Population response of rodents to control with rodenticides

We summarize theoretical approaches and practice of rodent pest control in Russia and former USSR during last 50 years. We review literature as well as original data to understand mechanisms of rodent populations recovery after chemical control campaigns in urban areas, agricultural lands and natural foci of plague. Laboratory and field experiments indicate that inherent individual variation in behavioural, physiological and life-history traits provides survival of heterogeneous mix of individuals in residual population with increased resistance to poisonous baits and high reproductive potential that leads to fast recovery of a population. In a series of field experiments with various rodent and lagomorph species （Mus musculus, Rattus norvegicus, Meriones unguiculatus, M. meridianus, M. tamariscinus, Ochotona pallasii ） we have shown that patterns of recolonization of depopulated area and mechanisms of population recovery vary among species and depend on species-specific social organization. After control territorial and group-living species demonstrated an increase in mobility and affiliative and marking behaviour and a decrease in intraspecific aggression. The rate of recolonization of treated areas was high due to redistribution of survived individuals and immigration by neighbors. Population recovered to original level due to increased breeding performance and fecundity of both survived residents and immigrants. In contrast, socially-independent species exhibited minor changes in behaviour. Recolonization was mainly due to better survival and recruitment of youngs, so the rate of recolonization was low. Species-specificity of behavioural compensation mechanisms to control should be considered when developing ecologically based rodent management strategies

Acute Inhalation Toxicity Study of 2-Fluoroaceta mide in Rats

One of the most potent rodenticides is 2_fluoroacetamide (2_FA). Toxicity of this chemical is well documented. However, its inhalation toxicity data is not available in the literature. Hence, \{acute\} inhalation toxicity study was carried out by exposing male and female rats to aerosols of 2_FA at different concentrations for 4 h in a dynamically operated whole body inhalation exposure chamber. During and after the inhalation exposure the rats were less active, and showed mild tremors and convulsions. At higher concentrations the rats died after 2_3 days. The estimated 4_h LC 50 for male and female rats was 136.6 and 144.5 mg·m -3 respectively. Exposure to 0.7 LC 50 for 4 h duration showed an increase in the liver weight of male and female rats 7 days after exposure. Various haematological and biochemical variables determined were within the normal limits. However, histological findings showed injured lung as indicated by desquamation and necrosis of the epithelium of the respiratory tract. Marked hypertrophy of hepatocytes displaying strong acidophilic granulated cytoplasm was observed. Focal dilatation of renal proximal tubules in kidney with cytoplasmic vacuolation, and irregularly placed pyknotic nuclei were seen. The present study shows that 2_FA is a highly toxic chemical through the inhalation route based on the LC 50 value. Consequently necessary precautions should be taken during its handling.

The result of bagged Pyrinuron baits for controlrodent pest of forests

Bagged and dispersed Pyrinuron (a self-formulated rodenticide) were tested for control of Clethrionomus rutilus and Clethrionomus rufocanus in larch plantation, Pingshan area, Heilongjiang Province from Oct. 1998 to Apr. 1999. The results showed that the bagged Pyrinuron has good result for control of the two rodent pests. The density of rodents was reduced by 90.5% after application of bagged Pyrinuron. This application method has characteristics of long residual period, bait not going mould and saving labour force.

Persistence of Coumarins Rodenticidas Brodifacoum and Coumatetralyl in Brazilian Urban Environment

The chemical control of Rattus norvegicus in S?o Paulo city has been done using coumarins rodenticides as paraffin block and powder contact. The brodifacoum-paraffin block is placed in culverts and similar sites being subject to the action of the weather that can change the concentration of active ingredient. Whereas coumatetralyl-powder contact is applied on the entrance of the burrows, being subject to the action of the weather, that can help in the active ingredient degradation and its transference to other environments. There is not information on the environmental persistence of these active ingredients in their formulations after placing on the environment. So this research evaluated the persistence of brodifacoum-paraffin block and coumatetralyl-powder contact after two months under environmental conditions. One hundred blocks were put in culverts and weekly, during two months, three blocks were retreated and submitted to extraction and the extract analyzed by high performance liquid chromatography for quantification of active ingredient. The coumatetralyl-powder contact was applied in experimental systems simulating the field conditions. Soil and water samples were collected weekly, for two months, submitted to the extraction and the extracts analyzed by high performance liquid chromatography for quantification of active ingredient. The results pointed the stability of brodi-facoum-paraffin block under real application environmental conditions because 100% of active ingredient was recovered after exposition of the blocks. However, there was decreased about 80% in the concentration of coumatetralyl-powder contact on top soil during two months of environmental exposition, however there was not found it in water sample.

