Parasitological, serological and molecular diagnosis of Dirofilaria immitis in dogs in Northeastern Brazil.

Dirofilaria immitis is a zoonotic filarid that mainly affects the domestic dog, causing a generally fatal chronic disease, known as heart worm disease. In addition to dogs, the parasite can affect wild canids, cats, and humans. Due to its importance to One Health, detection of parasitism by D. immitis in dogs can help the adoption of control measures that aim to reduce the occurrence of parasitosis in animals and humans. The detection of D. immitis is based on the use of parasitological, serological, and molecular methods, which vary in sensitivity and specificity. Therefore, the objective was to evaluate and compare the efficiency and performance of parasitological, serological, and molecular tests in the detection of D. immitis in dogs in Northeastern Brazil. Whole blood and serum from 140 dogs from the municipality of Sousa were used, varying between males and females; aged one to 17 years; pure and mixed breeds; domiciled and stray. Three microscopic parasitological techniques (MPT) were used: capillary blood smear (CBS), peripheral (PBS) and modified Knott test (MK) associated with the morphometric diagnosis of the microfilariae. For the detection of D. immitis antigens, a rapid immunochromatographic test (RIT) (ALERE Dirofilariose AG Teste kit®, Seogu-dong, Korea) was used, and polymerase chain reaction (PCR) as a molecular method. To evaluate the tests, PCR was considered the gold standard, and sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) values were calculated. To verify the agreement of the tests, the Kappa test was performed (p ≤ 0.05). From the 140 analyzed samples, 33.6% (48/140) presented microfilariae, antigen and/or parasitic DNA. 23.6% (33/140) were positive in the CBS; 25.7% (36/140) in the PBS; 29.3% (41/140) in the MK; 30% (42/140) in the RIT and 28.6% (40/140) in the PCR. All methods showed almost perfect agreement with PCR, high sensitivity (0.8-0.95), specificity (0.94-0.99), and values established with VPP (0.8571-0.9722) and VPN (0.9519-0.9797). The CBS and PBS showed less sensitivity and greater specificity. MK presented the highest sensitivity and RIT was the choice for hidden infections. Considering the occurrence of D. immitis in dogs in a non-coastal region of Northeastern Brazil, an epidemiological approach is recommended to identify risk factors for this zoonotic parasitosis.

Prevalence and factors associated with Dirofilaria immitis infection in dogs in Sertão Paraibano, Northeast Brazil / Prevalência e fatores associados à infecção por Dirofilaria immitis em cães no Sertão Paraibano, Nordeste do Brasil

Dirofilaria immitis is a heart and large vessel parasite that mainly affects domestic dogs and has shown a re-emerging zoonosis in recent years. The objective of this study was to determine the prevalence, associated factors, and geographic areas of D. immitis in dogs in the city of Sousa, Paraíba, Northeast Brazil. A total of 320 dogs were selected and evaluated, 160 domiciled and 160 wandering, from the 32 districts of the city. Clinical examination, blood collection, and epidemiological data retrieval were performed for each animal. The sanitation conditions of the environment were visually observed at the time of evaluation. Three methods were used to investigate the morphometric diagnosis of microfilariae: capillary blood smear (ESC), peripheral blood smear (ESP), and modified Knott test. The data were subjected to univariate and multivariate statistics for the observation of risk factors and qualitative assessment of the examinations. Of the 17.5% (56/320) of animals testing positive for D. immitis, 25% (40/160) were wandering and 10% (16/160) were domiciled dogs. Positive dogs were found in 24 of the 32 neighborhoods evaluated, with Angelim and Doutor Zezé having the highest percentages of 1.56% (5/320) each. Only the categories of cardiac alterations (OR 6.231 [1,539-25,236]) and stray dogs (OR 2.463 [1,281-4,735]) demonstrated potential risk factors for infection. Of the 56 positive animals, 28 were positive in the three tests, and another 28 showed variance between methods and/or between prepared slides. No other filaridae were observed. The city of Sousa is considered to have a significant prevalence of infection by D. immitis, and forms of control and prophylaxis are required to reduce the risks of transmission to animals, as well as to humans.

Dirofilaria immitis é um parasito de coração e de grandes vasos que acomete principalmente cães domésticos, também causador de uma zoonose reemergente nos últimos anos. O objetivo deste trabalho foi determinar a prevalência, fatores associados e áreas geográficas de D. immitis em cães na cidade de Sousa, Paraíba, Nordeste do Brasil. Para isso, foram selecionados e avaliados 320 cães, sendo 160 domiciliados e 160 errantes, provenientes dos 32 bairros da cidade. Foi realizado o exame clínico, coleta de sangue e dados epidemiológicos de cada animal. O ambiente foi observado visualmente quanto as condições de saneamento no momento de avaliação. Para pesquisa de microfilárias, foram realizados três métodos: esfregaço sanguíneo capilar (ESC), periférico (ESP) e teste de Knott-modificado, associado ao diagnóstico morfométrico das microfilárias. Os dados foram submetidos a estatísticas uni e multivariadas para observação de fatores de risco e avaliação qualitativa dos exames. Obteve-se prevalência de 17,5% (56/320) de animais positivos para D. immitis, sendo 25% (40/160) errantes e 10% (16/160) domiciliados. Dos 32 bairros avaliados, em 24 foram encontrados cães positivos, sendo Angelim e Doutor Zezé, os bairros com maior percentual 1,56% (5/320) cada. Somente as categorias de alterações cardíacas (OR 6,231 [1.539-25.236]) e cães errantes (OR 2,463 [1.281-4.735]) demonstraram potencial fator de risco para infecção. Dos 56 animais positivos, 28 apresentaram positividade nos três testes, e outros 28 demonstraram variância entre métodos e/ou entre lâminas confeccionadas. Não foram observados outros filarídeos. Considerou-se que a cidade de Sousa apresenta prevalência significativa de infecção por D. immitis, sendo necessário estabelecer formas de controle e profilaxia, para reduzir os riscos da transmissão para animais, como também para humanos.