A recent cooperative extension article by Dr. Syed A. Bokhari of the University of California (edited for Hatch by Mark E. Cook) described the disease and prevention of the pathogen Mycoplasma gallisepticum (MG). The following is an excerpt from Dr. Bokhari's article. The Infection MG (Mycoplasma gallisepticum) is one of the major health problems facing the poultry industry. About one-third of the nation's table-egg laying flocks are infected with MG, including 75% of the multi-age flocks and 15% of the all- in, all-out flocks. As much as 90% of the backyard poultry may also be infected with mycoplasmas. Other fowl, i.e. turkeys, partridge pheasants, peafowl, guinea fowl, quail, ducks, and pigeons are also susceptible to MG infection. They may be present and cause no disease until triggered by stress. Following infection, this may collapse under certain conditions. Mycoplasmas are susceptible to various chemicals including some broad-spectrum antibiotics and commonly used disinfectants. The severity and appearance of disease may be influenced by concomitant infection and other pathogens and/or by predisposing factors. Predisposing factors include nutritional deficiencies and intensive management with excessive ammonia and dust. Other pathogens include the viruses of Newcastle disease and infectious bronchitis, including vaccine strains and pathogenic strains of E. coli and Hemophilus gallinarium. Under experimental conditions the incubation period between exposure and infection is from 6 to 21 days. Under field conditions, the incubation period is not established due to many variables which influence the onset and the extent of disease. Field outbreaks of MG near the onset of production (between the 26th and 38th weeks of age) may suggest a long incubation period. |
Transmission Mycoplasma may spread rapidly within a population of birds. There is only a week or two separating the first evidence of infection and the time the entire flock becomes positive. The disease is spread in the flock by direct contact (bird to bird) with infected carriers, airborne dust and droplets, contact with contaminated equipment, crates, feed, water, and litter, and other species of birds, wild birds and rodents. MG can also spread through the hatching eggs (transovarian) and/or hatchery. The severity and intensity of MG infection is variable. It is more severe and of longer duration in the cold months and it affects younger birds more severely than mature birds. Recovered birds may become carriers of MG. |
Symptoms Signs of MG may develop slowly in the flock. Respiratory signs usually persist for weeks. The first sign is a nasal discharge followed by a foamy or bubbly condition of the eyes. Birds may show a persistent hacking cough, sneezing and sniffing, and tracheal rales. Poor physical condition and loss of weight are usually apparent. In broilers, the onset of signs are severe and include severe reduced growth rate and feed intake. Layers will show a drop in egg production and feed consumption. Production may continue at a lower level. The primary lesions in turkeys are air sacs and lung lesions. Swelling of one or both infraorbital sinuses may be apparent. Internally one may see marked swelling of nasal passages, sinuses, trachea, and bronchi. Air sacs are often thick and opaque (recent vaccination against IB or ND may also enhance the opacity of air sacs) and may contain slimy or cheesy exudate. Morbidity and mortality in the field outbreaks vary widely depending on the environmental and climatic conditions and type of secondary infection. The infection may vary from mild with low mortality to severe with high mortality In broilers, mortality may be high if management is poor and birds are exposed to stress and other secondary infection. Laying hens usually experience low mortality, but many of the birds have an unthrifty appearance. Very high mortality may be seen in turkeys. |
Diagnosis Presumptive diagnosis may be based upon flock history and records of performance, and a positive plate/tube agglutination test for MG. Confirmed diagnosis is by isolation and identification of Mycoplasma gallisepticum. The general consensus is that a MG outbreak results in a financial disaster for a producer. In addition to the loss of production and birds, he/she is saddled with expensive drugs and other expenses; cleaning, disinfecting, and keeping the premises empty for 30 to 90 days, etc. Loss of market and loss of income may further aggravate the situation. Business as usual is never possible once a flock of birds becomes positive. |
