Inclusion Body Hepatitis and Hydropericardium Syndrome or Hydropericardium Hepatitis Syndrome-an Emerging Poultry Disease
Das T1*, Das NK2 and Mallick S1
1 Scientist, ICAR-NIFMD-ICFMD, Bhubaneswar
2BVO, Bisoi, Mayurbhanj, FARD, Government of Odisha
*Corresponding author E mail id: tarenisahoo@gmail.com
Inclusion body hepatitis and hydropericardium syndrome or hydropericardium hepatitis syndrome caused by FAdV are currently considered as emerging poultry disease causing high mortality among 3-5 weeks old broiler birds and severe economic losses to poultry industry worldwide. FAdVs are widely distributed. They are transmitted mechanically, vertically and horizontally. HPS/HHS is associated with higher mortality in broiler birds compared to IBH. Coinfection with other immunosuppressive viruses like IBD, CAV, Marek’s Disease virus etc. significantly worsen IBH-HPS severity. Hepatomegaly, hepatic necrosis with presence of intranuclear inclusion bodies in hepatocytes are important lesions in IBH and in addition, in HPS, hydropericardium is a pathognomonic lesion. Clinical signs, necropsy findings and molecular methods like PCR/ Real Time PCR are considered two golden standards for disease diagnosis. Proper husbandry practices, strict biosecurity measures as well as vaccination with autogenous inactivated vaccine are crucial for prevention and control of the disease. Recently, recombinant subunit vaccine/ recombinant chimeric vaccine has been developed using different serotypes of FAdV which are highly protective against IBH-HPS.
Introduction
In India, poultry keeping is 5000 years old and presently, one of the fastest growing segments of both rural and urban agriculture sector. The poultry population in India is 851.81 million in 2019 (20th Livestock Census). The production of eggs is rising at the rate of 10.19% and poultry is contributing 50.50% of meat production in India. Today, India is the world’s 3rd largest egg producer, 5th largest poultry producer and sixth largest poultry meat producer. The growth in poultry industry in India is marked by increase in number and size of poultry farms. Our poultry industry is facing various challenges. The morbidity and mortality due infectious and non-infectious diseases in chickens may disrupt the economy and lead to disastrous consequence. It causes severe losses to poultry industry by causing mortality, immune suppression, decreased feed conversion, poor growth rate, reducing meat quality, reducing egg production etc. among various diseases, Inclusion body hepatitis and hydropericardium syndrome has become one of more common impediment to growth of broiler industry leading to heavy economic loss and reduced body weight gain. In addition, its immunosuppressive attribute further complicates with secondary infection and loss.
Aetiology
Inclusion body hepatitis (IBH) and hydropericardium syndrome (HPS) or hydropericardium hepatitis syndrome (HHS) is caused by Fowl Adenovirus which is a non-enveloped double stranded DNA icosahedral virus with 60-80nm diameter and 35,000 bp genome length belonging to Genus Aviadenovirus and Family Adenoviridae. It is classified into five different species (A to E) based on molecular structure and 12 different serotypes depending upon cross neutralization test and melt curve analysis (Cizmecigil et al., 2020). IBH is caused by FAdV-2 and 11 (Species-D) and FAdV-8a and 8b (Species-E). HHS/ HPS is caused by FAdV-4 (Species-C).
History and transmission
IBH was first detected in the poultry population of North America in 1963 (Helmboldt and Frazier, 1963). In Asia, HPS was first reported in Angara Goth, Karachi, Pakistan with accumulation of straw-coloured fluid in the pericardial sac along with hepatitis and was named as Angara disease (Jaffery et al., 1988). In India, HPS was detected in the poultry belt of Jammu and Kashmir, Punjab, and Delhi in 1994 and named as Leechi disease due to characteristics appearance of peeled Indian leechi (Gowda et al., 1994). There are several reports on IBH-HPS outbreaks in India from different states like Uttar Pradesh, Maharashtra, AP, Karnataka, Kerala, Tamil Nadu, Odisha, West Bengal, Assam, Mizoram etc. (Asthana et al., 2013; Suohu and Rajkhowa et al., 2021).
The disease is mostly seen in 3-5 weeks old broiler birds, occasionally reported in broiler breeders and commercial layers of less than 20 weeks old in milder with 10% mortality (EI-Shall et al., 2022). Pan et al., 2017 reported HPS in 180 days old layer birds with 50% mortality. There are also reports of FAdV-4 associated HHS in ducks under natural condition (Yu et al., 2018). The virus is transmitted vertically through eggs from parent birds to progeny which is an important feature of fowl adenovirus. The infected breeder bird transmits FAdV to their progeny for 3-6 weeks until development of immunity. Virus can be transmitted by infected hatching eggs from one region to another region. The FAdVs are transmitted bird to bird in a flock horizontally by oral -faecal route because of high shedding of virus in the faeces. Contamination with infected faeces also spreads virus further.
Pathogenesis and clinical signs
The incubation period of the disease is 5-18 days. FAdVs have affinity for hepatic cells, endothelial cells as well as lymphoid organs like spleen, thymus, bursa of Fabricius, caecal tonsil etc. resulting in severe immune suppression. The pathogenicity of FAdV was found to be enhanced by infectious bursal disease virus (IBD), chicken anaemia virus (CAV), mycotoxin etc. HPS is more dangerous than IBH as it causes significant mortality in broiler birds. PX, a structural protein of FAdV-4 was reported to induce apoptosis in Leghorn hepatocellular cells resulting in liver injury.
