Large Animal Medical Nursing: Food Animal Diseases Study Guide

Septic Arthritis in Calves

• Definition and Context: Septic arthritis involves the infection and inflammation of the joints in young calves.

• Treatment Protocols: To manage the infection, a combination of broad-spectrum systemic antibiotics is utilized along with localized interventions:   

• Intravenous (IV) Regional Antibiotic Perfusion: A technique used to deliver high concentrations of antibiotics directly to the affected limb.    

• Joint Lavage: The process of flushing the joint space with fluid to remove infectious material and inflammatory mediators.    

• Arthrotomy: A surgical procedure to open the joint for inspection or drainage.

Calf Scours

• Etiology (Causes):

  • Viral Agents: Various viruses can trigger enteric distress.    

  • Bacterial Agents: Specific bacteria are responsible for the infection.

  • Environmental and Nutritional Factors: Poor nutrition and inadequate sanitation are major contributing factors to the development and spread of the disease.

• Clinical Presentation: Manifests through specific clinical signs (though not listed exhaustively in the source, they typically involve diarrhea and dehydration).

• Management: Treatment strategies are required to address hydration and the underlying cause.

White Muscle Disease (WMD)

• Alternative Name: Nutritional myodegeneration.

• Affected Species: Commonly seen in calves, lambs, and kids.

• Etiology: Caused by a deficiency in Vitamin $E$ and/or Selenium ($Se$).

• Pathology: The disease affects both skeletal and cardiac muscles.

• Clinical Presentation: In lambs with $Se$ deficiency, specific indicators of muscle degeneration are visible.

• Treatment: Involves the administration of Vitamin $E$ and Selenium injections.

• Prevention: Implementing a preventive diet in the dam (mother) to ensure adequate nutrient transfer to the offspring.

Enterotoxemia

• Synonyms: Known colloquially as "classic overeating disease" or "pulpy kidney disease."

• Prevalence: Recognized as one of the most common diseases in food animals.

• Causative Agent: Clostridium perfringens, specifically types $C$ and $D$.

• Pathogenesis: These bacteria produce lethal toxins. Fatal outcomes are common in lambs and kids.

• Predisposing Factors: A sudden change in diet can trigger the proliferation of bacteria that are already present in the gut. Inappropriate feeding practices, such as feeding bakery waste.

• Clinical Signs: Often affects the fastest-growing lambs within a flock.

• Management and Control:

  • Treatment: Primarily supportive care.

  • Vaccination: Administered to the pregnant ewe to provide passive immunity to the offspring.

Rumen Tympany (Bloat)

• Definition: An abnormal distention of the rumen caused by the accumulation of gas.

• Frothy Bloat:  

  • Cause: Overingestion of legumes or grains.

  • Mechanism: The formation of a stable froth traps gas and blocks the normal eructation (belching) process.

• Free Gas Bloat:

  • Mechanism: Due to a failure of eructation.

  • Associated Conditions: Esophageal foreign bodies (choke), motor abnormalities, or lateral recumbency (lying on the side).

• Clinical Observation: When viewing a bloated calf from the rear, the left side appears distended.

• Treatment Strategies:

  • General: Treatment depends heavily on the specific type and underlying cause.

  • Free Gas Bloat Treatment: Passing a stomach tube via the nasogastric or orogastric route to release gas. Administration of rumen stimulants to improve motility and restore normal belching.

  • Frothy Bloat Treatment: The froth must be consolidated into larger pockets of gas before it can be expelled.

  • Emergency Intervention: Trocarization using a rumen cannula (trocar) is performed in critically bloated animals.

  • Long-term Management: Nutritional management is essential for prevention.

Bovine Viral Diarrhea (BVD) and Johne’s Disease

• Bovine Viral Diarrhea (BVD):

  • Characteristics: A common virus-induced gastroenteritis that can affect cattle of all ages.

  • Persistent Infection (PI): Persistent infection in young animals may lead to the development of Mucosal Disease (MD) later in life.

  • Mortality: Mucosal Disease carries a mortality rate of $100\%$.  

  • Clinical Management: Focuses on diagnosis and vaccination protocols.

• Johne’s Disease: Causative Agent: Mycobacterium paratuberculosis.

  • Clinical Signs: Severe emaciation, intermandibular edema (swelling under the jaw), and chronic diarrhea.

Bovine Respiratory Disease Syndrome (BRDS)

• Definition: A complex syndrome resulting from the interaction of respiratory viruses, bacteria, and stress.

• Terminology: BRDS in feedlot cattle is specifically referred to as "shipping fever."

• Primary Viral Components:

  • Infectious Bovine Rhinotracheitis (IBR).

  • Bovine Viral Diarrhea (BVD).     

  • Parainfluenza virus ($PI3$).     

  • Bovine Respiratory Syncytial Virus (BRSV).    

  • Respiratory Coronavirus.

Ovine Progressive Pneumonia (OPP)

• Overview: A disease in sheep that results in progressive respiratory failure.

• Manifestations:

  • Pulmonary form (predominant in the United States).     

  • Mastitis (referred to as "hard bag").     

  • Neurologic signs.     

  • Arthritis.

• Clinical Signs: Exercise intolerance, open-mouth breathing, exaggerated expiratory effort, and an occasional dry cough. Weight loss occurs in later stages despite the animal maintaining a good appetite.

• Pathology: Causes interstitial pneumonia.

• Prognosis: Affected animals usually die within $3-8\,\text{months}$ after the onset of clinical symptoms.

• Diagnosis: Based on clinical signs, necropsy findings, and serology testing.

