Top 10 Poultry, part 1: Newcastle, Marek's, Avian Influenza, ILT, Infectious bronchitis

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Newcastle disease (avian pneumoencephalitis)

Torticollis, a sign of Newcastle disease

Petechiae in proventriculus and gizzard; inflammation of duodenum (outside & inside view), Newcastle disease
- Classic case: high mortality rate
  - Acute onset severe respiratory and/or neurologic and/or GI signs:
    - Respiratory:
    - Neurologic:
    - GI: Watery green diarrhea
  - Sometimes sudden death
  - Decreased egg production with thin shells and watery albumen
- Dx:
  - Etiology: RNA avian paramyxovirus-1 (APV1 or PMV-1)
  - Gold standard test: virus isolation
    - Dead birds: lung, kidney, GI tract
    - Live birds: nasopharyngeal and tracheal exudate swabs
  - RT-PCR for pathotyping and genotyping
  - Intracerebral pathogenicity index (ICPI): inoculating day-old chicks to determine virulence
  - Hemagglutination positive
  - Almost pathognomonic necropsy lesions: multifocal necrosis, hemorrhagic intestinal mucosa (especially at lymphoid foci - cecal tonsils)
- Rx: None, CULL all birds on premises
  - Prevention:
    - Good management practices, spreads quickly through facility via aerosol exposure
    - Indoor operations better, outdoor flocks at higher risk
    - Vaccines in countries where virulent virus disease outbreaks occur
- Pearls:
  - APV1 are labeled depending on how fast they kill chick embryos post-innoculation
    - Lentogenic (slow), used in vaccines and not reportable
    - Mesogenic (medium)
    - Velogenic (fast); further divided into:
  - Clinical signs vary with strain
  - Strains vary by differences in surface glycoproteins: hemagglutinin-neurominidase (HN) and fusion (F)
  - Mesogenic and velogenic Newcastle disease are REPORTABLE in USA
  - ZOONOTIC: transitory conjunctivitis in humans

Marek's disease

Normal eye on left, grey eye (from lymphocytic infliltration of iris) on right, Marek's disease

Enlarged sciatic nerve on left, Marek's disease
- Classic case: Clinical signs based on which organ/tissue T-lymphocytes infiltrate
  - Sciatic nerve paralysis (one leg forward, one backward)
  - "Grey eye" (due to lymphocytic infiltration of iris)
  - Young chicken (2-5 mos)
  - Decreased growth rate and egg production
  - Enlarged feather follicles (cause for condemnation)
- Dx:
  - Etiology: Oncogenic lymphotrophic alphaherpesvirus (genus Mardivirus)
  - Virus isolation, PCR (for viral DNA in lymphoid tumors), AGID
  - Enlarged peripheral nerves (esp. sciatic) at necropsy
  - Lymphoid tumors in liver, spleen, gonads, heart, lung, kidney, muscle and proventriculus
  - Bursa is rarely affected and usually atrophic (distinguishes from lymphoid leukosis)
  - Histopathology and immunohistochemistry
- Rx: None
  - Supportive care in pet poultry
  - Prophylaxis: vaccinate in ovo or day-old chicks decreases shedding
- Pearls:
  - Virus causes in lymphoproliferative disease/neoplasia in chickens
  - No vertical transmission; horizontal transmission is mainly via inhalation of aerosolized "chicken dander" & can travel on the wind between flocks
  - Virus practically ubiquitous; assume flocks infected
  - Silent recovered lifelong carriers are main reservoir

Avian influenza (AI)

Hemorrhaging of the limbs with HPAI
- Classic case: Depends on pathogenicity/strain
  - Low-pathogenicity AI (LPAI): often subclinical
    - Mild to moderate respiratory signs
    - Poor weight gain
    - Egg drop
  - High-pathogenicity AI (HPAI): "Fowl plague"
    - Peracute death, prostration
    - Cyanosis of head appendages, petechiation in viscera, oral/nasal bloody discharge
    - Diarrhea
    - Neurologic signs
    - Hemorrhages of the limbs
    - Spreads rapidly!
- Dx:
  - Etiology: Orthomyxovirus, influenza type A
  - Virus isolation in eggs from clinical samples with rRT-PCR for typing
  - Hemagglutination positive
  - Haemagglutinin and Neuraminidase (H and N) typing and subtyping also done by inhibition tests using antisera (H5 & H7 HPAI subtypes are most commonly implicated)
- Rx:
  - Prevention: autogenous vaccination (requires state veterinarian approval) and strict biosecurity
  - HPAI: no treatment, depopulate
  - Supportive care and antibiotics for LPAI
- Pearls:
  - Highly contagious
  - HPAI is REPORTABLE, possibly ZOONOTIC (H5N1, H7N7 can be fatal to humans)
  - Often carried long distances by subclinically infected waterfowl or seabirds
  - Gene re-assortment occurs in developing countries or markets where humans, fowl, and swine intermix, creating new genotypes

Infectious laryngotracheitis

Dyspneic chicken, infectious laryngotracheitis
- Classic case:
  - Acute outbreak of gasping, coughing, conjunctivitis, dyspnea, depression
  - +/- Bloodstained beaks in chickens under 4 weeks
  - Decreased egg production
  - Mortality variable, often high
  - Chronic: poor weight gain in broilers
  - Latent infection in survivors, can recrudesce when birds stressed
- Dx:
  - Etiology: Gallid herpesvirus I
  - Necropsy: blood, mucus, caseous exudate, or hollow cast in trachea
  - Intranuclear inclusion bodies
  - Clinical cases: virus isolation, PCR
  - Screen flocks with ELISA or virus neutralization (VN) serological tests
- Rx:
  - No treatment
  - Immediately vaccinate adults during outbreak
  - Prevent with biosecurity and vaccination
- Pearls:
  - Highly contagious
  - Worldwide; transmission horizontal through aerosol, fomites
  - Vaccination with attenuated vaccines has regularly resulted in disease through serial virus passage in vaccinates
  - Recovered birds are lifelong carriers
  - REPORTABLE

Infectious bronchitis

Upper respiratory signs with infectious bronchitis

Wrinkled egg, infectious bronchitis
- Classic case:
  - YOUNGEST birds: acute onset upper (sneezing, conjunctivitis, swelling) and lower (rales, coughing, dyspnea) respiratory signs
  - Breeders & layers: SHARP decrease in egg production and misshapen or wrinkled egg shells
  - Variable mortality, but almost 100% morbidity
- Dx:
  - Etiology: RNA coronavirus
  - Necropsy: white urates in renal tubules
  - NEGATIVE hemagglutination reaction
  - Virus isolation in chick embryo
  - Paired serology
- Rx: None, supportive care
  - Antibiotics for secondary infections
  - Prophylaxis:
    - Vaccines
    - Strict biosecurity
- Pearls:
  - Worldwide, common, contagious
  - Reportable in some states
  - Some strains cause reproductive issues, some are nephrotrophic

Images courtesy of The Poultry Site (torticollis/Newcastle, laryngotracheitis), USDA (grey eye/Marek's, avian influenza), Raketenpilot (walking chickens), Lucyin (Marek's sciatic nerves, Newcastle hemorrhages), Copyleft (wrinkled egg), Dr. Marina Brash (infectious bronchitis), Benjamint444 (silkie), and Dimus (turkey).

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