Clinical and genomic features of Listeria monocytogenes-associated mesenteric lymphadenitis in a cat.

BACKGROUND: Listeriosis is a severe foodborne infection caused by Listeria monocytogenes, an important foodborne pathogen of animals and humans. Listeriosis is a rare disease in cats. OBJECTIVE: To describe the clinical, diagnostic imaging, histological, and microbiological features of L. monocytogenes-associated mesenteric lymphadenitis in a cat. ANIMALS: Listeria monocytogenes-associated mesenteric lymphadenitis was confirmed in a cat by histology and microbiology. RESULTS: Two distinct isolates of L. monocytogenes were cultured from the affected mesenteric lymph node and whole genome sequencing was performed. CONCLUSION AND CLINICAL IMPORTANCE: This report should alert veterinary clinicians and microbiologists to the syndrome, which may have implications for health and food safety in animals and humans.

Mesenteric lymphangitis and sepsis due to RTX toxin-producing Actinobacillus spp in 2 foals with hypothyroidism-dysmaturity syndrome.

Actinobacillus suis-like organisms (ASLOs) have been isolated from the genital, respiratory, and digestive tracts of healthy adult horses, horses with respiratory disease, and septic foals. Two foals with congenital hypothyroidism-dysmaturity syndrome from separate farms developed ASLO infection. At necropsy, both had contracted carpal flexor tendons, thyroid hyperplasia, and thrombotic and necrotizing mesenteric lymphangitis and lymphadenitis; one foal also had mandibular prognathism. Numerous ASLOs were isolated from tissues from both foals, including intestine. Biochemical testing and mass spectrometric analysis of the two Actinobacillus isolates did not allow unequivocal identification. Comparative genetic analysis was done on these and similar isolates, including phylogeny based on 16S rRNA, rpoB and recN genes, as well as RTX (repeat in toxin) toxin typing of apxIA-apxIVA and aqxA genes. One isolate was identified as Actinobacillus suis sensu stricto, based on the presence of apxIA and apxIIA but not aqxA, whereas the other isolate had aqxA but neither apxIA nor apxIIA, consistent with A equuli ssp haemolyticus. Based on genotypic analysis of the isolates included for comparison, 3 of 3 equine ASLOs and 2 of 5 A equuli isolates were reclassified as A equuli subsp haemolyticus, emphasizing the importance of toxin genotyping in accurate classification of actinobacilli.

Histopathology of grossly normal mesenteric lymph nodes of New Zealand farmed red deer (Cervus elaphus) including identification of lipopigment.

This article describes the histopathology of grossly normal mesenteric lymph nodes (MLNs) of New Zealand farmed red deer (Cervus elaphus). Eighty MLNs were sourced from 10 deer from 5 North Island herds and 5 South Island herds classified as low risk and high risk of Mycobacterium avium subspecies paratuberculosis (MAP) infection, respectively. Fixed sections were stained with hematoxylin and eosin; Ziehl-Neelsen; and, selectively, periodic acid-Schiff, Perl's, and Sudan black. Positive Ziehl-Neelsen stain, follicular hyperplasia, capsular eosinophil infiltration, focal granulomas, foci of macrophages containing lipopigment, parasitic granulomas, and calcified foci are described and severity graded where appropriate. Animal age, sex, and herd of origin are variably associated with the presence of one or more features. Trabecular fibrosis and dilated edema-filled sinusoids are described. These observations allow differentiation between likely nonpathologic histologic features in deer MLNs and features possibly attributable to infection with a pathogen such as MAP.

Mycobacterium branderi Infection in a Horse with Granulomatous Mesenteric Lymphadenitis.

Although relatively uncommon in horses, infections caused by Mycobacterium spp. may affect the gastrointestinal tract. Mycobacterium branderi is a non-tuberculous Mycobacterium (NTM) that causes respiratory infections in man. Non-tuberculous mycobacteria may also affect horses; however, infection by M. branderi has not yet been reported in this species. This report describes the clinical, pathological, microbiological and molecular findings of M. branderi infection in a horse, causing granulomatous mesenteric lymphadenitis. A 17-year-old Thoroughbred stallion had a 3-month history of chronic diarrhoea, cachexia and ventral and cervical oedema. Necropsy examination revealed severe mesenteric lymphadenomegaly, together with mesenteric lymphangiectasia and diffuse small intestinal mucosal thickening. Microscopically, the mesenteric lymph node had diffuse granulomatous inflammatory infiltration, replacing most of the nodal parenchyma, with multiple acid-fast bacilli within the cytoplasm of macrophages. There was also diffuse lymphangiectasia. Fresh samples of mesenteric lymph nodes yielded no bacterial growth; however, nested polymerase chain reaction products obtained from the mesenteric lymph node samples were consistent with M. branderi. This infection should be included as a differential diagnosis in cases of chronic diarrhoea in horses, especially when granulomatous enteritis and lymphadenitis are also observed.

