Diphtheria: Causes, Symptoms, Diagnosis ,prevention and control
It is an acute infectious and communicable disease caused by Corynebacterium diphtheria and characterized in its typical form by the presence of membrane (pseudomembrane) in the throat and generalized toxaemia. Diphtheria is a localized infection of the upper respiratory tract that may be associated with delayed systemic manifestations Chiefly, laryngeal obstruction and peripheral neuropathy. The three main types of diphtheria are anterior nasal, tonsillar and pharyngeal: there may be other clinical types, such as laryngeal and cutaneous diphtheria. Laryngeal diphtheria is serious in infants and you, while nasal diphtheria is mill and often chronic.
Occurrence: In the developed countries the incidence of diphtheria has declined remarkably; even in some developing countries including Bangladesh, as a result of expanded programm of immunization, the disease incidence has been showing a declining trend.
Agent : Corynebacterium diphtheriae is a gram-positive bacillus which is killed by heating at 58°C for 10 minutes and readily by most common disinfectants. However, it is resistant to drying, may be isolated form the dust around the beds in different wards . Antigenically claviger may be divided into 3 types— gravis, intermedius and mitis. The biotype mitis appears to be prominent in endemics but when the disease is epidemic, there is usually a change of type to gravis or intermedius. There is cross immunity between the three types. Disease is prodcued by the production of a powerful exotoxin. Non-toxigenic strains rarely produce local lesions. Mortality rates are 7-8% for gravis and intermedus.
Host: The disease occurs mostly in school going children. Although all ages may be affected, mortality is high in the extremes of age. There is no sex predilection for diphtheria. A large proportion of population in developing countries seem to acquire active immunity through inapparent infection. Infants born to immune mothers derive maternal antibodies which protect them during the first few months of their life.
Environment: Overcrowding and poor socioeconomic conditions predispose to both ease of spread and morbidity. Cases of diphtheria occur in all seasons, but spread of the disease is more common in the winter months.
Reservoir: Man. is the reservoir. Sub clinical infections are fairly common and there are carrier states. both healthy and convalescent. With regard to infectivity it is said that skin and ear carriers may contaminate. The throat or nose carriers, although occurrences of these types may not be as common as nasal types.
Incubation period: This is usually 2-6 days. Mode of transmission: The disease is transmitted by way of contact with a case of diphtheria or carrier, and more rarely with articles soiled with discharges from lesions of infected persons. The causative organism enters the host mainly through the respiratory tract or through ingestion of contaminated milk or similar food items and excreted through the respiratory tract.
Susceptibility: Infants born of immune mothers are relatively immune. Recovery form a clinical attack is not always followed by lasting immunity; immunity is often acquired through inapparent infection.
Diagnosis is confirmed by bacteriological examinations—culture and demonstration of an organism in stained smears. However, a clinical diagnosis which should form the basis for starting immediate treatment, is based on observation of a whitish membrane, specially if extendng to the uvula and soft palate.
Prevention and Control of Diphtheria
Active immunization against diphtheria is the best method of prevention. For the purpose of vaccination, antigen mixtures, e.g., DPT or DT toxoids may be used. However, in the national EPI programme triple antigen (DPT) is recommended. Protection conferred by the primary series of 3 doses is excellent. A
booster dose one year after the primary series may be considered. For effective control, the following measures should be taken: (a) Active search for cases and carriers among the contacts; (b) All cases and carriers to be isolated till the throat swabs (two swabs taken 24 hours apart) are negative; (c) Concurrent disinfection of all articles in contact with patient, and all articles soiled by discharges of patient: (d) Treatment. Antitoxin therapy must be instituted rapidly upon making a clinical diagnosis without awaiting the report on a throat swab. Antitoxin therapy is the only specific treatment to prevent further fixation of toxin to tissue receptors, since fixed toxin is not neutralized by antitoxin. Depending on the severity, 20,000 to 120,000 units of horse-serum antitoxin should be administered intravenously after an initial test dose to exclude allergic reaction. For mild cases 4,000 to 8,000 units i.m. will suffice. Procaine penicillin 1.2 g i.m. once daily for 7 days should be administered concurrently to eliminate the organisms and thereby remove the source of toxin production.
Institutional control of diphtheria. When diphtheria has broken out in a school or community, the whole population should be subjected to Schick Tests and throat swab tests.