to aquatic organisms. Predatory animals (birds and mammals) are at great risk from secondary poisoning. They can die as a result of consuming a single poisoned rodent. The active ingredient may therefore only be used in closed rooms.
Flocoumafen
Chemical name: 4-Hydroxy-3- [3- (4'-trifluoromethylbenzyloxyphenyl) -1,2,3,4-tetrahydro-1-naphthyl] coumarin.
Flocoumafen is an active ingredient of the second generation and is mainly used in domestic rat control as well as in hygienic areas (sewers, landfills, sewage treatment plants). It is highly effective and works after just one shot. Flocoumafen is eaten by the rats in the form of bait presented to the rodents in bait boxes. The effect is delayed after 4–7 days. Flocoumafen inhibits blood clotting (anticoagulant). The common antidote is vitamin K1 , PPSB .
Safety, health and environmental protection (SHE)
It is taken orally. To avoid secondary poisoning, rats and mice that are already dead should be disposed of. Flocoumafen is environmentally hazardous. Toxicity: LD 50 rat oral 0.25-0.56 mg / kg
Difethialone
Chemical name: 3- [3- (4'-Bromo-biphenyl-4-yl) -1,2,3,4-tetrahydro-naphth-1-yl] -4-hydroxy-thiochromen-2-one.
Difethialon is a second generation anticoagulant. Mainly for combating mice and rats indoors as well as in warehouses and stables. Poisoned animals must not be allowed outside. Resistance to this coumarin derivative has not yet become known. Used in bait form against mice and rats and, in contrast to most other anticoagulants, works after a single intake. It is very toxic for humans (labeling T +, LD 50 / rat / oral: 0.59 mg / kg), as well as for most higher animal species. Secondary poisoning of domestic and wild animals is possible when eating dead rodents. In the event of accidental ingestion, therapy with vitamin K supplements must be carried out under medical supervision. Beilstein Registry Number: 8398136.
Antidotes to anticoagulants of the coumarin derivatives group
In the event of poisoning with coumarins, vitamin K must be given immediately as an antidote . The effect of vitamin administration is based on the displacement of the coumarins by the enzymes that form the coagulation factors. Here, too, there is a delay in the effect, since the missing coagulation factors can only be gradually replaced by the liver. Long-term therapy with vitamin K is necessary, especially in the event of poisoning by Brodifacoum. In an emergency, the missing coagulation factors can be replaced directly.
Other anticoagulants
1,3-indandione
Diphacinone and chlorophacinone
Diphacinone and chlorophacinone are active ingredients derived from 1,3-indanedione that are very effective at inhibiting blood clotting in mammals. It is one of the second generation anticoagulants.
Safety, health and environmental protection (SHE)
The pure active ingredient is highly toxic to humans. It is therefore rated T +. A teratogenic effect has not yet been investigated, but it can be assumed. The route of absorption through the skin must also be taken into account. The active ingredient is also highly toxic to pets, wild animals and aquatic organisms.
Antidote to chlorophacinone
In the event of poisoning with 1,3-indanedione, vitamin K1 must be given immediately as an antidote. In an emergency, the missing coagulation factors must be replaced directly. According to several sources, neither vitamin K3 nor K4 is suitable as an antidote for this substance.
Phosphine formers
As a fumigant
Aluminum phosphide , magnesium phosphide and calcium phosphide form with the moisture of the earth hydrogen phosphide . Aluminum phosphide (AlP) reacts e.g. B. so with water:
The gaseous hydrogen phosphide (PH 3 ) formed in this way is a breath poison that spreads in the rodents' underground passages and kills them. Large volumes of grain that are transported by ship are added to aluminum phosphide or calcium phosphide tablets, which react on the transport route with the residual moisture (water) of the grain to form phosphorus hydrogen, which kills rodents and other pests. Phosphorus is highly flammable and can form a dangerous, explosive gas mixture with the air. The agent must not be used in the vicinity of surface water.
In Annex I and IA of Directive 98/8 / EC, only aluminum phosphide and magnesium phosphide are listed as conditionally approved biocidal phosphine formers (as of August 2011). The implementation of fumigations with some of the active substances mentioned here is subject to authorization in Germany. Rodenticides with calcium phosphide as an active ingredient (trade name Polytanol ) are approved in Germany and Austria .