Acute oral toxicity of zinc phosphide:an assessment for wild house mice(Mus musculus)

Irregular plagues of house mice,Mus musculus,incur major economic impacts on agricultural production in Australia.The efficacy of zinc phosphide(ZnP),the only registered broadacre control agent for mice,is reported as increasingly variable.Have mice become less sensitive over time or are they taking a sub-lethal dose and develop-ing aversion?In this laboratory study,the sensitivity of mice(wild caught;outbred laboratory strain)was assessed using oral gavage of a range of ZnP concentrations.The estimated LD50 values(72–79 mg ZnP/kg body weight)were similar for each mouse group but are significantly higher than previously reported.The willingness of mice to consume ZnP-coated grains was determined.ZnP-coated grains(50 g ZnP/kg grain)presented in the absence of alternative food were consumed and 94%of wild mice died.Mice provided with alternative food and ZnP-coated wheat grains(either 25 or 50 g ZnP/kg grain)consumed toxic and non-toxic grains,and mortality was lower(33–55%).If a sublethal amount of ZnP-coated grain was consumed,aversion occurred,mostly when alternative food was present.The sensitivity of wild house mice to ZnP in Australia is significantly lower than previously assumed.Under laboratory conditions,ZnP-coated grains coated with a new higher dose(50 g ZnP/kg grain)were readily consumed.Consumption of toxic grain occurred when alternative food was available but was decreased.Our unambiguousfindings for house mice indicate a re-assessment of the ZnP loading for baits used for control of many rodents around the world may be warranted.

Unwanted and unintended effects of culling: A case for ecologically-based rodent management

In this study, the ecological effects of culling programs are considered in the context of rodent pest management.Despite the escalation of rodent problems globally, over the past quarter of a century there have not been many newdevelopments in culling programs directed at managing these populations. There is a strong reliance on broad scaleuse of chemical rodenticides or other lethal methods of control. The ecological consequences of culling programsbased on chemical rodenticides and bounty systems are considered. Although rodents cause tremendous economichardship to people on a continental scale, usually less than 10% of species cause substantial impacts. Indeed, manyspecies of rodent provide important “ecological services” and, given that culling programs rarely distinguishbetween rodent species, often the non-pest rodents are at grave risk. Rodent control is conducted with littleappreciation of what proportion of the population would need to be culled for a significant reduction in economicdamage. In Indonesian rice fields, once rodent densities are high then a reduction in yield loss from 30% to 15%would require more than 75% of the population to be culled;a reduction to less than 5% yield loss would requiremore than a 95% cull. The negative ecological consequences of culling can be better managed if the method isspecifically tailored to the species that need to be managed. A greater emphasis on ecologically-based rodentmanagement would assist markedly in reducing the unwanted and unintended effects of culling.

Anticoagulant rodenticide intoxication in east China:a three-year analysis

The study was designed to analyze the incidence and pattern of anticoagulant rodenticide intoxication in east China and to discuss strategies of diagnosis based on laboratory analysis experience.A total of 117 patients with anticoagulant rodenticide poisoning confirmed by toxicological analysis in east China were included in this study from 2011 to 2013.The mean concentration of anticoagulant rodenticide,age,and gender of these patients,as well as the mode and type of poisoning,were discussed.The age ranged from less than 1 to 80 years with the feeble preponderance of males(M D 53.0%,F D 47.0%).The 0–9 age group covered the largest ratio of these anticoagulant rodenticide poisoning patients.Accidental or voluntary ingestion seems to be the most common cause of intoxication,with still the poisoning cause being unknown for a large number of positive analyses.Bromadiolone was the most commonly observed anticoagulant rodenticide found in the biological samples,followed by brodifacoum.The concentrations of bromadiolone and brodifacoum that were detected in the first collected whole blood from each patient ranged from 1 to 878 ng/mL(mean 97.9 ng/mL)and from 0.5 to 1566 ng/mL(mean 225.1 ng/mL),respectively.The data analysis shows a high incidence of anticoagulant rodenticide poisoning without awareness of the poisoned subjects,clearly emphasizing the need for toxicological analysis in patients with vitamin K-dependent coagulation disorder and restriction on availability of anticoagulant rodenticide.

