Newcastle disease (ND) is endemic in Angola. Several outbreaks of ND occurred in small backyard flocks and village chickens with high mortality in the southern provinces of the country, Cunene, Namibe and Huíla, in 2016 and 2018. In those years, 15 virulent ND virus (NDV) strains were isolated and grouped within subgenotype 2 of genotype VII (subgenotype VII.2). We now present a study on the thermostability of the isolates, aiming at the selection of the most thermostable strains that, after being genetically modified to reduce their virulence, can be adapted to the production of vaccines less dependent on cold chain and more adequate to protect native chickens against ND. Heat-inactivation kinetics of haemagglutinin (Ha) activity and infectivity (I) of the isolates were determined by incubating aliquots of virus at 56 °C for different time intervals. The two isolates from Namibe province showed a decrease in infectivity of 2 log10 in ≤ 10 min, therefore belonging to the I-phenotype, but while the NB1 isolate from 2016 maintained the Ha activity up to 30 min and was classified as thermostable virus (I−Ha+), the Ha activity of the 2018 NB2 isolate decreased by 2 log2 in 30 min, being classified as a thermolabile virus (I−Ha−). Of the 13 NDV isolates from Huíla province, 10 isolates were classified as thermostable, eight with phenotype I+Ha+ and 2 with phenotype I−Ha+. The other three isolates from this province were classified as thermolabile viruses (I−Ha−). Contribution: This study will contribute to the control and/or eradication of Newcastle disease virus in Angola. The thermostable viral strains isolated from chickens in the country can be genetically manipulated by reverse genetic technology in order to reduce their virulence and use them as a vaccine in the remote areas of Angola.

The lack of effective therapeutic modalities for mammary cancer is attributed to side effects and therapy resistance, necessitating the exploration of alternative treatment options. Newcastle Disease Virus (NDV) exhibits oncolytic activity, making it a promising candidate for cancer therapy. This study aims to assess the effectiveness of the virulent NDV Tabanan-1/ARP/2017 on the growth of mammary carcinoma. The study involved 15 white female Sprague-Dawley rats induced with mammary carcinoma. After the tumors had developed, the rats were divided into two treatment groups, i.e., treatment 0 (P0) and treatment 1 (P1), which received 500 μL of phosphate-buffered saline and 128 HAU/500 μL of NDV Tabanan-1/ARP/2017, respectively. The rats were euthanized on day 15 post-virotherapy. Rats were necropsied, the tumor was excised to measure its weight, percentage of tumor inhibition, and subsequently routinely processed for histopathological preparations. The tumor weights in each treatment group were 3.70±0.72 and 2.34±0.64 grams, respectively, with a tumor inhibition percentage of 36.62%. The angiogenesis, hemorrhage, and mitotic activity of P1 were lower than those of P0, while inflammatory cell infiltration and areas of necrosis appeared more prominent in the group treated with the NDV. In conclusion, the NDV Tabanan-1/ARP/2017 shows potential as a virotherapy agent for rat mammary carcinoma models.