Extraneous reticuloendotheliosis virus (REV)

Test code: S0266 - Ultrasensitive qualitative detection of extraneous reticuloendotheliosis virus by reverse transcription coupled real time polymerase chain reaction

Reticuloendotheliosis (RE) refers to a group of pathologic syndromes caused by the reticuloendotheliosis virus (REV), a member of the Retroviridae family, specifically the Gammaretrovirus genus. REV is genetically and immunologically distinct from other avian retroviruses such as avian leukosis/sarcoma virus (ALSV), showing closer similarity to mammalian retroviruses such as murine leukemia virus (MLV). REV affects a wide range of avian species, including chickens, turkeys, ducks, geese, quail, pheasants, and others, causing significant economic losses in the poultry industry due to its immunosuppressive and oncogenic effects.

REV is associated with three main disease syndromes: runting disease syndrome, chronic neoplastic disease, and acute reticulum cell neoplasia. Runting disease syndrome is characterized by growth retardation, weight loss, and abnormal feather development (eg "naked neck" or "helicopter feathers"). This syndrome is often seen in young birds (4–10 weeks old), especially after exposure to contaminated vaccines. Chronic neoplastic disease involves B-cell and T-cell lymphomas, which can resemble lymphoid leukosis (caused by ALSV) or Marek’s disease (caused by a herpesvirus). Development of chronic neoplastic disease usually takes a long latency period - typically >4 months. Acute reticulum cell neoplasia refers to a rapidly progressing tumor formation, often involving T-cells, and is seen in chickens, turkeys, ducks, and quail. Symptoms occur 6–8 weeks post-infection and can be confused with Marek’s disease due to similar pathology.

The most significant impact of this viral infection is immunosuppression. REV induces a transient but severe immunosuppressive state, impairing T-cell proliferation and increasing susceptibility to other infections. Such effects can lead to vaccination failures, exacerbating economic impacts.

REV can also integrate its genetic material into the genomes of large DNA viruses, such as fowlpox virus (FWPV) and Marek’s disease virus (MDV), creating recombinant pathogens. This complicates diagnosis and control, as these chimeric viruses can spread naturally in poultry and wild birds.

REV is transmitted through multiple routes. Horizontal transmission is primarily through fecal-oral routes, contact between birds, or via contaminated litter. Mosquitoes and other blood-sucking insects are suspected vectors. The virus can also pass from hen to progeny. Accidental contamination of live poultry vaccines (eg Marek’s disease, fowlpox, Newcastle disease, or infectious bronchitis vaccines) has caused significant outbreaks (Woźniakowski et al., 2015). Germline transmission is rare but has been reported, where REV integrates into the host genome and is passed to offspring.

Diagnosing REV is challenging due to its similarity to Marek’s disease and avian leukosis. Furthermore, REV causes immunosuppression of infected animals so that serology detection of antibodies may not be suitable. Molecular detection by polymerase chain reaction (PCR) has high specificity and sensitivity and is useful to confirm the diagnosis (Li et al., 2012).

Utilities:

• Help confirm the disease causing agent
• Environmental monitoring
• Help ensure that bird populations are free of extraneous reticulendotheliosis virus
• Early prevention of spread of this virus among bird populations
• Minimize human exposure to this virus
• Safety monitoring of biological products and vaccines that derive from birds

References:
Li, K., Gao, H., Gao, L., Qi, X., Qin, L., Gao, Y., Xu, Y. and Wang, X. (2012) Development of TaqMan real-time PCR assay for detection and quantitation of reticuloendotheliosis virus. J. Virol. Methods. 179:402-408.

Woźniakowski, G., Mamczur, A. and Samorek-Salamonowicz, E. (2015) Common occurrence of Gallid herpesvirus-2 with reticuloendotheliosis virus in chickens caused by possible contamination of vaccine stocks. J. Appl. Microbiol. 118:803-808.

Specimen requirements: 0.2 ml feces, or cloacal swab, or 0.2 ml whole blood in EDTA (purple top) tube, or 0.2 ml fresh or frozen tissue, or 0.2 ml cell culture.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative reverse transcription coupled real time PCR

Normal range: Nondetected