Comparison Of The Susceptibility And Pathology Of Velogenic Newcastle Disease Virus Infection In Broilers And Pullets

ABSTRACT

The greatest human nutritional problem in Nigeria is that of inadequate animal protein

in the diet of a large proportion of the population. The development and sustenance of the

poultry industry in Nigeria appears to be the fastest means of meeting human need for dietary

animal protein supply. However, diseases constitute a major problem to the development of

the poultry industry and Newcastle disease (ND) is the most important of these diseases.

Newcastle disease is caused by a ND virus (NDV) which is a Paramyxovirus. The commonest

strain of NDV in Nigeria is the velogenic, viscerotropic NDV which is the most virulent

among the five pathotypes. Chickens are the most susceptible of all the avian species;

however the relative susceptibility of various types of chicken to velogenic NDV infection has

not been investigated. The objective of this study is to compare the susceptibility, clinical

signs, gross and histologic lesions, haematological and serum protein profile changes,

distribution and persistence of lesions of velogenic Newcastle disease virus KUDU-113 in

broilers and pullets experimentally infected at 10 weeks of age. Thirty broilers and 30 pullets

were inoculated intramuscularly with 0.1ml of a velogenic Newcastle disease virus (NDV)

strain (KUDU-113) with a median EID50 of 105.46 per ml. Clinical signs were first observed in

the pullet on day 2 post inoculation (PI) which were mainly depression, ruffled feathers,

whitish diarrhoea, prostration, tucking of the head under their wings, paralysis of legs and

wings and withdrawal from feed. In broilers, signs were first observed on day 3 PI, which

were withdrawal from feed, depression, jerking of head, neck and head tremor, generalized

spasm and recumbence, ruffled feathers and greenish diarrhoea. Weight loss was highly

significant (P 0.05) difference was observed in the pullets. There

were no significant (P > 0.05) differences in total white blood count, heterophil, and

lymphocytes counts in both infected broilers and pullets. There were no significant (P > 0.05)

differences between the infected and control in the total serum protein values on day 4 PI in

broilers. However, the total serum protein value of the infected pullets was significantly (P 0.05) on day 4 PI. The above observation

shows that differences in weight loss and lesion severity were higher in broilers than in

pullets.