Prevalence of infectious diseases in Sonali chickens at Bogra Sadar Upazila, Bogra, Bangladesh

Objective: The study was conducted to determine the prevalence of infectious diseases in Sonali chickens at Bogra Sadar Upazila, Bogra, Bangladesh. Materials and methods: A total of 258 sick and dead Sonali chickens were examined for the diagnosis of different infectious diseases based on history, clinical findings and postmortem lesions of dead and sacrificed birds. Results: Infectious Bursal disease (IBD) was recorded in 14.72% (n=38/258) cases. Similarly, Newcastle disease (ND), Coccidiosis, Colibacillosis and Mycoplasmosis were recorded in 11.24% (n=29/258), 13.95% (n=36/258), 14.72% (n=38/258), 12.79% (n=33/258) cases, respectively. Mixed infection of IBD, ND and Coccidiosis found in 16.67% (n=43/258) birds. On the other hand, mixed infection of IBD, ND and colibacillosis was recorded in 15.89% (n=41/258) cases. Conclusion : It is concluded that several infectious diseases are commonly present in Sonali chicken in the study area of Bangladesh. Mixed infections are more prevalent as compared to single infection. Proper hygienic management and appropriate vaccination should be taken in consideration for effective control the diseases. Further microbiological and molecular diagnoses are suggested for detail studies of these diseases and their pathogens.


INTRODUCTION
Poultry industry plays an important role in Bangladesh in fulfilling the protein demand of human (Islam et al. 2014a). It is considered as the farmers' first investment in the livestock ladder as a way of income generation. The poultry meat alone contributes a substantial 37% of the total meat production in Bangladesh (Begum et al., 2011). The commercial poultry production by the private sector is expanding rapidly in Bangladesh. This industry can provide opportunities for the increase of Gross Domestic Product (GDP) growth rate through ensuring food security and self-employment, and finally reducing poverty.
Sonali chickens are well adapted in the environmental conditions of Bangladesh, as it requires less care and attention as compared to other breeds. It is also easier for women to rear (Saleque and Saha, 2013). In spite of many positive reasons behind rearing of Sonali chickens, there are some causes that hamper in optimum production of Sonali chicken by smallholder households in Bangladesh (Biswas et al. 2006). Poultry diseases are one of the major constraints for developing poultry industry in Bangladesh (Islam and Samad, 2004). Prevalence of diseases in a particular area depends on various factors like geo-climatic condition, management practices, immunization status, and social awareness.
Prevalence of infectious diseases is considered for establishing a commercial poultry farm. The northern part of Bangladesh is considered as a poultry hub especially of Sonali chicken, which is used as meat purpose. Biswas et al. (2006) reported that about 28% mortality of Sonali chickens in southeastern coast of Bangladesh due to outbreak of several infectious diseases. However, very few studies have been reported on prevalence of infectious diseases of chickens of northern part of Bangladesh. Thus, this study was aimed at investigate the prevalence of various infectious diseases of Sonali chickens in the northern part of Bangladesh.

MATERIALS AND METHODS
The study was performed at District Livestock Hospital, Bogra from September to November, 2015. It was noted prevalence of infectious diseases was comparatively higher in late autumn period as compared to other seasons of the year (Gunnarsson et al., 2012). So, our experiment was performed covering that season. A total of 258 sick and dead Sonali chickens were examined for diagnosis of diseases. The live birds were sacrificed according to standard animal care guidelines giving them minimum pain. The clinical findings and owner complaints were also recorded.

Diagnosis of Disease:
The birds were examined and recorded the post mortem findings as per the method described by Swayne et al. (2013). The clinical signs and post-mortem findings of different diseases are mentioned below.

Infectious bursal disease (IBD):
The observed clinical signs of IBD were severe depression, inappetance, ruffled feather, vent pecking, limy diarrhea, and rise of body temperature. Post mortem findings included hemorrhages in the thigh and pectoral muscles, swollen and enlarged bursa. Kidneys are enlarged and urate deposition in the tubules.

Newcastle disease (ND):
The observed clinical findings of ND were sudden death, fluff up feathers, body coat dragging on the ground, lethargy, inappetance, respiratory distress, gasping and greenish diarrhea. Nervous signs included tremor, torticollis, convulsion and paralysis of wings and legs. Post-mortem findings included pin point hemorrhages at the tip of proventricular glands, hemorrhage and necrotic ulceration on the intestine and cecal tonsils, and marked congestion of trachea.

Colibacillosis:
The observed clinical findings of colibacillosis were coughing, sneezing, reduced appetite, poor growth and omphalitis. Whitish covering on liver and heart, edematous epicardium covered with yellowish and fibrinous exudates, enlarged and congested yolk sac were observed in post-mortem examination.
Coccidiosis: Bloody diarrhea, dehydration, depression, emaciation, and poor growth rate were demonstrated as clinical findings. Post-mortem findings showed hemorrhages and engorged clotted blood in cecum.

Mycoplasmosis:
The clinical signs of mycoplasmosis included tracheal rale, nasal discharge, coughing, facial edema, lacrimation and reduced feed consumption. In post-mortem findings, cloudy air sac, pericarditis, perihepatitis, congested and mucoid trachea were demonstrated.

RESULTS AND DISCUSSION
Among the 258 Sonali chickens examined in this study, IBD was recorded in 14.72% (n=38/258) chickens, whereas ND, Coccidiosis, Colibacillosis and Mycoplasmosis were found in 11.24% (n=29/258), 13.95% (n=36/258), 14.72% (n=38/258), and 12.79% (n=33/258) samples respectively ( Table 1). A mixed infection of IBD, ND and Coccidiosis was found in 16.67% (n=43/258) samples, and IBD, ND and Colibacillosis was found in 15.89% (n=41/258) chickens ( Table 1) (Camilotti et al. 2016). In our study, mixed infection of the diseases were very common in the study area. Therefore, unhygienic environment of the farm might be increases the susceptibility of infection.    Coccidiosis was recorded 13.95% chickens in our study, which is higher than the findings of Our present study depicted that mycoplasmosis is the most common infectious disease occurred before winter season, which supports report of Sarkar et al. (2005).
The present study revealed that 16.67% of Sonali chickens were affected with IBD, ND and Coccidiosis infections. Prevalence of mixed infection of the disease in Sonali chicken is higher than single infection. It might be due to unhygienic environment, increase humidity, and poor litter management, which increases the susceptibility of mixed infections. A mixed infection of IBD, ND and Colibacillosis was recorded in 15.89% cases. Immunocompromised birds increase the susceptibility of mixed infection, as reported by Toro et al. (2006).

CONCLUSION
Prevalence of mixed infection of various diseases is common in Sonali chickens as compared to single infection. Proper housing, feeding and hygienic environment can be provided to reduce the disease prevalence of infectious diseases in Sonali chickens. Further microbiological and molecular diagnoses are suggested for detail studies.