Detection of Reticuloendotheliosis Virus in Muscovy Ducks, Wild Turkeys, and Chickens in Brazil.

Reticuloendotheliosis viruses (REVs) are known to cause immunosuppressive and oncogenic disease that affects numerous avian species. Reticuloendotheliosis viruses are present worldwide and recently have been reported in South America with cases of infected commercial flocks in Argentina. We surveyed for the presence of REV in birds from a state in the northern region of Brazil using real-time PCR. We report here the presence of REV in Brazil, detected in Muscovy Ducks (Cairina moschata), Wild Turkeys (Meleagris gallopavo), and chickens (Gallus gallus) at a relatively high prevalence (16.8%). Phylogenetic analysis indicated a close relationship of these strains to variants in the US. This study provides evidence of REV in the Amazon biome and provides a baseline for future surveillance of the virus in the region and throughout Brazil.

Serological and molecular identification of Reticuloendotheliosis virus (REV) in chickens in Sudan.

BACKGROUND: Reticuloendotheliosis virus (REV) is a gammaretrovirus that belongs to the family of Retroviridae. The infection can result in immunosuppression, runting syndrome, high mortality, acute reticular cell neoplasia or T- and/ or B-cell lymphoma, in a variety of domestic and wild birds. The disease is widespread around the world. No related data have been reported in Sudan about the disease. The present study was conducted to determine the prevalence of REV antibodies and DNA in local and commercial breeds of chickens older than 20 weeks from June 2014 to February, 2017. METHODS: A total of 460 sera samples and 150 (50 liver and 100 spleen) tissue samples were collected from local and commercial breeds of chickens older than 20 weeks and screened for anti-REV antibodies in four states of Sudan using a commercial REV antibody ELISA test kit (IDEXX). Polymerase chain reaction (PCR) was performed to detect REV DNA in tissue samples in Khartoum State. RESULTS: The results revealed that the overall seroprevalence of REV was 74.6% among local and commercial chicken breeds, but in commercial it was 79.5% (190/239) and 69.2% in local breeds (153/221). One hundred and fifty tissue samples of chickens (50 liver, 100 spleen) were tested using PCR for detection of REV using primer sets of the conserved region in envelope glycoprotein (env) gene with a band length of 850 bp. Five out of 50 (10%) liver samples were RE provirus DNA positive detected by PCR, whereas 15 out of 100 (15%) spleen samples were PCR positive. Univariate analysis revealed there was a difference (p ≤ 0.05) between locality and breed of chickens and seropositivity to REV. CONCLUSIONS: The prevalence of the disease was high in Sudan and more studies are needed to evaluate the epidemiology and pathogenesis of the virus.

Survey of Reticuloendotheliosis Virus in Wild Turkeys (Meleagris gallopavo) in Texas, USA.

Reticuloendotheliosis virus (REV) is an immunosuppressive and sometimes oncogenic avian retrovirus that establishes lifelong infection in a wide range of avian species. REV-infected wild birds roaming near at-risk captive flocks, such as is the case for the highly endangered Attwater's Prairie Chicken (APC; Tympanuchus cupido attwateri), could act as a reservoir for viral transmission. In wild birds, prevalence rates of REV are low and appearance of associated disease is uncommon. During 2016-17, nearly half of all captive adult APC mortality at Fossil Rim Wildlife Center captive breeding facility in Glen Rose, Texas, US was attributed to REV infection. The unusually high REV prevalence rate prompted us to survey for this virus in wild galliforms throughout the region. From 2016-17, 393 blood samples collected from two subspecies of Wild Turkeys (Meleagris gallopavo) were tested for REV proviral DNA through amplification of the viral 3' long terminal repeat and segments of the viral pol gene. In REV-affected counties, 5% (5/98) of native Rio Grande Wild Turkeys (Meleagris gallopavo intermedia) were identified as REV-positive. In addition, we detected REV in one of 62 Eastern Wild Turkeys (Meleagris gallopavo silvestris) that had been imported during conservation efforts. To better determine protective measures, continued surveillance, including collection and genetic analysis of REV-infected samples, is necessary to identify sources of REV outbreaks in captive APC flocks.

An outbreak of lymphomas in a layer chicken flock previously infected with fowlpox virus containing integrated reticuloendotheliosis virus.

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.

Complete genomic sequence of a Muscovy duck-origin reticuloendotheliosis virus from China.

The complete proviral sequence of a Muscovy duck-origin reticuloendotheliosis virus (REV) associated with spontaneously occurring neoplastic disease in 2011 in Zhejiang province, China, was determined. Comparative sequence analyses indicate that the present REV is most closely related to the chicken-origin REV isolate HLJR0901 and the goose-origin isolate Goose/3410/06. These findings suggest that chickens or geese may transmit the REV to Muscovy ducks.

Occurrence of reticuloendotheliosis in Chinese partridge.

