Epidemiologia e clínica de cães portadores de dirofilariose em espaços urbanos de município do litoral do Paraná e aspectos da histologia de Culex quinquefasciatus Say, 1823 (Diptera, Culicidae)

Abstract

Abstract: Coastal areas located in the tropics are considered enzootic for Dirofilaria immitis, which has cosmopolitan distribution. The climate may be presented as a favorable condition, owing to the high temperatures and high pluviometric precipitation. These have direct and positive relation with the development of species of Diptera, considered potential vectors, as for instance Culex quinquefasciatus (Culicidae). This research aims at evaluating the prevalence of Dirofilaria immitis in two populations of dogs from an urban area, following the clinic evolution of the animals with dirofilariosis and discussing aspects of the internal morphology of Culex quinquefasciatus. The prevalence of Dirofilaria immitis was examined in two populations of dogs in Guaratuba, Paraná. One population consisted of wandering dogs captured by the Sanitary Vigilance Department of the City Hall. The other population consisted of domiciliary dogs from a district away from the downtown area and deficient in water supplying, water collecting and soil drainage infrastructure. Three methods have been simultaneously used to detect and identify microfilaries: the direct blood smear, the modified Knott’s test and the Snap® Canine Heartworm Antigen Test Kit (IDEXX Laboratories). The clinical evolution of the microfilaremic dogs was performed under different handling conditions: a) a dog under ideal conditions of feeding and shelter, and b) a dog in the care of its owners without appropriate feeding and shelter. The common procedures for both dogs were demonstration of microfilaries in blood films. The dog under ideal conditions was submitted to hemograma, skin and fecal parasitologic exams, radiographic and ultrasonographic thoracic exams, while only necropsy and histopathology were performed in the dog in the care of its owners. For Dirofilaria immitis it was detected a prevalence of 1% positive microfilaremic in the group of dogs captured and a prevalence of 4.2% positive microfilaremic in the group of domiciliary dogs, in which case the results indicated potential for dirofilariosis in the urban area analyzed. Concomitantly, through the direct blood smear and the modified Knott’s test, the prevalence of Dipetalonema sp. was detected, the values of which were 11.6% for the dogs captured and 5.6% for the domiciliary dogs. The clinical evolution of the disease in the microfilaremic dogs demonstrated the same progressive reduction of microfilaremy, although one of the dogs died for causes not related to Dirofilaria immitis. The microscopic study of the internal structures of Culex quinquefasciatus showed that this agent has three defense mechanisms against microfilaries directly related to the middle intestine: the oxihemoglobin crystal formation, the ingested blood coagulation and the peritrofic matrix secretion in a shorter period of time. The dirofilariosis in Guaratuba may be considered a zoonosis of reduced quantitative importance; nevertheless, en considered qualitatively, the positive cases indicate the need of monitoring the dogs and the population of potential vectors, once the area of major prevalence of the disease has some of the necessary elements for the maintenance of dirofilariosis, which are the environmental conditions for the development of the potential vector mosquito and the dogs which bear the disease.