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being in neural tissue. Mortality of chickens infected with Marek's disease was quite low. Current strains of Marek virus, decades after the first vaccine was introduced, cause lymphoma formation throughout the chicken's body and mortality rates have reached 100% in unvaccinated chickens. The Marek's disease vaccine is a "leaky vaccine", which means that only the symptoms of the disease are prevented. Infection of the host and the transmission of the virus are not inhibited by the vaccine. This contrasts with most other vaccines, where infection of the host is prevented.
362:
lines such as large lymphocyte, lymphoblast, primitive reticular cells, and occasional plasma cells, as well as macrophage and plasma cells. The T cells are involved in the malignancy, showing neoplastic changes with evidence of mitosis. The lymphomatous infiltrates need to be differentiated from other conditions that affect poultry including lymphoid leukosis and reticuloendotheliosis, as well as an inflammatory event associated with hyperplastic changes of the affected tissue.
35:
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strains are virulent enough to induce symptoms but not enough to kill the host, allowing further transmission. However, the leaky vaccine changes this evolutionary pressure and permits the evolution of highly virulent strains. The vaccine's inability to prevent infection and transmission allows the spread of highly virulent strains among vaccinated chickens. The
454:
Because vaccination does not prevent infection with the virus, Marek's is still transmissible from vaccinated flocks to other birds, including the wild bird population. The first Marek's disease vaccine was introduced in 1970. The disease would cause mild paralysis, with the only identifiable lesions
466:
The evolution of Marek's disease due to vaccination has had a profound effect on the poultry industry. All chickens across the globe are now vaccinated against Marek's disease (birds hatched in private flocks for laying or exhibition are rarely vaccinated). Highly virulent strains have been selected
414:
It is recommended that all flocks positive for Marek's disease remain closed, with no bird being introduced or leaving the flock. Strict biosecurity and proper cleaning is essential, using products like
Activated Oxine or Virkon S and reducing dander buildup in the environment. Proper diet, regular
361:
The presence of nodules on the internal organs may also suggest Marek's disease, but further testing is required for confirmation. This is done through histological demonstration of lymphomatous infiltration into the affected tissue. A range of leukocytes can be involved, including lymphocytic cell
357:
The demonstration of peripheral nerve enlargement along with suggestive clinical signs in a bird that is around three to four months old (with or without visceral tumors) is highly suggestive of Marek's disease. Histological examination of nerves reveals infiltration of pleomorphic neoplastic and
458:
Under normal conditions, highly virulent strains of the virus are not selected for by evolution. This is because such a severe strain would kill the host before the virus would have an opportunity to transmit to other potential hosts and replicate. Thus, less virulent strains are selected. These
397:
In addition to gross pathology and histology, other advanced procedures used for a definitive diagnosis of Marek's disease include immunohistochemistry to identify cell type and virus-specific antigens, standard and quantitative PCR for identification of the virus, virus isolation to confirm
342:
Diagnosis of lymphoid tumors in poultry is complicated due to multiple etiological agents capable of causing very similar tumors. It is not uncommon that more than one avian tumor virus can be present in a chicken, thus one must consider both the diagnosis of the disease/tumors (pathological
291:
in a previously uninfected or unvaccinated flock, causing depression, paralysis, and death in a large number of birds (up to 80%). The age of onset is much earlier than the classic form; birds are four to eight weeks old when affected. Infiltration into multiple organs/tissue is
442:
Before the development of the vaccine for Marek's disease, Marek's disease caused substantial revenue loss in the poultry industries of the United States and the United
Kingdom. The vaccine can be administered to one-day-old chicks through subcutaneous inoculation or by
467:
to the point that any chicken that is unvaccinated will die if infected. Other leaky vaccines are commonly used in agriculture. One vaccine in particular is the vaccine for avian influenza. Leaky vaccine use for avian influenza can select for virulent strains.
358:
inflammatory lymphocytes. Peripheral neuropathy should also be considered as a principal rule-out in young chickens with paralysis and nerve enlargement without visceral tumors, especially in nerves with interneuronal edema and infiltration of plasma cells.
276:
may occur. Besides lesions in the peripheral nerves, there are frequently lymphomatous infiltration/tumours in the skin, skeletal muscle, visceral organs. Organs that are commonly affected include the ovary, spleen, liver, kidneys, lungs, heart,
324:
is impairment of the T-lymphocytes resulting from Marek's disease, preventing a competent immunological response against pathogenic challenge, with the affected birds become more susceptible to disease conditions such as coccidiosis and
430:
when chickens are infected with the virus. However, administration of the vaccine does not prevent an infected bird from shedding the virus, though it does reduce the amount of virus shed in the dander, hence reducing
415:
deworming and vitamin supplements can also help keep infected flocks healthier. Reducing stress is also a key component, as stress will often bring about illness in birds infected with Marek's disease.
