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

Prof. Dr. F. Van ImmerseelGhent University

Faculty of Veterinary MedicineDept. 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 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

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

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

Optimal gut health

Balanced intestinal microflora

Optimal animal performance

Nutrition and management

Gut wall morphology, integrity and inflammation

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)

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

Onset of necrotic enteritisOnset of necrotic enteritis

+

not necessarily disease!!

PREDISPOSING FACTORS !!

Predisposing factorsPredisposing factors

• Coccidiosis

• Feed

• Others

- Hygiene / shed management

- Stocking density

- Immunosuppression

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)

Experimental in vivo model for sub-clinical NEExperimental in vivo model for sub-clinical NE

Necrotic lesions

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

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

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

Different C. perfringens toxins, different activities, different host range?

HOST-SPECIFIC TOXINS ???

εβ

ε ι

βEnter

otoxin

netB

α

α

α

NetB toxin

NetB mutant is unable to cause necrotic lesions !

Keyburn et al. (2008).

PLOS Pathog. 4(e26).

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

‘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

Granulocyte rim

Bacteria

Necrotictissue

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?

Treatment with therapeutic antibiotics

٢٣

• Infection from day 17 until day 20

• Treatment in the drinking water from day 20 until day 24

Treatment with therapeutic antibiotics

٢٤

Percentage of birds with necrotic lesions over the 3 sampling days

(Lanckriet et al., 2010)

Protective effects of ionophore anticoccidials

٢٥

• Treatment in-feed from day 1

Protective effects of ionophore anticoccidials

٢٦

Percentage of birds with necrotic lesions over the 3 sampling days

(Lanckriet et al., 2010)

Protective effects of certain feed additivesProtective effects of certain feed additives

Treatment in-feed from day 1

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)

Vaccination ? (netB? Toxoid? Crude SN?)Vaccination ? (netB? Toxoid? Crude SN?)

Percentage of birds with necrotic lesions over the 3 sampling days

‘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

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.

1000120014001600180020002200

1 2 3 4 5 6 7 8macroscopic dysbacteriosis score

villu

s le

ngth

(um

)

2 - 8

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

0123456789

1 2 3 4 5 6 7 8macroscopic dysbacteriosis score

T-ce

ll in

filtra

tion

(% a

rea)

2 - 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

Lactate Acetate

Butyrate

Sulphate

H2S

Sulphate-reducingbacteria

Clostridium cluster XIVa

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 epithelialdamage)– Manno-oligosaccharides– Fructo-oligosaccharides – …

Thanks for your attention !