Marek's disease in Japanese quail -- a pathological, virological and serological study

Marek's Disease in a Flock of Japanese Quails (Coturnix japonica) in Germany

A case of increased mortality was investigated at a German farm housing Japanese quails (Coturnix japonica) for egg production. Different age groups were kept in aviaries in one barn. The quail chicks had diarrhea and the adults were emaciated, some also with diarrhea and conjunctivitis. Postmortem examination showed gross tumorlike lesions in 7 of 15 adult quails examined, with ocular lesions in 2 of them. On histopathological examination, infiltrates of monomorphic round cells were found in liver, spleen, lung, and proventriculus. In the eyes of two quails, similar cells were infiltrating the choroid layer, limbus, and adjacent parts of the cornea. Malignant lymphoma was diagnosed. Immunohistochemical examination identified tumor cells as T cells, and Mardivirus gallidalpha 2-specific PCR was positive for five quails with gross lesions. Additionally, Proteus mirabilis and Klebsiella pneumoniae were detected in the chicks and Clostridium spp. and coccidia in the adults. Marek's EcoQ protein (Meq) gene from Mardivirus gallidalpha 2 was sequenced and analyzed, confirming Marek's disease. The results of our examinations demonstrate that the ocular lesions were caused by Marek's disease and that the Meq gene from Mardivirus gallidalpha 2 was detected in the flock of quails. As a control strategy for Marek's disease in quails, an all-in/all-out system was introduced. Additional laying quails acquired from a breeder at 35 days of life were vaccinated at stabling with a combined turkey herpesvirus (HVT)-Rispens vaccine and 14 days later with a Rispens vaccine. Subsequently, the losses and laying rates returned to normal.

Sex Differences in Response to Marek's Disease: Mapping Quantitative Trait Loci Regions (QTLRs) to the Z Chromosome

Marek's Disease (MD) has a significant impact on both the global poultry economy and animal welfare. The disease pathology can include neurological damage and tumour formation. Sexual dimorphism in immunity and known higher susceptibility of females to MD makes the chicken Z chromosome (GGZ) a particularly attractive target to study the chicken MD response. Previously, we used a Hy-Line F₆ population from a full-sib advanced intercross line to map MD QTL regions (QTLRs) on all chicken autosomes. Here, we mapped MD QTLRs on GGZ in the previously utilized F₆ population with individual genotypes and phenotypes, and in eight elite commercial egg production lines with daughter-tested sires and selective DNA pooling (SDP). Four MD QTLRs were found from each analysis. Some of these QTLRs overlap regions from previous reports. All QTLRs were tested by individuals from the same eight lines used in the SDP and genotyped with markers located within and around the QTLRs. All QTLRs were confirmed. The results exemplify the complexity of MD resistance in chickens and the complex distribution of p-values and Linkage Disequilibrium (LD) pattern and their effect on localization of the causative elements. Considering the fragments and interdigitated LD blocks while using LD to aid localization of causative elements, one must look beyond the non-significant markers, for possible distant markers and blocks in high LD with the significant block. The QTLRs found here may explain at least part of the gender differences in MD tolerance, and provide targets for mitigating the effects of MD.

Mapping QTL Associated with Resistance to Avian Oncogenic Marek's Disease Virus (MDV) Reveals Major Candidate Genes and Variants

Marek’s disease (MD) represents a significant global economic and animal welfare issue. Marek’s disease virus (MDV) is a highly contagious oncogenic and highly immune-suppressive α-herpes virus, which infects chickens, causing neurological effects and tumour formation. Though partially controlled by vaccination, MD continues to have a profound impact on animal health and on the poultry industry. Genetic selection provides an alternative and complementary method to vaccination. However, even after years of study, the genetic mechanisms underlying resistance to MDV remain poorly understood. The Major Histocompatability Complex (MHC) is known to play a role in disease resistance, along with a handful of other non-MHC genes. In this study, one of the largest to date, we used a multi-facetted approach to identify quantitative trait locus regions (QTLR) influencing resistance to MDV, including an F₆ population from a full-sib advanced intercross line (FSIL) between two elite commercial layer lines differing in resistance to MDV, RNA-seq information from virus challenged chicks, and genome wide association study (GWAS) from multiple commercial lines. Candidate genomic elements residing in the QTLR were further tested for association with offspring mortality in the face of MDV challenge in eight pure lines of elite egg-layer birds. Thirty-eight QTLR were found on 19 chicken chromosomes. Candidate genes, microRNAs, long non-coding RNAs and potentially functional mutations were identified in these regions. Association tests were carried out in 26 of the QTLR, using eight pure lines of elite egg-layer birds. Numerous candidate genomic elements were strongly associated with MD resistance. Genomic regions significantly associated with resistance to MDV were mapped and candidate genes identified. Various QTLR elements were shown to have a strong genetic association with resistance. These results provide a large number of significant targets for mitigating the effects of MDV infection on both poultry health and the economy, whether by means of selective breeding, improved vaccine design, or gene-editing technologies.

