TABLE 1.

Clinical data obtained from calves infected with WT, rescued, or LR mutant viruses

Group	Clinical symptom
	Nasal sheddinga	Ocular sheddinga	Respiratory distressb	Off feedc	Conjunctivitisd	Secretion or lesions in turbinatee
WT	5–6 d (9.0 logunits)	5–6 d (7.2 logunits)	3–4 d	3 d	++++	++++
LR rescued	5–6 d (9.0 logunits)	5–6 d (7.0 logunits)	3–4 d	3 d	++++	ND
LR mutant	2–3 d (8.0 logunits)	0–1 d (5.5 logunits)	0–1 d	1.5 d	−−−	+

^aThe values indicate the length of time during the acute infection that nasal and ocular secretions were observed on average for each group. d, days. The numbers in parentheses indicate the highest titer obtained in each group during the time of shedding. 

^bRespiratory distress was deemed to be present when animals presented signs such as shallow quick breaths, hanging head, and locked front legs. The values represent the number of days (d) on average that each group showed the above-mentioned symptoms. 

^cCalves were considered off feed if food remained 12 to 16 h after feeding. The value represents the number of days on average that each group showed this symptom. 

^dA typical clinical sign of BHV-1 infection is conjunctivitis. Severe conjunctivitis (++++) was observed during the acute infection. No conjunctivitis (−−−) was seen in calves infected with the LR mutant virus. 

^eCalves were necropsied on days 0, 2, 4, 6, 10, and 14 p.i. A major amount of mucus (++++) was observed in the turbinates of calves infected with the WT virus, whereas low levels of mucus (+) were observed in the LR mutant-infected group. Typical herpetic lesions were observed in the turbinate in the WT group (days 10 to 14 p.i.), whereas few lesions were observed in the LR-mutant group. ND, not done.