807:
640:"Immunosuppressive effects of Marek's disease virus (MDV) and herpesvirus of turkeys (HVT) in broiler chickens and the protective effect of HVT vaccination against MDV challenge"
365:
Key clinical signs as well as gross and microscopic features that are most useful for differentiating Marek's disease from lymphoid leukosis and reticuloendotheliosis include:
408:
PCR blood testing can also detect Marek's disease, and proper testing can differentiate between a vaccinated bird with antibodies and a true positive for Marek's disease.
229:
for a few weeks. After infection, microscopic lesions are present after one to two weeks, and gross lesions are present after three to four weeks. The virus is spread in
772:
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vaccination is the preferred method, as it does not require handling of the chicks and can be done rapidly by automated methods. Immunity develops within two weeks.
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2140:
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Witter RL, Gimeno IM, Pandiri AR, Fadly AM (July 2010). "Tumor diagnosis manual: the differential diagnosis of lymphoid and myeloid tumors in the chicken".
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218:. Viruses related to MDV appear to be benign and can be used as vaccine strains to prevent Marek's disease. For example, the related herpesvirus found in
405:(OIE) reference laboratory for Marek's disease is Avian Viral Oncogenesis group (led by Professor Venugopal Nair OBE) at The Pirbright Institute, UK.
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diagnosis) and of the virus (etiological diagnosis). A step-wise process has been proposed for diagnosis of Marek's disease, which includes:
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infection. Furthermore, without stimulation by cell-mediated immunity, the humoral immunity conferred by the B-cell lines from the
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222:(HVT), causes no apparent disease in the birds, and continues to be used as a vaccine strain for prevention of Marek's disease.
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Read AF, Baigent SJ, Powers C, Kgosana LB, Blackwell L, Smith LP, Kennedy DA, Walkden-Brown SW, Nair VK (July 2015).
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Birds infected with GaHV-2 can be carriers and shedders of the virus for life. Newborn chicks are protected by
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Current Topics in
Microbiology and Immunology: Marek's Disease (Current Topics in Microbiology and Immunology)
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Six syndromes are known to occur after infection with Marek's disease. These syndromes may overlap.
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708:"Characterization and experimental reproduction of peripheral neuropathy in White Leghorn chickens"
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Islam AF, Wong CW, Walkden-Brown SW, Colditz IG, Arzey KE, Groves PJ (October 2002).
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191:, a Hungarian veterinarian who described it in 1907. Marek's disease is caused by an
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1965:
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599:"Atherosclerosis induced by infection with Marek's disease herpesvirus in chickens"
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834:"Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens"
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Age: Marek's disease can affect birds at any age, including <16 weeks of age;
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vaccination when the eggs are transferred from the incubator to the hatcher.
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also shuts down, thus resulting in birds that are totally immunocompromised.
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Left — normal chicken eye; Right — Eye of a chicken with Marek's disease.
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Fenner FJ, Gibbs EP, Murphy FA, Rott R, Studdert MJ, White DO (1993).
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Marek's disease is not treatable, however, supportive care can help.
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History, epidemiology, clinical observations and gross necropsy;
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2162:
950:
808:"Leaky Vaccines Enhance Spread of Deadlier Chicken Viruses"
2158:
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of the more virulent strains is increased by the vaccine.
199:(GaHV-2). The disease is characterized by the presence of
909:"'Leaky' Vaccines May Fuel Evolution of Deadlier Viruses"
398:
infections, and serology to confirm/exclude infections.
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is the only known method to prevent the development of
16:
Highly contagious viral neoplastic disease in chickens
884:"This chicken vaccine makes its virus more dangerous"
497:
International
Committee on Taxonomy of Viruses (ICTV)
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Lymphoid proliferation in skin and feather follicles;
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involvement, difficulty breathing or dilation of the
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Pleomorphic lymphoid cells in nerves and tumors; and
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causes round, firm lesions at the feather follicles.
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519:"ICTV Taxonomy history: Gallid alphaherpesvirus 2"
381:Interfollicular tumors in the bursa of Fabricius;
372:Clinical signs: Frequent wing and leg paralysis;
318:is induced in experimentally infected chickens.
706:Bacon LD, Witter RL, Silva RF (October 2001).
2174:
2139:species listed below parent taxon –– Source:
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2349:European Union Council Directive 1999/74/EC
597:Fabricant CG, Fabricant J (November 1999).
