|Practical Poultry Raising (Peace Corps, 1981, 225 p.)|
|7. Keeping chickens healthy|
Chickens are subject to as many ailments as humans are. Some chicken and human diseases even have the same names: pox, colds, cholera, typhoid, hepatitis, pneumonia, bronchitis and so forth. Parasites, such as tapeworms, ticks and lice, and poisonous substances such as aflatoxin and botulism attack chickens as well as humans. A welltrained veterinarian, backed by a competent laboratory, can identify most chicken diseases with a good degree of certainty, but even then often can't prescribe effective treatment, because some diseases cannot be treated, only prevented.
So what hope is there for small farmers and extensionists who don't have the veterinarian's experience and equipment? Plenty. Good management of chickens, with special attention to sanitation, quality of feed and vaccinations greatly reduces the chances of diseases or parasites attacking the flock. Knowing about major health problems and how to treat them is important - but not as important as preventing these problems in the first place.
Even with good management, of course, health problems can occur, and the farmer should be alert for them. A sick chick is inactive, doesn't stand erect and may have runny eyes or dried traces of diarrhea around its vent. It may sleep in an odd position or walk with a strange gait. Older sick chickens show obvious signs of poor condition: thin, hunched body, scraggly feathers, wings hanging loosely, general weakness and smaller size than the healthy members of the flock (assuming that the flock is all the same age and breed, which is stongly recommended). Two major signs of health problems in a flock are if total feed consumption decreases, or if mortality exceeds one percent in any seven - day period. Observe your flock for deviations from normal for at least 15 minutes each day.
Even in a well - managed flock you can expect to lose an average of one percent each month. In other words, if you start with 100 chicks, you should expect to have about 90 left at the end of a year. Some will die suddenly; others will show obvious signs of disease. Remove sick and dead chickens.
For small flocks of less than 50 chickens, use an isolation pen for the period of sickness. For larger operations, slaughter sick birds and perform a post mortem examination to see if the cause of sickness can be determined.
If mortality exceeds the one percent rate or if there are more than one or two sick chickens in a flock of 100, seek veterinary advice immediately.
Bury all dead chickens in a pit in the ground to eliminate any chance of disease transmission from these chickens. A dead bird disposal pit should have a tight cover to prevent predators such as rats from getting at the chickens. If the farmer has a methane gas digester, dead chickens can be put in this, but feathers will have to be removed first because they do not digest for many months. If this is done, burn the feathers.
The innumerable diseases that can affect a chicken may be divided into three categories:
· Those prevented by locally recommended vaccines (such as Newcastle).
· Those prevented by or treated automatically in a good management schedule (such as coccidiosis).
· Those for which good sanitation and nutrition are the best means of prevention (such as cholera or coryza).
Prevention by Vaccination
Before doing any vaccinations, you should become familiar with what diseases are prevalent in your area or you may needlessly vaccinate for a non - existent disease. Check first with local authorities. A vaccine, which contains bacteria or viruses introduced into the body to produce immunity to a specific disease by causing the formation of antibodies, can be administered to chickens in a number of ways (see below). Handle the birds swiftly but smoothly to minimize stress, but be sure that all receive the proper dosage.
Be extremely careful with vaccines - they can kill birds. Store them according to directions; many need refrigeration. Mix them away from poultry just before using. Don't spill them on or near chickens. When working with large numbers of birds, have adequate help - the person mixing and giving the vaccines should not handle the birds, if possible. If you are using a live virus vaccine, tell neighboring farmers because if they have not already vaccinated their birds, the live virus could spread the disease to their chickens. If one farmer vaccinates and the next doesn't, be certain there is no means of transmitting the disease to non - vaccinated birds. Don't give more vaccine per bird than recommended, and don't give less - stretching vaccine supplies is dangerous. Administer mixed vaccine at once and get rid of the remainder - don't keep it overnight as it will lose its effectiveness. Thoroughly sterilize your equipment if you plan to use it again (it is best to dispose of it and use new equipment). Change your clothes and disinfect your shoes before visiting other chickens.
Methods of vaccination include:
· Medicine or eye dropper - Put a drop of vaccine in the bird's eye and wait for it to blink, or place a finger over one nostril, put the drop in the other nostril, and wait until the drop is breathed in.
· Feather follicle - Pull a few feathers from the bird's thigh and rub the feather follicles in the area with a vaccine - soaked cotton swab or brush.
· Wing web stick - Dip a web stick into vaccine and use it to puncture the skin on the underside of a wing. Be careful not to hit a blood vein. Always stick the same wing of all birds (either the left or the right wing) so that you can check later on for a scab which shows the vaccine has been effective, or "a take."
