caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is now a pandemic threat. This virus is supposed to be spread by human to human transmission. Cellular angiotensin-converting enzyme 2 (ACE2) is the receptor of SARS-CoV-2 which is identical or similar in different species of animals such as pigs, ferrets, cats, orangutans, monkeys, and humans. Moreover, a recent study predicted that dogs might be secondary hosts during the evolution of SARS-CoV-2 from bat to human. Therefore, there is a possibility of spreading SARS-CoV-2 through domestic pets. There are now many reports of SARS-CoV-2 positive cases in dogs, cats, tigers, lion, and minks. Experimental data showed ferrets and cats are highly susceptible to SARS-CoV-2 as infected by virus inoculation and can transmit the virus directly or indirectly by droplets or airborne routes. Based on these natural infection reports and experimental data, whether the pets are responsible for SARS-CoV-2 spread to humans; needs to be deeply investigated. Humans showing clinical symptoms of respiratory infections have been undergoing for the COVID-19 diagnostic test but many infected people and few pets confirmed with SARS-CoV-2 remained asymptomatic. In this review, we summarize the natural cases of SARS-CoV-2 in animals with the latest researches conducted in this field. This review will be helpful to think insights of SARS-CoV-2

No abstract

No abstract

Topology and histology were performed in the lymphoid tissues (thymus, bursa of Fabricius, spleen and cecal tonsils) of the fifteen 28-days-old "Kasilla" broilers by observation of H & E stained sections in the Department of Anatomy and Histology, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh during the period from October to December 2005. In the present study, it was observed that the thymus was enclosed by a thin connective tissue capsule. Numerous fine septa of connective tissue originated from the capsule and divide the organ into incompletely separated lobules. Each lobule organized into a peripheral cortex and a central medulla. The population of the immunocompetent cells (lymphocytes and immunoglobulin containing plasma cells) in the cortex were denser rather than that of medulla of the thymic lobule. The bursa of Fabricius was consisting of long thick mucosal folds (plicae). Numerous follicles filled the lamina propria of each fold and each bursal follicle was composed a peripheral cortex and a central medulla. The population of the immunocompetent cells in the cortex of the bursal follicle were denser rather than that of medulla of the bursal follicle. The spleen was surrounded by a thick splenic capsule and there was a small number of trabeculi. The network of the splenic tissue was consisting of a network of reticular cells and fibers and was arranged into red pulps, which were scatteredly distributed within the white pulps. The white pulp was composed of network of reticular cells and reticular fibers within which the immunocompetent cells were diffusely distributed. It contained sheathed arteries and lymphatic nodules. The red pulp of the spleen was formed from venous sinuses and anastomosing cord of reticular cells, macrophages, lymphocytes and blood cells. Cecal tonsil was composed of four histological layers i.e. tunica mucosa, submucosa, muscularis and serosa. Their lining epithelium was simple columnar epithelium. More diffuse lymphoid tissue and unorganized lymphatic nodules were present both in the mucosa and submucosa of the cecal tonsil of broiler. The length and breadth of the thymic lobules were 629.30 ± 118.95 µm and 376.03 ± 98.92 µm, bursal follicles 468.83 ± 52.26 µm and 240.70 ± 34.19 µm, white pulp of the spleen 112.62 ± 13.25 µm and 89.42 ± 12.20 µm, lymphatic nodules of the cecal tonsil 255.20 ± 20.46 µm and 186.08 ± 24.90 µm respectively. The result of the present study revealed that the immunocompetent cells were arranged scatteredly or densely and as unorganized or organized lymphatic nodules in the lymphoid tissues and the length and breadth of the thymic lobule, bursal follicle, splenic white pulp and lymphatic nodule of cecal tonsils were varied within the lymphoid tissues and even one another.

The polybasic furin cleavage site insertion with four amino acid motifs (PRRA) in spike protein's S1/S2 junction site is important in determining viral infectivity, transmission, and host range. However, there is no review so far explaining the effect of the furin cleavage site of the spike protein on SARS-CoV-2 replication and pathogenesis in the host and immune responses and vaccination. Therefore, here we specifically focused on genomic evolution and properties of the cleavage site of spike protein in the context of SARS-CoV-2 followed by its effect on viral entry, replication, and pathogenesis. We also explored whether the spike protein furin cleavage site affected the host immune responses and SARS-CoV-2 vaccination. This review will help to provide novel insights into the effects of polybasic furin cleavage site on the current COVID-19 pandemic.