Clinicopathological studies on ulcerative lymphangitis in cattle: Alterations in serum inflammatory cytokines, anti-microbial, organs functions, and oxidative stress-related biomarkers.

Background: Affection with Corynebacterium pseudotuberculosis (C. pseudotuberculosis) and development of cellulitis and/or abscess formation with cutaneous lymphangitis in cattle is rare to some extent, so literature about the biochemical changes that would accompany this infection is rare. Aim: In this context, the present study was designed to screen the effect of the infection with C. pseudotuberculosis cutaneous lymphangitis on the release of some immune molecules, organ functions, and redox state in Baladi cows. Methods: Fourteen Baladi cows from a small dairy farm in El-Behira, Egypt, were selected to complete this study. After bacteriological culture confirmation, seven of them were found suffering from cutaneous lesions due to infection with C. pseudotuberculosis (Diseased group), while the others were healthy (Healthy group). Serum samples were obtained to evaluate the presumptive changes in some clinicopathological parameters. Results: Serum analysis revealed a significant decrease in the levels of interferon-gamma and interleukin-17 as well as a significant decrement in the concentration of beta-defensin (ß-defensin) and lipocalin-2. While serum level of interleukin-10 recorded a significant increase in these animals when compared to healthy control animals. Concurrently, the affected animals recorded a significant elevation in serum levels of hepato-cardiac enzymes, urea, and creatinine in addition to disturbance in the serum redox state. Conclusion: In conclusion, infection with C. pseudotuberculosis cattle may disturb the defensive immune state, body organ function, and redox state of the animals.

Prevalence and risk factors for epizootic lymphangitis among equids in ethiopia during 2002-2023: A systematic review and meta-analysis.

In Sub-Saharan Africa (SSA), particularly in Ethiopia, Epizootic Lymphangitis (EL) is the most prevalent fungal disease of equids, which causes significant economic losses as well as a decrease in equid populations. Therefore, this systematic review and meta-analysis were designed to pool the results of individual studies and estimate the prevalence of EL among equids in Ethiopia. A systematic search of research articles on the prevalence and risk factors of EL among equids in Ethiopia was conducted in registers, databases, and other sources. Cochrane's Q, inverse variance (I2), sensitivity analysis, funnel plot, Begg's, and Egger's regression tests were used to check heterogeneity and publication bias. A random-effects model was used to calculate the pooled burden of EL among equids. For this meta-analysis, a total of 7217 equids were included in the 14 eligible studies. The overall pooled prevalence of EL among equids in Ethiopia was 20.24% (95% CI: 16.27, 24.21). According to the subgroup analysis, the highest prevalence was observed in cart horses (20.98%), the Amhara region (21.46%), and studies conducted using sample sizes of 384 equids or greater (24.67%) and from 2002 to 2018 (25.52%) study periods. Harness-inflicted wounds, sharing stables or yards with harnesses, and the presence of preexisting wounds were identified as factors significantly associated with EL magnitude. Early diagnosis and proper medication, as well as implementing appropriate prevention and control measures, are necessary for the management of EL in equids.

Growth inhibitory effect of selected medicinal plants from Southern Ethiopia on the mycelial phase of Histoplasma capsulatum var. farciminosum.

BACKGROUND: Epizootic lymphangitis is an infectious and chronically debilitating disease of the equines. Histoplasma capsulatum var. farciminosum, a thermally dimorphic fungi, is the causative agent for the disease. In Ethiopia, the disease significantly affects carthorses, posing threats to animal welfare, and resulting in substantial economic losses. Limited availability of widely accessible antifungals in addition to the chronic nature of the disease is the major challenge against management of epizootic lymphangitis. This study aimed to assess the in vitro efficacy of specific local medicinal plant extracts against the mycelial phase development of H. capsulatum var. farciminosum in southern Ethiopia. The leaves of Xanthium strumarium, Kanda (Family Rubiaceae), Croton macrostachyus (Bisana in Amharic), and Centella Asiatica (Echere waye as a local name in Zeyissegna) that are traditionally used for the treatment of different skin ailments were collected and extracted for the in vitro trial. RESULTS: The study revealed that methanol extracts of Xanthium strumarium, Kanda, Croton macrostachyus, and Centella Asiatica, at minimum inhibitory concentrations of 1.25 mg/ml, 2.5 mg/ml, 2.5 mg/ml, and 5 mg/ml, respectively, inhibited the growth of H. capsulatum var. farciminosum. CONCLUSION: This in vitro finding could serve as significant preliminary data in the exploration of effective alternative treatment options for epizootic lymphangitis. This study provides a crucial foundation for further research aimed at determining the chemical components and in vivo effectiveness of these plant extracts against both the mycelial and yeast forms of Histoplasma capsulatum var. farciminosum.

