I've heard of this before. Pathogens, specifically pesticides, may help explain the fall of male fertillity over the past 50 years.

The mechanism seems interesting, however. It is multigenerational, but does not involve mutation. I'd like to read the paper.

The study was carried out on laboratory rats that received high levels of vinclozolin, a fungicide widely used in vineyards, and methoxychlor, a pesticide used to replace DDT when it was banned more than 30 years ago. Scientists found that the male offspring of the exposed rats suffered a sharp decline in the quality and quantity of their sperm and that these traits continued to be passed on down the male line.

Yet the researchers believe that the chemicals did not mutate the genes of the rats - a proven way of passing on damaging traits - but instead may have altered the way the genes work.

Michael Skinner of Washington State University, who led the research team, said nearly all the male rats born in each generation were affected by sperm damage or low sperm counts. He said that the findings, published today in the journal Science, suggest that toxins may play a role in heritable diseases that were previously thought to be caused solely by genetic mutations.