Infectious laryngotracheitis of chickens: Pathologic and immunohistochemistry findings

Infectious laryngotracheitis (ILT) is an important upper respiratory disease of chickens. Gross and histologic lesions of ILT in chickens are compared to immunohistochemistry to evaluate the diagnostic test sensitivity. A total of 31 separate ILT-confirmed necropsy submissions (12 commercial meat-type flocks, 13 egg-type producers, and 6 backyard flocks) were arbitrarily selected. Each submission ranged from 1 to 18 birds, for a total of 246 chickens. Cases with available formalin-fixed tissues were selected to include a range of bird production types, ages, clinical histories, and severity of macroscopic and histologic lesions. Macroscopic findings in the respiratory tract varied from increased mucus (55.6%) to fibrinonecrotic exudate (20.3%) and hemorrhages in the larynx and trachea (13.0%). Syncytia with intranuclear inclusion bodies were present in the respiratory tract epithelium with or without hemorrhages. Sections of conjunctiva, sinus, larynx, trachea, lung, and air sac were analyzed by immunohistochemistry (IHC) to detect gallid alphaherpesvirus 1 (GaHV-1) antigen. Positive immunolabeling was detected in the cytoplasm and nuclei of syncytia and epithelial cells in 18/22 conjunctivae (82%), 12/13 sinuses (92%), 18/22 larynxes (82%), 23/25 tracheas (92%), 10/21 lungs (57%), and 3/8 air sacs (37%). Of the 34 tissues with no visible syncytia or inclusion bodies, 8 were positive by IHC. In conclusion, IHC was useful to study the viral antigen tissue distribution and support the diagnosis of ILT when the histopathologic interpretation was doubtful.

Seroprevalence of Newcastle Disease Virus in Local Chickens in Njombe and Bahi Districs in Tanzania

Newcastle disease virus (NDV) causes significant losses of poultry in Tanzania. Like in many African countries, the regular surveillance of NDV is important for the control of disease. The objective of this study was to determine seroprevalence of NDV in backyard poultry in Bahi and Njombe districts of Tanzania over the rainy (May) and dry (November) seasons in 2016. Using hemaglutination inhibition test, the overall seroprevalence was determined to be 26.8%. The significant differences in seroprevalence was between seasons ((higher (34.9%) in dry season, p < 0.0001)) and age ((higher (30.3%), p < 0.0001 in adult birds)). There were no significant differences in seroprevalence between the districts or sex. The higher levels of “protective” antibody titers were significantly associated with location; Njombe (RR 1.15), dry season (RR 1.08), and age; adult birds (RR 1.16), however the prevalence of these titers was not high enough to conclude any herd immunity among these flocks. This study therefore provides a brief insight of NDV disease dynamics in Tanzania. Future studies focusing on transmission, strain type, and monthly dynamics of NDV in backyard flocks will provide greater insight into the disease dynamics and allow new practical strategies to alleviate the effects of NDV for the smallholder farmers

Description of factors decreasing egg incubation of creole hens (Gallus gallus domesticus)

Objective: To describe the factors that affect the incubation of fertile eggs of Creole hens (Gallus gallus domesticus) at Mezquital Valley, Hidalgo, Mexico. Design/Methodology/Approach: 448 eggs of Creole hens were incubated in a Casser model 7622 incubator, in which the number of infertile and fertile eggs was evaluated; within the number of fertile eggs, the number of dead embryos was determined; due to dehydration or damage caused by fungi and bacteria. From the live hatched chickens, those that died due to omphalitis were recorded. Results: 272 of 448 incubated eggs were fertile; 119 of them hatched and 153 were dead embryos. While 176 were infertile. Among the dead embryos, 84 of dehydration, 69 due to fungal and bacterial infection and 11 live hatched chicks due to omphalitis. Limitations/implications: The literature review found little information on factors affecting the hatching of fertile Creole chicken eggs in backyard flocks. Findings/conclusions: Infection by fungi and bacteria increase embryonic mortality, while omphalitis increases mortality during the first days of life of the backyard Creole chickens. High storage temperature in the nest or incubator causes embryo dehydration.