The socioeconomic impact of equine epizootic lymphangitis in working equids in low and middle-income countries: A scoping review.

Equine epizootic lymphangitis (EEL) is a very infectious and contagious fungal disease that, with its ocular, respiratory and skin forms, causes severe effects on the health and welfare of working equids. Treatment is expensive and rarely available in low and middle-income countries (LMICs). Epidemiological data is lacking in most countries where the disease is known to exist. The purpose of this scoping review is to identify the current knowledge on the socioeconomic impact of EEL in working equids in LMICs, to highlight knowledge gaps and provide recommendations for future research. Seven eligible papers were obtained from the search of four databases and backward citation searching. The review showed that the available research on this subject is very scarce and restricted to Ethiopia. From the results it emerged that EEL causes detrimental socioeconomic effects on working equids' owners, compromising their health and livelihood. Its economic consequences were attributed to the reduced working capacity and loss of sick animals. Among the social impacts, authors highlighted the stigma around sick equids and their owners. Further studies on the socioeconomic impact of EEL conducted in endemic areas are highly required. The integration of epidemiological data with socioeconomic impact studies from LMICs may promote funding allocation for the development of cost-effective treatments and vaccines and for implementing disease prevention and control programmes. Future research would gain from applying the One Health approach to better examine the multiplicity of the disease socioeconomic effects, therefore increasing the potential of research to orientate policy.

Comparative investigations into the growth details of Histoplasma capsulatum var farciminosum on four different agar media.

Epizootic equine lymphangitis (EEL) is a chronic fungal disease that affects equids. The causative agent is a dimorphic fungus called Histoplasma capsulatum var farciminosum. Histoplasmacapsulatum var farciminosum field strain 7 (D 2878/2023) isolated from the eye socket of an EEL Ethiopian horse was sub-cultured on four different solid media and incubated at 26°C and 37°C for 6 weeks. Details of growth morphology were recorded and shown in images during 6 weeks of incubation. Histoplasmacapsulatum var farciminosum grew best at 26°C on all four agars, but only on sheep blood agar at 37°C as small, white dry colonies.

Histoplasma capsulatum var farciminosum was isolated from the eye socket of an equine epizootic lymphangitis infected Ethiopian horse on Mycosel agar, which was sub-cultured on four different solid media at two different temperatures for 6 weeks to show its growth pattern.

Study on prevalence and associated risk factors of epizootic lymphangitis in equine in Nagele Arsi town, southeastern Ethiopia.

Epizootic lymphangitis is a contagious, chronic and overwhelming disease of equids, characterized by chronic discharging skin nodules. This study was aimed to investigate the prevalence and associated risk factors of epizootic lymphangitis in equines at Nagele Arsi town, southeastern Ethiopia. A cross-sectional study using a random sampling technique was employed from December 2021 to June 2022 via clinical and microscopic examinations of the lesions. The overall prevalence of epizootic lymphangitis was 4.37% with a prevalence of 6.69%, 0.72%, and 0% in horses, donkeys, and mules, respectively. The sex, species, harness type, season, and body condition scores of equids have shown statistically significant differences (p < 0.05) with the prevalence of epizootic lymphangitis. Macroscopically, the lesions revealed varying degrees of nodule to ulcer on the sternum, limbs, face, and cervical region of the equine. Upon giemsa stain, fungal hyphae with a halo (unstained capsule-like) structure were observed. Histologically, pyogranulomatous inflammation with fibroplasia was appreciated. In conclusion, epizootic lymphangitis was rampant in the study area. This requires a detailed investigation incorporating a large sample size using fungal culture and other molecular techniques including PCR.

Ultrasonographic features of intestinal lipogranulomatous lymphangitis in 10 dogs.

