Despite decades of research and efforts, bovine respiratory disease (BRD) remains the most important cause of economic losses in youngstock¹. BRD costs all farmers in many ways: treatment costs, lower animal survival, reduced growth, higher age at first calving – all huge impacts on animal health, welfare, productivity, and overall profitability². A recent Canadian study found that BRD early in life can have a profound impact on first lactation milk yield – calves that had BRD produced 525 kg LESS 305-day milk than their healthy herdmates in their first lactation³. Preventing BRD will pay in the short AND long-term.

So, what’s causing BRD in our calves?

BRD is a multifactorial disease – most illness is caused by a variety of viruses and bacteria. There is usually other factors that stress the animal and suppress their immune system – poor ventilation, rapid temperature fluctuations, high stocking density, irritating gasses (ammonia) etc.

Often, BRD starts with a virus causing damage to the upper and lower respiratory tract. Bacteria are the next culprits – they take advantage of the damage the viruses have done to the respiratory tract and can produce profound lung damage.

Bovine Respiratory Syncytial Virus (BRSV) is a major virus associated with BRD. Recent studies of the viromes of healthy and diseased cattle found that BRSV is the most common vaccine-preventable virus in BRD cases^4,5. Data from the Ontario Veterinary College’s Animal Health Lab identified BRSV as playing a major role in BRD outbreaks, a trend that is headed in the wrong direction (Figure 1)⁶.

Young calves are the primary group of animals affected by BRSV, with the most severe presentations of disease occurring in animals under 6 months of age and often in the presence of protective maternal antibodies⁷. These infections are often passed from older (often silently infected animals) to younger animals, who are most susceptible to the virus. That being said, it is not uncommon to see outbreaks in adult animals, especially where vaccination has been inconsistent on the farm.

What does BRSV look like in cattle?

BRSV is the only virus that causes direct and severe lung damage on its own. It has an incubation period between 3 and 5 days with disease spread from day 3 to 10 after infection. Infected animals can show absolutely no signs. However, for animals that do get sick, it may last for up to 2 weeks! Signs of BRSV in cattle include sudden onset of discharge from the nose and eyes, high fevers of > 40ºC / 104 ºF, cough, depression, off-feed, and progressive difficulty in breathing / wheezing. Lactating cows may also have a sudden drop in milk production. Pastured cattle that are not seen daily may be found dead or in severe respiratory distress. Without testing animals in early onset of disease, we may not be able to detect BRSV. By this time, bacteria may have set up shop, causing further damage.

How about the bacteria that cause BRD?

When evaluating what bacteria are causing BRD in the herd, the picture tends to be less clear – with mixed infections the predominant finding – over half of all samples submitted to a major diagnostic lab in Quebec were positive for more than one virus and bacteria⁸. Figure 2 outlines the relative prevalence of the 5 most common bacteria identified.

Most bacteria seen in Figure 2 can live in the UPPER respiratory tract (noses, throats) of healthy calves. They often need a trigger to express disease – some combination of immune-suppressing stressor (changing weather, mixing with other animals) or cellular injury (ammonia, respiratory viruses) that allows them to travel into the lungs and cause damage. While all of these bacteria can cause significant disease, Mannheimia haemolytica, Histophilus somni, and Mycoplasma bovis have the most weapons to establish infections and severe cause pneumonia.

Preventing BRD in your herd

There are a variety of steps that everyone can take to control BRD in their herds:

1. Lab testing – you need to know the viruses and bacteria that is causing problems in your herd. The key here is early in the disease process to get a fuller picture! Your herd vet will lead you through this process.
2. Separate dam from calf ASAP (at latest 12 hours post-calving) to prevent disease transmission from dam to calf. Ideally, young animals will also be housed in separate environments to prevent aerosol transmission.
3. Minimize stressors – recall that stress suppresses the immune system. Examples include:
   • Calm animal handling,
   • Reduced mixing/moving events to as few as possible,
   • Maintain a constant barn environment within the animal’s thermoneutral zone,
   • Ensure clean, dry bedding,
   • Keep stocking densities low – this reduces stresses and also lowers the possibility that an infected animal will pass the virus/bacteria on to a herd mate.
4. Focus on ventilation – adequate ventilation:
   • Reduces harmful fumes or particles that can stress the animal or damage their airways.
   • Disperses any virus or bacteria in the air around the animal.
   • Ensures optimal temperature and humidity at the pen level
5. Weaning protocols are vital in young calves, as most of the BRD in youngstock occurs shortly after weaning:
   • Calves should be consuming 2 pounds of calf starter before you remove their milk.
   • Ample fresh, clean drinking water improves starter intake and helps with rumen development
6. Vaccination – use proven products that are effective in the class of animal you are vaccinating.
   • Young calves (<1 month old), because of colostral antibodies, should be vaccinated intranasally early in life.

Vaccination for success

Getting management and environment right are KEY steps to reducing BRD on the farm. You must not forget about using a proven vaccine to prevent disease!

Respiratory viruses such as Infectious Bovine Rhinotracheitis (IBR) and Bovine Viral Diarrhea (BVD) are present at very low prevalence in our dairy herds – current modified live virus (MLV) vaccines have done an excellent job at reducing the prevalence of these viruses. Duration of protection against these products is often enumerated on the label insert and tends to be greater than 1 year. Challenge studies evaluating Parainfluenza 3 (PI3) have not been able to produce disease in any calves challenged!

