Lecture 17 and 18: Viral Diseases of Poultry

transmission of fowl pox

• affects chickens and turkeys

• slow spread

• requires direct contact with traumatized skin or oral mucosa

• arthropod vectors

clinical signs of fowl pox

• cutaneous (dry form) → papules, vesicles, pustules, crusts on unfeathered skin

• diphtheritic (wet form) → yellow raised lesions, mouth, pharynx, trachea, difficulty swallowing/breathing

diagnosis of fowl pox

• based on clinical signs/lesions

• intracytoplasmic inclusions (Bollinger bodies)

fowl pox vaccinations

• chickens → wing web

• turkeys → inner thigh

Newcastle disease

• important in chickens and turkeys

• zoonotic → causes mild flu-like symptoms and conjunctivitis in humans

• rapid horizontal transmission via aerosols. fecal-oral, and fomites

what are the primary sources of velogenic forms of Newcastle Disease Virus (NDV)?

smuggled pet birds and poultry from South America/Mexico

mesogenic and lentogenic forms of newcastle disease are referred to as

paramyxovirus-1 (PMV-1)

the virulent forms of newcastle disease are called

Viscerotrophic velogenic newcastle disease (VVND) and neurotrophic velogenic newcastle disease (NVND)

clinical signs of newcastle disease

• VVND strain → may see peracute death or respiratory signs, drop in egg production followed by high mortality

• NVND strain → respiratory signs, CNS/PNS signs, hemorrhages in digestive tract

• mesogenic strains → mild upper respiratory signs (sneezing) and occasional cough associated with airsacculitis, infection is often followed by bacterial infection

diagnosis of newcastle disease

• PCR

• serology performed on acute (sick birds) and convalescent (taken 2-3 weeks later) using ELISA

prevention of newcastle disease

• VVND/NVND are eradicated in the USA by testing, euthanasia, and disposal

• mesogenic infection is prevented using live strains as vaccines prior to egg production

• killed vaccines used as boosters after egg production has begun

avian influenza

• affects all bird species, but important in chickens and turkeys \

• migratory waterfowl and shore birds are considered the major natural reservoir and are asymptomatic

transmission of avian influenza

• horizontal transmission via aerosols and fecal material

• fomites are important means of spread

• potentially zoonotic

clinical signs of avian influenza

• in low path strains H5 and H7 → mild respiratory signs, drop in egg production, low mortality

• in high path strains H5 and H7 → diarrhea, edema of head and face, CNS problems, acute drop in egg production high mortality

• tracheitis, hemorrhage

what types of avian influenza are reportable?

H5 and H7

avian influenza H5N1 recent outbreak

• total birds affected = 158M

• newest development → detection in dairy cattle in March 2024 in Texas

• 70 related human cases

infectious bronchitis (IB) transmission

• affects chickens only

• rapid horizontal transmission via aerosols, but also fecal-oral and fomites

• intermittent shedding for months

clinical signs of infectious bronchitis

• up to 100% morbidity

• oculonasal discharge in chicks

• adults = snick, cough, tracheal rales

• serous or caseous exudate in trachea, nasal passages, and sinuses

• severe egg production drops with soft shell and misshapen eggs

what can occur if young birds have severe IB?

• leads to later problems

• impacted oviducts, ruptured ova, and cystic right oviducts

• if kidneys are affected, then renal failure when water consumption drops

• development of gout

what is the IB vaccine given in conjunction with?

PMV-1 vaccine

infectious laryngotracheitis (ILT, LT) transmission

• worldwide in chickens

• horizontal transmission via aerosols, fomites

• spread is slow within a flock

• latency with stress shedding

clinical signs of ILT

• morbidity is high, but mortality is strain dependent

• milder strains → conjunctivitis, oculonasal discharge, sinusitis, drop in egg production

• virulent strains → coughing with expectoration of bloody mucus, dyspnea, and head/neck extension

ILT prevention

• virus moves slowly, so can vaccinate in the face of an outbreak to prevent spread within flock

