Diagnosing Poultry Diseases: Symptoms, Causes & Treatments

Diagnosing what ails an animal is an art that is based on evidence, not mere guesswork. Like people, farm animals often exhibit changes in behavior and appearance when something is wrong. Successful poultry farmers closely monitor their flocks for any signs of disease and come to recognize the symptoms of many common ailments through this observation.

However, for some diseases, there may be no observable symptoms initially, and their presence must be determined through specialized procedures, including laboratory tests.

For example, a chicken that experiences bloody stools, refuses to eat or drink, and loses weight might have Coccidiosis, but further evaluation is necessary to make a more accurate diagnosis.

It's worth noting that some diseases appear only at specific times of the year, and others affect only young birds. When diagnosing a potential illness, it's important to consider the presence of the disease in the surrounding area and whether any new birds have been recently introduced to the farm.

Usually, the first signs of disease are very slight but noticing these early symptoms before serious ones appear helps greatly in the control of diseases. Animals recover more quickly when given care and treatment at the onset of the sickness. What is more, the spread of disease can often be stopped if a sick bird is at once separated from the rest of the flock.

(a).  The Meaning of Symptoms

A symptom is a physical or mental characteristic that is considered to be indicative of an illness. The symptoms of various diseases can vary between birds of the same species, and a specific ailment may exhibit different symptoms in different bird species.

If one or more signs of illness are observed, a more comprehensive examination of the affected birds should be conducted. In most cases, it is unwise to make a final diagnosis until all factors that may impact the health of the flock have been taken into account.

Only a few symptoms point to disease of particular parts of the body. Most symptoms are general.

When a part of the body is ill, symptoms can appear in other areas as well, similar to an upset stomach causing a headache and making a person feel sick all over. Symptoms, however, are not a disease in and of themselves; they simply indicate the presence of a disease.

The goal of diagnosis is to determine the cause of the symptoms. Many illnesses have similar symptoms, and relying solely on symptoms can lead to misdiagnosis.

The common practice of farmers buying medicines without a veterinarian's prescription can result in incorrect treatment. Efforts should be made to have a qualified animal health practitioner visit the farm for a more accurate diagnosis.

If birds aren't eating as expected, it may be due to an intestinal disease or moldy feed. But even a sudden change in feed or poor beak trimming can cause symptoms similar to those of an infectious disease.

When conducting an examination, it's advisable to start with the simple things. This way, you can quickly determine what's causing a sick bird's illness. You can then verify your findings by looking for additional symptoms to confirm the presence or absence of a specific disease.

(b). Noting the General Behavior

When a bird exhibits behavior that is contrary to its normal tendencies and appears abnormal, it often indicates the onset of illness. Therefore, a competent diagnostician needs to be familiar with the typical appearance and behavior of healthy birds. This is the only way for them to recognize deviations from the norm.

Signs of a Healthy Bird:

1. It stands in an erect position with its head and tail elevated.
2. Its combs and wattles should be bright red.
3. The facial parts should be well-filled out.
4. The eyes are bright, alert, and not blinded.
5. No discharges should come out of the eyes.
6. The nostrils should be clean, without discharges.
7. The feathers are smooth, clean, and neat.
8. It should have normal legs with joints that are smooth and cool to the touch.
9. The bird in the flock should have a weight that is typical for the type and age of the bird.
10.  The scales on the legs and feet should be clean and waxy in appearance
11. Movement should be normal, without limping or inability to walk.
12. It should have the skin color characteristic for the breed and strain of the bird, as well as the age.

NOTE:

Birds that are very sick usually look very drowsy, with their eyes half closed, their wings droop, have rough feathers, and seem to move only with great effort. They may huddle on the roost or floor.

How to diagnose poultry diseases based on symptoms and general behavior:

1. Neck twisting and paralysis:

A bird that twists its neck could be suffering from Newcastle Disease, Fowl Cholera, a brain infection, or an improper injection of Marek's Disease and Botulism. If the neck is retracted over the back, it is likely a sign of a nutritional (vitamin) deficiency or possibly Newcastle Disease once again.

2. Loss of weight, shape, and size:

In diseases that cause a rapid decline in health, birds exhibit a dejected appearance with dull eyes and blank expressions. The loss of weight, shape, and size can be attributed to a lack of feeding, nutritional deficiencies, lymphoid leucosis, gizzard impaction, and worm infestations.

Stunted and uneven growth can still result from gizzard impaction, overcrowding, inadequate feeding, blue comb disease, aflatoxin poisoning, and joint inflammation.

3. Feather condition (feather pecking, feather eating, and feather picking) :

Feather pecking, eating, and picking may be caused by, amongst other factors, a nutritional deficiency (methionine). This could also suggest that the birds have not been de-beaked. The loss of feathers could be a sign of molting.