· Drinking water - Some vaccines are mixed into the flock's drinking water.
· Intramuscular - Use a syringe to inject the vaccine into the breast.
Wing Web Stick
Other than knowing the obvious symptoms of the most common chicken diseases and what to do about them, an inexperienced farmer should be very cautious about diagnosing a disease and attempting to cure it. Seek professional advice whenever possible.
Disease Newcastle is the disease most widely feared by poultry farmers around the world. When it strikes young chickens, mortality may be as high as 100 percent. In parts of Asia, it is known as Ranikhet Disease.
Cause - Virus transmitted by other chickens and other species of birds.
Symptoms - Coughing, gasping and raspy breathing and/or extreme nervousness, and distended crop. Inactivity, uncoordination, drowsiness, huddling near heat source, drooping head, partial paralysis, coma, death. The presence of all these symptoms does not confirm the diagnosis - only lab tests can do that. Newcastle quite often appears as a respiratory condition before a nervous condition appears.
Post mortem signs - Mucus in trachea, possibly yellow and thickened air sacs; possible hemorrhages in proventriculus.
Treatment - None.
Prevention - Most countries have vaccines available. A general rule of thumb used by many poultry experts is to vaccinate on a 4 - 4 - 4 schedule, meaning at four days of age, four weeks, and four months. But you should use local recommendations.
Puncturing the Wing Web
Fowl pox is a disease that attacks birds when they are three to five months old. It is not necessary to vaccinate for this illness before the chicks are five weeks of age. Pigeon pox vaccine is only needed to provide emergency treatment if there is an outbreak of fowl pox in a non - vaccinated flock.
Cause - Virus spread by insects, especially mosquitoes,and then by direct contact with infected chickens and wild birds.
Symptoms - Fowl pox most frequently attacks birds when they are three to five months old. There are two types:
· Dry pox or modular form, which generally appears as a wart or insect bite. Causes swelling of comb, wattles, face and sometimes eye. By itself, dry pax doesn't usually cause much mortality.
· Wet or diptheritic form begins with discharge from e es and nostrils, then a cheesy material forms in the mouth. This can cause suffocation unless it is removed. Wet pox results in high mortality - up to 50 percent - and egg production in layers decreases substantially.
Post mortem signs - Mucus in trachea, possibly yellow and thickened air sacs, hemorrhages in the proventriculus.
Treatment - In an affected flock: if the birds have been observed daily, this disease can often be detected before many birds are affected. In this case, vaccinate the unaffected birds with fowl or pigeon pox vaccine immediately. If a neighboring flock gets the disease, vaccinate all flocks in the area immediately. There is no treatment for chickens already having fowl pox.
Prevention - Follow the recommendations of local authorities. In most cases this means:
· If fowl pox is prevalent in an area, the best action is to vaccinate. Many experts suggest vaccinations around the sixth week of age and again at 12 weeks.
Cause - Bacteria spread by droppings of infected birds through contaminated soil, feed or water. Vectors include wild birds and the feet of people and animals.
Symptoms - There are two types of cholera which affect chickens:
· Peracute or severe cholera: the only symptoms are dead birds.
· Acute and chronic: sudden, almost total lack of appetite; greenish - yellow diarrhea; difficulty in breathing; high fever and increased thirst; head turns blue; enlarged, hot, swollen combs and wattles; affected birds feel very hot; swollen eyes and thick discharges from nasal passages similar to that found in coryza.
Treatment - A recommended bacteriacide (sulpha drugs) in feed and water may reduce mortality in an infected flock. Remove affected birds and change litter. Thoroughly disinfect equipment and house.
Prevention - Primarily, cleanliness. If vaccines are recommended, it may help to administer them in accordance with the recommendations of local authorities.
Cause - Virus spread through air or via contaminated material.
Symptoms - Chicks: sneezing, gasping, mucus, clicking heard in throat, discharge from nostrils and eyes. Layers: egg production drops abruptly by 10 to 50 percent, remaining production poor quality (thin shells, misshapen, watery whites). In chicks, mortality may be 5 to 60 percent; in mature birds, zero to two percent.
Treatment - None for the infection. Antibiotics can be given to lessen complications.
Prevention - Following nearby outbreaks, vaccines, if recommended by local authorities, can be used in accordance with their recommendations and schedules.
Cause - Virus, airborne or carried on clothing and equipment from infected birds.
Symptoms - Birds have extreme difficulty breathing, may stretch their necks when inhaling and droop their heads on their chests when exhaling, also may cough up bloody mucus. Mortality may range from 5 to 50 percent.
Treatment - None for the infection, but disease spreads slowly, so unaffected birds can be vaccinated.
