Generation Anticoagulant Rodenticides Research Articles

Blood-clotting response tests for resistance to diphacinone and chlorophacinone in the Norway Rat ( Rattus norvegicus Berk.)

Resistance baselines were obtained for the first generation anticoagulant rodenticides chlorophacinone and diphacinone using laboratory, caesarian-derived Norway rats ( Rattus norvegicus) as the susceptible strain and the blood clotting response test method. The ED 99 estimates for a quantal response were: chlorophacinone, males 0.86 mg kg −1, females 1.03 mg kg −1; diphacinone, males 1.26 mg kg −1, females 1.60 mg kg −1. The dose-response data also showed that chlorophacinone was significantly ( p<0.0001) more potent than diphacinone for both male and female rats, and that male rats were more susceptible than females to both compounds ( p<0.002). The ED 99 doses were then given to groups of five male and five female rats of the Welsh and Hampshire warfarin-resistant strains. Twenty-four hours later, prothrombin times were slightly elevated in both strains but all the animals were classified as resistant to the two compounds, indicating cross-resistance from warfarin to diphacinone and chlorophacinone. When rats of the two resistant strains were fed for six consecutive days on baits containing either diphacinone or chlorophacinone, many animals survived, indicating that their resistance might enable them to survive treatments with these compounds in the field.

Combined Superwarfarin and Ethylene Glycol Ingestion:A Unique Case Report With Misleading Clinical History

A markedly elevated prothrombin time (PT) and activated partial thromboplastin time (APTT) were observed in a 24-year-old man who was admitted with a history of ethylene glycol ingestion. Further laboratory evaluation suggested that the coagulopathy was related to acquired factor deficiencies. The PT and APTT improved transiently on usual doses of vitamin K, but rapidly became abnormal again. The coagulopathy was controlled only after large doses of vitamin K for at least 37 days. On further questioning, the patient admitted to consuming a large quantity of a rodenticide. The second generation anticoagulant rodenticides (superwarfarins) result in a potent and prolonged anticoagulant effect by reducing the activity of the vitamin K dependent factors (II, XII, IX, and X). To our knowledge, this is the first reported concomitant ingestion of both ethylene glycol and a superwarfarin compound. This case serves to illustrate how a logical laboratory evaluation can lead to the proper diagnosis, despite a misleading clinical history.

Kinetic Models to Predict Bioaccumulation of Pollutants

Within the context of ecotoxicology, the importance of the bioaccumulation (used in a general sense to describe situations where organisms acquire higher concentrations in their body than are present in their food and/or the ambient medium in which they live) of persistent pollutants in ecosystems became very clear in the late 1950s and early 1960s when populations of birds of prey were severely affected by residues of organochlorine insecticides. Sharp declines in population of sparrowhawk (Accipiter nisus) and peregrine (Falco peregrinus) in Western Europe were associated with residues of dieldrin and heptachlor epoxide originating from seed dressings (Ratcliffe 1980; Newton & Haas, 1984). The thinning of eggshells of raptors and fish-eating birds was associated with residues of pp'DDE (Cooke, 1973; Ratcliffe, 1980; Newton & Haas, 1984). During the same period in Sweden, birds of prey were affected by organomercury compounds used as fungicides (Brinck, 1967). In all these cases there was evidence of marked bioaccumulation of the compounds with movement along food chains. With the withdrawal of aldrin, dieldrin, heptachlor and DDT from most countries of Western Europe and North America, recoveries of populations of certain birds of prey (e.g. sparrowhawk and peregrine) were subsequently documented (Ratcliffe, 1980; Newton & Haas, 1984). Following these events there was a tendency to feel that the problem of bioaccumulation had been solved. Subsequent events were to prove that this was not the case. In 1969, a large kill of fish-eating sea birds (mainly guillemots [Uria aalge] and razorbills [Alca torda]) occurred in the Irish sea, and the birds were found to contain high levels of polychlorinated biphenyls (PCBs). A subsequent investigation implicated PCBs in the disaster but suggested that they were not the primary cause, although a substantial proportion of birds contained residues in liver sufficiently high to cause death in cormorants (Phalacrocorax aristotelis) (NERC Report, 1971; Koeman et al., 1973; Walker, 1990). More recently several studies have shown that high levels of some 15-20 PCB congeners are still to be found in top predators, despite the withdrawal of PCB mixtures from the market (Norstrom, McKinnon & de Freitas, 1976; Borlakoglu, Wilkins & Walker, 1988). Significant levels of certain highly toxic polychlorodibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) have also been reported in fish-eating sea birds (Van den Berg et al., 1987). Organotin compounds have been shown to be effectively bioaccumulated by shellfish. Their implication in the decline of oyster populations when used as antifouling agents in marine paints was a factor leading to their withdrawal from the British Market. Finally, there is evidence that second generation anticoagulant rodenticides (e.g. brodifacoum, bromadiolone and difenacoum) may be bioaccumulated in the livers of predators (e.g. owls) and scavengers (e.g. corvids) which feed upon rats and mice. Why do these lipophilic compounds undergo bioaccumulation in ecosystems? This is not simply an academic question, since an understanding of the critical processes leading to bioaccumulation is fundamental to the solution of an important practical question -how can the risks of bioaccumulation in ecosystems be predicted? How can the potential hazards of new pesticides be assessed? Because of the complexity of ecosystems, there is no single answer to this question and there is no single model or system that will predict all cases of bioaccumulation. In the following account, bioaccumulation will be considered in two distinct situations: 1 Aquatic systems. 2 Terrestrial organisms. In each case model systems will be discussed which may be useful for the prediction of risks of bioaccumulation of lipophilic pollutants.

Field evaluation of bromadiolone in two rat infested areas

Abstract The efficacy of bromadiolone, a second generation anticoagulant rodenticide, was evaluated against the rodent infestation in two localities of S. V. University campus, Tirupati, India. Poison baiting with bromadiolone (0.005%) in loose bait (cracked bajra) and ready‐to‐use wax bait formulation was carried out for 4 days. The two assessment methods of census feed consumption and tracking activity were employed simultaneously to determine the relative efficacy of the candidate poison. The percent reductions of rodent activity determined from the combined results of census feeding and tracking indices were 89.2 and 85.7 in sites I and II, respectively, resulting in a total percent control of 87.5.