Article originally written by Roshan Poudel…..B.V.Sc and AH..IAAS,Paklihawa
Gout is a metabolic disease characterized by deposition of urates on the surfaces of various internal organs, or various joints. It is a very common finding during postmortem examination of poultry, and can be a source of great economic loss to the farmer. Birds usually die from kidney failure. Both in broiler and layer chicks, gout can be seen from 4th day onward and can be a serious problem between 2nd and 3rd week. In layers, though relatively rare, gout can be seen even up to 50th week, and is mostly of nutritional origin
Types of gout
- Visceral gout – deposition of uric acid crystals in visceral organs like kidney, liver, heart and gut. It is the acute and more common form of gout reported in poultry. It causes huge mortality in poultry ranging from 15-35 per cent. It is observed in young poultry.
- Articular gout – deposition of uric acid crystals in joints, ligaments and tendon sheath. It is chronic form of gout and has some genetic predisposition. It is rarely seen in poultry.
In both forms, deposits consist of white chalky needle shaped shiny crystals called ‘tophi’. In gout, blood levels of uric acid can be as high as 44mg/100ml as compared to 5-7mg/100ml in a normal bird
Causes of gout
1. Lack of water, or inadequate supply of water (dehydration).
2. Inadequate number of drinkers, or even just overcrowding.
3. Excess of dietary calcium, or calcium:phosphorus imbalance, or low intake of phosphorus in relation to calcium.
4. Increased intake of protein.
5. Vitamin A deficiency.
6. Excessive amount of salt (sodium chloride).
7. Infection with certain kidney damaging strains of infectious bronchitis virus in young chickens.
8. Fungal toxins (mycotoxins), such as oosporein and ochratoxin.
9. An electrolyte excess or deficiency.
10. Treatment with sodium bicarbonate
Uric acid is the end product of purine and protein metabolism in poultry. Uric acid is formed in the liver and excreted by kidneys. Birds are uricotelic, lack the enzyme uricase and this along with the process of water conservation, allows them to excrete urine in the form of semi-solid uric acid in the faeces.
Disruption in the metabolic process of excretion of uric acid leads to gout. So gout can arise either due to production of uric acid over the capacity of kidneys to excrete it, or due to compromised kidney function failing to excrete the produced uric acid
An elevated serum urate level, together with local factors, can result in the deposition of urate crystals into the joints. Once crystals are deposited into a joint, they can be released into the joint space and initiate an inflammatory cascade causing acute gouty arthritis.
I. Presence of white chalky deposits on the surfaces of heart, liver, kidneys, proventriculus, and lungs. These deposits are seen as white chalky coating
2. The chalky deposits first begin on the heart and then spread
3. Kidneys are swollen, congested, and typically gouty (greyish white in colour) .
4. One or both ureters may be distended with white material.
5. In the articular gout, when joints are opened, the tissue surrounding the joints is white due to urate deposition
- Joint fluid test. Your doctor may use a needle to draw fluid from your affected joint. Urate crystals may be visible when the fluid is examined under a microscope.
- Blood test. Your doctor may recommend a blood test to measure the levels of uric acid and creatinine in your blood. Blood test results can be misleading, though. Some people have high uric acid levels, but never experience gout. And some people have signs and symptoms of gout, but don’t have unusual levels of uric acid in their blood.
- X-ray imaging. Joint X-rays can be helpful to rule out other causes of joint inflammation.
- Ultrasound. Musculoskeletal ultrasound can detect urate crystals in a joint or in a tophus.
a.Pseudogout (calcium pyrophosphate deposition disease)
The definitive diagnosis is finding calcium pyrophosphate crystals in the synovial fluid. These are rhomboid-shaped, weakly positively birefringent crystals.
Chondrocalcinosis (radiographic calcification of cartilage in certain joints) is usually present.
Synovial fluid is usually bloody and has no monosodium urate crystals.
X-rays may show soft-tissue swelling
Synovial fluid microscopy and culture may be gram positive and show growth
Blood cultures may grow the causal bacteria
Synovial fluid is inflammatory, but no monosodium urate crystal are found