A retrospective study of pigeon herpesviral infection in domestic pigeons in California (1991-2014) and literature review

We characterized naturally occurring pigeon herpesvirus (PiHV; Columbid alphaherpesvirus 1) infection in domestic pigeons in California. We retrieved and analyzed 62 pathology reports produced between 1991 and 2014 at the California Animal Health and Food Safety Laboratory System. In 56 of the cases, the diagnosis of PiHV infection was established based on histopathology, either alone (44 cases) or combined with virus isolation (VI; 8), transmission electron microscopy (TEM; 3), or PCR (1); in the remaining 6 cases, the diagnosis was established based on VI (5 cases) or TEM (1) alone. PiHV infection affected 1 system in 34, 2 in 16, and ≥3 systems in 6 cases; data were not available for the remaining 6 cases. Most commonly affected was the digestive system (55 cases), followed by the respiratory tract (5) and lymphoid system (2). The liver (39 cases), crop (17), and esophagus (14) were the organs affected most commonly. Many affected cells often bore single eosinophilic intranuclear inclusion bodies. PiHV infection was a secondary diagnosis or incidental finding in 35 cases. Most (55) cases had 1 (21), or up to 4 (34), other concurrent infections; the most common concurrent infections were pigeon circoviral infection (26), trichomonosis (24), aspergillosis (11), and colibacillosis (10).

Nonenteric Lesions of Necrotic Enteritis in Commercial Chickens in California: 25 Cases (2009-2018)

Necrotic enteritis (NE) is an important enteric disease affecting a wide variety of avian species, including poultry, caused by Clostridium perfringens type G and, rarely, type C. Significant economic losses can result from elevated mortality rates and poor performance, such as decreased weight gain associated with intestinal damage and impaired absorption of nutrients. Additional losses can result from elevated condemnation at the processing plant because of a high incidence of cholangiohepatitis. Nonenteric lesions associated with NE have been rarely reported. This paper describes uncommon presentations of NE in commercial chickens received by the California Animal Health and Food Safety Laboratory (Turlock and Tulare branches) between 2009 and 2018. Overall, extraintestinal lesions associated with C. perfringens were diagnosed in 25 cases of NE involving commercial broiler chickens. The extraintestinal sites most commonly affected included liver, followed by gizzard, bursa of Fabricius, gall bladder, and spleen. The etiology of these lesions, C. perfringens, was confirmed from a combination of gross, bacteriologic, microscopic, and immunohistochemical findings. The most common predisposing factors for NE identified were coccidiosis (56%, 14/25) and immunosuppressive disease agents, including infectious bursal disease virus (16%, 4/25) and fowl adenovirus group 1 (4%, 1/25). Additionally, four cases (16%) had microscopic lesions compatible with cystic enteritis, probably of viral etiology. This study describes the incidence of extraintestinal lesions of NE in chickens, underlying the role of enteric disorders and immunosuppression as major predisposing factors for the development of NE.

Health surveillance of a potential bridge host: Pathogen exposure risks posed to avian populations augmented with captive-bred pheasants

Augmentation of wild populations with captive‐bred individuals presents an inherent risk of co‐introducing novel pathogens to naïve species, but it can be an important tool for supplementing small or declining populations. Game species used for human enterprise and recreation such as the ring‐necked pheasant (Phasianus colchicus) are commonly raised in captivity and released onto public and private wildlands as a method of augmenting naturalized pheasant populations. This study presents findings on pathogen exposure from three sources of serological data collected in California during 2014–2017 including (a) 71 pen‐reared pheasants sampled across seven game bird breeding farms, (b) six previously released pen‐reared pheasants captured at two study sites where wild pheasants occurred and (c) 79 wild pheasants captured across six study sites. In both pen‐reared and wild pheasants, antibodies were detected against haemorrhagic enteritis virus (HEV), infectious laryngotracheitis (ILT), infectious bursal disease virus (IBDV), paramyxovirus type 1 (PMV‐1) and Pasteurella multocida (PM). Previously released pen‐reared pheasants were seropositive for HEV, ILT, and PM. Generalized linear mixed models accounting for intraclass correlation within groups indicated that pen‐reared pheasants were more than twice as likely to test positive for HEV antibodies. Necropsy and ancillary diagnostics were performed in addition to serological testing on 40 pen‐reared pheasants sampled from five of the seven farms. Pheasants from three of these farms tested positive by PCR for Siadenovirus, the causative agent of both haemorrhagic enteritis in turkeys and marble spleen disease of pheasants, which are serologically indistinguishable. Following necropsy, owners from the five farms were surveyed regarding husbandry and biosecurity practices. Farms ranged in size from 10,000 to more than 100,000 birds, two farms raised other game bird species on premises, and two farms used some form of vaccination. Biosecurity practices varied by farm, but the largest farm implemented the strictest practices.