Additionally, infectious coryza can cause feathers to become moist under the wings, while deposits at the feather shafts' base may indicate the presence of lice and mite eggs.

4. Nasal discharges:

Nasal Discharges are a common symptom in infectious coryza, chronic respiratory disease, infectious bronchitis, and avian influenza (bird flu).

5. The skin:

The symptoms associated with skin conditions include excessive pigmentation, as seen in cases of poorly productive birds, and nodules, mainly on the legs, as in the case of Marek's disease.

6. Swollen faces:

Swollen faces are commonly seen in the following conditions: infectious coryza, Newcastle disease, vitamin A deficiency, colibacillosis (where the face appears darkened and purplish), and injuries. Nodules on the face may be caused by fowl pox.

7. The eyes:

 There are several eye conditions that can affect poultry. Watery eyes are often a sign of infection known as coryza. Blindness can be caused by either fowl pox or aspergillosis. Irregular pupils can indicate Marek's disease. If the eyes appear watery, red, inflamed, and frequently closed, it could be a result of Newcastle's disease, vitamin A deficiency, ammonia burns, or infectious laryngotracheitis.

Crusty eyelids may also indicate a vitamin A deficiency. Enlarged and swollen eyes are often a symptom of mycoplasma infection.

8. Leg abnormalities:

Leg abnormalities can be observed in various conditions, including Marek's disease, heatstroke, cage layer fatigue, vitamin deficiency, and acute water shortage, which can result in leg paralysis. Fowl pox causes rough and scaly legs, while scaly leg mite infestation leads to scaly legs.

Vitamin D deficiency results in bowed legs and swollen joints and can be caused by infections in joints, Pullorum disease, staphylococcal infection, and joint inflammation.

9. Swollen and bulbous wattles:

Swollen and Bulbous Wattles, Infection Coryza, and Fowl Cholera.

10. Nodes on wattles and combs:

Fowl pox

11. The mouth:

12. Death:

In many instances, how death occurs can indicate specific disease conditions. Immediate death with little to no warning signs can be caused by Fowl cholera, acute dehydration, and overheating.

A high death rate can be caused by a variety of factors, including Fowl cholera, Newcastle disease, acute coccidiosis, Aflatoxicosis, and Botulism, among others.

It is important to pay attention to the way in which death occurs in order to determine the underlying cause and take the necessary steps to prevent the further spread of the disease.

13. Egg production:

In addition to death, a decrease in egg production can also indicate certain disease conditions in poultry. Understanding the symptoms and signs of low egg production can help diagnose and prevent future outbreaks.

A sudden drop in egg production can be caused by various reasons such as Newcastle disease, Infectious bronchitis, Infectious Laryngotracheitis, Avian influenza, mismanagement, fowl cholera, chronic respiratory disease, dietary deficiencies, gizzard impaction, fowl pox, lice, mites, and worms, and lymphoid leucosis.

Lowered egg production can be a result of diseases such as Coccidiosis, Enteritis, and Aflatoxicosis.

Abnormalities in egg shape and pigmentation can also indicate health issues such as Necrotic enteritis, Infectious bronchitis, Newcastle disease, dietary deficiency, Vitamin D deficiency, and Calcium and phosphorus deficiency.

Regular monitoring and prompt treatment of any issues can help maintain a healthy flock and consistent egg production.

Note: Numerous factors may adversely affect egg production. Investigate the cause by answering the questions below;

Qn1: How old are the birds?

Young birds at the onset of laying produce fewer eggs in terms of percentage laying than older ones. They also produce smaller eggs.

Qn2: How much feed are the birds consuming daily?

If the quantity of feed consumed per bird is less than what is required (125-140g per bird), the egg will not be formed, or the egg laid will be smaller and of lower quality than expected. Overfeeding can also lead to lowered egg production.

Qn3: Has there been a change in the type of feed?

Make sure the feed is well-balanced in terms of energy and protein content. The feed texture should not be changed. Make sure the feed is not moldy.

Qn4: How much light do the birds receive daily?

Laying birds should receive additional lighting to natural light. A lighting period of 16 hours per day is recommended for laying flocks. At the end of natural daylight, switch on artificial lights and switch them off between 10 pm and 11 pm. The "increased day length" stimulates egg production.

Qn5: What is the condition of the birds?

Make sure the birds are healthy and comfortable. Look for possible disease symptoms and signs. Find out if the birds are active or not.

Qn6: What is the shell quality like?

Qn7: What about the interior egg quality?

Qn8: Are the birds crowded?

Qn9: Are there any signs of both internal and external parasites?

Qn10: Are you sure about the number of birds in each flock?

