Reference | Primary bacterial challenge (route of infection and dose/animal) | Time between exposure to the two pathogens | Secondary bacterial challenge (route of infection and dose/animal) | Main results of the clinical trials | Impact of the coinfection on BRD (score 1 to 4) | Study limitations |
---|---|---|---|---|---|---|
Houghton and Gorlay, [154] | M. bovis (Intranasal) | Simultaneous | M. haemolytica (Intranasal) | Dually inoculated animals were more severely affected than animals inoculated with one pathogen M. bovis group: 1–6% lung consolidation M. haemolytica group: 0–1% lung consolidation Coinfected animals displayed 34 to 55% of lung consolidation | 3 | |
Gourlay et al. [155] (gnotobiotic calves) | M. bovis (Intranasal and intratracheal, 6 × 108 CFU) | 1 day and 2 days | M. haemolytica (Intranasal and intratracheal, 7 × 108 CFU cultured for 6 h or for 18 h before inoculation) | Mannheimia group: no illness or gross lesions Coinfected group: severe clinical illness and 16% of lung consolidation at necropsy with 2-days delay, severe illness and high area of lung consolidation in dually infected calves (50–64%) inoculated with 1-day delay between pathogens, increased lesions when using 6 instead of 18 h culture of Mannheimia | 3 | Lack of M. bovis group |
Gourlay et al. [155] (gnotobiotic calves) | M. haemolytica (Intranasal and intratracheal, 7 × 108 CFU cultured for 6 h or for 18 h before inoculation) | 2 days | M. bovis (Intranasal and intratracheal, 6 × 108 CFU) | No significant increase in pneumonia in coinfected animals, mild signs in all groups | 2 | Lack of M. bovis group |
Gourlay et al. [155] (Conventionally reared calves) | M. bovis (Intranasal and intratracheal, 6 × 108 CFU) | Simultaneous | M. haemolytica (Intranasal and intratracheal, 7 × 108 CFU cultured for 6 h or for 18 h before inoculation) | Mannheimia group: no illness and no gross lung lesions Coinfected group: only few calves displayed fever and clinical signs and 6–8% of lung consolidation at necropsy, the remaining calves displayed no clinical signs | 2.5 | |
Gourlay et al. [155] (Conventionally reared calves) | M. bovis (Intranasal and intratracheal, 6 × 108 CFU) | 1 day | M. haemolytica (Intranasal and intratracheal, 7 × 108 CFU cultured for 6 h or for 18 h before inoculation) | M. bovis group: moderate clinical signs and reduced extent of lung consolidation (27–40%) Coinfected group: severe clinical signs resulting in the death of one calf and higher extent of lung consolidation (28 to 60%) | 4 |