Case Report - A Case Report of Avian Malaria (Plasmodium spp.) in Pen-Reared Pigeons (Columbia livia)

One dead 6-week-old, male racing pigeon ( Columbia livia ) was submitted for postmortem evaluation after presenting with weight loss, anorexia, dry shanks, dehydration and lethargy. The bird belonged to a confined flock with 12 other pigeons raised by a hobbyist. Two pigeons in the flock reportedly had died with a history of similar clinical signs. On gross examination, the liver and the spleen were diffusely dark brown to black. Histopathology revealed moderate to large amounts of anisotropic, intracytoplasmic black pigment, compatible with hemozoin, in the spleen, liver, lung and kidneys, with small amounts in the heart and meninges of the brain. Marked plasmacytic infiltrates were observed in liver, lungs, heart and kidneys. Blood smears from a clinically affected concomitant pigeon from the flock revealed numerous light-blue, round to oval, intraerythrocytic trophozoites and meronts suggestive of Plasmodium spp. PCR and sequencing tests were performed from spleen and ceca using fragments of the 18S ribosomal RNA and the mitochondrial cytochrome B (cytB) genes. Sequencing results confirmed the presence of Plasmodium in the affected pigeon. Although an exact genetic match could not be determined, the most similar species to the isolate from this study are P. relictum , P. matutinum, P. lutzi and P. homocircumflexum .

Chlamydiosis in a Gouldian Finch (Erythrura gouldiae)

Avian chlamydiosis is an infection caused by obligate intracellular and Gram-negative bacteria belonging to the family Chlamydiaceae and has been reported in more than 450 avian species distributed in 30 orders. In particular, a high prevalence of infection has been demonstrated in wild passerine populations, including both asymptomatic and clinically ill individuals, suggesting a role of these avian species as important carriers. In May 2018, avian chlamydiosis was diagnosed in a 1-year-old male Gouldian finch (Erythrura gouldiae) at the Turlock Branch of the California Animal Health and Food Safety Laboratory System. The bird belonged to an outdoor aviary with mixed avian species, including Gouldian finches, doves (Geopelia cuneata and Spilopelia chinensis), and psittacines (Aratinga, Psittacula, Pyrrhura, and Trichoglossus sp.). Severe respiratory distress and mortality were noted among the finches. Gross and histopathologic lesions were concentrated in the liver and spleen, with a mild involvement of the upper respiratory tract. Chlamydia spp. were detected in the spleen and kidney by real-time PCR and were further confirmed by immunohistochemistry. Subsequently, Chlamydia psittaci was isolated from the liver and spleen and characterized as a CP3-like strain (genotype B). In addition, viral particles compatible with circovirus were identified in the liver by direct electron microscopy. To the authors' knowledge, this is the first report of avian chlamydiosis with hepatic viral particles consistent with circovirus infection in a Gouldian finch.

Partial Molecular Characterization and Pathogenicity Study of an Avian Reovirus Causing Tenosynovitis in Commercial Broilers

This study describes the molecular characterization of avian reoviruses (ARVs) isolated during an outbreak in commercial chickens between 2015 and 2016. In addition, a pathogenicity study of a selected ARV strain isolated from a field case of viral tenosynovitis in commercial broiler chickens was performed. On the basis of phylogenetic analysis of a 1088-bp fragment of the ARV S1 gene, the investigated sequences were differentiated into five distinct genotypic clusters (GCs), namely GC1, GC2, GC3, GC4, and GC6. Specific-pathogen-free (SPF) and commercial broiler chickens were challenged with the GC1 genetic type MK247011, at 14 days of age via the interdigital toe web. No significant effects in body weight gain and feed conversion were detected in both chicken types. The Δ interdigital web thickness was most severe at 4 days postchallenge (DPC) in both the SPF and broiler subgroups. The inflammation in SPF birds was slightly more severe compared with broilers. Neither mortality nor clinical signs occurred in the infected groups for the duration of the experiment, despite the presence of significant microscopic lesions in challenged birds. Microscopic changes of tenosynovitis became evident at 3 DPC, with the highest incidence and severity detected at 14 and 21 DPC, respectively. Seroconversion against ARV occurred 3 wk postchallenge, and the microscopic lesions detected in tendon and heart sections were highly compatible with those described in the field. Increased severity of tenosynovitis and epicarditis lesions were noted in the ARV-challenged groups compared with the control groups. Although SPF and broiler chickens showed comparable responses to the challenge with an ARV genetic variant, detected lesions were subclinical, denoting the limitations of our challenge approach. The age selected in this experiment possibly influenced the course of the infection. Data from this study highlight the genotypic diversity of isolates in California, and the outcome of the pathogenicity study can be used as a basis to improve protocols for pathogenicity studies to characterize ARV variants causing clinical disease in the field.

