Histopathological and immunohistochemical study of the gastrointestinal tract from a dog naturally infected with Leishmania (Leishmania) chagasi: a case report

Neutrophils, eosinophils, and mast cells in the intestinal wall of dogs naturally infected with Leishmania infantum

Visceral leishmaniasis (VL) is a disease caused by the protozoa Leishmania infantum and can cause an inflammatory reaction in the gastrointestinal tract, however the role of granulocytic cells (neutrophils, eosinophils, and mast cells) in the intestine of dogs infected is not fully understood. We performed a quantitative analysis these cells in the intestinal wall of dogs with canine visceral leishmaniasis (CVL). Twenty dogs were assigned to one of three groups: group 1 (G1, n=8), dogs with CVL and L. infantum amastigotes in the intestine; group 2 (G2, n=9), dogs with CVL but without intestinal amastigotes; and group 3 (G3, n=3), uninfected dogs (control group). Granulocytic cells were counted in the crypt-villus unit (mucosa), submucosa, and muscle layer of the intestinal mucosa. Cell counts were higher in the intestinal wall of dogs from G2 followed by G1 and G3 (p≤0.05). In G1, there was a low inverse correlation between parasite burden of the small intestine and granulocyte counts (r= -0.1, p≤0.01). However, in G2 dogs, mast cell and eosinophil numbers showed positive correlation (r=0.85, p≤0.01). The granulocytic cell hyperplasia observed in the intestine of L. infantum-infected dogs suggests that these cells may be involved in the cell-mediated immune response for parasite elimination.

Correlation study and histopathological description of intestinal alterations in dogs infected with Leishmania infantum

The aim of this work was a correlation study and histopathological description of alterations associated with the presence of Leishmania infantumamastigote in the intestinal wall of dogs infected with canine visceral leishmaniasis (CVL). Three groups were used: G1 (n = 8), comprising naturally infected dogs with CVL with amastigotes of L. infantum in the small and large intestines; G2 (n = 9), infected dogs with CVL, without intestinal amastigotes; and G3 (n = 3), uninfected dogs. Histochemistry and immunohistochemistry methods were used for histopathology and amastigotes identification. 47.1% (8/17) of dogs from G1 group had amastigotes in the mucosa, submucosa and muscle layers of the small and large intestines and it was observed a prominent inflammatory reaction characterized by chronic infiltration of mononuclear cells: macrophages, lymphocytes and plasma cells. Comparison between the groups showed only a significant difference in relation to mucosal microscopic structural alterations in dogs from G1 in relation to G2 and G3. Parasite burden showed significant correlations with the microscopic alterations and clinical status of dogs in G1. By the conclusion, the inflammatory reactions caused by the parasites in the intestines might have contributed towards alterations in digestive processes, worsening the dogs' clinical status of CVL.

Expression of regulatory T cells in jejunum, colon, and cervical and mesenteric lymph nodes of dogs naturally infected with Leishmania infantum

Using flow cytometry, we evaluated the frequencies of CD4(+) and CD8(+) T cells and Foxp3(+) regulatory T cells (Tregs) in mononuclear cells in the jejunum, colon, and cervical and mesenteric lymph nodes of dogs naturally infected with Leishmania infantum and in uninfected controls. All infected dogs showed chronic lymphadenitis and enteritis. Despite persistent parasite loads, no erosion or ulcers were evident in the epithelial mucosa. The colon harbored more parasites than the jejunum. Frequencies of total CD4(+), total Foxp3, and CD4(+) Foxp3(+) cells were higher in the jejunum than in the colon. Despite negative enzyme-linked immunosorbent assay (ELISA) serum results for cytokines, levels of interleukin-10 (IL-10), gamma interferon (IFN-γ), transforming growth factor beta (TGF-β), and tumor necrosis factor alpha (TNF-α) were higher in the jejunum than in the colon for infected dogs. However, IL-4 levels were higher in the colon than in the jejunum for infected dogs. There was no observed correlation between clinical signs and histopathological changes or immunological and parasitological findings in the gastrointestinal tract (GIT) of canines with visceral leishmaniasis. However, distinct segments of the GIT presented different immunological and parasitological responses. The jejunum showed a lower parasite load, with increased frequencies and expression of CD4, Foxp3, and CD8 receptors and IL-10, TGF-β, IFN-γ, and TNF-α cytokines. The colon showed a higher parasite load, with increasing expression of IL-4. Leishmania infantum infection increased expression of CD4, Foxp3, IL-10, TGF-β, IFN-γ, and TNF-α and reduced CD8 and IL-4 expression in both the jejunum and the colon.

