Ranaviruses have been associated with amphibian, fish and reptile mortality events worldwide and with amphibian population declines in parts of Europe. Xenopus laevis is a widespread invasive amphibian species in Chile. Recently, Frog virus 3 (FV3), the type species of the Ranavirus genus, was detected in two wild populations of this frog near Santiago in Chile, however, the extent of ranavirus infection in this country remains unknown. To obtain more information about the origin of ranavirus in Chile, its distribution, species affected, and the role of invasive amphibians and freshwater fish in the epidemiology of ranavirus, a surveillance study comprising wild and farmed amphibians and wild fish over a large latitudinal gradient (2,500 km) was carried out in 2015–2017. In total, 1,752 amphibians and 496 fish were tested using a ranavirus-specific qPCR assay, and positive samples were analyzed for virus characterization through whole genome sequencing of viral DNA obtained from infected tissue. Ranavirus was detected at low viral loads in nine of 1,011 X. laevis from four populations in central Chile. No other amphibian or fish species tested were positive for ranavirus, suggesting ranavirus is not threatening native Chilean species yet. Phylogenetic analysis of partial ranavirus sequences showed 100% similarity with FV3. Our results show a restricted range of ranavirus infection in central Chile, coinciding with X. laevis presence, and suggest that FV3 may have entered the country through infected X. laevis, which appears to act as a competent reservoir host, and may contribute to the spread the virus locally as it invades new areas, and globally through the pet trade.

13 Inflammatory bowel disease (IBD) is a disease with recurring 14 gastrointestinal symptoms. Lymphocytes and mast cells are proposed as 15 important components in the immunopathology of IBD in dogs. Mast cells 16 depend on degranulation, a process that compromises mucosal 17 permeability and normal intestinal barrier function, which alters the normal 18 inflammatory process by allowing recruitment of lymphocytes in dogs with 19 IBD. In this study, T and B lymphocyte populations and mast cells were 20 examined in situ in 39 intestinal samples of dogs affected by IBD, by 2 21 immunohistochemistry. Both T lymphocytes and mast cells numbers were 22 significantly higher in the lamina propria of the intestinal wall of dogs with 23 IBD compared with control dogs. Out of the total number of mast cells 24 detected by CD117 expression significantly less cells appear to be 25 granulated according to granule staining with Toluidine Blue, suggesting 26 that an important degranulation process takes place in IBD. Single and 27 double immune staining for tryptase and chymase showed that mast cells 28 can express only one or both enzymes. Tryptase positive cells were 29 significantly higher in number that chymase positive and 30 tryptase/chymase positive cells. T lymphocytes were concentrated mostly 31 at the upper portion of the intestinal villi lamina propria while mast cells 32 were distributed mainly among crypts. These results suggest that 33 populations of T lymphocytes and mast cells play a role in the 34 immunopathology and development of IBD in dogs, also these changes 35 could be helpful as complementary indicators of canine IBD. 36 37 Keywords: dog; inflammatory bowel disease; immunohistochemistry; T 38 lymphocytes; mast cells 39 40 42 disorders characterized by persistent or recurring gastrointestinal 43 symptoms with histologic evidence of inflammatory cell infiltration (1). 3 44 There are different forms of IBD in dogs, depending on the main cell type 45 involved and the affected portion of the intestine where the infiltration 46 takes place, being lymphocytic-plasmacytic enteritis the most common 47 form (2). The etiology of IBD remains unknown. Several studies suggest 48 that these diseases result from inappropriate immune responses to the 49 intestinal microbiome in genetically susceptible individuals (3-6). There 50 are several factors involved including microbiome, environmental factors, 51 genetic predisposition, and changes in the immune response of the 52 individual, which may lead to loss of tolerance to the endogenous flora 53 and the development of chronic inflammation of the gastrointestinal tract 54 (7,8). 55 Different studies (9-12) suggest that a primary defect in the 56 recognition of commensal bacteria or bacterial pathogens in the intestinal 57 lumen, may lead to an increase in the production of IL-23, that induce 58 naïve T cells to differentiate into T-helper (Th) lymphocytes, which release 59 large amounts of proinflammatory cytokines (13,14). Theses cytokines 60 damage the intestinal epitheliu...