Spread of sexually transmitted disease in ladybirds

A study at the University of Liverpool into the spread of sexually transmitted infection in ladybirds has shown that disease risk to large populations cannot be predicted without a full understanding of the disease dynamics at small geographical scale. Scientists investigated a virulent form of infection in the central and northern European populations of the two-spot ladybird to understand the conditions that favoured disease spread. Researchers found that disease burden in two locations of the same habitat - the lime tree - were very different, despite being within 12km of each other. Variation at small local scale not predicted It is expected that disease epidemics will vary over space, but variation at small local scale, however, was not predicted because it is generally thought that insects move easily and regularly amongst habitats, taking infection with them. The Liverpool team found that there were significant differences between disease outbreak sites that were close to each other, which were caused by differences in mating rates across habitats. The study showed that a healthy supply of food increased the mating frequency of ladybirds, and therefore encouraged disease spread. Ladybirds with less food supply, however, mate less frequently and did not experience the same high rate of infection.