Expression of Toll-like receptors 2 and 9 in cells of dog jejunum and colon naturally infected with Leishmania infantum

BACKGROUND

Infection with parasite protozoa is a long-term health issue in tropical and subtropical regions throughout the world. The Toll-like receptor (TLR) signaling pathway is one of the first-responding defense systems against Leishmania. The aim of this study was to investigate the expression of TLR2 and TLR9 in jejunum and colon and its correlation with CD11c, CD11b, and CD14 receptors used as markers for dendritic cells and macrophages.

METHODS

Twenty four dogs infected with Leishmania infantum were used in this study. Cytometry was carried out in lamina propria cells from jejunum and colon using markers for TLR2, TLR9, CD11b, CD11c and CD14.

RESULTS

Cellular inflammatory exudate was diffuse in the mucosa and submucosa, predominately comprising mononuclear cells: plasma cells, macrophages, and lymphocytes. Despite the parasite load, microscopy showed no erosion was evident in the epithelial mucosa layers. The colon harbored more parasites than the jejunum. Flow cytometry revealed higher frequency of TLR2+ and CD11c+ dendritic cells in the colon than in the jejunum. Conversely, TLR9-expressing cells were more frequent in jejunum. Moreover, frequency of macrophages (CD11b+ and CD14+) expressing simultaneity TLR9 were lower in the colon than in jejunum, while CD11c+ cells predominated in the colon. Despite of the negative ELISA serum results, IL-10 and TNF-α were higher in jejunum than colon of infected animals. However, IL-4 was higher in colon than jejunum of infected animals. A higher expression these cytokines were demonstrated in infected dogs compared to uninfected dogs.

CONCLUSIONS

There was no correlation between clinical signs and pathological changes and immunological and parasitological findings in the gastrointestinal tract in canine visceral leishmaniasis. However, jejunum showed a lower parasite load with increased frequency and expression of CD11b, TLR9, CD14/CD11b/TLR9 receptors and IL-10 and TNF-α cytokines. Conversely, the colon showed a higher parasite load along with increased frequency and expression of TLR2, CD11c receptors, and IL-4 cytokine. Thus, Leishmania infantum is able to interfere in jejunum increased expression of TLR2, TLR9, CD11b, CD14, CD14/CD11b/TLR9 receptors, IL-10, and TNF-α; and in colon increased expression of CD11c, TLR2, TLR9, CD11b, CD14 e, CD14/CD11b/TLR9 receptors, IL-10, and TNF-α.

Histopathological and parasitological study of the gastrointestinal tract of dogs naturally infected with Leishmania infantum

Background

The aim of this study was to provide a systematic pathological and parasitological overview of the gastrointestinal tract (GIT), including the stomach, duodenum, jejunum, ileum, caecum and colon, of dogs naturally infected with Leishmania.