Zinc phosphide reacts much more slowly with water (moisture) so that it is usually not used as a fumigant. On the other hand, zinc phosphide was used as an active ingredient on bait. Zinc phosphide is currently (8/2011) not listed as a biocide in Annex I or Ia (positive list) of the EC Biocide Directive.
As food poison
Zinc phosphide is used as an active ingredient in bait. As soon as the zinc phosphide comes into contact with the stomach acid after being swallowed, the very toxic phosphine is formed in the body.
Zinc phosphide is used as an active ingredient in poison wheat, on carrot pieces or in dough flakes. To prevent poisoning of non-target organisms, the bait must not be placed openly on the surface of the soil.
Other
There are also other rodenticides (for example bromethalin ) that cannot be classified in any of the groups mentioned above.
Old toxins
Arsenic compounds , barium carbonate , strychnine and white phosphorus , which were used as rodenticides until around 1950, are also so toxic to humans that they are no longer generally approved for this application. Thallium (I) sulfate is an exception. It was used from the 1920s to around the mid-1970s. B. from Bayer AG in the products Zelio poison grains (poison wheat; active ingredient content 2% thallium sulfate; packaging with red warning color) and Zelio paste (active ingredient content 2.5% thallium sulfate; packaging with blue warning color). Today, thallium sulfate is no longer generally permitted. However, in special cases with special approval from the federal authority, it can be used for the extermination of rats and mice in closed rooms (i.e. intradomally). However, it has become obsolete due to the second generation of coumarin derivatives.
Any remaining stocks of the poisons mentioned here may not be used, but must be disposed of as hazardous waste. The use of hexogen kneaded with bread dough is no longer permitted, as this active ingredient falls under the Explosives Act .
Calcium carbide
Calcium carbide is not a rodenticide in the strict sense of the word, as it aims at expulsion rather than poisoning. This repellent is placed in the corridors of the rodents and develops with the moisture in the earth ethine (= acetylene), which contains traces of the unpleasant-smelling gases ammonia , hydrogen phosphide and hydrogen sulphide . When handling, it must be noted that ethine is a highly flammable gas which forms an explosive mixture with air at a concentration between 2.3% and 82% ethine. Calcium carbide must not get into water, as the calcium hydroxide produced during the reaction increases the pH value, which is dangerous for aquatic life.
Individual evidence
- ↑ Approval of rodent control agents with anti-clotting agents (2nd generation anticoagulants). (PDF; 1.3 MB) p. 6 , archived from the original on May 11, 2013 ; Retrieved April 24, 2013 .
- ↑ ENVIRONMENTAL SITUATION IN AUSTRIA - Eighth environmental control report from the Environment Minister to the National Council Vienna, July 1, 2007. (PDF; 10.7 MB) Retrieved on January 24, 2012 .
- ↑ Approval of rodent control agents with anti-clotting agents (2nd generation anticoagulants). (PDF; 1.3 MB) Archived from the original on May 11, 2013 ; Retrieved April 24, 2013 .
- ↑ Reports and information . Reports and Information, 1954.
- ↑ a b Bennett G. Galef: Socially mediated attenuation of taste-aversion learning in Norway rats: Preventing development of "food phobias" , Animal Learning & Behavior, Volume 17 (4), pp 468-474 (1989).
- ↑ Stähler safety data sheet
- ↑ Dana Gray Allen, John K. Pringle, Dale A. Smith; Handbook of veterinary drugs.
- ↑ General Directorate Health and Food Safety of the European Commission: Entry on calcium phosphide in the EU pesticide database ; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on February 17, 2016.
- ↑ Annex I and IA to the EC Biocide Directive ( Memento of July 7, 2013 in the Internet Archive ).
- ↑ Fighting field mice: what means are allowed, what is forbidden? on agrarheute.com (accessed October 20, 2016)
- ↑ Anna Charlotte Fuhrmeister: Poisonings - Panorama change of the last decades . Dissertation at the Medical Faculty of the University of Bonn, 2005, p. 106.
Safety, health and environmental protection (SHE): Please read the safety data sheet and the manufacturer's instructions for use before using the individual agents.