Role of Marek's disease herpesvirus in the induction of tumours in Japanese quail (Coturnix coturnix japonica) by methylcholanthrene

The QT35 cell line, established from 20-methylcholanthrene (MCA)-induced tumours in Japanese quail, is positive for Marek's disease virus (MDV), and therefore we examined whether MDV is important for the development of MCA-induced tumours. Japanese quail were inoculated with the JM16 strain of MDV at 1 or 3 days of age or left uninoculated. At 3 weeks of age, quail were injected in the breast muscle with 4 mg MCA in corn oil or corn oil alone. Quail were observed for tumours three times/week and at post mortem at 11 to 12 weeks of age. MDV DNA was detected by polymerase chain reaction (PCR) in spleens of 14/20 birds inoculated with JM16+corn oil and of 53/71 birds inoculated with JM16+MCA. Interestingly, 1/74 quail was positive in the MCA group alone for MDV DNA. Tumours were collected for histopathology, cell line development, and PCR and reverse transcriptase-PCR for the presence of MDV. Tumours developed in 38/83 MCA-treated and 32/85 JM16+MCA-treated quail. Fibrosarcomas without metastasis were the only tumours observed in the MCA-treated quail, while quail treated with JM16 and MCA developed undifferentiated tumours, fibrosarcomas, lymphosarcomas or combinations with or without metastasis. One out of 20 quail receiving JM16 alone developed a lymphosarcoma. Cell line development was not influenced by JM16. Tumours from MCA-treated quail were negative for MDV, while 19/29 were positive in the JM16+MCA group. MDV transcripts were present in 13/18 tumours examined in the JM16+MCA group. In conclusion, MDV did not affect tumour development but did influence tumour aggression and histological type.

Isolation of Marek's disease virus from Japanese quail with lymphoproliferative disease

Sixty-one Japanese quail from eight flocks with problems of recurring outbreaks of lymphoproliferative diseases resembling Marek's disease (MD), were examined aetiologically. Gross lymphomatous lesions were seen in 17 of the quail and 11 out of 56 quail had MD virus (MDV) feather tips antigens. MDV antibody was detectable in only one of 22 quail. None of 9 quail had antibodies against reticuloendotheliosis virus (REV). No MDV was isolated from the total 42 materials of quail using cell culture technique. No REV and avian leukosis virus (ALV) were isolated from some of them. However, specific-pathogen-free chicks inoculated with the blood materials revealed MD. and four MDVs were recovered from them. The isolates proved free from REV and ALV. The isolates were placed into serotype 1 by the indirect immunofluorescent antibody test. These results indicate that MDV is aetiologically involved in the present outbreaks of lymphoproliferative disease in Japanese quail.

Marek's disease, candidiasis and megabacteriosis in a flock of chickens (Gallus gallus domesticus ) and Japanese quail (Coturnix japonka )

An outbreak of mortality in chickens and Japanese quail sharing the same airspace was investigated. Marek's disease was diagnosed in five of 11 chickens examined, and in 20 of 24 quail; crop candidiasis was found in four of the chickens and in five of the quail, and moderate to large numbers of organisms referred to as megabacteria were observed in eight of the chickens and 16 of the quail. The disease was so severe that almost all of the quail in the flock died or were culled during the following six months. In contrast, only approximately 5 per cent of the chickens died from Marek's disease.

Transactivation of latent Marek's disease herpesvirus genes in QT35, a quail fibroblast cell line, by herpesvirus of turkeys

The QT35 cell line was established from a methylcholanthrene-induced tumor in Japanese quail (Coturnix coturnix japonica) (C. Moscovici, M. G. Moscovici, H. Jimenez, M. M. Lai, M. J. Hayman, and P. K. Vogt, Cell 11:95-103, 1977). Two independently maintained sublines of QT35 were found to be positive for Marek's disease virus (MDV)-like genes by Southern blotting and PCR assays. Sequence analysis of fragments of the ICP4, ICP22, ICP27, VP16, meq, pp14, pp38, open reading frame (ORF) L1, and glycoprotein B (gB) genes showed a strong homology with the corresponding fragments of MDV genes. Subsequently, a serotype 1 MDV-like herpesvirus, tentatively name QMDV, was rescued from QT35 cells in chicken kidney cell (CKC) cultures established from 6- to 9-day-old chicks inoculated at 8 days of embryonation with QT35 cells. Transmission electron microscopy failed to show herpesvirus particles in QT35 cells, but typical intranuclear herpesvirus particles were detected in CKCs. Reverse transcription-PCR analysis showed that the following QMDV transcripts were present in QT35 cells: sense and antisense meq, ORF L1, ICP4, and latency-associated transcripts, which are antisense to ICP4. A transcript of approximately 4.5 kb was detected by Northern blotting using total RNA from QT35 cells. Inoculation of QT35 cells with herpesvirus of turkeys (HVT)-infected chicken embryo fibroblasts (CEF) but not with uninfected CEF resulted in the activation of ICP22, ICP27, VP16, pp38, and gB. In addition, the level of ICP4 mRNA was increased compared to that in QT35 cells. The activation by HVT resulted in the production of pp38 protein. It was not possible to detect if the other activated genes were translated due to the lack of serotype 1-specific monoclonal antibodies.