JPC SYSTEMIC PATHOLOGY

HEMOLYMPHATICS SYSTEMS

April 2024

H-V01

 

Signalment (JPC #1759387): Tissue from a chicken.

 

HISTORY: None

 

HISTOPATHOLOGIC DESCRIPTION: Scalded and plucked skin: Multifocally within the superficial dermis, deep dermis, and panniculus, adjacent to feather follicles, arrector pullorum muscles, vessels, adipocytes, and occasionally nerves, there are nodular, up to 400 µm diameter aggregates of small and medium sized lymphocytes admixed with occasional lymphoblasts/large lymphocytes, macrophages, and heterophils; these aggregates are surrounded by areas of fibrosis. The epidermis and feathers are missing and there is disruption of dermal collagen (scalding and plucking artifact).

 

MORPHOLOGIC DIAGNOSIS: Feathered skin: Dermatitis, perifolliculitis, and panniculitis, lymphoproliferative, nodular, multifocal, moderate, chicken, avian.

 

ETIOLOGIC DIAGNOSIS: Alphaherpesviral dermatitis

 

CAUSE: Marek’s disease virus (serotype 1), gallid herpesvirus 2

 

CONDITION: Marek’s disease (MD)

 

SYNONYMS: Fowl or range paralysis, polyneuritis, neurolymphomatosis gallinarum

 

GENERAL DISCUSSION: 

• Highly contagious double-stranded DNA alphaherpesvirus with worldwide distribution
• Progressive T-cell lymphoproliferative disease with variable signs and several overlapping syndromes; most often occurs between 2-7 months of age
• The most common lymphoproliferative disease of chickens; vaccination has dramatically reduced the incidence of the disease, but not of infection
• Marek’s disease virus (MDV) serotypes MDV-2 and MDV-3 (herpesvirus of turkeys) are non-oncogenic and primarily used for immunization against MDV-1
• In a recent report of mortality in backyard poultry in eight states in the US, the most common primary diagnosis was neoplasia or lymphoproliferative disease (42% of total birds autopsied); 63% of these had Marek's disease or leukosis/sarcoma (Cadmus, J Vet Diagn Invest. 2019)

 

PATHOGENESIS:

• Enveloped virus (cell-free) shed primarily in feather follicle dander, also present in excretions/secretions but of lesser importance; virus is infective up to 8 months on dried feathers; subclinical infection with virus shedding is common
• Infection occurs through inhalation; vertical transmission does not occur; viral replication occurs in the feather follicle epithelium
• Four phases of infection 
  • Inhalation of virus à infection of respiratory epithelial cells and local macrophages à viremia à cytolytic viral replication in lymphocytes 
  • Latency in CD4+ T cells à systemic viral spread, including cutaneous viral infection, replication, and shedding
  • Reactivation of CD4+ T cells à late cytolytic stage and immunosuppression
  • Viral reactivation and neoplastic transformation of CD4+ T cells
• Important MD-specific genes: 
  • Meq (MDV-EcoRI-Q): Oncogene; one of the most important determinants of oncogenicity (Kurokawa, J Vet Diagn Invest, 2022) 
  • vTR: Viral homologue of telomerase (Wilson, J Comp Path, 2022)
  • pp38: Virus replication 

 

TYPICAL CLINICAL FINDINGS:

