Newcastle disease is an infection of domestic poultry and other bird species with Newcastle disease virus (NDV).
The extreme variation in virulence of different NDV isolates strain and the widespread use of live vaccines means that the identification of a NDV isolate as avian paramyxovirus-1 (APMV-1) from birds showing clinical signs does not confirm a diagnosis of ND, so that an assessment of the NDV virulence of the isolate is also required.
A definitive assessment of virus virulence is based on the intracerebral pathogenicity test (ICPI) of Newcastle Disease virus.
Its singular form cerebrum (pleural;) the principal and most anterior part of the brain in vertebrates, located in the front area of the skull and consisting of two hemispheres, left and right, separated by a fissure.
Its Prefers to the ability of an organism to cause disease (ie, harm the host) into host & producing respective clinical signs as well mortality in the individual
Define pathogenicity index
A series of records used for the ability of an organism to cause disease in biological fields.
Pathogenicity index of Newcastle Disease
v) The Intracerebral pathogenicity index is a test to see how virulent a virus is
The intracerebral pathogenicity index (ICPI) is the mean score per bird per observation over the 8-day period.
The ICPI is the mean score per bird per observation over the 8-day period.
How to inject virulent virus of NDV
The assistant presents the chick to operator while the superior positiion of skull is approachable during inject virulent virus of NDV in day old chicks . draw an imaginary line dividing skull in two equal halves in the head of day old chicks. few milimeter lateral to midline at the level of ocular orbit enter the skull by sharp needle 1–2mm inside. 100 microliter syringe fitted with .5cm needle 20 gauge is adequate during this test. injection is usually uneventful. some times chick may show little excitation but soon settle. very rearely chick may die. One more chick discarding accidental death after few days.
i) Fresh infective allantoic fluid with a HA (haemagglutunun Inhibition) titre >24 (>1/16) is diluted 1/10 in sterile isotonic saline with no additives, such as antibiotics.
ii) 0.05 ml of the diluted virus is injected intracerebrally into each of ten chicks hatched from eggs from an Specific Pathogen Free flock. These chicks must be left over 24-hours but under 40-hours old at the time of inoculation.
iii) The birds are examined every 24 hours for 8 days after inoculation in day old chicks.
iv) At each observation, the birds are scored: 0 if normal, 1 if sick, and 2 if dead after 8 days. (Birds that are alive but unable to eat or drink during examination period, should be killed humanely and scored as dead at the next observation in this test. Dead individuals must be scored as 2 at each of the remaining daily observations after death in this test.
The birds are examined every 24 hours for 8 days after inoculation in day old chicks.
At each observation the birds are scored
The most virulent ND viruses will give a maximum score of 2.0 in ICPI ( Intracerebral pathogenicity index) test, whereas lentogenic and asymptomatic enteric strains will give values close to 0.0 which indicate Ndv not able to produce disease into the host.
General Observation may explain by following way
Score 00 indicates: No clinical signs are observed, Feeding, watering & movements are normal.
Score 01 indicate that: Normal clinical signs of NDv are observed in desired times.
Score 02 indicates that: Chicks died per acute or acutely.
Reference diseases of poultry, 13th edition