Five Stages of Chickens Catching a Cold
In recent years, avian influenza has swept across the globe, forcing many farms to prematurely sell their flocks and incurring heavy losses. However, upon closer examination, the initial trigger for many previously healthy flocks was often not the influenza virus itself, but rather a seemingly minor oversight in ventilation management—the flock catching a cold. Initial symptoms were mild and easily overlooked, or even when attention was given, inappropriate medication or inadequate management led to a rapid escalation of the disease. By the time mortality rates soared, the optimal window for control had passed.
To help you accurately time your intervention, we have divided the entire process of a flock catching a cold into five progressive stages. Please check against these stages to identify your flock’s current stage—the earlier the identification, the higher the cure rate and the smaller the losses.
Phase 1: Initial Stage of Cold Exposure
This is the stage with the highest cure rate, but also the most easily overlooked.
External Symptoms:
Chickens exhibit mild coughing, nasal shaking (head shaking), tearing, and clear nasal discharge, accompanied by a “wheezing” sound (similar to phlegm in the throat). The most typical symptom is: when the temperature drops in the morning and evening, the chickens are noticeably lethargic, tucking their heads in and ruffling their feathers; however, when the temperature rises at noon or in the morning, their mental state “returns” to normal, giving the false impression that they are about to recover. At this time, feed intake decreases slowly, or even does not decrease, easily leading to a loss of vigilance.
Necropsy Findings:
Swelling of one or both infraorbital sinuses (nasal sinuses), and redness of the eyelids. Slight bleeding is present in the larynx and the anterior third of the trachea, and a small amount of clear, foamy mucus is visible in the trachea. No obvious lesions are found in other organs.
Treatment Recommendations: Timely and appropriate medication at this stage has an extremely high cure rate. Immediately improve ventilation in the coop to prevent cold drafts from blowing directly on the chickens. At the same time, administer medications to relieve cold symptoms caused by wind-cold and provide emergency immunization with attenuated vaccines or antibodies.
Phase 2: Upper Respiratory Tract Infection
If the first phase is not effectively controlled, the disease continues to progress, with the infection spreading deeper into the trachea from the larynx.
Main Manifestations:
Tracheal inflammation worsens, and the mucus secreted in the trachea increases significantly and becomes thicker, no longer the clear, frothy substance. At this time, the chickens’ coughs will sound more muffled and moist (with phlegm). The core task of treatment at this stage is to stop the cough and dissolve the phlegm, helping the chickens expel inflammatory secretions and prevent airway obstruction.
Treatment Recommendations: Administer bronchodilators and phlegm-thinning medications promptly (such as ammonium chloride, bromhexine, etc.), combined with anti-inflammatory drugs. Simultaneously, it is essential to raise the coop temperature by 1-2°C and reduce temperature fluctuations.
Phase 3: Pneumonia
Entering this stage signifies that the disease has progressed from superficial symptoms to deeper involvement, with substantial lesions appearing in the lungs.
External Symptoms:
The flock exhibits significant lethargy, drowsiness, and worsening respiratory symptoms (increased coughing and wheezing). Feed intake decreases markedly. Mild edema begins to appear on the head and face, and fever becomes pronounced.
Nectomy Findings:
The lungs show a “pancreatic” appearance (resembling cooked edema, grayish-white in color), with congestion and blackening. Due to high fever and inflammation, the gallbladder is dilated, filled with bile, and may even necrotize. Some chickens begin to develop pericardial effusion (clear or pale yellow fluid). At this stage, it is crucial to forcefully reduce the fever; otherwise, any subsequent drug treatment will be significantly less effective.
Treatment Recommendations: In addition to antipyretics (such as carbaspirin calcium or acetaminophen), administer antibiotics sensitive to mycoplasma and E. coli. Simultaneously, improve ventilation in the chicken house, but avoid excessive airflow.
Phase 4: Cardiopulmonary Dysfunction
Often, by the time farmers truly begin to panic, the flock has already reached this stage. Pneumonia overloads the cardiopulmonary system, leading to cardiac dysfunction.
Main Manifestations:
The primary characteristic is increased pericardial effusion, weak heartbeat, and obstructed blood circulation. Lung congestion worsens, causing hypoxia. More chickens stretch their necks and pant, and some exhibit abdominal breathing. At this point, even with increased medication, mortality rates begin to rise.
Treatment Recommendations: At this stage, medication alone is insufficient to reverse the progression. It is essential to combine this stage with cardiotonic and hepatoprotective drugs (such as vitamin C and taurine), strictly control secondary infections, minimize stocking density, and reduce stress.
Phase 5: Systemic Infection and Circulatory Disorders
This is the terminal stage of chicken influenza, commonly known as severe airsacculitis, pericarditis, perihepatitis, and bronchial obstruction complex.
External Symptoms:
Severe edema of the head and face; numerous chickens stretch their necks and breathe with open mouths, emitting sharp, strange cries (indicating severe tracheal obstruction). Feed intake drops drastically or even ceases completely, and mortality increases significantly.
Neotomy Findings:
Systemic inflammation: pericarditis and perihepatitis (pericardium and liver surface covered with fibrinous exudate); thickened, cloudy air sacs (cheesy appearance). In more severe cases, complete bronchial obstruction occurs (hard, rod-shaped or Y-shaped cheesy material), and cheesy emboli are also present in the lungs. All internal organs undergo degeneration; metabolic circulation in the heart, liver, spleen, lungs, and kidneys is comprehensively impaired, resulting in a dark purple appearance.
Treatment Recommendations: Treatment at this stage is extremely difficult, with a high culling rate. If most of the flock has not yet shown severe symptoms, you can try to urgently isolate the sick chickens and take a comprehensive approach to clearing heat and detoxifying, tonifying the kidneys and protecting the liver, and preventing secondary infections in the flock. However, you must be prepared to “stop the damage”.
Influenza outbreaks rarely occur out of thin air; the vast majority begin with a sudden temperature fluctuation. Remember: “Good ventilation is the first line of defense for your chickens’ immunity.”
Referring to these five stages, you should clearly understand that the first two stages are the most cost-effective and efficient “windows of opportunity.” In the third and fourth stages, the return on investment drops sharply, and the fifth stage is merely a matter of “firefighting.”
It is recommended to conduct “4 AM inspections” at least twice a week—this is the lowest temperature of the day, when chickens are most susceptible to chilling. Check for gaps in side windows, whether cold air is flowing back from fans, and whether the chickens are huddled together. Post this five-stage checklist in the chicken house duty room to help you and the staff detect problems early, make accurate judgments, and intervene quickly, preventing these “troubled times” from becoming a “disaster” for the farm.
