Proventriculitis in broiler chickens: effects of immunosuppression

A Retrospective Study of Transmissible Viral Proventriculitis in Broiler Chickens in California: 2000-18

Transmissible viral proventriculitis (TVP) is a disease of chickens, mostly in broilers of 2-8 wk of age. Chicken proventricular necrosis virus (CPNV), a birnavirus, is the etiologic agent. Characteristic gross lesions are enlargement, atony, and pallor of the proventriculus. Cases diagnosed in California between 2000 and 2018 (n = 477), originating from 93 different farms representing all major companies in the region, were analyzed. Frequency of cases varied widely between years, with no recognizable seasonality. The flocks were between 6 and 61 days of age; the average age was 34.0 days, and the median age was 35 days. In 166 cases, between 6.3% and 100% of the submitted birds had gross lesions in the proventriculus. The most common findings were enlarged or dilated proventriculi, thickened walls, and pale or mottled serosal appearance. Histopathologically, inflammation of the glands was the most frequent finding. Other lesions included necrosis, hyperplasia, or both conditions of the glandular epithelium; dilated glands; and occasionally fibrin deposition, fibrosis, and hemorrhages. Twenty-three proventriculi from six cases were tested by immunohistochemistry for the presence of CPNV antigen; 21 stained positive. In 209 cases, birds also had lesions in the bursa fabricii attributed to infectious bursal disease, but with no significant difference in the mean percentage of birds with gross lesions in the proventriculus between cases with or without lesions in the bursa fabricii. The results show that TVP is a common disease of broiler flocks in California and confirms that CPNV is the likely causative agent.

Ascaridia galli induced ulcerative proventriculitis in a poultry bird

Various possible causes of proventriculitis include virus, bacteria, fungus, protozoans, nematodes, biogenic amines and excessive copper sulphate. In the present case, parasites were found in the lumen of the proventriculus, gizzard and duodenum of a poultry bird. Characteristic features of the parasite were studied and confirmed as Ascaridia galli. An ulcerative proventriculitis evident as denuded superficial epithelium, sub-epithelial hemorrhages, infiltration of the inflammatory cells and fibrosis were seen at histopathology. Proventriculitis caused by A. galli has not been reported till date. Here, we report a case of ulcerative proventriculitis in a poultry bird caused by nematode, A. galli.

Runting Stunting Syndrome Associated with Transmissible Viral Proventriculitis in Broiler Chickens

This report describes an outbreak of transmissible viral proventriculitis (TVP) associated with runting stunting syndrome (RSS) in 25- and 28-day-old broiler chickens, in which chicken proventricular necrosis virus (CNPV) was detected. Clinical signs included poor uniformity, very small birds for their age, increased mortality, and culling of smaller birds. Almost all birds necropsied exhibited moderate to severely enlarged proventriculi with diffusely pale serosa and thickened walls. Microscopically the proventriculi had lesions of degeneration and necrosis of the epithelium of the proventricular glands, accompanied by lymphocytic inflammation and glandular hyperplasia, with occasional formation of lymphoid nodules within the glandular parenchyma. Immunohistochemistry staining for CPNV was positive. Positive staining was generally found in the cytoplasm of glandular epithelial cells in the form of finely granular brown pigment. CPNV RNA was detected in the proventriculi by reverse transcriptase-PCR (RT-PCR). Other findings included mild enteritis in a few birds and small bursa of Fabricius. Direct electron microscopy performed on the intestinal samples was negative for viral particles. RT-PCR analysis of bursae was positive for infectious bursal disease virus (IBDV). In conclusion, this report associates TVP with RSS by describing an outbreak in which TVP attributable to CPNV was the most commonly found lesionin chickens with a clinical history compatible with RSS. Therefore, TVP should be considered as a possible differential diagnosis in cases compatible with RSS.

Histopathology in diagnosis of broiler chicken and layer diseases--review of cases 1999-2010

The aim of this study was to estimate the prevalence of histopathological lesions in the different organs in relation to the commercial-type and the age of birds (i.e. broiler chickens and layers). During the period 1999-2010 a total of 189 cases was submitted to the Division of Animal Pathomorphology, Department of Pathology and Veterinary Diagnostics at WULS. Most cases were found in broiler chickens (66.7%). The majority of the histopathological lesions were detected in the liver and lymphoid organs. In of 29% cases of hepatic injury pathognomonic lesions associated with inclusion body hepatitis (IBH) were found. The mean age of birds was 23 days. Among IBH cases proventriculitis (58%) was more often found than gizzard lesions (25.8%). Interestingly, we noted some intranuclear inclusions in the epithelial cells within the proventriculus. A low percentage of histopathological evidence of infectious bursal disease (IBD) was reported in chickens. The gastrointestinal tract was the second most frequent predilection site for histopathological lesions. Histopathological findings within the heart and lungs were less common and were more often seen in the upper respiratory tract. Cases of infectious laryngotracheitis (ILT) were registered in broiler chickens (3.2%, mean age 37 days) and in layers (4.8%; mean age 196 days). Lesions associated with Marek's disease, avian leukosis and fowl pox were recognized only in layers, respectively in 3.2% (mean age 176 days), 1.6% (mean age 205 days) and 1.1% (mean age 196 days) of all cases. Avian encephalomyelitis (AE) was noted only in 0.5% of all cases.

