Study of haemostatic disorders in experimentally induced leishmaniasis in Beagle dogs

Photocatalytic pathway toward degradation of environmental pharmaceutical pollutants: structure, kinetics and mechanism approach

During the last few years, the presence of pharmaceuticals in the aquatic environment, classified as so-called emerging contaminants, has attracted attention from the scientific community.

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.

Systemic alterations of bovine hemostasis due to Rhipicephalus (Boophilus) microplus infestation

The tick Rhipicephalus (Boophilus) microplus is a hematophagous ectoparasite that causes considerable economic losses to cattle breeding. Although R. microplus saliva contains several molecules that interfere with the blood coagulation process, so far the systemic alterations in the host hemostatic system have not been described. This study aims to determine if R. microplus infestation induces any disturbance to the host's hemostatic system. To address these questions, six calves were experimentally infested with 20,000 R. microplus larvae and their blood was collected before and 7, 14 and 21 days post-infestation. Collagen and ADP-induced platelet aggregation as well as coagulation (activated partial thromboplastin time and prothrombin time) decreased in infested bovines. Platelet blood count and fibrinogen increased during the course of infestation, probably as a compensatory response. These alterations may play a role in host health status, and show that the host cannot fully counteract the tick anti-hemostatic mechanisms.

A retrospective study of 61 cases of spontaneous canine epistaxis (1998 to 2001)

OBJECTIVES

To determine the prevalence and identify possible clinicopathologic indicators of the diseases associated with canine epistaxis.

METHODS

The medical records of 61 dogs with epistaxis were reviewed.

RESULTS

Systemic diseases, diagnosed in fifty-six dogs, included canine leishmaniasis in twenty-three dogs, canine monocytic ehrlichiosis in twenty-two, concurrent canine leishmaniasis and canine monocytic ehrlichiosis in six, rodenticide toxicity in two and primary immune-mediated thrombocytopenia, suspected oestrogen toxicity and systemic arterial hypertension in one dog each. Intranasal diseases were documented in the remaining five dogs, including transmissible venereal tumour in three dogs, and nasal adenocarcinoma and nasal aspergillosis in one dog each. Mucosal pallor and a generalised bleeding tendency were significantly more common among dogs with canine monocytic ehrlichiosis compared with those with canine leishmaniasis, whereas the opposite was true for peripheral lymphadenomegaly. Also, dogs with canine monocytic ehrlichiosis presented with pancytopenia more frequently compared with those with canine leishmaniasis; in the latter dogs, the median values of haematocrit, leucocyte and platelet counts and serum total protein concentrations were higher.

CLINICAL SIGNIFICANCE

Canine leishmaniasis and canine monocytic ehrlichiosis are the leading causes of canine epistaxis in Greece. Mucosal pallor, bleeding tendency and pancytopenia are more likely to be indicative of canine monocytic ehrlichiosis, as opposed to peripheral lymphadenomegaly and hyperproteinaemia in canine leishmaniasis.

The effects of prednisone on haemostasis in leishmaniotic dogs treated with meglumine antimoniate and allopurinol

Thirty dogs naturally infected with Leishmania infantum were studied in order to determine the effects of treatment on haemostatic function. The animals were divided randomly into two treatment groups: Group 1 received meglumine antimoniate and allopurinol; Group 2 dogs were given the same treatment plus prednisone. Ten healthy animals were used as untreated controls. Clinical examination and determination of platelet aggregation, coagulation factors and biochemical parameters were undertaken before treatment and after 15, 30 and 60 days. A significant improvement in platelet aggregation was detected after 60 days in Group 1, but only after 15 days in Group 2. In both treated groups, platelet aggregation was lower than in the control group at the end of the study. The results suggest that prednisone may be a useful tool in the treatment of haemostatic disorders during canine leishmaniosis. The potential benefits and risks due to the use of corticosteroids in the treatment of leishmaniosis are discussed.

Evaluation of adenosine 5'-diphosphate (ADP)- and collagen-induced platelet aggregation in canine leishmaniasis

Leishmania-infected dogs, which represent an important reservoir of infection in many parts of the world, frequently suffer from haematological disorders, including thrombocytopenia. In this study, the ability of platelets from healthy (control) dogs (n = 11) and from dogs with naturally acquired clinical leishmaniasis (n = 24) to aggregate in the presence of two different agonists (adenosine 5'-diphosphate [ADP] and collagen) was assayed. Haematological parameters examined consisted of the platelet count, prothrombin time, activated partial thromboplastin time (aPTT), fibrinogen concentration and D-dimer concentration. In dogs with leishmaniasis, a significant decrease in ADP- and collagen-induced platelet aggregation was observed. Compared with platelets from the control dogs, those from leishmania-infected dogs showed a higher sensitivity to collagen, as demonstrated by a reduction in platelet aggregation of up to 20.4%, and a significant (P < 0.0001) difference for all the doses tested. With ADP the reduction was up to 10.4%, the difference reaching a significant level of P < 0.0001 only at the maximum dose used. The nature of this response, which was not accompanied by any clinical signs of bleeding other than an increase in aPTT, emphasizes the role of platelets in the parasite-host cell interaction.

