DIPHTHERIA – OVERVIEW.

Diphtheria is an infectious disease caused by the bacterium Corynebacterium diphtheria.

The bacteria primarily infects the mucosal membranes of the throat and nose. It also infects the skin but not as often as it infects the upper airways. Not only that but the bacteria produce a toxin which also affects other organs.

Due to early immunization and vaccination against diphtheria, mortality and morbidity of diphtheria have reduced. With that notwithstanding, diphtheria is still a significant child health problem in countries with poor Expanded Program of Immunization (EPI) coverage initiated by the World Health Organization (WHO) to vaccinate children all over the world. In 2016, about 7,100 cases of diphtheria were recorded by the World Health Organization.

The infection has an acute onset and may present as a sore throat, low fever, swollen glands in the neck, and malaise. On inspection, one of the hallmark sign of diphtheria is a layer of thick, grey material covering the back of the throat. This causes difficulty in breathing in most cases as a result of blocking the airway.

Diphtheria can also be very fatal as a result of the toxins produced by the bacteria which affect organs such as the heart, kidney, nervous system, etc.

Diphtheria is curable when diagnosed early and treated with antitoxins and antibiotics.

 TRANSMISSION

C. diphtheriae infection is contagious and is usually spread through direct physical contact or through droplet secretions from the cough or sneeze of infected individuals. Its main routes of transmission are as follows:

1. Airborne: Breathing or inhalation of droplet secretions from coughs or sneezes of infected individuals. Diphtheria infection spreads efficiently in this route, especially in crowded and slummy conditions.

2. Contact with infected items or persons: Infection is occasionally spread from handling items used by an infected person on which bacteria-laden secretions have been deposited. This includes; drinking from the infected person’s unwashed glass, eating with an infected person’s unwashed spoon, etc.

One can also be infected by coming in contact with or touching an infected wound.

People who have been infected by the diphtheria bacteria can be asymptomatic and carriers of the infection if not treated.

SYMPTOMS OF DIPHTHERIA

Usually, symptoms present two or five days after one becomes infected. Others may also be asymptomatic (without symptoms) as a carrier.

Initially, there are flu-like symptoms such as;
1. Low-grade fever
2. Headache
3. Sore throat
4. Weakness
5. Malaise

Eventually, as the disease progresses, the symptoms it presents with are;

1. Difficulty swallowing
2. Throat hoarseness
3. Swollen neck (enlarged neck lymph nodes)
4. Coughing
5. Shortness of breath

Once the bacteria toxins enter healthy tissues, it destroys them within 3-5 days. Its presence in the pharynx (throat) causes the buildup of a thick, grey covering in the back of the throat.

On some occasions, some patients have skin involvement, resulting in skin ulcers. Ulcers are usually covered with a grey membrane. This is known as Skin (Cutaneous) Diphtheria.

RISK FACTORS

1. Children and adults who have not been immunized for diphtheria.
2. People living in crowded and poor hygienic conditions.
3. Travelling to a diphtheria endemic area.

INVESTIGATIONS

Diphtheria is often diagnosed by physical examination and patient’s history.

The history helps you to confirm if the person has an up-to-date immunization and also rule out all other risk factors.

An isolated culture of C. diphtheriae in a culture medium and the identification of the presence of a toxin is necessary for making a diagnosis.

It is advised that, even if diphtheria is suspected, the patient must be treated. However, the culture of Corynebacterium from the patient yields a definitive diagnosis.

If doctors suspect heart problems, electrocardiography can be ordered to confirm the diagnosis.

COMPLICATIONS

In as much as diphtheria can be easily treated, if treatment is delayed, it can lead to complications such as;

1. Sepsis: A response of the body’s immune system to an infection that results in organ dysfunction or failure.

2. Heart-rhythm problems due to potential damage to heart muscles.

3. Dyspnea (difficulty in breathing).

4. Paralysis (inability to move a part or whole of the body).

5. Nerve damage.

These can all be fatal if not managed promptly and tactically.

TREATMENT

Treatment is usually targeted at the bacteria and its toxin. Antibiotics are given to kill the bacteria while antitoxins are used to counteract the toxins.

