Bacterial and viral pathogens of the bovine GI tract Flashcards
Actinomycosis is a commensal pathogen of which area?
Oral cavity
When is Actinomycosis most likely to cause disease?
More common if cattle fed very coarse feed that can cause damage to the buccal mucosa and gums.
What are the clinical signs/findings with Actinomycosis infection?
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.
How can Actinomycosis be treated?
- Debridement and antibacterial therapy.
- Oral or iv iodine is most commonly used ± parental penicillin or oxytetracycline.
- Removal of coarse roughage from the diet
Where is Actinobacillosis a commensal of?
The upper GI tract
When is infection with Actinobacillosis most likley?
More common if grazing abrasive pasture plants that can cause damage to the alimentary mucosa.
What are the clinical signs/findings with Actinobacillosis infection?
- Difficulty with prehension and mastication.
- Swelling and abscessation of tongue and draining lymph nodes in cattle and of lips in sheep.
How is Actinobacillosis treated?
Oral or IV iodides
What is another name for laryngeal necrobacillosis?
Calf diphtheria
Describe the aetiology of Oral (necrotic stomatitis) and laryngeal (calf diphtheria) necrobacillosis
- Fusobacterium necrophorum a gram-negative, non-spore forming, rod-shaped anaerobic but aerotolerant organism.
- Commensal of alimentary tract.
What are the clinical signs/findings with Oral (necrotic stomatitis) and laryngeal (calf diphtheria) necrobacillosis infection?
- Fetid breath.
- Necrotic lesions of oral mucosa (necrotic stomatitis) or larynx (calf diphtheria).
- Inspiratory dyspnoea and stridor.
Describe the aetiology of Salmonellosis
- Gram-negative, rod-shaped bacilli
- Major food-borne pathogen of humans
Describe where Salmonellosis infection occurs/spreads in the body, in normal and immunocompromised animals
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).
What are the common routes of Salmonella infection?
- 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.
What are some risk factors for clinical salmonellosis?
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.
What are some clinical signs of GI Salmonellosis?
- 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
How is Salmonellosis treated and controlled?
- Antimicrobials (controversial)
- Oral and intravenous fluids and NSAIDs
- Vaccination
- Biosecurity and hygiene
What acts as a risk factor for Clostridium perfringes going from a normal GI tract inhabitant to a disease causing bacteria?
Surplus carbohydrate or protein that exceeds the capacity of the intestine to absorb it are used for bacterial growth and toxin production
Why is treatment for Clostridium perfringes often ineffective?
Because the disease is too acute
Describe the disease caused by Clostridium perfringes type A
- Haemorrhagic enterotoxaemia
- Haemolytic disease
- Abomasal ulcers
What clinical signs present with Clostridium perfringes type A infection?
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
Clostridium perfringens types B and C mostly affects which group of animals?
Predominant in very young animals, particularly fast-growing, well-nourished animals (check vaccine status)
Describe the disease caused by Clostridium perfringes type B and C
Typically presents acutely with haemorrhagic diarrhoea, abdominal pain, and toxaemia.
What is the major source of infection for BVD?
The persistently infected (PI) viraemic animal
Describe persistently infected BVD cattle
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.
Aside from direct transmission, how else can BVD spread?
Flies, fomites (hypodermic needles), airborne transmission, AI/ET, and possibly rectal palpation
Describe the pathogenesis of BVD
Transient immune suppression occurs in acutely infected animals. Innate and adaptive immune cells infected.
What are the clinical signs of subclinical BVD in immunocompetent non-pregnant cattle?
Mild transient disease with inappetence, depression, fever, leukopenia, and mild diarrhoea.
What are the clinical signs of peracute BVD?
Respiratory disease, depression, anorexia, profuse watery diarrhoea ± blood, conjunctivitis, fever (40+C)
What is mucosal disease, which animals does it affect?
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
Describe the lesions of mucosal disease
Characterized by small ulcers that affect only epithelial cells; consequently, they are found throughout the GI and respiratory tracts. Vasculitis also occurs.
What are the clinical signs of acute mucosal disease?
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.
How can you treat mucosal disease?
There is no treatment, but it can be prevented by detecting and eradicating persistently infected animals
Describe the epidemiology of winter dysentery (coronavirus)
- Faeco-oral transmission.
- High morbidity, low mortality.
- Typically occurs in winter months in housed cattle
What are the clinical signs of winter dysentery (coronavirus)
Sudden onset of diarrhoea among majority of herd. Fever, milk drop, inappetance and recovery within a few days. Enterocolitis.
How is Winter dysentery treated and controlled?
Treatment: None.
Control: Hygiene. Reduce overcrowding
What is the most appropriate preventative measure for actinomycosis (lumpy jaw)?
- Remove coarse feed from diet
- No vaccine available for this
A swelling centred on the caudal buccal cavity and/or laryngeal region is caused by?
Laryngeal necrobacillosis
Salmonella may manifest as…?
Enteritis, abortion, septicaemia
