Diphtheria

Diphtheria

Definition - It is an acute infectious bacterial disease caused by corynebacterium diphtheriae found in clinical forms i.e. Anterior nasal, Pharyngotonsiller (faucial) and Laryngotracheal. The bacteria produces a powerful exotoxin locally and it is responsible for the formation of pseudo-membrane, local oedema and lymphadenopathy with sign of toxaemia.

Agent factors -

AGENT - Corynebacterium diphtheria. It is a gram +ve non-motile organism and it has no invasive power but produce a powerful exotoxin.

There are two types of strains – 

(a) Pathogenic strain – Gravis, mitis, belfanti and intermedius. 

(b) Non-pathogenic strain – They are capable to change into pathogenic strains due to ß-phase.

INFECTIVE MATERIAL – Nasopharyngeal secretion and contaminated wounds, fomite and dust.

SOURCE OF INFECTION - (a) Case (5%) – mild and frank clinical cases. (b) Carrier (95%) – Temporary and chronic carrier

PERIOD OF COMMUNICABILITY – 14-28 days from onset of disease or till two throat cultures are negative

Host factors -

AGE – Usually 1-5 years

SEX – Equal in both sexes.

IMMUNITY – Passive immunity formation up to few months of birth (70% herd (group) immunity up to age of 3 years and 90% up to 5 years.

ENVIRONMENTAL FACTORS – Winter season is favorable but cases can be seen throughout the year.

Incubation Period - 2-6 days

Mode of transmission – Direct droplets, droplet nuclei and freshly contaminated fomite

Clinical features -

PHARYNGO-TONSILLAR – Sore throat, mild to moderate fever (On examination – Erythema at pharynx and tonsils, formation of pseudo-membrane “greenish black or bluish white” initial can be wipe off easily but later it can’t be wipe off and attempt can cause bleeding), submandibular edema and localized lymphadenopathy (bull neck deformity)

LARYNGOTRACHEAL (It is always secondary) - Croupy cough and hoarseness of voice

NASAL - Formation of pseudo-membrane in nasal mucosa.

NON-RESPIRATORY DIPHTHERIA - Cutaneous diphtheria (infective material - come in contact with wound), conjunctival diphtheria and vulvar diphtheria.

Schick test -

Schick test	Diphtheria anti-toxin (test arm)	Inactivated diphtheria anti-toxin (control arm)
+ve	Test arm +ve	Control arm –ve (susceptible)
-ve	Test arm –ve	Control arm –ve (immune)
Pseudo-positive (false)	Test arm –ve	Control arm +ve (allergic)
Combined	Test arm +ve	Control arm +ve
0.2 ml toxin given on forearm and 5-10 mm erythema (red area) indicate +ve test.

Prevention and control –

1.      Early detection

2.      Isolation

3.      Treatment

4.      Vaccination – (dose of vaccine is 0.5 ml IM, 6,10, 14 weeks, 15-24 month and 5 year)

a.       Single vaccine

                                                              i.      Formal toxoid (FT)

                                                            ii.      Alum precipitated toxoid (APT)

                                                          iii.      Purified toxoid aluminium phosphate (PTAP)

                                                          iv.      Purified toxoid aluminium hydroxide (PTAH)

                                                            v.      Toxoid anti-toxin floccules (TAF)

b.      Combined or mixed vaccine

                                                              i.      Diphtheria pertussis tetanus vaccine (DPT)

                                                            ii.      Diphtheria tetanus toxoid (DT)

                                                          iii.      Diphtheria tetanus toxoid (dT – adult type)

c.       Antisera – Diphtheria antitoxin

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