Poultry exam

Health problems occurring in intensive egg-productive poultry farming

Intensive farming

* High number of birds, confined housing, no outdoor access

* High meat/egg production

* Leads to: metabolic diseases, overcrowding, stress, rapid disease spread

Birds examined/treated on *flock basis**, not individually

Behavioral disorders

* Feather plucking: stress, overcrowding, boredom, low protein diet

* Cannibalism: overcrowding, stress

Reproductive disorders

* Egg drop syndrome (Adenovirus): pale, soft-shelled or shell-less eggs in otherwise healthy hens

Egg peritonitis: defective oviduct → yolk deposited in abdomen → risk of E. coli* infection

Skeletal diseases

* Rickets (young birds): Vit D₃/Ca/P deficiency → weak, soft bones

* Osteomalacia (adult birds): same cause as rickets

* Caged layer fatigue: Ca deficiency + lack of exercise → soft bones after peak lay

Metabolic diseases

* Fatty Liver Haemorrhagic Syndrome: excess energy intake, low exercise → fatty liver + hemorrhage

* Prevention: increase protein, add antioxidants

Infectious diseases

* Fowl cholera

* Newcastle disease (NCD)

* Coccidiosis

* Avian influenza

* Salmonellosis

* Fowl pox

Environmental / management issues

* Ammonia intoxication (poor ventilation, deep litter)

* Pododermatitis

* Circulatory failure (broilers)

* Sudden death syndrome

Health problems occurring in intensive fattening flocks.

* Short lifespan: ~42 days, ~2.5 kg

* Fewer disease types compared to hatchlings

Growth-related problems

* Rapid weight gain → locomotor disorders:

* Rickets

* Dyschondroplasia

* Degenerative joint disease (viral arthritis)

* Tibial rotation

Circulatory issues

* Heart relatively too small, insufficient capillary development

* Common: sudden death syndrome, ascites syndrome

Feet lesions

* Bumblefoot: pressure → ischemia → infection → pododermatitis

Metabolic disorders

* Frequent due to intensive growth

Environment-related risks

* High stocking density → poor ventilation → ↑ inhaled pathogens, rapid disease spread

* Overcrowding → stress → cannibalism, suffocation

Housing problems

* Deep litter → ammonia buildup → intoxication, fungal infections

Management (when problems occur)

Reduce growth rate: Lower-quality feed and fewer light hours per day

3. Health problems occurring in extensive poultry farming.

• Low bird numbers, low meat/egg production, low work productivity

• Free-range → birds find own food

• Minimal supervision (vet ~1×/year)

• Higher disease risk (↓ biosecurity, ↑ contact with environment & wildlife)

• Both contagious + metabolic diseases

General health issues

• Bumblefoot: pressure → ischemia → infection → pododermatitis

• Nutritional deficiencies: ↓ growth, ↓ egg production, possible death (vit/min)

• Intoxications:

  • Excess nutrients (e.g. salt + limited water)

  • Toxins (Clostridium in soil, aflatoxins in feed)

Parasitic diseases

• ↑ due to intermediate hosts exposure

• Endoparasites: Ascaridia, Heterakis gallinarum, Syngamus trachea, Eimeria spp.

• Ectoparasites: lice, mites (Dermanyssus gallinae), ticks, air sac mite

Examples

• Capillariasis (Capillaria spp., IH: earthworm): weight loss, dysphagia

• Cropworm (Gongylonema ingluvicola, IH: insects): regurgitation, emaciation

• Tx: flubendazole, levamisole; Prevention: biosecurity, limit IH

Viral diseases

• Marek’s disease: from vaccinated poultry. paralysis, high mortality

• Newcastle disease (Paramyxovirus): respiratory, sudden death, airborne

• Avian influenza: zoonotic risk

Bacterial diseases

• Chlamydia psittaci: systemic (resp + GIT), often asymptomatic

• Mycoplasma synoviae, M. gallisepticum: chronic respiratory disease

• Salmonella pullorum/gallinarum

Fungal diseases

• Aspergillus: lungs, air sacs

• Microsporum, Trichophyton

Other risks

• Wildlife predation

• Increased exposure to environmental pathogens

4. Specific immunoprophylaxis and serodiagnostics.

Immunoprophylaxis = Prevention of disease by inducing active or passive immunity

(vaccination, maternal antibodies, recovery from disease)

Purpose: Prevention and control of infectious diseases

Basic principles:

Vaccinate only healthy birds!