A New Method for Detection and Identificationof Sodium Fluoroacetate and Fluoroacetamideby NMR Spectroscopy

Nuclear magnetic resonance (NMR) is well known for its capacity to identify thestructure of chemical compounds. But, as we know, it has not yet been used in thedetection and identification of fluorine-containing toxicants in complicated matrixes.Here some efforts were made in this area to apply this powerful technique totoxicological analysis. Sodium fluoroacetate and fluoroacetamide are two fluorine-containing rodenticidesof high toxicity. Their determination in samples related to intoxication is

Efficacy of anticoagulant-free alternative bait products against house mice(Mus musculus)and brown rats(Rattus norvegicus)

The attractiveness and efficacy of four anonymous anticoagulant-free alternative rodenticides(active ingredients cellulose or plaster)were tested on wild strain groups of house mice(Mus musculus Linnaeus)and brown rats(Rattus norvegicus Berkenhout)in laboratory choice and no-choice experiments.In no-choice tests,the rodenticide product was offered ad libitum to the animals for 21 days(mice)and 10 days(rats),respectively.In choice tests,the rodenticide product and non-poisoned food were offered for 28 days(mice)and 14 days(rats).Two products with cellulose(C1 and C2)as the active ingredient were tested against both mice and rats.In two no-choice tests with mice,all animals died within 14 days(C1)and 21 days(C2);in a third no-choice test,11%(2/18)of mice survived(C1:21 days).In all three tests,numerous incidents of cannibalism were observed.The attractiveness of cellulose baits was tested for one product(C1)in three trials against normal food pellets.In all trials,bait consumption was low and all mice survived(15-34 days).Two no-choice trials with cellulose baits(C1)were conducted on groups of Rattus norvegicus;11 of 12 rats survived the bait feeding period and no cannibalism or sign of aggression between conspecifics was observed.Two plaster-based(CaSO_(4)·0.5H_(2)O)products(P1 and P2)were tested against both mice and rats;in no-choice tests,only one mouse(n=20)and no rats(n=8)were killed,although the baits proved to be attractive for rats and mice in choice tests.The results of these experiments suggest that neither cellulose-based nor plaster-based rodenticides are suitable agents for the control of Mus musculus and Rattus norvegicus.

Impact of fertility versus mortality control on the demographics of Mastomys natalensis in maize fields

The multimammate mouse,Mastomys natalensis,is the most common rodent pest species in sub-Saharan Africa.Currently,rodenticides are the preferred method used to reduce the population of rodent pests,but this method poses direct and indirect risks to humans and other non-target species.Fertility control is a promising alternative that has been argued to be a more sustainable and humane method for controlling rodent pests.In this study,we compared the effectiveness of fertility control bait EP-1(quinestrol(E)and levonorgestrel(P),10 ppm)and an anticoagulant rodenticide bait(bromadiolone,50 ppm)on the population dynamics of M.natalensis in maizefields in Zambia during 2 cropping seasons.M.natalensis was the most abundant species in maizefields(77%of total captures).Fertility control reduced the number of juveniles and suppressed population growth of M.natalensis at the end of the 2019–2020 cropping season.The population density initially decreased after rodenticide treatment,but the population rapidly recovered through immigration.None of the treatments influenced maize damage by rodents at germination(F2,67=1.626,P=0.204).Applying the treatments during the maize seeding time was effective at suppressing population growth at the end of the cropping season than application the month before maize seeding.This research indicates that a single-dose delivery of EP-1 and rodenticide have comparable effects on the population dynamics of M.natalensis.Thesefindings are important in developing fertility control protocols for rodent pest populations to reduce maize crop damage and improve yields.

Management of Aluminium Phosphide Poisoning with a Holistic Approach at NHL Municipal Medical College and Hospital,Ahmedabad

Background:Aluminium phosphide is a usual ingredient of rodenticide and its poisoning is a common cause of suicide in India.Signs and symptoms of its toxicity are well-known.Its toxic effects are mainly due to liberation of phosphine gas which causes cell hypoxia due to inhibition of oxidative phosphorylation and results in circulatory failure.Aims and Objectives:Mortality with aluminium phosphide is high as there is no specific antidote available yet.And hence we need to explore holistic treatment approach to improve patient outcomes in aluminium phosphide poisoning.Materials and Methods:Present study discusses a holistic treatment approach to aluminium phosphide poisoning in this retrospective analysis of 100 cases from a tertiary care hospital in this study.Results:Around 65%patients survived due to the holistic treatment approach and correct treatment protocol with supportive therapy.Conclusions:The aggressive and appropriate management with continuous hemodynamic monitoring and holistic treatment approach can reduce the mortality significantly in aluminium phosphide poisoning.