Mastitis in Cattle

• Definition: Inflammation of the mammary gland typically caused by the invasion of the streak canal of the teat by bacterial pathogens.

• Predisposing Factors:     

  • Environmental conditions.    

  • Physical injury.     

  • Issues with milking machine equipment.

• Clinical Classifications:     

  • Asymptomatic/Subclinical: No visible changes in milk or udder; detected via testing for somatic cells.     

  • Clinical: Visible signs of inflammation and changes in milk.     

  • Contagious vs. Environmental: Based on the source of the pathogen.

• Diagnosis:

  • Clinical: Physical examination of the milk and udder.

  • Subclinical: The California Mastitis Test (CMT), which identifies increased somatic cell counts.

• Prevention (The Five-Point Plan):     * 1. Hygiene: Includes both pre-milking and post-milking sanitation.     * 2. Proper Milking Procedures.     * 3. Dry Cow Treatment (antibiotics given at the end of lactation).     * 4. Culling: Removing chronically infected cows from the herd.     * 5. Record Maintenance: Keeping detailed health records.

Periparturient Hypocalcemia

• Common Names: Milk fever, hypocalcemia, or puerperal tetany.

• Target Population: Periparturient (near the time of giving birth) dairy cows.

• Etiology: A decline in serum calcium levels caused by the lag in mobilization of calcium reserves from the body, influenced by diet and the parathyroid gland.

• Clinical Signs:     * Sternal or lateral recumbency (inability to stand).     * Muscle twitching and tachycardia.     * Characteristc "S" shape to the neck.     * Head resting on the hindquarters.     * Hyperexcitability, ataxia (incoordination), head bobbing, and shuffling of feet.     * Cold extremities.     * Bloat, gastrointestinal (GI) stasis, and a lack of defecation.

• Treatment: Must be administered quickly; typically involves Intravenous (IV) Calcium Gluconate.

• Prevention:     * Providing a well-balanced, low-calcium diet during the dry period.     * Maintaining separate housing for dry cows to strictly control their dietary intake.

Neoplastic and Contagious Conditions

• Lymphosarcoma:     * The most common neoplastic (cancerous) disease in cattle.     * Typically affects cattle between the ages of $2$ and $6\,\text{years}$.     * Locations for malignant tumors: Spinal column (leading to an inability to rise), eyes, abomasum, heart, kidneys, and uterus.

• Caseous Lymphadenitis (CL):     * Causative Agent: Corynebacterium pseudotuberculosis.     * Impact: Highly contagious; the most common cause of lymph node abscesses in small ruminants.     * Management: Surgical removal, lancing/flushing of abscesses, long-term antimicrobials, formalin/antimicrobial injections, culling, or vaccination.

• Anthrax:     * Causative Agent: Bacillus anthracis (spore-forming bacteria).     * Characteristics: Acute disease causing sudden death; endemic in parts of the southern United States.     * Warnings: Avoid necropsy to prevent spore release; carcasses require specific disposal.     * Treatment: Penicillin (though rarely treated in time).     * Public Health: Considered a bioterrorism agent; zoonotic risk.

Cardiovascular and Neurological Diseases

• Pericarditis:     * Development: Penetration of the pericardial sac by a metallic foreign body (often called traumatic pericarditis or reticuloperitonitis).     * Pathology: Mixed bacterial infection and severe inflammation with exudates.     * Treatment: Very difficult; requires long-term antibiotics.

• Scrapie:     * Classification: Transmissible spongiform encephalopathy (TSE) caused by an infectious prion protein.     * Signs: Primarily significant weight loss.     * Diagnostics: Biopsy for antemortem diagnosis; postmortem confirmation is required.     * Legal Status: A reportable disease; genetic testing is available for management.

Conditions of the Integument and Oral Cavity

• Foot Rot (Interdigital Necrobacillosis):     * Cattle Cause: Fusobacterium necrophorum.     * Small Ruminant Cause: Dichelobacter nodosus and Fusobacterium necrophorum.     * Sign: Lameness in multiple animals.

• Papillomatous Digital Dermatitis (PDD):     * Commonly known as "Hairy Heel Wart."     * Causes superficial inflammation of the digit, progressing to mature lesions and granulation tissue. Treated with footbaths and antibiotics.

• Blackleg and Malignant Edema:     * Causes: Clostridium chauvoei (Blackleg) and Clostridium septicum (Malignant Edema).     * Result: Necrotizing myositis and cellulitis; causes sudden death in young cattle. Prevented with bacterin vaccines.

• Cutaneous Papillomas (Warts):     * Caused by the Papilloma virus in young cattle. Often self-limiting, though they can be crushed or surgically removed.

• Contagious Ecthyma (Soremouth/Orf):     * Viral disease in small ruminants causing lesions on lips and udders. It is zoonotic (spreads to humans).

• Wooden Tongue and Lumpy Jaw:     * Wooden Tongue: Caused by Actinobacillus lignieresii; involves abscessation of the tongue.     * Lumpy Jaw: Caused by Actinomyces bovis; results in bony masses on the mandible or maxilla and is generally difficult to treat.

Questions & Discussion

• Visual Diagnosis of Bloat: How is bloat identified from a distance?     * Response: By viewing the calf from the rear; the left side will show significant distention.

• Treatment of Soremouth: Is there a specific cure for Contagious Ecthyma?     * Response: The disease is typically self-limiting. Treatment focuses on supportive therapy and antimicrobials to prevent secondary bacterial infections. Caution must be taken with the live vaccine as it is zoonotic.