Viral hemorrhagic fevers: neurologic complications
Aug. 17, 2021
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Pertussis or whooping cough is an important cause of infant death worldwide. Pertussis is caused by the organism Bordetella pertussis, a gram-negative bacillus. In 2019, the World Health Organization estimated 132,754 cases of pertussis globally, 95% of which were in developing countries. Severe complications of pertussis include pneumonia, encephalopathy, and meningoencephalitis. Central hypoventilation secondary to pertussis encephalopathy occurring during childhood has been described in an isolated case. An increased risk of epilepsy was noted in children with hospital-diagnosed pertussis compared with the general population. Infants who survive critical pertussis illness often have poor neurocognitive development. In the past, several neurologic complications were identified in infants immunized with the whole-cell pertussis vaccine, including acute encephalopathy, seizures, hypotonic-hyporeactive episodes, inconsolable crying, and anaphylactic reactions. Experts now believe that there is no convincing evidence proving an association between the pertussis vaccine and persistent brain damage. Vaccine encephalopathy is, in fact, an inherited genetic defect of the SCN1A gene that codes for the voltage-gated neuronal sodium channel. In fact, children who presented with earlier diagnoses of alleged vaccine encephalopathy in infancy were diagnosed years later with Dravet syndrome. The prenatal maternal tetanus, diphtheria, and acellular pertussis vaccination is safe, and the vaccine is not associated with an increased risk of autism spectrum disorder in offspring. That vaccine triggers autoimmune encephalitis remains unconfirmed. Based on a review of current literature, the author presents an overview focusing on pertussis encephalopathy and vaccine encephalopathy; in addition, he also discusses the epidemiology, pathogenesis, pathology, diagnosis, and treatment of pertussis.
• Encephalopathy is a rare complication of pertussis.
• Several neurologic complications have been described with the pertussis vaccines, particularly with whole-cell vaccines.
• There is no convincing evidence proving an association between vaccine and persistent brain damage.
• Vaccine encephalopathy is, in fact, caused by an inherited genetic defect of the voltage-gated neuronal sodium-channel gene.
In 1640, Guillaume de Baillou provided the first detailed description of whooping cough as a distinct entity when he described an epidemic in 1578 (29). Kohn suggests that the description of the Perinthus cough by Hippocrates (around 400 BC) might possibly be whooping cough or a mix with other diseases, such as viral respiratory infections. In 1682, Thomas Willis was the first person to recognize the epidemic nature of pertussis. Bordet was credited with first describing the bacteria Bordetella pertussis. In 1900, he observed numerous coccobacilli in respiratory secretions collected from his own daughter who was suffering from pertussis. In 1906 Bordet and Gengou cultured Bordetella pertussis. Encephalopathy was first described as a complication of pertussis infection in 1877. Sydenham first used the term “infantum pertussis” in 1679.
Following the widespread use of whole-cell pertussis vaccines containing diphtheria and tetanus toxoids in the 1940s, the mean incidence rates of pertussis decreased from 150/100,000 to approximately 1/100,000 by 1980. Vaccine encephalopathy was first identified in a report by Byers and Moll in 1948. Eight efficacy trials evaluating acellular pertussis vaccines were conducted in the early 1990s; the results were reported in publications from 1995 to 1998. In 1996, less immuno-reactogenic diphtheria, tetanus, and acellular pertussis vaccines were licensed and recommended for routine use in infants and young children, replacing whole-cell pertussis and diphtheria and tetanus toxoid vaccines completely in the United States. Acellular pertussis vaccines were not associated with enhanced risk of neurologic complications.
The British National Childhood Encephalopathy Study was established in 1976 as an independent scientific enquiry into severe acute neurologic illnesses associated with pertussis vaccine. The study concluded that there was no significant association between vaccination and brain disease in most instances of encephalopathy, unexplained coma, convulsions lasting more than 30 minutes or associated with persistent complications, infantile spasms, or Reye syndrome in previously normal children within 7 days of immunization (20; 29). It was earlier suggested that pertussis vaccination might trigger the development of Dravet syndrome in children who have an SCN1A mutation.
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