Pertussis

Definition   

Pertussis is a highly contagious bacterial disease which affects the respiratory system and produces spasms of coughing that usually end in a high-pitched sounding deep inspiration (the "whoop").

Causes, incidence, and risk factors   

• Pertussis caused by Bordetella pertussis bacteria.
• Spread through the air by respiratory droplets.
• The incubation period is usually 7 days.
• Contagious period 7days to 3 weeks.

Incidence

• Prior to vaccine: USA 175,000 cases per year
• By 1970: <5,000 per day
• 1980-1999: Increasing incidence to 8.000 per year and growing.
• Traditionaly children < 5 year of age largest group with 14% > 20 years of age. This prorportion is changing with children<10 accounting for 58% and now 42% of cases in persons > 10 years of age.
• Many children are not immunized because of parental resistance (fear of complications-religious belief).

Communicability:

High: 70%- 100% attack rate in non immunized.

Description:

Whooping cough can affect people of any age. Prior to the advent of widespread immunization, the disease occurred mostly in infants and young children. Now a higher percentage of cases are seen among adolescents and adults.

 The bacteria invade the nose and throat, trachea, and  lungs. The infection usually lasts 6 weeks but the cough can go on for months.

The cough is characterized by repeated coughing, 2 or 3 coughs without inhaling then a characteristic inspiratory whoop with or without cyanosis-loss of consciousness-vomiting.

Recovery begins about four weeks after the onset of symptoms and may take several weeks to months  Immunization may moderate the course of pertussis when it does not produce complete immunity.

Symptoms   

• Cold symptoms

• cough, severe, may be dry or may produce sputum
• slight fever (102 F or lower)
• severe coughing attacks
  • ends in a high-pitched, crowing sound when inhaling, or ends in a high-pitched "whoop" (whooping cough)
  • coughing spell (paroxysm) may end in a momentary loss of consciousness
  • cough with difficulty breathing
• vomiting during a severe bout of coughing
• diarrhea
• choking spells in infants
• choking that occurs when emotional

Signs and tests   

Tests may include:

• a nasopharyngeal and oropharyngeal throat swab culture
• a blood count (CBC) with an elevated white blood cell count characterized by large numbers of lymphocytes (lymphocytosis)
• serologic (blood) tests for Bordetella pertussis
• immunologic tests

Treatment   

Erythromycin to be given within 2 weeks of onset

Hospitalization for  severe cases. Apnea monitoring.

Supportive care ( IV fluids-humidified -air-anti-inflammatory mediactions).

Prognosis  

In older children, the prognosis is generally very good. Infants are the group at the highest risk with 0.5% to 1% mortality

Complications   

• slowed or stopped breathing (apnea)
• pneumonia
• convulsions due to lack of oxygen can cause permanent brain damage
• nose bleeds
• ear infections
• brain damage from lack of oxygen (anoxic encephalopathy)
• bleeding in the brain (cerebral hemorrhage)
• seizure disorder (permanent)
• developmental retardation

Prevention:

During epidemics, unimmunized children under the age of seven should be excused from school and public gatherings for 14 days after the last reported exposure and isolated from anyone known or suspected to be infected.

Cases of the disease are reported to public health officials by health care providers so that health warning announcements and other preventative measures can be taken. Pertussis is now recognized more often in adolescents and adults.

Vaccine:

Whole Cell vaccine: Developped in 1930’s – suspension of formalin-inactivated B. Pertussis cells.

Series of four dosesof DTP: 70 to 90% effective

Immunity would decrease with time

Complications included fever – redness – seizures – encephalopathy ( rarely).

Replaced by Acellular vaccine.

Acellular vaccine: Licenced in 1991. Purified , inactivated components of B. Pertussis

DtaP schedule: 2mo-4mo-6mo-15-18mo.

Efficiency 70 to 85%.

Adverse Reactions:

Mild: fever – redness . Rate 3 to 5 % .

Moderate: febrile seizures – hypotonic episodes

No distinct syndrome resuslting from vaccine administration ( SIDS- transverse myelitis- )

Contraindication:

Allergic reaction or encephalopathy following  vaccine component injection.

Precautions in febrile patient or children with history of febrile seizures-collapse – persistent crying after vacciantion.

Storage:

Stored between 2 and 8 degree c

Dr Paul Assad

REF:

CDC Epidemiology and prevention of vaccine-preventable diseases, 6^th edition –Jan 2000