Erosive colitis in experimental canine Leishmaniasis

Infection by Leishmania (Leishmania) infantum chagasi causes intestinal changes B-1 cells dependent

Evaluating the histopathological and morphometric changes caused by Leishmania (Leishmania) infantum chagasi infection either in the presence or absence of B-1 cells. Wild-type Balb/c and XID mice were used. Half of XID mice received B-1 cells adoptive transfer (XID + B1). Five animals from each group were infected (Balb/c I, XID I and XID + B1 I), totalizing six groups (n = 5). After 45 days of infection, the ileum was collected for histological processing and analysis. After infection, the XID animals showed an increase in the thickness of the intestinal layers, in the depth and width of the crypt and in the villi width. However, the Balb/c I group showed a reduction in almost all these parameters, whereas the villi width was increased. The villi height decreased in the infected XID animals; however, it was increased in the XID + B1 I group. Leishmania (L) infantum chagasiinfection caused a decrease in the number of Paneth cells; however, their area was increased. Finally, goblet cells and enterocytes presented different change profiles among groups. This study showed that the parasite infection causes structural and histopathological alterations in the intestine. These changes might be influenced by the absence of B-1 cells.

Insights of Leishmania (Viannia) braziliensis infection in golden hamster (Mesocricetus auratus) intestine

AIM

The present study compared and evaluated morphological and quantitative alterations in the ileum of hamsters infected by two L. (V.) braziliensis strains isolated from patients with different lesion aspects and treatment responses.

MAIN METHODS

Hamsters were infected in the left hindpaw with a suspension of promastigotes (2 × 10⁷/100 μl) of two different strains of L. (V.) braziliensis. After 90 or 120 days, the animals were euthanized. Samples of the ileum and mesenteric lymph node were collected for histological examination and quantitative polymerase chain reaction.

KEY FINDINGS

All infected animals developed similar profile of paw lesions. In peripheral blood there was an increase in the number of mononuclear cells which contributed to elevated global leukocytes count. Increases in the width and height of villi and width and depth of crypts were observed. The thickness of the muscular layers, submucosa, and intestinal wall also increased. Histopathological alterations were observed, including inflammatory infiltrate in crypts and a large number of immune cells in the lamina propria, submucosa, and muscular layer. Immune cells were found inside myenteric ganglia, with an increase in the number of intraepithelial lymphocytes. Leishmania DNA was detected in the ileum and mesenteric lymph node at both times of infection. The presence of amastigotes in the ileum was revealed by immunohistochemistry.

SIGNIFICANCE

The infection with different strains of L. (V.) braziliensis causes morphological and quantitative alterations in the ileum of hamsters and the parasite can migrate to the mesenteric lymph node and intestine.

An Atypical Case of Leishmaniasis Associated with Chronic Duodenitis in a Dog

We describe an atypical case of duodenal leishmaniasis in a boxer dog presenting with chronic diarrhea and poor general condition. Antidiarrheic therapy was previously administered without success and inflammatory bowel disease localized to the small intestine was suspected, given the chronic clinical signs and by ruling out other known causes of gastrointestinal inflammation. Endoscopic biopsy of duodenum showed a moderate increase in lamina propria lymphocytes, plasma cells, and macrophages. Basophilic bodies were seen in the cytoplasm of numerous macrophages, suggestive of Leishmania spp, confirmed by immunostaining, and a diagnosis of granulomatous duodenitis associated to Leishmania infection was made. After 7 mo of therapy, a significant clinical improvement and weight gain were observed, and endoscopic histology showed no evidence of Leishmania. A progressive decline of anti-leishmanial antibody titer was also observed during follow-up. This report emphasizes the importance of atypical symptoms and the unusual location of visceral leishmaniasis, suggesting the need to consider leishmaniasis in the differential diagnosis of canine chronic enteritis, especially in endemic areas.

Glycol methacrylate embedding for the histochemical study of the gastrointestinal tract of dogs naturally infected with Leishmania infantum

