novel insights in the pathogenesis and control of necrotic enteritis/dysbacteriosis in broilers
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Novel insights in the pathogenesis and control of necrotic enteritis/dysbacteriosis in broilersTRANSCRIPT
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Novel insights in the pathogenesis and control of necrotic enteritis/dysbacteriosis in broilers
Prof. Dr. F. Van ImmerseelGhent University
Faculty of Veterinary MedicineDept. Pathology, Bacteriology and Avian Diseases
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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 gastro-intestinal tract
• Viscosity should be low
• Nutrition and feed additives can influence gut microbiota composition
• Using nutrition changes we can predispose to NE/dysbacteriosis
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Gut health: what are important factors?Gut microbiota composition
• Both quantity and quality are important, depending on gastro-intestinal segment
• Stability and diversity of microbiota is important !• Richness (number of species) and eveness (relative abundance
of species) are important !
ileum LactobacillusClostridiumEnterococcusStreptococcusWeisellaStaphylococcusCampylobacterEubacteriumFusobacteriumBacillusother
cecumClostridiumRuminococcusFusobacteriumEubacteriumLactobacillusBacteroidesBacillusEscherichiaEnterococcusother
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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
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Gut health: what are important factors?Inflammation
• Immune cell infiltration should be kept as low as possible, without interfering with normal repsonses
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Factors affecting gut health
Optimal gut health
Balanced intestinal microflora
Optimal animal performance
Nutrition and management
Gut wall morphology, integrity and inflammation
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Necrotic enteritisNecrotic enteritis
• Enteric disease in broilers
• Age-specific onset, 2-4 weeks post hatch
• Clostridium perfringens
Worldwide estimated losses due to necroticenteritis:
2 billion $ annually
Ban on antibiotic growth promoters (AGP) in EU (01-01-2006)
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Clostridial Enteritis – The Profit Killer
Typical growth retardation caused by clostridial enteritis at the third week of life
Source: Sluis W Van Der, World Poultry 2000
In practice, necrotic enteritis in chicken occurs mostly between 15-35 days of life, with a peak at 20-25 days of life
Only after 10-12 days of life an anaerobic microflora is established in the gut
010203040506070
7 14 21 28 35 42days
daily
wei
ght g
ain
(gra
m)
Control broiler Broiler with Clostridium infection
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Onset of necrotic enteritisOnset of necrotic enteritis
+
not necessarily disease!!
PREDISPOSING FACTORS !!
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Predisposing factorsPredisposing factors
• Coccidiosis
• Feed
• Others
- Hygiene / shed management
- Stocking density
- Immunosuppression
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d16 d17 d18 d19 d20 d21 d22 d23 d24
Gumboro vaccine x
Feed + fishmeal (30%) x x x x x x x x
10-fold dose of Paracox-5 x
Oral inoculation with
C. perfringens strain 56x x x x
Autopsy x x x
Experimental in vivo model for sub-clinical NEExperimental in vivo model for sub-clinical NE
40-70% of infected birds present necrotic lesions(Gholamiandehkordi et al., 2007)
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Experimental in vivo model for sub-clinical NEExperimental in vivo model for sub-clinical NE
Necrotic lesions
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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 strainsTesting different C. perfringens strains
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0
10
20
30
40
50
60
negative control
paracox 7 8 17 48 56 61
per
cen
tage
of a
nim
als
wit
h le
sio
ns
group
Testing different C. perfringens strainsTesting different C. perfringens strains
Results
• Only isolates from NE cases induce necrotic lesions
• Ability to induce disease is independent of ability to produce alpha toxin
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Strain Birds with lesions (%) netB
7 0 -
8 0 -
17 0 -
48 11.11 +
56 48.15 +
61 55.56 +
Necrotic enteritis specific toxinNecrotic enteritis specific toxin
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Different C. perfringens toxins, different activities, different host range?
HOST-SPECIFIC TOXINS ???
εβ
ε ι
βEnter
otoxin
netB
α
α
α
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NetB toxin
NetB mutant is unable to cause necrotic lesions !
Keyburn et al. (2008).
PLOS Pathog. 4(e26).
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Single strain dominanceSingle strain dominance
• Isolates from a NE outbreak are highly clonal in the flock
• C. perfringens strains isolated from broilers are genetically heterogeneous
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‘Spot-the lawn’ test‘Spot-the lawn’ test
growthinhibition
no growthinhibition
Results
• Virulent strains are more capable of inhibiting other C. perfringens strains
• Strains that produce peptides that inhibit other C. perfringens strains
overgrow the others
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Granulocyte rim
Bacteria
Necrotictissue
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What can we do?
٢٢
•Kill the bacteria
•Prevent predisposing factors•Coccidiosis (ionophores ...)• Stocking density, hygiene, ...• Optimize nutritional quality
•Vaccination? e.g. netB toxoid
•Feed additives?
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Treatment with therapeutic antibiotics
٢٣
• Infection from day 17 until day 20
• Treatment in the drinking water from day 20 until day 24
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Treatment with therapeutic antibiotics
٢٤
Percentage of birds with necrotic lesions over the 3 sampling days
(Lanckriet et al., 2010)
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Protective effects of ionophore anticoccidials
٢٥
• Treatment in-feed from day 1
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Protective effects of ionophore anticoccidials
٢٦
Percentage of birds with necrotic lesions over the 3 sampling days
(Lanckriet et al., 2010)
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Protective effects of certain feed additivesProtective effects of certain feed additives
Treatment in-feed from day 1
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Protective effects of certain feed additivesProtective effects of certain feed additives
Percentage of birds with necrotic lesions over the 3 sampling days
(Timbermont et al., 2010)
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Vaccination ? (netB? Toxoid? Crude SN?)Vaccination ? (netB? Toxoid? Crude SN?)
Percentage of birds with necrotic lesions over the 3 sampling days
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‘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 necessarilypresent
Synonyms ???Feed passage syndromeMalabsorption syndromeWet litter syndrome…..
Dysbacteriosis
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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.
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1000120014001600180020002200
1 2 3 4 5 6 7 8macroscopic dysbacteriosis score
villu
s le
ngth
(um
)
2 - 8
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measured in µm in broilers at 21 days
0
50
100
150
200
250
1 2 3 4 5 6 7 8
macroscopic dysbacteriosis score
mus
clar
laye
r thi
ckne
ss (u
m) 2 - 8
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0123456789
1 2 3 4 5 6 7 8macroscopic dysbacteriosis score
T-ce
ll in
filtra
tion
(% a
rea)
2 - 8
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Dysbacteriosis: macrocopical signs in the gut
• Inflammation• Morphological damage (villi length decreases,
apoptosis, goblet cell proliferation)• Tunica muscularis thinning
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Microbiota composition?
• Is it a dysbiosis of the gut microbiota???
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Poly- or oligosaccharides
-oses
Lactate Acetate
Butyrate
Sulphate
H2S
Sulphate-reducingbacteria
Clostridium cluster XIVa
Clostridium cluster IV
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How to control dysbacteriosis?
• Antibiotics• Feed composition• Products that are
– Antibacterial
– Anti-inflammatory
– Shift bacterial microbiota composition
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Preventive products
• Acids• Essential oils
• Prebiotics: steering the microbiota composition to a favorable one (anti-inflammatory, less epithelialdamage)– Manno-oligosaccharides– Fructo-oligosaccharides – …
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Thanks for your attention !