It is important to note that, the CDC recommends antibiotics such as:

1. Erythromycin as a first-line treatment for patients above 6 months of age.

2. Intramuscular (IM) penicillin is recommended as a first-line drug for patients who cannot take erythromycin.
Patients usually become non-infectious after about 48 hours of effective antibiotic therapy

Antitoxin

This is the second kind of treatment for the disease. This aims at reducing the progression of the disease by binding to diphtheria toxins which haven’t bound to human cells. This antitoxin is derived from horses and as such, patients who are allergic should not be treated with it.

PREVENTION

Diphtheria is very preventable as there is an available vaccine. WHO recommends a 3-dose primary vaccination series with diphtheria containing vaccine followed by 3 booster doses.

Prior to the availability of antibiotics, diphtheria was common amongst young children. Today, the disease is not only treatable but is also preventable with a vaccine.

The diphtheria vaccine is usually combined with vaccines for tetanus and whooping cough (pertussis). The three-in-one vaccine is known as diphtheria, tetanus, and pertussis vaccine. The current version of this vaccine is known as the DTaP vaccine for children and the Tdap vaccine for adolescents and adults.

Diphtheria, tetanus, and pertussis vaccine is one of the childhood immunizations that doctors recommend worldwide.

Vaccination consists of a series of five shots, specifically administered in the arm or thigh. DTaP is given to children at these ages; 2 months, 4 months, 6 months, 15 to 18 months, and 4 to 6 years.

The diphtheria vaccine is effective at preventing diphtheria. But there may be some side effects which ranges from person to person. Some children may have a mild fever, fussiness, drowsiness or tenderness at the injection site after a DTaP shot.

Rarely, the DTaP vaccine causes serious complications in a child, such as an allergic reaction (hives or a rash develops within minutes of the injection), seizures or shock (complications that are treatable).

Some children, such as those with epilepsy or another nervous system condition might not qualify for the DTaP vaccine.

Booster Shots

After the initial series of immunizations in childhood, you need booster shots of the diphtheria vaccine to help you maintain immunity. That’s because immunity to diphtheria fades with time.

Children who received all of the recommended immunizations before age 7 should receive their first booster shot at around age 11 or 12. The next booster shot is recommended 10 years later, then repeated at 10-year intervals. Booster shots are particularly important if you travel to an area where diphtheria is common.

The diphtheria booster is combined with the tetanus booster—the tetanus-diphtheria (Td) vaccine. This combination vaccine is given by injection, usually into the arm or thigh.

Tdap is a combined tetanus, diphtheria and acellular pertussis (whooping cough) vaccine. It’s a one-time alternative vaccine for adolescents aged 11 through 18 and adults who haven’t previously had a Tdap booster. It’s also recommended for anyone who’s pregnant, regardless of previous vaccination status.

EPIDEMIOLOGY

Diphtheria was one of the leading causes of childhood death in the years before vaccines were introduced. However, after the diphtheria toxoid vaccine was invented in 1923, the incidence has declined drastically.

Globally, the incidence rate became better after EPI implementation began in 1977 with the diphtheria vaccine as one of the original six EPI antigens.

In the 1990s, there was a dramatic increase in incidence representing a widespread epidemic in the Russian Federation and the former Soviet Republics, with about 157,000 cases and 5,000 deaths.

Reasons for the outbreak were reported as in falling support for vaccination among both parents and health care providers, with over 50 diagnoses listed as contraindications to vaccination and up to 50% of children in some areas receiving the less immunogenic adult formulation Td instead of the recommended DTP due to concerns about complications.

According to WHO, data for diphtheria reported at a 5-year averages shows declination from about 10,000 cases per year during 2000- 2004 to 5288 per year during 2005-2009. However, since 2009 global annual reported cases have levelled off.

Globally, diphtheria incidence is highest in the South-East Asia region, especially since 2005. Reported cases reported from the European and African regions have decreased.

Among countries with the top 10 case counts since 2000, India has the largest number of reported cases, with Indonesia and Nepal being the other main sources of diphtheria cases from this region.

A large number of cases was also reported from Nigeria in 2000-2004 but it does not figure prominently in the other time periods. However, this is likely an artefact of poor surveillance and reporting.

Two other countries also had large outbreaks during this period; Madagascar and Papua New Guinea.