Prevention - Never vaccinate where there is no history of the disease. If an outbreak occurs nearby and vaccine is available, use the schedule and methods recommended by local authorities.
Marek's Disease (Leukosis)
Cause - Virus spread through chicken dander (cells sloughed from feather follicles), the major component of chicken house dust.
Symptoms - Droopiness, poor feathering and weight loss may be the only signs before death. Some birds are mildly to completely paralyzed; they lie on their sides and slowly starve. Mortality may be up to one percent per day for two to three weeks.
Treatment - None.
Prevention - Vaccination of day old chicks - usually done by the breeder, if done at all. Vaccinated egg - breed chicks are especially valuable.
Cause - Salmonella bacilla transmitted through the eggs from one generation to the next if parents are not salmonella - free. Can also be transmitted through visitors' feet, animals, contaminated feed, equipment, and wild birds.
Symptoms - Chicks: sudden deaths, other chicks droop wings, huddle near heater. Diarrhea is white, sticky and foaming. Chicks may have 50 percent mortality. Adults: in acute outbreaks are weak and depressed, may have greenishbrown diarrhea.
Treatment - Sulfabased drugs for market stock; do not use
infected birds for breeding.
Prevention - Buy only certified pullorum - free chicks and implement sanitary management practices.
Cause - Nine species of coccidia (protozoan parasites) spread through contaminated food, water or litter. Each species attacks a different portion of the intestines or ceca, an intestinal appendage. It is extremely difficult to isolate chickens from coccidia.
Symptoms - Signs of the disease will vary with the type of coccidia involved and the degree of immunity the flock has to that type. General indications are: decrease in food consumption; birds hunch backs, droop tails and ruffle feathers. Diarrhea may start and the loose droppings may be bloody (reddish brown). Following bloody diarrhea, mortality may increase rapidly.
Post mortem results - In chickens less than 16 weeks old, red specks on interior wall of intestines (in severe case, purple spots show through exterior wall). Intestinal wall thicker than normal. Other signs: gray - white streaks on wall of upper intestine, pink or reddish substance on intestinal wall. In chicks (under nine weeks) ceca may be filled with blood and swollen to the size of a finger. For birds older than 16 weeks, a lab test is needed.
Treatment - If a confirmed outbreak among chickens one to twelve weeks old is severe, treat immediately with locally recommended coccidiostats.
Prevention - There are three ways to deal with coccidiosis.
· Natural development of immunity - Allow the flock to build immunity without administering any drugs unless there is a severe outbreak. This works well when the flock is exposed only to low levels of coccidia. Under very dry conditions, there may not be enough infection present to develop immunity. In a very dry environment, sprinkle the litter with water at weekly intervals to maintain a constant exposure and immunity level in the flock. This may be necessary where a wellventilated poultry house is located in an area where the humidity level of the outside air is consistently under 50 percent. Sudden, massive invasions of coccidia can hurt the flock severely, and large doses of medication can prevent future immunity.
· Complete prevention - Give the flock the recommended medium level of coccidiostat through its first 15 weeks. This most likely will prevent the birds from contracting coccidiosis at all, but they won't develop immunity either. Use this method only for broilers and for layers that will be kept in wire cages.
· Immunity plus treatment - Use the low - level dosage recommended during the first 15 weeks. This should allow the birds to develop some immunity, and they may not need any further attention. In case of a mild outbreak, treat broilers and layers going to cages with the largest recommended dosage. Treat layers that will be kept on litter with heavy doses only during severe outbreaks so that they otherwise build up as much immunity as they can. This method is the safest overall, and would be the best single recommendation for small - and medium - sized flocks.
Coccidiostats - These drugs come in many forms, many combinations and under many names, both generic and proprietary. It's a good idea to switch from one type of drug to another each chicken cycle so that local coccidia do not establish resistance to any particular one. Don't mix one with another - it may be harmful. Follow manufacturer's directions closely.
Some effective coccidiostats are: amprolium; amprolium plus ethopabate (not for laying chickens); arsenobenzine, stop use five days before slaughter; glycarbylamide (not for laying chickens), stop use at least four days before slaughter; dinitrodiphenyldisulfide; nicarbazin, stop use four days before slaughter; aklomide, stop use at least five days before slaughter; bithionol and methiotriazamide, stop use at least five days before slaughter; 3,5, dinitro - oToluamide (not for laying chickens); and sulfaquinoxaline. Other drugs that can be used as coccidiostats, though not as effective as those above, include: terraymicin, nidrafur, agribon, 3 - Nitro, NF - 180 - furazolidone, nitrofurazone, phthalysulfacetamide (TSC), and sulfaethoxypyridazine (SEZ).
