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The toxicity and efficacy of the acute rodenticide scilliroside was evaluated in the laboratory against the lesser bandicoot rat, Bandicota bengalensis. The acute oral LD50 and LD 95 doses for males were 0·8 mg/kg and 2·5 mg/kg respectively, and for females were 0·5 mg/kg and 1·6 mg/kg, respectively. When caged bandicoots were given a choice between plain and poison baits, the optimum concentration of scilliroside was found to be 0·05%. Symptoms of poisoning appear from 22 to 34 min after feeding starts and the latency pattern indicated an abrupt ceasing to feed at these points. Death occurred from 2 h to as long as 6 days after poisoning, following prolonged convulsive seizures. There appears to be aversion to scilliroside at all concentrations in food baits. Maximum mortality attained on free-choice feeding on scilliroside was 90%. Despite these disadvantages, the material may have merit as an alternative rodenticide to zinc phosphide where acute toxicants are to be used. [ABSTRACT FROM PUBLISHER]

The baseliiie susceptibility of the lesser bandicoot rat, Bandicota bengalensis, from Rangoon, Burma, to five anticoagulant rodenticides was established with no-choice feeding in the laboratory. The susceptibility of lesser bandicoots to the several poisons (brodifacoum, difenacoum, diphacinone, coumatetralyl, and warfarin) was such that they were offered at a 0·001 % concentration. B. bengalensis was most susceptible to brodifacoum, and in descending order, difenacoum, coumatetralyl, diphacinone and warfarin. In comparison with Rattus norvegicus on warfarin at 0·005 %, B. bengalensis proved more susceptible. Feeding tests at 0·005 % concentration indicated that a 1-day feeding on broclifacoum and difenacoum would result in complete mortality, whereas coumatetralyl and warfarin would require 4 days feeding to a 100 % kill. Brodifacoum and difenacoum are recommended at 0·002–0·005 % bait concentrations and coumatetralyl at 0 001 % concentrations for the control of B. bengalensis in the field in Rangoon. The use of any anticoagulant material in rat control should be alternated with acute toxicants to retard the possible development of anticoagulant resistance. [ABSTRACT FROM PUBLISHER]

The properties of pyriminyl (N-3-pyridylmethyl-N′-p-nitrophenyl urea) as a rodenticide against the lesser bandicoot rat (Bandicota bengalensis) in Rangoon, Burma, were investigated in the laboratory. The acute LD 50 and LD 95 dose of orally administered pyriminyl for B. bengalensis were found to be 6·7 mg/kg and 23·0, mg/kg of body weight respectively. When caged bandicoots were given a choice between plain and poisoned baits, the optimum rodenticidal concentration in the bait was found to be 0·25–0·5%. Symptoms of pyriminyl poisoning appear from 1 to 4 h after feeding starts, giving individual animals time to consume from 2 to over 30 LD 50 doses of 0·5% pyriminyl before feeding stops. Deaths occurred from 4 to 96 h after either oral dosing or free-choice feeding. There appeared to be no significant aversion to the poison at 0·25% or 0·5% concentration in foods. The potential hazards and use of pyriminyl as a field bait against populations of B. bengalensis are discussed. [ABSTRACT FROM PUBLISHER]

An analysis was made of the dose-response of several populations of Rattus norvegicus fed upon baits containing 0·005% warfarin for various numbers of days. Warfarin-susceptible populations fell within a narrow range, with LFP50s and LFP98s (lethal feeding periods in days to obtain 50% and 98% mortalities respectively) of up to 3·0 and 5·0 days respectively. The probability of an individual rat from these populations surviving a six-day feeding period was estimated at 0·003 or less. Populations with responses falling beyond these limits were regarded as warfarin-resistant.Six of nine populations of R. norvegicus, from England, Germany and the United States, were determined to be warfarin-susceptible within the narrow limits given above. In all six cases, no animals survived the six-day WHO feeding test for anticoagulant susceptibility. In three populations from the United States, where rats survived six days feeding, their population responses clearly fell outside the measures given above. It is suggested, tentatively, that anticoagulantresistant Norway rat populations be defined as those whose LFP50 and LFP98 exceeds 3·0 and 5·0 days respectively, and in which the probability of an individual animal surviving a six-day feeding upon 0·005% warfarin is 0·01 or more. [ABSTRACT FROM PUBLISHER]