| Shipping fever pneumonia is a respiratory disease of cattle of multifactorial etiology with
Mannheimia
haemolytica
and, less commonly,
Pasteurella
multocida
or
Histophilus
somni
(Histophilosis : Introduction), being the important infectious agents involved. Shipping fever pneumonia is associated with the assembly into feedlots of large groups of calves from diverse geographic, nutritional, and genetic backgrounds. Disease is typically seen in feeder calves 7-10 days after assembly in a feedlot. Morbidity can approach 35%; mortality is 5-10%. |
| Etiology: |
| The pathogenesis of shipping fever pneumonia involves stress factors, with or without viral infection, interacting to suppress host defense mechanisms, which allows the proliferation of commensal bacteria in the upper respiratory tract. Subsequently, these bacteria colonize the lower respiratory tract and cause a bronchopneumonia with a cranioventral distribution in the lung. Multiple stress factors are believed to contribute to the suppression of host defense mechanisms.
Transportation over long distances serves as a stressor; it may be associated with exhaustion, starvation, dehydration, chilling and overheating depending on weather conditions, and exposure to vehicle exhaust fumes. Additional stressors include passage through auction markets; commingling, processing, and surgical procedures on arrival at the feedlot; dusty environmental conditions; and nutritional stress associated with a change to high-energy rations in the feedlot. The
individual viral and bacterial etiologies, clinical signs, lesions, and treatment are discussed under viral respiratory tract infections (
Viral Respiratory Tract Infections: Overview) and bacterial pneumonia (
Bacterial Pneumonia: Overview). |
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| Control and Prevention: |
| Prevention of shipping fever pneumonia should focus on reduction of the stressors that contribute to development of the disease. Cattle should be assembled rapidly into groups, and new animals should not be introduced to established groups. Auction markets and mixing of cattle from different sources should be avoided if possible. Transport time should be minimized, and rest periods, with access to feed and water, should be provided during prolonged transport. Calves should be
weaned 2-3 wk before shipment, and surgical procedures should be performed in advance of transport. Cattle should be processed within 48 hr after arrival at the feedlot. A rest period of 6-12 hr after transport may allow for rehydration and return of cortisol to levels that will have less impact on the immune response to vaccination. Adaptation to high-energy rations should be gradual as acidosis, indigestion, and anorexia may inhibit the immune response. Vitamin and mineral
deficiencies should be corrected. Dust control measures should be used. Metaphylaxis with long-acting antibiotics given “on arrival” for cattle at high risk for developing shipping fever pneumonia has been shown to significantly reduce morbidity and improve rate of gain. |
| The administration of viral respiratory vaccines on entry to the feedlot has been historically controversial, especially with modified live vaccines. These vaccines have been reported to increase the mortality associated with shipping fever pneumonia. Continuous improvements in modified live vaccine production, and the fact that these vaccines do not require a booster, have made them preferred over killed vaccines for on-arrival processing. When possible, vaccinations for the
viral and bacterial components of shipping fever pneumonia should be given 2-3 wk before transport and can be repeated on entry to the feedlot. |
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