Common Diseases and Parasites in Chickens
Chickens are subject to numerous diseases and parasites. In fact, diseases and parasites are the chief hindrances to success in raising poultry. Most common health problems can be avoided through preventative management; nevertheless, sooner or later every flock experiences its share of maladies. If you are not prepared to deal with these problems, do not get involved with poultry. The poultry farmer must be ever vigilant in monitoring the condition of his or her flock. For more information on poultry disease, order A Manual of Poultry Diseases distributed by the Texas Agricultural Extension Service.
Having said all that, there is an argument to be made against overreacting to disease. Those who administer antibiotics as a general disease preventative are guilty of this. The commerical poultry industry which sets most of the standards for disease control is far more concerned about disease than should be the small farmer. This is because an outbreak can wreak havoc in overcrowded battery houses and result in substantial financial losses for the high-volume commercial farmer. In my opinion, the small farmer is better off breeding for a strong constitution over time by retaining robust birds and culling out weak and disease prone ones. This is an excellent method for improving the long-term heatlh of your flock. I have found, for instance, that the only way I can economically deal with chronic respiratory disease is to allow my birds to develop resistance to it. Breeding for resistance also implies that one will not restock with new birds every year, as is recommended by many experts. Rather one will retain and perpetuate those birds which have exhibited strong health characteristics.
Chronic respiratory disease (CRD) is a bacterial infection, characterized by coughing, sneezing, nasal discharge, lethargy and weight loss. It has caused high mortality in many flocks, especially among young birds. An outbreak of this disease can persist in a flock for many weeks. This disease is highly contagious and can even be transmitted from hens to their eggs. Treatment of CRD with antibiotics has shown mixed results.
Infectious Coryza is a bacterial infection which usually results in swelling of the face around the eyes and wattles. Watery discharge from the eyes frequently results from the lids adhering together. This disease is easily treated with antibiotics, such as terramycin.
Pullorum disease is a bacterial infection highly fatal to young chicks and detrimental to production in older birds. It is best diagnosed through blood testing. The complete eradication of infected birds is the only sound way to prevent pullorum disease. Make sure that you purchase chicks from hatcheries operating under a state or national pullorum control program.
Epidemic tremors is a viral disease often transmitted to chicks through the eggs of infected parents. It usually affects young birds and, while seldom fatal, usually permanently damages infected birds. Its symptoms include the inability to walk normally and paralysis. Vaccines are widely available for this disease.
Fowl pox is a slow-spreading viral infection resulting in nodules and scabs on the face, mouth and throat. It usually last for several weeks and retards growth, but is seldom fatal. A vaccine is available for this disease.
Infectious bronchitis is an extremely contagious respiratory infection of poultry, characterized by coughing, sneezing and rattling. The disease never causes nervous system disorders. It usually last from 10 to 14 days in a flock and morality varies, though chicks are particularly susceptible. Vaccines are available for this disease, and it is often administered in combination with Newcastle vaccine.
Marek's disease is a viral disease which usually affects young birds. There are several forms of the disease, including those which attack the viscera, the nervous system, the eyes and the skin. Therefore, this disease may produce a variety of symptoms in various combinations. The best means of avoiding Marek's disease is to buy chicks from hatcheries which vaccinate against it.
Newcastle disease is a highly contagious viral infection, causing a nervous respiratory disorder in poultry. Symptoms include nasal discharge, excessive mucus in the trachea, difficulty in breathing. Particularly in young birds, nervous disorders, such as paralysis of one or both wings and legs or a twisting of the neck and head, may also develop. Mortality rates resulting from Newcastle infections varies. Vaccines are widely available for this disease.
Coccidiosis is a protozoan intestinal disease of poultry characterized by diarrhea, lethargy and emaciation. It is usually seen in growing birds and young adults. While not resulting in high mortality, coccidiosis greatly inhibits development. Most poultry feeds contain a coccidiostat, which prevents this disease.
The best means of avoiding outbreaks of diseases and parasites is to exercise preventative health care practices. To accomplish this:
1. Do not run new chickens in facilities previously used by another flock until the facilities have been thoroughly cleaned and disinfected.
2. Never mix chicks or growing birds with adults. The greater the separation the better.
3. If you must mix birds from another flock with your existing flock, quarantine the new birds for a several weeks to make sure they are disease free.