IBH is characterized by sudden onset of mortality peaking at 3-4 days of post infection, stopping at day 5th or may continue to 2-3 weeks with 10-30% mortality. Sick birds exhibit crouching position with ruffled feathers and less meal intake (El-Shall et al., 2022). Anaemia and jaundiced appearance of skin and skeletal muscle have been described. HPS is also characterized by sudden onset of mortality, lethargy, huddling with ruffled feathers and yellow mucoid droppings with 20-80% mortality.
Gross and microscopic pathology
Grossly, the affected livers are pale, friable, and enlarged with presence of minute necrotic foci and petechiae to ecchymosis haemorrhages. Swollen kidneys, atrophic thymus/ bursa, aplastic bone marrow have been reported. In HPS, hydropericardium is pathognomonic with presence of straw-coloured fluid in the pericardial sac with occasional coagulation of fluid giving rise to cloudy appearance. Pulmonary oedema, hepatitis and pale enlarged reticulated kidneys with dilated tubules are observed in HPS. Ascites and pancreatic necrosis have been reported in severe epidemics. Haemorrhages in skeletal muscles and swollen congested spleen with petechiae have been reported (Das et al., 2015; Dutta et al., 2017).
Intranuclear inclusion body in liver hepatocytes is the hall mark for FAdV infection which has been documented in both IBH and HPS cases. Thickening of Glisson’s capsule, vascular congestion, sinusoidal congestion, fatty alteration, cloudy swelling, hepatocyte degeneration, multifocal coagulative necrosis with inflammatory cell infiltration etc. have been observed. In kidney, interstitial lympho-plasmocytic nephritis and glomerulonephritis are observed. In lung, congestion, haemorrhage, oedema of pleura and parenchyma have described along with mononuclear infiltration. In heart, myocarditis, haemorrhage, mononuclear infiltration has been reported. In spleen, lymphocyte depletion, RE cell proliferation, congestion and haemorrhage are observed. In BF, lymphoid depletion, haemorrhage and follicular atrophy are seen (Das et al., 2015; El-Shall et al., 2022).
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| Fig. 1. Photograph showing hepatomegaly with hydropericardium in a chick |
Diagnosis
The traditional method for laboratory diagnosis of IBH-HPS includes clinical signs like sudden onset of mortality among 3-6 weeks broiler birds; necropsy findings like pale, enlarged friable liver and hydropericardium; and histopathological findings like intranuclear inclusion bodies in hepatocytes (Das et al., 2015). Other diagnostic tests like serological techniques including indirect immunofluorescent assay, ELISA, neutralization test, Double immunodiffusion, indirect haemagglutination test, agar gel immunodiffusion test, counter immune-electrophoresis, fluorescent antibody technique etc. are used to detect IBH-HPS virus infection in poultry (Asthana et al., 2003; McFerran and Adair, 2003; Bisht et al., 2022). The virus particles can be demonstrated by transmission electron microscopy (Asthana et al., 2003; Chandra et al., 1997). Virus isolation can be carried out in chicken embryo liver cell culture or chicken embryo kidney cell culture (Kumar et al., 2003). The virus can be propagated in 7-8 days old specific pathogen free chicken eggs via yolk sac route and chorio allantoic membrane route or can be propagated in embryonated duck eggs (Cheema et al.,1989; Mahmood et al., 1995). Immunohistochemistry, immunofluorescence method and in situ PCR can be used to detect virus particles in the tissue samples like liver and heart (Alcigir and Vural et al., 2013). Molecular techniques for detection of IBH-HPS includes conventional PCR targeting L1 loop in hexon gene, sequencing, and phylogenetic analysis (Chitradevi et al., 2021; Naguib et al., 2021). Real time PCR with high resolution melting curve analysis and SYBR green based Real Time PCR have been described for detection and quantification of FAdV (Steer et al., 2009; Gunes et al., 2012). PCR-Restriction fragment length polymorphism has been developed for differentiating different strains of FAdV-4 (Mase et al., 2010). A sensitive triple nano-particle assisted PCR assay has been developed for detection of FAdV, IBD and CAV (Luan et al., 2022).
Prevention and control
The key strategy for prevention control and control of IBH-HPS is proper husbandry and biosecurity practices like cleaning and disinfection of equipment and premises, restriction to entry of visitors, sufficient poultry house ventilation and lighting etc. The affected flock can be isolated and treated properly with diuretics, liver tonics, haematinics and vitamin -E for improving general health of birds (Kataria et al., 2013). The addition of 2.5% iodophor disinfectant to drinking water @0.07%-0.1% has been found to be very effective in reducing severity and course of the disease (Abdul-Aziz and AI-Attar, 1991). Immunization with autogenous inactivated vaccine prepared from prevalent serotype is recommended for prevention and control of disease in particular region. In India, inactivated oil emulsified anti IBH-HPS vaccine prepared from FAdV propagated in cell culture was reported to provide protection within first week of vaccination (Kataria et al., 1997). Formalinised inactivated vaccines prepared from HPS isolate propagated in chicken embryo kidney cell has been found to be 100% protective in broiler birds (Gupta et al., 2005). In India, only oil emulsion vaccines are used only when outbreak is suspected, not regularly (Kataria et al., 2013). In our country, HP Vac, one of the licenced vaccines composed of oil emulsified killed FAdV-4 is available and is manufactured by INDOVAX Pvt. Ltd (Shah et al., 2017). In recent year, first novel single component recombinant chimeric fibre protein vaccine prepared from combining epitopes of FAdV-4 and 11 has been found to be highly protective against IBH and HPS (Luca et al., 2022). A potential bivalent inactivated novel chimeric FAdV-4 containing fibre-1 of FAdV-8b vaccine has been developed and found to provide protection against FAdV-4 and 8b (Wang et al., 2022) which can be used for effective control and prevention of IBH and HPS.
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