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MODULE 18 - Ruminant Production > PATHOLOGY - Calf Scour > Flashcards

PATHOLOGY - Calf Scour Flashcards

1
Q

What are the main risk factors for calf scour?

A

The main risk factors for calf scour are poor management and animal husbandry

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2
Q

What are the main things that can be done to prevent calf scour?

A

Boost calf immunity and resistance to disease
Minimise infection pressure

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3
Q

What can be done to boost calf immunity and resistance to disease?

A

Colostrum management

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4
Q

What can be done to minimise infectious pressure?

A

Housing management
Hygiene management
Stocking density
Manage sick calves

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5
Q

Which housing management practices can be used to prevent calf scour?

A
  1. Dry and draught free housing with good drainage and ventilation
  2. Calf housing should be at least 20 metres from the milking shed as adult cows can be a source of infection
  3. Within calving pens, calves should be no more than 5 days older than one another, as older calves can act as a source of infection for the younger calves
  4. Calves should be moved around the shed as little as possible
  5. House bobbies (male calves) seperately from the female calves
  6. Two metre high, solid partitions between the calf pens
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6
Q

Why should bobbies (male calves) be housed separately from the female calves?

A

Bobbies (male calves) should be housed separately from female calves as their management is often different and they may receive less colostrum than the females as they are not priositised as much as the heifer replacement calves (which will be worth more economically). Thus, the males will be at an increased risk of disease and can be a source of infection

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7
Q

Which hygiene management practices can be used to prevent scour?

A

Clean dry bedding
Regularly refresh bedding during calving season
Replace bedding completely between calving seasons

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8
Q

Which stocking density practices can be used to prevent scour?

A

Minimum of 1.5m^2 per calf (aim for min of 2 - 3m^2)
No more than 100 calves per shed
No more than 20 calves per pen

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9
Q

How should you manage sick calves to reduce the spread of calf scour?

A

Quarantine bought in animals
Remove sick calves prompty from the healthy calves
Biosecurity
Feed sick calves last and with seperate feeders of possible

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10
Q

What are the three pathophysiological mechanisms of calf scour?

A

Secretory diarrhoea
Osmotic diarrhoea
Malabsorptive diarrhoea

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11
Q

Describe briefly the pathophysiology of secretory diarrhoea

A

Secretory diarrhoea is when fluid secretion from the intestine exceeds absorptive capacity. Bacteria can release endotoxins which ultimately result in reduced sodium absorption by the villous cells and increased chloride secretion by the crypt cells

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12
Q

Describe briefly the pathophysiology of osmotic diarrhoea

A

Osmotic diarrhoea is when substances within the intestinal lumen exert osmostic pressure, drawing fluid into the lumen. This can be caused by sodium and chloride within the lumen, but also unabsorbed molecules of a dietary origin

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13
Q

Describe briefly the pathophysiology of malabsorptive diarrhoea

A

Malabsorptive diarrhoea can be caused by passive malabsorption of fluid from the intestinal lumen due to villous atrophy and morphological changes to the absorptive surface of the intestine. Crypt hyperplasia can also occur and immature secretory cells can migrate onto the villi and increase secretory capacity, contributing to the diarrhoea

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14
Q

What are the two main classifications of calf scour?

A

Nutritional scour
Infectious scour

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15
Q

What are some of the potential causes of nutritional scour in calves?

A

Excess volumes of milk
Feeding at the wrong temperatures or concentrations
Irregular feeding times

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16
Q

Which bacteria can cause calf scour?

A

E. coli
Salmonella
Campylobacter

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17
Q

Describe the morphological characteristics of E. coli

A

E. coli is a Gram negative, facultatively anaerobic, rod bacteria

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18
Q

What is the pathogenesis of enterotoxic E. coli (ETEC)?

