Prevalência e técnicas de diagnóstico de Dirofilaria immitis em cães no Sertão Paraibano.

Abstract

Dirofilaria immitis is a zoonotic parasite that mainly affects domestic dogs, and wild canids and occasionally other mammals such as domestic cats and humans. This dissertation consists of two chapters in the form of scientific articles. In chapter 1, the objective was to determine the prevalence and factors associated with infection by D. immitis in dogs in the city of Sousa, semiarid of Paraíba. 320 dogs were selected and evaluated, of which 160 were domiciled and 160 stray, from 32 neighborhoods in the city of Sousa. Clinical examination, blood collection and epidemiological data of each animal were performed. For microfilariae research, three methods were performed: capillary blood smear (ESC), peripheral (ESP) and modified Knotttest (KM), associated with the morphometric diagnosis of the microfilariae. There was a prevalence of 17.5% (56/320) positive animals for D. immitis, with 71.43% (40/56) wandering and 28.57% (16/56) domiciled. Of the 32 neighborhoods evaluated, 24 were found positive dogs, with Angelim and Doutor Zezé, the neighborhoods with the highest percentage 1.56% (5/320) each. The categories of cardiac disorders (Odds ratio 6,231 [CI 1,539-25,236]) and stray dogs (Odds ratio 2,463 [CI 1,281-4,735]) were risk factors for infection. Of the 56 positive animals, 28 showed positivity in the three tests, and another 28 showed variation between methods and / or between made slides. It was considered that the region of the Sertão Paraibano has a significant prevalence of infection by D. immitis, being necessary to establish forms of control and prophylaxis, to reduce the risks of transmission to animals, as well as to humans. In Chapter 2, the objective was to evaluate and compare the efficiency and performance of parasitological, serological and molecular tests in the diagnosis of D. immitis in the Sertão Paraibano, Northeast Brazil. Whole blood and serum from 140 dogs from the municipality of Sousa were used. Three microscopic parasitological techniques (PMS) were used: ESC, ESP and KM, associated with the morphometric diagnosis of microfilariae. For the detection of D. immitis antigens, the rapid immunochromatographic test (TRI) of ALERE Dirofilariose AG Teste kit® was used, and direct polymerase chain reaction (PCR) as a molecular method. To evaluate the tests, PCR was considered the gold standard, with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) values being calculated. To verify the agreement of the tests, the Kappa test was performed (p≤0.05). Of the 140 samples analyzed, 33.6% (48/140) presented microfilariae, antigen and / or parasitic DNA. Of this total of samples, 23.6% (33/140) were positive in the ESC; 25.7% (36/140) in the ESP; 29.3% (41/140) in the KM; 30% (42/140) in the TRI and 28.6% (40/100) in the PCR. All methods showed almost perfect agreement with PCR, high sensitivity (0.8 to 0.95), specificity (0.94 to 0.99), values established with VPP (0.8571 to 0.9722) and VPN (0.9519 to 0.7979). All techniques were highly effective with almost perfect agreement with PCR. ESC and ESP were the techniques with less sensitivity and greater specificity. KM was considered the most sensitive test and IRT was the choice for hidden infections. The PCR showed high sensitivity and specificity in comparison to the other tests, and better identification of D. immitis.