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Breakout from Pneumonia Outbreaks
Publish Date:Winter 2010
Due to the time of year, weather and associated management changes, we are right in the middle of livestock pneumonia season. However, good managers know how to recognize early cases and treat for best outcomes. More importantly, they know how to reduce the factors that put animals at risk of this serious disease.
Pneumonia: The Scourge of Animal Populations
Pneumonia means inflammation of the lungs. Inflammation is a normal bodily response to anything foreign that enters the body or disturbs cells; it is actually part of the body’s defense system and healing process. Unfortunately, the fluid and cells that rush to a diseased or injured tissue during the process of inflammation can be quite detrimental when this process happens in the lungs. Extra fluid and cells in the free space of the lungs or in the walls of the air sacs can significantly interfere with the exchange of oxygen and carbon dioxide that must occur for optimal animal health and performance. Indeed, an animal’s response to a disease-causing agent in the lungs may cause much more damage than the pathogen itself. Pneumonia is rare when animal populations and densities are low. In winter, animals are housed or gather more closely together, increasing the concentration of pathogens in their environment. Confinement and higher animal densities also result in increased air temperatures, humidity and condensation, which are beneficial conditions for pathogen survival and transmission. Contact between disease-carrying individuals and the rest of the herd increases during cold weather, as well.
Pneumonia is regarded as a “multifactorial disease,” which means multiple factors are usually responsible for the development of clinical disease. To clarify, in an otherwise healthy animal, the presence of potentiallypathogenic bacteria in the nasal passages would usually not be enough to cause disease. However, a chilled, stressed and malnourished animal would be at much greater risk of clinical disease.The bacteria responsible for most cases of pneumonia are common inhabitants of the nasal passages of healthy animals. Many factors can weaken the host’s immune system and/or damage the lining of the respiratory tract to such an extent that these pathogens are able to progress deeper into the respiratory tract and cause disease (Table 1).
Viral causes of pneumonia deserve special mention because they often precede cases of secondary bacterial pneumonia. The main viral causes of pneumonia in cattle include Infectious Bovine Rhinotracheitis (IBR), Parainfluenza 3 (PI3), Bovine Respiratory Syncyntial Virus (BRSV) and Bovine Viral Diarrhea Virus (BVD). Other recognized but less common pneunomia-related viruses include Herpesvirus, Adenovirus, Rhinovirus, Malignant Catarrhal Fever Virus, Enterovirus and Reovirus. In small ruminants, a chronic “slow virus” (Ovine Progressive Pneumonia virus in sheep and Caprine Arthritis and Encephalitis virus in goats) can also cause pneumonia. The lungs of affected animals enlarge as the body responds to the virus by depositing scar tissue; death is usually due to a secondary bacterial infection.
The Real Culprits
Pasteurella multocida and Mannheimia haemolytica are the two bacteria most commonly associated with pneumonia in cattle, particularly in recently-weaned calves that are transported significant distances (“shipping fever”). These bacterial can also be problematic in sheep, goats and swine. Numerous other bacteria can also cause pneumonia including Mycoplasma, Pseudomonas, Corynebacterium, Staphylococcus, Hemophilus, Streptococcus, E. coli, Bordetella, Neisseria, Erysipelothrix, and Fusobacterium.
Fungal organisms can sometimes cause respiratory infections, as can lungworms. White Muscle Disease secondary to selenium deficiency can affect muscles involved in swallowing, predisposing the animal to inhalation pneumonia. Vomiting, improper administration of oral medications or any other situation that causes foreign objects to enter the airway can also result in pneumonia.
Signs of Illness
Animals with pneumonia typically have a fever, reduced appetite and are less active than their herdmates. They may stand alone. They will lag behind when the herd/flock moves. As the disease progresses, animals will have an increased respiratory rate and breathe with difficulty, sometimes to the point of openmouthed breathing. They may cough and/or have nasal discharge. Weight loss and “rough looking” condition are common in chronic cases. Animals can die after a very short time of illness with few clinical signs or weeks later after a prolonged course of pneumonia. Others can become chronic “poor do-ers” with poor performance; they can also serve as a source of infection for herdmates.
As already mentioned, successful managers are able to keep the incidence of pneumonia low through effective management practices. Here is a summary of effective practices.
1. Provide adequate nutrition, meaning proper amounts of a balanced diet for all individuals based on desired levels of production and performance as well as maintenance.
2. Do not add new animals to a group without an extensive period of quarantine. Closed herds or closed groups are safest.
3. Consider airflow and nose-to-nose contact: do not have younger animals downwind of or in direct contact with older animals
4. Do not keep chronic poor do-ers.
5. Minimize dust and smoke in the environment.
6. Control mud—it promotes chilling, which increases stress and maintenance requirements.
7. Working with your veterinarian, create and implement an effective vaccination program to prevent pneumonia. Follow vaccine recommendations, including proper storage, handling, and administration of doses.
8. Monitor weanlings and young animals carefully; they are the most likely to develop clinical disease.
9. Ensure excellent ventilation that provides fresh, clean air to all animals. Do not mistake drafts for ventilation. Assess air quality at all levels, including nose level of recumbent animals—this is where high ammonia levels are most often detected.
10. Do not overcrowd. Ensure adequate feeder space and bedding space for all animals.
11. Isolate suspected cases in a hospital area. Do healthy animal chores first, then treat sick animals. Change clothing, wash hands and disinfect equipment after handling sick animals.
12. Necropsy dead animals when the cause of death is unknown. Laboratory tests can often identify the causative virus and/or bacteria, determine antibiotic sensitivities and lead to effective vaccination recommendations.
Losses due to pneumonia are much greater than the obvious loss of individual dead animals. Pneumonia in a herd or flock means animals are not performing up to their maximum potential, production costs are higher than they should be, labor is increased and food product quality is compromised. Responsible animal caretakers know it is their duty and responsibility to address animal welfare concerns and ensure a safe and healthy environment for their animals. During animal confinement season, it is essential that producers be ever vigilant for the factors that can result in a pneumonia outbreak and mitigate as many of these factors as possible.
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