Marek's disease virus associated ocular lymphoma in Roulroul partridges (Rollulus rouloul)

The genome evolution of Marek's disease viruses in chickens and turkeys in China

The virus that causes Marek's disease (MD) is globally ubiquitous in chickens, continuously evolving, and poses a significant threat to the poultry industry. Although vaccines are extensively used, MD still occurs frequently and the virus has evolved increased virulence in China. Here, we report an outbreak of MD in vaccinated chickens and unvaccinated turkeys in a backyard farm in Guangdong province, China, in 2018. Phylogenetic analysis revealed two lineages of MDVs at this farm, with one lineage, containing isolates from two turkeys and five chickens, clustering with virulent Chinese strains and displays a relatively high genetic divergence from the vaccine strains. These new isolates appear to have broken through vaccine immunity, yielding this outbreak of MD in chickens and turkeys. The second lineage included four chicken isolates that clustered with the CVI988 and 814 vaccine strains. The large diversity of MDVs in this single outbreak reveals a complex circulation of MDVs in China. Poor breeding conditions and the weak application of disease prevention and control measures make backyard farms a hotbed for the evolution of viruses that cause infectious diseases. This is especially important in MDV as the MD vaccines do not provide sterilizing immunity, which allows the replication and shedding of virulent field viruses by vaccinated individuals and supporting the continuous evolution of MDVs. Hence, constant monitoring of the evolution of MDVs is necessary to understand the evolution of these field viruses and potential expansions of their host range.

Immunohistochemical identification of T and B lymphocytes in formalin-fixed, paraffin-embedded tissues of 53 avian species using commercial antibodies

Providing a method to detect avian lymphocytes by immunohistochemistry (IHC) would be helpful for analyzing immune function and diagnosing diseases in birds. In this study, we comprehensively examined the immunohistochemical identification of avian T and B lymphocytes in formalin-fixed, paraffin-embedded tissues from 53 avian species across 15 orders, using eight commercially available lymphocyte markers. T lymphocytes from all 53 avian species tested were specifically detected by IHC using the anti-CD3 antibody (clone F7.2.38). The appropriate antibody for detecting avian B lymphocytes in IHC varied depending on the avian species. B lymphocytes were specifically labeled by IHC in 46 of 53 avian species (86.8%) using any of seven B cell markers. The anti-PAX5 antibody (clone SP34) immunohistochemically detected B lymphocytes from the majority of avian species (41 out of 53 species), excluding those in the orders Falconiformes (falcons) and Passeriformes (oscines). The anti-BAFF-R antibody (clone 2C4) proved suitable for detecting B lymphocytes in the orders Galliformes (landfowls) and Anseriformes (waterfowls) in IHC. Caution is advised when using the anti-BLA36 (clone A27-42) and two anti-CD20 (clone L26 and product No. PA5-16701) antibodies, which are commonly used as B cell markers in mammals, for detecting avian B lymphocytes. These antibodies reacted with cells located in both T and B cell areas in certain avian species. The anti-Bu-1a/b (clone AV20) and anti-CD79a (clone HM57) antibodies were found not to bind to B lymphocytes in various avian species in IHC.

Effect of ketoprofen on intravenous pharmacokinetics of ganciclovir in chukar partridges (Alectoris chukar)

The aim of the study was to determine the effect of ketoprofen (2 mg/kg) on the intravenous pharmacokinetics of ganciclovir (10 mg/kg) in chukar partridges (Alectoris chukar). Eight clinically healthy partridges were used in the study. The study was performed in two periods using a cross-over design following a 15-day drug washout period. Plasma concentrations of ganciclovir were determined using the high-pressure liquid chromatography-ultraviolet detector and analyzed by non-compartmental analysis. The elimination half-life (t_1/2ʎz ), area under the concentration-time curve (AUC_0-∞ ), total body clearance, and volume of distribution at steady state of ganciclovir were 1.63 h, 33.22 h*μg/ml, 0.30 L/h/kg, and 0.53 L/kg, respectively. Ketoprofen administration increased the t_1/2ʎz and AUC_0-∞ of ganciclovir by 78% and 108%, respectively, and while decreased Cl_T by 53%. The increased plasma concentration and prolonged elimination half-life of ganciclovir caused by ketoprofen may result in the prolonged duration of action and therapeutic effect of ganciclovir. However, the concomitant use requires determination of the pharmacokinetics of ketoprofen and the safety of both drugs.

A Review of Pathogen Transmission at the Backyard Chicken-Wild Bird Interface

Habitat conversion and the expansion of domesticated, invasive species into native habitats are increasingly recognized as drivers of pathogen emergence at the agricultural-wildlife interface. Poultry agriculture is one of the largest subsets of this interface, and pathogen spillover events between backyard chickens and wild birds are becoming more commonly reported. Native wild bird species are under numerous anthropogenic pressures, but the risks of pathogen spillover from domestic chickens have been historically underappreciated as a threat to wild birds. Now that the backyard chicken industry is one of the fastest growing industries in the world, it is imperative that the principles of biosecurity, specifically bioexclusion and biocontainment, are legislated and implemented. We reviewed the literature on spillover events of pathogens historically associated with poultry into wild birds. We also reviewed the reasons for biosecurity failures in backyard flocks that lead to those spillover events and provide recommendations for current and future backyard flock owners.