A

Enterotoxic E. coli (ETEC) adheres to the microvilli on the intestinal epithelium via the K99 antigen which allows the bacteria to bind to the intestinal epithelium, and produce heat labule and heat stable toxins. Heat labile toxins stimulate Cl- secretion from the enterocytes. Heat stable toxins inhibit the Na+/Cl- co-transporters on the surface enterocytes and stimulate Cl- and water secretion from the crypt enterocytes, resulting in secretory and osmotic diarrhoea

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19
Q

What is the typical signalement for enterotoxic E.coli (ETEC) mediated scour?

A

Enterotoxic E. coli (ETEC) causes scour in calves less than 5 days old

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20
Q

What are the clinical signs of enterotoxic E.coli (ETEC) mediated scour?

A

Profuse, four smelling scour
Wet mouth
Abdominal distension
± Blood in the scour
± Pyrexia
± Systemic clinical signs

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21
Q

Which strains of E. coli cause scour in older calves?

A

Enteropathogenic E. coli (EPEC)
Enterohaemorrhagic E. coli (EHEC)

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22
Q

What is the pathogenesis of enteropathogenic E. coli (EPEC)?

A

Enteropathogenic E. coli (EPEC) adheres to and translocates into the enterocytes, resulting in damage to and loss of the microvilli, compromising the absorptive capacity of the enterocytes resulting in malabsorptive diarrhoea

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23
Q

What is the pathogenesis of enterohaemorrhagic E. coli (EHEC)?

A

Enterohaemorrhagic E. coli (EHEC) produces Stx1 and Stx2 of shiga toxin (verotoxin) which causes inhibition of protein synthesis and enterocyte apoptosis, compromising the absorptive capacity of the intestinal epithelium, resulting in absorptive diarrhoea

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24
Q

Which species of salmonella most commonly cause calf scour?

