Bacterial and viral pathogens of the bovine GI tract

Question 1

Actinomycosis is a commensal pathogen of which area?

Answer 1

Oral cavity

Question 2

When is Actinomycosis most likely to cause disease?

Answer 2

More common if cattle fed very coarse feed that can cause damage to the buccal mucosa and gums.

Question 3

What are the clinical signs/findings with Actinomycosis infection?

Answer 3

Hard, immovable lump (pyelogranulomatous osteomyelitis) on maxilla or mandible.
Initially painless but may become more painful and may ooze small amount of thick pus containing yellow-white granules.

Question 4

How can Actinomycosis be treated?

Answer 4

• Debridement and antibacterial therapy.
• Oral or iv iodine is most commonly used ± parental penicillin or oxytetracycline.
• Removal of coarse roughage from the diet

Question 5

Where is Actinobacillosis a commensal of?

Answer 5

The upper GI tract

Question 6

When is infection with Actinobacillosis most likley?

Answer 6

More common if grazing abrasive pasture plants that can cause damage to the alimentary mucosa.

Question 7

What are the clinical signs/findings with Actinobacillosis infection?

Answer 7

• Difficulty with prehension and mastication.

- Swelling and abscessation of tongue and draining lymph nodes in cattle and of lips in sheep.

Question 8

How is Actinobacillosis treated?

Answer 8

Oral or IV iodides

Question 9

What is another name for laryngeal necrobacillosis?

Answer 9

Calf diphtheria

Question 10

Describe the aetiology of Oral (necrotic stomatitis) and laryngeal (calf diphtheria) necrobacillosis

Answer 10

• Fusobacterium necrophorum a gram-negative, non-spore forming, rod-shaped anaerobic but aerotolerant organism.
• Commensal of alimentary tract.

Question 11

What are the clinical signs/findings with Oral (necrotic stomatitis) and laryngeal (calf diphtheria) necrobacillosis infection?

Answer 11

• Fetid breath.
• Necrotic lesions of oral mucosa (necrotic stomatitis) or larynx (calf diphtheria).
• Inspiratory dyspnoea and stridor.

Question 12

Describe the aetiology of Salmonellosis

Answer 12

• Gram-negative, rod-shaped bacilli

- Major food-borne pathogen of humans

Question 13

Describe where Salmonellosis infection occurs/spreads in the body, in normal and immunocompromised animals

Answer 13

Infection primarily occurs orally and organisms replicate in the submucosa and Peyer’s patches of the distal ileum and large intestine.
In immunocompromised animals, the organisms spread to the reticuloendothelial cells of the liver, and onto the bloodstream. This can occur rapidly (approximately 15 minutes in calves).

Question 14

What are the common routes of Salmonella infection?

Answer 14

• Common routes include contaminated feed and environment (soil, birds, rodents, water supplies), and during transport (shedding exacerbated by stress).
• Introduction of a carrier animal into a herd is a common cause of outbreaks.

Question 15

What are some risk factors for clinical salmonellosis?

Answer 15

Intensification of husbandry and changes that could cause stress (dietary change, pen change, feed withdrawal, heat stress, parturition), heavy grazing of land spread with slurry, contaminated feedstuffs, carrier animals (is there a livery on the farm?) and vehicles.

Question 16

What are some clinical signs of GI Salmonellosis?

Answer 16

• Morbidity and mortality greatest in calves < 12 weeks old. Case-fatality almost 100% if no treatment provided.
• Septicaemia, abortion, enteritis, and localized tissue infections such as arthritis, osteitis, and terminal dry gangrene (ear tips, tail, below fetlock).
• Infection of calves may cause death within 24 hours, necrotizing enteritis, malabsorption and diarrhoea

Question 17

How is Salmonellosis treated and controlled?

Answer 17

• Antimicrobials (controversial)
• Oral and intravenous fluids and NSAIDs
• Vaccination
• Biosecurity and hygiene

Question 18

What acts as a risk factor for Clostridium perfringes going from a normal GI tract inhabitant to a disease causing bacteria?

