Mycoplasmosis In Poultry

Mycoplasma gallisepticum Infection

M. gallisepticum causes a respiratory disease, affecting the entire respiratory tract, particularly the airsacs, where it localizes. All the airsacs may be involved, become cloudy in appearance, and filled with mucus. In the later stages, mucus develops a yellow colour and cheesy consistency.

Commonly known as 'chronic respiratory disease' or 'CRD', M. gallisepticum infection is extremely important both in broilers and layers. While not a great killer, the disease is of great economic importance.

Affected laying flocks have been shown to produce as many as 20 fewer eggs per year than normal flocks. Also, it is an important egg-transmitted disease. M. gallisepticum infection is a serious problem in our country.The disease is characterized by abnormal respiratory sounds, coughing, and nasal discharge. Symptoms are usually slow to develop and the disease has a long course. 'Complicated CRD (CCRD)" also known as 'airsac disease' is a severe airsacculitis (inflammation of airsac), which occurs when M. gallisepticum infection gets complicated by E. coli and some respiratory virus infections.

Spread

I. Infection is usually transmitted through the hatching egg. This is the major means of spread.

2. Carrier birds (i.e., birds which carry the infection without showing symptoms) are responsible for

transmitting the disease. Direct contact of susceptible birds with the infected carrier chickens causes

outbreaks of the disease.

3. Spread may also occur by contaminated dust, droplets, or feathers carried through the air.

4. People are important carriers.

Symptoms

I. In adult flocks symptoms include abnormal respiratory sounds, nasal discharge, sneezing, coughing, and breathing through the open beak. Feed consumption is reduced and birds lose weight.

2. In laying flocks, egg production decreases, and the disease is usually more severe during winter.

3. In young chicks there is rattling, sneezing, and sniffing, all indicative of a respiratory difficulty.

4. In broilers, most outbreaks occur between 4 and 8 weeks of age.

5. However, the appearance of disease depends, as already mentioned, on the presence at the same time of other disease-producing organisms, or stress factors. Uncomplicated infections usually cause no symptoms, or cause mortality only in the very young.

Postmortem Findings

I. Presence of inflammatory material (exudate) in trachea, bronchi, and airsacs (Fig. 81, 82). Airsacs usually contain cheese-like inflammatory material. Some degree of pneumonia (inflammation of the lungs) may be seen .

2. In severe cases of airsac disease, thin or thick white layer of fibrin covers heart, liver, and airsacs.

These are cases of CCRD.

Diagnosis

I. There are no symptoms or postmortem findings which are characteristic of M. gallisepticum infection in chickens.

2. Demonstration of the organism is the most certain method of confirming the infection.

Treatment

M. gallisepticum is susceptible to several antibiotics. These include streptomycin , oxytetracycline,

chlortetracycline, tiamulin, neomycin, gentamicin, tylosin, erythromycin, lincomycin, enrofloxacin, and others.

Control

I. Treatment is only a temporary solution and is usually quite expensive. Removal of infection is the most satisfactory means of control.

2. Since M. gallisepticum is transmitted through eggs, maintaining chicken flocks free of M. gallisepticum is only possible by obtaining replacement flocks that are known to be free of the infection, and rearing them in strict isolation to avoid introduction of the disease.