Turkey coronavirus enteritis aka
Bluecomb disease
Mud fever
Transmissible enteritis
(A coronavirus that replicates in the cytoplasm)
CS of Turkey coronavirus enteritis
- sudden onset depression, anorexia
- decreased water consumption
- watery diarrhea
- poor growth, dec. egg prod./quality
- high Mb, moderate Mt depending on 2ary infections
Trans. Of turkey coronavirus enteritis
- shed in feces
- horizontal trans. Via ingestion and fomites
- wild birds, rodents, dogs, flies = mechanical vectors
- beetle larvae?
Gross path. Of turkey coronavirus enteritis
- pale and flaccid duodenum and jejunum
- distended ceca with watery contents
- visible wt. loss + dehydration
- atrophied bursa of Fabricius
Microscopic pathology of turkey coronavirus enteritis
Intestines:
- shortening of villi
- columnar –> cuboidal epithelium
- microvilli loss
- lamina propria infiltrated w/ lymphocytes, heterophils
Bursa of F:
- epithelial necrosis/hyperplasia
- heterophilic inflamm.
- lymphoid depletion
Immunity to turkey coronavirus enteritis
- flocks that recover are resistant to reinfection (suggests virus only has one serotype)
- IgA persists in intestinal secretions and bile for >6 months
Dx of turkey coronavirus enteritis
- via inoculation of embryonated eggs
- virus recovered from intestines and bursa of F and ID’d by PCR, EM, IF, or IP**
- SPF chicks infected experimentally
Prevention and control of turkey coronavirus enteritis
- biosecurity!
- no vaccine, no specific tx
- abx control 2ary infection only
- increase temp of brooder house
- avoid overcrowding
Avian metapneumovirus infection caused by what kind of virus
Paramyxovirus (ss RNA virus)
- surface projections = key to immunity**
- very fragile viruses - sensitive disinfectants
- has 4 substypes A,B,C,D (differentiated by sequencing)
- causes dz in chickens and turkeys of all ages in most countries
Sequelae of Avian metapneumovirus infection
- Poor performance and mortality in meat turkeys and broilers
- Poor egg prod. In breeders in layers
Distribution of avian metapneumovirus subtypes
A and B: Everywhere except USA, Australia, and NZ. Most common in Europe
C: causes dz in turkeys in the US, causes dz in ducks in France, causes dz in pheasants in S. Korea**
D: only in France
Subtypes A and B cross-protect against each other
Epi of Avian metapneumovirus
- Turkeys = most important natural host**
- most severe CS in young poults and broilers
- High Mb, variable Mt
Trans. Of Avian metapneumovirus
- Horizontal: aerosol, infected organic materials, fomites
- Vertical: no clear evidence
2 most important sites of virus replication of Avian metapneumovirus
- respiratory tract
- repro tract
Pathogenesis of avian metapneumovirus: turkeys vs. chickens
Turkeys: short incubation, rapid spread
Chickens: may be asymptomatic, or may present with “swollen head syndrome” char. By swollen infraorbital sinuses, submandibular swelling
CS of avian metapneumovirus
Resp. Signs: young chickens and turkey poults are depressed, frequently huddle, gasping, coughing, tracheal rales, nasal/ocular discharge
Drop in egg prod.
Lesions of avian metapneumovirus: turkeys vs. chickens
Turkeys:
- watery to mucous exudates in turbinates
- excess mucous in trachea
- peritonitis, fluid yolk material in abd.
- foamy/frothy eye
- pneumonia, air sacculitis, pericarditis, perihepatitis if 2ary infections
Chickens:
- Swollen head syndrome
- bad yellow gelatinous/purulent edema under skin of head, neck, and wattles
- eyelids may be swollen shut
Ddx of avian metapneumovirus
- NCD
- Infectious coryza
- Infectious bronchitis
CS indicative, but not definitive
Dx of avian metapneumovirus
- detect viral RNA using RT-PCR
- Ag detection (IF, IHC, EM)
- Ab detection (virus neutralization, ELISA**)
- virus isolation: tracheal ring cultures, yolk sac of SPF eggs
Vaccination for avian metapneumovirus
- vax broilers and young turkeys w/ live-attenuated
- vax breeders and layers w/live-attenuated as a primer at 2-4 wks, then inactivated vax as adults
Cause of avian lymphoid leukosis
- exogenous RNA tumor viruses (oncoviruses)
- Endogenous leukosis viruses not known to be oncogenic
Trans. Of avian lymphoid leukosis virus
Exogenous viruses:
-VERTICAL TRANSMISSION** from hen to chicks through the egg. Chicks hatch viremic and shed virus in saliva and feces –> HORIZONTAL transmission
Endogenous viruses:
-trans. Genetically by rooster and hen. Not oncogenic
Pathogenesis of avian lymphoid leukosis
Target organ = bursa of fabricius**
Transformation of lymphoid cells (B-cell precursors**) in follicle within bursa of F –> origination of tumors
Gross tumors found after 16 wks old
NO NERVE INVOLVEMENT (differentiates LL from Marek’s disease!**)
See pic “tumors caused by replication-competent avian retroviruses”
:)
See pic “tumors caused by replication-defective avian retroviruses”
:)
Renal tumors target what cells and cause what lesion?
Renal cells –> nephroblastomas
Osteopetrosis targets what cells and causes what lesion?
Osteoclasts/osteoblasts –> thickened long bones
Lymphoid leukosis targets what cells and causes what lesion?
B cells in bursa of F –> solid tumors of malignant lymphoblasts
-can have tumors in liver, kidneys, spleen, viscera, ovaries, etc.
Erythroblastosis targets what cells and causes what lesion?
Erythroblasts –> anemia, LIV/SP/KID enlargement and congestion
Myeloblastosis targets what cells and causes what lesion?
Myeloblasts –> anemia/leukemia
Myelocytomatosis targets what cells and causes what lesion?
Myelocyte –> sarcomas
Hemangioma targets what cells and causes what lesion?
Capillary endothelium –> hemangioma
Sarcomas targets what cells and causes what lesion?
Various mesenchymal cells –> sarcoma
Frank leukemia is commonly/seldom observed with avian LL?
Seldom
When infected with avian LL, transformed lymphoblasts secrete large amounts of what Ab?**
IgM (NOT IgY or IgA) - there is never a switch
Malignant lymphoblasts in tumors caused by avian LL express what markers?**
B lymphocyte markers
Prevention of tumor development 2ary to avian LL
Bursectomy up to 10-12 wks of age
Dx of lymphoid leukosis
-tumor cells are of bursa of F origin with B cell surface markers which can be ID’d with an antiserum
- PCR
- absence of Marek’s MEQ gene
How does the microscopic pathology of lymphoid leukosis compare to marek’s dz?**
Tumor cells of LL are of homogenous size and shape**
Control of avian LL**
- eradication of exogenous LLVs from breeders or genetic stock
- NO vaccine available
- biosecurity to avoid introduction!
Leukosis J virus emerged by recombination between exogenous and endogenous viruses and induces:**
Myelocytomas