Prevention As a first step, initiate today a self-imposed quarantine. Stop everything! People who come in direct contact with, and especially those who handle birds and manure, are the major concern for MG transmission. People are not controlled unless doors are locked. Keep a log book in each house to record the arrival of visitors who are required to sign in. This log wilt help you track down other potentially exposed flocks. Make no unnecessary visits to other poultry farms. If you must, visit no more than one flock per day. Ranch managers should not visit other poultry farms. Make it clear to farm workers that it is your farm policy that you do not allow other poultry on your ranch and you do not hire people who have any birds at home. Furthermore, you would prefer that no other members of the workers' families work at a poultry meat processing plant, hatchery, or assist in load-out on another ranch. Establish a pattern for necessary traffic by your field supervisors or production managers. If there are several farms in your organization, establish zones to prevent one person from traveling to all farms. Isolate young birds from older birds. Do not travel between them. Provide boots and coveralls for necessary visitors. Inspect everyone who comes to the farm. No truck drivers are allowed to enter the poultry houses. Part-time help and crews must wear freshly laundered clothing or clothing supplied on the farm each day. |
Step-By-Step MG Prevention Program Clean Infected Premises a. Completely depopulate the infected premises (removing all birds as well as all used feed supplies, removable equipment, and supply items that may be contaminated) to establish a "MG-free" flock. b. Remove all of the litter and manure completely. c. Wash down all inside surfaces (walls, ceilings, rafters, ventilation openings, air intake ducts, etc.) with a high pressure washer using a large volume of water. The addition of a cleaning agent speeds up and improves the process. d. Disinfect all of the interior surfaces of the building with recommended concentration of phenolic or cresylic acid disinfectant solution. Chlorine bleach solution (.025%) may be substituted for phenol or cresylic acid solutions. e. Spray the entire floor area, the lower three to four feet of the support poles, the perimeter walls, and the area outside the entrance with 0.1% glutaraldehyde solution at one gallon per 10 square feet. Also, spray a five- to ten- foot band around the entire outside perimeter to prevent contamination from outside the building. Close up the building and make it tight without any ventilation until the next day, and then open it up and air out the formaldehyde fumes. f. Spray the entire floor area, support poles, and side walls with carbaryl insecticide at recommended levels to control insect pests. Malathion may be added to, and applied with, the cresylic acid spray in place of the separated carbaryl applications. g. Bring back the necessary removable equipment that has been cleaned and disinfected and bring in feed and supply items that are also clean and not contaminated with pathogens. h. Allow the buildings to remain empty for at least two weeks after cleanout. i. Always consider the area outside the building contaminated, particularly if the previous flock had MG. Set up your traffic pattern to prevent recontaminating the building from the area outside. j. Obtain chicks hatched from eggs from MG-free breeder flocks, hatched in a hatchery where no infected eggs are set, and delivered in "MG-free" trucks by people who have no contact with infected birds. k. Farm workers go from younger to older birds (not vice-versa) if mutliple ages are present on the farm and cared for by the same person. l. Have only one age group on the farm (all-in, all-out) or have barns adequately separated (about 650 feet or more) and treat each age group as a separate unit. Clean up and disinfect barns between flocks. m. Enforce regulations on clothing and footwear worn by flock caretakers, servicemen, and equipment repairmen that move between flocks and farms. You can significantly influence the security and isolation of a healthy flock from the rest. Use "on-farm" clothing (including coveralls, boots, hats, etc.) in poultry barns. n. Feed truck, egg pick-up, and other service vehicle drivers must stay in the truck if servicing both infected and free farms (or if that is not possible, avoid the barn entrance area). |
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The following is taken from an article in the December 2000 Poultry Press:  Mareks Disease (MD), is a common virus that causes internal lesions (tumors), and kills more birds than any other disease. It is so common that you should assume you have it in your flock, even if you detect no evidence.