Pyogranulomatous enteritis and mesenteric lymphadenitis in an adult llama caused by Rhodococcus equi carrying virulence-associated protein A gene.

We report herein Rhodococcus equi infection in an 11-y-old, male llama with a history of diarrhea and endoparasitism. Postmortem examination revealed granulomatous and ulcerative enteritis, pyogranulomatous mesenteric lymphadenitis, fibrinosuppurative peritonitis, and granulomatous hepatitis. Intralesional macrophages were laden with gram-positive cocci. Bacteriology identified R. equi, and cultures tested positive for R. equi choE and vapA genes by PCR. This case expands the reported spectrum of lesions associated with R. equi infections in llamas from pyogranulomatous bronchopneumonia and peripheral lymphadenitis to pyogranulomatous mesenteric lymphadenitis and enteritis. We also link a R. equi that is carrying the virulent-associated protein gene VapA to clinical disease in New World camelids.

Listerial mesenteric lymphadenitis in 3 cats.

BACKGROUND: Listeriosis is a rare disease in cats with naturally occurring cases usually being identified in individual animals. Listerial mesenteric lymphadenitis has not been described previously in cats. OBJECTIVES: To describe the clinical and histological features of listerial mesenteric lymphadenitis in cats as well as treatment outcome. ANIMALS: Listerial mesenteric lymphadenitis was confirmed in 3 cats by histology, immunohistochemistry, and bacterial culture. RESULTS: The affected cats were young to middle aged and were examined for various clinical signs. On both palpation and abdominal ultrasound examination, all cats had marked mesenteric lymphadenomegaly. Survival was prolonged in all 3 cases. Two of the 3 cats were fed a raw meat-based diet before they developed clinical illness. CONCLUSIONS AND CLINICAL IMPORTANCE: Lymphadenitis caused by listeriosis has a protracted time course and should be a differential diagnosis for abdominal lymphadenopathy in young to middle-aged cats. Feeding of a raw meat-based diet may be a contributing factor for development of listeriosis in cats.

Intestinal and pulmonary mycotic lymphadenitis in cattle.

Among 4877 slaughtered cattle with tuberculosis-like lesions in lymph nodes, 94 cases (1.9 per cent) revealed fungal hyphae on histopathological examination. The survey period was 12 years and most of the affected animals (greater than 77 per cent) were beef cattle. Affected nodes were mesenteric in 84 cases (89.4 per cent), mediastinal and/or bronchial in seven cases (7.4 per cent), and in three cases (3.2 per cent), both mesenteric and mediastinal nodes were affected. The incidence of mycotic lymphadenitis was unrelated to year of study or season. Eighty-two of the cases were re-examined histologically and immunohistochemically. All lesions were granulomatous in nature and, in 26 cases, eosinophilic asteroid bodies (rosette formation) around hyphae were found. In 75 cases, immunofluorescence staining identified the agent as a zygomycete, probably Absidia corymbifera and, in one case, there was a concurrent infection with a Candida species. In seven cases that did not react with the antibodies employed, a diagnosis of zygomycosis was suggested on the basis of hyphal morphology. Hyphae of Aspergillus spp. were not found in any of the lesions. A concurrent fungal and mycobacterial infection (M. avium) was diagnosed in one case. Thus, zygomycetes are the main cause of macroscopically apparent mycotic lymphadenitis, a sporadic disease most probably caused by feeding with mouldy food stuffs.

Paraintestinal mesenteric abscess and chronic peritonitis in a bull.

A 2-year-old bull was examined because of intermittent anorexia, signs of mild colic, and weight loss of 3 weeks' duration. A tympanitic resonance (ping) could be heard during simultaneous auscultation and percussion of the right paralumbar fossa, and a mass could be felt in the right dorsal quadrant of the abdominal cavity during palpation per rectum. Right flank laparotomy was performed, and intraoperative ultrasonography and ultrasound-guided fine-needle aspiration were used to determine that the mass was an abscess. However, the abscess could not be removed or drained into the colon because of extensive adhesions to other organs. Because the owner refused to pursue continued medical treatment, the bull was euthanatized. At necropsy, the abscess was found to be connected to a caudal mesenteric lymph node through a fistula. Histologic evaluation of the lymph node revealed hyperplastic lymphadenitis, and an alpha-hemolytic streptococcus was recovered from the abscess fluid. The most likely possibility for the findings in this bull were that the lymphadenitis was of hematogenous origin and that the abscess developed as a direct extension of the infectious process, similar to development of mesenteric abscesses in horses with chronic streptococcal infection (i.e., strangles).

Prevalence of Mycobacterium avium subsp. paratuberculosis in farmed red deer (Cervus elaphus) with grossly normal mesenteric lymph nodes.