A

Salmonella typhimurium
Salmonella dublin

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25
What is the pathogenesis of salmonella?
Salmonella adheres to and invades the intestinal epithelial cells mediated by fimbriae. Salmonella preferentially adheres to and invades M-cells, however invasion via enterocytes also occurs. Within the intestinal epithelium, endocytosis occurs which forms vacuoles which translocate the salmonella to the lamina propria macrophages. Salmonella neutralise the nitric oxide within the macrophages and then reside within the phagylolysosomes. Salmonella toxins trigger acute inflammation of the gastrointestinal tract, as well as cause enterocyte damage and interference of closure of Cl- channels resulting in secretory diarrhoea. Salmonella toxins can also cause vascular thrombosis. The macrophages transport the salmonella to the mesenteric lymph nodes and then to the liver via the hepatic portal system
26
What is the typical signalement for salmonella mediated scour?
Salmonella causes scour in calves of any age, but mainly calves less than 2 months old
27
What are the clinical signs of salmonella mediated scour?
Scour Pyrexia ± Blood in the scour
28
Which viruses can cause calf scour?
Rotavirus Coronavirus
29
What is the pathogenesis of rotavirus?
Rotavirus invades and replicates within the enterocytes, followed by destroying the enterocytes resulting in secretory and malabsorptive diarrhoea
30
Which signalement is typically affected by rotavirus mediated scour?
Rotavirus typically causes scour in calves between 5 to 21 days old
31
What are the clinical signs of rotavirus mediated scour?
White scour Dehydration
32
(T/F) Coronavirus mediated scour is very similar to rotavirus mediated scour
TRUE.
33
Which parasites can cause calf scour?
Cryptosporidium parvum Coccidiosis Helminths
34
What is the pathogenesis for cryptosporidium parvum?
Cryptosporidium parvum cause invagination of the intestinal luminal membrane and causes villous atrophy, crypt hyperplasia and enterocyte apoptosis, resulting in malabsorptive and osmotic diarrhoea
35
What is the typical signalement for cryptosporidium parvum mediated scour?
Cryptosporidium parvum typically causes scour in calves between 1 week and 3 months old
36
What are the clinical signs of cryptosporidium parvum mediated scour?
Scour Dehydration
37
Why is cryptosporidium parvum so challenging to remove from the environment?
Cryptosporidium parvum oocysts persist in the enviornment and are very challenging to kill
38
What is required to kill cryptosporidium parvum oocysts in the environment?
Ammonia-based disinfectants
39
What is the pathogenesis for coccidiosis?
Coccidia cause enterocyte rupture resulting in malabsorptive and osmotic diarrhoea
40
What is the typical signalement for coccidia mediated scour?
Coccidia mediated scour typically affects calves between 3 weeks to 3 months old
41
What are the clinical signs of coccidia mediated scour?
Black/bloody scour Abdominal pain Faecal tenesmus
42
What is necrotic enteritis?
Necrotic enteritis is condition of unknown aetiology which affects 7 to 9 week old beef calves, usually when they have been put out to grass
43
What are the clinical signs of necrotic enteritis?
Pyrexia Bloody scour Anaemia
44
How do you diagnose the cause of calf scour?
Collect faecal samples from at least six of the sick calves and conduct faecal analysis, focusing on all of the major pathogens relevant to that age group. Additionally, taking faecal samples from healthy calves can provide a baseline for comparison. It is crucial to ensure that the calves being sampled haven't been treated with antibiotics as this can lead to inaccurate results
45
Which faecal analysis tests can you do to diagnose the cause of calf scour?
Bacterial culture Virology Parasitology ELISA
46
Why is it so important to diagnose the cause of calf scour?
It is important to diagnose the cause of calf scour in order to implement the correct prevention strategies
47
What are the consequences of calf scour?
Dehydration Hypovolaemia Pre-renal azotaemia Electrolyte imbalances Metabolic acidosis Hyperkalaemia
48
What causes metabolic acidosis in calf scour?
Intestinal bicarbonate loss Bacterial production of lactate Lactate production due to tissue hypoperfusion and anaerobic metabolism Pre-renal azotaemia resulting in decreased GFR and excretion of hydrogen ions
49
What are the clinical signs of metabolic acidosis in calves?
Progressive depression Decreased suckle reflex Reduced to absent palpebral reflex Weakness Comatose
50
Which factor kills scouring calves?
Dehydration
51
Which factors should you focus on during a clinical examination of a calf with scour?
Demeanour Hydration status Respiratory rate Nature of the scour Temperature Assess for metabolic acidosis
52
What is the main form of treatment for calf scour?
Fluid therapy
53
When is oral fluid therapy sutiable for the treatment of calf scour?
Oral fluid therapy is sutiable for the treatment of calf scour if the calf is less than 7% dehydrated with no clinical signs of metabolic acidosis
54
What are the aims of oral fluid therapy when treating calf scour?