However, when looking at BRSV, things do not look as good. A recent review found that current BRSV-containing vaccines on the market had little effect on calf morbidity and mortality following viral challenge⁹. PI3 components also had no effect on clinically relevant outcomes. When another viral intranasal product was tested in the Canadian market, it had little impact on most clinically relevant outcomes, and there was even an instance where vaccination negatively affected pre-weaning weight gains in one herd¹⁰. Times may have changed though, as NASYM is now in the Canadian market.

When looking at bacterial pneumonia vaccination, the evidence is quite variable. A recent review study found that while the evidence supports the use of bacterial vaccines to prevent pneumonia, the data is quite variable¹¹. The most prudent thing is to evaluate farm-level risk (if you’re a producer, your veterinarian is a great resource) and develop a monitoring strategy to evaluate the effectiveness of any product used in the herd.

HIPRA and BRD Prevention

HIPRA, a leading multinational veterinary pharmaceutical company, strives to be the reference in prevention for animal health. That is why the focus has been on developing industry-leading vaccines to prevent disease in animals.

In Canada, HIPRA can help cattle breathe easier with:

NASYM – a MLV against the most common virus causing respiratory disease in cattle – BRSV. With NASYM you get:

• Long-lasting – An industry-leading 8 MONTHS duration of immunity,
• Effective – Significant reduction in respiratory clinical signs due to BRSV infections,
  • Reduction in clinical signs 5 days after intranasal vaccination,
• Safe and effective to use early in the life of the calf,
• Break the cycle of infection – reduced virus shedding in vaccinated animals,
• Flexibility – product that can be administered either intranasally or intramuscularly.

HIPRABOVIS Somni/LKT – a vaccine against the most pathogenic bacteria commonly associated with pneumonia. With HIPRABOVIS you get:

• Lower disease  – significant reduction in clinical disease, antibiotic use, and death,
• Broad control – contains both M.haemolytica and H.somni – key causes of bacterial pneumonia,
• Long-lasting protection – high antibody titres for up to 40 weeks following the primary series.

To learn more about HIPRA, please visit www.hipra.com. There is also an excellent video library with various experts advising on BRD prevention.

For more on how HIPRA can help improve the health of your cattle, contact your veterinarian or Dr. Dan Shock, Business Unit Manager – Ruminants (dan.shock@hipra.com)”

References

1. Gorden PJ, Plummer P. Control, Management, and Prevention of Bovine Respiratory Disease in Dairy Calves and Cows. Vet Clin North Am Food Anim Pract. 2010;26(2):243-259. doi:http://dx.doi.org/10.1016/j.cvfa.2010.03.004
2. Closs G, Dechow C. The effect of calf-hood pneumonia on heifer survival and subsequent performance. Livest Sci. 2017;205(September):5-9. doi:10.1016/j.livsci.2017.09.004
3. Dunn TR, Ollivett TL, Renaud DL, et al. The effect of lung consolidation, as determined by ultrasonography, on first-lactation milk production in Holstein dairy calves. J Dairy Sci. 2018;101(6):5404-5410. doi:10.3168/jds.2017-13870
4. Zhang M, Hill JE, Godson DL, Ngeleka M, Fernando C, Huang Y. The pulmonary virome, bacteriological and histopathological findings in bovine respiratory disease from western Canada. Transbound Emerg Dis. 2020;67(2):924-934. doi:10.1111/tbed.13419
5. Zhang M, Hill JE, Fernando C, et al. Respiratory viruses identified in western Canadian beef cattle by metagenomic sequencing and their association with bovine respiratory disease. Transbound Emerg Dis. 2019;66(3):1379-1386. doi:10.1111/tbed.13172
6. Brooks A. Increased detection of BRSV associated with respiratory disease in cattle. AHL Newsletter. Published 2020. Accessed July 20, 2020. https://www.uoguelph.ca/ahl/increased-detection-brsv-associated-respiratory-disease-cattle
7. Sacco RE, McGill JL, Pillatzki AE, Palmer M V., Ackermann MR. Respiratory Syncytial Virus Infection in Cattle. Vet Pathol. 2014;51(2):427-436. doi:10.1177/0300985813501341
8. Savard C, Broes A. Bovine Respiratory Profiles Summary in Quebec – 2019. Bio-Vet Animal Health News. Published 2020. Accessed July 20, 2020. https://www.biovet-inc.com/en/bovine-respiratory-profiles-summary-in-2019/
9. Theurer ME, Larson RL, White BJ. Systematic review and meta-analysis of the effectiveness of commercially available vaccines against bovine herpesvirus, bovine viral diarrhea virus, bovine respiratory syncytial virus, and parainfluenza type 3 virus for mitigation  of bovine respiratory disease complex in cattle. J Am Vet Med Assoc . 2015;246(1):126-142.
10. Ollivett TL, Leslie KE, Duffield TF, et al. Field trial to evaluate the effect of an intranasal respiratory vaccine protocol on calf health, ultrasonographic lung consolidation, and growth in Holstein dairy calves. J Dairy Sci. 2018;101(9):8159-8168. doi:10.3168/jds.2017-14271
11. Larson RL, Step DL. Evidence-Based Effectiveness of Vaccination Against Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni in Feedlot Cattle for Mitigating the Incidence and Effect of Bovine Respiratory Disease Complex. Vet Clin North Am Food Anim Pract. 2012;28(1):97-106.e7. doi:http://dx.doi.org/10.1016/j.cvfa.2011.12.005