Experimental infection of dogs with Leishmania and saliva as a model to study Canine Visceral Leishmaniasis.

BACKGROUND: Canine Visceral Leishmaniasis (CVL) is a zoonotic disease caused by Leishmania infantum, transmitted by the bite of Lutzomyia longipalpis sand flies. Dogs are the main domestic reservoir of the parasite. The establishment of an experimental model that partially reproduces natural infection in dogs is very important to test vaccine candidates, mainly regarding those that use salivary proteins from the vector and new therapeutical approaches. METHODOLOGY/PRINCIPAL FINDINGS: In this report, we describe an experimental infection in dogs, using intradermal injection of Leishmania infantum plus salivary gland homogenate (SGH) of Lutzomyia longipalpis. Thirty-five dogs were infected with 1×10(7) parasites combined with five pairs of Lutzomyia longipalpis salivary glands and followed for 450 days after infection and clinical, immunological and parasitological parameters were evaluated. Two hundred and ten days after infection we observed that 31,4% of dogs did not display detectable levels of anti-Leishmania antibodies but all presented different numbers of parasites in the lymph nodes. Animals with a positive xenodiagnosis had at least 3,35×10(5) parasites in their lymph nodes. An increase of IFN-γ and IL-10 levels was detected during infection. Twenty two percent of dogs developed symptoms of CVL during infection. CONCLUSION: The infection model described here shows some degree of similarity when compared with naturally infected dogs opening new perspectives for the study of CVL using an experimental model that employs the combination of parasites and sand fly saliva both present during natural transmission.

Treatment of canine visceral leishmaniasis by the vaccine Leish-111f+MPL-SE.

Immunotherapy of canine visceral leishmaniasis (CVL) may provide an alternative to both marginally effective chemotherapy and undesired euthanasia of infected dogs and could have a great impact not only on animal welfare, but also on control of human disease. Therefore, we examined the potential immunotherapeutic efficacy of the subunit vaccine Leish-111f+MPL-SE, which has undergone rigorous preclinical testing and been demonstrated safe in human clinical trials. Two separate trials were performed in Salvador, Brazil, to evaluate the vaccine for therapeutic efficacy against CVL caused by natural infection: an Open Trial and a Blinded Trial. In the Open Trial 59 dogs with clinically active CVL were sequentially allocated to four groups: group 1 received Leish-111f+MPL-SE; group 2 was treated with Glucantime; group 3 received a combination of the vaccine and Glucantime; and group 4 was given no treatment. At the 6-month assessment, the 13 non-treated dogs had either died or showed no clinical improvement. In contrast, most dogs in groups 1-3 showed initial improvement (100%, 80%, and 92%, respectively). Upon evaluation for a mean of 36 months after therapy, the following cure rates were observed: 75% for group 1 dogs (exact 95% confidence interval [CI] 43-95%), 64% for group 2 dogs (exact 95% CI 31-89%), and 50% for group 3 dogs (exact 95% CI 19-81%). Therapeutic efficacy of the Leish-111f+MPL-SE vaccine was reconfirmed in a subsequent Blinded Trial. The vaccine was effective for mild cases of CVL and was compromised in dogs with severe disease. Although further studies are required to understand mechanisms of action, the Leish-111f+MPL-SE vaccine is a promising tool to control VL in both dogs and humans.

Distinct antigen recognition pattern during zoonotic visceral leishmaniasis in humans and dogs.

Leishmania infantum is a causative agent of endemic zoonotic visceral leishmaniasis (VL) in regions of South America and the Mediterranean. Dogs are the major reservoirs for L. infantum in these regions, and control of disease in dogs could have a significant impact on human disease. Although dogs share many symptoms of VL with humans as a result of L. infantum infection, they also show some unique clinical manifestations, which are often a combination of visceral and cutaneous leishmaniasis, suggesting different mechanisms of disease development in dogs and humans. Here, we compare antibody responses of dogs and humans with VL to various defined leishmanial antigens. Parasite lysate and K39, the two most commonly used antigens for serodiagnosis of VL, detected the highest levels of antibodies in both humans and dogs with VL, whereas the recognition patterns of these antigens were distinct between the hosts. Among other defined antigens tested, LmSTI1 and CPB detected higher levels of antibodies in dogs and humans, respectively. These results indicate there is a difference between humans and dogs in antigen recognition patterns during VL. We infer that different strategies may need to be used in development of vaccines and diagnostics for humans and for dogs. In addition, we show a correlation between antibody titers to several antigens and severity of clinical symptoms during canine VL.

Can spleen aspirations be safely used for the parasitological diagnosis of canine visceral leishmaniosis? A study on assymptomatic and polysymptomatic animals.

The purpose of this study was to evaluate the safety of spleen aspiration as a sampling technique for the parasitological detection by culture and microscopy of Leishmania (chagasi) infantum. Two hundred and nine domiciled dogs from an endemic area for visceral leishmaniasis in Bahia State, Brazil, were studied. Most dogs (87%) were seropositive for anti-L. chagasi antibodies by ELISA. Clinical signs of disease were recorded and the animals monitored during and after spleen puncture in order to detect possible complications associated with the procedure. From a total of 257 splenic punctures in the 209 animals, only three minor events occurred, with no significant consequence for the animals and no association with risk factors. Leishmania was isolated from 149/180 (83%) seropositive dogs, and from 6/26 (23%) seronegative animals. The procedure did not cause adverse side effects or unnecessary suffering and confirmed the diagnosis in a large percentage of dogs. We conclude that spleen aspiration can be considered an effective and safe procedure for the definitive diagnosis of canine visceral leishmaniosis.

Comparison between splenic and lymph node aspirations as sampling methods for the parasitological detection of Leishmania chagasi infection in dogs.

The sensitivities of spleen and lymph node cultures for the diagnosis of canine visceral leishmaniasis were compared in 64 anti-Leishmania antibody positive dogs from an endemic area in Brazil. The sensitivity of spleen cultures for Leishmania detection was 97.9%; in lymph node cultures it was 25%. Positive spleen culture was more frequent (p = 0.048, Fisher's exact probability test) in symptomatic (28 out of 33 animals) than in asymptomatic animals (19 out of 31 animals). These results support the use of spleen instead of lymph node aspiration as the choice method for the parasitological diagnosis of the infection.

Comparison between splenic and lymph node aspirations as sampling methods for the parasitological detection of Leishmania chagasi infection in dogs

The sensitivities of spleen and lymph node cultures for the diagnosis of canine visceral leishmaniasis were compared in 64 anti-Leishmania antibody positive dogs from an endemic area in Brazil. The sensitivity of spleen cultures for Leishmania detection was 97.9 percent; in lymph node cultures it was 25 percent. Positive spleen culture was more frequent (p = 0.048, Fisher's exact probability test) in symptomatic (28 out of 33 animals) than in asymptomatic animals (19 out of 31 animals). These results support the use of spleen instead of lymph node aspiration as the choice method for the parasitological diagnosis of the infection.