M. Palanivelu

Duck virus enteritis (duck plague) – a comprehensive update

ABSTRACT Duck virus enteritis (DVE), also called duck plague, is one of the major contagious and fatal diseases of ducks, geese and swan. It is caused by duck enteritis virus (DEV)/Anatid herpesvirus-1 of the genus Mardivirus, family Herpesviridae, and subfamily Alpha-herpesvirinae. Of note, DVE has worldwide distribution, wherein migratory waterfowl plays a crucial role in its transmission within and between continents. Furthermore, horizontal and/ or vertical transmission plays a significant role in disease spread through oral-fecal discharges. Either of sexes from varying age groups of ducks is vulnerable to DVE. The disease is characterized by sudden death, vascular damage and subsequent internal hemorrhage, lesions in lymphoid organs, digestive mucosal eruptions, severe diarrhea and degenerative lesions in parenchymatous organs. Huge economic losses are connected with acute nature of the disease, increased morbidity and mortality (5%–100%), condemnations of carcasses, decreased egg production and hatchability. Although clinical manifestations and histopathology can provide preliminary diagnosis, the confirmatory diagnosis involves virus isolation and detection using serological and molecular tests. For prophylaxis, both live-attenuated and killed vaccines are being used in broiler and breeder ducks above 2 weeks of age. Since DEV is capable of becoming latent as well as shed intermittently, recombinant subunit and DNA vaccines either alone or in combination (polyvalent) are being targeted for its benign prevention. This review describes DEV, epidemiology, transmission, the disease (DVE), pathogenesis, and advances in diagnosis, vaccination and antiviral agents/therapies along with appropriate prevention and control strategies.

Prophylactic potential of resiquimod against very virulent infectious bursal disease virus (vvIBDV) challenge in the chicken

The study evaluated the prophylactic potential of resiquimod (R-848), a synthetic TLR7 agonist, against very virulent infectious bursal disease virus (vvIBDV) infection in chicken. Specific pathogen free White Leghorn chicks of three week age were treated with R-848 (50μg/bird, intramuscular) or PBS (n=26/group). Twenty four hour later, half of the birds from each group were challenged with 10(5) ELD50 of vvIBDV and observed for 10days. To understand the effect of R-848, immune response genes such as interferon (IFN)-β, IFN-γ, IL-1β, IL-4, iNOS and TLR7 were analyzed at 24 and 48h post-challenge in PBMCs ex vivo by real-time PCR (n=6/group). On day 4 post-challenge, representative birds (n=3/group) were sacrificed to study the bursal damage and IBDV antigen clearance. Immunosuppression was assessed by antibody response against live Newcastle disease virus (NDV) vaccine, which was administered on day 10 post-challenge. R-848 pre-treatment significantly upregulated the transcripts of each immune response gene studied (P<0.05). There was 50% mortality on vvIBDV challenge in control birds, while it was only 20% with R-848 group. R-848 pre-treatment reduced the bursal damage as indicated by lower bursal lesion score in histopathology, reduced IBDV antigen signal in immunohistochemistry and improved antigen clearance in agar gel immunodiffusion test. Further, it protected significantly against vvIBDV induced immunosuppression as indicated by HI antibody titre. It is concluded that pre-treatment of R-848 conferred partial protection from mortality and bursal damage while complete protection against immunosuppression in chicken when challenged with vvIBDV, which could be due to the upregulation of immune response genes.

Haemorrhagic enteritis of turkeys – current knowledge

ABSTRACT Haemorrhagic enteritis virus (HEV), an adenovirus associated with acute haemorrhagic gastro-intestinal disease of 6–11-week old turkeys predominantly hampers both humoral and cellular immunity. Affected birds are more prone to secondary complications (e.g. colibacillosis and clostridiosis) and failure to mount an effective vaccine-induced immune response. HEV belongs to the new genus Siadenovirus. Feco-oral transmission is the main route of entry of the virus and it mainly colonizes bursa, intestine and spleen. Both naturally occurring virulent and avirulent strains of HEVs are serologically indistinguishable. Recent findings revealed that ORF1, E3 and fib genes are the key factors affecting virulence. The adoption of suitable diagnostic tools, proper vaccination and biosecurity measures have restrained the occurrence of disease epidemics. For diagnostic purposes, the best source of HEV is either intestinal contents or samples from spleen. For rapid detection highly sensitive and specific tests such as quantitative real-time PCR based on Taq man probe has been designed. Avirulent strains of HEV or MSDV can be effectively used as live vaccines. Novel vaccines include recombinant hexon protein-based subunit vaccines or recombinant virus-vectored vaccines using fowl poxvirus (FPV) expressing the native hexon of HEV. Notably, subunit vaccines and recombinant virus vectored vaccines altogether offer high protection against challenge or field viruses. Herein, we converse a comprehensive analysis of the HEV genetics, disease pathobiology, advancements in diagnosis and vaccination along with appropriate prevention and control strategies.

