Fuzzy: a genetic marker for warfarin resistance in the Norway rat.

No recombination was observed between fuzzy (fz) and warfarin resistance (Rww) in 245 rats from a backcross test for linkage. This locates fz very close to Rw in linkage group I. The map position established for fz makes this allele particularly suitable for use in combination with p (pink-eyed dilution) for linkage tests in group I and as a genetic marker for the Rw locus in studies of warfarin resistance. The map position of fz in the rat corresponds to that of fr (frizzy) in the mouse, suggesting homology between these loci in the 2 species.

Field trials of second-generation anticoagulants against difenacoum-resistant Norway rat populations.

Trials of rodenticidal baits containing 50 p.p.m. difenacoum, 50 p.p.m. bromadiolone or 20 p.p.m. brodifacoum were carried out on farmsteads against populations of Rattus norvegicus containing difenacoum-resistant individuals. Six difenacoum treatments failed in 14--42 days of baiting. Two treatments with bromadiolone succeeded in 23 and 33 days, but four further treatments lasting 35--56 days failed to eradicate the populations. Brodifacoum gave virtually complete control of six populations in 21--73 days and of the ten residual populations left behind by the other two compounds, after baiting for a further 11--85 days. The performance of both bromadiolone and brodifacoum was well below that reported by previous investigators, indicating the possibility of low-grade resistance to these compounds in the difenacoum-resistant strain.

Wavy: a new recessive rexoid mutant in the Norway rat.

A new rexoid mutant is reported for the Norway rat, Rattus norvegicus, designated as wavy (symbol wv) and inherited as an autosomal recessive. Breeding data indicate that wavy is not linked with the known rexoid variant, rex (Re) or with genes in linkage groups I and IV. Additional data indicate that rex is not linked with the linkage group IV gene, nonagouti (a) and confirm that it shows dominant autosomal inheritance. Since both wavy and rex are of full penetrance and viability and may tag new linkage groups, they should be useful as markers in linkage studies.

The susceptibility of Tatera indica, Nesokia indica and Bandicota bengalensis to three anticoagulant rodenticides.

Three South-Asian rodent past species were tested for susceptibility to anticoagulant rodenticides. Wheat fluor containing 0-025% warfarin 0-0375% coumatetralyl or 0-005% difenacoum was fed to 260 Tatera indica, 140 Nesokia indica and 81 Bandicota bengalensis for 1-56 days. Tatera was about as susceptible to anticoagulants as Rattus has been reported to be. Nesokia and Bandicota were extremely variable: though the majority were highly susceptible, the slopes of the dose-mortality curves were close to zero. The difenacoum diet appeared to be more toxic than the warfarin diet to all three species, but less toxic than the coumatetralyl diet to Tatera and Nesokia. All of the anticoagulants were eventually lethal to all of the animals tested.

Laboratory evaluation of gophacide as a rodenticide for use against Rattus norvegicus and Mus musculus.

Laboratory tests were carried out to assess the efficacy of gophacide as a rodenticide against the Norway rat (Rattus norvegicus) and the house mouse (Mus musculus). Results of feeding tests with wild animals suggest that the compound would be more useful against mice than rats, and that 0.3% would be a near optimal concentration for field trials for both species. The hazards of using gophacide as a rodenticide are discussed.

Some properties of calciferol as a rodenticide.

The potentiality of calciferol (alone and combined with warfarin) for the control of commensal rats and mice has been examined in the laboratory. Nearly all animals fed on 0.1% calciferol for 2 days died. Though illness usually reduced food intake after the first 24 hr. there was no sign of aversion to the poison at 0.1% - which is considered to be the lowest concentration suitable for use against Rattus norvegicus, R. rattus and Mus musculus in the field. There was some indication that resistance to warfarin in R. norvegicus may be correlated with susceptibility to calciferol. Toxicity tests with calciferol combined with warfarin indicated an additive effect between the compounds. No evidence for synergism was found however, although elsewhere there is some evidence for this.

Laboratory tests of 5-p-chlorophenyl silatrane as a rodenticide.

The properties of 5-p-chlorophenyl silatrane as a rodenticide against Rattus norvegicus and Mus musculus were investigated in the laboratory. The high oral toxicity of the compound was confirmed. When the compound was given to laboratory rats and mice by stomach tube at lethal dosages, signs of poisoning were observed within a minute. When caged wild rats and mice were given a choice between plain and poisoned baits the optimum rodenticidal concentration in the bait was about 0.5% for both species, producing 50% mortality in wild rats and 95% mortality in wild mice. The results are discussed in relation to safety in use and the probable effectiveness of the compound as a rodenticide in field conditions.