• In neurologic disease, progressive unilateral or bilateral ascending paralysis
• Neurolymphomatosis (classical MD): Incoordination, asymmetric progressive paresis and uni- or bilateral paralysis of legs or wings; often one leg held forward and the other backward (hurdler’s position); wing dropping; torticollis; dilation of the crop and gasping if vagus nerve is involved
• Transient paralysis: Variable ataxia to partial or complete paralysis lasting only 1-2 days; the syndrome appears to be caused by vasogenic brain edema; many birds recover only to succumb to clinical MD a few weeks later
• Acute MD (Fowl paralysis): Explosive outbreaks in young chickens; widespread depression followed by ataxia and paralysis of some; significant mortality without localized neurologic signs; absent visceral lymphoma but prominent nerve lesions
• Ocular lymphomatosis: Partial or total blindness; death from starvation and dehydration because of inability to reach food/water
• Cutaneous MD: Nodular skin lesions 
• Chronic ill-thrift: Neoplastic lesions in various internal organs
• MDV-induced severe immunosuppression can lead to secondary infection
• Severe necrotic dermatitis has been reported in the combs of White Leghorn chickens genetically resistant to the MD viral-induced tumor development; secondary bacterial infection due to immunosuppression
• Outbreaks in vaccinated layers can occur after onset of egg production (> 5 months) associated with vv+ MDV, called “late Marek’s” 

 

TYPICAL GROSS FINDINGS:

• Enlargement up to three times normal of peripheral nerves; often unilateral; affected nerves may lose cross striations and be discolored yellow
• Visceral tumors are the most common lesion, forming small or diffuse, grayish and translucent nodules or general enlargement with diffuse grayish discoloration
• Ocular lesions: Uni- or bilateral graying of the iris with irregular pupilsdue to lymphoblastoid cell infiltration; irregular and eccentric pupil; iritis and uveitis
• Cutaneous lesions: Round, nodular lesions up to 1 cm in diameter, particularly around feather follicles, may have red skin of non-feathered legs

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• A mixture of pleomorphic lymphocytes (likely a mixture of neoplastic CD-4+ T-cells and reactive/inflammatory B/T cells, macrophages)
• Bursa (if affected): Expansion of plica by lymphocytes within the interfollicular tissue with eventual destruction of follicles; remaining follicles atrophied
• Skin: Coalescing aggregates of small lymphocytes around affected feather follicles and in feather pulp; as malignant transformation occurs, the aggregates become larger and contain more medium and large lymphocytes and blast cells; eventually these cells replace dermal structure and cause follicular and epidermal atrophy; eosinophilic intranuclear inclusion bodies may occur within transitional zone and stratum corneum of feather follicle epithelium; syncytial cells are not seen
• Peripheral nerves (autonomic and motor nerves): Polymorphic mononuclear infiltrates or (infrequently) infiltrates of neoplastic T cells as part of a systemic disease; lymphocytic ganglioneuritis in dorsal root and autonomic ganglia; may have edema, demyelination; lesions in motor nerves are classified as type A (neoplastic) or type B (inflammatory) 
• CNS: Cerebral perivascular cuffing, vasculitis, edema, gliosis, lymphocytic meningitis
• Visceral organs: Most common site for lymphoid tumors
• Eye: Lymphocytes present in anterior and posterior uvea; very virulent strains may produce eosinophilic intranuclear inclusions in lymphocytes in the cornea and retinal ganglia cells

 

ULTRASTRUCTURAL FINDINGS:

• Enveloped 150-160 nm diameter, dsDNA virus with 85-100 nm icosahedral nucleocapsid
• Virions are common in the nucleus but rare in cytoplasm and extracellular spaces
• Within feather follicle epithelium, the enveloped viral particles are 273-400 nm

 

ADDITIONAL DIAGNOSTIC TESTS:  

• Virus isolation, conventional PCR, or antibody serology alone are not confirmatory as the virus is ubiquitous and most chicken flocks are persistently infected
• Histologic examination (with IHC to determine lymphocyte type) and real-time PCR to quantify MDV copies are reliable methods for diagnosis (Kurokawa, J Vet Diagn Invest, 2022)
• Transformed MD-infected T-cells often overexpress an activated T-cell surface marker, MD tumor-associated surface antigen (MATSA) and only few are positive for IgM 
• IHC recently developed for MeQ (Kurokawa, J Vet Diagn Invest, 2022)

 

DIFFERENTIAL DIAGNOSIS:  

Other causes of lymphoproliferative disease in chickens:

