Hepatitis - Birds

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Introduction

Hepatitis refers to inflammation of the liver which can lead to gross lesions visible at necropsy.

In birds, these lesions are seldom diagnostic, as numerous infectious diseases cause hepatitis. Liver inflammation usually occurs alongside systemic infection and changes in other organs such as the spleen and lungs may be helpful in obtaining a diagnosis.

Histopathology can usually be more revealing, especially if special stains are used. Electron microscopy, viral isolation, DNA probes and special cultures can be used to get an exact aetiological diagnosis.

Most causes of hepatitis are difficult to diagnose in the live bird, unless the enlarged liver causes abdominal distension or biochemical tests produce significant results.

Common causes of hepatitis are as follows:

Viral Infections

Psittaciformes

Pacheco's disease caused by a herpesvirus
Avian polyomavirus
Acute Psittacine Beak and Feather Disease
Adenovirus inclusion body hepatitis
Reovirus-associated hepatitis

Falconiformes

Inclusion Body Hepatitis

Columbiformes, Strigiformes and others

Herpesvirus

Anseriformes Goose Virus Hepatitis

Galliformes Mareks Disease

Bacterial Infections

Gram-positive and gram-negative bacteria can cause liver disease, usually secondary to septicaemia or enteritis.

Gram-positive

Staphylococcus and Streptococcus species are the most common organisms isolated. They disseminate through the blood from chronic necrotising skin lesions or can reach the liver by extension from adjacent air sacs.

Clostridia are of intestinal origin and can cause hepatitis.

Listeria monocytogenes can also cause disease, although it is a rare pathogen of birds.

Gram-negative

These are the most common causes of systemic bacterial infection.

Members of the Enterobacteriaceae, including E. coli, Klebsiella, Proteus, Salmonella, Yersinia and Enterobacter are common isolates.

This is usually secondary to invasion from the gut or extension up the biliary tree.

Mycobacteria

M. avium infects all birds.

Intracellular bacteria

Chlamydophila psittaci causes psittacosis and hepatomegaly with yellow foci of necrosis.

Fungal Infections

This is usually from extension from the lungs or air sacs, or as a result of haematologic spread.

Aspergillus species most commonly affect the liver.

Systemic Candida infection, particularly in immunosuppressed birds, can also result in liver invasion.

Parasites

Apicomplexa: Toxoplasma gondii and Sarcocystis

Hemoprotozoa: Plasmodium, Leukocytozoon and Hemoproteus

Sarcomastigophora: Trichomonas gallinae infections which become generalised, Histomonas meleagridis which is predominantly a disease of turkeys.

Microspora: Encephalitozoon hellem

Toxic Hepatitis

Ingestion of heavy metals such as lead or zinc.

Vitamin D toxicity

Mycotoxins such as Aflatoxins

Idiopathic

Chronic-active hepatitis, or cirrhosis, is common in psittacine birds, particularly parrots, cockatiels, mackaws and budgerigars. The cause of the hepatitis cannot be determined due to the chronicity of the lesions.


Hepatitis - Birds Learning Resources
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Flashcards
Test your knowledge using flashcard type questions
Avian Medicine Q&A 11


References

Samour, J. (2000) Avian Medicine Elsevier Health Sciences

Schmidt, R. (2003) Pathology of pet and aviary birds Wiley-Blackwell

Doneley, R. (2010) Avian medicine and surgery in practice Manson Publishing




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