NB: Avoid overcrowding and know the production of every flock.

Qn11: Are there enough drinking facilities, feeders, and laying nests?

Qn12: Are there any stress factors that could be affecting production now and recently?

14. Droppings:

Always take note of the appearance of droppings. If they are abundant, it could indicate an issue with intestinal health (such as enteritis) or a diet high in roughage.

If you observe blood in the droppings, one of the possible causes could be caecal coccidiosis, or, to a lesser extent, Newcastle disease.

If feed intake is low, you may also notice green droppings. Sulfur-yellow droppings are common in birds with blackheads, while light yellow or yellowish-green droppings are a common symptom of fowl cholera.

Intestinal parasite (protozoa) infestation typically results in foamy droppings.

15. Look at the feet of birds:

If the joints are stiff and the birds struggle to bend their legs, it is a sign of a problem with the tendons that hold the joints together. This condition is known as tenosynovitis.

The bird may also walk on its toes, and if the bottom of its feet is swollen, it may have a staphylococcus infection known as bumble foot.

When the toes are curled, the most common cause is a deficiency in riboflavin (vitamin B2); however, it could also be a result of genetics or poor management.

History

Diagnosis of poultry diseases based on history

Qn1: Is there a history of recent farm activities and relevant events that could relate to the presence of the condition at hand?

Qn2: How about management shortfalls like lack of feed, water provision, and vaccination failure?

Qn3: What about the feeding practices being undertaken?

Qn4: How is the feed formulated and mixed?

Qn5: Any recent disease outbreak in the neighborhood?

Qn6: Where were the chicks sourced from? (Your source of day-old chicks).

Qn7: What treatments and vaccinations have been administered to the flock?

Qn8: What quantity and quality of feeds are your birds receiving?

NB:

All the above and other relevant historical information can provide useful leads to the possible cause of disease.

Observations

Observe and assess the suitability of the housing units. The ventilation should be sufficient, and the roof should be leak-proof. The floor should be in good condition with proper litter, and cracks in the walls should be filled to prevent the hiding and multiplication of disease-causing organisms. The litter on the floor should be of the required density (thickness).

If the birds are still in the brooder, assess the temperature, feeding, and water provision. Overcrowding should be avoided, and high-quality feeds rich in protein, such as pellet starter or chick mash, should be provided. Moldy feeds should be avoided, and poultry feeds should be stored properly.

Proper premixes and feed additives should be used in feed mixing, and quality feed ingredients should be utilized.

Evaluate the treatments, vaccinations, feeding, egg production, and record keeping.

Finally, assess the quality of eggs laid and the weight of the birds.

Differential Diagnosis

The symptoms of several diseases are sometimes so much alike that it is hard to tell them apart. Even veterinarians with years of experience have this difficulty now and then. The differences in symptoms are there, alright, but they are so slight that they cannot easily be differentiated.

Such situations call for what is known as "differential diagnosis". This merely means that you use greater care and often more technical methods to find more symptoms and to find any differences among symptoms already found. You differentiate between the diseases that might be present.

Sometimes a slight difference in symptoms will be a clue to the nature of the disease.

The rapidity of the onset of the disease, the number of birds affected, and the death rate are valuable aids in diagnosis. If many birds suddenly fall sick, the cause is more probably an infectious disease or poison. Other symptoms make it easier to tell whether or not this is a suspected cause.

Symptoms of a disease sometimes change or new ones are added, and the sickness progresses. For this reason, it is helpful to know when the first signs of the disease appeared and how long it took for the later symptoms to develop. The speed with which a disease reaches a climax is often a clue to its nature.

Performing An Autopsy (POST-MORTEM)

Whenever there is any doubt about the presence of a serious disease, post-mortem examinations should be made, and affected body organs should be sent to a competent laboratory for examination. Autopsies can be done on carcasses or live animals.

When a suspected disease is dangerous to humans, such as Avian influenza (bird flu), special care should be taken to guard against infection. In any case, it is better to leave the examination to someone with veterinary or medical training. Never open the carcass of such cases, or else you may contaminate your premises.

Autopsies should be made as quickly as possible after death. Decomposition of the carcass starts early, especially in warm weather. If you wait, the changes in the body organs caused by decomposition may be mistaken for disease symptoms.

Conclusion

In conclusion, understanding the behavior and symptoms of sick chickens is crucial for maintaining a healthy flock and preventing the spread of diseases. By observing their general behavior, such as changes in appetite, activity level, and appearance, we can identify potential health issues early on and take appropriate measures to protect the rest of the flock.

It is also important to note that some diseases have specific signs and symptoms that require immediate attention. Regular monitoring, proper hygiene practices, and seeking veterinary assistance when necessary are essential for the well-being and longevity of your poultry flock.