Methods

Twenty mongrel dogs naturally infected with Leishmania (Leishmania) infantum and obtained from the Control Zoonosis Center of the Municipality of Ribeirão das Neves, Belo Horizonte Metropolitan area, Minas Gerais (MG) state, Brazil, were analyzed. The dogs were divided into two groups: Group 1 comprised nine clinically normal dogs and group 2 comprised 11 clinically affected dogs. After necropsy, one sample was collected from each GIT segment, namely the stomach, duodenum, jejunum, ileum, caecum and colon. Furthermore, paraffin-embedded samples were used for histological and parasitological (immunohistochemistry) evaluation and a morphometrical study were carried out to determine the parasite load (immunolabeled amastigote forms of Leishmania). The Friedman and the Mann Whitney tests were used for statistical analysis. The Friedman test was used to analyze each segment of the GIT within each group of dogs and the Mann Whitney test was used to compare the GIT segments between clinically unaffected and affected dogs.

Results

The infected dogs had an increased number of macrophages, plasma cells and lymphocytes, but lesions were generally mild. Parasite distribution in the GIT was evident in all intestinal segments and layers of the intestinal wall (mucosal, muscular and submucosal) irrespective of the clinical status of the dogs. However, the parasite load was statistically higher in the caecum and colon than in other segments of the GIT.

Conclusion

The high parasite burden evident throughout the GIT mucosa with only mild pathological alterations led us to consider whether Leishmania gains an advantage from the intestinal immunoregulatory response (immunological tolerance).

Canine visceral leishmaniasis: a remarkable histopathological picture of one asymptomatic animal reported from Belo Horizonte, Minas Gerais, Brazil

A remarkable histopathological picture of one asymptomatic dog naturally infected with Leishmania infantum (syn. chagasi) has been presented. Intracellular parasites were ease found in macrophages of all exanimated organs, especially in skin. Embedded paraffin tissues of liver, spleen, axillary and popliteal lymph nodes, and skin (ear, muzzle and abdomen) were stained by hematoxylin and eosin and by immunocytochemical reaction (streptoavidin-peroxidase method) to detect parasites. All organs showed an intense parasitism associated to severe pathological changes. All lymph nodes had conspicuous histological architecture alterations. Lymphocytes were replaced by macrophages stuffed with an intense number of amastigotes forms of Leishmania. The lymphoid nodules (without germinal centers) and the mantle zones in the cortex that surround the follicles were markedly attenuated. Livers showed small intralobular granulomas composed by macrophages loaded with amastigotes. Spleens had an intense depression of the white pulp whereas the lymphocytes were replaced by parasitized macrophages. All fragments of different anatomical region of skin (ear, muzzle and abdomen) showed a diffuse chronic inflammation. The cellular exudate was composed by macrophages, plasmocytes and lymphocytes. Macrophages loaded with amastigotes were ease found in all tissue fragments, but more intense in ear and muzzle. Thus, this fact enhances the importance of asymptomatic dogs in the epidemiology of visceral leishmaniasis.

Canine visceral leishmaniasis: a histopathological study of lymph nodes

Canine visceral leishmaniasis (CVL) is a zoonosis and a chronic systemic disease of the dog caused by a protozoan of the genus Leishmania. In the New World, the disease is caused by the species Leishmania (Leishmania) chagasi. There are only a few studies on the histopathology of lymph nodes in canine leishmaniasis. In the present paper, we report a histopathological description of lymph nodes considering animals with a defined clinical status and the parasite burden of lymph node tissues. Forty-eight mongrel dogs naturally infected with L. chagasi, were obtained from two endemic areas of Brazil. Cervical, axillary and popliteal lymph nodes were analyzed. The parasite burden, expressed as "Leishman-Donovan units", was variable among the defined types of clinical condition. Asymptomatic dogs can show higher parasitism than oligosymptomatic or symptomatic animals. Grossly, a generalized lymphadenopathy was found, but it was mainly observed in cervical and popliteal nodes. Histologically, the increased number and size of lymphoid follicles, and the marked hypertrophy and hyperplasia of medullary macrophages (cords and sinus) explained the lymphadenopathy. In addition, the clinical status or the tissue parasitism load might not be directly related to the intensity of the lesions.