Studies were conducted on the potential use of cholecalciferol as an alternative to anticoagulant rodenticides to control common rat pest in oil palm plantations, i.e., wood rats, Rattus tiomanicus, and the secondary poisoning impact of cholecalciferol on barn owls, Tyto javanica javanica. The laboratory efficacy of cholecalciferol (0.075% a.i.) was compared with commonly used first-generation anticoagulant rodenticides (FGARs): chlorophacinone (0.005% a.i) and warfarin (0.05% a.i). The 6-day wild wood rat laboratory feeding trial showed cholecalciferol baits had the highest mortality rate at 71.39%. Similarly, the FGAR chlorophacinone recorded a mortality rate of 74.20%, while warfarin baits recorded the lowest mortality rate at 46.07%. The days-to-death of rat samples was in range of 6-8 days. The highest daily consumption of bait by rat samples was recorded for warfarin at 5.85 ± 1.34 g per day while the lowest was recorded in rat samples fed cholecalciferol, i.e., 3.03 ± 0.17 g per day. Chlorophacinone-treated and control rat samples recorded consumption of about 5 g per day. A secondary poisoning assessment on barn owls in captivity fed with cholecalciferol-poisoned rats showed after 7 days of alternate feeding, the barn owls appeared to remain healthy. All the barn owls fed with cholecalciferol-poisoned rats survived the 7-day alternate feeding test and throughout the study, up to 6 months after exposure. All the barn owls did not show any abnormal behavior or physical change. The barn owls were observed to be as healthy as the barn owls from the control group throughout the study.
The brown rat (Rattus norvegicus) is a relatively recent (<300 years) addition to the British fauna, but by association with negative impacts on public health, animal health and agriculture, it is regarded as one of the most important vertebrate pest species. Anticoagulant rodenticides were introduced for brown rat control in the 1950s and are widely used for rat control in the UK, but long-standing resistance has been linked to control failures in some regions. One thus far ignored aspect of resistance biology is the population structure of the brown rat. This paper investigates the role population structure has on the development of anticoagulant resistance. Using mitochondrial and microsatellite DNA, we examined 186 individuals (from 15 counties in England and one location in Wales near the Wales-England border) to investigate the population structure of rural brown rat populations. We also examined individual rats for variations of the VKORC1 gene previously associated with resistance to anticoagulant rodenticides. We show that the populations were structured to some degree, but that this was only apparent in the microsatellite data and not the mtDNA data. We discuss various reasons why this is the case. We show that the population as a whole appears not to be at equilibrium. The relative lack of diversity in the mtDNA sequences examined can be explained by founder effects and a subsequent spatial expansion of a species introduced to the UK relatively recently. We found there was a geographical distribution of resistance mutations, and relatively low rate of gene flow between populations, which has implications for the development and management of anticoagulant resistance.
The recent expanding rat population is causing severe economic losses and diseases in human. The main objective of this study was to evaluate the antifertility effects of Andrographis paniculata (AP) methanol extract on the weight of testis, sexual behaviour, fertility, sperm quality and serum testosterone level in treated male rats compared with control rats. A total of 21 adult male rats Sprague-Dawley aged 12 weeks were divided into three groups; control group (distilled water), low dose group (800 mg/kg) and high dose group (1600 mg/kg) of AP methanol extracts given orally for 24 days. Body and testis weight, sexual behaviour test, fertility test, sperm quality and serum testosterone level were measured. Oral administration of AP methanol extract showed a significant decrease in testis weight, number of mountings, number of fetuses, sperm count, sperm motility and serum testosterone levels for all treatment group as compared with the control group, whereas mortality showed a significant increase. Observation on testis histology of treatment group exhibited features of degeneration in Sertoli cells and germinal cells in the seminiferous tubules, followed by the shrinkage of Leydig cells as compared with the control group, which showed characteristics of normal spermatogenesis. In conclusion, AP methanol extract exhibited antifertility effects in male rats, suggesting that AP is a potential herb to be applied as rodenticide.