Answer 18

Surplus carbohydrate or protein that exceeds the capacity of the intestine to absorb it are used for bacterial growth and toxin production

Question 19

Why is treatment for Clostridium perfringes often ineffective?

Answer 19

Because the disease is too acute

Question 20

Describe the disease caused by Clostridium perfringes type A

Answer 20

• Haemorrhagic enterotoxaemia
• Haemolytic disease
• Abomasal ulcers

Question 21

What clinical signs present with Clostridium perfringes type A infection?

Answer 21

Haemolytic disease presents acutely with severe depression, collapse, mucosal pallor, jaundice, haemoglobinuria, dyspnea, and the presence of severe abdominal pain.
Kidneys are swollen and dark brown and the liver pale and swollen with extensive necrosis of the small intestine

Question 22

Clostridium perfringens types B and C mostly affects which group of animals?

Answer 22

Predominant in very young animals, particularly fast-growing, well-nourished animals (check vaccine status)

Question 23

Describe the disease caused by Clostridium perfringes type B and C

Answer 23

Typically presents acutely with haemorrhagic diarrhoea, abdominal pain, and toxaemia.

Question 24

What is the major source of infection for BVD?

Answer 24

The persistently infected (PI) viraemic animal

Question 25

Describe persistently infected BVD cattle

Answer 25

Virus can be found in all secretions including nasal discharge, faeces, saliva, semen, urine, tears, and milk.
PI animals can remain clinically normal for several years – need to test! Are fertile but will produce PI offspring.

Question 26

Aside from direct transmission, how else can BVD spread?

Answer 26

Flies, fomites (hypodermic needles), airborne transmission, AI/ET, and possibly rectal palpation

Question 27

Describe the pathogenesis of BVD

Answer 27

Transient immune suppression occurs in acutely infected animals. Innate and adaptive immune cells infected.

Question 28

What are the clinical signs of subclinical BVD in immunocompetent non-pregnant cattle?

Answer 28

Mild transient disease with inappetence, depression, fever, leukopenia, and mild diarrhoea.

Question 29

What are the clinical signs of peracute BVD?

Answer 29

Respiratory disease, depression, anorexia, profuse watery diarrhoea ± blood, conjunctivitis, fever (40+C)

Question 30

What is mucosal disease, which animals does it affect?

Answer 30

Fetal infection during approximately 45 – 120 days gestation may lead to persistent viraemia (PI animal) in the calf due to immunotolerance. May remain healthy for up to 5 years

Question 31

Describe the lesions of mucosal disease

Answer 31

Characterized by small ulcers that affect only epithelial cells; consequently, they are found throughout the GI and respiratory tracts. Vasculitis also occurs.

Question 32

What are the clinical signs of acute mucosal disease?

Answer 32

Fever (40+C), tachycardia, tachypnoea, poor or absent ruminal contractility, profuse, watery, and foul-smelling diarrhoea 2-4 days after onset of signs. Faeces may contain blood and fibrinous casts. Ulcers in mouth may become confluent to create large necrotic areas. Similar lesions on muzzle and nares. Mucopurulent nasal discharge, dehydration and weakness.

Question 33

How can you treat mucosal disease?

Answer 33

There is no treatment, but it can be prevented by detecting and eradicating persistently infected animals

Question 34

Describe the epidemiology of winter dysentery (coronavirus)

Answer 34

• Faeco-oral transmission.
• High morbidity, low mortality.
• Typically occurs in winter months in housed cattle

Question 35

What are the clinical signs of winter dysentery (coronavirus)

Answer 35

Sudden onset of diarrhoea among majority of herd. Fever, milk drop, inappetance and recovery within a few days. Enterocolitis.

Question 36

How is Winter dysentery treated and controlled?

Answer 36

Treatment: None.
Control: Hygiene. Reduce overcrowding

Question 37

What is the most appropriate preventative measure for actinomycosis (lumpy jaw)?

Answer 37

• Remove coarse feed from diet

- No vaccine available for this

Question 38

A swelling centred on the caudal buccal cavity and/or laryngeal region is caused by?

Answer 38

Laryngeal necrobacillosis

Question 39

Salmonella may manifest as…?

Answer 39

Enteritis, abortion, septicaemia