Novel insights in the pathogenesis and control of necrotic enteritis/dysbacteriosis in broilers Prof. Dr. F. Van Immerseel Ghent University Faculty of Veterinary Medicine Dept. Pathology, Bacteriology and Avian Diseases
Gut health: what are important factors? Nutrition •
Optimal nutritional quality, free of pathogens and toxins
•
Feed should be broken down by digestive and non-digestive enzymes, to exclude presence of residual nutrients in gastrointestinal tract
•
Viscosity should be low
•
Nutrition and feed additives can influence gut microbiota composition
•
Using nutrition changes we can predispose to NE/dysbacteriosis
Gut health: what are important factors? Gut microbiota composition •
Both quantity and quality are important, depending on gastrointestinal segment ileum
• •
Lactobacillus
cecum
Clos tridium
Clostridium
Enterococcus
Ruminococcus
Streptococcus
Fusobacterium
Weisella
Eubacterium
Staphylococcus
Lactobacillus
Campylobacter
Bacteroides
Eubacterium
Bacillus
Fusobacterium
Escherichia
Bacillus
Enterococcus
other
other
Stability and diversity of microbiota is important ! Richness (number of species) and eveness (relative abundance of species) are important !
Gut health: what are important factors? Gut wall morphology and integrity •
Villus structure should be optimal to preserve absorptive surface
•
Epithelial cell proliferation and differentiation should be optimal
•
Lesions/erosions should be avoided
•
Epithelial cell damage or junction defects should be avoided
Gut health: what are important factors? Inflammation •
Immune cell infiltration should be kept as low as possible, without interfering with normal repsonses
Factors affecting gut health Gut wall morphology, integrity and inflammation Balanced intestinal microflora Optimal gut health
Nutrition and management
Optimal animal performance
Necrotic enteritis Worldwide estimated losses due to necrotic enteritis:
2 billion $ annually Ban on antibiotic growth promoters (AGP) in EU (01-01-2006)
•
Enteric disease in broilers
•
Age-specific onset, 2-4 weeks post hatch
•
Clostridium perfringens
daily weight gain (gram)
Clostridial Enteritis – The Profit Killer 70 60 50 40 30 20 10 0
Typical growth retardation caused by clostridial enteritis at the third week of life
7
14
21
28
35
42
days Control broiler
Broiler with Clostridium infection
Only after 10-12 days of life an anaerobic microflora is established in the gut
In practice, necrotic enteritis in chicken occurs mostly between 1535 days of life, with a peak at 20-25 days of life Source: Sluis W Van Der, World Poultry 2000
Onset of necrotic enteritis
+ not necessarily disease!!
PREDISPOSING FACTORS !!
Predisposing factors
•
Coccidiosis
•
Feed
•
Others - Hygiene / shed management - Stocking density - Immunosuppression
Experimental in vivo model for sub-clinical NE d16 Gumboro vaccine Feed + ďŹ shmeal (30%)
d17
d18
d19
d20
d21
d22
d23
d24
x
x
x
x
x
x
x
x
x
x x
x
x
x
10-fold dose of Paracox-5 Oral inoculation with C. perfringens strain 56 Autopsy
x x
x
40-70% of infected birds present necrotic lesions (Gholamiandehkordi et al., 2007)
Experimental in vivo model for sub-clinical NE Necrotic lesions
Testing different C. perfringens strains
Isolate number
Health status of the flock of origin
Toxinotype
Alfa toxin production
7
Healthy
A
Low
8
Healthy
A
Intermediate
17
Healthy
A
High
48
Necrotic enteritis
A
High
56
Necrotic enteritis
A
Intermediate
61
Necrotic enteritis
A
Low
Testing different C. perfringens strains
percentage of animals with lesions
Results 60 50 40 30 20 10 0 negative paracox control
7
8
17
48
56
61
group
• Only isolates from NE cases induce necrotic lesions • Ability to induce disease is independent of ability to produce alpha toxin
Necrotic enteritis specific toxin
Strain
Birds with lesions (%)
netB
7
0
-
8
0
-
17
0
-
48
11.11
+
56
48.15
+
61
55.56
+
Different C. perfringens toxins, different activities, different host range?
