A standardized cytological and immunochemical method for the analysis of fine-needle spleen aspirates: Assessment of leukocyte population changes in canine visceral leishmaniosis

Hematological Changes in Dogs with Visceral Leishmaniasis Are Associated with Increased IFN-γ and TNF Gene Expression Levels in the Bone Marrow

Visceral leishmaniasis is associated with a variety of hematological abnormalities. In this study, we correlated the hematological changes in the peripheral blood of dogs naturally infected with Leishmania infantum (L. infantum) with the distribution of cell lineages and cytokine gene expression patterns in the bone marrow. Samples from 63 naturally semidomiciled dogs living in an endemic area of visceral leishmaniasis were analyzed. L. infantum infection was detected in 50 dogs (79.3%). Among those, 18 (32%) had positive splenic cultures and showed more clinical signs. They also had lower red blood cell counts and leukocytosis with an increased number of neutrophils and monocytes in peripheral blood compared to dogs negative to this test. L. infantum DNA was detected in the bone marrow of 8/14 dogs with positive splenic culture. Dogs with L. infantum infection in the bone marrow presented with histiocytosis (p = 0.0046), fewer erythroid cell clusters (p = 0.0127) and increased gene expression levels of IFN-γ (p = 0.0015) and TNF (p = 0.0091). The data shown herein suggest that inflammatory and cytokine gene expression changes in bone marrow may contribute to the peripheral blood hematological changes observed in visceral leishmaniasis.

Isolation of naturally infecting Leishmania infantum from canine samples in Novy-MacNeal-Nicolle medium prepared with defibrinated blood from different animal species

The most commonly used culture medium for the in vitro isolation of Leishmania spp. from canine biological samples is biphasic Novy-MacNeal-Nicolle (NNN) medium, whose solid phase is prepared using rabbit blood. Leishmania infantum parasites from natural infections are highly sensitive and demanding for growth in axenic conditions when firstly obtained from the dog's body. The objective of this study was to evaluate whether NNN medium (NNN-test) prepared with chicken blood (NNN-C), ox blood (NNN-O), horse blood (NNN-H) or sheep blood (NNN-S) was viable for the isolation of parasites from naturally infected dogs, in an endemic area for visceral leishmaniasis caused by L. infantum. Spleen aspirates from six dogs previously diagnosed as infected by parasitological methods were simultaneously inoculated in each NNN-test medium, including the conventional medium prepared with rabbit blood (NNN-R), and the cultures were examined for three weeks under optic microscopy. Spleen samples were also analyzed for parasite loads by quantitative PCR (qPCR). Cultures from three of the six dogs (50%) were positive in at least one of the NNN-test media: one sample presented the highest spleen parasite load by qPCR (1.19 × 10⁴ parasites/mL) and was positive in all test media; the second sample presented parasitic isolation in the first week of culture in all inoculated media, of which the NNN-C medium had the highest mean parasite count (NNN-C = 23.5 × 10⁴/mL vs. NNN-R = 3.25 × 10⁴/mL); the third sample was positive only in the NNN-S medium besides the conventional control NNN-R. Cultures from the three remaining dogs were negative in all NNN media, including the control and test media; of those three dogs, two presented the lowest spleen parasitic loads according to qPCR. Blood from chicken, ox, horse and sheep shown to be viable for the preparation of NNN culture medium for the primary isolation of L. infantum from samples of naturally infected dogs and can be considered as an alternative to rabbit blood when necessary.

Magalhães-Junior J, Souza BM, Franke CR, Veras PS, Larangeira DF, Barrouin-Melo SM. Avaliação da infectividade parasitária a Lutzomyia longipalpis por xenodiagnóstico em cães tratados para leishmaniose visceral naturalmente adquirida

