Genotyping and pathotyping of diversified strains of infectious bronchitis viruses circulating in Egypt

Table 4 Pathogenicity index based on clinical scoring and necropsy of kidney and trachea of specific pathogen free chicks infected at one-day-old with infectious bronchitis viruses with examining survivors and dead birds during 14 d observation

Group	IBV isolates code	Observation record			Clinical score1	Gross lesion score2		Pathogenicity index3	Pathotyp4
		Dead	Survived	Mortality (%)		Trachea	Kidney
1	IBV-EG/1212B-2012	5/10	5/10	50	3	10	10	25	High
2	IBV-EG/IBV1-2011	4/10	6/10	40	2	10	10	24	High
3	IBV-EG/11539F-2011	1/10	9/10	10	1	7	0	8	Low
4	Negative control	0/10	10/10	0	0	0	0	0	No

¹Clinical score[2,28]: Score 0: No clinical signs; score 1: Lacrimation, slight shaking of head, watery feces; score 2: Lacrimation, presence of nasal exudate, depression, watery feces; score 3: Strong lacrimation, presence of nasal exudates, severe watery feces;

²kidney and trachea score: No of chicks with lesion score of ≥ 1;

³pathogenicity index: No of chicks with lesion score ≥ 1 + 1 point for every 10% mortality;

⁴pathotypes: Low (pathogenicity index value 1-9), intermediate (pathogenicity index value 10-18), high (pathogenicity index value ≥ 19). IBV: Infectious bronchitis virus.