Diseases

Disease Management 


It is important to consider several factors that relate to the quality and health of the flock once the type or breed has been chosen. Purchase stock only from reputable breeders or hatcheries. Stock purchased from magazine advertisements, especially bargain offers, can mean serious problems later. Stock should be purchased from Pullorum-Typhoid clean flocks under the National Poultry Improvement Plan (NPIP). Pullorum and Typhoid are highly contagious diseases caused by Salmonella. NPIP breeders, hatcheries and facilities have been checked for proper management and sanitation, and the presence of seriously diseased birds. “Sources of Poultry and Supplies for Small Flocks”, published by the University of Maryland Extension, provides a partial listing of poultry, eggs, and chicks for sale and can be obtained free from your county Extension office.

Because of the similarity of many diseases, diagnosis should be left to a professional veterinarian. With an accurate diagnosis, proper treatment can be given to the flock. Maryland Department of Agriculture Animal Health Diagnostic laboratories offer diagnostic services for poultry. When there is an outbreak in the flock, take one or two birds showing typical signs to the lab. When the diagnosis has been made, treat the disease under the direction of a veterinarian or with the advice of your county Extension educator.

Respiratory diseases

Respiratory diseases affect the respiratory tract and are the most common diseases in chickens. Table 8 shows some of the common respiratory diseases; most can be prevented by good biosecurity backed up with vaccination.

Table 8. Common Respiratory Diseases
Disease Symptoms
Infectious bronchitis Rapid spread, gasping, wet eyes, coughing, swollen sinuses, drop in egg production, misshapen eggs, rough- or soft-shelled eggs, watery egg whites, death
Newcastle disease Rapid spread, gasping, rattling, loss of appetite, coughing, huddling, paralysis of legs, twisted neck (stargazer), walking backward, drop in egg production, soft or misshapen eggs, death
Laryngotracheitis Slow spread, conjunctivitis (eye inflammation), coughing, sneezing, sitting hunched on floor, emitting a cawing sound, coughing bloody mucus, nasal discharge, swollen head and wattles, drop in egg production, death
Fowl pox

Skin – white to yellow bumps on comb, face or wattles, turning to scabs
Internal – cankers in membranes of mouth, throat and windpipe; difficult breathing; nasal or eye discharge

Coryza Thick nasal discharge with odor, swollen sinuses, ruffled feathers, difficult breathing
Mycoplasma Difficult breathing, ruffled feathers, nasal discharge, rattling, facial and nasal swelling, weakness, drop in egg production, swollen joints, yellowish feces
Cholera Droopiness; difficult breathing; loss of flesh; drop in egg production; purplish swollen head, comb and wattles; paralysis

Highly pathogenic transmissible diseases, such as Exotic Newcastle and Avian Influenza, can be avoided with proper management and biosecurity measures.

Marek's disease

Marek's disease is one of the most common killers of chickens of all ages. Marek's disease is caused by a Herpes virus that often accumulates in the feather follicles and spreads by aerosol through infected dander (sloughed skin and feather cells).
Another tumor-causing disease of chickens, similar to Marek's disease, is Lymphoid Leukosis which is caused by a Retrovirus. Common poultry publications often use the terms Marek's and Leukosis to refer to the same disease but they are actually different diseases that cause similar signs and lesions. Birds with Marek's show various forms of the disease.
Visceral Marek's results in tumors on the liver and other organs; the bird becomes thin and eventually dies. The neural (nervous system) form of Marek's results in progressive paralysis of the wings, legs and neck. An enlarged sciatic nerve (a nerve found in the inner part of the thigh) is a common cause of paralysis, with the bird eventually lying on its side unable to move. Gray eye is another form of Marek's, in which the iris shrinks, the eye turns gray and the bird goes blind. Fortunately, a vaccine for Marek's disease is available and most poultry suppliers sell chickens that are already vaccinated for the disease.


