Prevalence and pathology of Newcastle disease in broiler at Bochaganj Upazila of Dinajpur , Bangladesh

The study was schemed to investigate the prevalence, pathological conditions, mortality and clinical features of Newcastle disease in the small scale commercial broiler farms at Bochaganj upazila of Dinajpur district during January to June, 2014. A total 1950 birds (from 5 farms), among which 160 diseased and dead birds were selected out of which 99 (5.35%) birds were found to be positive for Newcastle disease. The clinical signs of the affected birds were sneezing, coughing, nasal discharge, laboured breathing, and torticolis. Broiler were inactive, weak and rough in appearance, greenish watery diarrhoea occur severely. Nervous sign include clonic, spasm and paralysis of the legs and wings. In this observation, the gross pathological lesions were slight to severe haemorrhages in caecal tonsils, typical lesions were proventricular haemorrhage, most commonly seen in the surface near the junction with the proventriculus. The prevalence of Newcastle disease in Bochaganj upazila was 5.35%. Mortality of Newcastle disease in non-vaccinated and vaccinated broiler flock was 20.76% and 4.6%, respectively.


Introduction
In the recent years poultry rearing has become a growing and prospective industry in Bangladesh.Poultry rearing can play a vital role in the country like Bangladesh where most of the people are landless, disadvantaged and devoid of formal education or skill to participate in income generating activities.The vast majority of the world's hungry people live in developing countries, where 13.5% of the population is undernourished (WFP, 2015).The average quantity of protein uptake by people is insufficient per head per day where as desirable requirement is decreasing daily per head day by day.The country has a population of 16 million people who need a daily protein requirement of 70 to 100 grams a day.Currently, the average poultry meat consumption is just one kilogram a person a year, while just 28 eggs per person are eaten each year, (Peter, 2014).Despite the special emphasis of the state on this sector, the development of poultry industry is seriously threatened by the outbreaks of acute contagious and fatal diseases.Among them Newcastle disease (ND), also known as Ranikhet disease, is one of the major problems in the development of poultry industry in Bangladesh.Newcastle disease is a deadly viral disease of poultry due to its high and rapid spreading nature among poultry and other domestic and semi domestic species of birds.It is caused by Avulavirus, a newly formed genus under Paramyxoviridae (Chang et al., 2001;Mayo, 2002).The virus mainly infects birds through their respiratory and gastrointestinal tract (Alexander, 1988).Depending on the strains of virus and how it reacts it causes huge economic losses to the poultry industry due to its high mortality rate in acute cases.The owner of the small scale farm faces many problems and loses their birds due to Newcastle disease infection that cause major economic loss.In the present study, gross and histopathological lesions produced by Newcastle disease virus (NDV) in various organs of diseased and dead birds were observed with their prevalence in broiler in Dinajpur district, Bangladesh.

Research area
Samples were collected from the small scale commercial broiler farms at Bochaganj upazila of Dinajpur district and research was conducted in the laboratory of Department of Pathology and Parasitology, Hajee Mohammad Danesh Science & Technology University, Dinajpur during January to June, 2014.

Experimental chickens
A total of 1950 birds of five farms were observed and 160 diseased and dead birds were examined for ND.

Clinical study
The general health condition and age of the chicken were recorded.The chickens were observed to detect clinical signs by usual inspection.The clinical signs were recorded during the physical visit of the affected flocks and the farmer's complaints about the affected birds were also considered.

Gross lesion
Gross morbid lesions of different organs were observed after necropsy examination of the birds.

Histopathological examination
During necropsy, various organs having gross lesions were collected, preserved and trimmed at 10% formalin.Formalin-fixed samples of the caecal tonsil, proventiculus and intestine from the diseased and dead chicken were processed for paraffin embedding, sectioned and stained with haematoxylin and eosin according to standard method (Luna, 1968) for histopathological study.

Results
Pathological investigation of Newcastle disease encountered in small scale commercial broiler farms at Bochaganj upazila in Dinajpur district was studied and different clinical, necropsy and microscopic conditions were recorded during the study period.