Transmissible viral proventriculitis identified in broiler breeder and layer hens

Transmissible viral proventriculitis (TVP) is a recognized cause of production losses in broiler chickens, but previously it has not been reported in broiler breeder and commercial layer hens. In this study, TVP was identified in broiler breeder and commercial layer hens, 9-20 wk of age, based on histopathologic detection of characteristic microscopic lesions. Microscopic lesions in proventriculi of affected hens consisted of glandular epithelial necrosis, ductal epithelial hyperplasia, replacement of glandular epithelium with ductal epithelium, and diffuse interstitial lymphoid infiltration. Additionally, chicken proventricular necrosis virus (CPNV), a virus previously identified as the etiology of TVP in broiler chickens, was detected in proventriculi of TVP-affected hens using a reverse transcriptase-polymerase chain reaction procedure. The findings identify TVP as a potential cause of production losses in broiler breeder and commercial layer hens and provide additional evidence for etiologic involvement in TVP by CPNV.

Effect of the polysaccharide extract from the edible mushroom Pleurotus ostreatus against infectious bursal disease virus

The polysaccharide-containing extracellular fractions (EFs) of the edible mushroom Pleurotus ostreatus have immunomodulating effects. Being aware of these therapeutic effects of mushroom extracts, we have investigated the synergistic relations between these extracts and BIAVAC and BIAROMVAC vaccines. These vaccines target the stimulation of the immune system in commercial poultry, which are extremely vulnerable in the first days of their lives. By administrating EF with polysaccharides from P. ostreatus to unvaccinated broilers we have noticed slow stimulation of maternal antibodies against infectious bursal disease (IBD) starting from four weeks post hatching. For the broilers vaccinated with BIAVAC and BIAROMVAC vaccines a low to almost complete lack of IBD maternal antibodies has been recorded. By adding 5% and 15% EF in the water intake, as compared to the reaction of the immune system in the previous experiment, the level of IBD antibodies was increased. This has led us to believe that by using this combination of BIAVAC and BIAROMVAC vaccine and EF from P. ostreatus we can obtain good results in stimulating the production of IBD antibodies in the period of the chicken first days of life, which are critical to broilers' survival. This can be rationalized by the newly proposed reactivity biological activity (ReBiAc) principles by examining the parabolic relationship between EF administration and recorded biological activity.

Bilateral effects of vaccination against infectious bursal disease and Newcastle disease in specific-pathogen-free layers and commercial broiler chickens

Different infectious bursal disease virus (IBDV) live vaccines (intermediate, intermediate plus) were compared for their immunosuppressive abilities in specific-pathogen-free (SPF) layer-type chickens or commercial broilers. The Newcastle disease virus (NDV) vaccination model was applied to determine not only IBDV-induced immunosuppression but also bilateral effects between IBDV and NDV. None of the IBDV vaccines abrogated NDV vaccine-induced protection. All NDV-vaccinated SPF layers and broilers were protected against NDV challenge independent of circulating NDV antibody levels. Sustained suppression of NDV antibody development was observed in SPF layers, which had received the intermediate plus IBDV vaccine. We observed a temporary suppression of NDV antibody development in broilers vaccinated with one of the intermediate, as well as the intermediate plus, IBDV vaccines. Different genetic backgrounds, ages, and residual maternal antibodies might have influenced the pathogenesis of IBDV in the different types of chickens. Temporary suppression of NDV antibody response in broilers was only seen if the NDV vaccine was administered before and not, as it was speculated previously, at the time the peak of IBDV-induced bursa lesions was detected. For the first time, we have demonstrated that the NDV vaccine had an interfering effect with the pathogenesis of the intermediate as well as the intermediate plus IBDV vaccine. NDV vaccination enhanced the incidence of IBDV bursa lesions and IBDV antibody development. This observation indicates that this bilateral effect of an IBDV and NDV vaccination should be considered in the field and could have consequences for the performance of broiler flocks.