Molecular epidemiology of endemic and very virulent infectious bursal disease virus genogroups in backyard chickens in California, 2009-2017

Pathogenic strains of infectious bursal disease virus (IBDV) are associated with increased morbidity, mortality, and immunosuppression in susceptible chickens. Backyard poultry is increasing in popularity in the United States, but very little is known about the prevalence and molecular epidemiology of IBDV within these flocks. We performed a retrospective study and phylogenetic analyses of IBDV detected in backyard chickens (BYCs) submitted to the California Animal Health and Food Safety (CAHFS) diagnostic laboratory system in 2009-2017. There were 17 CAHFS autopsy cases of very virulent IBDV (vvIBDV) segment A detected by RT-rtPCR in BYC flocks from 7 counties in California from 2009-2017. During this same time period, non-vvIBDV genotypes were detected by RT-rtPCR in 16 autopsy cases originating from BYC premises in 10 counties in California. Subsequent RT-PCR and phylogenetic analysis of a segment of the hvVP2 and VP1 gene identified vvIBDV, interserotypic reassortant IBDV (vvIBDV segment A and serotype 2 segment B), and non-vvIBDV (variant/subclinical IBDV and classic IBDV) strains in BYC flocks in California.

Otitis and meningoencephalitis associated with infectious coryza ( Avibacterium paragallinarum) in commercial broiler chickens

Infectious coryza, caused by Avibacterium paragallinarum, is an acute respiratory disease of poultry that can result in substantial morbidity, mortality, and economic losses. In March 2017, the Turlock branch of the California Animal Health and Food Safety laboratory system encountered an unusual clinical and pathologic presentation of infectious coryza in 6 live, 29-d-old, commercial broiler chickens that were submitted for diagnostic investigation. Antemortem evaluation revealed severe neurologic signs, including disorientation, torticollis, and opisthotonos. Swollen head-like syndrome and sinusitis were also present. Histologically, severe sinusitis, cranial osteomyelitis, otitis media and interna, and meningoencephalitis were noted, explaining the clinical signs described. A. paragallinarum was readily isolated from the upper and lower respiratory tract, brain, and cranial bones. Infectious bronchitis virus (IBV) was also detected by PCR, and IBV was isolated in embryonated chicken eggs. Based on sequencing analysis, the IBV appeared 99% homologous to strain CA1737. A synergistic effect between A. paragallinarum and IBV, resulting in exacerbation of clinical signs and increased mortality, may have occurred in this case. A. paragallinarum should be considered among the possible causes of neurologic signs in chickens. Appropriate media should be used for bacterial isolation, and the role of additional contributing factors and/or complicating agents should be investigated in cases of infectious coryza.

Pathology and Tissue Distribution of an LPAI H5N8 of North American Lineage Isolated from an Outbreak in Commercial Japanese Quail (Coturnix c. japonica) in the Central Valley of California

