MYCOPLASMOSIS IN THE COMMERCIAL POULTRY

MYCOPLASMOSIS IN THE COMMERCIAL POULTRY

Also known as: Avian Mycoplasmosis, Chronic Respiratory Disease

 

Compiled &  Edited by-DR. RAJESH KUMAR SINGH, (LIVESTOCK & POULTRY CONSULTANT), JAMSHEDPUR, JHARKHAND,INDIA
9431309542, rajeshsinghvet@gmail.com

 

Avian mycoplasmosis which is an important disease condition in birds is caused by four (4) commonly recognized pathogens: Mycoplasmagallisepticum(MG), Mycoplasma synoviae(MS), Mycoplasma meleagridis(MM)and Mycoplasma iowae (MI). Other mycoplasmas have also been incriminated in mycoplasma infections in birds  but are not pathogenic, so this review will focus mostly on MG and MS. This present review focused on clinical signs, transmission, economic significance, methods of diagnosis, treatment, prevention and control and researches done in Nigeria and it is aimed at increasing the research interest in avian mycoplasma in the country.

Avian mycoplasmosis is a disease which is worldwide in occurrence and is extremely important to both the broiler grower and the table-egg producer . It is caused by mycoplasma organisms of the Class Mollicutes. These organisms are different from other bacteria; they are of very small sizes  and do not have a cell wall . These characteristics account for the “fried egg” type of colonial morphology exhibited by mycoplasmas, their complete resistance to antibiotics that affect cell wall synthesis and their complex nutritional requirements . Avian mycoplasmas are also host specific (for instance, Mycoplasmameleagridis infects turkeys only)

Mycoplasma in poultry is not a new disease. There is mention in the old books of similar symptoms from about 100 years ago but it has generally been called roup or a common cold. Treatment tended to be by culling only.

The disease acquired the name mycoplasma once the causative organism had been discovered. Mainly the respiratory system in poultry is affected and the disease may be becoming more common, spreading with increased travelling of stock, more people keeping chickens and mixing them from different sources. The incubation period before clinical signs appear can be as little as a few days – it is very infectious. It appears to thrive in the bird when other pathogens are present, such as E. coli or infectious bronchitis (IB is certainly now more common in free-range flocks) or if the birds are stressed or debilitated. Debilitating factors include nutritional deficiency, excessive environmental ammonia and dust and stressors such as changes in the pecking order or exhibitions.

 

Causes and clinical signs————

 

 

The organism is neither a bacterium nor a virus in size, but part way between, having no cell wall but with a plasma membrane. Four out of the known 17 species of mycoplasma are pathogenic in poultry:

Mycoplasma gallisepticum: signs can include foamy eyes, sneezing, nasal discharge, swollen eyelids and sinuses, reduced egg production and gasping in chickens, turkeys and pheasants, swollen sinuses in waterfowl. This one is the main culprit in backyard flocks.

Mycoplasma synoviae: signs include swollen and hot joints in chickens and turkeys and/or respiratory signs as above, or thin, deformed shells at the broad (apical) end of the egg.

Mycoplasma meleagridis: signs include poor growth in turkey poults and lowered hatchability in turkey breeders.

Mycoplasma iowae: signs included reduced hatchability in turkey breeders, twisted legs in turkey poults.

When nasal discharge is evident, feathers become stained with this as the bird tries to clean its eyes and nostrils. There is a particular sweet smell associated with this discharge which to the sensitive nose is immediately apparent when entering a hen house.

Transmission————

 

 

Nasal discharge and cool temperatures are protective of the organism so any sneezing will deposit droplets which will remain infective for several days. Transmission is also through the egg, plus carried on the clothes and hands of people tending the birds. Mycoplasmas are transmitted laterally by contact , infectious aerosols coughed and sneezed by infected birds , through contaminated feed, water, contact personnel and communicant animals mainly birds  and vertically through the eggs . Veneral transmission is particularly important in the case of MM . MS infection can also be through the conjunctiva and upper respiratory tract . It has beenreported by that M. gallinarum and M. gallinaceum have been isolated from the oviduct of chickens. This suggests that egg transmission of this species is possible.According to , infected birds carry MG for life and can remain asymptomatic until they are stressed.