Mareks is a member of the herpesvirus family of viruses. It is also known as "Range Paralysis". Mareks is spread through airborne feather dander so microscopic that it can spread from one farm to another via the wind, even when no human or bird contact is made between the two farms. The virus enters through the bird's respiratory tract. The turkey version is Herpes Virus Turkey (HVTP, and the waterfowl version is known as Duck Virus Enteritis (or DVE). All three are from the same family of viruses. It's not common for MD, HVT, and DVE to cross over between chickens, turkeys, and ducks kept together, but it has happened. The study of Mareks Disease in poultry is exciting because it has had a profound effect on cancer research in all species, including human. And the Mareks vaccine for chickens was the first time medical science was able to produce an effective cancer vaccine for any species. There are a few different types of Mareks in chickens. The most common are eye, viceral (tumor producing), and nerve. The nerve version is known by some Fanciers as "down in the leg", and symptoms range from slight to severe paralysis in the wings, legs, or neck, and usually results in death from trampling by other chickens, and/or the inability to get to food and water. There can be "transient" paralysis that disappears after a few days, such as a dropped wing that suddenly corrects itself. In the eye version, you'll detect an irregularly shaped pupil, cloudy eye (gray eye), or sensitivity to light. It can result in blindness. The visceral version should be considered when a bird is just generally "wasting". Mareks is extremely contagious but does not spread vertically (to the egg). Youngsters should develop a natural immunity (called 'age resistance'), by the time they are five months old. This is one of the reasons it is important to raise your youngsters separately from you oldsters. The older birds that have encountered Mareks and have managed to survive are carriers. New birds coming in from other flocks are always potential carriers. Mareks usually hits between 5 and 25 weeks of age, but can appear even later if the bird had 'latent' MD and is substantially stressed. However, if the bird is a few years old, I would suspect a similar disease called Lymphoid Leukosis (which does pass to the egg). Both diseases will produce internal lesions (or tumors), detectable upon post mortem examination, but LL does not produce paralysis. Since it is so difficult to control your birds' exposure to Mareks, (showing, bringing in new birds, airborn spread from other farms), the best course is prevention. That starts with completely sanitizing your brooders. Then consider the Mareks vaccine, which is available in a freeze-dried form through a few of the mail-order suppliers, and is easy to administer to day-old chicks. The downside is that you have to administer the vaccine within one-half hour of mixing it with the fluid it comes with (dilutent), and you have to plan your hatching to accommodate the 'all-or-none' vaccination within a day or two of hatch. (After one hour of mixing the Mareks vaccine, the active virus dies and the vaccine becomes ineffective.) You'll inject the vaccine under the skin at the back of the neck (subtecaneously). Be careful though, you could stick right through to the other side and vaccinate the floor instead of the chick. There are certain 'B factors' contained in the blood of some chickens that make them resistant to Mareks. If you have access to a lab for 'B type' blood testing, 'B factor' birds are desirable for breeding for a 'Mareks-free flock. Overall the easiest way to keep Mareks out of your flock (but not the most effctive) is to promote 'age resistance' by keeping your youngsters separate from the adults and away from the poultry shows until they are over 5 months old.
HOW TO VACCINATE Vaccinate all your chicks at as close to day old as possible. Also
vaccinate
all the adult chickens at the same time.
Vaccinate all the birds within one hour of mixing the dry vaccine wafer
with
the diluent.
Enlist the help of somebody to help you.
Start with the chicks. Have two containers. One to hold unvaccinated
chicks
, and a second to hold vaccinated chicks.
Use a table, and chairs, and good lighting.
Have all the birds caught prior to starting. Have everything prepared
before
mixing.
Mix the vaccine, and follow the instructions, using a TB or 25 gauge
needle.
Have hour helper hold the chick with one hand, and gently grasp it's
head
with the other hand. Pick up the down or feathers with a couple fingers
to
lift the skin on the back of the neck, with your other hand inject the
vaccine under the skin. Feel for a little pop as the needle penetrates
the
skin. If you feel two pops you went through both layers of skin and out
the
other side. if this happens, just do it over. It's a little nerve
wracking
with small chicks, especially bantam chicks but it's entirely doable,
and it
just gets easier and easier.
After vaccinating, make sure you keep your chickens away from any
others for
three weeks afterwards. Infectious Laryngotracheitis (ILT) in Poultry Infectious Laryngotracheitis (ILT) is a viral infection of the respiratory tract (trachea - windpipe) of chickens, pheasants and peafowl. It can spread rapidly among birds and causes high death losses in poultry that are susceptible. The disease is not a human health risk. Turkeys, ducks and geese do not get the infection but could spread the virus. Signs of the diseaseInfected birds will be coughing and gasping, will have difficulty breathing or may simply be found dead. There may be bloody exudate from the nose and mouth. Birds may stand with wings spread, head and neck extended and be struggling for air. Some birds show milder signs, with discharge from the eyes and nose. Up to 100 per cent of a flock can be affected, and up to 30 per cent may die. Birds that recover may be carriers of the virus. They will appear healthy, but can be an ongoing source of virus to infect other birds. Birds that are stressed by transportation or other changes in their environment are more likely to develop the disease or begin shedding the virus. The carrier state can persist for up to two years. Farms may remain contaminated for long periods after outbreaks. Spread of the diseaseILT is most readily spread by direct contact between susceptible birds and infected ones (Figure 1). It may be spread by contaminated equipment and vehicles or be carried into poultry houses on footware or clothing. Humans are the primary culprit in the spread of infection between farms.
