Poultry Diseases: Impact, Types and Causes

1. Introduction:

Poultry diseases had made an adverse effect on the industry during past few years. The data and studies related to the impact of poultry diseases and their prevalence is still not enough. The interpretation, forecasting of poultry diseases and their epidemiological analysis is very important at national and international levels.

The monitoring of production and vigilant approach for disease control is very important for producers to minimize the chance of disease occurrence, for that instance a diligent analysis of the monitoring data might be very helpful to devise the new and in the innovation of existing epidemiological strategies. Both bacterial and viral diseases in poultry may cause the significant mortality rates which may discourage the farmers and entrepreneurs in this industry.

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The bacterial pathogens have a vital importance in causing respiratory problems in domestic and commercial poultry. Sometimes after the exposure of bird to viral disease the chances become evident to form bacterial colonies in the respiratory tract (Glisson et al., 1998). The respiratory diseases have got a consequential portion among the overall disease incidence in poultry. Infectious coryza, fowl cholera, Colibacillosis and Bordetallosis comes under this category.

Poultry has been drastically affected by the viral incidences during past few decads. The viral respiratory diseases of poultry may act as a catalyst in the economic loss of poultry worldwide. The notable outcomes of viral infections are the declined egg production and quality, diminished growth and ultimately high mortality (Jones et al., 2010). These diseases are very virulent causing a massive loss in terms of high mortality such as New castle disease and Avian influenza. Infectious laryngotracheitis (ILT), infectious bronchitis (IB) and Turkey rhinotracheitis (TRT) are also important forming a second tier of important diseases. IB alone is responsible for the loss of £23 million per year, reports stated (Jones et al., 2010).

Apart from there are multiple factors which may become the responsible factor for the respiratory distress. It includes some fungi such as aspergillus which cause aspergillosis in poultry, a condition of acute or chronic respiratory problem in chickens. The intensive poultry production is an emulous business providing a narrow window for profit, so a small negligence in managing expenditures related to medication and vaccine or in ensuring good health status may put the business at the risk of massive loss. Therefore the integrated surveillance and the preventive measures are needed to avoid any loss, which will be discussed in this study.

2. Bacterial respiratory diseases of poultry:
   1. Infectious Coryza:

It is one of the acute respiratory diseases of poultry. This disease can be seen predominantly in commercial laying flocks in different parts of USA, merely present in broilers (Merck, 2010). Primarily the disease is limited to the birds and do not have public health concerns but it causes huge economic losses in chickens in terms of reduction in growth and 10-40% drop in egg production in laying birds (Blackall et al.,1989).

1. Causative agent: Haemophilus paragallinarum (Blieck et al., 1932).
2. Signs and Symptoms: Nasal and ocular discharge, Conjuctivitis, facial odema and swollen wattles.
3. Morbidity and Mortality: depending on the virulence of the pathogen may alter the duration of disease, it usually characterized by low mortality and high morbidity (Delaplane et al., 1934). In severe and prolonged conditions may cause high mortality.
4. Treatment: Different antibiotics and sulfonamides were found to be useful in diminishing the severity of the infection. Oxytetracycline and erythromycin are the commonly used antibiotics. But drug resistance has been indicated during the course of time (Reece et al., 1985).

2. Fowl Cholera (Pasteurellosis):

It is known to be a disease of both wild and domesticated birds. Disease will appear as a septicemia in the start and then followed by benign and chronic condition later characterized by the high morbidity and mortality (Richard et al., 1997). The pathogen is capable of releasing virulent and non-virulent endotoxins. Affected birds may remain carriers and will act as a reservoir of infection (Pritchett et al., 1930). Domestic geese were found to be susceptible to fowl cholera (Van es et al., 1940).

1. Causative agent: Pasteurella Multocida (Pasteur et al., 1880).
2. Signs and symptoms: Affected birds will show the signs related with loss of appetite. 5-15% drop in egg production in laying birds has been observed. Bluish comb and wattles are the evident signs observed in the birds died of acute fowl cholera (Merck 2010).
3. Morbidity and Mortality: This disease is characterized by the high mortality particularly in the laying hens. The infection seldom occurs in broilers. 0-20% mortality has been reported. 17-68% mortality was seen in turkeys during an outbreak, described by (Alberts et al., 1948).
4. Treatment: The use of antibiotics based on the sensitivity test has proved to be effective in treating fowl cholera up to maximum extent. Studies has illustrated that prolonged delay in medication may lead to the chronic condition (McNeil et al., 1948).

3. Bordetellosis:

It is known to be a highly contagious upper respiratory tract disease in poultry. The exposure of the bird to disease will favor the bacteria to make colonies in the ciliated epithelium of upper respiratory tract, resulting in the onset of clinical signs (Skeeles et al., 1997). Another synonym for this disease is ‘Turkey Coryza’ because the clinical signs are much related to the infectious coryza in chickens. Bordetellosis is highly concerned disease in the turkey producing region of USA, Canada, Australia and Germany (Boycott et al., 1984). However it is evident that the cause of turkey rhinotracheitis in UK, France and South Africa includes some viruses and other pathogens in addition to bordetalla avium (Lister et al., 1986).

1. Causative agent: Bordetella avium (Filion et al., 1967).
2. Signs and Symptoms: Sneezing, altered vocalization, collapsing of trachea, oculo-nasal discharge followed by impaired growth, submaxillary odema and dyspnea.
3. Morbidity and Mortality: The disease is known to be lethal in a way causing high morbidity in 2-6 week age of turkeys. 80-100% morbidity has been reported (Saif et al., 1980) with very less incidence of mortality i.e. 10%. Whilst the less chance of mortality and low morbidity of 20% in breeder flocks was suggested by (Kelly et al., 1986).
4. Treatment: A nominal improvement has been observed by the use of ordinary antibiotics. The treatment of infected flock with potassium penicillin-G at the dose rate of 10⁶ IU per gallon of drinking water and 1.8g tetracycline HCl for three days has shown maximum recovery in 24 hours (Kelly et al., 1986). In an experimentally infected flock of turkeys the aerosol treatment of flock by oxytetracycline HCl has shown positive effects by prolonging symptom development and curtailing bacterial numbers in trachea (Alsteen et al., 1985).