14/04/2024
Pneumonia - in cattle
Other Names
Bovine Respiratory Disease
Bronchopneumonia
Respiratory Disease
Description
Pneumonia refers to inflammation of the lungs. It may be accompanied by inflammation of the larger airways (bronchioles) and referred to as bronchopneumonia, or by inflammation of the pleura (outer surface of the lung, adjacent to the chest wall) and referred to as pleuropneumonia.
Pneumonia in cattle is often caused by infectious agents, particularly by a combination of bacteria and viruses. Pneumonia in cattle, also known as bovine respiratory disease (BRD), is influenced by a complex causal web involving a range of animal, management, and agent factors.
The rapid, deep, open mouth breathing associated with heat stress is believed to facilitate the inhalation of organisms deep into the airways.
A number of viral, bacterial, and Mycoplasma pathogens may be involved. Many are normal inhabitants of the upper respiratory tract of cattle that can become serious opportunistic pathogens.
Infectious agents associated with BRD include:
Viruses:
1; bovine herpesvirus 1 (BHV-1 or IBR),
2; parainfluenza virus type-3 (PI-3),
3; bovine respiratory syncytial virus (BRSV),
4; bovine coronavirus (BCV),
5; bovine viral diarrhoea virus (BVD),
6; adenoviruses.
Bacteria:
1;Mannheimia haemolytica,
2;Pasteurella multocida,
3;Histophilus somni,
4;Arcanobacterium pyogenes,
5;Salmonella sp.
6;Mycoplasma sp.
The most common form of severe BRD is a bacterial bronchopneumonia involving one or more of the bacterial agents identified above. The viruses (and perhaps Mycoplasma) are thought to be initial infective agents that act to compromise respiratory defence mechanisms and allow the bacteria to pe*****te into the lower airways and alveoli causing more severe disease.
Clinical Signs and Diagnosis
Signs of BRD in cattle, particularly in the early stages, may be subtle and variable.
1;nasal/ocular/oral discharge,
2; depression,
3; lethargy,
4; emaciated body condition,
5; laboured or rapid shallow breathing,
6; coughing,
7; extended head and neck,
8; droopy ears.
The first observable sign in affected animals is often depression, observed as lethargy, reluctance to move, lowered head, drooped ears, and half-closed eyes. Serous nasal discharge is common in early stages, turning mucopurulent as the condition progresses.
Increased respiratory rates are common in early stages, due in part to elevated temperature. As the disease progresses, dyspnoea becomes more pronounced and animals may adopt a typical stance of extended neck, drooling, open mouth breathing, and a soft cough.
Affected animals may be found dead without obvious ante-mortem signs, and pneumonia therefore diagnosed at necropsy.
If lameness and joint swelling from arthritis is also present, then involvement of Mycoplasma bovis, Histophilus somni, and Chlamydophila sp. should be suspected.
Misdiagnosis is common. Pneumonia may be missed because cattle may show relatively few clinical signs until severely ill, and auscultation of ruminant lungs may be difficult and not very informative. In addition, a diagnosis of pneumonia may be made in cattle suffering from other conditions, such as heat stress, causing increased respiratory rate or dyspnoea.
At necropsy, anteroventral lobes mostly feel consolidated (firm), rather than spongy, and are discoloured (mostly dark red). The lung surface may be coated with fibrin strands or sheets, which may stick to the parietal pleura (lining of the rib cage).
Interlobular septa are usually prominent. It is not uncommon at necropsy to find more than 50% of lung consolidated with no ante-mortem signs having been detected.
Note that discolouration of the lungs on its own is not a sign of pneumonia. Pneumonia should be diagnosed by feel. Normal lungs feel soft and spongy and are pink, but can be severely discoloured by gravitational pooling of blood or congestion. Lungs with pneumonia feel rubbery (some viruses) or consolidated like liver (other viruses and bacteria).
Treatment
Treat suspected cases aggressively with
1; parenteral antibiotics (ceftiofur sodium, florfenicol, tilmicosin, tulathromycin, procaine penicillin, oxytetracycline, erythromycin, trimethoprim sulpha, or tylosin) and
2; non-steroidal anti-inflammatory drugs (flunixin meglumine, ketoprofen, meloxicam, or tolfenamic acid). Injectable vitamin C administered on initial diagnosis can help to improve response to treatment.
Prevention
Infectious agents associated with BRD are likely to be ubiquitous. Testing and vaccination protocols for some export shipments may reduce exposure to some viral pathogens, but it is likely that all shipments will be exposed at varying levels to some or all of the BRD pathogens. Preventive strategies should be aimed at minimising adverse effects of various potential stressors that may increase susceptibility to clinical infection, as well as trying to minimise risks of pathogen exposure and transmission.
A range of measures may be considered for animals at their farm of origin such as yard weaning, introduction to trough feeding and watering, dehorning, drenching, castration, and vaccination against a range of diseases including BRD pathogens. Many of these measures may be incorporated into accredited backgrounding or preconditioning programs aimed at ensuring consistent quality of animals arriving at a feedlot or assembly depot.
Selection of appropriate stock, minimal mixing of animals, low stress handling, minimising exposure to harsh weather prior to loading, optimal stocking rates, good ventilation, and having an ample supply of quality feed and water are all measures that may be used during export voyages to reduce the risk of BRD occurring.
Vaccines specifically targeting BRD pathogens may reduce morbidity and mortality. In Australia, registered bovine vaccines are available against BVD, infectious bovine rhinotracheitis (BHV-1) and Mannheimia haemolytica. Ideally, vaccination should occur prior to entering assembly points. Other infectious agents may be incorporated into vaccines that are registered in other countries, and these are occasionally used under special licensing arrangements in cattle being exported from All