Intestinal lipogranulomatous lymphangitis (ILL) is a granulomatous inflammation of the lymphatic vessels of the intestinal wall and mesentery characterized by lipogranulomas. The purpose of this retrospective, multi-center, case series study is to report the ultrasonographic features of canine ILL. Ten dogs with a histologically confirmed ILL undergoing preoperative abdominal ultrasound were retrospectively included. Additional CT was available in two cases. Lesion distribution was focal in eight dogs and multifocal in two. All dogs presented with intestinal wall thickening and two had a concomitant mesenteric mass adjacent to the intestinal lesion. All lesions were in the small intestine. Ultrasonographic features were altered wall layering with predominantly muscular and to a lesser extent submucosal layer thickening. Other findings included hyperechoic nodular tissue within the muscular, serosa/subserosal, and mucosal layers, hyperechoic perilesional mesentery, enlarged submucosal blood/lymphatic vessels, mild peritoneal effusion, intestinal corrugation, and mild lymphadenomegaly. The two intestinal to mesenteric masses presented heterogeneous echostructure, predominantly hyperechoic with multiple hypo/anechoic cavitations filled with mixed fluid and fat attenuation content on CT. Histopathological findings included lymphangiectasia, granulomatous inflammation, and structured lipogranulomas affecting mainly submucosa, muscularis, and serosa. The intestinal to mesenteric cavitary masses revealed severe granulomatous peritonitis with steatonecrosis. In conclusion, ILL should be considered as a differential diagnosis for dogs with this combination of ultrasonographic features.

Computed tomographic features of focal lipogranulomatous lymphangitis for differentiating from malignant intestinal lesions in a dog.

An eight-year-old Maltese dog presented with diarrhea and anorexia. Ultrasonography revealed marked focal wall thickening with loss of layering in the distal ileum. Contrast-enhanced computed tomography (CT) revealed a preserved wall layer with hypoattenuating middle wall thickening. In some segments of the lesion, small nodules protruding toward the mesentery from the outer layer were observed. Histopathology revealed focal lipogranulomatous lymphangitis (FLL) with lymphangiectasia. This is the first report to describe the CT features of FLL in a dog. CT features of preserved wall layers with hypoattenuating middle wall thickening and small nodules can assist in diagnosing FLL in dogs.

Evaluation of the degree and distribution of lymphangiectasia in full-thickness canine small intestinal specimens diagnosed with lymphoplasmacytic enteritis and granulomatous lymphangitis.

Intestinal lymphangiectasia (IL) is often observed in dogs with chronic small intestinal diseases. Hypoplasia of the lymphatic vessel due to decreased lymphangiogenesis, which has been suggested in human idiopathic IL, may contribute to the pathogenesis of canine IL. This study aimed to evaluate the diameter and number of lymphatic vessels in full-thickness small intestinal specimens of dogs with IL. Immunohistochemical labeling of lymphatic endothelial cell markers was performed on retrospectively retrieved full-thickness small intestinal specimens. Sixteen dogs with histologically confirmed IL were included, of which 10 had lymphoplasmacytic enteritis (LPE), and six had granulomatous lymphangitis (GL). Nine dogs that died from non-gastrointestinal disorders and with little or no abnormalities in the small intestine were used as controls. Lymphatic vessel diameters in dogs with IL were significantly increased in all layers of the small intestine, including the villus lacteal, lamina propria, submucosa, muscularis, and mesentery, compared with controls (all P<0.01). There was no significant difference in the lymphatic vessel diameters between dogs with LPE and GL (all P>0.05). There was no significant difference in the number of lymphatic vessels between dogs with IL and the controls in all layers of the small intestine (all P>0.05). This study demonstrated that IL was observed in all layers of the small intestine, including the submucosa, muscularis, and mesentery, independent of the underlying disease. Factors other than reduced lymphatic vessels would contribute to the pathogenesis of IL in dogs.

Epidemiology of epizootic lymphangitis of carthorses in northern Ethiopia using conventional diagnostic methods and nested polymerase chain reaction.

BACKGROUND: Epizootic lymphangitis (EL), caused by Histoplasma capsulatum variety farciminosum (HCF) is a contagious, chronic disease of equines, characterized by development of nodular lesions in the lymph nodes, lymphatic vessels and skin. It is one of the most important diseases of equines in Ethiopia, causing significant economic loss, particularly in the livelihood of carthorse owners. To date there is neither effective diagnostic nor control measure implemented in the country. Furthermore, there is a shortage of data on the epidemiology of the disease in different regions of this country. The aim of this study was to investigate epidemiology of EL in northern Ethiopia, using the conventional methods as well as nested polymerase chain reaction (PCR). RESULTS: The presence of HCF genetic material was confirmed in 44% (84/191) of the carthorses. Subclinical infection was observed in 18.2% (22/121) of the apparently healthy carthorses. Considering the nested PCR as a gold standard, sensitivity and specificity of clinical examination were 74% and 92.5%, respectively, while the area under the ROC curve (AUR) was 0.83 (95% confidence interval, 0.77, 0.896). Moreover, a moderate (k = 0.675) agreement observed between the nested PCR and clinical examination. CONCLUSIONS: This study demonstrated widespread occurrence of EL in northern Ethiopia, and the advantage of the nested PCR in detecting infection of HCF, even before the clinical symptoms became apparent.

