Why would human untreated pathogens be much more of a hazard than those of pigs, goats or chickens (salmonella, campylobacter, MRSA, Q fever, bird flu…) ?

That's a great question. I spent years in Nursing school, and we studied such topics a lot. But since you asked, here is a nice summary I got online...
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Human pathogens pose a greater hazard than animal pathogens because they are already adapted to infect humans, often spread more efficiently between people, and can carry higher risks of chronic illness or death. Zoonotic pathogens from animals are dangerous too—but they typically require a spillover event and may not transmit as easily human-to-human.
Why Human Pathogens Are More Hazardous to Humans
- Species Adaptation: Human pathogens like norovirus, hepatitis A, and Shigella are already optimized to infect and replicate in human hosts, making them more efficient at causing illness.
- Transmission Efficiency: Many human pathogens spread via direct contact, contaminated surfaces, aerosols, or fecal-oral routes, with low infectious doses. For example, norovirus can infect with as few as 18 viral particles.
- Pathogen Load and Persistence: Human waste often contains high concentrations of pathogens, including viruses, bacteria, and protozoa. These can persist in soil and water, increasing exposure risk.
- Antibiotic Resistance: Human pathogens are more likely to carry multi-drug resistance genes, especially in urban or hospital settings. This makes infections harder to treat and control.

Animal Pathogens: Still Dangerous, But Different
- Zoonotic Potential: Pathogens like salmonella, campylobacter, MRSA, and Q fever can infect humans, but they often require specific exposure routes (e.g., handling raw meat, inhaling barn dust).
- Limited Human-to-Human Spread: Most animal pathogens don’t spread easily between humans. For example, campylobacter rarely causes outbreaks without contaminated food or water.
- Spillover Events: Diseases like bird flu or Q fever typically emerge through spillover, where a pathogen jumps from animals to humans. These events are rare but can be catastrophic if the pathogen adapts to human transmission.
Environmental and Public Health Implications
- Human waste requires stricter treatment protocols because of its higher risk profile. That’s why untreated human feces are not permitted for direct land application in most countries.
- Animal manure can be composted or aged, reducing pathogen load before use in agriculture. Even then, it’s regulated to prevent contamination of food crops.
One Health Perspective
The
One Health framework emphasizes that human, animal, and environmental health are interconnected. While animal pathogens are a major concern—especially in farming and wildlife contexts—
human pathogens pose the most direct and immediate threat to public health when untreated waste is mishandled
journalofethics.ama-assn.org CDC WHO.
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All of that summary is consistent with what I learned in Nursing school. Having said that, science is having a hard time here at the moment and many people don't believe in some of our modern medicine and practices. I don't want to get political, but just let me say that in Nursing school we were always taught to follow Evidence-Based Practice as defined here...
What I always appreciated about EBP is that new research could bring new knowledge to our profession and we had to be open to new patient care as needed.
I spent many hours looking at bacteria and viruses under the microscope, but I think the science is pretty solid on human pathogens being a greater hazard than animal pathogens. Of course, I always wash my hands after tending my chickens, because animal pathogens can get you sick, too. Actually, as a RN, I'm always washing my hands out of habit, even at home.

Does any of that make sense to you? I have not lived in the Netherlands, and don't know much about how your people feel about these topics. It sounds like your people are light years ahead of us in terms of Green ideas and sustainable practices. I'm willing to consider other ideas even if they run contrary to my education and understanding.