Paper II
Question
Describe the laboratory diagnosis and prophylaxis of tetanus
Answer
Tetanus (caused by Clostridium tetani)
Laboratory diagnosis: tetanus is primarily a clinical diagnosis (based on characteristic muscle rigidity, trismus/lockjaw, risus sardonicus, and opisthotonus in a patient with a compatible wound history), since laboratory confirmation is often unhelpful/unreliable:
- Gram stain of wound material — may show Gram-positive bacilli with characteristic terminal, round spores giving a “drumstick” appearance, though C. tetani is often not detectable directly in the wound.
- Anaerobic culture of wound material — on media such as Robertson’s cooked meat medium; frequently negative even in confirmed clinical tetanus, since the disease is toxin-mediated and the organism may be present only in very small numbers or already cleared by the time of diagnosis.
- Toxin detection — mouse neutralization/bioassay for tetanospasmin, technically demanding and not routinely used clinically.
- Given these limitations, clinical diagnosis based on characteristic signs and a compatible wound/injury history remains the primary basis for diagnosis, without waiting for laboratory confirmation.
Prophylaxis:
- Active immunization — Tetanus toxoid (TT), part of the routine DPT/Td vaccination schedule, given in a primary series in infancy with periodic booster doses (including a booster in pregnancy to protect against neonatal tetanus via passive transfer of maternal antibody).
- Passive immunization — Tetanus Immunoglobulin (TIG), providing immediate passive protection, indicated for wound management in individuals with incomplete/uncertain/absent vaccination history, particularly for tetanus-prone wounds (deep, contaminated, devitalized wounds).
- Wound management — thorough wound cleaning/debridement of devitalized/necrotic tissue to eliminate the anaerobic environment favouring C. tetani germination, a critical adjunct to immunoprophylaxis.
- Post-exposure prophylaxis decision is based on both the wound category (clean minor vs tetanus-prone) and the patient’s vaccination history, per standard tetanus-prophylaxis guidelines/tables, determining whether TT, TIG, or both are indicated.
- Elimination of Maternal and Neonatal Tetanus (MNT) — a public health strategy centred on ensuring adequate maternal tetanus toxoid immunization and promoting clean/hygienic delivery and cord-care practices, given the historically high burden of neonatal tetanus in inadequately immunized populations.