International Journal of Molecular Veterinary Research, 2024, Vol.14, No.6, 235-243 http://animalscipublisher.com/index.php/ijmvr 236 morbidity and mortality rates (Abdisa and Tagesu, 2017; Sahoo et al., 2022). The disease is caused by the Newcastle disease virus (NDV), which belongs to the genus Avulavirus, sub-family Paramyxovirinae, and family Paramyxoviridae. 2.1 Etiology and pathogenesis of ndv (Newcastle disease virus) NDV is classified into different pathotypes based on its virulence: asymptomatic enteric, lentogenic, mesogenic, viscerotropic velogenic, and neurotropic velogenic strains (Abdisa and Tagesu, 2017). The virus primarily spreads through respiratory aerosols, fecal contamination, and contact with infected birds or contaminated materials. Pathogenesis studies have shown that NDV can infect various tissues, including the respiratory and gastrointestinal tracts, and can cause systemic infections leading to severe clinical signs and high mortality. The virus's ability to replicate in multiple organs, such as the trachea, liver, spleen, and brain, contributes to its pathogenicity (Hussein et al., 2019; Akanbi et al., 2020). 2.2 Clinical signs and diagnosis of ND in chickens Clinical signs of ND in chickens vary depending on the virus strain, age, and species of the bird, as well as the presence of concurrent infections and immunity levels. Common symptoms include respiratory distress (gasping, coughing, sneezing), neurological signs (tremors, paralysis, twisted necks), and gastrointestinal issues (greenish diarrhea). Diagnosis is typically based on clinical signs, history, and laboratory confirmation through virus isolation, serological tests, and molecular techniques such as RT-PCR (Abdisa and Tagesu, 2017; Nyoman et al., 2024). 2.3 Epidemiology and global distribution of ND ND is endemic in many parts of the world, including Asia, Africa, and some regions of the Americas, while countries like the United States and Canada are free from virulent strains in poultry (Abdisa and Tagesu, 2017). The disease's prevalence varies significantly across different regions and is influenced by factors such as bird species, management practices, and environmental conditions (Zegeye et al., 2021; Sahoo et al., 2022). In Ethiopia, for example, the seroprevalence of ND in chickens was estimated to be around 21.47%, highlighting the need for effective control measures4. Similarly, in Bangladesh, outbreaks of ND caused by genotype VII.(Hussein et al., 2019) have been reported, indicating the virus's widespread distribution and the challenges in controlling its spread (Figure 1) (Nooruzzaman et al., 2022). Newcastle disease remains a significant threat to poultry health globally, with its complex etiology, diverse clinical manifestations, and widespread distribution necessitating comprehensive control strategies, including vaccination and biosecurity measures. Figure 1 Gross pathological changes in chickens experimentally inoculated with LT67 isolates of NDV (Adopted from Nooruzzaman et al., 2022) Image caption: (a) Hemorrhages in the trachea, (b) congestion in the lungs, (c) hemorrhages in the proven- triculus, (d) hemorrhages in the intestines (button-like ulcers), (e) C hemorrhages in the cecal tonsils, (f) congestion in the liver, (g) severe congestion in the kidneys, (h) congestion in the brain, (i) hemor- rhages in the Harderian glands, (j) hemorrhages and atrophy in the thymus, (k) congestion in the spleen, and (I) hemorrhages and slight atrophy in the bursa of Fabricius (Adopted from Nooruzzaman et al., 2022)
RkJQdWJsaXNoZXIy MjQ4ODYzNA==