Viruses Flashcards
Gumboro
Infectious bursal disease
serotype 1 - subclinical, virulent or very virulent
shed in faeces, transmitted by fomites
morbidity 100%
mortality 5-60%
most susceptible 3-6w old
signs = incoordination, prostration, diarrhoea, vent picking. B cell response affected
PM = bursa edematous with yellow transudate and hemorrhage. congestion of pectoral and leg muscles and atrophy of the bursa
Gumboro diagnosis
gross bursal lesions and micro lymphocyte depletion, PCR and VI on 9-11d chorioallantoic
DD = mareks, IBH, aflatoxicoses
No treatment
Chicken anemia
CIAV
trans = feco-oral, maybe resp and through infected feather follicle epithelium. Vertical, in semen
SOI = contaminated litter
signs = anemia, weakness, weight loss, depress
PM = pale organs, atrophy of thymus and bursa, yellow bone marrow. BLUE WING - haemorrhage under skin
chicken anemia diagnosis
PCR, decreased hematocrits, history and signs
no treatment
prevent = live vaccine injection or in water before start of laying. maybe natural exposure but risky. vaccinate 7d old broilers in USA
very resistant to disinfectants and heat
lots of synergy with other immunosuppressive viruses so control those
Mareks epidemiology
alphaherpesviridae - MDV1 are mild, virulent and avirulent and MDV2 and 3 are avirulent
ubiquitous in environment
highly contagious and survives months in litter and dust - matures to infective form in epithelium in the feather follicle and then released to environment
affects older than 4w old
mareks pathogenesis
1 early cytolytic infection
2 latent
3 second phase of cytolytic infection - permanent immunosuppression
4 proliferative phase - lymphoid neoplasms
affects CD4 lymphocytes
mareks signs
transient paralysis, depression, atherosclerosis, death due to paralysis as birds can’t reach food
PM = enlarged nerves - vagus, brachial and siatic, tumours in liver, spleen, heart, lungs, enlarged feather follicles
mareks diagnosis
diagnose tumours not infection as ubiquitous. enlarged nerves, PCR
DD = reticuloendotheliosis (older chickens and no nerve changes) LL (no bursal tumour in LL, also 14w+ in LL)
mareks control
vaccine in hatchery or in ovo on 18th day of incubation
Lymphoid leukosis
avian retrovirus
affects B lymphocytes and 16w+ chickens
trans = shed in to yolk (congenital infection) and horizontal in faeces
not too highly contagious, trans decreased by good sanitation
outcomes:
1 no viremia, no antibody
2 no viremia with antibody
3 viremia with antibody
4 viremia no antibody
LL pathogenesis
transforms in intact bursa 4-8w PI
tumours detectable until 14w old, death around sexual maturity
subclinical decreases egg production with no tumours
signs of LL
inappetence, weakness, diarrhoea, emaciation
PM = tumours in liver, spleen, bursa, kidney
diagnosis of LL
history, signs, PM, histopath, IHC, VI, serology
control = no treatment or vaccine, eradicate from breeding stock (test eggs for antigen)
reticuloendotheliosis
reticuloendotheliosis virus 3 subtypes
trans = horizontal most common but vertical too, mosquitos and insects
pathogenesis reticuloendotheliosis
non neoplastic runting - 4-10 w old
acute neoplastic - after 6-8w latent period, T cells
chronic - B cells affected, looks like LL
signs reticuloendotheliosis
weight loss, paleness, occasional paralysis and abnormal feathering
PM = abnormal feathers, bursa and thymic atrophy, tumours in liver, spleen
diagnosis reticuloendotheliosis
history, signs, difficult PM, PCR
control = none practiced
no treatment
egg drop syndrome
duck adenovirus 1
spread by contaminated Mareks disease vaccine
trans = vertical most frequent, horizontal
most susceptible = broiler parents and brown egg layers
in ovo infected show signs at sexual maturity
signs egg drop
transient diarrhoea, apathy, decreased egg production, rough/thin shells, loss of shell pigment
diagnosis egg drop
IHA test, gel immunodiffusion
DD = Newcastle, IB, AE
prevent = inactivated vaccine at 14-20w
age LL
older than 16w
age reticuloendotheliosis
older than 17w
age mareks
older than 4w
bursa lesions neoplastic diseases
LL nodular changes
RE rare atrophy
M rare diffuser atrophy
cells affected neoplastic diseases
LL B lymphocytes
RE B and T lymphocytes
M CD4 lymphocytes
avian encephalomyelitis
AEV - epidemic tremor
trans = vertical and horizontal (feco-oral)
morbidity and mortality up to 50%
AE signs
ataxia, tremors, weakness, paralysis, biphasic mortality pattern
PM = no gross lesion on Brian, maybe cataracts in survivors
diagnosis AE
history, signs, PM, RT-PCR, IHC, VI of brain, duodenum or pancreas
DD = bacterial/mycotic encephalitis, neurotropic Newcastle, rickets, nutritional encephalomalacia
prevent AE
no treatment
vaccinate broiler pullets at 8w old or 4w before laying, often combined with fowl pox and given by wing web stab
IBH and hydropericardium syndrome
fowl adenovirus
trans = vertical and horizontal
signs = sudden mortality in less than 6w old chicks, lethargy, huddling, ruffled feathers, yellow mucoid droppings
PM IBH and hydropericardium
swollen enlarged liver w yellow discolouration. HHS = straw coloured transudate in pericardial sac
diagnosis IBH and HHS
mortality pattern and gross lesions
histopathology and PCR
no treatment
prevent = live or inactivated vaccine
hemorrhagic enteritis
Turkey adenovirus 3 (siadenovirus)
trans = feco-oral/cloacal and contam equipment
signs hemorrgaic enteritis
100% morbidity, 1-60% mortality
7-9w old turkeys, depress, pallor, bloody faeces, 2nd bacteria infections 2w later so second wave of mortality
PM = congestion and haemorrhage in SI and enlarged friable mottled spleen