For the longest time, I have always believed that animals have a much stronger immune system than that of humans. And why shouldn’t we think that? After all, we wash our hands after using the bathroom and before we eat. Meanwhile, a dog will drink right out of the toilet or eat any garbage it finds outside. Vultures eat animals that have been rotting in the sun for days. The dogs and the vultures seem to be fine. So that led me to always wonder: Do humans have weaker immune systems than other animals?

But just like humans, animals get sick too. In many of these cases, the illness can kill them.

Building Immunity Against Pathogens

Immunity develops when we expose ourselves to pathogens and our immune system, after experiencing the pathogen, develops a way to fight it. Immunity is also passed on from mother to child via nursing (the antibodies are in the milk), so if the mother has experienced some pathogens in her life and the immune system is active, then she will pass on those antibodies to her offspring.

Sip by sip, the giraffe calf gains more than just nourishment – breast milk is rich in microbiota and ensures any young animal’s protection against numerous diseases.

This is a temporary immunity and if the child/calf/cub is now exposed to that same pathogen they may still become sick but it will be less severe than if they had no protection. If they do not become exposed to the pathogen while they are protected by the mother’s antibodies, the baby will soon lose the ability to fight off the pathogen and will have to re-develop it via its own exposure later.

Wild animals are naturally, more exposed to the ‘dirt’ and ‘bad stuff’ out there and so their offspring are given temporary immunity to that stuff. The offspring, however, mostly become exposed to those same pathogens pretty soon but it doesn’t kill them because they have some protection from their mother. It may not be full-on immunity but enough protection that they might only get mildly sick. Once they have been exposed, then even after the mother’s antibodies wear off, they will be producing their own.

The immune systems of different species, including humans, have evolved to meet the specific challenges they face in their respective environments. Wild animals are exposed to various pathogens and environmental challenges that humans may not encounter, and their immune systems have adapted accordingly. They may have robust defences against certain types of infections prevalent in their habitats.

Lower Human Immunity

Humans have now become accustomed to cleaning our environments to perfection. We as parents still give our immunity temporarily to our children if they are breastfed but many children now are not allowed to become exposed to the ‘dirt’ of the world until long after their temporary protection has worn off. Hence, when older children or adults come into contact with a pathogen that they have absolutely no protection from, the problem can be severe.

It is important to realise that humans are animals too. I couldn’t find any evidence suggesting that our immune system is any weaker than those of other mammals. Certain animals can definitely eat disgusting stuff that would make us sick, and I learnt that these animals simply have stronger stomach acids than we do, not stronger immune systems.

The spotted hyena’s stomach acid pH level is less than two. This is very low when compared with human stomachs, which have a pH level closer to three. This acidity allows the stomach to act as a filter, effectively controlling which microbes can pass through the stomach to the gut.

So, wild animals can drink from dirty water, or eat meat that has been sitting out for days because they have built up some protection to those specific pathogens from a young age. Wild animals who aren’t able to build up strong immune systems probably die young. While those with genes for strong immune systems are likely to survive and pass along their genes.

Contrasting Immunity in Wild Animals and Humans

Wild animals aren’t able to create immunity like humans can. For example, we take antibiotics and vaccinations. Similarly, animals don’t show when they’re sick the way that humans do. This is because of natural selection: if they showed sickness or weakness, they would die, because they couldn’t find food or predators would kill them and eat them. This means that when other animals do eventually appear sick, it’s usually because they’re about to die of the sickness. Humans, on the other hand, don’t have to worry about starving because of a cold or flu, and usually don’t have to worry about being eaten either, so we can show symptoms of our illness while we fight said illness off.

Immunity can also improve during our lives. When individuals (dogs, humans, woodpeckers etc.) are exposed to germs, our immune systems respond right away and have memory cells that keep the body alert for that germ in the future. Animals living in the wild have immune systems that have been introduced to a lot more germs than our immune systems have been.

Studying how immunity works in different animals, including humans, has shown us how they protect themselves. At first, I thought animal immune systems were stronger, but I learned that each species has its own way of dealing with threats. Wild animals pass temporary protection to their babies through exposure to the environment, while humans, with their cleanliness habits, might miss out on early protection.

It’s important to remember that humans are animals too, and although our immune systems have some differences, they’re not necessarily weaker. Our ability to show symptoms and fight off infections is part of our evolutionary journey, showing how we adapt and survive in the natural world.