Epidemiology Of Tetanus Flashcards
What is the causative agent of tetanus?
Clostridium tetani
- gram positive bacilli
- obligate anaerobes
- with a drumstick appearance
- universally present in the soil
Where is C. tetani located in its dormant phase?
Extremely stable bacterial spores commonly found in cultivated soil (least frequently in virgin soil).
- Spores can also exist in environments as diverse as animal excrement, house dust, and the human skin and colon
Physiochemical properties of C. tetani?
Highly resistant to heat and most chemical agents including ethanol, phenol, and formalin.
- they can be destroyed by iodine, glutaraldehyde, and hydrogen peroxide or autoclaving at 121oC under 15 PSI pressure
Length of dormant phase?
Spores can remain infectious for more than 40 years in soil
- If the spores enter a wound that penetrates the skin and extends deeper than oxygen can reach, they germinate and produce a toxin that enters the bloodstream
Vegetative form produces which 2 exotoxins?
- TETANOLYSIN: Unknown role in pathogenesis of tetanus
- TETANOSPASMIN: aka Tetanus Toxin is a potent neurotoxin which blocks Inhibitory neurotransmitters in the central nervous system and causes the muscular spasms typical of generalized tetanus (potency comparable to botulinum toxin)
Reservoir for C. tetani?
- Intestine of herbivorous animals and excreted in their faeces e.g., horses, goats and sheep
- Soil and dust
Period of communicability of C. tetani?
None because it is not transmitted from person to person
Hosts for tetanus?
- Can occur at any age
- In developed countries largely restricted to the elderly
- In developing countries common in newborns or mothers due to
unclean deliveries and poor postnatal hygiene - Tetanus in children and adults following injury is also a public
health concern - Gender: males>females
Risk factors?
- Occupation
- Pregnancy – delivery or abortion
- Soil, agriculture and animal husbandry
- Injuries, in- or outdoor
- Customs and habits
- Lack of primary care
Transmission?
- Not communicable
- Entry into the body through any form of injury
- Neonatal tetanus almost always from unclean birthing practices
especially application of contaminated material to umbilical stump - In children and adults both acute and chronic infections occur
- Puncture and deep wounds more likely to result in infection than
superficial abrasions
Incubation period?
- 3 - 21 days, 6-8 days common
- In neonates, 4-14 days, average 7 days
- The farther the injury site from the CNS the longer the incubation
period - Severity of disease inversely related to length of incubation period
Pathophysiology?
- C tetani spores are noninvasive and usually require compromise in host skin defenses
accompanied by foreign bodies and/or other bacteria for inoculation to occur - Although C tetani wound contamination is common, germination and conversion to the toxin
producing vegetative form only occurs in wounds with C tetani conducive environment i.e., low
oxidation-reduction potentials, especially where there is devitalized tissue. - Tetanospasmin reaches CNS (blood borne) to periphery nerves or retrograde intraneuronal
transport. - Blood borne tetanospasmin does not cross the blood brain barrier
- Tetanospasmin in CNS migrates to cell bodies of inhibitory nerves and prevents release of
neurotransmitters glycine and γ-aminobutyric acid (GABA). - With inhibitory control suppressed, resting firing rate of motor neurons increases leading to
muscular rigidity, tetanic muscular spasms and sympathetic overactivity.
Generalised clinical presentations?
Most common form
1. Spasm of masseter muscles (LOCKJAW) and grimace like
appearance of the face (RISUS
SARDONICUS) are early signs
2. Spasms of the muscles of the
abdomen, neck, back and thorax
(OPISTHOTONOUS position).
3. Tonic seizures if severe
Note:
- patient does not lose consciousness
- Can be stimulated by external stimuli
- Can continue for weeks, and recovery
can take several months
- elevated temperature, sweating,
hypertension and tachycardia
common
Localised clinical presentations?
Less common.
1. Stiffness and rigidity of muscles around infection site
2. Recovery is spontaneous, only 1%
fatal.
3. It can be prodrome of generalized tetanus
Cephalic clinical presentations?
Rare form
1. Presents as trismus plus paralysis of
one or more cranial nerves, commonly
the facial nerve
2. Characteristic involvement of
cranial nerves
