CRD in Poultry- Chronic Respiratory Disease is one of the most common respiratory diseases of poultry.The disease occurs when birds infected with Mycoplasma gallisepticum are stressed. The subsequent invasion by secondary bacteria causes the major damage to the bird. The microorganisms of the class Mollicutes (Mycoplasma) were first identified in 1898 as the etiologic agent of the bovine contagious pleuropneumonia (BCPP) & thereafter all similar agents were named pleuropneumonialike (PPLO-like) organisms.
Species Affected by Chronic Respiratory disease (CRD): Poultry,Turkeys,Game Birds,Pigeons, and Passerine Birds of all ages.
CRD in Poultry- Chronic Respiratory Disease' Cause:
The underlying cause of CRD in Poultry is Mycoplasma gallisepticum (MG).The condition is frequently triggered by respiratory viruses such as ND and IB and subsequently complicated by bacterial invasion.The main agents involved in the infection are Mycoplasma gallisepticum and E. coli. Stress caused by moving the birds, by debeaking, other operations/handlings or other unfavourable conditions e.g. cold or bad ventilation, make the birds more susceptible. Avian mycoplasmosis can be caused by several species of Mycoplasma (class Mollicutes, order Mycoplasmatales, family Mycoplasmataceae) including Mycoplasma gallisepticum, M. synoviae, M. meleagridis and M. iowae. M. gallisepticum is the most important pathogen in poultry. It also causes disease in other avian species. M. gallisepticum infections are also known as chronic respiratory disease (CRD) of chickens, infectious sinusitis of turkeys and house finch conjunctivitis. Several strains of M. gallisepticum have been reported, including the R (poultry), P (psittacine) and house finch strains. Strains may vary greatly in their pathogenicity for different species of birds. In one study, budgerigars developed severe disease after experimental infection with the R strain of M. gallisepticum but not the house finch strain.
Etiology Mycoplasma gallisepticum + chronic stress factor + secondary coliform organisms cause respiratory disease Species susceptible Chickens, turkeys, pigeons, ducks,Peafowl and passerine birds. Incidence Very widespread and present in most, if not all commercial flocks. Each batch of new pullets will become infected.
Transmission of CRD in Poultry :
The main problem is that parent birds infected with Mycoplasma gallisepticum can transmit the organism through the egg to their offspring (vertical transmission). In addition, infection can occur by contact or by airborne dust or droplets (horizontal transmission). The incubation period varies from 4 days to 3 weeks.
Egg Transmission - of major importance and the means by which the disease perpetuates itself. Airborne (aerosol) - generally rapid, but does not travel distances. Indirect or mechanical - the major means of entry of CRD is by the introduction of infected carrier birds or transport by persons such as service personnel, vaccinators and blood testers. The risk is great when people handle CRD-free birds on the same day after handling CRD-infected birds. Transfer can also occur on equipment (crates, vehicles, and vaccinating equipment).
Clinical Signs of CRD in Poultry :
Young chickens (broilers or layer pullets) will show respiratory distress. The birds frequently show lack of appetite, decreased weight gain and increased feed conversion ratios. In adult birds the most common signs are sneezing and general respiratory distress. In laying birds a drop in egg production between 20-30 % can occur. In breeders hatchability can be affected and day-old chick quality produced from hatching eggs coming from infected flocks will be reduced.
Sign of CRD in Poultry :
• Nasal and ocular discharge, (watery eyes) rattling in the wind pipes, coughing, gasping (dyspnea), sneezing and shaking of the hed.
• Feed consumption drops off leading to decreased egg production and loss of weight.
• Male birds frequently have the most prominent signs.
• Reduced hatchability and chick viability.
• Occassional encephalopathy and abnormal feathers In Broilers
• Most outbreaks occur between 3rd and 6th weeks ofage.
• Poor feed conversion, sharp decline in weight gain.
• Slow growth
• Leg problems
• Morbidity rate fairly high but not great mortality.
• Poor carcass quality, high contamination rate. Thin and weak birds with razor-blade breasts.
Diagnosis of CRD in Poultry :
Diagnosis of MG infection can be made based on clinical signs and post mortem lesions followed by confirmation in the laboratory using blood (serum) samples for serology or organs swabs for identification by PCR or mycoplasma isolation. Respiratory virus infection (Newcastle disease or infectious bronchitis) with secondary infection (E. coli, etc.) can give similar lesions.
