Tumors Associated with Avian Leukosis Virus Subgroup J in Layer Hens during 2007 to 2009 in China

Abstract

ABSTRACT. In the 3 years leading up to November 2009, 6 different types of naturally occurring neoplasms associated with avian leukosis virus subgroup J (ALV-J) were diagnosed by histopathology, polymerase chain reaction (PCR) and immunohistochemistry (IHC) in 140 layer hens out of approximately 100,000. The most prevalent tumor type was hemangioma (50%) in commercial layer flocks; the second most prevalent neoplasm type was myelocytoma (38.6%); a small number of ALV-J positive lymphomas (4.3%) that were not associated with Marek's disease (MD) or lymphoid leukosis (LL) was observed. Histiocytic sarcomas (2.1%) were found mainly in the spleen, liver and kidney. Fibrosarcomas (2.8%) presented as metastatic thigh, liver, lung and kidney neoplasms. Three cases of intestinal adenocarcinoma (2.1%) were found associated with ALV-J. Chickens with multiple tumors were a common phenomenon. Usually, hemangiomas plus myelocytomas (8.6%), myelocytomas plus histiocytic sarcomas (2.1%), hemangioma plus myelocytoma and lymphoma (3.6%) were found in various viscera organs. The present report describes the occurrence of multiple neoplasms associated with ALV-J in field layer hens.KEY WORDS: avian leukosis virus subgroup J (ALV-J), layer chickens, multiple neoplasms.J. Vet. Med. Sci. 72(8): 1027-1033, 2010 Avian leukosis virus subgroup J (ALV-J), first described in the United Kingdom in 1991 and later in other countries, has been associated primarily with myeloid leukosis in meat-type chickens [8,[11][12][13][14][15]. ALV-J has caused severe economic losses in broiler breeders throughout the world. Vertical transmission from broiler breeders to progeny is more frequent with ALV-J than with other ALV subgroups [25].ALV-J in the field has occurred almost entirely in meattype chickens several years ago. Layers have rarely become infected, but experimental studies with Rous sarcoma virus having the inserted envelope gene of ALV-J by Payne [16] have shown that both layers and turkeys are susceptible to ALV-J infection, while other poultry and game birds appear to be resistant.The frequencies of different tumor types seen by Payne [11] during 1996-1998 from suspect ALV-J infected flocks were 58% for myeloid leukosis (ML), 12% for histiocytic sarcoma (HS), 9% for erythroblastosis and 5% for blast cell tumors. Numerous birds had more than one type of tumor, and some had up to four different types.In chickens, layer strains are considered to be at risk in China and their exposure to ALV-J contamination has already been demonstrated by Xu [23,24,26] and Cheng [6]. ALV-J in egg-type chickens with ML has already resulted in significant economic losses in China. Gingerich [9] also reported that a recombinant ALV containing the long terminal repeat (LTR) of the subgroup J and the envelope of subgroup B was isolated from commercial White Leghorn flocks with ML. Cheng [5] reported cases of ML diagnosed in a local Chinese breed that is commonly recognized as a dual purpose type of chicken, both for eggs and meat, in Shandong Province, P.R. China....

Molecular Epidemiology of Avian Leukosis Virus Subgroup J in Layer Flocks in China

“…Although an intact E element was not a critical requirement for the ALV-J induction of tumors, the presence of the E element could be associated with a higher frequency of tumors in susceptible chickens (8). The ALV-Js isolated from layer flocks induced a high incidence of hemangioma in China (6,36). However, previous studies indicated that the dominant tumor induced by ALV-J infection in meat-type chickens was a myelocytoma (ML) (21).…”

“…However, in China, the host range of ALV-J is changing. ALV-J has become a major problem in layer chickens since 2008 (6,14). In the present study, the analysis of sequences of ALV-J layer isolates showed that (i) the env genes of 77.8% (21/27) of the layer isolates with a high degree of genetic variation were significantly different from the env genes of the ALV-J broiler isolates, (ii) a 205-bp deletion in the 3= UTR and unique nucleotide mutations in the 3= UTR and 3= LTR were detected, and (iii) almost all layer isolates contained a complete E element of 147 to 149 residues.…”

“…However, field cases of ALV-J infection and tumors in commercial layer chickens emerged in 2004 (37). ALV-J has been found to induce various tumors and cause significant economic losses in parent and commercial layer flocks in recent years, especially from 2008 to 2010 (6,14,18,36). Many field cases of ALV-J infection and tumors occurred in 15-to 29-week-old egg-type chickens in several provinces.…”

“…Although several field cases and complete proviral genomic sequences for ALV-J strains isolated from layer chickens have been reported (6,18,36), little is known about the molecular epidemiology of ALV-J layer isolates in China. The first study conducted by our laboratory between 2007 and 2009 showed that ALV-J is predominantly responsible for layer avian leukosis in China (14).…”

Identification of avian leukosis virus subgroup J-associated acutely transforming viruses carrying the v-src oncogene in layer chickens

“…Since it was first isolated in the UK in 1991 (Payne et al, 1991), ALV-J has spread rapidly worldwide. Moreover, the pathogenicity of ALV-J has increased in China in recent years and has induced a greater diversity of tumours compared with the ALV-J prototype virus, HPRS-103, such as myeloid leukosis, haemangioma, histiocytic sarcoma, fibrosarcoma and erythroblastoma in both broilers and layers (Cheng et al, 2010;Gao et al, 2010Gao et al, , 2012Ji et al, 2012;Lai et al, 2011;Pan et al, 2011;Qu et al, 2012;Shi et al, 2011). Although a series of programmes monitoring ALV-J surveillance and control have been conducted in China, the epidemic status is still particularly serious among indigenous Chinese chicken breeds (Dong et al, 2015).…”