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689:American Association of Avian Pathologists
195:known as "Marek's disease virus" (MDV) or
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859:
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614:
435:of the disease. Marek's disease does not
375:Incidence: >5% in unvaccinated flocks;
567:
565:
563:
537:
535:
490:to incorporate a subfamily designation"
476:
350:Characteristics of the tumor cell, and;
298:causes lymphocyte infiltration of the
7:
781:World Organisation for Animal Health
770:"Reference Experts and Laboratories"
403:World Organisation for Animal Health
484:Davison, Andrew (27 January 2016).
2415:Avian infectious laryngotracheitis
14:
2430:Histomoniasis (blackhead disease)
747:"Chapter 2.3.13. Marek’s Disease"
2475:Fatty liver hemorrhagic syndrome
2144:
33:
2344:Abnormal behaviour in captivity
237:and transmitted by inhalation.
486:"Rename species in the family
1:
616:10.1016/S0002-8703(99)70276-0
574:Veterinary Virology (2nd ed.)
302:(making the iris turn grey),
2425:Avian sarcoma leukosis virus
851:10.1371/journal.pbio.1002198
810:. 2015-07-27. Archived from
378:Potential nerve enlargement;
938:Marek's Disease Information
758:OIE Terrestrial Manual 2010
657:10.1080/0307945021000005824
353:Virological characteristics
268:of one or more limbs. With
206:as well as infiltration of
2747:
304:unequal size of the pupils
2651:Gallid alphaherpesvirus 2
2612:Gallid alphaherpesvirus 2
2497:Infectious bursal disease
2486:Gallid alphaherpesvirus 3
2134:
1091:
1032:
987:
725:10.1080/03079450120078680
310:Cutaneous Marek's disease
258:Classical Marek's disease
197:Gallid alphaherpesvirus 2
160:
153:
146:Gallid alphaherpesvirus 2
28:
23:Gallid alphaherpesvirus 2
21:
2261:List of poultry feathers
2552:Tibial dyschondroplasia
2547:Squamous cell carcinoma
2256:List of chicken colours
576:. Academic Press, Inc.
176:is a highly contagious
783:, Retrieved 2018-12-13
760:, Retrieved 2012-08-03
603:American Heart Journal
250:
2721:Animal viral diseases
542:Hirai K, ed. (2001).
285:Acute Marek's disease
248:
2582:Gallid herpesvirus 2
2460:Dermanyssus gallinae
940:at poultrykeeper.com
546:. Springer: Berlin.
296:Ocular lymphomatosis
187:. It is named after
164:Gallid herpesvirus 2
30:Virus classification
1024:Malacoherpesviridae
794:"Viral Oncogenesis"
227:maternal antibodies
2440:Campylobacteriosis
814:on October 6, 2018
775:2012-07-16 at the
752:2013-06-10 at the
609:(5 Pt 2): S465–8.
331:Bursa of Fabricius
264:causes asymmetric
262:neurolymphomatosis
251:
121:Orthoherpesviridae
2703:
2702:
2574:Taxon identifiers
2565:
2564:
2522:Newcastle disease
2502:Infectious coryza
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1846:Lymphocryptovirus
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1083:Alloherpesviridae
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989:Higher taxonomy:
583:978-0-12-253056-2
553:978-3-540-67798-7
437:spread vertically
433:horizontal spread
393:T-cell lymphomas.
322:Immunosuppression
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384:CNS involvement;
327:Escherichia coli
306:, and blindness.
193:alphaherpesvirus
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2420:Avian influenza
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1655:Muromegalovirus
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1585:Cytomegalovirus
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844:(7): e1002198.
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796:. 23 July 2014.
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777:Wayback Machine
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1460:Varicellovirus
1455:
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1010:Herviviricetes
998:Heunggongvirae
988:
985:
984:
976:
974:
973:
966:
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951:
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932:External links
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1685:Proboscivirus
1681:
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1231:Herpesviridae
1227:
1213:
1210:
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1205:
1203:
1200:
1199:
1197:
1195:
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1189:
1183:
1180:
1178:
1175:
1173:
1170:
1169:
1167:
1165:
1164:
1163:Ictalurivirus
1159:
1153:
1150:
1148:
1145:
1143:
1140:
1138:
1135:
1134:
1132:
1130:
1129:
1124:
1118:
1115:
1113:
1110:
1108:
1105:
1104:
1102:
1100:
1099:
1098:Batrachovirus
1094:
1090:
1087:
1085:
1084:
1079:
1064:
1063:
1061:
1059:
1058:
1053:
1046:
1045:
1043:
1041:
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1035:
1031:
1028:
1026:
1025:
1020:
1016:
1015:Herpesvirales
1012:
1011:
1006:
1005:
1004:Peploviricota
1000:
999:
994:
993:
992:Duplodnaviria
986:
982:
981:
980:Herpesvirales
972:
967:
965:
960:
958:
953:
952:
949:
945:
939:
936:
935:
931:
916:
915:
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904:
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867:
862:
857:
852:
847:
843:
839:
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828:
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813:
809:
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800:
795:
789:
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782:
778:
774:
771:
766:
763:
759:
755:
751:
748:
743:
740:
735:
731:
726:
721:
718:(5): 487–99.
