Livestock Disease Section Mycoplasma Gallisepticum

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. Top 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. Top 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. Top 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. Top 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. Top 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).

The Infection Transmission Symptoms Diagnosis Prevention Step by Step MG Prevention Program