This report describes the pathology and tissue distribution of avian influenza (AI) antigens by immunohistochemistry (IHC) in the tissues of commercial layer quail from a natural outbreak of low pathogenic avian influenza (LPAI) H5N8. LPAI virus H5N8 of North American lineage was diagnosed in commercial Japanese quail hens ( Coturnix coturnix japonica) in California based on serology, reverse-transcriptase real-time polymerase chain reaction, virus isolation, and sequencing. The sudden increase in mortality in a flock of laying quail hens had prompted the submission of 15 live and 5 dead, 10- to 15-wk-old quail to the California Animal Health and Food Safety Laboratory System, Turlock branch in the beginning of April 2014. There was mild bilateral swelling of the eyelids and greenish diarrhea in 4/15 live quail submitted. On postmortem examination, there were severe, extensive hemorrhages and multifocal, confluent pale foci in the pancreas in 10/20 birds. Liver gross lesions in five birds ranged from a few pale areas to numerous disseminated foci. Histology revealed moderate to severe necrosis of acinar cells in the pancreas with little or no inflammation in most of the birds. Livers had acute multifocal coagulative necrosis of hepatocytes with fibrin exudation and infiltration of few to large numbers of heterophils and lymphocytes randomly scattered throughout. The AI virus was detected in the nucleus and cytoplasm of pancreatic acinar cells and hepatocytes by IHC targeting the nucleoprotein of the AI virus. A few birds had AI antigen in the reticuloendothelial cells of the spleen, endothelial cells of the lungs, epithelium of the respiratory mucosa, and lamina propria of the intestine. The severity of the lesions observed in this natural outbreak of LPAI in quail was higher than that expected for the pathotypic presentation in this species.

Pathogenicity of Genome Reassortant Infectious Bursal Disease Viruses in Chickens and Turkeys

Infectious bursal disease virus (IBDV) contains two genome segments (segment A/segment B) that can reassort among the viruses. Reassortant IBDVs have been identified in several countries including the United States. These reassortant viruses usually include at least one genome segment from a very virulent (vv)IBDV strain. In vivo virulence of six reassortant IBDV from the United States was assessed relative to the virulence of three frequently described IBDV pathotypes: vvIBDV (rB strain), classic virulent (cv)IBDV (STC strain), and subclinical (sc)IBDV (Del-E strain). Morbidity and mortality in 4-wk-old specific-pathogen-free (SPF) leghorns indicated that reassortant IBDV with a vv genome segment A and non-vv segment B were less pathogenic than the vv/vv rB strain but more pathogenic than the cv/cv STC strain. The sc/vv IBDV strain D6337 (sc/vv) was comparable to the STC strain in pathogenicity. Viruses with a serotype 2 (ser2) genome segment A, regardless of the type of genome segment B, did not cause clinical disease in SPF chickens or turkeys. None of the reassorted viruses caused morbidity, mortality, or gross lesions in SPF turkeys. Histopathologic lesions in the bursa of turkeys were not observed in any group except those challenged with the serotype 2 OH strain, which had a mild lymphocytic depletion. No mortality was observed in maternally immune broilers inoculated with any of the IBDV pathotypes at 1, 2, 3, and 4 wk of age. No bursal lesions were observed in any of the broiler chicken groups at 1 wk of age except for the D2712 (ser2/cv)-inoculated birds that had mild lymphocyte depletion. Based on evaluation of bursal lesion scores and IBDV reverse transcriptase-PCR on broilers challenged at 2 wk of age, the K669 (vv/ser2) virus broke through the maternal immunity while the STC, Del-E, rB, D2712 (ser2/cv), and 7741 (vv/cv) viruses did not. All viruses broke through maternal immunity in the broilers at 3 wk of age except the Del-E scIBDV and D2712 (ser2/cv) reassortant IBDVs. At 4 wk of age, maternal antibodies were very low and bursal lesions were observed in all broilers challenged with the viruses. The data indicate that genome reassortant IBDVs are less pathogenic than is the rB (vv/vv) IBDV. However, the reassortant viruses with a vv genome segment A can still cause morbidity and mortality in SPF chickens, and they were able to break through maternal immunity produced via use of commercial classic and variant vaccines at an early age. This suggests that current breeder vaccination programs may not adequately protect against the reassortant vv/ser2 and vv/cv IBDV strains.

Trichodinosis associated with pathology of the reproductive tract in waterfowl

Trichodinid ciliophorans are opportunistic parasites of many species of fish, amphibians, and molluscs, but yet never reported in association with lesions in birds. Postmortem and histopathological evaluation of a commercial adult Toulouse gander and female goose, and a wild Mallard drake revealed the presence of severe pathological parasitic colonization of their reproductive tracts. Histopathological findings included moderate to severe granulocytic inflammation, acanthosis, accentuation of the rete pegs, and proliferative hyperplastic squamous metaplasia of the mucosa of the ejaculatory ducts and groove, sulcus spermaticus, glandular part of the phallus (cavum penis), and oviduct in association with large numbers of ciliated protozoa anchored to the tissues or free in the lumen. These protozoa had characteristic morphological features analogous to the family of Trichodinidae. The source of this parasitism could not be determined. To our knowledge, this is the first report of trichodinosis associated with pathology in birds.