RESUMO: O efeito de um protocolo quimioterápico multidrogas contra a leishmaniose visceral (LV) canina, sobre a capacidade de transmissão de Leishmania infantum ao vetor, foi analisado por meio de xenodiagnóstico. Trinta e cinco cães naturalmente infectados foram avaliados antes e durante o tratamento com a combinação de metronidazol, cetoconazol e alopurinol a cada três meses por até um ano. Em cada avaliação, os cães foram individualmente submetidos ao xenodiagnóstico e quantificação da carga parasitária por PCR quantitativa. O tratamento foi eficaz em bloquear a transmissibilidade parasitária do cão para o flebotomíneo (p= 0,011) nos cães avaliados. Houve significante correlação entre recuperação clínica e infectividade: cães com melhora clínica mais evidente apresentaram menores chances de transferir L. infantum ao Lutzomyia longipalpis via xenodiagnóstico (r=0,528, p= 0,002). Esses resultados demonstram que o tratamento canino com o protocolo proposto pode representar uma alternativa ao sacrifício de cães no Brasil como medida de controle da doença, uma vez que as drogas utilizadas não são aplicadas ao tratamento da LV humana em áreas endêmicas.

Parasite load in the blood and skin of dogs naturally infected by Leishmania infantum is correlated with their capacity to infect sand fly vectors

The sand fly Lutzomyia longipalpis is primarily responsible for the transmission of visceral leishmaniasis (VL) in the New World, and dogs are considered to be the main urban reservoir of this disease. In order to improve the efficacy of control measures, it is essential to assess the transmission capacity of Leishmania infantum to the sand fly vector by naturally infected dogs. The present study investigated the existence of correlations between canine clinical presentation and the intensity of parasite load in the blood, skin and spleen of naturally infected dogs. In addition, we also attempted to establish correlations between the intensity of parasite load in canine tissue and the parasite load detected in sandflies five days after feeding on naturally infected dogs. A total of 23 dogs were examined and classified according to clinical manifestation of canine VL. Blood samples, splenic aspirate and skin biopsies were collected and parasite DNA was quantified by qPCR. Canine capacity to infect Lu. longipalpis with parasites was evaluated by xenodiagnosis and parasite loads were measured five days after feeding. No significant differences were observed with respect to canine clinical manifestation and the parasite loads detected in the blood, skin and spleen samples obtained from naturally infected dogs. Regardless of clinical canine visceral leishmaniasis (CVL) presentation and the degree of parasite burden, almost half of the dogs successfully infected sandflies with parasites, albeit to a low number of sandflies with correspondingly low parasite loads. Parasite loads in both canine blood and skin were shown to be positively correlated with the canine infectiousness to the sand fly vector, and positive correlations were also observed with respect to these tissues and the sand fly infection rate, as well as the parasite load detected in sandflies following xenodiagnosis. In conclusion, this indicates that parasite loads in both blood and skin can function as potentially reliable markers of canine capacity to infect sand fly vector.

Severe clinical presentation of visceral leishmaniasis in naturally infected dogs with disruption of the splenic white pulp

In this work, we investigated the association between the disruption of splenic lymphoid tissue and the severity of visceral leishmaniasis in dogs. Clinical and laboratory data from 206 dogs were reviewed. Spleen sections collected during the euthanasia of these animals were analyzed, and the splenic lymphoid tissue samples were classified as well organized (spleen type 1), slightly disorganized (spleen type 2), or moderately to extensively disorganized (spleen type 3). Of 199 dogs with evidence of Leishmania infection, 54 (27%) had spleen type 1, 99 (50%) had spleen type 2, and 46 (23%) had spleen type 3. The number of clinical signs associated with visceral leishmaniasis was significantly higher in the animals with evidence of Leishmania infection and spleen type 2 or 3 than in the animals with spleen type 1. Alopecia, anemia, dehydration, dermatitis, lymphadenopathy, and onychogryphosis were all more frequent among animals with evidence of Leishmania infection and spleen type 3 than among the dogs with evidence of Leishmania infection and spleen type 1. The association between the severity of canine visceral leishmaniasis and the disorganization of the splenic lymphoid tissue was even more evident in the group of animals with positive spleen culture. Conjunctivitis and ulceration were also more common in the animals with spleen type 3 than in the animals with spleen type 1. The serum levels (median, interquartile range) of albumin (1.8, 1.4–2.3 g/dL) and creatinine (0.7, 0.4–0.8 mg/dL) were significantly lower and the serum levels of aspartate aminotransferase were significantly higher (57, 39–95 U) in animals with spleen type 3 than in animals with spleen type 1 (2.8, 2.4–3.4 g/dL; 0.9, 0.7–1.2 mg/dL and 23, 20–32 U, respectively). Our data confirm the hypothesis that disruption of the splenic lymphoid tissue is associated with a more severe clinical presentation of canine visceral leishmaniasis.

