Botulinum toxin type H- the deadliest known toxin- has been discovered in the feces of a child suffering from botulism. The toxin's DNA hasn't been released to the public as it has no antidote.  

Botulinum toxin is one of the most poisonous neurotoxin known to man. Injecting just 2 billionths of a gram of the substance is enough to kill an adult. Currently, researchers know about the existence of seven serotypes of the toxin- A, B, C1, C2, D, E, F and G. All of them are produced by the bacterium Clostridium botulinum and damage human body by blocking acetylcholine, a neurotransmitter, leading to muscle paralysis.

The new serotype of the toxin- type H- was reported by Stephen Arnon and colleagues at the California Department of Public Health, according to the New Scientist. It has been over four decades since the discovery of the other similar toxins.

There is a lot of interest in Botulinum toxin, both for its toxicity and medical benefits. Botox (onabotulinumtoxinA) is currently used for crow's feet linesbladder control and even in migraine treatment. Many scientists believe that the toxin could be used by extremists as a bio-weapon.

The study team decoded the bacterial strain that produces the deadly substance. According to the New Scientist, this is the first time a genetic sequence has been kept hidden from public database over security concerns.

Victims of the known types of Botulinum toxin are treated with monoclonal antibodies, which are immune proteins produced in lab and react with the toxin-type.

In the present study, researchers conducted toxicity tests on a group of mice. They used the standard antibodies provided by US Centers for Disease Control and Prevention (CDC) and found that few of them reacted weakly with the new toxin and none of them were able to protect the test mice.

Arnon and colleagues then tried to grow type- H antibodies in rabbits.  These antibodies protected mice from the toxin, but researchers had to use a very high dose, The New Scientist reported.

The study is published in the Journal of Infectious Diseases.