AIM: To estimate the prevalence of Mycobacterium avium subsp. paratuberculosis (Map) in farmed deer with no gross post-mortem evidence of Map infection slaughtered in New Zealand, and to assess predictors of infection. METHODS: Mesenteric lymph node (MLN) samples (n = 251) were collected from 60 lines of deer presented at two slaughterhouses in the North and two in the South Island of New Zealand between October 2008 and January 2009 and cultured for Map. Estimates of individual animal prevalence for each island were adjusted to account for the clustering of individual observations within herds. The national herd prevalence estimate was calculated as a weighted mean, with weights being the proportion of herds from which deer were slaughtered at North and South Island slaughterhouses among all herds slaughtering deer throughout New Zealand. Age, gender, and the presence of other carcasses with enlarged and/or granulomatous MLN in the same line (line status) were assessed as predictors of infection using multivariable logistic regression. RESULTS: A national cluster-adjusted individual animal prevalence of 45 (95% CI = 30-60)% was estimated, with North and South Island prevalences of 29 (95% CI = 16-45)% and 51 (95% CI = 36-66)%, respectively. Line status was a strong predictor of infection in young deer (OR 7.1, 95% CI = 2.4-21.5), but not in older deer. Herd-level prevalence was 44 (95% CI = 24-64)% in the North Island and 67 (95% CI = 49-85)% in the South Island. Weighted adjustment resulted in a national herd-level prevalence estimate of 59 (95% CI = 41-78)%. CONCLUSIONS: This study has provided a national baseline prevalence estimate for Map infection at the individual and herd-level, showing a contrast between the North and South Islands. More research to investigate the factors contributing to the difference in infection prevalence seen between the islands may help to identify suitable control measures for Map in deer herds.

Sensitivity, specificity and level of agreement of meat inspector detection of abnormal lymph nodes of farmed deer (Cervus elaphus) in New Zealand.

AIMS: To assess the sensitivity (Se), specificity (Sp) and level of agreement in the detection of abnormal deer mesenteric lymph nodes (MLN) by official assessors (meat inspectors) for the purpose of slaughter premise surveillance for Johne's disease in New Zealand farmed deer. METHODS: To determine Se and Sp, four meat inspectors in two commercial deer slaughter premises (DSP) each examined between 153 and 925 MLN under normal visual examination, palpation and/or incision inspection procedures. Abnormal MLN were independently defined as those with a circumference measurement of  ≥ 55 mm and/or grossly visible pathological changes such as caseation, necrosis and/or mineralisation, while those with a circumference of <55 mm and without gross lesions were defined as normal. The inspectors' diagnosis of normal or abnormal was retrieved from the national DSP-based surveillance database for Johne's disease in deer. To determine between-inspector level of agreement, 54 meat inspectors visually examined two photographic images each of 19 normal and 10 abnormal MLN, and recorded their diagnosis. Between-inspector agreement was calculated based on a modification of Cohen's kappa statistic for multiple raters. The influence of covariates such as inspector age and experience on the between-inspector level of agreement were assessed using the Breslow-Day statistic and test for equal kappa coefficients. RESULTS: The weighted average Se and Sp of inspector detection of abnormal MLN was 13.3 (minimum 4.8, maximum 41.2)% and 99.9 (minimum 99.5, maximum 100.0)%, respectively. The level of between-inspector agreement in the diagnosis of abnormal and normal MLN was fair (κ = 0.32). Employment location, inspector age, experience inspecting deer or other species, and the number of shifts inspecting deer within the previous four weeks had no influence on between-inspector agreement (p > 0.10). CONCLUSIONS: Inspectors diagnosed abnormal deer MLN with a high specificity, but low sensitivity. These data supported that visual assessment of MLN characteristics was suitable for national surveillance for paratuberculosis, while highlighting the need for further emphasis on training of inspectors in abnormal lymph node detection.

Mesenteric lymphadenitis of swine caused by Rhodococcus sputi.

Rhodococcus sputi caused tuberculosislike lymphadenitis of mesenteric lymph nodes in swine. This is the first study reporting that R. sputi can be a pathogen in swine.

Avian mycobacteriosis in three horses.

The clinical, bacteriologic and pathologic findings of three adult horses suffering from avian tuberculosis are presented. Chronic weight loss and hypoproteinemia were pertinent clinical abnormalities in all three horses. Gross pathologic lesions were characterized by chronic enterocolitis with mesenteric lymphadenopathy in two horses and hepatic granulomas in the third horse. The microscopic diagnoses were chronic, non-caseating granulomatous enterocolitis, and necrotizing, non-mineralizing granulomatous hepatitis, respectively. All three horses had granulomatous lymphadenitis of mesenteric lymph nodes with varying degrees of non-mineralizing, coagulation necrosis. Various serotypes of the Mycobacterium avium-intracellulare complex were isolated from selected tissues and feces.