Vaccine effectiveness and use of collar impregnated with insecticide for reducing incidence of Leishmania infection in dogs in an endemic region for visceral leishmaniasis, in Brazil.

Although a national programme for control of visceral leishmaniosis (VL) is being run in Brazil, the disease continues to spread. This programme is essentially based on culling infected dogs from endemic regions. Thus, there is an urgent need to develop other control measures against VL to deter its advance. Here, a subunit vaccine, a recombinant vaccine, an insecticide-impregnated collar and the associations between these measures were evaluated for reducing the incidence of Leishmania infection in dogs. This was through a cohort study conducted in an endemic region of Brazil, considering the incidence and time of total exposure over a period of 1 year. The incidence of VL was estimated by means of serological and molecular diagnostic tests, 180 and 360 days after the application of the control measures. The estimates of the effectiveness (EF) were not significant in any cohort. The EF of the subunit vaccine, the recombinant vaccine and the collar were 26.4%, 32.8% and 57.7% and the upper limit of the 95% confidence interval for EF were 63.7%, 67.9% and 82.5%, respectively. In conclusion, under the conditions of this study, none of the immunogens for VL control was sufficiently effective to protect dogs against infection. On the other hand, use of collars impregnated with insecticide seems to constitute a method with better prognosis, corroborating other studies in this field.

Serological and molecular diagnostic tests for canine visceral leishmaniasis in Brazilian endemic area: one out of five seronegative dogs are infected.

Euthanasia of infected dogs is one of the measures adopted in Brazil to control visceral leishmaniasis (VL) in endemic areas. To detect infected dogs, animals are screened with the rapid test DPP® Visceral Canine Leishmaniasis for detection of antibodies against K26/K39 fusion antigens of amastigotes (DPP). DPP-positives are confirmed with an immunoenzymatic assay probing soluble antigens of promastigotes (ELISA), while DPP-negatives are considered free of infection. Here, 975 dogs from an endemic region were surveyed by using DPP, ELISA and real-time PCR (qPCR) for the diagnosis of VL. When DPP-negative dogs were tested by qPCR applied in blood and lymph node aspirates, 174/887 (19·6%) were positive in at least one sample. In a second sampling using 115 cases, the DPP-negative dogs were tested by qPCR in blood, lymph node and conjunctival swab samples, and 36/79 (45·6%) were positive in at least one sample. Low-to-moderate pairwise agreement was observed between all possible pair of tests. In conclusion, the official diagnosis of VL in dogs in Brazilian endemic areas failed to accuse an expressive number of infected animals and the impact of the low accuracy of serological tests in the success of euthanasia-based measure for VL control need to be assessed.

Evaluation of an Immunochromatographic Test to the Diagnosis of Canine Brucellosis Caused by Brucella canis.

This study evaluated the performance of an immunochromatographic test (ICT) for the diagnosis of canine brucellosis caused by Brucella canis, comparing its results with that of the rapid slide agglutination test with and without the use of 2-mercaptoethanol and the agar gel immunodiffusion test (AGID). The microbiological culture, PCR and clinical examination were used as reference. According to the results obtained in clinical examination, blood culture, culture of semen and vaginal swab and PCR in blood, semen and vaginal swab, a total of 102 dogs were divided into three groups: B. canis-infected dogs (Group 1), B. canis-non-infected dogs (Group 2) and dogs with suspected brucellosis (Group 3). The diagnostic sensitivity of RSAT, 2ME-RSAT, AGID and ICT in Group 1 was, respectively, 75%, 37.5%, 27.8% and 89.58%. The diagnostic specificity of RSAT, 2ME-RSAT, AGID and ICT in Group 2 was, respectively, 91%, 100%, 100%, and 100%. In dogs with suspected brucellosis, 9.67% were RSAT positive, none was positive by 2ME-RSAT, 3.22% were AGID positive and 6.45% were ICT positive. The main drawback concerning canine brucellosis diagnosis is the lack of a highly sensitive serological assay to be used as a screening test to the rapid identification of infected animals. The ICT showed a high diagnostic specificity and a diagnostic sensitivity value greater than that observed in the RSAT, 2ME-RSAT and AGID. However, 10.41% of infected dogs had negative results by ICT. These dogs were positive by microbiological culture and/or PCR, indicating active infection and consequently a higher potential of spreading Brucella. Although rapid and simple to perform, the ICT lacked sensitivity to be used as a screening test.

Detection of Leishmania (L.) chagasi in canine skin.

Canine visceral leishmaniasis (CVL) is caused by a protozoa parasite of the specie Leishmania (L.) chagasi endemic for humans and dogs in many regions of Brazil. The purpose of the present study was the detection of (L.) chagasi in canine skin tissues from three different groups of clinical signs: asymptomatic, oligosymptomatic and polysymptomatic Leishmania-infected dogs. Lesional or non-lesional skin tissue samples from 34 naturally infected dogs were obtained and processed by histochemistry (HE) and immunohistochemistry (IMHC) for direct parasitological examination and the results were compared with a polymerase chain reaction (PCR) method. IMHC and HE methods detected intact Leishmania-amastigote parasites in lesional and no lesional skin, particularly in asymptomatic and oligosymptomatic dogs. 50% of skin samples collected from asymptomatic and 21.4% from oligosymptomatic dogs had parasites in their skins even though with mild inflammatory reaction or without any macroscopic dermatological alterations. On the other hand, 100% of polysymptomatic dogs showed several forms of clinical dermatological alterations and 91.7% had intact amastigotes with parasite load ranging from mild to intense. By PCR, DNA of Leishmania spp. was detected in 97.8% skin samples regardless clinical status of the dogs or IMHC/HE test results. PCR on skin was a sensitive procedure for CVL diagnosis, but direct observation of intact parasite in skin biopsies, particularly by IMHC, may be also considered to support the diagnosis.