Adhesive properties of platelets from different animal species

The use of large animals (e.g., pig and sheep) in human medicine, and the need to develop new therapeutic strategies for domestic animal diseases related to platelet disorders, require better characterization of the physiology of animal platelets. In this study, the ability of platelets from buffaloes, horses, pigs and sheep to adhere to immobilized autologous fibrinogen was compared with that of human platelets. Blood samples were collected from the jugular vein of six healthy subjects of each species and platelet-rich plasma (PRP) was obtained by centrifugation. Platelets, isolated by further centrifugation of PRP, were washed by gel-filtration on Sepharose-2B, counted and added to the wells of 96-well plates pre-coated with autologous fibrinogen. After different times of incubation, non-adherent platelets were removed, and the number of adherent platelets was assessed by measuring endogenous acid phosphatase activity. Horse platelets showed the strongest ability to adhere to autologous immobilized fibrinogen, being 1.7-, 3.1- and 2.3-fold more active than human, buffalo and porcine platelets, respectively. Sheep platelets were unable to adhere to autologous immobilized fibrinogen. Platelet activation by adenosine 5-diphosphate (ADP) increased both human and animal platelet adhesive response. ADP-stimulated sheep platelets were able to adhere to autologous immobilized fibrinogen, albeit to a lesser extent than platelets from the other animal species. The observed interspecies variability in adhesive properties of platelets may reflect structural differences, or differences in the availability of the fibrinogen receptor (glycoprotein IIb/IIIa) on the platelet surface.

Species variability in platelet aggregation response to different agonists

Conflicting data on platelet function in animal species are reported in the literature. In this study, the response of buffalo, horse, pig and sheep platelets to different agonists was assessed. Blood samples were collected from the jugular vein of six healthy subjects of each species and platelet-rich plasma was obtained by centrifugation. Platelet aggregation responses to increasing doses of adenosine 5'-diphosphate (ADP), arachidonic acid, collagen, platelet activating factor (PAF) and ristocetin were measured by a turbidimetric method. Horse platelets were the most responsive to ADP, collagen and PAF, whereas sheep platelets were the most responsive to ristocetin. The response to arachidonic acid varied least between species. PAF was the most effective agonist, inducing a maximum aggregation response at a concentration of 1 micro M for platelets of each species. Conversely, concentrations of ristocetin higher than 1mg/ml induced a maximum aggregation response only with sheep and horse platelets. The different responses of platelets from the four animal species to various agonists may reflect either (1). structural differences (including composition of the platelet membrane and presence of specific agonist receptors), or (2). activation of distinct signalling pathways by the agonist.

Atypical forms of canine leishmaniosis

Canine leishmaniosis is a common disease in the Mediterranean area, but sporadic cases in dogs having travelled through endemic regions are also reported. The disease's evolution is usually chronic and symptoms are either non-specific (fever, weight loss, lethargy, enlarged lymph nodes), dermatological, renal or ocular. The purpose of this article is to review the literature and to describe our own experience of certain atypical forms of canine leishmaniosis. These include specific skin lesions, monoclonal gammopathy, renal failure (without any other signs), chronic colitis, haemostatic problems and disorders of the cardiovascular, respiratory and musculo-skeletal systems.

Evaluation of the potential causes of epistaxis in dogs with natural visceral leishmaniasis

Haemostasis was evaluated in 19 dogs with natural Leishmania infection, six of them with a history of epistaxis, and the results were compared with the results from 24 healthy dogs. In addition, the dogs' blood pressure was measured and biopsies were taken from the nasal mucosa. Buccal mucosa bleeding time was prolonged in the dogs with leishmaniasis (P < 0.002) and most significantly in those with epistaxis (P < 0.005). None of the Leishmania-infected dogs had thrombocytopenia, low levels of plasma von Willebrand factor antigen, a prolonged prothrombin time or activated partial thromboplastin time, a low plasma fibrinogen concentration or high serum fibrin degradation products. These results rule out defects of secondary haemostasis or disseminated intravascular coagulation as significant causes of epistaxis in non-complicated leishmaniasis. Histopathology of the nasal mucosa of 10 of the affected dogs, three of them with epistaxis, revealed ulcerative and inflammatory lesions in all of them.

Serological and parasitological follow-up in dogs experimentally infected with Leishmania infantum and treated with meglumine antimoniate

Six healthy beagle dogs were infected with Leishmania infantum (MCAN/ES/92/BCN-83/MON-1) by intravenous inoculation of 5 x 10(7) promastigotes and two others were used as controls. When animals showed clinical signs of disease at 29, 37, 41 and 45 weeks post-infection (p.i.), they were treated with meglumine antimoniate (20.4 mg Sb/kg/12 h) subcutaneously for two periods of 10 days each. Sera were tested periodically for Leishmania antibodies by Dot-ELISA, ELISA and Western blot (WB). Aspirates of popliteal lymph node (PLN), peripheral blood sample (PB) and healthy skin were cultured in NNN and Schneider's medium. PLNs were positive between 8 and 20 weeks p.i. and in one animal PB was positive 6 weeks p.i. Samples of healthy skin, obtained before treatment, were also positive. Dot-ELISA and ELISA detected specific antibodies at an early stage between 4 and 12 weeks p.i and surpassed the cut-off between 16-24 weeks p.i., while the WB was positive between 10-19 weeks p.i. The pattern of bands revealed during the first stages of infection was variable and only in two cases did the positivity start with bands of low molecular weight (12-14 kD); the number of bands increased until 15-24 weeks p.i., after which sera revealed a complete pattern of bands, from 12 to 85 kD, in the antigen of Leishmania. After treatment the clinical improvement of the animals was accompanied by a decrease in antibody titers (Dot-ELISA and ELISA) although the parasites remained in the PLN. This was reflected in the WB by a decrease in the intensity of bands, especially those in the region of 12-30 kD. A new increase in the antibody levels between 3 and 5 months after terminating the therapy was detected in the WB by a restoration of the initial complete pattern of bands.