In Vitro Evaluation of the Effects of Selected Plants on the Growth of the Mycelial Form of Histoplasma capsulatum Variety farciminosum in Ethiopia.

Epizootic lymphangitis is prevalent in equines in Ethiopia, causing remarkable economic and welfare impacts but often neglected. Lack of effective treatment contributed to its continued occurrence, and hence, search for an effective treatment should be considered a priority area to minimize its impacts. Previous ethnobotanical studies have reported that Curcuma longa, Phytolacca dodecandra, and Datura stramonium were used to treat cutaneous fungal infections and reduce their incidence. The treatment effects of these plants against epizootic lymphangitis should be studied. The in vitro growth inhibitory effects of methanol extracts of the root of C. longa, berry of P. dodecandra, and leaf of D. stramonium were evaluated. Histoplasma capsulatum var farciminosum was isolated from clinical cases of epizootic lymphangitis in carthorses in central Ethiopia. The nested polymerase chain reaction was used to confirm the identity of the isolates. Serial twofold dilutions of the extract of berries of P. dodecandra and leaves of D. stramonium were done in sterile water, whereas dilution of the extract of roots of C. longa was done in dimethylsulphoxide. The effects of the plants on the growth of Histoplasma capsulatum var farciminosum were assessed by agar dilution assay. Culture media with no antifungal agent and media containing ketoconazole served as negative and positive control, respectively. The methanol extract of C. longa showed inhibitory effects at concentrations ranging from 0.07 to 5 mg/mL. Similarly, the methanol extract of P. dodecandra showed growth inhibitory effects at concentrations ranging from 0.156 to 5 mg/mL. That is, the growth inhibitory concentration of C. longa was 0.07 mg/mL, whereas that of P. dodecandra was 0.156 mg/mL. In contrast, D. stramonium showed no inhibitory effect. This preliminary observation showed that methanol extracts of C. longa and P. dodecandra showed inhibitory effects on the growth of Histoplasma capsulatum var farciminosum requiring further repeated in vitro evaluation so as to generate adequate evidence, which would justify in vivo trials.

Is Corynebacterium pseudotuberculosis infection (pigeon fever) in horses an emerging disease in western Canada?

This report describes 5 horses in the southern Alberta region with typical and atypical external abscessation due to Corynebacterium pseudotuberculosis (pigeon fever). "Pigeon fever" has recently been diagnosed in new geographic regions in North America and should be kept as a differential diagnosis by practitioners when an external or internal abscess is identified in a horse.

L'infection parCorynebacterium pseudotuberculosis(fièvre du pigeon) chez les chevaux est-elle une maladie émergente dans l'Ouest canadien? Ce rapport décrit cinq chevaux dans la région sud de l'Alberta atteints d'abcès externes typiques et atypiques causés par Corynebacterium pseudotuberculosis (fièvre du pigeon). La «fièvre du pigeon¼ a récemment été diagnostiquée dans de nouvelles régions géographiques de l'Amérique du Nord et devrait être conservée comme diagnostic différentiel par les praticiens lorsqu'un abcès externe ou interne est identifié.(Traduit par Isabelle Vallières).

Development and Evaluation of a Molecular Diagnostic Method for Rapid Detection of Histoplasma capsulatum var. farciminosum, the Causative Agent of Epizootic Lymphangitis, in Equine Clinical Samples.

