Human dirofilariosis in Poland: the first cases of autochthonous infections with Dirofilaria repens

Abstract

Dirofilaria (Nochtiella) repens Railliet et Henry, 1911 (Nematoda: Onchocercidae) is a subcutaneous parasite of dogs and other carnivorous animals, with human acting as incidental hosts. D. repens occurs endemically in warm climates on various continents, in Europe mainly in Mediterranean countries. The aim of this study was to summarize information on human dirofilariosis in Poland, taking into consideration parasitological and epidemiological data. Between April 2009 – December 2011, in the parasitological laboratories of Medical University in Warsaw and the National Institute of Public Health/National Institute of Hygiene, fragments of affected human tissues and parasite specimens were examined microscopically. Molecular methods were used to confirm the results from eight microscopic investigations. A literature review to summarize all data on dirofilarial infections in humans in Poland was conducted. In these investigations, autochthonous dirofilariosis was found in humans for the first time in Poland. During the last 3 years, 12 new cases of human D. repens dirofilariosis were recognized. Since 2007, a total of 18 D. repens infection have been found in humans in Poland. Parasitic changes were located in various parts of the body, in the form of subcutaneous nodules containing single nematodes surrounded by granulation tissue (15 cases). In 3 cases, a subconjuctival localization was found. Seventeen of the 18 described cases were noted in central Poland where dirofilariosis occured in dogs. In this area, autochtonous infection was identified in 3 women who had never left Poland in their lives; the others were probably infected outside the country while staying in endemic regions. Data on human and canine infection collected from central Poland during the last 5 years indicates that Dirofilaria repens has been introduced into our country, and that the infection is successfully spreading, with the border of the endemic area currently on 52°N, 21°E. To control the epidemiological situation it is necessary to identify D. repens hosts within local mosquito populations, and to monitor dogs. Because of the increasing number of cases of human infections, whether introduced or local, physicians should take dirofilariosis into consideration in differential diagnosis of skin and eye diseases.