Internal Lesions of CRD in Poultry :
A reddish inflamed trachea and/or frothy, cheesy exudate in the airsacs, especially in complicated cases (e.g. with secondary E. coli infections) are observed. In mild MG infections the only lesion might be slight mucus in the trachea and a cloudy or light froth in the airsacs.
Post Mortem Lesions of CRD in Poultry :
In uncomplicated cases in chickens, the lesions typically include mild sinusitis, tracheitis and airsacculitis. If the chicken is infected concurrently with E. coli, thickening and turbidity of the air sacs, exudative accumulations, fibrinopurulent pericarditis and perihepatitis may be seen. In turkeys, severe mucopurulent sinusitis may be found, with variably severe tracheitis and airsacculitis. Lesions reported in naturally infected chukar partridges and pheasants include conjunctivitis and sinusitis of one or both infraorbital sinuses. Finches typically exhibit mild to severe inflammation in one or both eyes and the periorbital region. The eyelids may be swollen and inflamed, and a clear to cloudy, thickened ocular discharge may be noted. There may also be drainage from the nares.
In Turkeys There are two forms of this disease in the turkey. With the “upper form” the birds have watery eyes and nostrils, the infraorbitals (just below the eye) become swollen, and the exudate becomes caseous and firm. The birds have respiratory rales and show unthriftiness. With the “lower form” infected turkeys develop airsacculitis. As with chickens, birds can show no outward signs if the infection is uncomplicated. Thus, the condition may go unnoticed until the birds are slaughtered and the typical legions are seen. Birds with airsacculitis are condemned, Production is lower in infected flocks, decreased weight gain, feed efficiency and egg production.
Morbidity and Mortality :
In chickens with uncomplicated infections, the morbidity rate is high and the mortality rate low; however, more severe disease occurs if the birds are concurrently infected with other viruses or bacteria. Mortality rates can be high in turkeys. In wild songbirds, the impact of the disease is complicated by other factors. Under controlled experimental conditions, house finches exhibited morbidity rates approaching 100%, but low mortality rates of approximately 5% or less.
M. gallisepticum infections can cause significant economic losses on poultry farms from chronic respiratory disease, reduced feed efficiency, decreased growth and decreased egg production. The carcasses of birds sent to slaughter may also be downgraded. M. gallisepticum infections are notifiable to the World Organization for Animal Health (OIE). This organism has been eradicated from most commercial chicken and turkey breeding flocks in the United States; however, it remains endemic in many other poultry operations.
CRD in Poultry does not normally cause an alarming number of deaths. The effect is more of a chronic nature causing reduced weight gain and higher feed conversion ratios in broilers and lower egg production in breeders and layers. In this way the overall economic losses can be very high.
Treatment of CRD in Poultry :
- Disinfect the farm and equipments with right disinfectant i.e. Viraclean
- Ciprocolen is the best and time tasted medicine for CRD in Poultry
- Chicks arrived from known infected parent flocks should be treated with a suitable Ciprocolen during the first 48 hours after placement and then subsequently at 20 - 24 days for 24 to 48 hours period.
- Efforts should be made to reduce dust and secondary infections. Improve the ventiliation for having good results of medicine.
- All poultry drinking water should be treated with Aquacure .
Prevention of CRD in Poultry :
- Establishment of Mycoplasma free breeding flocks.
- Before purchasing chicks from a hatchery, it should be confirmed that they are free from CRD.
- Chicks should be raised at the place where there is no approach of infected birds.
- Complete fencing of the breeding farms and sufficient isolation of prevent airborne infections from infected flocks.
- Disposing of dead birds by incineration, deep burial or by means of special disposal pits.
- Using vaccines that are free from contamination of Mycoplasma gallisepticum.
- Construction of the houses must be done in such a way that prohibit the entrance of any type of wild birds and wandering animals.
- Prohibition of visitors in the farm.
- Before coming in contact with flocks, workmen should take shower and put on special clothes.
- House infected and uninfected flocks at least 50 to l00 m apart. Prevent the disease spreading by adopting basic principles of isolation and all-in, all-out management and buy vaccinated pullets.You should also read Cause & Prevention of Poultry Diseases
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