Salmonelose em bezerros pelo sorovar Dublin no estado do Paraná, Brasil - aspectos clínico-patológicos / Salmonellosis in calves by serovar Dublin in Paraná State, Brazil - clinicopathological aspects

Background: Calf diarrhea remains one of the main diseases affecting the cattle industry. Persistence of this significant problem is associated with the complexity of factors that may be involved (infectious, environmental). An accurate diagnosis is essential for confirming the cause and helping clinicians and cattle producers to apply appropriate strategies in a timely manner. This report describes the histological changes according to the degree of salmonellosis severity, which is a contagious infectious disease caused by Salmonella enterica subsp. enterica, a Gram-negative bacterium, in two beef calves in northern Paraná State, southern Brazil. Cases: Two 90-day-old crossbred Angus and Nellore calves from a beef farm in northern Paraná State were referred to a Veterinary Hospital. Animal 1- developed acute clinical signs (enteritis, ataxia, and muscle rigidity) and died the day after the signs began. Gross findings included heavy and non-collapsed lungs, pulmonary oedema, hepatomegaly, enteritis, and severe diffuse typhlitis. Microscopic analysis revealed severe diffuse necrotic enteritis, typhlitis, severe diffuse interstitial pneumonia, moderate centrilobular hepatic necrosis, mild multifocal nephritis, and severe spleen and lymph node necrosis. Paratyphoid nodules were evidenced on the liver, spleen, and mesenteric lymph nodes. Animal 2- presented apathy, green fibrinous diarrhea, and died three days after the onset of clinical signs. The macroscopic examination showed moderate diffuse enteritis and hepatosplenomegaly. At the microscopic examination, many paratyphoid nodules were observed on the liver, spleen, kidneys, and Peyer's patches, which were associated with intralesional and intravascular bacilli. Additional findings included severe diffuse fibrinous necrotic enteritis with intralesional bacilli, diffuse interstitial pneumonia, multifocal splenic necrosis, lymphoid depletion, and moderate multifocal to coalescent lymphocytic nephritis. Histological Gram staining was performed on selected samples, revealing intralesional Gram-negative bacilli in the liver and intestine. Thus, liver and intestine fragments were used for the microbiological examination. Microbiological culture, isolation and biochemical tests identified the genus Salmonella spp. Then, the colonies were subjected to serological tests for serovar identification, according to ISO/TR 6579-3, which determined the serovar Dublin. After identifying the disease etiological agent, the outbreak was controlled by appropriate antibiotic therapy combined with the correction of sanitary measures. Discussion: Enteritis is a frequent disease in calves, posing a diagnostic challenge in identifying the etiological agent. In the present case, the histological, microbiological, and serological results confirmed a disseminated Salmonella spp. infection. The microscopic findings, such as interstitial pneumonia, fibrinous necrotic enteritis markedly in ileum and paratyphoid nodules in various organs, are the most common aspects of the disease. However, fibrinous cholecystitis, which is considered pathognomonic for salmonellosis, was not observed in this study. Therefore, the absence of such a lesion should not exclude the disease in sick animals. A microscopic injury score was used to determine lesion severity by assigning values from 1 to 4, wherein: 1 = no apparent lesions, 2 = mild lesions, 3 = moderate lesions, and 4 = severe lesions. Both calves were scored as 4. Multiple predisposing factors for the condition were identified in this farm such as different age animals in the same paddock and no specific paddock for sick animals, given that the infectious agent remains in feces, saliva, and nasal discharge. The serovar Dublin induces several clinical signs such as septicemic, respiratory, and enteric manifestations, making a clinical diagnosis a challenge

Enteric pathology and Salmonella-induced cell death in healthy and SIV-infected rhesus macaques.

The goal of this study was to morphologically characterize a ligated ileal loop model of Salmonella enterica serotype Typhimurium infection in rhesus macaques (Macaca mulatta) and to verify the occurrence of Salmonella-induced cell death in vivo. Eight adult healthy male rhesus macaques were used for ligated ileal loop surgery. Four macaques had been intravenously inoculated with simian immunodeficiency virus (SIV) mac251. Ileal ligated loops were inoculated with wild-type (WT) S. Typhimurium strain IR715 (ATCC14028 nal (r)), an isogenic noninvasive mutant strain (ATCC14028 nal (r) ΔsipAΔsopABDE2), or sterile Luria Bertani broth. Loops were surgically removed at 2, 5, and 8 hours post-inoculation (hpi). Intestinal samples were processed for histopathology, immunohistochemistry for detecting Salmonella, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), and transmission electron microscopy. Combined histopathology scores were similar between SIV-infected and control macaques. As expected, the invasion-deficient mutant was less pathogenic than WT S. Typhimurium. Neutrophil infiltrate in the intestinal mucosa correlated with bacterial loads (r = 0.7148; P < .0001) and fluid accumulation (r = 0.6019; P < .0001) in the lumen of the intestinal loops. Immunolabeled WT S. Typhimurium was observed in the epithelium and lamina propria at the tip of the villi at 2 hpi, progressing toward deeper lamina propria at 5-8 hpi. Most TUNEL-positive cells localized to the lamina propria, and some had morphological features of macrophages. Ultrastructurally, bacteria were observed intracellularly in the lamina propria as well as within apoptotic bodies. This study provides morphological evidence of Salmonella-induced cell death in vivo in a relevant nonhuman primate model.

Prevalence of Salmonella spp. antibodies to Toxoplasma gondii, and Newcastle disease virus in feral pigeons (Columba livia) in the city of Jaboticabal, Brazil.

The rock pigeon (Columba livia) may serve as a reservoir for several pathogenic agents that can be transmitted to poultry, wildlife, domesticated pets, and/or humans via excreta, secretions, or dust from feathers. In addition, ingestion of infected pigeons by wild and domestic animals can also transmit these pathogenic agents. The health status of 126 free-living pigeons in an urban area was evaluated by microbiologic culture for Salmonella and serologic testing for the presence of antibodies for Toxoplasma gondii and for Newcastle disease virus (NDV) from 120 and 109 pigeons, respectively. After drawing blood, the birds were euthanized, and fragments of the liver, spleen, lungs, and gonads, and feces were cultured for Salmonella spp. Salmonella spp. was isolated from 10 birds (7.94%), of which 8 were Salmonella typhimurium, one was Salmonella enterica subsp. enterica serotype 4,12 and one was Salmonella enterica subsp. enterica serotype 4,12,i. Six of 109 pigeons (5.50%) were positive for NDV antibodies when using the hemagglutination inhibition test. Toxoplasma gondii antibodies were detected by immunofluorescence in one of 120 sera tested (0.83%). The results indicate that feral rock pigeons were exposed to NDV and T. gondii, although the exposure was low. In addition, these birds had Salmonella spp. and could disseminate this pathogen in the environment.