Ages Of Birds Affected ————

All ages of chickens and turkeys are susceptible to avian mycoplasmosis although young birds are more prone to infection than the older ones ; it seems that some resistance develops with age

Economic impact————

 

Economic Significance– MG has been ascribed to be the most economically important of the pathogenic mycoplasma species affecting poultry due to the significant losses occurring from decrease in egg production, decrease in egg quality, poor hatchability(high rate of embryonic mortality and culling of day old birds), poor feed efficiency, an increase in mortality and carcass condemnations and medication costs. Economic losses in the poultry industry caused by this infection have been noted to be significant  the infection has been reported by  to reduce egg production in layers and broiler breeder chickens by 10-20%.

 

Reduced egg production and reduced weight gain in chickens, turkeys, waterfowl and pheasants.

Diagnosis—————

 

History, clinical signs, and typical gross lesions may be suggestive of M gallisepticum infection. Serology by agglutination and ELISA methods are commonly used for surveillance. Hemagglutination-inhibition is used as a confirmatory test, because nonspecific false agglutination reactions may occur, especially after injection of inactivated oil-emulsion vaccines or infection with M synoviae. M gallisepticum should be confirmed by isolation from swab samples of infraorbital sinuses, nasal turbinates, choanal cleft, trachea, air sacs, lungs, or conjunctiva. Primary isolation is made in mycoplasma medium containing 10%–15% serum. Colonies on agar medium are used for species identification by immunofluorescence with species-specific antibodies. PCR can also be used for detection of M gallisepticum DNA using swabs taken directly from infected sites (choana, sinuses, trachea, air sacs) or after growth in culture.

Mycoplasma isolates must be identified by species, because birds may also be infected with nonpathogenic mycoplasmas. E coliinfection, Newcastle disease, avian influenza, and other respiratory diseases (eg, infectious bronchitis in chickens) should be considered in the differential diagnosis and can act as inciting or contributing pathogens.

 

Post Mortem Lesions———

Gross post mortem lesions——-

On post mortem examination, lesions may be found throughout the upper and lower respiratory tracts. Catarrhal exudates may be present in the nasal passages, infra orbital sinuses, trachea and bronchi . Mild sinusitis, tracheitis and air sacculitis are observed in uncomplicated cases of mycoplasmosis in chickens. Thickening and turbidity of the air sacs, Exudative accumulations, fibrinopurulent pericarditis and perihepatitis may be seen in cases where the chicken is concurrently infected with E. coli . In turkeys severe mucopurulent sinusitis may be found with variable severe tracheitis and air sacculitis . Interstitial pneumonia and Salpingitis are often seen in chickens and turkeys ; other findings may include conjunctivitis, corneal opacities and peri ocular edema . The severity of these lesions is variable depending on the virulence and pathogenicity of the infecting strain, concurrent respiratory pathogens and stress factors .

Differential Diagnosis ———

 

Differential diagnosis in poultry includes respiratory diseases such as infectious bronchitis, mild Newcastle disease and avian influenza . Other pathogens to be considered include Hemophilusparagallinarum, and Pasteurellamultocida, while avian pneumovirus, Pasteurellamultocida and Chlamydia are also to be considered in turkeys. Mixed infections with Mycoplasma gallisepticum and other organisms can occur

 

Treatment———————

 

