Practical 1. Major diseases occuring during broiler rearing

Question 1

Enteric disease complex. Affected age groups; economical losses

Answer 1

• young chickens affected, mainly < 3 weeks
• poor food conversion, decreased weight gain, complications (secondary infections) - death

Question 2

Enteric disease complex. Clinical symptoms

Answer 2

• huddling, litter ingestion
• diarrhoea —> consequences (deficiencies, wet litter -> pododermatitis, NH3 - respiratory problems)
• poor production, fail to grow

Question 3

Cause of enteric disease complex in chicken

Answer 3

• not completely cleared
• multifactorial
• VIRUSES! (Astroviridae, Coronaviridae, Reoviridae, Rotaviridae, PARVOVIRIDAE, etc)

Question 4

Pathogenesis of enteric diseases

Answer 4

• dilated thin-walled intestines (viruses)
• villus degeneration (villus denudation, villus atrophy/fusion) -> reduced functional surface =>
  maldigestion-malabsorption-malsecretion

Question 5

Several names of enteric disease complex in chicken

Answer 5

Several names indicate characteristic symptoms or lesions due to unclear etiology

• Runting-Stunting Syndrome (RSS)
• Malabsorption syndrome (MAS)
• Infectious stunting syndrome (ISS)
• Pale bird syndrome (refers to pale legs due to impaired carotene absorption)
• Helicopter disease (refers to abnormalities of feathering)
• Brittle bone disease (refers to disorders of bone formation due to impaired calcium absorption)

Question 6

General Pathogenesis of viral enteritides

Answer 6

• blunting of the villi (villus atrophy) due to epithelial loss (villus denudation)
• viraemia may also develop following the multiplication of viruses in the intestines

Extraintestinal lesions:
- abnormalities of feathering
- disorders of bone formation (ricketts, osteoporosis, tibial dyschondroplasia (TD), epiphyseolisis)
- vitamin E deficiency
- atrophy of the immune organs (immunosuppressive, secondary infections)

Question 7

Ratio of crypt : villus in normal intestinal mucosa?

Answer 7

1:7

Crypts (of Lieberkuhn) are moat-like invaginations of the epithelium around the villi, and are lined largely with younger epithelial cells which are involved primarily in secretion.

Question 8

Answer 8

Villus denudation and villus atrophy

Question 9

Answer 9

Multifocal inflammatory cell infiltration in the liver (portal circulation!)

Histopathological observation of liver sections from broiler chickens (Bar =50 µm). Green arrows show inflammatory cell infiltration and yellow arrows show intrahepatic hemorrhages. A, control group; B, AFB1 group; C, cur + AFB1 group; D, curcumin group.

Question 10

Pododdermatitis <-> enteric disease ?

Answer 10

Diarrhoea -> wet litter -> pododermatitis -> ventral recumbency (sternal bursitis, dehydration, starvation)

Question 11

Effect on kidneys during enteric disease complex in chicken

Answer 11

Dehydration -> renal degeneration
(Enlarged, pale kidneys or tubular pattern)

Question 12

Epiphyseolysis in case of enteric disease complex in chicken

Answer 12

If epiphysis detaches -> exsanguition

Question 13

Necrotic enteritis (NE)

Answer 13

• Clostridium perfringens type A or C
• anaerobic, gram-positive
• spore-forming, toxin-producing
• commonly found in soil and water and the intestines and faeces of normal birds

Not contagious - role of predisposing factors ! - diet, damage to the intestinal mucosa (e.g. coccidiosis, ingestion of rough, fibrous litter)

• mainly at 2-5 weeks of age
• sporadic, acute, fibrinonecrotic enteritis, pseudo membrane
• high mortality

Question 14

Answer 14

Necrotic enteritis in chicken

Question 15

Coccidiosis of chicken

Answer 15

Eimeria spp
- obligated intracellular protozoa
- host-specific
- mainly at 3-6 weeks of age
- most pathogenic species: E.necatrix - small intestines, E.tenella - caeca, E.brunetti - large intestines

Question 16

Respiratory diseases of chicken

Answer 16

• avian metapneumovirus (aMPV or avian rhinotracheitis (ART), paramyxoviridae)
• avian influenza (AI) (bird flu)
• Newcastle disease (ND)
• infectious bronchitis (IB)
• mycoplasmosis
• colibacillosis
• ornithobacteriosis

Question 17

Avian metapneumovirus (aMPV, or avian rhinotracheitis, ART; paramyxoviridae)

Answer 17

Pathogenesis:
- infection via inhalation (mainly 3-12 weeks of age)
- if secondary bacterial infection occurs -> swollen head syndrome (SHS) - due to sinusitis and cellulitis

Clinical symptoms:
- sneezing, nasal discharge, head shaking

Pathology:
- rhinotracheitis
- airsacculitis
- peritonitis (secondary E.coli infection)

