Pathogenesis and Lab diagnosis of Ebola virus

Dr. Pendru Raghunath

Source of infectionSuspected to be a zoonotic (animal-borne)

Suspected reservoirs

Bats

Primates (in some cases, have been confirmed)

Pathogenesis

Mode of infection

1. Direct contact with contaminated human body fluids such as blood, urine, vomitus, faeces and semen

2. Contact with contaminated medical products such as syringe needles

3. Consumption of wild animal meat (“bush meat”)

Pathogenesis

• Macrophages infected with Ebola virus produce different cytokines and nitric oxide (NO) .

• Breakdown products of necrotic cells also stimulate the release of the same cytokines

• These cytokines are responsible for the fever, malaise, vasodilatation, increased vascular permeability, hypotension, and shock of ebola virus disease

• Virus-infected macrophages synthesize cell-surface tissue factor (TF), triggering the extrinsic coagulation pathway

• Liver dysfunction and protein C synthesis inhibited

• Small blood clots form in vessels

• Consume all the available coagulation proteins and platelets

• Normal coagulation is disrupted, this leads to abnormal bleeding

• Disruption of normal blood flow to organs and multi organ failure

Incubation period

• Patients with Ebola virus disease typically have an abrupt onset of symptoms 8 to 10 days after exposure (range 2 to 21 days)

• The incubation period for the individual patient depends, in part, upon the type of exposure (eg, approximately 6 days for percutaneous exposure versus 10 days for contact exposure).

Clinical manifestationsPatients with Ebola virus disease initially present with non-specific

influenza-like symptoms and can progress to multiorgan failure and septic shock

• Stage I (unspecific):

-Extreme asthenia (body weakness) - headache - arthralgia (neuralgic pain in joints) - myalgia (muscular pain or tenderness), back pain -High fever - Nonproductive cough and pharyngitis -diarrhea, nausea and vomiting, anorexia abdominal pain - dysphagia (difficulty in swallowing)

Late Symptoms

  Stage II (specific)

Bleeding from eyes, ears, and nose Bleeding from the mouth and rectum (gastrointestinal bleeding) Neuropsychiatric abnormalities (depression) Anuria (the absence of urine formation) Hiccups Eye inflammation (conjunctivitis) Genital swelling (labia and scrotum) Increased feeling of pain in skin Rash over the entire body that often contains blood Mucosal redness of the oral cavity Seizures, coma, delirium

Laboratory diagnosis

• Non-specific methods• Specific methods

Non-specific methods• Leukopenia — Leukopenia usually presents as lymphopenia and is

then followed by an elevated neutrophil count, with an increased percentage of immature forms

• Thrombocytopenia — Platelet counts are usually in the range of 50,000 to 100,000/µl

• Transaminitis —Elevated serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels

• Coagulation abnormalities — Prothrombin (PT) and partial thromboplastin times (PTT) are prolonged

• Renal abnormalities — Proteinuria is a common finding, and renal insufficiency occurs with progression of illness.

• The diagnosis is confirmed by isolating the virus, detecting its RNA or proteins, or detecting antibodies against the virus in a person's blood

• Isolating the virus by cell culture, detecting the viral RNA by polymerase chain reaction (PCR) and detecting proteins by ELISA is effective early and in those who have died from the disease

• Virions can be seen and identified in cell culture by electron microscopy due to their unique filamentous shapes, but electron microscopy cannot tell the difference between the various filoviruses despite there being some length differences.

• Detecting antibodies against the virus is effective late in the disease and in those who recover.

Specific methods

Immunochromatographic method