717:
713:
709:
702:
699:
694:
690:
683:
680:
675:
671:
667:
663:
658:
653:
650:(5): 449–61.
649:
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634:
631:
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622:
617:
612:
608:
604:
600:
593:
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579:
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488:Herpesviridae
480:
477:
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311:
308:
305:
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297:
294:
290:
286:
283:
281:and adrenals.
280:
275:
271:
267:
263:
259:
256:
255:
254:
247:
240:
238:
236:
233:from feather
232:
228:
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217:
213:
209:
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198:
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175:
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139:
138:
135:
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130:
127:
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122:
118:
115:
114:
111:
110:
109:Herpesvirales
106:
103:
102:
99:
98:
94:
91:
90:
87:
86:
85:Peploviricota
82:
79:
78:
75:
74:
70:
67:
66:
63:
62:
61:Duplodnaviria
58:
55:
52:
51:
48:
45:
42:
41:
36:
31:
27:
24:
20:
2650:
2581:
2511:
2484:
2392:Rooster Flag
2377:Cockfighting
2329:Chick sexing
2279:Battery cage
2054:Rhadinovirus
2052:
2034:
1989:
1966:Manticavirus
1964:
1904:
1844:
1826:
1792:
1745:Roseolovirus
1743:
1713:
1683:
1653:
1583:
1572:
1458:
1370:Simplexvirus
1368:
1343:
1298:
1273:
1251:
1229:
1193:Salmonivirus
1191:
1161:
1128:Cyprinivirus
1126:
1096:
1081:
1055:
1037:
1022:
1014:
1008:
1002:
996:
990:
978:
943:
918:. Retrieved
914:Live Science
912:
903:
892:. Retrieved
890:. 2015-07-27
888:PBS NewsHour
887:
878:
841:
838:PLOS Biology
837:
827:
816:. Retrieved
812:the original
802:
788:
780:
765:
757:
742:
715:
711:
701:
692:
688:
682:
647:
643:
633:
606:
602:
592:
573:
543:
522:. Retrieved
513:
501:. Retrieved
496:
487:
479:
465:
457:
453:
448:
444:
441:
422:
413:
410:
407:
400:
396:
364:
360:
356:
341:
326:
321:
315:
309:
295:
284:
261:
257:
252:
224:
196:
189:József Marek
173:
172:
163:
145:
144:
132:
120:
108:
96:
84:
72:
60:
53:
43:(unranked):
22:
2606:Wikispecies
2532:Psittacosis
2517:Mycoplasmas
2465:Egg binding
2450:Coccidiosis
2445:Candidiasis
2248:Terminology
2150:Wikispecies
2036:Patagivirus
1057:Ostreavirus
524:16 November
499:. p. 2
424:Vaccination
270:vagus nerve
216:lymphocytes
183:disease in
2710:Categories
2527:Omphalitis
2470:Erysipelas
2372:Cockatrice
2284:Free range
2198:As poultry
2137:Unassigned
1991:Percavirus
1828:Bossavirus
1345:Scutavirus
1300:Mardivirus
920:2018-11-03
894:2021-07-26
818:2018-11-03
471:References
419:Prevention
181:neoplastic
133:Mardivirus
2666:Q24808654
2542:Scaly leg
2387:Sarimanok
2271:Husbandry
1906:Macavirus
1715:Quwivirus
1275:Iltovirus
1039:Aurivirus
338:Diagnosis
292:observed.