Figure 1. Virus can spread between birds
The disease is rare in commercial poultry operations in Alberta. Surveillance is ongoing to detect it, and it is typically found in fancy or hobby flocks. These flocks may be introducing new birds to the flock on an ongoing basis and may not have the isolation that many commercial operations have. Some exotic species such as pheasants and quail can also carry the virus and spread it within mixed fancy flocks. Disease prevention and controlBiosecurity is essential to control diseases such as ILT. The essential elements of biosecurity include the following: - Do not allow other people to enter your barns. This element is critical if these people are in contact with other poultry, especially fancy or hobby flocks.
- If people must enter your barns, they should use boots and coveralls that you provide or be able to assure you that they have not been on another poultry farm that day.
- Use a boot dip to help control disease, and change the dip frequently (daily).
- Do not visit other poultry operations unless necessary. Wash and disinfect your boots and clothing before using them in your own barns after you return.
- Limit vehicle traffic on your farm site to reduce the chances for contamination that you may track into your barns.
- Do not allow animals access to your barns.
- Store all dead carcasses in a closed container to prevent scavengers from dragging them around and spreading viruses or bacteria.
- Do not have fancy birds and commercial poultry on the same farm. Employees of commercial farms should not have fancy flocks on their own farms.
- Perform thorough cleanout and disinfection between flocks. The ILT virus can survive for a long time in a carcass, especially if the carcass is frozen. The virus dies quickly when exposed to sunlight or disinfectants.
Your responsibilitiesIf you suspect a problem with ILT or any other infectious disease, please submit sick or dead birds to a diagnostic laboratory for examination. The disease can only be confirmed by post mortem examination. The ILT policy in Alberta specifies that Alberta Agriculture, Food and Rural Development will notify all commercial poultry operations within a 20 km radius of a farm where ILT has been diagnosed. This notice serves as a warning to producers to be aware of the disease, to enhance the biosecurity of their flocks and to submit any suspicious cases to the diagnostic laboratory for examination. Infectious Coryza Infectious coryza is a specific respiratory disease in chickens that occurs most often in semi-mature or adult birds. Infection may result in a slow-spreading, chronic disease that affects only a small number of birds at one time, or in a rapid spreading disease with a higher percentage of birds being affected. The occurrence of infectious coryza is not widespread and the incidence is relatively low. The disease is caused by a bacterium known as Hemophilus gallinarum. Outbreaks usually result from the introduction of infected or carrier birds into a flock. Transmission of the infection occurs by direct contact, airborne infection by dust or respiratory discharge droplets and drinking water contaminated by infective nasal exudate. Susceptible birds usually develop symptoms within three days after exposure to the disease. Recovered individuals may appear normal but remain carriers of the organism for long periods. Once a flock is infected, all birds must be considered as carriers. The most characteristic symptoms of infectious coryza include edematous swelling of the face around the eyes and wattles, nasal discharge and swollen sinuses. Watery discharge from the eyes frequently results in the lids adhering together. Vision may be affected because of the swelling. The disease results in a decrease in feed and water consumption and an increase in the number of cull birds. An adverse effect on egg production usually occurs in proportion to the number of affected birds. Diagnosis can be confirmed only by isolation and identification of the causative organism. The organism, Hemophilus gallinarum, is extremely fastidious and often difficult to isolate. Prevention is the only sound approach in controlling infectious coryza. It usually can be prevented by management programs that eliminate contact between susceptible and infected birds. It requires only separating affected or carrier birds from the susceptible population. In order to prevent the infection, introduce started or adult birds only from sources known to be free of the infection. If infection occurs, complete depopulation followed by thorough cleaning/disinfecting is the only means for eliminating the disease. A number of drugs are effective for treating the symptoms of the disease although the disease is never completely eliminated. Sulfadimethoxine or sulfathiazole in the feed or water or erythromycin administered in the drinking water can reduce the symptoms of this disease. |