Two commercial flocks of Chinese partridge experienced increased mortality associated with a wasting disease at 120-day old in June 2006. Postmortem examination of dead chickens consistently showed visceral tissues mainly proventriculus, liver and spleen were diffuse enlargement. Microscopic examination revealed masses of immature lymphocytes with frequent mitotic figures were seen in various tissues including proventriculus, liver, spleen, kidney, heart, lung, thymus and intestine. Reticuloendotheliosis virus (REV) was isolated from each of four blood samples. Viral antigens were observed in cultured CEF (SPF embryos came from the Ji-nan poultry institute) inoculated blood samples via on indirect immunofluorescent assay. Three hundred bp fragments of LTR of REV obtained from liver samples of six chickens by PCR. This disease has not previously been reported in Chinese partridge. Chinese partridge may represent a potential reservoir of infection for other Chinese local chickens.

Serological and virological surveys of reticuloendotheliosis in chickens in Taiwan.

Reticuloendotheliosis virus (REV) is widespread in the world. No related data has been reported in Taiwan. To determine the REV infection status, antibody determination and virus isolation were performed on chickens in Taiwan. The results revealed that serological flock prevalence for the REV antibody reached 92.8% (39/42) amongst breeders (> 16 weeks old). Two different REV isolates were identified by reverse transcriptase-polymerase chain reaction, electron microscopic, immunofluorescent, and western blot assays after isolation. One of these viruses was isolated from a broiler breeder farm and the other was isolated from a Taiwan Country Chicken farm. Despite their different origins, the percent identity of the nucleotide sequences of the env gene of these two isolates was 99.7%. These two strains were similar to the FPV-UI-REV strain, featuring 99.7% and 99.8% percent identity. Indeed, REV infection would appear to be quite common amongst chickens.

Enzootic reticuloendotheliosis in the endangered Attwater's and greater prairie chickens.

Reticuloendotheliosis (RE) in captive greater prairie chickens (GPC, Tympanuchus cupido pinnatus) and Attwater's prairie chickens (APC, Tympanuchus cupido attwateri) was first reported in 1998. RE is caused by avian reticuloendotheliosis virus (REV), an oncogenic and immunosuppressive retrovirus infecting multiple species of wild and domestic birds. During August 2004 through May 2006 a captive population of prairie chickens was affected simultaneously with a neoplastic condition and also avian pox, the latter being detected in 7.4% (2 of 27) of all birds submitted for histopathology. A survey for REV was conducted in order to examine its possible role in mortality observed primarily in juvenile and adult specimens of prairie chickens. The investigative procedures included postmortem examinations, histopathology, molecular detection, and virus isolation. In total, 57 Attwater's prairie chickens and two greater prairie chickens were included in the study. REV infection was diagnosed using virus isolation or polymerase chain reaction (PCR) or both in 59.5% (28 of 47) of blood samples and/or tumors from suspect birds. Lymphosarcomas were detected in the tissues of 37% (10 of 27) of the birds submitted for histopathology. Such lymphosarcomas suggestive of RE represented the most frequent morphologic diagnosis on histopathology among 27 separate submissions of naturally dead prairie chickens. Overall, REV was detected or RE diagnosed in 34 of 59 prairie chickens (57.62%). The average death age of all birds diagnosed with lymphosarcomas on histopathology was 2.2 yr, ranging from <1 to 4 yr. Although deaths associated with neoplasia occurred in males and females in equal proportions based on submissions, overall more males were diagnosed as REV infected or RE affected (16 males vs. 7 females, and 11 birds of undetermined gender). Reticuloendotheliosis virus was confirmed as a significant cause of mortality in captive prairie chickens.

Characterization of T-cell lymphomas associated with an outbreak of reticuloendotheliosis in turkeys.

Increased mortality and decreased egg production associated with disseminated lymphoma were observed in a turkey breeding flock for more than 20 weeks. A few unrelated meat turkey flocks, from the same integrator, experienced increased condemnation due to neoplasia in a few organs. Lymphoma was characterized by a uniform population of large lymphocytes with large vesicular nuclei containing one or two nucleoli and with little, faintly staining, basophilic cytoplasm. Neoplastic cells replaced normal tissue and were consistent with lesions seen with reticuloendotheliosis virus (REV) infection. Immunoperoxidase and fluorescent antibody staining characterized the neoplastic cells as CD3+, CD4+ and CD8- lymphocytes. Infection with REV was confirmed by virus isolation, polymerase chain reaction, serology and indirect fluorescent antibody. Poults hatched from these breeders tested positive for REV antibodies at hatch, but the performance of these flocks was normal and lymphoma was not observed. The origin of REV infection in this outbreak could not be determined. This is the first documented report of T-cell lymphomas associated with REV in commercial flocks. Furthermore, this is the first time that lymphomas have been characterized as T helper cells (CD3+ CD4+ and CD8-) in an outbreak of REV in turkeys.