Correct the fluid deficit Provide alkalinising agents to improve the buffering capacity of the blood Increase the strong ion difference by replacing lost sodium and potassium Maintain blood glucose levels
55
(T/F) Milk should still be fed alongside oral fluid therapy when treating calf scour
TRUE. Oral fluid therapy is crucial for correcting dehydration and electrolyte imbalances, but milk provides essential nutrients like protein and energy that are necessary for recovery. However, do not mix milk and fluid therapy (feed 1.5 hours apart) as the electrolytes can intefere with casein digestion within the abomasum
56
When is intravenous fluid therapy required for the treatment of calf scour?
Intravenous fluid therapy should be used if the calf is between 7 - 9% dehydrated with clinical signs of mild metabolic acidosis
57
What is the maintenance fluid rate for calves?
50 - 100ml/kg/day
58
How may litres of fluid should be administered to scouring calves to accommodate ongoing losses?
2 - 3 litres/day
59
Which fluid type is best for IV treatment of scouring calves?
Hartmannn's fluid
60
What is the fluid rate for intravenous fluid treatment of calf scour?
Administer IV fluids at a rate of 80ml/kg/hr for the first hour (i.e. fully open the giving set), and then reduce the rate to 30 - 50ml/kg/hr. Always follow up intravenous fluid therapy with oral fluid therapy
61
When is intravenous fluid therapy and 1.3% bicarbonate required for the treatment of calf scour?
Intravenous fluid therapy and 1.3% bicarbonate should be used in the treatment of calf scour if the calf is over 9% dehydrated with clinical signs of moderate to severe metabolic acidosis
62
How do you carry out a bicarbonate spike?
Add 13g of sodium bicarbonate to 1 litre of 0.9% NaCl or sterile water to form 1.3% bicarbonate
63
When is it appropriate to administer 1.3% bicarbonate to a scouring calf?
Only administer 1.3% bicarbonate if a calf is over 7 days old, you have corrected the fluid deficit with fluid therapy but they are still exhibiting clinical signs of metabolic acidosis
64
Why should you only administer 1.3% bicarbonate to calves over 7 days old?
Studies have shown that calves over 7 days old are much more likely to be in metabolic acidosis than calves less than 7 days old
65
How many litres of 1.3% bicarbonate should you administer to a scouring calf in sternal recumbency?
If the calf is less than or equal to 40kg and is in sternal recumbeny, administer 2 litres of 1.3% bicarbonate, however if they are above 40kg, administer 3 litres of 1.3% bicarbonate
66
How many litres of 1.3% bicarbonate should you administer to a scouring calf in lateral recumbency?
If the calf is less than or equal to 40kg and is in lateral recumbency, administer 3 litres of 1.3% bicarbonate, however if they are above 40kg, administer 4 litres of 1.3% bicarbonate
67
What is the main contraindication 1.3% bicarbonate adminstration in calves?
You should never administer 1.3% bicarbonate to calves in severe respiratory distress
68
Why is 1.3% bicarbonate contraindicated in calves in severe respiratory distress?
Bicarbonate is a buffer which binds to H+ within the bloodstream to form carbonic acid which rapidly dissociates into CO2 and water, increasing serum CO2 levels in the blood. This can exacerbate hypercapnia and respiratory acidosis as ventilation will be compromised in patients in severe respiratory distress. This will also decrease the pH within the cerebrospinal fluid as the blood CO2 will diffuse into the cerebrospinal fluid, decreasing the pH. This can result alter CNS function and present clinically as muscle tremors and fasciculations (twitches)
69
Which adjunctive treatments can be used for calf scour?
Antimicrobials Analgesia Specific cryptosporidium parvum treatment Specific coccidiosis treatment
70
Why is it contraindicated to administer oral antibiotics to animals that have diarrhoea?
Diarrhoea decreases gut transit time resulting in decreased absorption and bioavailability of the drug
71
When are antimicrobials indicated in the treatment of calf scour?
If you suspect E. coli or salmonella mediated scour Systemic clinical signs indicating septicaemia or secondary small intestinal bacterial overgrowth (SIBO) Blood in the scour
72
Which systemic clinical signs can indicate antimicrobials are required in the treatment of calf scour?
Pyrexia Lethargy Decreased appetite | Remember calves with scour are generally BAR
73
Which first line antibiotic should you use for calf scour?
Trimethoprim and potentiated sulphonamides (TMPS)
74
Which analgesia drugs can you use in the treatment of calf scour?
NSAIDs. However only when the fluid deficit is corrected as you risk nephrotoxicity
75
Which drug can be used to treat cryptosporidium parvum?
Halofuginone
76
Which drug can be used to treat and prevent coccidiosis?
Toltrazuril
77
What nursing care is required when treating calf scour (this will have to be done by the farmer)?
Isolation from other calves Keep warm (i.e. use calf jackets) Access to fresh, clean water Feed milk alongside fluid therapy Monitor response to treatment

MODULE 18 - Ruminant Production (30 decks)

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