Gram Positive Bacilli
Not true about Clostridium tetani?
|A||It is dormant and present in soil and man and animal intestine|
|B||It is transmitted through infected wounds|
|C||It occurs more in winter and dry season|
|D||Herd immunity does not contribute|
It occurs more in winter and dry season
a. Many spp. of Clostridium, especially Cl.perfringens and Cl. tetani are found normally in human and intestine. Cl. tetani spores can persist in soil and remain dormant for several years.
b. Most cases of tetanus result from small puncture wounds or lacerations which become contaminated with C. tetani spores that germinate, multiply and produce toxin (tetanospasmin).
c. Symptoms appear due to migration of toxin along neural paths from local wound to sites of action in the CNS.
d. There it becomes rapidly fixed to gangliosides at the presynaptic inhibitory motor nerve endings, and is taken up into the axon by endocytosis. The effect of the toxin is by selective cleavage of a protein component of synaptic vesicles, synaptobrevin II and thereby block the release of inhibitory neurotransmitters (glycine and gamma-amino butyric acid) across the synaptic cleft, which is required to inhibit nervous impulse.
e. Tetanus is more common in developing countries where the climate is warm and in rural areas where soil is fertile and highly cultivated.
f. Herd immunity only applies to diseases that are contagious. It does not apply to diseases such as tetanus in which there is no human to human transmission.