Abstract
ABSTRACT This study compared the pathologic effects of velogenic Newcastle disease (ND) virus in broilers and pullets using the normal pathogenic dose of the virus following an earlier report that challenge of the two types of chickens with a low dose of the virus caused mortalities in broilers but none in pullets. One hundred and twenty chickens (10 weeks old) were randomly assigned into four groups (n = 30 each): inoculated intramuscularly with velogenic viscerotropic ND virus (vvNDV) pullets – IP, uninfected pullets – UP, infected broilers – IB and uninfected broilers – UB. Anorexia, depression, ruffled feathers, green diarrhoea, tucking of the head under their wings, droopy wings and prostration were observed on days 2 and 3 post inoculation (PI) in groups IP and IB respectively. Mortality in IP and IB was 100%. Weight loss was significant (P < 0.05) by day 4 PI in both IP and IB when compared with their controls. Percentage weight loss in IP and IB were 20.26% and 38.66%, respectively. Proventricular, intestinal and caecal tonsil haemorrhages were significantly (p < 0.05) more severe in group IB than IP. Histopathology showed more severe necrosis and depletion of the lymphocytes in the bursa of Fabricius, thymus and spleen of group IB than IP. The above observations show that the lesions of vvNDV infection may be more severe in IB than IP.
Highlights
Newcastle disease (ND) is a viral disease caused by Newcaastle disease virus (NDV) which is an avian paramyxovirus belonging to the genus Avulavirus in the family Paramyxoviridae and order Mononegavirales (Lamb et al 2005)
The velogenic pathotype of ND is the most severe form of ND with the velogenic viscerotropic pathotype being the most common and enzootic in Africa, Middle and Far East and some countries of Central and South America (Spradbrow 1988; Echeonwu et al.1993; Liu et al 2003; Solomon et al 2012) It is a disease of severe economic importance due to high mortalities in chickens, loss of egg production due to significant reduction in serum phosphorus levels (Igwe et al 2018), loss of international trade on poultry and poultry products due to embargo by the international community and the expensive stamping out policy used in the control of the disease in those countries where velogenic Newcastle disease is exotic
This paper describes a comparative study of the severity of velogenic viscerotropic ND virus (vvNDV) infection in broilers and pullets
Summary
Newcastle disease (ND) is a viral disease caused by Newcaastle disease virus (NDV) which is an avian paramyxovirus belonging to the genus Avulavirus in the family Paramyxoviridae and order Mononegavirales (Lamb et al 2005). Chickens are the most susceptible (Eze et al 2014; Igwe et al 2014; Okoroafor et al 2018), being the only avian species that show severe gastrointestinal lesions of ND. The velogenic pathotype of ND is the most severe form of ND with the velogenic viscerotropic pathotype being the most common and enzootic in Africa, Middle and Far East and some countries of Central and South America (Spradbrow 1988; Echeonwu et al.1993; Liu et al 2003; Solomon et al 2012) It is a disease of severe economic importance due to high mortalities in chickens, loss of egg production due to significant reduction in serum phosphorus levels (Igwe et al 2018), loss of international trade on poultry and poultry products due to embargo by the international community and the expensive stamping out policy used in the control of the disease in those countries where velogenic Newcastle disease (vND) is exotic. It has been reported that vaccination could protect against the clinical signs but not against the multiplication and shedding of the vvNDV, atrophy and depletion of the lymphocytes in the lymphoid organs ((Miller et al 2007, 2013; Ezema et al 2009, 2016; Cattoli et al 2011; Bwala et al 2012; Okwor et al 2016; Sa e Silva et al 2016; Okoroafor et al 2018)
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