Poultry Viral Diseases

Avian primary immune organs

T lymphocytes, B lymphocytes

Avian secondary immune organs

cecal tonsils, Peyer patches, harderian gland, spleen, lymphoid follicles

Chicken Infectious Anemia (CIA) / Chicken Anemia Virus (CAV) / Blue Wing Disease

characterized by aplastic anemia, lymphoid atrophy, hemorrhages, immunosuppression

• ubiquitous

Infectious Bursal Disease (IBD)

viral disease of chickens

IBD is characterized by?

inflammation and subsequent atrophy of the bursa of Fabricius plus immunosuppression

IBD happens to chickens how old?

3-6 weeks old

How to control IBD?

vaccination in breeders

Avian Viral Tumors (MDV and ALV)

Marek’s Disease Virus (MDV)

tumoral disease of chickens, turkeys, quails

• ubiquitous

MDV (Marek’s Disease Virus) happens in chickens how old?

2-7 months old (beyond 3 weeks)

What disease is the most diagnosed in backyard flocks?

ALV (avian viral tumors)

Etiology of ALV/MDV

• DNA

• Alpha-herpesvirus

• cell-associated

• three serotypes [1 (mild v, vv, vv+), 2 (non-oncogenic), 3 (HVT)]

• cross reactivity

• enveloped

ALV/MDV transmission

Feather dander most important, sporadic shedding through lifetime, latency, very contagious

ALV/MDV signs

depression, poor body condition, asymmetric partial paralysis/dilation of crop, blindness

ALV/MDV lesions

nerve enlargement, discoloration of iris, enlargement of feather follicles, lymphomas in nerves and viscera

ALV/MDV diagnosis

History, age, location of tumors

In older chickens (late Marek’s vv+)

nerve involvement

virology and symptoms not very useful

qRT-PCR

ALV/MDV is most common in

immature chickens (2 to 5 mo)

ALV/MDV control

Vaccination (in ovo or 1 day old)

immunity not fully developed for 7-10 days, minimize exposure until then

ALV/MDV vaccines

HVT, HVT + serotype 2, attenuated serotype 1

cell associated vaccine manipulate properly

buy vaccinated chickens from NPIP hatcheries

Infectious Bronchitis (IB)

acute and highly contagious respiratory disease of chickens

IB targets the

upper respiratory and urogenital tracts

IB symptoms

tracheal rales, sneezing, nasal discharge, coughing, drop in egg prod and quality

IB transmission

highly contagious, short incubation period (24-48 hrs)

horizontal transmission most important (aerosols)

IB economic losses rep by

reduced feed conversion

reduced weight gain

increased mortality in young chickens

increased condemnations at processing plants

reduced egg prod and egg quality

IB Prevention

Vaccination w/variable effects

• bc variability of virus, different types

cleaning and disinfection

• very sensitive virus

Influenza Virus Type A

Birds-mammals

Influenza Virus Type B

humans-seals

Influenza Virus Type C

humans-pigs

Avian influenza

Orthomyxoviridae, influenzavirus A

Influenza genetic material

(-)ssRNA, 8 segments

Influenza variability

susceptible to mutations and recombination

Influenza Antigenic drift

point mutations due to selective pressure

Influenza antigenic shift

reassortment of gene segments

• ducks and swine play important role

Most important proteins in influenza are

Hemagglutinin (HA) and Neuraminidase (NA)

Influenza receptors

determine host and tissue tropism

• a2,3 = sialic acid binding (avian type)

  • a2,6 = sialic acid binding (human type)

HPAI

severe clinal signs

• death without signs

• nervous signs

• cessation of egg prod in 6 days

• necrosis, edema, hemorrhages in comb/wattles

• pneumonia

• cutaneous hemorrhages in skin of shanks

high mortality in birds

LPAI

little or no clinical signs in birds (H5-H7)

• mild to severe respiratory signs (sneezing, coughing, rales, lachrymation)

• decreased egg prod

• decreased water/feed consumption

• diarrhea

High vs Low pathogenic determined by

lab, look at chicks intravenous pathogenicity index (IVPI > 1.2 in chicks)

molecular sequencing

Avian Influenza since Oct. 2020

increase and spread globally

• includes Latin America and Antarctic region

Increase in # of outbreaks and losses in poultry

• peak in Oct 2021-Sept 2022

Increased impact in wildlife

Increased # of cases in domestic & wild mammals

2024 Avian Influenza

Oct = new start seasonal wave of AI cases

almost all HPAI outbreaks associated w/H5N1 Gs/Gd lineage clade 2.3.4.4

virus became endemic in dabbing ducks

• reservoirs for different AI’s, behave as mixing vessel w/potential to adapt virus to new hosts

Historically avian influenza became HPAI by

went from ducks to chickens to turkeys (became HP) then back to ducks, ducks spread HPAI

HPAI outbreak 2022-2025

Wild bird clinical cases (lots resident non migratory birds)

• waterfowl

• raptors

• pelicans

• cranes

• terns

Europe, North/South/Central America, Africa, Asia

• US first detected East coast in Atlantic flyaway, moved to West through raptors/waterfowl/crows

HPAI EPI Data

• EPI curve shows longer outbreak w/higher proportion of backyard birds affected and wider bird distribution

• higher proportion of backyard to commercial flocks

Most common wild bird species infected

Pelicans → Vultures → Hawks → Geese

Avian influenza incubation

highly variable, between 3-21 days

HPAI control

vaccination in endemic countries

eradication and surveillance in free countries

biosecurity

best treatment is prevention

Newcastle disease

respiratory, digestive, nervous signs disease caused by Orthoavulavirus type 1, Paramyoxovirus

Newcastle disease is difficult to recognize due to

different pathotypes depending on different viral isolates

Newcastle Pathotypes

Velogenic NDV: acute respiratory/neurologic signs w/high mortality

Mesogenic NDV: milder mortality just in young chicks (some vaccines)

Lentogenic NDV: mild or inapparent respiratory infections (live vaccines B1, La Sota, Clone 30)

End Reservoir for Newcastle disease

waterfowl

• mostly for lentogenic strains

• most velogenic strains reside in chicken populations so resident poultry risk for endemicity of NDV

Newcastle Control

vaccination (LaSota or B1) when close contact to waterfowl

vaccinating with mild strains to protect against exotic strains

different strategies depending on the challenge

Fowl Pox (POX)

slow spreading virus in chickens, turkeys, other birds

• prod cutaneous lesions in areas devoid of feathers and/or respiratory and digestive mucosa

Fowl Pox is in all birds except

recently hatched

POX etiology

DNA Avipoxvirus, family poxviridae

POX transmission

mosquitoes

close contact, aerosols

POX signs

cutaneous, diphteritic, low mortality

POX diagnosis

signs and lesions

POX control

vaccination (from 4-10 weeks old), recombinants

• check for take 7-10d after

control mosquitoes and cannibalism

POX treatment

get rid of scab, clean area w/disinfectant

vaccination

Infectious Laryngotracheitis (ILT)

respiratory tract infection characterized by gasping and expectoration of bloody mucus

ILT causes economic loss by

reduced egg prod and mortality

ILT signs

excessive lacrimation (crying)

swelling of eyes

almond shape eyes

coughing and bloody expectoration

ILT lesions

mucoid to hemorrhagic tracheitis and hemorrhagic exudates in trachea

caseous exudate in larynx

ILT diagnosis

Histopathology

isolation/identification of herpesvirus

Sx ELISA and VN

IFA

CAHFS Lab system

Davis - Avian, livestock, horse

Turlock - Avian

Tulare - Avian, livestock, horse

San Bernardino - Avian, livestock, horse