Prevalence of Select Intestinal Parasites in Alabama Backyard Poultry Flocks

Keeping chickens as backyard pets has become increasingly popular in the United States in recent years. However, biosecurity is generally low in backyard flocks. As a consequence, they can serve as reservoirs for various pathogens that pose a risk for commercial poultry or human health. Eighty-four fecal samples, 82 from chickens and two from turkeys, from 64 backyard flocks throughout the state of Alabama were collected in the summers of 2017 and 2018. Coccidia oocysts were seen in 64.1% of flocks with oocyst counts in most samples below 10,000 oocysts per gram. Eggs of Ascaridia spp. or Heterakis gallinarum were observed in 20.3% of the flocks, and eggs of Capillaria spp. in 26.6% of the flocks. Egg counts were low, rarely exceeding 1000 eggs per gram. DNA extracted directly from fecal samples was investigated by PCR for other relevant parasites. The results showed that 4.7% of flocks were positive for Histomonas meleagridis, 18.8% of flocks for Tetratrichomonas gallinarum, 18.8% of flocks for Cryptosporidium spp. and 87.5% of flocks for Blastocystis spp. The results will help to provide information that can be used to design outreach programs to improve health and wellbeing of birds in backyard flocks.

Molecular survey and interaction of common respiratory pathogens in chicken flocks (field perspective)

Aim: The present study was designed for the detection of the most prevalent respiratory infections in chicken flocks and clarifying their interaction and impact on flock health. Materials and Methods: A total of 359 serum samples were collected from 55 backyard chickens and tested using commercial enzyme-linked immunosorbent assay kits to determine the seroprevalence of Newcastle disease virus (NDV), infectious bronchitis virus (IBV), influenza type A, Mycoplasma gallisepticum (MG), and Mycoplasma synoviae (MS). Molecular prevalence of NDV, IBV, low pathogenic avian influenza virus (LPAIV) H9N2, MG, and MS was carried out on swab, and tissue samples collected from 55 backyard flocks and 11 commercial broiler flocks suffered from respiratory infections using polymerase chain reaction (PCR) and reverse transcription-PCR. Results: Seroprevalence of NDV, IBV, Influenza type A virus, MG, and MS in chicken backyard flocks was 56.4%, 50.9%, 12.7%, 14.5%, and 3.6%, respectively. Specific antibodies against one or more respiratory viruses and mycoplasma were detected in 36.4% of backyard flocks, indicating concurrent viral infections. The molecular survey showed that 90.9% of chicken backyard flocks were infected with common respiratory viruses (NDV, IBV, and LPAIV H9N2) while 81.8% of commercial broiler flocks were infected. The molecular prevalence rate of NDV, IBV, and LPAIV H9N2 was 46.97%, 56.1%, and 19.7% in backyard flocks, respectively. Combined viral and bacterial infection represented 40% and 63.6% of the respiratory infections, resulting in enhanced pathogenicity and increased mortalities of up to 87.5% and 27.8% in backyard and commercial flocks, respectively. Mixed infection of IBV, LPAIV H9N2, and/or Escherichia coli is the most prevalent mixed infection in broiler flocks, inducing severe clinical outcomes. Avian pathogenic E. coli was, respectively, isolated from 40% of backyard flocks and 81.82% of broiler flocks. Staphylococcus aureus was isolated from three backyard chicken flocks mixed with other respiratory pathogens with elevated mortality. Mixed infection of E. coli and MG reported in 9.1% of broiler flock. MG was detected in 14.5% of backyard flocks and 9.1% of broiler flocks while MS was detected only in 3.6% of backyard chickens mixed with E. coli, and other viruses. Conclusion: Our results confirm that mixed infections are more commonly prevalent and associated with dramatic exacerbation in clinical outcomes than a single infection. Bidirectional synergistic interaction between these concurrently interacted respiratory pathogens explains the severe clinical impact and high mortality rate. The high prevalence of IBV (either as a single or combined infection) with LPAIV H9N2 and/or E. coli, in spite of intensive use of commercial vaccines, increases the need for revising vaccination programs and the application of standard biosecurity measures. Backyard chickens impose a great risk and threaten commercial flocks due to the high prevalence of viral respiratory pathogens.

