Matias A. Dorsch

Salmonella spp. is a major zoonotic pathogen. Although reptiles are mostly considered subclinical carriers, clinical disease may develop following immunosuppression. Clinical salmonellosis in reptiles has been extensively reported; however, the condition has been rarely described in bearded dragons (Pogona vitticeps). We retrospectively analyzed six cases of salmonellosis in bearded dragons and characterized the pathological, immunohistochemical, and bacteriological findings. Clinical signs and gross findings were mostly non-specific. Histological findings mainly consisted of fibrinonecrotizing enterocolitis (83.3%); necrotizing or granulomatous hepatitis (66.7%); pneumonia including bronchopneumonia or interstitial pneumonia in one case each (33.3%); tubulointerstitial nephritis with tubular necrosis (16.7%); and coelomitis (16.7%). Salmonella enterica subsp. houtenae was cultured in three cases (33.3%), whereas S. enterica subsp. enterica serovar Rissen, S. enterica subsp. enterica serovar Cotham, and S. enterica subsp. diarizonae were cultured in one case each. Intralesional bacteria were detected via immunohistochemistry in kidneys and colon in two cases (33.3%). The predominance of lesions in the intestines and liver likely reflects initial intestinal colonization followed by hematogenous dissemination to the liver. Hepatic lesions are thought to represent different stages along a continuum, progressing from acute necrosis to discrete granuloma formation. Renal and respiratory involvement was infrequent, as reported in other reptile species. Some of the isolated Salmonella subspecies (S. diarizonae and S. houtenae) are well-recognized causes of clinical disease in other reptile species but not previously identified in bearded dragons. This study provides a comprehensive pathological, immunohistochemical, and bacteriological characterization of salmonellosis in bearded dragons, thus raising awareness and assisting in the identification of this condition.

Toxoplasma gondii is a globally prevalent zoonotic parasite with multiple life stages and transmission routes, including ingestion and transplacental transmission. It is a major cause of abortion in sheep, goats and pigs, among other production animals, worldwide. While Type II strains are common in livestock in North America and Europe, non-archetypal, non-clonal genotypes are highly prevalent in South America. This study aimed to determine the molecular epidemiology of T. gondii strains causing sheep abortion in Uruguay. Phylogenomic analyses confirmed significant divergence among typed strains and revealed similarities with genotypes previously detected in the human population. Two novel strains, were isolated and characterized, uncovering the connection between their genetic makeup and phenotypes. Differences in virulence could be correlated to differences in gene copy number of the pseudo kinase ROP5 – further highlighting this virulence factor as relevant in wild strains. Whole-genome sequencing further confirmed the divergence among Uruguayan isolates, uncovering at least three distinct evolutionary origins. Overall, our findings highlight the circulation of virulent non-clonal lineages with links to human infections and underscore the importance of furthering genomic surveillance in South America to better understand Toxoplasma ’s transmission dynamics, pathogenic potential, and zoonotic risk.

In April–June 2017, a cluster of 4 third-trimester abortions caused by Coxiella burnetii was diagnosed on a dairy farm with 356 Holstein cows in Uruguay. We investigated 1) the seroprevalence of C. burnetii in cows delivering normal calves in this herd, 2) whether non-aborting cows gave birth to seropositive and/or PCR-positive newborn calves in the year of the abortion cluster, and 3) whether seronegative newborn calves seroconverted after ingesting colostrum replacer. In March–September 2017, serum samples were collected from 133 calving cows and their calves immediately after birth and before colostrum ingestion. All 266 sera were analyzed for anti– C. burnetii IgG by ELISA. Additionally, 179 blood samples from some of these animals (82 cows, 97 calves) were PCR-tested for C. burnetii DNA. Thirty of the 133 (22.5%) cows delivering normal calves were seropositive at parturition; 4 of 82 (4.9%) were PCR-positive. All calves tested at birth by ELISA and PCR were negative. Our results suggest that congenital infection is not an important route of C. burnetii transmission to live-born calves in this herd. We observed that 76 of 80 (95%) seronegative newborn calves in 2021 became seropositive for anti– C. burnetii IgG at 24-h-old after drinking an imported commercial colostrum replacer, which could confound seroepidemiologic surveys in herds using colostrum replacers.

Canine leproid granuloma (CLG) is a chronic form of dermatitis that has been associated with nontuberculous mycobacterial infections in Africa, Oceania, the Americas, and Europe. We report here a case of CLG associated with a member of the Mycobacterium tuberculosis complex (MTBC), which could be of public health concern. An 8-y-old pet dog developed 0.5–1-cm diameter, raised, firm, nonpruritic, alopecic, painless skin nodules on the external aspects of both pinnae. Histologic examination revealed severe pyogranulomatous dermatitis with intracellular Ziehl-Neelsen–positive bacilli that were immunoreactive by immunohistochemistry using a polyclonal primary antibody that recognizes tuberculous and nontuberculous Mycobacterium species. DNA extracted from formalin-fixed, paraffin-embedded skin sections was tested by a Mycobacterium genus–specific nested PCR assay targeting the 16S rRNA gene. BLAST sequence analysis of 214-bp and 178-bp amplicons showed 99.5% identity with members of the MTBC; however, the agent could not be identified at the species level. Although CLG has been associated traditionally with nontuberculous mycobacterial infections, the role of Mycobacterium spp. within the MTBC as a cause of this condition, and the role of dogs with CLG as possible sources of MTBC to other animals and humans, should not be disregarded given its zoonotic potential.