• Live vaccines → mainly for housed/intensive systems

• Killed vaccines → often for outdoor/extensive birds

• Vaccinate breeders → maternal antibody transfer to chicks

• Drinking water vaccines → no chlorine

Administration methods

• Wing web: puncture with a double-prong needle (fowl pox, avian encephalomyelitis, fowl cholera)

• Aerosol (spray): for respiratory vaccines (Newcastle, infectious bronchitis), applied in hatchery or at arrival → attaches to eye/resp mucosa

• Drinking water: for large flocks (water deprivation before use)

• Subcutaneous injection

• Intramuscular (IM): pectoral muscle

• Eye drop: via nasolacrimal duct → swallowed (accurate individual dose, e.g. coccidiosis)

• Intranasal

Broilers	Layers	Breeders
1 day – NCD, IB, IBD (aer)	1day - Mareks SC., IB	1 day - Marek’s i.m., IB
	10+days & 4w NCD/ IB	10d&4weeks – NCD/IB
	7weeks – NCD/IB	7weeks – NCD/IB
	15weeks – Avian pox (wingweb)	15weeks – Avian Pox
	18 weeks – NCD, IB, Egg Drop	18 weeks- NCD, IB, ED

Age	Broilers (short life)	Layers (egg production)	Breeders (parent stock)
1 day	Marek’s (SC) ± NCD, IB (spray)	Marek’s (SC)	Marek’s (SC)
2–3 weeks	NCD, IB	NCD, IB	NCD, IB
3–5 weeks	IBD	IBD	IBD
7–10 weeks	— (often slaughtered early)	NCD, IB (booster)	NCD, IB (booster)
10–12 weeks	—	Avian encephalomyelitis	Avian encephalomyelitis
12–14 weeks	—	NCD, IB	NCD, IB
15 weeks	—	Fowl pox	Fowl pox
16–18 weeks	—	NCD, IB ± Egg drop	NCD, IB ± Egg drop
Extra	Minimal program (short lifespan)	Focus on egg production protection	More vaccines (e.g. Mycoplasma, ILT, Salmonella)

Layers are vaccinated against Marek’s at day 1, followed by Newcastle disease and infectious bronchitis at 2–3 weeks with multiple boosters, IBD around 3–5 weeks, fowl pox at 15 weeks, and a final booster including egg drop before laying.

Other vaccines

• Avian encephalomyelitis: vaccinate breeders (~11 weeks). Essential in breeders to protect their offspring, optional in layers (?)

Hygiene & prevention

• All-in-all-out → same age birds, ↓ disease spread & cannibalism

• Cleaning/disinfection between flocks

• Biosecurity (B&W zones)

• Egg sanitation (dipping)

• Probiotics

Serodiagnostics = Diagnosis using serological reactions (antibody detection in serum/body fluids)

Purpose: Monitor antibody titers

• Check vaccine success

• Determine revaccination timing

• Investigate disease outbreaks

Methods: PCR, ELISA, IFA, HIT, AGID

Key point: Low antibody titers → risk of disease / vaccination failure

Drug administration:

• Parenterally (i.v. (no practical use), i.m. (pectorals, thigh muscle), s.c. (flank)

• Medication with water / food for big flocks, mostly used for vaccination. Water deprivation before giving medicated water

• Serology after 2-3 weeks to look for titers (vaccination give elevated titers)

5. Diseases caused by incorrect nutrition, avitaminoses, malabsorption syndrome

Primary – Exogenous. Lack in feed.
Secondary – Endogenous. High demand or disorders in absorption/utilisation. (Enteritis).

Vitamin deficiencies are most commonly caused by a lack of a complete vitamin premix from the birds’ diet (exogenous). Though in some cases, endogenous deficiency may be seen, caused by increased demands, stress, infections, Git disorders, etc. Multiple signs of deficiency can be seen, although in general, signs of B vitamin deficiencies appear first as there are some stores of fat-soluble vitamins in the body

Deficiency → Key Sign → Cause

Minerals / Nutrition

• Ca / P / Vit D₃ → Rickets (young), osteomalacia (adult), soft bones, thin shells → ↓ Ca absorption/imbalance

• Mn / Choline / Zn → Perosis (slipped tendon), decreased growth of long bones, widening of tibiometatarsal joint, twisting of tibia, and slipped m. gastrocnemius tendon! → defective bone/tendon development

• High energy : low protein → Fatty liver + hemorrhage (FLHS) → excess energy, low exercise

• Ca + no exercise → Cage layer fatigue, fractures → depletion during egg production

Fat-soluble vitamins

• Vit A → Blindness, dry cornea, poor growth → epithelial damage. Treat with vit A in water.

• Vit D₃ → Rickets/osteomalacia, “penguin stance” → ↓ Ca/P metabolism. Treat with single massive D3 dose (15000IU)

• Vit E (+Se) → Ataxia, “crazy chick syndrome”, muscular dystrophy → oxidative damage. Treatment: Se + Vit E in diet. CS: falling over, green wings. 3 outcomes: Encephalomalacia (crazy chick syndrome), Exudative diathesis, muscular dystrophy

• Vit K → Hemorrhage, anemia → ↓ clotting (↓ prothrombin). Vit K in feed.