• TCO or CEO vaccines given by eye-drop method

• CEO can roll-over in flock and become virulent

neonatal enteritis transmission

• affects young chickens and turkeys

• horizontal transmission by fecal-oral

• infection is complex and can include multiple viruses and other organisms associated with dysbiosis

clinical signs of neonatal enteritis

• ill-thrift, shrill chirping, huddling, ruffled feathers, paleness, diarrhea, weight gain, decreased feed and water intake, poor feed conversion, un-even growth

• acute spike in mortality

• small intestines → mucosal hyperemia and watery, gaseous, intestinal contents, thin intestinal walls, litter material in gizzard

treatment of neonatal enteritis

• palliative → increase environmental temperature and ventilation rate

• to prevent the development of rickets → add vitamin D to water and rouse birds to encourage them to eat and drink

prevention of neonatal enteritis

no vaccines available!!

transmission for coronaviral enteritis of turkeys

• affects turkeys of any age, but severity is worse in young birds

• horizontal transmission via feces

• shedding can continue for days-week after recovery

• older, recovered birds serve as a reservoir for young, naive birds

clinical signs of coronaviral enteritis of turkeys

• young poults → depression, huddling, shrill chirping, drop in feed consumption, then water consumption, loss of body weight, watery or frothy droppings, variation in body size/unevenness

• associated with poult enteritis mortality syndrome

poult enteritis mortality syndrome

• intestines small, thin walled

• lumen filled with watery or frothy gaseous contents

• in turkey breeder hens → see rapid drop in egg production, white egg shells

treatment of coronaviral enteritis of turkeys

• provide extra heat

• increase ventilation

• keep birds as dry as possible to reduce stress and chilling

• antibiotics for secondary infections

prevention of coronaviral enteritis of turkeys

• depopulation of premises followed by cleaning/disinfection of buildings and equipment

• if multiple ages on farm, switch to single age operation

• no vaccine available

turkey viral hepatitis transmisison

• affects turkeys

• horizontal (fecal-oral) and vertical (hen to egg to poult)

• ducks and geese serve as natural reservoir

clinical signs of turkey viral hepatitis

• often subclinical unless another disease or stressor present

• depression and sporadic deaths

• coalescing focal hepatic necrosis with congestion and hemorrhage

• focal pancreatic necrosis

prevention of turkey viral enteritis

• do not continue to use eggs from breeders thought to be infected

• no vaccine available

transmission of inclusion body hepatitis (IBH)/ hepatitis-hydropericardium syndrome (HHS)

• affects chickens (broilers and layers) 3-15 weeks of age

• older than 15 weeks likely have developed immunity

• serotype D is most problematic

• vertical and horizontal transmission, fecal-oral

• clinical disease does not occur unless there is some type of stressor or immunosuppressive event

clinical signs of IBH

• sudden peak in mortality

• icterus, pallor, hepatomegaly, liver yellow-tan, mottled

• some outbreaks cause increased pericardial fluid

• areas of multifocal necrosis with intranuclear inclusion bodies may be found in liver, kidneys, heart

prevention of IBH

• vaccinate breeders

• do not use eggs from breeder flocks suspected of being infected

neonatal enteritis and infectious bronchitis may cause

nephritis leading to visceral/articular gout

infectious bursal disease (IBD) transmission

• affects chickens 3-6 weeks of age, but can occur in any chicken with a functional bursa of fabricius

• horizontal transmission, fecal-oral

• B-lymphocytotrophic virus replicates primarily in the bursa

clinical signs of IBD

• acute onset, tremors, depression, anorexia, ruffled feathers, vent picking, high morbidity, mortality may approach 30%

• bursa becomes edematous and congested, then atrophies in 7-8 days

• secondary bacterial infections occur as a result of immunosupression

prevention of IBD

• vaccinate breeders with killed vaccine

• may need to vaccinate young birds if strong field challenge

• treat secondary bacterial infections with antibiotics

hemorrhagic enteritis (HE) transmission

• affects primarily turkeys 6-12 weeks of age

• also seen in peasants and chickens

• horizontal transmission, fecal-oral

• replicates in/destroys B-cells and macrophages

clinical signs of HE

• with virulent strains → high morbidity, acute increase in mortality, decrease in feed and water consumption, bloody feces, blood-stained vent

