Avian Diseases, Pt. 2 Flashcards
What causes Marek’s disease? What species are most affected?
avian alphaherpesvirus, Gallid herpesvirus type 2 (dsDNA)
chickens
- quails, turkeys, pheasants, jungle fowl
How is Marek’s disease transmitted? What kind of disease is it?
highly infectious, particularly in young chicks through feather dust, where it can remain infectious for years (inhaled)
lymphoproliferative and neoplastic - first neoplastic disease for which a vaccine was developed
What are the 3 serovars of Marek’s disease virus?
1 = oncogenic
2 = chickens
3 = turkeys
(other oncogenic virus = avian leukosis virus, a retrovirus)
What are the 4 phases of Marek’s disease?
- early cell-to-cell infection
- latent infection
- feather follicle shedding
- proliferative (lymphoma) phase
What happens during phase 1 of Marek’s disease?
- inhalation or ingestion of infected feather dander
- infection of respiratory epithelium and macrophages
- viremia
- infection of T and B cells in thymus, bursa, spleen, and BM, causing immunosuppression
What happens during phase 2 of Marek’s disease?
- replication in T cells (CD4+), less so in B cells and CD8+ cells
- no obvious clinical signs
(latent infection)
What happens during phase 3 of Marek’s disease?
- lymphocytes carry virus to feather follicles
- virus replicates in epithelial cells
- virus shed in feather dander
- lymphocytes also carry virus to visceral epithelium and nervous system
- mononuclear inflammation
What happens during phase 4 of Marek’s disease?
- some CD4+ T cells undergo neoplastic transformation
- lymphomas develop
- tumors are a mixture of neoplastic T cells and reactive B cells and macrophages
What is characteristic of classical Marek’s disease? In what 3 ways does this affect the bird?
neurolymphomatosis = paralysis
- leg/wing paralysis (sciatic/brachial nerves)
- torticollis (cervical nerves)
- dilation of crop and respiratory signs (vagus/intercostal nerves)
What are the 3 other presentations of Marek’s disease other than classical?
- VISCERAL (ACUTE) - lymphomatous proliferation (tumors) in viscera and skin
- OCULAR LYMPHOMATOSIS - lymphocyte infiltration of iris with loss of pigmentation (grey eye)
- CUTANEOUS - enlarged feather follicles/nodules, erythematous legs (Alabama redleg)
Classical Marek’s disease:
paralysis - sciatic nerve
Classical Marek’s disease:
left sciatic nerve thick due to lymphocyte inflammation
Visceral (acute) Marek’s disease:
nodular lymphoblastic lesions
Ocular Marek’s disease:
grey eye - lymphocyte infiltration of iris
Ocular Marek’s disease:
grey eye, constricts pupil due to inflammation
Cutaneous Marek’s disease:
Alabama redleg - erythematous legs
Cutaneous Marek’s disease:
enlarged feather follicles/nodules
What are the 2 main histopathological presentations of classical Marek’s disease?
- PNS = proliferative/inflammatory with demyelination, causing paralysis; chronic without paralysis
- CNS = inflammatory lesions with perivascular cuffing, microgliosis, and endotheliosis
What is the histopathological presentation of visceral (acute) Marek’s disease?
lymphoid tumors with a mixture of pleomorphic lymphocytes including malignant T cells, reactive B cells, other T cells, and macrophages
What is the histopathological presentation of ocular lymphomatosis due to Marek’s disease?
lymphocyte infiltration of the iris
What are the 3 histopathological presentations of cutaneous Marek’s disease?
- dermatitis with lymphocytes and/or lymphomatous proliferations
- lymphomatous lesions around feather follicles and blood vessels
- IN inclusions in feather follicle epithelium
Classical Marek’s disease, histopathology:
PNS = inflammation
Cutaneous Marek’s disease, histopathology:
perivascular lymphomatous lesion
How is Marek’s disease diagnosed? How is it controlled? Is it zoonotic?
PCR, IHC
- virus isolation, IFA, viral neutralization
chicks are typically vaccinated by 1 day old
no
Marek’s disease vs. Lymphoid leukosis:
What causes Newcastle disease? How does it compare to others in the same family?
avian Paramyxovirus 1 (ssRNA)
reportable to OIE - does not cause paramyxovirus infection
What species are most affected by Newcastle disease? What are some potential reservoirs?
chickens
waterfowl, psittacines
What 2 things determine the pathogenicity of avian Paramyxovirus 1?
strain
1. ICPI - intracerebral pathogenicity index
2. F protein sequence - penetrates host cell membrane
(VELOGENIC - viscerotropic, neurotropic)
What is the main way that Newcastle disease is transmitted? How else can it be transmitted?
ingestion of inhalation of infected secretions (feces, respiratory secretions, excretions)
- fomites
- vertical
What is the pathogenesis of Newcastle disease?