ε
ι
netB
α
α HOST-SPECIFIC TOXINS ???
α
ε β
in x to o er t En
β
NetB toxin NetB mutant is unable to cause necrotic lesions !
Keyburn et al. (2008). PLOS Pathog. 4(e26).
Single strain dominance • Isolates from a NE outbreak are highly clonal in the flock
• C. perfringens strains isolated from broilers are genetically heterogeneous
‘Spot-the lawn’ test Results
growth inhibition
no growth inhibition
• Virulent strains are more capable of inhibiting other C. perfringens strains • Strains that produce peptides that inhibit other C. perfringens strains overgrow the others
Gr an ul rim ocy
Necrotic tissue Bacteria
te
What can we do? •Kill the bacteria •Prevent predisposing factors •Coccidiosis (ionophores ...) • Stocking density, hygiene, ... • Optimize nutritional quality
•Vaccination? e.g. netB toxoid •Feed additives?
٢٢
Treatment with therapeutic antibiotics • Infection from day 17 until day 20 • Treatment in the drinking water from day 20 until day 24
٢٣
Treatment with therapeutic antibiotics Percentage of birds with necrotic lesions over the 3 sampling days
(Lanckriet et al., 2010) ٢٤
Protective effects of ionophore anticoccidials
• Treatment in-feed from day 1
٢٥
Protective effects of ionophore anticoccidials
Percentage of birds with necrotic lesions over the 3 sampling days
(Lanckriet et al., 2010) ٢ٌ
Protective effects of certain feed additives Treatment in-feed from day 1
Protective effects of certain feed additives Percentage of birds with necrotic lesions over the 3 sampling days
(Timbermont et al., 2010)
Vaccination ? (netB? Toxoid? Crude SN?) Percentage of birds with necrotic lesions over the 3 sampling days
Dysbacteriosis ‘Trendy’ term pointing to a condition in which composition of microbiota is capable of decreasing performance due to poorly described mechanisms, although pathogens are not necessarily present
Synonyms ??? Feed passage syndrome Malabsorption syndrome Wet litter syndrome …..
Macroscopic scoring •
Figure. Macroscopic dysbacteriosis score system parameters.
• •
A. Overall gut ballooning; B. Content of the intestinal tract, 1. Mucoid, orange intestinal content, 2. Foamy intestinal content; C. Tonus of the intestinal tract, 1. Good tonus, 2. Lack of tonus; D. Macroscopically visible thickness of the intestinal tract, 1. Macroscopically thin intestinal tract, 2. Intestinal tract with normal thickness; E. Undigested particles in the colon (arrows); F. Inflammation of the gut, 1. Inflammation, 2. No inflammation.
• • • •
2 - 8
villus leng th (um )
2200 2000 1800 1600 1400 1200 1000
1
2
3
4
5
6
macroscopic dysbacteriosis score
7
8
musclar layer thickness (um)
measured in Âľm in broilers at 21 days
250
2 - 8
200 150 100 50 0 1
2
3
4
5
6
macroscopic dysbacteriosis score
7
8
T-cell infiltration (% area)
9 8 7 6 5 4 3 2 1 0
2 - 8
1
2
3
4
5
6
macroscopic dysbacteriosis score
7
8
Dysbacteriosis: macrocopical signs in the gut
• Inflammation • Morphological damage (villi length decreases, apoptosis, goblet cell proliferation) • Tunica muscularis thinning
Microbiota composition?
• Is it a dysbiosis of the gut microbiota???
Poly- or oligosaccharides
-oses
Sulphate Lactate
Acetate
Sulphate-reducing bacteria H2S
Clostridium cluster XIVa
Butyrate
Clostridium cluster IV
How to control dysbacteriosis? • Antibiotics • Feed composition • Products that are – Antibacterial – Anti-inflammatory – Shift bacterial microbiota composition
Preventive products • Acids • Essential oils • Prebiotics: steering the microbiota composition to a favorable one (anti-inflammatory, less epithelial damage) – Manno-oligosaccharides – Fructo-oligosaccharides – …
Thanks for your attention !