Coccidiosis

Coccidiosis is the single most common cause of death in young birds. It is caused by single-celled protozoan parasite that attacks different parts of the intestinal tract, causing an irritation of the lining that prevents the absorption of food. In minor outbreaks, the birds are droopy, have ruffled feathers and lose weight. Egg production in older birds declines. Severe cases result in hemorrhage and death. Practically all poultry house litter contains coccidia; it is important to keep litter dry and to purchase feed that contains a coccidiostat for young birds.

External parasites

External parasites cause losses if proper prevention and treatment procedures are not followed. Chickens should be checked once a week for signs, as shown in Table 9. Consult with your county Extension agent for procedures and chemicals for prevention and control. Follow directions on packages of chemicals for treatment and control.

Table 9. Common external parasites
External parasites Symptoms
Chiggers Red, pimple-like irritations
Lice Large, yellowish, transparent insects on the skin; low weight; blackish discoloration (dirty) in the vent and tail area; drop in egg production
Mites  
Red (roost) Loss of weight, red specks, death
Northern fowl Red or black specks around vent, unthrifty, drop in egg production
Feather Loss of feathers, web irregular with only shafts left in some cases
Scaly leg Enlarged shanks and toes with raised, crusty scales

 


Internal parasites

Internal parasites are worms found in the digestive and respiratory tracts. Often insects, such as beetles, act as the intermediate host. Insects carry the worm eggs, which are deposited in the chicken after the chicken eats the insect. Common internal parasites are listed in Table 10. Chemicals for the prevention and treatment of internal parasites should be administered under the direction of a competent authority.

Table 10. Common internal parasites
Internal parasites Symptoms
Large roundworm Long, yellow-white worms in intestine; droopiness; weight loss; diarrhea; death
Capillary worm Hair-like worms in crop and upper intestine, droopiness, weight loss, death
Cecal worm Short worms in the ceca, unthrifty, weak, loss of flesh
Tapeworm

Long, white, flat, segmented worms in intestine; unthrifty; slow growth; weakness

Gapeworm Red, forked worms in trachea; gasping; coughing

 

Other diseases

Other diseases are not as common and require a professional diagnosis. Moldy feed causes mycotoxins which may result in production losses and flock mortality. Chickens can also develop nutritional deficiencies if they are not given a well-balanced diet.

Sanitation


Lack of cleanliness is often a precursor to poultry disease. There are several sanitation measures that should be taken in a home chicken flock:

1) complete cleaning and disinfecting of house and equipment before starting chicks or housing layers

2) daily cleaning of waterers

3) screened manure pits under roosts, feeders and waterers

4) managing litter to keep it dry and clean

5) burying or composting all dead chickens

6) raising young stock away from adult chickens

7) isolating the flock from outside traffic (chickens raised off the farm, neighbors, birds, dogs, etc.)

8) practicing good housekeeping and rodent control

9) disposing of litter and manure by spreading and plowing or spading the manure under soil. Manure and litter should be spread and stored in areas not used by poultry.


Poultry manure can provide an excellent source of plant nutrients for your garden. Due to the danger of infection, poultry manure should always be well composted before adding to your garden. Never add any type of raw manure to your vegetable garden. Please refer to the on-farm composting publication listed in the References section of the bulletin for complete details.

Properly managing any mortality from your chicken flock will prevent the spread of disease. There are several options that are available for managing the disposal of dead chickens. Composting is one option to consider. Composting animal carcasses is identical to the process occurring in the composting of any other organic material. However, composting may not be a viable option when there is very little mortality. University of Maryland Extension Fact Sheet 717 by Brodie and Carr provides complete details about composting animal mortalities. Burial may be another option of dead bird disposal; however, it may not be permitted in certain locations due to groundwater levels. It is recommended to check with your county before disposing of any dead birds by burial. There are also dead animal removal services available in Maryland that will dispose of dead birds for a fee.

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