Water-soluble vitamins

• B1 → Stargazing → CNS dysfunction

• B2 (riboflavin) → Curled toe paralysis → nerve damage. Gross pathology = Marked enlargement of the sciatic and brachial nerve sheaths; sciatic nerves usually show the most pronounced effects.

• B3 → Perosis → overlaps with Mn deficiency

• B7 (biotin) → Dermatitis, fatty liver → skin + metabolism

• B12 → Anemia → ↓ RBC production

• Vit C → Weakness, weight loss → connective tissue disorder, Scurvy

Malabsorption syndrome

→ Diarrhea, poor growth, undigested feed (caused by reovirus + intestinal damage)

• Disease Complex (avian reovirus + other virus & bacteria) commonly found in broilers.

• May affect GIT, nutritional deficiency & lesions, by apoptosis and heterophil infiltration of jejunum, causing malabsorption. Diarrhea, malpositioned beak, decreased growth, rickets, foamy undigested particles in droppings.

• No treatment! May vaccinate. Good hygiene.

Exam trick

Bone problems → think Ca/P/Vit D₃ or Perosis

Neuro signs → think Vit E or B vitamins

Skin/epithelium → think Vit A / Biotin

Bleeding → think Vit K

6. Feather disorders - etiology, symptoms, diagnostics, dif. dg,  therapy and prevention.

Poultry – Feather Disorders & Skin Diseases (Ultra High-Yield Flashcard)

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# 6. Feather disorders

## Ectoparasites (major cause of feather damage + anemia)

Bed bug (Cimex lectularius)

* Signs: anemia, poor condition, feather loss, ↓ production (severe cases)

* Treatment: pyrethroid fumigation

Biting lice (Mallophaga)

* Signs: irritation, scabs, crusty egg clusters at feather base, anemia

* Treatment: pyrethroid spray

Red mite (Dermanyssus gallinae)

* Signs: nocturnal feeding, anemia, pruritus, restlessness, ↓ production

* Also vector (e.g. bacterial diseases like fowl cholera)

* Treatment: pyrethroids, carbamates, organophosphates

Ticks (Ixodes, Dermacentor)

* Signs: anemia, emaciation, skin lesions; may transmit systemic disease (fever, paralysis)

* Treatment: acaricides (same groups as above)

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## Non-parasitic feather disorders

Feather plucking

* Etiology: stress, overcrowding, high temperature, boredom, low protein, high density

* Signs: feather loss, skin damage

* Treatment: environmental enrichment, dim light, increase protein, sedation (if needed), beak trimming (prevention measure in severe systems)

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## Viral feather disease

Reticuloendotheliosis virus (retrovirus)

* Signs: abnormal feathers, anemia, enlarged nerves, thymic atrophy

* Diagnosis: PCR

* Differential diagnosis: Marek’s disease (nerve tumors, similar neuropathy)

* Treatment: none

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## Vitamin-related

* Niacin (B3) deficiency → feather loss, perosis signs

* Treatment: B-complex supplementation

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# 7. Skin diseases

## Bacterial

Gangrenous dermatitis / malignant oedema

* Agent: Clostridium perfringens, C. septicum

* Signs: moist necrosis, black/red skin, gas in subcutis, feather loss, cellulitis

* Treatment: antibiotics (penicillin)

* Prevention: avoid wounds, hygiene

Bumblefoot (pododermatitis)

* Agent: Staphylococcus aureus (± others)

* Signs: plantar abscess, lameness

* Treatment: remove scab, clean, antibiotics

* Prevention: proper litter, perch design

Erysipelas

* Agent: Erysipelothrix rhusiopathiae

* Signs: skin lesions, depression, endocarditis, pericarditis

* Diagnosis: culture (blood agar), PCR

* Treatment: antibiotics

* Prevention: vaccination

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## Viral

Avian pox (Avipoxvirus)

* Signs:

* Dry form: skin nodules (head, legs, vent)

* Wet form: plaques in mucosa/sinuses

* Differential: Trichomonas, Marek’s

* Treatment: none (self-limiting)

* Prevention: vaccination + vector control

Marek’s disease (Herpesvirus)

* Signs: skin nodules, nerve enlargement, tumors, eye lesions

* Treatment: none

* Prevention: vaccination

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## Fungal

Favus (Microsporum gallinae)

* Signs: crusts/scales on head → may spread systemically in severe cases

* Treatment: antifungals + hygiene

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## Parasitic skin lesions

* Ectoparasites (lice, mites, ticks) → main cause of pruritus + feather damage

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## Other important

Pododermatitis (“hock burn”)

* Cause: prolonged contact with wet/dirty litter (contact dermatitis)

* Progression: erythema → erosions → fibrosis → lameness

* Treatment: none specific

* Prevention: dry litter, management improvement

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# Exam shortcut

* Feather loss + itching → parasites or stress

* Neurological + feather changes → Marek / REV

* Skin necrosis + gas → Clostridium

* Nodules → pox or Marek

* Plantar lesions → bumblefoot / litter problem