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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 !

Novel insights in the pathogenesis and control of necrotic enteritis/dysbacteriosis in broilers  

Novel insights in the pathogenesis and control of necrotic enteritis/dysbacteriosis in broilers

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