4. Avoid exposing your flock to wild birds or vermin.
5. Observe proper nutrition.
6. Provide spacious coops with adequate ventilation.
7. Isolate sick birds from the rest of your flock.
8. Vaccinate against diseases common to you area.
9. Guard against parasites.
10. Work with your veterinarian.
11. Do not indiscriminately administer antibiotics as a preventative healthcare practice.
Vaccines are suspensions of large amounts of the disease-causing organism or virus in a diluent. When administered to poultry, vaccines stimulate antibody production so that the birds develop an immunity to targeted pathogens. Because most vaccines contain living vaccine viruses that can adversely affect unprotected laying flocks, one must be careful not to spread pathogens to other birds on the same premises. Vaccination programs should be tailored to meet the needs of a particular region. Vaccines, as drugs, must be used properly to be effective. For best results:
1. Store vaccines in the refrigerator according to manufacturers recommendations.
2. Do not use outdated vaccines.
3. After a vial of vaccine has been opened, destroy by burning any contents remaining after use.
4. Records serial numbers of vaccines used.
The Texas Agricultural Extension Service recommends the following vaccination program:
Replacement Chicks for Egg Production or Breeders:
1. Purchase day-old chicks vaccinated at the hatchery against Marek's disease.
2. Vaccinate for Newcastle at 7 days and at 4 weeks of age through drinking water or spray method.
3. At 6 weeks, vaccinate for infectious bronchitis through drinking water.
4. At 8 weeks, vaccinate for fowl pox using wing-web stab method.
5. Between 10 and 14 weeks, vaccinate breeders against epidemic tremors.
6. Revaccinate against Newcastle disease when birds are moved into laying house.
Chicks for Broiler Production:
1. Vaccinate for Newcastle at 7 days and at 4 weeks of age through drinking water or spray method.
2. At 2 weeks, vaccinate for infectious bronchitis through drinking water.
Mites and lice are the two most common external parasites of poultry. These pests infestations can transmit pathogens, decrease egg production, increase feed costs, reduce weight gain and even lead to death. To prevent external parasite infestation: 1) Keep your facilities clean, 2) Avoid exposing your flock to other chickens, wild birds and rodents 3) Routinely examine your birds for signs of infestation. A good discussion of poultry parasites and pests is provided by Dr. Philip G. Koehler. Also check out External Parasites of Texas Poultry by the Texas Agricultural Extension Service.
Mites are usually found on and under feathers, but a few varieties may be found in body tissues, feather quills and respiratory passages. Some mites, such as the northern fowl mite, depluming mite and chicken mite, live on the host and are usually detected by damaged feathers and feather loss. Other species, such as the red mite, hide around roosts during the day and feed on the host only at night, making them difficult to detect. The scaly-leg mite burrows beneath the scales on feet and legs, causing large, disfiguring crusts and scabs to form. This is a very common and detrimental mite. Fortunately, it is easily remedied through several applications of viscous oil, such as mineral oil or linseed oil, to the afflicted bird's legs.
Lice are wingless insects with flattened bodies and broadly rounded heads. There are several species of lice which affect chickens, including the body louse, the head louse, the wing louse and the fluff louse. Check under your chickens' feathers regularly for signs of infestation. Also watch for egg clusters on downy feathers, especially on the head and around the vent. Dusting chickens with 5% Sevin dust usually gets rid of lice.
Large roundworms are a common parasite of poultry. Adult worms are about 1.5 to 3 inches long and about the diameter of a pencil lead. Piperazine is highly effective in removing the adult parasite, though it is the immature form that causes th e most damage. The best means of dealing with this parasite is through prevention; Make certain that your facilities are cleaned thoroughly before introducing new birds.
Tapeworms are flatened, ribbon-shaped worms composed of numerous segments. They vary in size from very small to several inches in length. All poultry tapeworms spend part of their lives in intermediate hosts (usually insects), and the birds become infected by eating these hosts. Although several drugs are available for removing tapeworms, most are of doubtful efficacy.
Cecal worms have a life cycle similar to that of large roundworms. These worms are found, however in the ceca and not the large intestine. This parasite is rarely problematic, though severe infestations may cause weakness and emaciation. Phenothiazine and hygromycin B have been used successfully as treatments.