Resistance to anticoagulant rodenticides in Martinique could lead to inefficient rodent control in a context of endemic leptospirosis.

Leptospirosis is a re-emergent worldwide zoonosis. It is endemic in Martinique where transmission conditions are favourable. Humans are usually infected through contact with water contaminated with urine of rodents. Recent human leptospirosis outbreaks in Martinique require today effective rodent management to prevent leptospirosis transmission. Nowadays, use of anticoagulant rodenticides (AR) is the main method implemented to control rodent populations. Nevertheless, intensive use of these AR has selected worldwide many VKORC1-based resistant rodent strains to AR. Our aim was to characterize the sensitivity of Martinique commensal rodents to AR to better prevent leptospirosis transmission. Resistance of house mice to first-generation and in rare cases even to second-generation ARs were clearly demonstrated in Martinique with the detection of the Y139C mutation with a very high allelic frequency of 40% and the A26T/Y139C double-mutation with an allelic frequency of 0.9%. In black rat, the most prevalent rodent in Martinique, 3 new Vkorc1 coding mutations were detected, the H68N, A115T and S149N mutations associated with moderate resistance to first generation AR. Therefore, rodent management in Martinique must be carried carefully to avoid resistance diffusion and maintain long-term effective rodent management, to be able to efficiently prevent leptospirosis transmission.

Bromadiolone susceptibility in wild and laboratory Mus musculus L.(house mice) in Buenos Aires, Argentina.

BACKGROUND: Rodents are major pests in many agricultural systems, where they can cause significant economic losses and involve a sanitary risk. The application of anticoagulant rodenticides for rodent control has showed a decrease in effectiveness through time because of the development of resistant populations and the development of aversion behaviour. The goal of the present study was to test the susceptibility to bromadiolone and the existence of anticoagulant resistance in Mus musculus L. (house mouse) in Argentina. We conducted a feeding test with wild animals captured in poultry farms and a laboratory strain that were fed with bromadiolone bait. RESULTS: Three animals of the field experimental group survived the 21 days study period, while for laboratory animals mortality was 100%. Control field animals which were fed without anticoagulant showed 100% survival. CONCLUSION: We found evidence of the presence of anticoagulant resistant M. musculus L. in the study area. Feeding behaviour may have contributed to increasing the time of survival, and may be a mechanism that allows metabolic clearance of the bromadiolone. Under field conditions control with anticoagulants would be less effective because animals have alternative food.

Environmental factors associated with rodent infestations in Argentine poultry farms.

1. Seasonal variations in rodent infestations were studied at poultry farms in central Argentina as well as the environmental factors associated with rodent infestations at poultry farms. 2. During the summer and winter of 1998 rodent infestation was monitored at 10 poultry farms by means of tracking stations, and 21 environmental variables were selected that a priori could be related with the extent of rodent infestation. 3. There was a higher rodent infestation in winter than in summer. 4. Species detected by rodent sightings at the poultry farms included Akodon azarae, Calomys spp. (C. laucha and possibly C. musculinus) and Mus musculus. 5. In summer, rodent infestation was positively associated with the perimeter of the farm, whereas there was an inverse relationship with the maintenance conditions of the sheds. In winter, rodent infestation was positively associated with the percentage of the borders of the farm covered with vegetation, and with the amount of plant cover, especially the amount of plant cover which was above 20 cm in height. 6. There was no significant relationship between rodent infestation and the time lag since the last application of rodenticide (first-generation anticoagulant) at the farms. 7. These results suggest that strategies for controlling rodents based solely on chemical methods may not be good enough for efficient rodent control. Farms which are properly managed, with a better control of vegetation growth at both the perimeter and within the internal area, in addition to a higher maintenance of sheds have appreciably lower rodent infestations.

Actividad rodenticida de cuatro drogas anticoagulantes / Rodenticide activity of four anticoagulants drugs

Con el propósito de determinar, analizar y comparar el efecto rodenticidad de cuatro drogas anticoagulantes, se sometió a grupos de Rattus norvegicus línea Sprague Dawley no resistentes a drogas anticosagulantes, en tres períodos (2, 3 y 5 días respectivamente), con warfarina, clorafacinona, coumatetralyl y brodifacoum. Para este efecto se trabajó con 110 ratas cepa blanca. Luego, se analizaron y compararon los consumos de cebos para las 4 drogas, determinándose las mortalidades por ingestión de éstas. Se observaron las principales alteraciones anatomopatológicas. Los resultados del experimento muestran disminución significativa (p< 0,05) del consumo de cebo para tratamiento con coumatetralyl en período de 3 y 5 días de cebado, warfarina en el período de 5 dias de cebado y brodifacoum en dos días de cebado. Esta dosificación resultó ser la más eficiente con una mortalidad de 100 por ciento. Coumatetralyl también resultó ser eficiente, provocando 100 por ciento de mortalidad a partir de tres días de cebado, clorafacinona, fue menos eficiente, ya que se logró un 100 por ciento de mortalidad sólo a partir del 5º día de cebado. Se observó alteraciones anatomopatológicas tales como: congestión pulmonar, cardíaca y hepática, esplenomegalia y hepatomegalia. La sangre se observó de color rojo oscuro y sin coagular