Infectious Coryza (Cold)
Cause - A bacteria, spread from chronic or acutely infected birds to healthy birds.
Symptoms: Foul - smelling discharge from eyes and nostrils; coughing; sneezing; difficult breathing; chicks shake their heads as if trying to get rid of something; often found where different ages of birds are kept together and birds are overcrowded. Rare in adults, but when found, egg production drops, feed consumption decreases. Mortality rare.
Treatment - Sulfa drugs in the feed or water will eliminate the problem within two weeks if other diseases or complications are not present.
Prevention - Do not mix birds of different ages: cull all birds found with swollen head parts before they infect the rest of the flock; there may be bacterins or vaccinations available in some countries, but not most. Use proper management practices.
Parasites, both internal and external, weaken and can kill chickens. In addition to getting its food from a chicken's body, a parasite also can carry disease or increase the bird's susceptibility to disease.
At least nine species of worms may infect various internal parts of chickens. Chief among them are roundworms, cecal worms and tapeworms. Worms are spread through feces or through a variety of intermediate hosts, including snails, slugs, earthworms, flies, cockroaches and other insects.
Symptoms - Initial increase in feed consumption with little or no weight gain. In severe cases, chickens lose weight rapidly. Laying chickens produce fewer eggs.
Post mortem results - Large roundworms, found in middle of small intestine, are yellowwhite, from 4 to 7.5 cm. (1 1/2 to 3 in.) long, and comparatively thick - bodied. Cecal worms, found in blind ends of the ceca, are white and about 1.25 cm. (1/2 in.) long. Tapeworms, found in the small intestine, are flat, white, ribbon - like and segmented. They vary in size from microscopic to 15 - 17.5 cm (6 to 7 in.).
Treatment - Each type of worm requires a specific drug: piperazine for roundworms, phenothiazine for cecal worms and dibutyltin dilaurate for tape worms. Some manufacturers combine one or more of these drugs in a single medication. Treat as directed for major infestations.
Prevention - Primarily, sanitation. Make sure that litter is replaced between flocks, keep wild birds out of the house, use insecticides against cockroaches and other intermediate hosts and do not feed snails or slugs to chickens. If you suspect that worms are present (they probably are), treat broilers at four weeks of age and every two months thereafter; layers at ten weeks and every two months thereafter.
The most common poultry parasites are lice. They spend their entire life cycle on the body of the bird.
Symptoms - Skin irritation, scabs, ruffled feathers, diarrhea, small weight gains or decrease in egg production, some dead young chickens when infestations are heavy.
Treatment - Infested chickens on raised floors, in cages or ranging free should be sprayed or dusted with malathion, carbaryl, pyrethins, naled, coumaphos or similar preparations, using a crop sprayer. In deep - litter systems, the litter and all equipment except feeders and waterers can be sprayed or dusted. Where chemicals are too expensive or not available, some farmers use a mixture of ashes with sulphur powder or gun powder obtained from the local market. About 20 grams of sulphur powder to 1 kg of cold ashes or a 1:50 ratio is said to be quite effective.
Prevention - Keep nests clean. If you use roosts, paint them
with nicotine sulfate - the bird's body
heat will create fumes that kill the lice. Some use creosote in the cracks and joints of roosts (carbolineum).
One Kind of Chicken Louse
Mites are almost invisible, spiderlike creatures that come in various species. Some stay on the birds continuously, while others attack only at night.
Symptoms - Scaly leg mite: birds lame, legs swelling, scaly and crusted. Red mites (nocturnal): loss of weight and egg production, anemia. Depluming mites (base of feathers): birds pull feathers out to relieve itching.
Treatment - None for scaly leg, cull affected birds. For other mites, same treatment as for lice.
Prevention - Same as for lice.
In addition to sucking blood, fowl ticks (flat, egg - shaped, reddish - brown bugs), can carry spirochetosis. Spirochetosis, or tick fever, results in rapid death without any other symptoms. Usually, ticks are found only in hot, dry areas. They spend part of the time in cracks in walls, roosts, and other wooden equipment and are very hard to find. If you suspect their presence, pry into cracked boards with a knife and examine closely.
Symptoms - Loss of appetite and weight, possible anemia.
Treatment - Same as for lice, then aggressively attack infestation, removing litter and equipment, feeling in cracks in feeders and elsewhere for ticks, cleaning and spraying everything, and repeating that twice at two - week intervals and once six months later. If the roof is thatch, change it. If the house is old, consider building a new one. Some farmers go over cement and other non-inflammable materials with a blowtorch.
Prevention - Sheet metal feeders, nesting boxes and other equipment are easier to keep free of ticks than wooden ones. Roosts hung by wire are safer than those on stands.