Pre-baiting for increased acceptance of zinc phosphide baits by voles: an assessment technique

During a product-performance test of 2% zinc phosphide (Zn₃P₂) steam-rolled-oat groats (11.2 kg ha⁻¹) to control voles (Microtus spp) in alfalfa (Medicago sativa), randomly located, brushed-dirt plots were used to assess broadcast distribution and removal/acceptance of placebo particles. Results showed that the Spyker® Model-75 Spreaders were calibrated adequately, with placebo baits broadcast uniformly onto plots [x ± SD = 3.5 (±2.7) groats 930 cm⁻¹]. Acceptance of the placebos by voles increased rapidly – 28% and 60% by 24 h and 48 h post-broadcast, respectively. Analyses of variance confirmed the uniformity (non-significance) of particles broadcast among enclosures/plots and the significantly greater removal/acceptance of placebos across days. This technique affords an objective decision-making tool for applicators and researchers applying Zn₃P₂ baits in field situations – an objective technique of assessing pre-bait acceptance that should improve efficacy of the rodenticide. © 1999 Society of Chemical Industry     

Peliosis hepatis and hemoperitoneum in a dog with diphacinone intoxication

Objective: To describe the clinical course of a dog presented with peliosis hepatis and hemoperitoneum in concert with anticoagulant rodenticide intoxication.
Case summary: A 7.75-year-old spayed female Shetland Sheepdog presented with clinical signs consistent with hypovolemia, hemoperitoneum, and a history of bright green stool 3 days before the onset of clinical signs. Initial packed cell volume/total solids were consistent with acute hemorrhage. A coagulation profile showed prolongation in activated clotting time and prolongation of both prothrombin and activated partial thromboplastin time, suggesting abnormal coagulation. Abdominal hemorrhage persisted in the face of normalization of the hemodynamic status and coagulation profile, and treatment with Vitamin K₁. Abdominal ultrasound revealed multiple patchy hypoechoic areas throughout the caudate liver lobe. An exploratory laparotomy was performed 24 hours after presentation and revealed the caudate liver lobe as the source of the hemorrhage. Histopathologic examination of a specimen of the liver was consistent with peliosis hepatis. Toxicologic testing identified diphacinone levels in the blood consistent with anticoagulant rodenticide intoxication. Postoperative recovery was uneventful, and within 48 hours the dog was discharged. The dog returned to full function and a hepatic ultrasound performed 15 months postoperatively showed no significant abnormalities.
New or unique information provided: Exposure to anticoagulant rodenticides may be associated with the development of peliosis hepatis in dogs.     

Resistance to anticoagulant rodenticides in Germany and future strategies to control Rattus norvegicus

Widespread anticoagulant resistance was discovered in populations of the brown rat (Rattus norvegicus Berk.) in an area of roughly 8000 km² in north-west Germany. Resistance testing was performed by feeding tests and/or by measuring blood clotting response after intraperitoneal injection of a sublethal testing solution. A hierarchical resistance system was found with warfarin resistance at the base followed by bromadiolone/coumatetralyl resistance to difenacoum resistance at the top. Warfarin resistance was spread over the whole area with reduced incidence towards the edges. Difenacoum resistance represented the highest level found so far and was restricted to the inner zone of the resistance area where it occurred with a frequency of 6% of all individuals tested. Breeding experiments with bromadiolone-resistant rats showed that expression of the bromadiolone resistance gene differed in the two sexes, suggesting additional sex-linked modifying effects to the resistance gene. Control strategy within the resistance area with respect to prevention of further selection for resistance is discussed.     

Rodenticide grain bait ingredient acceptance by Norway rats (Rattus norvegicus), California ground squirrels (Spermophilus beecheyi) and pocket gophers (Thomomys bottae)

Vertebrate pest control in California is often accomplished through the use of rodenticide grain baits. These grain baits are composed of steam-rolled oats (SRO), a toxicant, an indicator dye and an oil combination. A series of tests were performed to determine the effects of various dye and oil formulations on acceptance of grain bait by Norway rats [Rattus norvegicus (Berk)], California ground squirrels [Spermophilus beecheyi (Richardson)] and pocket gophers (Thomomys bottae Eyd & Gerv). Seven different dyes, four oil formulations and clean (untreated) oats were tested for acceptance. The addition of the selected oils and dyes to grain resulted in no significant differences in consumption. This indicates that there is a wide variety of dyes that could be used in the formulation of rodenticides. These alternatives could aid in proper pesticide use, the deterrence of bait consumption by birds and possibly in ingredient adhesion to the finished bait.     

山西隰县社鼠对溴敌隆的敏感性研究

雌雄分开,随机分组,按5个不同食毒期供给浓度为0.000 5%的溴敌隆毒饵,在实验室做单个笼养无选择摄食试验,并用Bliss计算机程序计算不同食毒期与对应死亡率之间的关系。结果表明,社鼠对溴敌隆的敏感性,性别之间差异无统计学意义(Pb>0.05,PLFP50>0.05),故将雌雄数据合并计算,得毒力回归方程y=3.32+3.81x,LFP50,LFP95,LFP99及其95%置信限分别是2.76(2.17～3.51)d,7.47(4.42～12.62)d和11.27(5.79～21.95)d。按世界卫生组织推荐的以致死99%敏感靶标鼠种的食毒期(LFP99)取整天数作为抗药性检验标准,山西隰县地区社鼠摄食浓度为0.000 5%溴敌隆毒饵12 d存活即为抗性鼠。     

Efficacy and attractiveness of zinc phosphide bait in common voles (Microtus arvalis)

BACKGROUND: Minimising the concentration of active ingredient in rodenticide bait is desirable economically and for the protection of the agroecosystem. This study aimed to identify a zinc phosphide concentration that balances palatability and efficacy for common vole (Microtus arvalis Pall.) management and to compare the attractiveness of two bait carriers. RESULTS: Bait uptake of voles was reduced by 87–98% compared with plain bait when bait contained 0.4–3.2% zinc phosphide. There was an almost 50% decrease in the uptake of zinc phosphide when the zinc phosphide concentration of bait was doubled. Red dye used in commercially available bait decreased bait consumption by 10%. Daily consumption of zinc phosphide bait on days 2 to 5 was half the consumption on the first day of exposure. In bait choice tests, wheat kernels were preferred initially, but within 12 h similar amounts of wheat‐based pellets and wheat kernels were eaten. CONCLUSIONS: According to the results from the laboratory trial, a zinc phosphide concentration of 2.1% seemed to balance uptake/efficacy best and may be most appropriate for the management of common vole populations. This concentration is substantially lower than the concentration used in many registered products. A reduced concentration of active ingredient and the use of pellet bait instead of wheat which is highly attractive for birds may have advantages for agroecosystem health when applying zinc phosphide for rodent control. © Jens Jacob, Mechthild Budde and Angela Leukers, employees of the Federal Research Centre for Cultivated Plants, Germany. Printed with permission.     

青海省玛沁草原鼠害调查与D型生物灭鼠剂灭鼠试验

在对草原鼠害调查的基础上,对D型生物灭鼠剂灭鼠进行了试验,结果表明:D型生物灭鼠剂是一种高效的杀鼠药物,0.10%组的毒饵灭效率为95.32%;0.15%组的毒饵灭效率为97.99%;0.20%组的毒饵灭效率为100%。按照生态平衡与经济学角度来讲,0.10%为最佳配制浓度。