Question 18

Answer 18

Catarrhal rhinitis

Question 19

Answer 19

Fibrinous airsacculitis

Question 20

Answer 20

Serofibrinous serositis

Question 21

Avian influenza (AI) - bird flu

Answer 21

• notifiable disease
• higher mortality
• haemorrhages

Question 22

Newcastle disease (ND)

Answer 22

• notifiable disease
• higher mortality
• central nervous system symptoms!
• Newcastle disease virus (=paramyxovirus type 1)

Question 23

Infectious bronchitis (IB)

Answer 23

• coronavidae

Pathogenesis:
Infection mainly via inhalation -> replication (Harderian gland - tracheal epithel - kidney and oviduct epithel)

Clinical symptoms, pathology:
- high morbidity-mortality
- different pathotypes (respiratory, nephropathogenic, enterotropic)
- respiratory symptoms
- nephritis - urate deposits (visceral gout)
- proventriculitis

In layer flocks can result in egg-laying disorders and “false-layers”

Question 24

Mycoplasmosis in birds. Causing agents, clinical symptoms

Answer 24

Mycoplasma gallisepticum, Mycoplasma synoviae

• small bacteria, without cell wall
• predisposing factors!

Clinical symptoms:
- M.gallisepticum: respiratory symptoms
- M.synoviae: (respiratory symptoms) + enlarged joints

In layer flocks they can cause decreased egg production and decreased hatchability

Question 25

Mycoplasmosis in birds. Pathology

Answer 25

- respiratory lesions (sinusitis, airsacculitis, CRD (chronic respiratory disease) with *E.coli* secondary infection) - arthritis, tenosynovitis, bursitis - serositis - inflammation of the oviduct (juvenile) - septicaemia

Question 26

Answer 26

Sinusitis (inflammation of the paranasal sinuses) due to mycoplasmosis

Question 27

Answer 27

Arthritis (enlarged joints due to accumulation of exudate) due to mycoplasmosis

Question 28

Answer 28

Sternal bursa - serofibrinous bursitis due to mycoplasmosis

Question 29

Colibacillosis

Answer 29

**Avian pathogenic *Escherichia coli* (APEC)** Forms: - omphalitis (inflammation of the navel) - septicaemia - swollen head syndrome (with aMPV) - chronic respiratory disease (CRD) - clinical symptoms depending on predisposing factor -> conjunctivitis, tranche it is, airsacculitis (scrambled egg-like fibrinous content)

Question 30

Answer 30

Fibrinous serositis in colibacillosis

Question 31

Ornithobacteriosis (ORT)

Answer 31

***Ornithobacterium rhinotracheale*** Pathogenesis: - facultative pathogen bacterium - mainly 3-4 weeks of age chickens Predisposing factors: - chicken anaemia virus (CAV) - Gumboro disease or Infectious bursal disease virus (IBDV) - infectious bronchitis virus (IBV) - feed containing mycotoxin - unsuitable environment Clinical symptoms (uncharacteristic): - depression, decreased feed and water intake - respiratory symptoms (nasal discharge, difficult breathing)

Question 32

Answer 32

Catarrhal rhinitis (mucous yay content in the airways) in ornithobacteriosis

Question 33

Answer 33

Serous airsacculitis (foamy content in the airsacs) in ornithobacteriosis

Question 34

Some major non-infectious diseases

Answer 34

- tibial dyschondroplasia (TD) - sternal bursitis (breast blisters) - deep pectoral myopathy (Oregon disease, green muscle disease) - ascites syndrome or pulmonary hypertension syndrome (PHS)

Question 35

Tibial dyschondroplasia (TD). Clinical signs

Answer 35

- a cone of abnormal cartilage forms in the metaphysics - reduced load capacity (painful, bowing of the tibiotarsus in severe cases)

Question 36

Tibial dyschondroplasia (TD). Causes

Answer 36

Multifactoral: - **genetic** selection (rapid growth is the major cause of tibial dyschondroplasia) - inadequate **calcium/phosphorus** ratio in the diet - metabolic acidosis - mycotoxicosis

Question 37

Sternal bursitis (breast blisters)

Answer 37

- it is associated with repeated injuries to the breast bone area - (can be caused by *Mycoplasma synoviae* infection)

Question 38

Deep pectoral myopathy (Oregon disease, green muscle disease)

Answer 38

- **necrosis of the supracoracoid muscle due to ischaemia** - in meat type chicken (and turkey) - uni or bi-lateral - **initially pale and swollen from deems, later green and dry** - predisposing factors: increased wing flapping and inadequate muscle vasculature (but not the body weight!) - condemnation of affected muscles

Question 39

Ascites syndrome or Pulmonary hypertension syndrome (PHS)

Answer 39

- **exsessive accumulation of transudate fluid within the peritoneal spaces, cardiac enlargement, dilated right ventricle, right-sided heart failure** - mainly at 5-6 weeks of age - **caused by pulmonary hypertension due to rapid growth** (higher oxygen demand)

Question 40

Swollen head syndrome

Answer 40

aMPV (avian metapneumovirus) + secondary bacterial infection (e.g. *E.coli*)