266:paralysis
241:Syndromes
235:follicles
140:Species:
68:Kingdom:
2660:Wikidata
2626:11459840
2591:Wikidata
2537:Pullorum
2492:Gapeworm
2435:Botulism
2402:Diseases
2382:Kapparos
2339:Candling
2324:Hatchery
2228:Poularde
1729:MschBHV1
870:26214839
773:Archived
750:Archived
734:19184938
674:36320339
666:12427339
625:10539849
289:epidemic
204:lymphoma
185:chickens
155:Synonyms
116:Family:
80:Phylum:
2597:Q707619
2507:Malaria
2480:Fowlpox
2367:As pets
2359:Culture
2294:Yarding
2238:Broiler
2233:Poussin
2206:As food
2190:Chicken
2015:MusHV-1
1975:PhaHV-1
1860:CeHV-14
1855:CalHV-3
1334:SpAHV-1
1202:SalHV-1
1172:AciHV-2
1137:AngHV-1
861:4516275
695:: 1–84.
461:fitness
220:turkeys
128:Genus:
104:Order:
92:Class:
2218:Breeds
2211:Dishes
2118:SaHV-2
2108:MuHV-4
2088:McHV-5
2078:CrHV-2
2073:BoHV-4
2063:AtHV-2
2044:VeHV-3
2025:VeHV-1
2020:PhHV-3
2010:FeHV-1
1980:VoHV-1
1945:SuHV-3
1940:OvHV-2
1935:HiHV-1
1930:CpHV-2
1925:BoHV-6
1915:AlHV-1
1895:PoHV-2
1890:PaHV-1
1885:PnHV-1
1875:McHV-4
1865:GoHV-1
1836:DeHV-1
1815:SgHV-1
1809:PhHV-2
1779:SuHV-2
1774:MuHV-3
1769:McHV-9
1754:HHV-6A
1734:TuHV-1
1724:CaHV-2
1694:ElHV-1
1664:MuHV-1
1644:SaHV-4
1634:PaHV-3
1629:PnHV-2
1624:MnHV-1
1614:McHV-3
1604:CeHV-5
1599:CbHV-1
1594:AoHV-1
1559:SuHV-1
1554:PhHV-1
1549:MoHV-1
1539:FeHV-1
1499:CvHV-1
1494:CeHV-9
1489:CpHV-1
1484:CaHV-1
1479:BuHV-1
1469:BoHV-1
1449:SaHV-1
1444:PtHV-1
1439:PaHV-2
1434:PnHV-3
1424:MaHV-1
1409:McHV-1
1404:LeHV-4
1389:CeHV-2
1384:BoHV-2
1379:AtHV-1
1359:TeHV-3
1354:ChHV-5
1329:MeHV-1
1319:GaHV-2
1314:CoHV-1
1309:AnHV-1
1289:PsHV-1
1284:GaHV-1
1262:ChHV-6
1240:IgHV-2
1177:IcHV-1
1142:CyHV-1
1107:RaHV-1
1065:OsHV-1
1047:AbHV-1
868:
858:
732:
672:
664:
623:
580:
550:
449:In ovo
445:in ovo
428:tumors
287:is an
231:dander
212:organs
208:nerves
201:T cell
2693:10390
2680:6JXG7
2639:76375
2621:IRMNG
2455:Colds
2223:Capon
2083:HHV-8
2000:EHV-2
1870:HHV-4
1803:EHV-7
1609:HHV-5
1544:HHV-3
1514:EHV-1
1394:HHV-1
1013:>
1007:>
1001:>
995:>
670:S2CID
503:7 May
493:(PDF)
178:viral
54:Realm
47:Virus
2688:NCBI
2141:ICTV
866:PMID
730:PMID
662:PMID
621:PMID
578:ISBN
548:ISBN
526:2017
505:2019
401:The
300:iris
274:crop
210:and
2675:CoL
2634:ISC
2143:––
856:PMC
846:doi
720:doi
652:doi
611:doi
607:138
260:or
214:by
2712::
2690::
2677::
2662::
2636::
2623::
2608::
2593::
2103:12
2098:11
1880:10
1759:6B
911:.
886:.
864:.
854:.
842:13
840:.
836:.
779:,
756:,
728:.
716:30
714:.
710:.
691:.
668:.
660:.
648:31
646:.
642:.
619:.
605:.
601:.
562:^
534:^
495:.
439:.
56::
2182:e
2175:t
2168:v
2113:7
2093:8
2068:3
2005:5
1955:5
1950:4
1920:2
1794:γ
1764:7
1704:5
1699:4
1674:8
1669:2
1639:4
1619:8
1574:β
1534:9
1529:8
1524:4
1519:3
1509:3
1504:2
1474:5
1429:2
1419:3
1414:2
1399:2
1324:3
1253:α
1212:3
1207:2
1182:2
1152:3
1147:2
1117:3
1112:2
970:e
963:t
956:v
923:.
897:.
872:.
848::
821:.
736:.
722::
693:1
676:.
654::
627:.
613::
586:.
556:.
528:.
507:.
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