Histoplasma capsulatum var. farciminosum, the causative agent of epizootic lymphangitis (EZL), is endemic in parts of Africa. Diagnosis based on clinical signs and microscopy lacks specificity and is a barrier to further understanding this neglected disease. Here, a nested PCR method targeting the internal transcribed spacer (ITS) region of the rRNA operon was validated for application to equine clinical samples. Twenty-nine horses with signs of EZL from different climatic regions of Ethiopia were clinically examined. Blood samples and aspirates of pus from cutaneous nodules were taken, along with blood from a further 20 horses with no cutaneous EZL lesions. Among the 29 horses with suspected cases of EZL, H. capsulatum var. farciminosum was confirmed by extraction of DNA from pus and blood samples from 25 and 17 horses, respectively. Positive PCR results were also obtained with heat-inactivated pus (24 horses) and blood (23 horses) spotted onto Whatman FTA cards. Two positive results were obtained among blood samples from 20 horses that did not exhibit clinical signs of EZL. These are the first reports of the direct detection of H. capsulatum var. farciminosum in equine blood and at high frequency among horses exhibiting cutaneous lesions. The nested PCR outperformed conventional microscopic diagnosis, as characteristic yeast cells could be observed only in 14 pus samples. The presence of H. capsulatum var. farciminosum DNA was confirmed by sequencing the cloned PCR products, and while alignment of the ITS amplicons showed very little sequence variation, there was preliminary single nucleotide polymorphism-based evidence for the existence of two subgroups of H. capsulatum var. farciminosum This molecular diagnostic method now permits investigation of the epidemiology of EZL.

Focal intestinal lipogranulomatous lymphangitis in 10 dogs.

OBJECTIVES: To describe the clinical and pathological features of canine focal lipogranulomatous lymphangitis, to evaluate its underlying infectious cause and to compare it with human Crohn's disease. METHODS: Retrospective review of case records with a histopathological diagnosis of focal lipogranulomatous lymphangitis. Bacterial and fungal colonisation was evaluated using fluorescence in situ hybridisation and histochemical staining, respectively. A comparison with Crohn's disease was performed by a human pathologist. RESULTS: Ten dogs were evaluated. The historical complaints were predominantly chronic diarrhoea (10/10) and vomiting (5/10). The biochemical abnormalities included hypoalbuminaemia (6/10) and hypocobalaminaemia (4/6). Abdominal sonography revealed a thickened distal ileum±ileocolic junction. Colonoscopy showed a swollen caecal ostium and oedematous caecum in 7/10 dogs. A stenotic ileo-colic opening prevented endoscopic intubation in all dogs. Histology from the resected lesions revealed granulomatous inflammation involving the muscularis and serosa. Fluorescence in situ hybridization demonstrated invasive bacteria in 2/10 dogs. Post-resection, all dogs received metronidazole and tapering immunosuppressive doses of prednisolone. Remission (median 17 months) was achieved in 8/10 dogs. CLINICAL SIGNIFICANCE: Focal lipogranulomatous lymphangitis is a rare and severe form of canine inflammatory bowel disease with preferential localisation to the ileum and the ileocolic junction. An underlying infectious aetiology was not identified.

Participatory appraisal of the impact of epizootic lymphangitis in Ethiopia.

Epizootic lymphangitis (EZL) is reported to have a significant impact upon livelihoods within resource-poor settings. This study used a participatory approach to explore peoples' experiences of EZL and examine the perceived impact of disease, owner knowledge and understanding of EZL, lay management of disease and, attitudes and strategies towards disease prevention. Focus-group discussions were held with 358 cart-horse owners and drivers recruited from 7 towns attended by SPANA (Society for the protection of animals abroad) mobile veterinary clinics and 2 unexposed towns where no SPANA clinics were available. Focus group discussions explored four main research questions: (1) Is EZL recognised by animal owners, and is this considered an important disease in equids? (2) What factors do animal owners associate with the development of disease? (3) What happens to an animal with clinical disease and how does this impact upon the owner/community? (4) Are measures taken to reduce disease occurrence? These key areas were explored using photographs, disease ranking, matrices and open discussion. Data were analysed using descriptive statistics and thematic analysis. The results are presented thematically and include: recognition and descriptions of EZL, treatment strategies used, disease priorities and ranking, impact of disease, disease transmission and attitudes and approaches to disease prevention. EZL was widely recognised and ranked highly as an important disease of equids. However, there was uncertainty around identifying early cases of EZL, and this could impact upon the timing of initiating treatment and separating potentially infectious animals. People had varying knowledge of effective methods for disease prevention and reported particular difficulties with isolating infected animals. The impact of EZL was multi-dimensional and encompassed effects upon the horse, the individual owner and the wider society. Working equids provide a vital utility and source of income to many people in resource-poor settings. Often, infection with EZL resulted in a reduction in working ability which had a direct impact upon the livelihoods of owners and their dependent family members. EZL also impacted upon the welfare of the horse as sick animals continued to be worked and, in advanced cases, horses were abandoned due to ineffective or unavailable treatment. This study conceptualises the importance of EZL due to the effects of the disease on the horse and its impact upon human livelihoods. Epizootic lymphangitis is a neglected disease that requires further investigation in order to develop practical and sustainable disease control strategies within endemic regions.

