What is filth, exactly?
The FDA handbook catchily called "Food Defect Action Levels: Levels of Natural or Unavoidable Defects in Foods That Present No Health Hazards for Humans," says that filth is "objectionable matter contributed by insects, rodents, and birds; decomposed material; and miscellaneous matter such as sand, soil, glass, rust, or other foreign substances."
Sounds good enough to eat.
In the booklet, the FDA writes that "it is economically impractical to grow, harvest, or process raw products that are totally free of non-hazardous, naturally occurring, unavoidable defects."
So there is RODENT, BIRD and INSECT filth in most of your food and completely allowable..