AGR 292 Unit 2

What is the leading health in feedlot cattle

bovine respiratory disease complex (BRD)

When do BRD typically occurs

in the first 45 days on feed

What acts first?

Viruses

What acts second?

Bacteria

Clinical Findings for viral pneumonia

Fever, nasal/ocular discharge, coughing, reduced appetite

How does viral pneumonia pass from animal to animal?

Direct Contact, Aerosol Droplets

When do most of respiratory disease occur

In autumn and early winter

Infectious bovine rhinotracheitis (IBR)

Damages the upper airway lining, predisposes cattle to secondary bacterial pneumonia, which can be fatal

BRSV (Bovine Respiratory Syncytial Virus)

Primarily affects young calves, directly damages lower respiratory tissue

Parainfluenza-3 (PI-3)

usually causes only mild disease, affects both upper and lower respiratory tracts, found alongside other BRD viruses

Bovine Viral Diarrhea Virus BVDV

immunosuppression, opens the door to secondary bacterial AND secondary viral pneumonia, common in young cattle, calf is born persistently infected (PI)

Epithelial Damage

Virus damages the airway lining that normally blocks

bacteria

impaired Immunity

Local and/or systemic immune defenses are weakened

Microbiota Disruption

The normal balance of airway bacteria is thrown off

Bacterial Overgrowth

Opportunistic bacteria multiply unchecked

How to diagnos viral pneumonis?

PCR on nasal swab or BAL fluid

How to tell if an animal has BVDV and is PI?

ear-notch ELISA or PCR

Why wouldn’t you culture for BRD virus?

Most BRD viruses grow poorly or not at all in routine viral culture

Are there MLV or killed vaccines for viral pneumonia?

Yes

What will you do if an animal has BVDV?

Identify the PI and cull

How to help prevent viral pneumonia?

Reduce weaning, shipping, and commingling stress

Clinical finding of bacterial pneumonia

Fever, labored breathing, abnormal lung sounds

How does bacterial pneumonia pass animal to animal?

Viral Precursors, Environmental Stress, Direct Contact

Mannheimia haemolytica (MH)

Most frequently isolated bacterium from BRD cases in feedlot and dairy calves, normally lives in the upper airway; proliferates after to lower after stress or viral infection. Releases leukotoxin during lung colonization

Pasteurella multocida

Secondary but significant cause of bacterial pneumonia, affects the upper respiratory tract, less common. Opportunistically bacteria move from the nose into the lungs

Mycoplasma bovis

Causes chronic pneumonia and arthritis, often with pulmonary abscessation. Usually secondary, but can be a primary pathogen under weaning/transport stress. Produces multifocal caseonecrotic bronchopneumonia

Host stress or immune compromise + a viral

initiator + a bacterial invader =

The BRD Complex Model

Whats the highest morbidity rate group?

Newly received, lightweight, high-risk calves

How to diagnose bacterial pneumonia?

Culture from transtracheal wash or BAL

Why wouldn’t you use a nasal swab for bacterial pneumonia?

lower-tract sampling is required for a reliable culture result

How to distinguish between major bacteria?

Lesion pattern

How to treat bacterial pneumonia?

antibiotic selection, blocking bacterial protein or DNA synthesis & replication

Why can antibiotics be bad for bacterial pneumonia?

Drug resistance

What is metaphylaxis?

mass treatment of high-risk arrivals, plus reducing the preceding viral/stress

How to prevent bacteria and viral pneumonia?

Avoid overcrowding, Optimize timing of vaccinations, Provide adequate rest, feed and water, Make sure bedding is clean and dry and keep animals as clean and dry as possible, Minimise exposure to environmental conditions, Improve ventilation

What is brisket disease?

chronic hypoxia at high altitude

Is brisket disease infectious?

No

When do most cattle get brisket disease?

6-8 months old

Symptoms of brisket disease

Lethargy, Breathing changes, Weakness

Clinical finding of brisket disease

Brisket edema, jugular distention, labored breathing a "nutmeg" liver

How to diagnose brisket disease?

Pulmonary Arterial Pressure (PAP) test via jugular catheterization

what is the pressure for brisket disease?

over 50mmHg

When should you test for brisket disease?

16+ months, after 3+ weeks at elevation

Treatment of brisket disease

Thoracocentesis plus immediate move to lower altitude, diuretics, antimicrobials, vitamin B complex