What are the common diseases that cause abnormal body color in chickens?

1. Staphylococcal infection

The affected areas look like bruised and contused tissue, appearing red, green, blue-black, or black depending on the degree of hemoglobin breakdown. Chronic cases involve arthritis. A definitive diagnosis requires pathogen identification.

2. Streptococcal infection

The lesions resemble those of staphylococcal infection but occur less often, and a definitive diagnosis also requires pathogen identification.

3. Monocytosis (uremia)

The muscle color is darker or more purplish than normal, and the comb and head are cyanotic. The kidneys are swollen and pale with urate deposits; in more severe cases, urate deposits are also present on the peritoneum, pericardium, and viscera. Blood smear examination shows increases in both the relative and absolute values of monocytes.

4. Acute septicemia

In some cases of septicemia, the whole body turns black, with multiple hemorrhages in the internal tissues. A definitive diagnosis requires pathogen identification.

5. Toxic cyanotic diseases

Cyanosis is caused by cardiac weakness resulting from some disease, such as toxic cardiac degeneration, pericarditis, Escherichia coli infection, or certain systemic toxemias and septicemias. A definitive diagnosis requires investigation of the cause or pathogen identification.

6. Spirochetosis

Jaundice appears throughout the body tissues, with enlargement of the liver and spleen and necrotic foci in the spleen. A definitive diagnosis requires pathogen identification.

7. Histomoniasis (cecal hepatitis, blackhead disease)

The skin of the head is often purplish-blue, and the droppings are sulfur-yellow. One or both ceca are enlarged, with thickening of the intestinal wall and attached yellow masses; ulcers are sometimes seen penetrating the intestinal wall; the mucosa is necrotic and thickened, with yellowish-green exudate; the cecal lumen is filled with a tofu-dreg-like material, often forming casts. Liver lesions are typically distinctive round, depressed structures with a yellow necrotic center.

Examination of feces or samples taken from cecal contents or liver lesion tissue can detect the pathogen, namely Histomonas meleagridis.

8. Fowl typhoid

The comb and wattles are pale and shrunken, but in severe cases with toxemia or septicemia they turn black, and the skin sometimes also turns black. Affected chickens have diarrhea and a fever as high as 43°C-44°C. Necropsy shows enlargement of the liver and spleen, possibly with grayish-white necrotic spots, and the liver often appears bronze-colored; enteritis, usually most severe in the upper small intestine; necrotic foci in the myocardium are occasionally seen; and fibrinous perihepatitis resembling egg yolk is also commonly seen. A definitive diagnosis requires pathogen identification.

9. Fowl pox

When fowl pox is severely epidemic, some cases have pox warts all over the body surface; this condition often involves secondary staphylococcal infection, and thus abnormal body surface color appears.