Experimental reproduction of transmissible viral proventriculitis by infection of chickens with a novel adenovirus-like virus (isolate R11/3)

Transmissible viral proventriculitis (TVP) was experimentally reproduced in 2-wk-old specific-pathogen-free chickens and commercial broiler chickens by eyedrop inoculation of adenovirus-like virus (AdLV), isolate R1 1/3. No clinical signs and no weight gain depression were observed in chickens inoculated with AdLV (R11/3); however, gross and microscopic lesions characteristic of TVP were present in proventriculi of inoculated chickens. Proventriculi of AdLV (R11/3)-inoculated chickens were markedly enlarged, compared with sham-inoculated controls, by day 7 postinoculation (PI). Microscopic lesions in proventriculi of inoculated chickens were detected beginning on day 3 PI and consisted of degeneration and necrosis of glandular epithelium, ductal epithelial hyperplasia, replacement of glandular epithelium with ductal epithelium, and diffuse interstitial lymphoid infiltration; no microscopic lesions were observed in other tissues. AdLV (R11/3) antigens were detected in proventriculi by immunohistochemistry on days 3-10 PI in inoculated SPF chickens and days 3-21 PI in inoculated commercial broiler chickens; no viral antigens were detected in other tissues. AdLV (R11/3) was reisolated from proventriculi of inoculated SPF and commercial broiler chickens on days 5 and 7 PI. No virus, viral antigens, or lesions were detected in proventriculi collected from sham-inoculated chickens. These findings indicate an etiologic role for AdLV (R11/3) in TVP.

Identification of infectious bursal disease viruses from RNA extracted from paraffin-embedded tissue

After histopathologic screening of bursas of Fabricius for the presence of infectious bursal disease virus (IBDV) lesions, the hypervariable region of the VP2 gene for IBDV was extracted from formalin-fixed paraffin-embedded tissue blocks. With real-time reverse transcription-polymerase chain reaction (RT-PCR) and sequencing, IBDV was identified in 227 different blocks. The ability to identify the actual virus strain associated with the lesions observed microscopically in the bursa of Fabricius allowed for direct correlation between viral identity and lesions, which may help in designing vaccination strategies. Several new emerging viruses that do not group with other known IBDVs in phylogenetic tree analysis were identified, as well as a unique variant virus that had 63 nucleotides missing from its hypervariable region.

Partial characterization of an adenovirus-like virus isolated from broiler chickens with transmissible viral proventriculitis

Transmissible viral proventriculitis (TVP) was experimentally reproduced in specific-pathogen-free chickens using a homogenate of proventricular tissue obtained from TVP-affected commercial broiler chickens. Thin-section electron microscopy revealed intranuclear, approximately 70-nanometer (nm), adenovirus-like viruses (AdLV) within proventricular lesions. The AdLV, designated AdLV (R11/3), could not be propagated using various avian and mammalian cell cultures or by inoculation of embryonated chicken eggs by yolk, allantoic, or chorioallantoic membrane routes. However, AdLV (R11/3) was successfully propagated by amniotic inoculation of embryonated chicken eggs, with detection of the virus in proventriculi and intestinal contents of hatched 2-day-old chicks (8 days postinoculation). Virus propagation was evident in in ovo-inoculated chicks by (1) gross and microscopic lesions in proventriculi consistent with TVP, (2) immunohistochemical localization of AdLV (R11/3) antigens in proventricular epithelium, (3) thin-section electron microscopic detection of intranuclear, approximately 70-nm AdLVs within proventricular epithelium, and (4) negative-stain electron microscopic detection of extracellular, approximately 70-nm AdLVs in intestinal contents. Indirect immunofluorescence and polymerase chain reaction procedures that specifically recognize groups I, II, and III avian adenoviruses failed to recognize AdLV (R11/3). The findings suggest an etiologic role for AdLV (R11/3) in TVP and indicate that this virus is distinct from known avian adenoviruses.

Proventriculitis in broiler chickens: immunohistochemical characterization of the lymphocytes infiltrating the proventricular glands

Broiler chickens with transmissible proventriculitis have severe lymphocytic infiltration of the proventricular glands. The distribution of T cells and B cells in these infiltrates was studied histopathologically, and their identity was confirmed immunohistochemically (CD3, CD4, CD8, and B cells). To reproduce this disease, 1-day-old commercial boilers were orally gavaged with homogenized proventriculi from broilers with proventriculitis. Resulting lesions were examined at both acute (7 days postinoculation [i]) and chronic (14 and 21 dpi) time points. Lymphocytic infiltrates in the proventricular glands and the mucosal lamina propria were present at all time points and were most prominent and demarcated at 14 dpi. T and B lymphocytes were present during acute and chronic proventriculitis, but their distribution varied within the glands. Lymphocytic infiltrates in the proventricular glands and in the lamina propria were predominantly CD3+T cells, and most of these were also CD8+. B cells and CD4+ T cells formed aggregates in chronic proventriculitis. Thus, both cell-mediated and humoral immune responses are induced during transmissible proventriculitis, and the cell-mediated immune response is morphologically greater.