• with avirulent strains → high morbidity, low mortality due to primary infection, but higher mortality due to secondary infection with E. coli or Salmonella

prevention of HE

• turkeys → live vaccine derived from peasant strain or avirulent turkey strain, administered in water at 5 weeks of age

• virulent strain from turkeys is used to vaccinate peasants

lymphoid leukosis transmission

• chickens only

• horizontal and vertical transmission → frequency of infected eggs is low but chickens hatched are permanently viremic and transmit horizontally

clinical signs of lymphoid leukosis

• in older birds → enlargement of abdomen due to B-lymphoblastoid tumors and neoplastic infiltration in many organs like liver, bursa, kidney, ovary

• do not see tumors in nervous system

• paraventricular hyperplasia seen in young broiler chickens associated with J subgroup

vaccine for lymphoid leukosis

no vaccine → must get rid of infected breeders

chicken infectious anemia transmission

• chickens only

• vertical and horizontal transmission

• susceptibility to infection rapidly decreases over the first 2-3 weeks of age

clinical signs of chicken infectious anemia

• failure to thrive, depressed

• bone marrow (watery), bursal, thymic and splenic atrophy

• aplastic anemia develops 14-16 days post-infection

• immunosuppression results in secondary bacterial/fungal infections

prevention of chicken infectious anemia

• vaccinate breeder hens

• never vaccinate while in lay due to vertical transmission

marek’s disease transmission

• chickens 2-7 months of age

• late marek’s occurs after onset of production because birds not well vaccinated

• horizontal transmission

• latent virus shed by infected chickens in feather follicle dander

clinical signs of marek’s disease

• T-lymphoblastoid tumors and inflammation acting as space occupying masses

• unique propensity to develop in nervous tissue→ associated with partial paralysis, blindness, graying of iris

prevention of marek’s disease

vaccination in ovo or at day 1 of age

egg drop syndrome transmission

• clinical disease only in chickens, but can recover disease from ducks and geese

• horizontal and vertical transmission

• virus remains latent until birds approach peak egg production

clinical signs of egg drop syndrome

• loss of color in pigmented eggs

• thin shelled and shell-less eggs

• failure to reach projected peak egg production levels

• ovaries and oviduct may atrophy

prevention of egg drop syndrome

• vaccinate layer pullets

• use killed vaccine because of latency and vertical transmission problems

reoviral arthritis/tenosynovitis transmission

• affects chickens and turkeys

• clinical disease seen in heavy meat-type birds

• horizontal transmission, recovered birds may serve as carriers

• vertical transmission suspected

clinical signs of reoviral arthritis

• lameness, foot pads, hock joints, and digital flexor/extensor tendons swollen

• often see rupture of tendons

• hock joint contains straw colored or blood tinged fluid, erosions in articular cartilage

prevention of reoviral arthritis

• sanitation

• broiler chicken most susceptible at 1 day of age

• vaccinate breeders to boost maternal/passive immunity

osteopetrosis transmission

• chickens, usually adults

• horizontal and vertical transmission

clinical signs of osteopetrosis

• long bones of legs

• appear thickened, periosteum, underlying bone often spongy but can become dense over time

prevention of osteopetrosis

• no vaccine

• eliminate breeders due to vertical transmission

avian encephalomyelitis transmission

• chickens and turkeys

• enteric virus that produces no signs in infected adults

• horizontal and vertical transmission

• young chicks without maternal antibody develop CNS disease

clinical signs of avian encephalomyelitis

• slight drop in egg production in adult birds

• young birds → dull expression, ataxia, tremors of head and neck, paresis progressing to paralysis

• necropsy → white spots in muscle of gizzard and proventriculus

• recovered birds may develop cataracts

prevention of avian encephalomyelitis

• vaccinate breeders

• attenuated live vaccine administered by wing web inoculation or in water

equine encephalitis (EEE) transmission

• infects poultry and many wild birds

• horizontally transmitted through mosquitoes

• birds serve as reservoir for equine diseases

• zoonotic

clinical signs of EEE

• birds usually aclinical

• occasionally will see depression, somnolence, incoordination, ataxia, circling, paresis, paralysis

• no gross lesions visible

prevention of EEE

• no vaccine for birds

• vector control