Emphysematous Eosinophilic Lymphangitis in the Ruminal Submucosa of Cattle.

Twenty cattle (14 Holstein-Friesian, 3 Japanese Black, 3 Aberdeen Angus) ranging in age from 3 months to 8 years exhibited, at slaughter, emphysematous thickening of the ruminal submucosa owing to the appearance of numerous, contiguous, small gas bubbles. Microscopic changes in the ruminal submucosa consisted of (1) multiple cystic (emphysematous) lymphangiectasis that was frequently lined or occluded by granulomatous inflammatory infiltrates including macrophages, multinucleate giant cells, and eosinophils; (2) intralymphatic phagocytosis by macrophages and giant cells of eosinophils that showed positive labeling with the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling assay; and (3) an inflammatory infiltrate extending from the area of lymphangitis into surrounding tissue, as well as edema, hemorrhage, fibrin exudation, fibroplasia, or capillary proliferation throughout the lesional submucosa. In addition, 15 (75%) of the cattle had globular leukocyte infiltrates in the mucosal epithelia of the rumen.

Focal intestinal lipogranulomatous lymphangitis in 6 dogs (2008-2011).

BACKGROUND: Lipogranulomatous lymphangitis is inflammation of the intestinal lymphatic vessels and surrounding tissues caused by chronic leakage of lipid-laden chyle. Grossly, lipogranulomas are typically disseminated small masses on the serosa and surrounding lymphatic vessels and consist of epithelioid macrophages, multinucleated giant cells, and cholesterol. Lipogranulomatous lymphangitis is occasionally seen in patients with lymphangiectasia and protein-losing enteropathy (PLE). OBJECTIVES: To characterize the historical features, clinical signs, treatment, histopathology, and outcome of dogs with focal lipogranulomatous lymphangitis. ANIMALS: Six dogs with ultrasonographic evidence of focal, regional small intestinal masses, often with involvement of the adjacent mesentery, and a diagnosis of focal lipogranulomatous lymphangitis based on histopathology of biopsied masses. RESULTS: The median age of dogs was 6.9 years (range 3-10 years). All dogs had total protein, globulin, and albumin concentrations within the reference range at initial presentation and had intestinal masses identified on abdominal ultrasound examination. Histopathologic evaluation of lesions identified severe mural and mesenteric lipogranulomatous lymphangitis. Lymphangiectasia was noted in 5 cases and only in sections within the mass-like lesion; tissue without lipogranulomas had minimal lymphangiectasia, suggesting a localized phenomenon. Postoperative outcomes ranged from remission of clinical signs with no subsequent treatment for 10-12 months in 2 dogs, postoperative management with medical and nutritional management in 3 dogs, and no outcome for 1 case. CONCLUSIONS AND CLINICAL IMPORTANCE: This case series describes a unique mass-like manifestation of intestinal lipogranulomatous lymphangitis and should be considered as a possible differential diagnosis in dogs with an intestinal mass.

Granulomatous typhlocolitis, lymphangitis, and lymphadenitis in a horse infected with Listeria monocytogenes, Salmonella Typhimurium, and cyathostomes.

A 15-year-old American Quarter horse mare was euthanized because of poor response to therapy for severe diarrhea. Significant gross findings were limited to the large intestines. The walls of the cecum and colon were thickened with widely scattered nodules in the mucosa and submucosa that extended into the enlarged colic lymph nodes. Microscopically, there was severe granulomatous typhlocolitis, lymphangitis, and lymphadenitis, with many intralesional Gram-positive, non-acid-fast coccobacilli and few cyathostomes. Intralesional bacteria were immunohistochemically and polymerase chain reaction (PCR) assay positive for Listeria monocytogenes. Concurrent infection with Salmonella enterica serovar Typhimurium was detected by PCR and culture. Infection with L. monocytogenes in horses is rare, and coinfection with Salmonella and small strongyles probably contributed to the development of granulomatous typhlocolitis.