For today's study, the researchers took skin swabs of 3016 tadpole and adult midwife toads from 126 locations across the Iberian Peninsula between 2003 and 2008. They analysed the samples in the laboratory, using a sensitive molecular technique called polymerase chain reaction (PCR) and found Bd infection at 31 of the sites.
The researchers looked at the genetic fingerprints of the fungi causing a cluster of infections and deaths in the Pyrenees and found they were all identical. This suggests that the disease was introduced to the area relatively recently.
The researchers then used mathematical models to determine whether environmental factors, such as minimum and maximum temperatures, rainfall and altitude affected the probability of infection or the risk of fatality. The results showed no link between environmental factors and probability of infection, but infected toads living at high altitude were more likely to die as a result of their infection than those living at lower altitudes.
The authors of the study say the increase in risk of mortality could be because the toads are less able to fight off infection in the mountains, where temperatures are colder, or that the fungus is better adapted to cold environments. The researchers now plan to investigate this further.
|Contact: Lucy Goodchild|
Imperial College London