Clinical examination
The clinical signs of the birds affected with NDV varied from farm to farm.The signs were sneezing, coughing, and torticollis of the neck and shaking of the head.Chicken showed marked depression, inactive and weak.Sometime complete inability to make sound.Greenish watery diarrhoea occurred.Nervous sign include paralysis of the neck and legs.

Status of prevalence and mortality of the disease
The study revealed the following status of mortality and prevalence of Newcastle diseases virus (NDV) in broiler.Table 1 showed the prevalence of ND at different region of Bochaganj upazila of Dinajpur district.A total of 1950, among which 160 birds were selected during the study period from which 99 birds were found infected with ND.The prevalence of ND was 5.35%.Mortality rate of vaccinated broiler was 4.65% and in nonvaccinated broiler was 20.76% showed (Table 2).The total mortality rate was 4.5 times higher in nonvaccinated than in vaccinated birds.The percentages variation of most common gross lesions that were found in different organs during postmortem examination are presented in Table 3.

Necropsy examination
Gross pathological changes in different samples were nearly similar but varied in severity.These included slight to severe haemorrhages in the proventiculus (Figure 1), haemorrhage in the internal wall of intestine and haemorrhage in caecal tonsils.

Histpathological study
Histopathological changes in proventiculus are distortion of normal architecture of tissue.Necrosis and haemorrhages around the gland, globular destruction of the proventiculus (Figure 2).Severe epithelial layer destruction in the proventiculus (Figure 3).Haemorrhage in the proventiculur section.

Discussion
A total 1950 birds, among which number of infected birds 160, out of which 99 affected broiler chickens were examined as NDV and observed clinical signs were sneezing, coughing, nasal discharge, laboured breathing, and torticolis which correspond with the findings of Okoye et al. (2000).Greenish diarrhoea which was also similar with the findings of Alexander (1993).Nervous system was marked by paralysis of legs, neck and wing which correspond with the findings of Ressang et al. (1961).
Prevalence of NDV at different small scale commercial broiler farms in Bochaganj upazila are showing in Table 1 where total 5 farms visited in this upazila.Total 160 diseased and dead birds were examined out of which 99 birds were found to be positive for NDV.The prevalence of ND at Bochaganj was 5.35% which were dissimilar with the findings of Yuguda et al. (2007) who stated 46% prevalence in Borno state of Nigeria.Salihu et al. (2012) stated 54.67% prevalence.Njagi et al. (2010) stated 17.8% prevalence in hot dry zone and 9.9% in cool wet zone.The variation of prevalence may be due to variation in geographical location, seasonal variation, species variation, managemental error and so on.
Out of 130 non-vaccinated birds, 27 died due to ND and mortality rate was (20.76%), whereas out of 130 vaccinated birds, 6 died of ND and 4.6% mortality rate showed in Table 2.The relative risk of NDV was 4.5 times higher in nonvaccinated birds than vaccinated one.In vaccinated flock death from ND might be due to vaccination failure (wrong time vaccination, wrong route, use of denaturated vaccine etc.), improper management.The mortality was 4.5 times higher in nonvaccinated birds than in vaccinated birds.Result was not agreed with Barman et al. (2010) who stated that the risk was 1.5 time higher in nonvaccinated birds.Percentages varriation of most common gross lesions that were found in different organs during postmortem examination showed in Table 3.In this observation, the gross pathological lesions were slight to severe haemorrhages in the proventiculus, haemorrhage in caecal tonsils.These findings support with the observation of Mishra et al. (2000) and Okoye et al. (2000) who reported that typical lesions are proventricular haemorrhage, most commonly seen in the surface near the junction with the ventriculus and in the caecal tonsils and haemorrhages in the intestine, which supports with the finding of others (Jungherr and Hanson, 2004).Kianizadeh et al. (2002) who reported that haemorrhagic lesions associated with necrosis are found in the intestinal wall.Histopathological lesions in the proventiculus were distortion of normal architecture of tissue, globular destruction, sever epithelial layer destruction, haemorrhages and congestion in the mucosa of proventriculus.