Investigation of canine visceral leishmaniasis in a non-endemic area in Brazil and the comparison of serological and molecular diagnostic tests

Abstract INTRODUCTION: Visceral leishmaniasis (VL) is an important zoonosis in Brazil. Previous identification of parasitized dogs can also help prevent the disease in humans, even in non-endemic areas of the country. The Brazilian Ministry of Health recommends diagnosis in dogs using a DPP® (rapid test) as a screening test and an immunoenzymatic assay (ELISA) as a confirmatory test (DPP®+ELISA), and culling infected dogs as a legal control measure. However, the accuracy of these serological tests has been questioned. METHODS: VL in dogs was investigated in a non-endemic area of the São Paulo state for three consecutive years, and the performances of different diagnostic tests were compared. RESULTS: A total of 331 dog samples were collected in 2015, 373 in 2016, and 347 in 2017. The seroprevalence by DPP®+ELISA was 3.3, 3.2, and 0.3%, respectively, and by indirect immunofluorescence assay (IFA), it was 3.0, 5.6, and 5.5%, respectively. ELISA confirmed 18.4% of DPP® positive samples. The concordance between the IFA and DPP® was 83.9%. The concordance between IFA and DPP®+ELISA was 92.9%. A molecular diagnostic test (PCR) was performed in 63.2% of the seropositive samples, all of which were negative. CONCLUSIONS: In non-endemic areas, diagnostic tests in dogs should be carefully evaluated to avoid false results.

Seroprevalence and incidence of Leptospira spp. in domestic dogs in the Southeast region of São Paulo State, Brazil / Soroprevalência e incidência de Leptospira spp. em cães domésticos na região sudeste do estado de São Paulo, Brasil

Leptospirosis is a zoonotic disease caused by Leptospira and domestic dogs can act as host of some serovars. In order to analyze the transmission dynamics in a dog population, with and without immunization, a longitudinal study was carried out with a focus to evaluate antibody response and to identify serovars. Blood samples were collected in three consecutive years (2015 to 2017) from 331, 373 and 347 dogs respectively. The dog seroprevalence in each year was 11%, 7% and 14%, respectively, and the incidence in 2016 was 5% and in 2017, 14%. The most frequent serovars were Cynopteri and Butembo in 2015, Cynopteri, Butembo and Hardjoprajitno in 2016, and Canicola and Butembo in 2017. Dogs can play a role as sentinel animals and hosts of Leptospira serovars. The percentage of seropositive dogs due to vaccination was higher than the previous years without immunization and lower than in previous years for other serovars, which we interpret as evidence for the importance of immunization. These parameters associated with active canine population control are important for prevention and control of leptospirosis not only in dogs but alsoto inhibit the transmission between dogs and humans.(AU)

A leptospirose é uma zoonose causada pelo agente etiológico Leptospira. Cães domésticos atuam como hospedeiro de diversos sorovares deste agente. Com intuito de analisar a dinâmica da leptospirose em uma população canina, com e sem imunização, um estudo longitudinal foi realizado avaliando a resposta sorológica destes animais e identificando seus sorovares. Foram coletadas amostras de 331, 373 e 347 cães em três anos consecutivos (2015 a 2017). As soroprevalências foram de 11%, 7% e 14%, respectivamente, e a incidência em 2016 foi de 5% e em 2017 de 14%. Os sorovares mais frequentes foram Cynopteri e Butembo em 2015, Cynopteri, Butembo e Hardjoprajitno em 2016, e Canicola e Butembo em 2017. Estes cães estão atuando como bio-indicadores da presença de Leptospira na região do estudo, incluindo sorovares zoonóticos, e contribuindo com a sua manutenção no ambiente. A soropositividade para sorovares protegidos pela vacina foi mais alta do que nos anos anteriores à imunização, enquanto para os sorovares não protegidos pela vacina diminuiu, demonstrando a importância da imunização para essa população de cães. Medidas de prevenção e controle para a leptospirose, como imunização e controle populacional canino, são recomendadas no local para inibir a transmissão do agente entre as populações de cães e humanos envolvidas.(AU)

Seroprevalence and incidence of Toxoplasma gondii and Neospora caninum infection in naturally exposed domestic dogs from a rural area of São Paulo state, Brazil / Soroprevalência e incidência de infecção por Toxoplasma gondii e Neospora caninum em cães domésticos naturalmente expostos em uma área rural no estado de São Paulo, Brasil

Abstract Dogs are hosts of the protozoans Toxoplasma gondii, which causes an important public health disease, and Neospora caninum. Studies that have evaluated toxoplasmosis and neosporosis for prolonged periods in dog populations are rare. We analyzed infection by both parasites in a domestic dog population over three consecutive years in São Paulo state, Brazil. In the 1st, 2nd and 3rd years of collection, 181, 193 and 172 domiciles were visited, and blood samples of 331, 371 and 348 dogs were collected for antibody serology, respectively. The seroprevalence of T. gondii in each year was 27.2%, 22.5% and 43.9%, respectively, and that of N. caninum was 7.8%, 4.8% and 6.8%, respectively. The incidence rates for T. gondii in the 2nd and 3rd collections were 13.2% and 30.0%, and those for N. caninum were 3.3% and 4.4%, respectively. Positive and negative serological conversions for both agents occurred at high frequencies during the study period. This study reveals the canine population's serological profile and demonstrates the constant exposure of dogs to the investigated pathogens, indicating the need for prevention and control measures in the region.

Resumo Os cães são hospedeiros dos protozoários Toxoplasma gondii, que causam uma importante doença para a saúde pública, e Neospora caninum. Estudos que avaliam a toxoplasmose e a neosporose por períodos prolongados em populações caninas são raros. Foi analisada a infecção por esses dois parasitas em uma população de cães domésticos e domiciliados por três anos consecutivos, no Estado de São Paulo, Brasil. Nos 1º, 2º e 3º anos de coletas, 181, 193 e 172 domicílios foram visitados, nos quais foram coletadas amostras de sangue de 331, 371 e 348 cães para sorologia, respectivamente. A soroprevalência de T. gondii em cada ano foi de 27,2%, 22,5% e 43,9%, respectivamente; e a de N. caninum foi de 7,8%, 4,8% e 6,8%, respectivamente. As taxas de incidência para T. gondii, nas 2ª e 3ª coletas, foram de 13,2% e 30,0%, respectivamente; e para N. caninum, 3,3% e 4,4%, respectivamente. As conversões sorológicas positivas e negativas para ambos os agentes ocorreram em alta frequência durante o período analisado. Este estudo revela o perfil sorológico da população canina e demonstra sua constante exposição aos patógenos investigados, o que requer medidas de prevenção e controle na região.