Why Typhoid Toxin Targets Only Humans????

Hello every one , 

Today I will be discussing about most harmful toxin ie typhoid toxin. Typhoid toxin is produced  by Salmonella spp which causes a food borne infection (typhoid fever). Typhoid is typically transmitted through food or water contaminated by infected people. 

You must heard of this disease as it is common among humans, but have you heard of dog, or any animal having this disease ,You can find out !

 Think then what the disease will be called .............

It was first seen in a women named mary hence called as Typhoid Mary

then in dog it will be called as Typhoid Dog...........joke

This will not be case, as the typhoid toxin only attacks humans:D

The bacterium Salmonella typhi causes typhoid fever in humans, but leaves other mammals unaffected. Researchers at University of California, San Diego and Yale University Schools of Medicine now offer one explanation — CMAH, an enzyme that humans lack. Without this enzyme, a toxin deployed by the bacteria is much better able to bind and enter human cells, making us sick. This CMAH enzyme change the sugar molecule so that typhoid toxin cannot bind.

All mammals have  cell surfaces with a type of sialic acid sugar called Neu5Ac. In most mammals, the enzyme CMAH coverts Neu5Ac to Neu5Gc, a subtle but important distinction involving a single oxygen atom. 

The toxin damages cells expressing Neu5Ac sugars on their surface, but not those with Neu5Gc (the non-human type).  The findings were confirmed in a mouse model.

In conclusion the answer lies as -Due to a single oxygen atom difference in sialic acids, typhoid toxin affects humans while other mammals are resistant.

-Dixy