- ingestion/inhalation of infected secretions
- virus replicated in the mucosa of the upper respiratory and/or intestine
- virus spreads by hematogenous route (primary viremia) adhered to RBC
- virus infects spleen and BM
- virus spreads hematogenously to CNS and/or other organs (secondary viremia)
- virus is shed through respiratory secretions, excretions, or feces
How does viscerotropic velogenic Newcastle disease present?
- acutely lethal, kills chickens of all ages
- weakness, anorexia
- green diarrhea
- prostration, tremors, torticollis, paralysis, opisthotonus
- death
flock mortality can reach 100%
How does neurotrophic velogenic Newcastle disease present?
- acutely lethal, kills chickens of all ages
- sharp decrease in egg production
- weakness, anorexia
- RESPIRATORY SIGNS: difficulty breathing, wheezing, gurgling, conjunctivitis
- NERVOUS SIGNS: prostrations, tremors, torticollis, paralysis, opsthotonus
Neurotrophic velogenic Newcastle disease:
torticollis
What gross lesions present in visceral and neurotropic velogenic Newcastle disease?
VVND = necrotizing gastroenteritis and hemorrhage at junctions
NVND = pneumonia and/or encephalitis
What 3 histopathological presentations are common with visceral velogenic Newcastle disease?
- necrotizing gastroenteritis
- hemorrhages in junctions of the esophagus, proventriculus, and gizzard
- GALT necrosis
What 2 histopathological presentations are common with neurotropic velogenic Newcastle disease?
- interstitial pneumonia
- non-suppurative encephalitis with lymphocyte perivascular cuffing, endotheliosis, and inclusion bodies
Newcastle disease, CNS:
spheroids - swollen axons and demyelination
Newcastle disease, CNS:
neuronal necrosis - red = dead, pyknotic nuclei
Newcastle disease, neuronal inclusion bodies:
Newcastle disease, CNS (cerebellum):
pink neuronal inclusion bodies
Newcastle disease, CNS:
neuronal inclusion bodies - IN and IC
How does the OIE diagnose Newcastle disease? What else can be done?
virus isolation and qPCR NVSL panel
- hemagglutination for unvaccinated flocks
- IHC
- immunochromatographic strips
How is Newcastle disease controlled?
- vaccines: live attenuated in water, aerosol, eye/nose droplets, beak dipping; inactivated
- hygiene/biosecurity
Is Newcastle disease zoonotic?
yes, but rare
- immunosuppression increases risk
- veterinarians, processing plant employees, lab workers, and vaccination crews are most susceptible
What are the 3 major clinical signs of Newcastle disease in humans?
- self-limiting conjunctivitis*
- excessive lacrimation, eyelid edema, subconjunctival hemorrhage, unilateral/bilateral reddening
- generalized infection - fever, headache, chills
What causes Bornavirus disease? What are some other names?
avian Bornavirus (ABV) - ssRNA virus with nuclear replication
- Macaw wasting disease
- Psittacine Proventricular Dilatation Disease
- Proventricular Dilatation Disease
- Neuropathic gastric dilatation
What 2 species are most affected by Bornavirus disease?
- Pisttacines, canaries, finches
- Canada goose
What does avian Bornavirus target?
- autonomic nerves of the upper and middle GI: esophagus, crop, proventriculus, gizzard, duodenum
- CNS: cerebellum, cerebrum, brainstem
What is thought to be the infection route of Bornavirus disease? What happens after infection?
- trauma/inoculation in skin
- fecal-oral, respiratory
migration to nervous ganglia (and CNS in Canada goose) with retrograde axonal transport
What are the 6 common clinical signs of Bornavirus disease?
- weight loss - no movement or digestion of food
- crop stasis, proventricular/ventricular dilatation, regurgitation
- undigested material in feces
- starvation
- CNS signs - ataxia, loss of predator reflex
- death
Bornavirus disease, radiography:
flaccidity and dilation of proventriculus, ventriculus, and crop
What are 4 common postmortem gross findings of Bornavirus disease?
- emaciation
- falccidity and dilation of proventriculus, ventriculus, and crop
- lack of muscular grinding of seeds - undigested material in feces
- possible cardiomegaly and hydropericardium
Bornavirus, GI:
dilatation - proventriculus, ventriculus, crop
What 3 places do lymphocytes and plasma cells infiltrate in Bornavirus disease?
- myenteric plexus, ganglia, and peripheral nerves
- brain and spinal cord
- heart and adrenal glands
What histopathology is characteristic in the CNS in Bornavirus disease?
demyelination and perivascular cuffing with Purkinje cell necrosis
Bornavirus disease, CNS:
encephalitis - mononuclear perivascular cuffs
Bornavirus disease, PNS:
neuritis - perivascular cuffs of lymphocytes and fewer macrophages and plasma cells
Bornavirus disease, PNS (ganglia):
ganglioneuritis - lymphocytes with fewer macrophages and plasma cells
How is Bornavirus disease diagnosed?
- ANTEMORTEM: qPCR plucked feathers
- clinical signs and gross findings
- histopathology and IHC
neuron is dark due to nuclear replication