Many human diseases are caused by the effects of other organisms that ‘choose’ our bodies as their environment. What they do when they are inside us causes problems with our physiology. We are, naturally, anthropomorphic about this. We see it as ‘our’ disease, caused by a micro-organism and often ‘carried’ by another animal. We call the animal that carries the disease to us a vector. Many arthropods fall into this category.
Ticks, Fleas and Kissing Bugs
We think of the Deer Tick as a carrier of Lyme Disease, and of the American Dog Tick as a carrier of Rocky Mountain Spotted Fever and Tularemia. It might be better if we thought of this as the complex relationships between six different species of animal; humans, two tick species, and three species of bacteria. This way of thinking would not help us cure our diseases, but it might be a better way of understanding exactly what is going on. Similarly Cat Fleas carry the Cucumber Tapeworm and some Kissing Bugs carry Chaga’s Disease.
Mosquitoes
The Tiger Mosquito carries Dengue Fever and Eastern Equine Encephalitis in the same way, but I have tried to change our perspective a little in my article entitled School for Young Tigers.
Points of view
There are many more examples of invertebrates that can act as vectors and carry human diseases. Many more carry diseases of other animals such as cats, dogs, birds and horses. We tend to look at these things from the point of view of the invertebrate which is involved, but there are many other possible perspectives. Medics and veterinarians would look at the diseases, microbiologists would look at the micro-organisms and biologists look at the bugs!
To fully understand what is going on I would argue that we need to avoid being anthropocentric, in other words we must look at what happens with the eyes of an ecologist who would see a number of different species and the ways in which they affect one-another. We loose the whole perspective when we see things only as they affect human beings.
So, while it is true that many invertebrates can carry human diseases, I suggest that it is better to think of this as the complex ways in which the species involved interact.
read an article about Chagas Disease
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