Disseminated intravascular coagulation in a dog naturally infected by Leishmania (Leishmania) chagasi from Rio de Janeiro - Brazil

BACKGROUND

Disseminated intravascular coagulation (DIC) is an acquired disorder characterized by the activation of intravascular coagulation and excessive fibrin formation. It always occurs in association with other clinical conditions, including parasitic diseases. DIC has been described as a unusual complication in human and canine visceral leishmaniasis.

CASE PRESENTATION

DIC was found in a seven-year-old male mongrel dog naturally infected by Leishmania (Leishmania) chagasi. Haemostasis parameters demonstrated changes in primary and secondary haemostasis and fibrinolysis.

CONCLUSION

DIC is a unusual condition described in canine visceral leishmaniasis and it seems to be associated with several immunological and pathological mechanisms involved in the disease.

Directions for the diagnosis, clinical staging, treatment and prevention of canine leishmaniosis

Canine leishmaniosis (CanL) due to Leishmania infantum is a life threatening zoonotic disease with a wide distribution in four continents and importance also in non-endemic regions. The purpose of this report is to present a consensus of opinions on the diagnosis, treatment, prognosis and prevention of CanL in order to standardize the management of this infection. CanL is a disease in which infection does not equal clinical illness due to the high prevalence of subclinical infection among endemic canine populations. The most useful diagnostic approaches include serology by quantitative techniques and PCR. High antibody levels are associated with severe parasitism and disease and are diagnostic of clinical leishmaniosis. However, the presence of lower antibody levels is not necessarily indicative of disease and further work-up is necessary to confirm CanL by other diagnostic methods such as cytology, histopathology and PCR. We propose a system of four clinical stages, based on clinical signs, clinicopathological abnormalities and serological status. Suitable therapy and expected prognosis are presented for each of the stages. The combination of meglumine antimoniate and allopurinol constitutes the first line pharmaceutical protocol. However, although most dogs recover clinically after therapy, complete elimination of the parasite is usually not achieved and infected dogs may eventually relapse. Follow-up of treated dogs with blood counts, serum biochemistry, urinalysis, serology and PCR is essential for prevention of relapses. Protection against sand fly bites by topical insecticides is effective in reducing infection, and recent development of vaccines has indicated that prevention by vaccination is feasible.

Phenotypic features of circulating leucocytes as immunological markers for clinical status and bone marrow parasite density in dogs naturally infected by Leishmania chagasi

Canine visceral leishmaniasis (CVL) manifests itself as a broad clinical spectrum ranging from asymptomatic infection to patent severe disease. Despite relevant findings suggesting changes on lymphocytes subsets regarding the CVL clinical forms, it still remains to be elucidated whether a distinct phenotypic profile would be correlated with degree of tissue parasite density. Herein, we have assessed the correlation between the clinical status as well as the impact of bone marrow parasite density on the phenotypic profile of peripheral blood leucocytes in 40 Brazilian dogs naturally infected by Leishmania chagasi. Our major findings describe the lower frequency of B cells and monocytes as the most important markers of severe CVL. Our main statistically significant findings reveal that the CD8(+) T cell subset reflects most accurately both the clinical status and the overall bone marrow parasite density, as increased levels of CD8(+) lymphocytes appeared as the major phenotypic feature of asymptomatic disease and dogs bearing a low parasite load. Moreover, enhanced major histocompatibility complex (MHC)-II density as well as a higher CD45RB/CD45RA expression index seems to represent a key element to control disease morbidity. The association between clinical status, bone marrow parasitism and CD8(+) T cells re-emphasizes the role of the T cell-mediated immune response in the resistance mechanisms during ongoing CVL. Higher levels of circulating T lymphocytes (both CD4(+) and CD8(+) T cells) and lower MHC-II expression by peripheral blood lymphocytes seem to be the key for the effective immunological response, a hallmark of asymptomatic CVL.