A novel recombinant Meq protein based dot-ELISA for rapid and confirmatory diagnosis of Marek’s disease induced lymphoma in poultry

Mareks disease (MD), is an economically important virus disease of poultry throughout the world. In this study, we for the first time reports development of a novel dot enzyme-linked immunosorbent assay (dot-ELISA) for the confirmatory diagnosis of lymphoma caused by Mareks Disease Virus (MDV). Suspected lymphoma tissue extracts from the diseased birds were used for the Meq oncoprotein antigen detection, which is expressed specifically in MDV lymphomas. Recombinant Meq oncoprotein was expressed using Expresso™ Rhamnose Sumo Cloning and Expression system and the hyperimmune serum was raised against it, which was used later while developing dot-ELISA. The dot-ELISA exhibited higher specificity (92%) in diagnosing MD lymphomas as compared to conventional PCR (40%), where later assay is unable to differentiate disease development (lymphoma) and/or infection. The developed dot-ELISA proved to be a specific, rapid and inexpensive technique detecting MDV lymphomas in poultry. Of the note, this new assay could be opted as a valuable diagnostic tool in the resource poor countries andcould further be used to differentiate from other tumor causing viruses in poultry.

Pathomorphological studies of lung lesions in sheep

Respiratory disorders are very common in sheep and often not easily detectable in the live animals until it is complicated. Thus examination of lungs at slaughter is the only way to understand pathology behind respiratory disorders and their prompt diagnosis. And thus this study was aimed at documenting various pathological conditions affecting the lungs of sheep. A total number of 903 sheep carcasses were examined, out of which, lung lesions were recorded in 203 cases (22.48%). Pneumonia was recorded in 16.82% (152/903) cases, adenomatosis in 4.87% (44/903) cases and other lesions (atelectasis, emphysema and hemorrhages) in 0.78% (7/903) of cases. Based on duration of inflammation, involvement of tissue component and the principal constituent of the exudates, the lung lesions were further classified as acute bronchopneumonia (90/203 cases, 44.33%), sub-acute bronchopneumonia (28/203 cases, 13.79%), chronic bronchopneumonia (7/203 cases, 3.45%), acute interstitial pneumonia (16/203 cases, 7.88%), chronic interstitial pneumonia (6/203 cases, 2.96%), broncho-interstitial pneumonia (4/203 cases, 1.97%), embolic pneumonia (1/203 cases, 0.49%), adenomatosis (44/203 cases, 21.68%), atelectasis (3/203 cases, 1.48%), emphysema (1/203 cases, 0.49%) and hemorrhages (3/203 cases, 1.48%).

Incidence of ovine pulmonary adenocarcinoma in southern parts of India: A slaughter house based study

Ovine pulmonary adenocarcinoma (OPA) or ovine pulmonary carcinomatosis (previously known as ovine pulmonary adenomatosis) is a contagious tumour forming viral disease caused by the genus beta-retrovirus of retroviridae (jaagsiekte sheep retrovirus). This study was aimed to understand the prevalence of disease in the locality based on histopathological diagnosis and its correlation with age, sex and breed. Out of 903 sheep carcasses examined, OPA was recorded in 44 cases accounting to 4.87%. The gross lesions varied from multifocal greyish nodules to complete consolidation of the lung parenchyma. Histologically, there were single to multiple layers of cuboidal to columnar epithelial cells giving adenomatous appearance. The cuboidal or columnar tumour cells replaced the normal alveolar epithelia and in some cases it formed into papilliform growths that projected into the alveoli. The peribronchial and peribronchiolar lymphoid aggregates were consistent features in most of the cases studied. Argyrophilic nucleolar organizer regions (AgNORs) were counted in representative cases of nodular and consolidated forms of adenocarcinomatosis to assess the rate of cell proliferation. The average AgNOR counts per nucleus were 4.672 ± 0.68 and 3.086 ± 0.537 for nodular and consolidated forms respectively.

