32. Epidemiology and prevention of infections transmitted through the skin

Wound infections

Tetanus

Clostridium tetani
Epidemiology
- Present worldwide
- More common in rural communities and agricultural regions
Transmission
- Bacterium produces spores
- Contaminated objects in contact with wounds or ulcers
- Penetrating injury from contaminated object (nails)
- No person-to-person
Reservoir:
- Soil
- Animal GI tract and faeces
Toxins
- Tetanolysin – haemolyses. No pathological activity
- Tetanospasmin – causes symptoms of tetanus
Clinical features
- Fatality 10 – 20% with therapy (without: 50%)
- Generalized tetanus
  - Most common form
  - Descending muscle rigidity
  - Laryngospasm, breathing difficulty
  - Risus sardonicus – smiling grin
  - Opisthotonus – spasm of the back muscles
- Localized tetanus
  - Tetanus symptoms in the area of the infection only
  - Rare, very good prognosis
- Cephalic tetanus
  - Rare, poor prognosis
  - If infection occurs at head or ear
  - Dysfunction of cranial motor nerves
- Neonatal tetanus
  - Neonate exposed during birth
  - Very poor prognosis
Treatment
- Supportive care
- Protection of the airways
- Neutralization of toxins (passive immunization)
Prevention
- Toxoid vaccine (DTaP)
  - Childhood vaccine
  - However, protection only lasts approx 10 years, so it’s recommended to get a booster shot for high risk groups (dirty wounds, military) if it’s more than 10 years since last booster
- Clean birth

Gas gangrene

Clostridium perfringens, other clostridium spp.
Risk factors
- Peripheral artery disease
- Diabetes mellitus
Transmission
- Spores enter wounds and thrive in anaerobic environment
- Often seen after trauma (accidents) or postoperative
Prevention
- Clean any skin injury thoroughly
- Remove foreign objects from wounds
- Give post-exposure antibiotics

Epidemic keratoconjunctivitis

Adenovirus
Transmission
- Direct contact with eye secretions
- Indirect contact by contaminated ophthalmic instruments
Epidemics
- Schools
- Hospitals
- Nursing homes
- Etc.
Prevention
- Good hygiene
- Don’t use the same ophthalmic instruments in patients with symptoms of keratoconjunctivitis and healthy patients

Trachoma

Pediculosis – lice infestation

Epidemiology
- Found in all countries and climates
- More common in developing countries
Transmission
- Direct contact
- Indirect – via sharing objects like combs, clothes, hats
Three types
- Pediculus capitis – head louse
  - Grow in hair
  - Lay eggs at the scalp
- Pediculus corporis – body louse
  - Lives in clothing, not in body hair
- Pthirus pubis – pubic louse
  - Grow in pubic hair
  - STD
Lice can be the vector of
- Rickettsia prowazeki (typhus)
- Borrelia recurrentis (relapsing fever)
Clinical features
- Itching
Prevention
- Don’t share stuff
- Avoid head-to-head contact
- Wash clothes at 60

Scabies

Sarcoptes scabiei var hominis
A mite that burrows into the epidermis, where they live and deposit eggs
Epidemiology
- Occurs worldwide
- More common in developing countries
- Often affects children and sexually active adults
- In crowded conditions
Reservoir
- Humans
Transmission
- Direct contact
Symptoms
- Itching
- Pimple-like rash
- Burrows in the skin
Prevention
- Avoid direct contact with infected
- Objects an infected person has used should be washed