Morphological and Immunohistochemical Examination of Lymphoproliferative Lesions Caused by Marek's Disease Virus in Breeder Chickens

Simple Summary

The poultry industry is the most intensive and fastest growing among all livestock production systems, and, in the last decades, it has expanded exponentially due to an increasing demand for meat and eggs. Marek’s disease is a highly contagious and rapidly progressive lymphoproliferative disease. It is one of the most dangerous diseases of those affecting the sector because it causes important economic losses. Although widely controlled by vaccination programs, sometimes chickens are not totally protected, and the presence of virulent field strains can allow outbreaks. This case describes the occurrence of Marek’s disease observed in a breeder chicken flock that reported an increase in mortality rate (+0.4–0.6%) after the 32nd week. Histological analysis has highlighted severe lesions on visceral organs of chickens caused by Marek’s disease, especially in the intestinal tract of a hen that had a tumor mass in the distal part of the cloaca. Immunohistochemical staining confirmed the disease-associated tumor. The aim of this study was to underline the importance of vaccine administration related to the maintenance of proper biosecurity practice, especially in the first week of the raising cycle. In addition, monitoring for disease even after vaccination is crucial to minimize economic loss.

Abstract

Marek’s disease is widely controlled by vaccination programs; however, chickens are not totally protected, especially immediately after the vaccination when a strong challenge could interfere with the effectiveness of vaccination in the absence of proper biosecurity practice. This case report describes the occurrence of Marek’s disease (MD) observed in a breeder chicken flock reared southeast of Sicily. MD outbreak occurred from 32 to 47 weeks with an increase in weekly mortality rate (+0.4–0.6%). Overall, mortality rate related to Marek’s disease was about 6% at the end of the cycle. Carcasses of chickens found during the occurrence of disease underwent necropsy, and tissues were collected to confirm the infection. Gizzard, cecal tonsil, intestine, spleen and tumor mass were collected and analyzed from a carcass of one hen, 32 weeks old and apparently asymptomatic. Multiplex real-time PCR performed on spleen tissues detected the presence of MD virus pathogenic strain. Macroscopic and microscopic evaluation of the rest of the samples confirmed the neoplastic disease. Moreover, the immunophenotype of the tumor cells was identified as CD3 positive by immunohistochemical (IHC) staining. The vaccinated flock had become rapidly infected with the MD virus, which proves that the challenge of the MD virus was too strong in the rearing house at the beginning of the cycle, causing the outbreak.

Central Nervous System B-cell Lymphoma in a Bald Eagle ( Haliaeetus leucocephalus)

An adult bald eagle ( Haliaeetus leucocephalus) presented for nystagmus and an inability to fly. On physical examination, the eagle was open-mouth breathing and tachycardic at 200 beats per minute, had a wrinkled cere and sunken eyes, and was an estimated 10% dehydrated. Additionally, the eagle was extremely weak, with neurologic abnormalities including bilateral proprioceptive deficits, nystagmus, and no pupillary light reflex in the left eye. Despite aggressive treatment, the eagle continued to decline rapidly and subsequently died. On histologic examination, diffuse and widespread infiltration of neoplastic lymphocytes was present in the brain, optic nerves, and pecten. Immunohistochemical PAX-5 labeling confirmed B-cell lymphoma confined to the eye and nervous system. Test results for select avian retroviruses, Marek's disease, West Nile virus, avian influenza viruses, and Mycoplasma were negative. To our knowledge, this is the first report of B-cell lymphoma in a bald eagle. Although rare, this condition is a differential diagnosis in cases of neurologic or ocular diseases in birds.

Marek's disease in chickens: a review with focus on immunology

Marek's disease (MD), caused by Marek's disease virus (MDV), is a commercially important neoplastic disease of poultry which is only controlled by mass vaccination. Importantly, vaccines that can provide sterile immunity and inhibit virus transmission are lacking; such that vaccines are only capable of preventing neuropathy, oncogenic disease and immunosuppression, but are unable to prevent MDV transmission or infection, leading to emergence of increasingly virulent pathotypes. Hence, to address these issues, developing more efficacious vaccines that induce sterile immunity have become one of the important research goals for avian immunologists today. MDV shares very close genomic functional and structural characteristics to most mammalian herpes viruses such as herpes simplex virus (HSV). MD also provides an excellent T cell lymphoma model for gaining insights into other herpesvirus-induced oncogenesis in mammals and birds. For these reasons, we need to develop an in-depth knowledge and understanding of the host-viral interaction and host immunity against MD. Similarly, the underlying genetic variation within different chicken lines has a major impact on the outcome of infection. In this review article, we aim to investigate the pathogenesis of MDV infection, host immunity to MD and discuss areas of research that need to be further explored.