Molecular characterisation of an avian influenza (H5N8) outbreak in backyard flocks in Al Ahsa, Eastern Saudi Arabia, 2017–2018

BackgroundAvian influenza viruses are still causing major concern not only to the poultry industry but also to human health across the globe. The live poultry markets and the small-scale local breeding of various species of birds in backyards are still playing important roles in the sustainability of most virulent influenza viruses, especially H5N8.MethodsThe authors investigated an outbreak of highly pathogenic avian influenza H5N8 in backyard flocks in Al Ahsa, Eastern Saudi Arabia that occurred in 2017–2018.ResultsA range of poultry including chickens, ostriches, ducks, pigeons and turkeys were clinically affected. Phylogenetic analysis suggested that this was a common source outbreak caused by a virus closely related to H5N8 viruses causing outbreaks elsewhere in Saudi Arabia in early 2018.ConclusionsSmall backyard flocks are still contributing to the epidemiology and transmission of H5N8.

Molecular characterisation of Mycoplasma gallisepticum isolates from Iran in the period 2012–2017

Mycoplasma gallisepticum (MG) causes chronic non-fatal diseases in the poultry industry with a remarkable decrease in feed consumption, egg production and other production indices. To study the genetic characteristics of MG isolates in commercial and backyard poultry flocks, 21 positive samples from different regions of Iran were analysed in the period 2012–2017. Typical macroscopic and histopathological lesions of the upper respiratory tract and lungs were found, similar to those reported by other researchers. A 298–361 bp part of the mgc2 gene was sequenced and analysed. Based on the phylogenetic analysis, the Iranian MG isolates fell into four distinct subgroups. The nucleotide difference between subgroups 1 and 4 was remarkable (91.6–94.9%). A 22-amino-acid insertion was present in two of the studied MG isolates, not observed in other vaccine and standard MG strains. The Iranian Veterinary Organisation (IVO) should consider the observed diversity of prevalent MG isolates from both commercial and backyard flocks in designing the strategy for controlling MG. More studies are needed to understand modifications in MG antigenicity and pathogenicity because of the observed genetic variations.

Retrospective analysis of infectious laryngotracheitis in backyard chicken flocks in California, 2007–2017, and determination of strain origin by partial ICP4 sequencing

Infectious laryngotracheitis (ILT) can cause severe losses in backyard flocks (BYFs) and commercial poultry. The prevalence of ILT, the circulating strains of ILT virus (ILTV) in BYFs, and the correlation of disease in BYF and commercial operations, is largely unknown. Of 8,656 BYF submissions, 88 cases of ILT were diagnosed at the California Animal Health and Food Safety Laboratory System in 2007–2017. ILT diagnosis by year varied from 0.19% to 1.7% of the total BYF submissions, with the highest number of cases submitted from Amador and Riverside counties. Moderate tracheitis, conjunctivitis, and occluded tracheal lumen were commonly reported gross anatomic lesions. Microscopically, inflammation and edema were observed in the trachea, lung, and conjunctiva; 62 (70%) cases had intranuclear inclusion bodies (INIBs), with 10 cases containing INIBs only in conjunctival sections. To analyze the circulating ILTV strains and to differentiate between field and vaccine strains of ILTV, real-time PCR and sequencing of 996 base pairs of the infected-cell polypeptide 4 ( ICP4) gene was performed on 15 ILTV-positive tracheal samples and compared to reference field and vaccine ILTV ICP4 sequences in GenBank. Fourteen strains were identical or closely related to the chicken embryo origin live virus vaccine strains, and one strain was closely related to a Chinese isolate, the USDA reference strain, and a vaccine strain. The presence of ILT in BYFs in counties with high commercial poultry concentrations demonstrates a risk for disease transmission and emphasizes the importance of continued surveillance and improved biosecurity in BYFs.