In canine visceral leishmaniasis a diffuse chronic inflammatory exudate and an intense parasite load throughout the gastrointestinal tract has been previously reported. However, these studies did not allow a properly description of canine cellular morphology details. The aim of our study was to better characterize these cells in carrying out a qualitative and quantitative histological study in the gastrointestinal tract of dogs naturally infected with Leishmania infantum by examining gut tissues embedded in glycol methacrylate. Twelve infected adult dogs were classified in asymptomatic and symptomatic. Five uninfected dogs were used as controls. After necropsy, three samples of each gut segment, including esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, and rectum were collected and fixed in Carnoy's solution for glycol methacrylate protocols. Sections were stained with hematoxylin-eosin, toluidine blue borate, and periodic acid-Schiff stain. Leishmania amastigotes were detected by immunohistochemistry employed in both glycol methacrylate and paraffin embedded tissues. The quantitative histological analysis showed higher numbers of plasma cells, lymphocytes and macrophages in lamina propria of all segments of GIT of infected dogs than controls. The parasite load was more intense and cecum and colon, independently of the clinical status of these dogs. Importantly, glycol methacrylate embedded tissue stained with toluidine blue borate clearly revealed mast cell morphology, even after mast cell degranulation. Infected dogs showed lower numbers of mast cells in all gut segments than did controls. Despite the glycol methacrylate (GMA) protocol requires more attention and care than the conventional paraffin processing, this embedding procedure proved to be especially suitable for the present histological study, where it allowed to preserve and observe cell morphology in fine detail.

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).

Genital lesions and distribution of amastigotes in bitches naturally infected with Leishmania chagasi

Recent reports indicate that Leishmania chagasi has tropism to the male canine genital system, which is associated with shedding of the organism in the semen, supporting the hypothesis of venereal transmission. The aim of this study was to describe the lesions and assess parasite load in the genital system of bitches with canine visceral leishmaniasis (CanL). Symptomatic (n=5) and asymptomatic (n=5) bitches seropositive for CanL were randomly selected at the Center for Zoonosis Control (Belo Horizonte, State of Minas Gerais, Brazil). Five serologically negative, healthy, adult bitches also from the CZC were used as controls. Samples from genital organs (vulva, vagina, cervix, uterine body, uterine horns, uterine tubes, and ovaries), liver, and spleen were histologically evaluated and processed for immunodetection of Leishmania sp., and PCR. The most significant histological change was a mild to moderate vulvar dermatitis, characterized by a histio-plasma-lymphocytic infiltrate. This change was detected in all asymptomatic, four symptomatic, and three uninfected control bitches. In one symptomatic and one asymptomatic bitch intracytoplasmic amastigotes were observed within macrophages in the inflammatory infiltrate. Samples from all the segments of the genital tract were positive in at least one infected animal, in the absence of detectable amastigotes in the tissue. These findings support the notion that L. chagasi does not have genital tropism in the bitch, which is in contrast to our previous findings in naturally infected male intact dogs.

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.

An alternative immunohistochemical method for detecting Leishmania amastigotes in paraffin-embedded canine tissues

Canine visceral leishmaniasis (CVL) is a zoonosis and a chronic systemic disease of the dog caused by a protozoan by the species Leishmania infantum in the Old World and Leishmania chagasi in the New World. Several methods are currently employed for the diagnosis of CVL including microscopic detection of the parasite in bone marrow and lymph node aspirates, demonstration of specific antibodies anti-Leishmania in sera from infected animals, and isolation of the parasite by in vitro culture or by inoculation of laboratory animals. However, a definitive diagnosis is based on the actual detection of the parasite, which is conventionally achieved by examining Giemsa-stained smears or histopathological sections stained with hematoxylin and eosin. These methods have a low sensitivity, and therefore, they are often inconclusive. This is particularly true in canine organs that have a low level of parasitism such as kidneys, lungs, central nervous system, and testis, or, in some cases, the skin. The technique for immunohistochemical detection of leishmanial amastigotes in canine tissues has been reported previously and has proved to be undoubtedly efficient for the diagnosis. In this paper, we describe a straightforward and inexpensive immunohistochemical approach for Leishmania detection in formalin-fixed paraffin-embedded canine tissues. Amastigote forms of Leishmania were easily observed within macrophages in several organs from naturally infected dogs using the streptavidin-biotin immunohistochemical method with canine hyperimmune serum as the primary antibody. In addition, the secondary antibody used was not specific to canine immunoglobulin, characterizing a cross-immune reaction. Our results indicate that this technique could be a useful tool for epidemiological, clinical, and histopathological studies.

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.

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

Samples of stomach, duodenum, jejunun, ileum, cecum and colon were collected for Giemsa-smears ("imprints") from one asymptomatic mongrel dog, naturally infected with Leishmania (L) chagasi. Other fragments were obtained and fixed in formalin (10% and buffered) for histopathological and immunohistochemical studies. The immunohistochemistry was carried out by a streptavidin-peroxidase technique and it allowed to detect amastigote forms of Leishmania chagasi in the different paraffin gut sections. The principal lesion observed was a discrete to moderate chronic inflammatory reaction in the mucosa and submucosa in all fragments of the gastrointestinal tract (GIT). A chronic cellular exsudate was observed in all GIT tissues and it was composed by mononuclear cells (monocytes, plasmocytes and lymphocytes). A comparison between the two techniques showed that the immunohistochemistry study is the best method to detect amastigote forms of Leishmania.