• Lymphoid leukosis (avian leukosis, retrovirus): Primary differential; see chart below
• Reticuloendotheliosis virus (retrovirus): Causes non-neoplastic runting syndrome (bursal and thymic atrophy), acute neoplastic disease resulting in T-cell lymphomas (resembles Marek’s disease), and chronic neoplastic disease resulting in B-cell lymphomas (resembles lymphoid leukosis); in chickens, turkeys, ducks, quail, and geese after either experimental or accidental infection from contaminated vaccines
• Recent report in three flocks in China of coinfection with ALV subgroup J, MDV, and REV; fluorescent multiplex immunohistochemistry revealed individual cells coinfected with all three viruses (Liu, J Vet Diagn Invest, 2019)

 

FEATURES	LYMPHOID LEUKOSIS	MAREK'S DISEASE
Etiology	Type C  Retrovirus	Alphaherpesvirus
Age	> 16 weeks	> 4 weeks (usually 2-5 months)
Paralysis	Absent	Present
Bursa of Fabricius	Nodular tumor	Diffuse enlargement, or  atrophy (or no lesions)
Skin or Muscle Involvement	Absent	May be present
Peripheral Nerve Infiltration	Absent	Present
Bursal Proliferation	Intrafollicular	Interfollicular
Lymphoid Cells	Uniform blasts	Pleomorphic
Tumor Cell Type	Predominantly B-cells	Predominantly T-cells
Tumor Cell	> 90% IgM+	< 5% IgM+

 

COMPARATIVE PATHOLOGY: 

Viruses that can induce tumors in domestic or laboratory animals. Adapted from Fenner’s Veterinary Virology (2017).

Family/Genus	Virus	Type of Tumor
DNA viruses
Poxviridae*/Leporipoxvirus	Rabbit fibroma virus and squirrel fibroma virus	Fibromas and myxomas in rabbits and squirrels (hyperplasia rather than neoplasia)
Poxviridae*/Yatapoxvirus	Yaba monkey tumor virus	Histiocytoma in monkeys
Herpesviridae/ Alphaherpesvirinae/ Mardivirus	Marek’s disease virus	T-cell lymphoma in fowl
Herpesviridae/ Gammaherpesvirinae/ Lymphocryptovirus	Epstein-Barr virus     Baboon herpes virus	Burkitt’s lymphoma, nasopharyngeal carcinoma, and B-cell lymphomas in humans and monkeys   Lymphomas in baboons
Herpesviridae/ Gammaherpesvirinae/ Rhadinovirus	Cottontail rabbit herpesvirus	Lymphoma in rabbits
Alloherpesviridae/ ranid herpesvirus	Lucké frog herpesvirus	Renal adenocarcinoma in frogs and tadpoles
Papillomaviridae/ multiple genera	Cottontail rabbit papillomavirus	Papillomas, skin cancers in rabbits
	Bovine papillomavirus 1,4	Papillomas, carcinoma of gastrointestinal tract
	Bovine papillomavirus 1,2	Papillomas, carcinoma of urinary bladder
	Bovine papillomavirus 7	Papillomas, carcinoma of eye
	Equine papillomavirus	Squamous cell carcinoma
Polyomaviridae/Polyomavirus	Raccoon polyomavirus	Central nervous system tumors in racoons
	Murine polyomavirus	Tumors in newborn rodents
Reverse Transcribing viruses
Hepadnaviridae: Orthohepadnavirus	Human, woodchuck hepatitis viruses	Hepatocellular carcinomas in humans and woodchucks
Hepadnaviridae: Avihepadnavirus	Duck hepatitis virus	Hepatocellular carcinomas in ducks
Retroviridae: Alpharetrovirus	Avian leukosis viruses	Leukosis (lymphoma, leukemia), osteopetrosis, nephroblastoma in fowl
	Rous sarcoma virus	Sarcoma in fowl
	Avian myeloblastosis virus	Myeloblastosis in fowl
Retroviridae: Betaretrovirus	Mouse mammary tumor virus	Mammary carcinoma in mice
	Mason-Pfizer monkey virus	Sarcoma and immunodeficiency disease in monkeys
	Ovine pulmonary adenocarcinoma virus (Jaagsiekte virus)	Pulmonary adenocarcinoma in sheep
Retroviridae: Gammaretrovirus	Feline leukemia virus	Leukemia in cats
	Feline sarcoma virus	Sarcoma in cats
	Murine leukemia and sarcoma viruses	Leukemia, lymphoma, and sarcoma in mice
Retroviridae: Deltaretrovirus	Avian reticuloendotheliosis virus	Reticuloendotheliosis in fowl
	Bovine leukemia virus	Leukemia (B-cell lymphoma) in cattle

