The lungs of cows differ from those of other animals. This makes them more susceptible to respiratory infections, in which the bacteria Mannheimia haemolytica plays an important role. In healthy animals, M. haemolytica not dangerous, until stress factors occur, possibly resulting in acute death of animals. Management measures can prevent this.
The lungs of a cow differ from the lungs of a horse, human, pig, dog or cat. One of the differences is lung capacity. The lung capacity of an adult cow is 12 liters and the oxygen requirement is 124 liters per minute. 30 breaths per minute are taken to meet this oxygen requirement. For comparison, a horse has a capacity of 42 liters and only needs 49 liters of oxygen per minute. The air flow is therefore higher in a cow than in a horse. This high airflow allows bacteria and viruses to penetrate deep into the lungs, where they can cause infection and inflammation.
Cows also have relatively longer airways, which creates more dead space. The dead space is the part of the lung where no oxygen is exchanged. This does not affect the functioning of the immune system, but it offers pathogens better opportunities to take action.
These restrictions make cows’ lungs more vulnerable to respiratory infections.
From bacteria to pathogens
The upper respiratory tract of cows contains a mixture of bacteria and viruses, without causing disease. The coexistence of these bacteria, viruses and other microorganisms is called the microbiome. It is a dynamic system that ‘lives’ there in balance and keeps the body healthy. Factors that promote susceptibility to disease change this composition, causing the animal to become ill.
Mannheim haemolytica is a bacterium that is part of the microbiome, also called a commensal. M. haemolytica consists of several serotypes, the most common being serotype A2. This is often present in low numbers in the nose and throat and does not cause damage (1). Two other serotypes, A1 and A6, are much more aggressive and are often observed in diseased animals in affected lung tissue. Serotype A1 is responsible for disease in cows or calves in 70% of cases in the Netherlands. When stress factors occur and the immune system is compromised, serotype A1 settles on the nasal and throat mucosa and replaces serotype A2. This shift is the beginning of an infection. Serotype A1 travels to the lungs with the inhaled air and damage begins quickly.
One of the main factors why M. haemolytica so dangerous is the production of toxins (leukotoxin). This toxin stimulates white blood cells and also causes swelling, weakening and breakdown of lung tissue (2,3). In this case, lung damage is the result of interaction between bacteria and the immune system of the cow or calf (4).
A cow or calf with an M. haemolytica infection can deteriorate rapidly or cause acute death without noticing any symptoms of disease. It is therefore extremely important to be there on time. If there are any symptoms, they will manifest themselves in high fever, rapid breathing and an acute drop in milk (in dairy cows).
In the past, prevention has been based almost exclusively on antibiotic administration, but because this contributes to the emergence of multiple antibiotic-resistant strains of M. haemolytica Vaccination is being used more and more nowadays (5). The latest developments focus on vaccines based on the toxin (leukotoxin) (6). This type of immunization stimulates an increase in several types of antibodies, which ensures good immunity with a 50-70% reduction in clinical symptoms and lung damage. The high efficacy of anti-leukotoxin vaccines is also because it provides cross-protection between other toxin-producing types (7). In addition, management measures are just as important. This includes colostrum management, quality of the (milk) feed, the climate in the stable and keeping calves in (same and small) groups.
Mannheim haemolytica is usually associated with fatal pneumonia (8). In healthy animals, M. haemolytica acts as a commensal until stressors occur. Prevention should not be based on antibiotic use alone, but should be combined with management measures, including vaccination, to control this disease.
Would you like to know more about Mannheim haemolytica or vaccination against this? Please contact one of our veterinarians: Jessica Hartjes, 06-3800 8533 (Netherlands), Niels Groot Nibbelink (South Netherlands) 06-8100 2036, Anne-Miek Timmermans (Central Netherlands) 06-1370 2817, Sabine Hoogeveen (North -West Netherlands) 06-8279 0165 or Anne-Lynn Geertshuis (North-East Netherlands) 06-2046 9304.
1. Griffin, D., Chengappa, M.M., Kuszak, J., McVey, D.S., 2010. Bacterial pathogens of the bovine respiratory disease complex. Vet Clin North Am Food Anim Pract 26, 381-394.
2. Roger J. Panciera, Anthony W. Confer. Pathogenesis and Pathology of Bovine Pneumonia Vet Clin North Am Food Anim Pract. 2010 Jul; 26(2): 191–214.
3. Jeyaseelan, S., Sreevatsan, S., Maheswaran, S.K., 2002. Role of Mannheimia haemolytica leukotoxin in the pathogenesis of bovine pneumonic pasteurellosis. Anim Health Res Rev 3, 69-82.
4. Mosier, D., 2015. Review of BRD pathogenesis: The old and the new. Animal Health Research Reviews, 15(2), 166-168.
5. Zecchinon, L., Fett, T., Desmecht, D., 2005. How Mannheimia haemolytica defeats host defence through a kiss of death mechanism. Vet Res 36, 133-156.
6. Tobias Oppermann, Nadine Busse, Peter Czermak, 2017. Mannheimia haemolytica growth and leukotoxin production for vaccine manufacturing — A bioprocess review. Electronic Journal of Biotechnology, 28, 95-100.
7. Rice, J. A., Carrasco-Medina, L., Hodgins, D. C., Shewen, P. E., 2007. Mannheimia haemolytica and bovine respiratory disease. Animal Health Research Reviews, 8(2), 117-128.
8. Laëtitia Dorso, Maud Rouault, Claire Barbotin, Christophe Chartier, Sébastien Assié, 2021. Infectious Bovine Respiratory Diseases in Adult Cattle: An Extensive Necropsic and Etiological Study. Animals (Basel). 2021 Aug; 11(8): 2280.
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