It has been reported  that the treatment of mycoplasma infected breeders with anti microbials decreases the rate of clinical manifestations and consequently also decreases the risk of transovarian transmission. It was stated  that although this procedure is recommended for laying hens, it doesn’t eliminate MG,MS OR even MM from the flock. Many antimicrobial agents such as oxytetracycline, amino glycosides, lincosamides, fluoroquinolones, tylosin and tiamulin have been shown to possess different degrees of in vitro activity against various veterinary mycoplasmas .An impressive effect of tylosin on Mycoplasma infected chickens has been recently reported . However, increasing resistance of mycoplasma against tetracyclines, macrolides  and quinolones  has been reported in animal and human species. Mycoplasmas have higher mutation rates than conventional bacteria which mean that they can rapidly develop resistance to other drugs including the oxytetracyclines and tylosin as has been reported in Europe . The massive use of antimycoplasma drugs resulted in development of antimycoplasma drug resistant MS and MG strains .However, the carrier status of infected flocks is not eliminated by treatment. It only suppresses the excretion of the micro organism in respiratory exudates and eggs

 

Antibiotic treatment will not completely cure the disease but will reduce the incidence to a tolerably low level. Tylan Soluble is licensed for the treatment of mycoplasma and is probably the best treatment. Baytril Oral should not be used in laying hens as it will take them out of the food chain. Tylan Soluble is effective in young stock but seems to be less effective in older stock unless given at the acute (early) stage of the disease. If still showing signs after treatment the bird must be culled as the organism will be too deeply entrenched within the airsacs and hollow bones to be removed, the bird remaining a carrier which will infect others. (Denagard is sometimes prescribed for chickens: this drug combined with the coccidiostat in a grower ration becomes fatal, so only use it in adults on a layer ration).

Control And Prevention Strategies ————

The prevention of mycoplasmosis in poultry includes the acquisition of birds free from MG, MS,MM or MI and constant monitoring of breeder flocks. These flocks free of MG should be sustained by maintaining replacements from mycoplasma-free sources in a single-age, all in all out management system . Control of avian mycoplasmosis consists of good biosecurity and proper hygiene. Although medication can be very useful in preventing clinical signs and lesions as well as economic losses, it cannot eliminate infection from a flock, it is not a satisfactory long term solution . Control by medication is necessary to complimentbiosecurity measures to minimize economic losses, lateral and vertical transmissions . It has been reported by that vaccination against MG and MS can be a useful long term solution in situations where maintaining flocks free of infection is not feasible especially in multi-age commercial egg

productionsites. Vaccines generally prevent egg production losses and reduce respiratory disease impact in commercial layers and can also help in the eradication or reduction of egg transmission in breeder flocks . Infections can be eliminated from a farm by depopulation of the flock, followed by thorough cleaning and disinfection of the premises . Most commonly used disinfectants are thought to be effective for MG. Recommended disinfectants for buildings and equipment include phenolic or cresylic acid disinfectants, hypochlorite, and 0.1% glutaraldehyde. Mycoplasmas are typically fragile and only survive in the environment for a few days therefore, birds can be re-introduced after two weeks

Prevention

• Keep stressors to a minimum or if a known stressor such as a show is imminent, give vitamin supplementation. There are several useful products on the market which contain probiotics and/or vitamins, administered in the water.
• Use a suitable disinfectant for both huts and equipment such as Virkon or F10.
• Keep dust and ammonia levels low by having (vermin-proof) ventilation on two sides of the hut at the top and never closing it off. Ammonia paralyses the small hairs (cilia) which act like an escalator to move normal mucus up the trachea before being swallowed.
• Feed high quality commercial food for the stage of growth and the species of bird.
• Monitor weather changes and take steps to minimise any effects.
• When attending to the stock, begin with the youngest at the start of the day (i.e. with clean clothes).
• Either quarantine new stock for 2-3 weeks or treat with Tylan Soluble as soon as the birds are obtained if there has been mycoplasma in your flock.
• Do not buy from auctions.
• If adult stock are kept symptom-free the risk of passing mycoplasma on through the egg is reduced.
• If young stock happen to be exposed to a mild bout of mycoplasma they will acquire a certain amount of immunity as long as there are no other pathogens (such as coli) present.
• Cider vinegar (10ml:500ml, plastic drinker only to avoid zinc toxicity) helps strengthen the immune system and keeps drinkers cleaner. Use one week a month, more often if diseases are present.

Reference-On Request