Blackleg is an infectious disease caused by Clostridium chauvoei. Cardiac blackleg has been reported in ruminants as an uncommon presentation of the disease; its pathogenesis is not understood completely. We include here a literature review of cardiac blackleg and a description of 2 cases in 12–15-mo-old feedlot steers in Argentina. Fourteen of 1,190 steers died suddenly over a period of 10 d. Postmortem examinations were performed on 5 of these animals. Grossly, severe, diffuse, fibrinous pericarditis and pleuritis, multifocal necrohemorrhagic myocarditis, diffuse pulmonary congestion, mild splenomegaly, and moderate congestion of meningeal vessels were observed. No significant gross lesions were observed in the skeletal muscles of any animal. Histology was performed on 2 of the steers. The main microscopic features were necrotizing myocarditis with myriad intralesional gram-positive rods with subterminal spores plus fibrinosuppurative pericarditis and pleuritis. C. chauvoei was detected by immunohistochemistry and PCR in the myocardium of both animals. These findings confirm a diagnosis of cardiac blackleg in these 2 steers and presumptively in the other affected animals.

Neospora caninum is a major reproductive disease in cattle worldwide. In the Argentinian Humid Pampa, the seroprevalence, incidence of abortions, and economic losses due to neosporosis are considerably higher in dairy than in beef cattle. Despite this, we recently demonstrated that N. caninum subpopulations are indistinctly distributed in both dairy and beef production systems. The association between genotypic characteristics defined by microsatellite analysis and the virulence of the different strains—particularly with regard to the severity and extension of histological lesions—is largely unknown. Herein, we used a morphometric approach to analyze encephalic lesions in 62 bovine fetuses spontaneously infected by N. caninum. Morphometric parameters (average size of focal lesions, number of foci/cm² and the percentage of the section affected by lesions) were compared according to the N. caninum subpopulations found in our previous microsatellite genotyping analysis, animal biotype (beef versus dairy), and fetal age (second stage of gestation versus third stage). The average size of the lesions differed significantly among fetuses with different gestational ages; however, no significant differences among animal biotypes or genotypic patterns were found. Further research into the genetic, molecular, and husbandry factors that could account for this greater impact in Argentinian dairy herds is needed.

Neospora caninum is an apicomplexan protozoan and a major cause of abortion in cattle worldwide. In the Argentinian Humid Pampa, bovine neosporosis causes severe economic losses. Despite this, information on the genetic structure of N. caninum in this region is limited. Therefore, this study aimed to genetically characterize N. caninum isolates associated with bovine abortion in the Humid Pampa region. For this purpose, spontaneous bovine fetal tissues submitted for diagnosis to the Veterinary Diagnostic Service at INTA Balcarce during 2008–2019 were assessed by PCR, indirect fluorescent antibody test (IFAT), and histologic analysis. PCR-positive samples were tested by multilocus microsatellite genotyping (MLGs) using 9 microsatellite markers. Thirty-one different genotypes were identified from 32 samples with at least seven markers. Argentinian MLGs were grouped into two clonal clusters when analyzed using eBURST network and principal coordinate analysis. No segregation based on the year of collection, animal biotype, or geographic origin was observed. In addition, the presence of linkage disequilibrium supported the clonal propagation of Argentinian MLGs. One Argentinian subpopulation was associated with isolates from Spain, Uruguay, Brazil, and Mexico, and the other one was linked to isolates from Scotland, Spain, and Germany. These findings reveal the presence of two clonal subpopulations of N. caninum in the Humid Pampa.

Detection of bovine viral diarrhea virus (BVDV) in aborted fetus samples is often difficult due to tissue autolysis and inappropriate sampling. Studies assessing different methods for BVDV identification in fetal specimens are scarce. The present study evaluated the agreement between different diagnostic techniques to detect BVDV infections in specimens from a large number of bovine aborted fetuses and neonatal deaths over a period of 22 years. Additionally, genetic, serological, and pathological analyses were conducted in order to characterize BVDV strains of fetal origin. Samples from 95 selected cases from 1997 to 2018 were analyzed by antigen-capture ELISA (AgELISA), nested RT-PCR (RT-nPCR), and real-time RT-PCR (RT-qPCR). In addition, amplification and sequencing of the 5′UTR region were performed for phylogenetic purposes. Virus neutralization tests against the BVDV-1a, BVDV-1b, and BVDV-2b subtypes were conducted on 60 fetal fluids of the selected cases. Furthermore, the frequency and severity of histopathological lesions were evaluated in BVDV-positive cases. This study demonstrated that RT-nPCR and RT-qPCR were more suitable than AgELISA for BVDV detection in fetal specimens. However, the agreement between the two RT-PCR methods was moderate. The BVDV-1b subtype was more frequently detected than the BVDV-1a and BVDV-2b subtypes. Neutralizing antibodies to any of the three subtypes evaluated were present in 94% of the fetal fluids. Microscopically, half of the BVDV-positive cases showed a mild non-suppurative inflammatory response. These results emphasize the need to consider different methods for a diagnostic approach of BVDV associated to reproductive losses.