* Not true oncogenic viruses. They differ from all other viruses listed in that poxviruses replicate in cytoplasm and do not affect the cellular genome.

 

REFERENCES:

1. Abdul-Aziz T, Fletcher OJ. Endocrine System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 562, 563, 580.
2. Abdul-Aziz T, Fletcher OJ. Cardiovascular System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 178, 179, 193, 194.
3. Barnes JH, Fletcher OJ. Hemic System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 47, 48, 67, 68. 
4. Barnes HJ, Fletcher OH, Abdul-Aziz T. Reproductive System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 608, 609. 
5. Cadmus K, Mete A, Harris M, et al. Causes of mortality in backyard poultry in eight states in the United States. J Vet Diagn Invest. 2019;31(3) 318-326.
6. Crespo R, Franca M, Fenton H, Shivaprasad HL. Galliformes and columbiformes. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier. 2018:753-754.
7. Fletcher OJ, Abdul-Aziz T. Alimentary System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 350.
8. Fletcher OJ, Abdul-Aziz T. Respiratory System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 256, 257.
9. Fletcher OJ, Barnes HJ, Abdul-Aziz T. Skeletal System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 112, 129.
10. Hongmei L, Kui M, Miaomiao L, Chengcheng Y, Xueting H. Histologic findings and viral antigen distribution in natural coinfection of layer hens with subgroup J avian leukosis virus, Marek's disease virus, and reticuloendotheliosis virus. J Vet Diagn Invest. 2019, Vol. 31(5) 761–765.
11. Kurokawa A, Yamamoto Y. Development of monoclonal antibodies specific to Marek disease virus-EcoRI-Q (Meq) for the immunohistochemical diagnosis of Marek disease using formalin-fixed, paraffin-embedded samples. J Vet Diagn Invest. 2022; 34(3): 458-464.
12. Liu H, Ma K, Liu M, et. al. Histologic findings and viral antigen distribution in natural coinfection of layer hens with subgroup J avian leukosis virus, Marek's disease virus, and reticuloendotheliosis virus. J Vet Diagn Invest. 2019 ;31(5):761-765.
13. MacLachlan NJ, Dubovi EJ, eds. Fenner’s Veterinary Virology. 5th ed. Cambridge, MA: Elsevier; 2017:76-78,191-193,196-198.
14. Sellers H, Ojkic D. Viral diseases. In: Boulianne M, ed.  Avian Disease Manual. 7th ed.  Jacksonville, FL: American Association of Avian Pathologists, Inc; 2019:34-40.
15. Shivaprasad HL. Eye and Ear. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 523, 537, 538, 542.
16. Shivaprasad HL, Barnes HJ. Integumentary System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 618, 639.
17. Swayne DE, Barnes HJ, Abdul-Aziz T, Fletcher OJ. Nervous System. In: Abdul-Aziz T, Fletcher OJ, Barnes HJ, eds. Avian Histopathology. 4^th ed. Madison, WI: Omnipress. 2016; 473, 497-503. 
18. Wilson LA, Lewis M, Baigent SJ. Marek’s Disease in an Indian Peafowl (Pavo cristatus) with Clinical Ocular Disease and Paraparesis. J Comp Pathol. 2022; 195: 7-11.

 

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