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Reticuloendotheliosis (RE) refers to a variety of conditions caused by retroviruses of the reticuloendotheliosis virus (REV) group. The various syndromes include runting disease syndrome, chronic lymphoid neoplastic syndrome and acute reticulum cell neoplasia. Chickens infected with REV suffer from the chronic neoplastic form of the disease.

In the United States, REV infection is detected in a significant proportion of commercial layer, broiler, and turkey flocks. No vaccines are used against REV infection and no genetic resistance to infection has been recognized.


REVs are transmitted horizontally through fecal-oral route, vertically, and accidentally through contaminated vaccines.

Clinical Signs

Weight loss
Pale comb and wattle
Occasional paralysis
Abnormal feathering


  • History
  • Clinical signs
  • Lab tests
  • Necropsy

Reported Cases

  • Case 1: Reticuloendotheliosis in a Partridges A large commercial flock of Hungarian partridge experienced elevated mortality associated with a wasting disease in May 1998. Postmortem examination of females consistently revealed a distended crop and abnormal gray-white tissue infiltrating the wall of the crop and thoracic esophagus. Neoplasia in male partridge was observed in the liver. Microscopic examination of the crop and thoracic esophagus revealed transmural masses of immature lymphocytes with frequent mitotic figures. Similar cells were observed in the liver of affected males. Virus particles consistent in size and morphology with reticuloendotheliosis virions were observed in neoplastic lymphoid cells via electron microscopy. Reticuloendotheliosis virus was isolated from each of four blood samples. Ref

  • Case 2: Visceral lymphomas in a Chickens Visceral lymphomas occurred in a 236-day-old layer flock previously diagnosed with reticuloendotheliosis virus (REV)-integrated fowlpox virus (FPV) infection at the age of 77 days. Common pathologic lesions were multiple neoplastic nodules of homogeneous lymphocytes in the livers and spleens of all submitted chickens. All neoplastic tissues were positive for the REV envelope (env) gene by PCR. In a retrospective molecular study of FPV-infected 77-day-old chickens from the same flock, we identified nearly full-length REV provirus integrated into the genome of FPV as well as the REV env gene in trachea samples, whereas only the REV LTR region was present in the FPV strain used to vaccinate this flock. The 622-bp REV env gene nucleotide sequence derived from the trachea and neoplastic tissues was identical. Commercial ELISA of serum samples revealed that all chickens aged between 17 and 263 days in this flock were positive for REV but not for avian leukosis virus. Taken together, the evidence suggests that the visceral lymphomas were caused by a REV-integrated FPV field strain. FPV infections of commercial chickens should be followed up by careful monitoring for manifestations of REV infection, including lymphomas and immune depression, considering the ease with which the REV provirus appears to be able to integrate into the FPV genome. Ref


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Provide additional vitamins and probiotics. Limit stress. Call your veterinarian.
Thymulin 5cHDiluted into drinking waterSato C et al., 2012



Scientific References