Pathogenicity associated with coinfection with very virulent infectious bursal disease and Infectious bursal disease virus strains endemic in the United States

The pathogenicity induced by co-challenge with the rB strain of very virulent Infectious bursal disease virus (vvIBDV) and IBDV pathotypes endemic in the United States was evaluated in specific pathogen–free chickens. Four- and 6-week-old birds were simultaneously challenged with a 105 50% egg infectious dose (EID50) of rB mixed with a 105 EID50 of one of the following viruses: standard classic (STC), subclinical variant (Del-E), subclinical variant (T1), or avirulent serotype 2 (OH). Each challenge group consisted of 5 chickens. The severity of disease was assessed by comparing the 5-day mortality rates, bursal lesions (mean bursal lesion scores), and mean bursal-to-body weight ratios in each of the challenged groups. A mortality of 100% (10/10 and 5/5) was observed in birds inoculated with only the vvIBDV (rB) strain at 4 weeks and 6 weeks of age, respectively. Although the sample sizes were low, a significant reduction in mortality and severity of disease, based on mean bursal lesion scores, was observed in groups co-challenged with rB and the less virulent pathotypes Del-E, T1, or OH at 4 weeks of age. Co-challenge with rB and the antigenically similar STC strain did not result in a significant decrease in mortality compared to challenge with the pathogenic rB strain at 4 weeks of age, but a significant reduction in the mean bursa lesion score was observed. At 6 weeks of age, a significant decrease in mortality and mean bursa lesion score was observed in the rB groups co-challenged with STC, Del-E, or T1 but not OH.

Mycotic Pododermatitis and Mycotic Pneumonia in Commercial Turkey Poults in Northern California

Seven 5-week-old broad-breasted white commercial meat turkeys were submitted to the California Animal Health and Food Safety laboratory in Turlock with a history of respiratory illness. The primary diagnostic findings were mycotic pododermatitis and mycotic pneumonia. The unique feature of this case was the colonization of footpad epidermis and subcutis by fungal hyphae in commercial turkey species. No fungal cultures were undertaken at the time of the necropsy; therefore, paraffin-embedded tissue sections of lung and footpads were used to extract, amplify, and sequence mycotic DNA. A mixed population of fungi was identified in both lung and footpads by polymerase chain reaction amplification of part of the large subunit ribosomal RNA gene using broad-range fungal primers and DNA sequencing. In footpads, sequences matching Cryptococcus saitoi and Cladosporium and Cudoniella species were identified. It is believed that these fungi were opportunistic pathogens originating from the litter. The fungi identified from lungs were Aspergillus species, most closely matching Aspergillus flavus and Arxiozyma telluris (most likely a contaminant). Mycotic pododermatitis in avian species is considered a rare pathologic finding, and few documented reports are available. The on-farm prevalence of footpad lesions was estimated at 3%, and there was no associated increase in the incidence of lameness or weight depression in affected birds. Microscopically, a granulomatous inflammatory reaction associated with fungal hyphae was observed in lung parenchyma. Disruption of keratinized epidermis, encrustations, and acute inflammation were also noted in footpads invaded with fungal hyphae.

Respiratory tract trichomoniasis in breeder squab candidates in Northern California

Breeder squab candidates between the ages of 6 and 16 wk were submitted to the California Animal Health and Food Safety Laboratory, Turlock branch, as a result of respiratory distress and increased mortality. These cases were submitted from one Northern California commercial squab operation on three separate occasions occurring between December 2007 and March 2008. Severe trichomoniasis was identified, primarily in the tracheal epithelium and lung of squabs, with few or no lesions in the oral cavity, crop, esophagus, and livers, where the organism commonly infiltrates. Infiltration of the trachea and lung sections with trichomonads was associated with a severe inflammatory response in the surrounding tissue. Diagnosis was confirmed with the use of histopathology and an immunoperoxidase special stain. Oxytetracycline supportive antibiotic therapy to prevent secondary bacterial infections was administered to remaining squabs on the farm, but no specific treatment regimen was instituted. This novel respiratory presentation of trichomoniasis continued over a period of 3 mo, until mortality gradually returned to normal.