Picorna virus Dr R S Gopika Prof Ho

Picorna virus Dr. R. S. Gopika Prof & Ho. D Dept Pathology SKHMC

Picorna viruses • • Family picornaviridae very small - 28– 30 nm size Non enveloped viruses Two major groups: ▫ Enteroviruses ▫ Rhinoviruses

Enteroviruses: Transmitted by fecal-oral route. However, they do not cause intestinal symptoms, but are associated with systemic manifestations. Examples: ○ Polio (3 serotypes) ○ Coxsackie A & B ○ Echovirus ○ Enteroviruses etc Rhinoviruses: Transmitted by respiratory mode. It is the MC cause of common cold.

Picorna virus – poliovirus • • RNA viruses with an icosahedral capsid. The viral particle is about 30 nm in diameter polio= gray matter Myelitis= inflammation of the spinal cord

Serotypes • Type 1 – Most common serotype to cause epidemics. Only serotype that is endemic currently in the world. • Type 2 It is the most antigenic and hence easiest serotype to be eradicated. No natural case has been reported since 1999. • Type 3 No natural case caused by serotype-3 has been reported since 2013.

Resistance: In feces – for months at 40º C - years at 200º C • Inactivated by heat and chlorination

• Natural infection occurs only in humans • Mo. T Feco-oral route • Most vulnerable age group 6 months to three years • M: F ratio- 3: 1 • Seasonal. More during rainy season

Pathogenesis • IP: 3 -6 days(4 - 35 days) • Transmitted by oral-fecal contact. • Person-to-person spread is the most common means of transmission, followed by contaminated water. • Receptor: Viral entry into the host cells is mediated by binding to CD 155 receptors present on the host cell surface.

Pathogenesis • Virus is present in blood for 3– 5 days. • It is shed from the oropharynx for up to 3 weeks and from the GI tract for up to 12 weeks after infection

Spread to CNS/spinal cord: is either by - Hematogenous spread(MC), - Direct Neural spread (occurs following tonsillectomy, where the virus may spread via glossopharyngeal nerve present in the tonsillar fossa). Site of action: Motor nerve ending - anterior horn cells of the spinal cord

Pathology Neuron degeneration: Earliest change in neuron is the degeneration of Nissl body (aggregated ribosomes, normally found in the cytoplasm of neurons). • Pathological changes are always more extensive than distribution of paralysis. • Destroy the Anterior horn cells of the Spinal Cord • Do not Multiply in Muscles only muscles manifest with weakness and flaccid paralysis result is secondary. • Occasionally produce Myocarditis, Lymphatic hyperplasia

c/m • IP- 7– 14 days. It manifests in four forms: • Inapparent infection: Following infection, the majority (91– 96%) of cases are asymptomatic. • Abortive infection: 5% of patients develop minor illness (fever and malaise). • Nonparalytic Poliomyelitis: Seen in 1% of patients, presented as aseptic meningitis. • Paralytic Poliomyelitis : is the least common form (< 1%), flaccid paralysis

According to Symptoms three basic patterns of polio infection - subclinical infections - nonparalytic and - paralytic

Subclinical Infection -Symptoms • • • General discomfort or uneasiness (malaise) Headache Slight fever Sore throat Vomiting

Nonparalytic/abortive polio Signs and symptoms of non-paralytic polio can last from one to 10 days. ▫ ▫ ▫ fever sore throat headache Vomiting fatigue meningitis

Paralytic polio • 1 % of polio cases can develop into paralytic polio. leads to paralysis in ▫ the spinal cord (spinal polio), ▫ brainstem (bulbar polio), ▫ or both (bulbospinal polio).

Paralytic polio • Initial symptoms are similar to non-paralytic polio. But after a week, more severe symptoms will appear. These symptoms include: ▫ loss of reflexes ▫ severe spasms and muscle pain ▫ loose and floppy limbs, sometimes on just one side of the body ▫ sudden paralysis, temporary or permanent ▫ deformed limbs, especially the hips, ankles, and feet

Spinal polio • Most common form of paralytic poliomyelitis • It results from viral invasion of the motor neurons of the anterior horn cells, or the ventral gray matter section in the spinal column • Virus invasion causes inflammation of the nerve cells, leading to damage or destruction of motor neuron ganglia – Flaccid paralysis

Bulbar polio • 2% of cases of paralytic polio, • Occurs when poliovirus invades and destroys nerves within the bulbar region of the brain stem. • Weakens the muscles supplied by the cranial nerves. • Symptoms of encephalitisfever, pharyngitis, headache, anorexia, nausea, and vomiting. • Illness may progress to aseptic meningitis and menigoencephalitis

CNS manifestations: Weakness: Vary from one muscle or group of muscles, to quadriplegia. Proximal muscles: legs more commonly than arms. Typically worsens over 2 to 3 days Bulbar involvement: producing dysphagia, dysarthria, and difficulty handling secretions. Cardiovascular & Resp. symptoms…bulbar poliomyelitis

Post-polio syndrome (PPS) • This can occur after 15 to 40 years. Common symptoms of post-polio syndrome are: ▫ ▫ ▫ ▫ ▫ continuing muscle and joint weakness muscle pain that gets worse becoming easily exhausted or fatigued muscle wasting /muscle atrophy trouble breathing and swallowing sleep apnea, or sleep-related breathing problems low tolerance of cold temperatures new onset of weakness in previously uninvolved muscles depression trouble with concentration and memory

Laboratory Diagnosis Viral isolation from Throat swabs- up to 1 week Rectal swabs- 6– 8 week) Stool specimens –(6– 8 week) Blood- (3– 5 days)

Lab • Antigen can be detected and serotyped by neutralization with specific antiserum. • Specific gene detection by PCR • Stool culture • Cultures of CSF, serum or throat swab are positive less frequently, but indicative of disease. • Antibody detection: Neutralizing Antibody and CFT Antibody

Prevention of poliomyelitis • Polio Vaccination • Salk vaccine -inactivated poliovirus vaccine (IPV) using killed virus - 1952. • Sabin oral poliovirus vaccine (OPV), using live attenuated virus- 1960. • In areas where polio is endemic, primary immunization is performed with Sabin OPV. • it has been replaced by the Salk IPV in countries without polio.

Polio Vaccination • Multiple doses required to achieve high humoral conservation rates against all virus types • Babies are given 4 doses through out their infancy.

Reference • Surinder Kumar-Essentials Of Microbiology • Anandanarayanan-Text Book Of Microbiology • Apurba Sankar Sastry-Essential of Medical Microbiology