Cytological and immunocytological detection and differentiation of Marek’s disease and lymphoid leucosis in poultry

AbstractMarek’s disease (MD) and lymphoid leucosis (LL) are the major diseases causing lymphoid tumors in chickens accounting for high economical losses. Gross examination could not yield definite diagnosis owing to their similar presentation of lesions. Thus present work was aimed for diagnosis and differentiation of MD and LL by utilizing simple cytology and novel immunocytology techniques. Cytological examination was carried out on slides with tumor touch imprints stained by simple Giemsa staining. The diagnosis was mainly achieved based on morphology of cell population. In the present study, out of a total of 595 cases examined, 502 cases had pleomorphic lymphocytic cell population suggestive of MD and 53 cases had uniform lymphocytic/lymphoblast cell population suggestive of LL, while the rest 40 cases remained inconclusive. A definitive diagnosis was achieved after performing immunocytology using specific antibodies that revealed 518 cases had reactivity for Meq oncoprotein specific for MD and 77 cases showed immunoreactivity for IgM in transformed B-cells confirming LL. The technique of immunocytology which has been useful for detecting human viral pathogens and MD in poultry has been applied for the first time as a novel, simple, rapid and inexpensive technique that could be used as an alternate test to effectively detect and differentiate MD and LL in poultry.

Pathological and molecular studies of the renal trematode Paratanaisia bragai in Indian peafowls (Pavo cristatus)

Endoparasitic diseases are commonly encountered in free-ranging birds. Although not all endoparasites cause disease, persistent infection with large numbers of parasites almost always affects normal physiological functions, leading to deleterious effects on the host. This paper describes the anatomopathological alterations caused by the renal trematode Paratanaisia bragai in Indian peafowl (n = 3) and examines the phylogeny of these and related parasites. Peafowl from forests in and around the Bareilly region, Uttar Pradesh, India, were necropsied, and microscopic and molecular investigations were performed. The peafowl were confirmed to be infected with P. bragai. Significant gross pathological lesions suggested nephrosis, and microscopic findings indicated a mild-to-moderate degree of nephrosis caused by the parasites in the tissue. The parasites were identified as P. bragai by histomorphological analysis of adult and eggs in the ureters, and the identification was confirmed by PCR and phylogenetic analysis. Nucleotide sequencing of the PCR products from the renal trematodes recovered from Indian peafowl revealed a close association with P. bragai from Columbiformes in the United Kingdom and Spain. The pathology and molecular epidemiology of parasitic diseases affecting peafowl is not well understood in India. This is the first report from India and the second report worldwide to document P. bragai infection in peafowl.

Baruscapillaria obsignata: a serious cause of enteropathy and high mortality in turkeys (meleagris gallopavo)

ABSTRACT Background: Capillariasis, an important parasitic disease of birds is caused at least by seven different genera of trichurid nematodes with clinical outcome ranging from mild enteritis to high mortality. Objective: This study was aimed to investigate the causative agent involved in high mortality associated with severe enteric illness among turkey flocks in an organized commercial poultry farm at Bareilly, India. Materials and Methods: Turkey carcasses (n = 119) and fecal samples from the affected deep litter pen constituted as the study materials. The disease was investigated by systematic necropsy, direct microscopy and histopathology. Representative samples were screened for other enteric pathogens. Results: Microscopic examination of mucosal scraping revealed capillarid worms and their eggs in all the samples. The morphological features of adult worms were typically consistent to Baruscapillaria obsignata. Histopathology exhibited thickened muscular and mucosal layers, mononuclear and heterophilic infiltration in the lamina propria, blunting and clubbing of villi, epithelial denudation and sections of capillarid worms. Administration of levamisole at 80 ppm in drinking water reduced the mortality, clinical illness and worm load after three days of therapy. Conclusions: The capillarid worms in different avian hosts can cause different clinical manifestations and outcomes. From India, this is the first report describing intestinal pathology caused by B. obsignata in turkeys. We conclude that the B. obsignata infection is capable of causing life threatening enteropathy in turkeys and, hence, routine screening, scheduled deworming and good litter management are crucial to control the infection and its associated loss.

Effect of Aloe vera Gel Extract on the Haematological Parameters in White Leghorn Chicks Vaccinated Against Infectious Bursal Disease Virus

1Immunology Section, ICAR-Indian Veterinary Research Institute, 2Avian Diseases Section, Division of Pathology, ICAR-Indian Veterinary Research Institute, 3Division of Biological Standardization, ICAR-Indian Veterinary Research Institute 4Division of Physiology and Reproduction, ICAR-Central Avian Research Institute 5Division of Animal Reproduction, ICARIndian Veterinary Research Institute 6Division of Veterinary Biotechnology, ICARIndian Veterinary Research Institute, Izatnagar, Uttar Pradesh 243 122, India.