Trakia Journal of Sciences, No 4, pp 388-395, 2020 Copyright © 2020 Trakia University Available online at: http://www.uni-sz.bg ISSN 1313-3551 (online) doi:10.15547/tjs.2020.04.013 Review HUMAN DIROFILARIASIS: CURRENT SITUATION AND POSSIBILITIES FOR DIAGNOSIS B. Chakarova1, M. Mitev2* 1Department of Hygiene, Epidemiology, Microbiology, Parasitology and Infectious Diseases, Faculty of Medicine, Trakia University, Stara Zagora, Bulgaria 2Department of Medical Physics, Biophysics, Roentgenology and Radiology, Faculty of Medicine, Department of Diagnostic Imaging, University Hospital ‘St. Kirkovich’, Trakia University, Stara Zagora, Bulgaria ABSTRACT Dirofilariasis in humans is a rarely diagnosed vector-borne zoonotic helminthic invasion. It is caused from filarial nematodes genus Dirofilaria & Railliet Henry, 1911 (Onchocercidae, Nematoda). Usually, the life cycle of the parasite takes place between mosquitoes (Culicidae) and carnivores. The human is an accidental host for the dirofilaria wherefore microfilariae in his blood circulation are almost always absent. The pathology of dirofilariasis results from the accidental localization of immature worms in the human body. Dirofilaria immitis caused heart and pulmonary dirofilariasis, but Dirofilaria repens, D. tenuis, and others can are found in different parts of the human body. The spread and Dirofilaria- invasive rates аrе undergone significant modifications affected by global climate change. Surgical extraction of the parasite in humans usually has a therapeutic effect, after which an etiological diagnosis is possible. The aim of the study is to review the current situation of human dirofilariasis in clinical and epidemiological aspects and possibilities for diagnosis. Key words: human dirofilariasis, clinical and epidemiological aspects dirofilariasis, diagnostic methods INTRODUCTION diagnosed as parasites in humans: D. Immitis Dirofilariasis in humans (heartworm disease in (Leidy, 1856), D. repens (Railliet & Henry dogs) is a rarely diagnosed vector-borne 1911) and D. tenuis (Chandler, 1942). zoonotic helminthic invasion. It is caused from Autochthonous D. repens infections have been filarial nematodes genus Dirofilaria & Railliet found in dogs in most European countries, Henry, 1911 (Onchocercidae, Nematoda). The from Portugal to Russia (1). The main first observation of D. repens-invasion in reservoir for D. repens in many countries in humans was probably reported in 1566 by the world such as the United States, Southern Amato Lusitano, a Portuguese physician. He Europe, Australia and Japan is the dog. (3). describes a worm nestled in the inner corner of The life cycle of the parasite takes place an eye in a 3-year-old girl (1). In 1626 Birago between mosquitoes, which are intermediate incorrectly described the larval forms of hosts, and domestic and wild carnivores (such roundworm specimens as Dioctophyme renale. as foxes, wolves, raccoons) acting as definitive In 1856 the genus was renamed as Filaria by hosts. Adult nematodes give birth to Leidy and in 1911 as Dirofilaria by microfilariae, which are transmitted by blood- Railliet&Henry (2). In the scientific literature, sucking through intermediate hosts - over 70 about 27 species of the genus Dirofilaria have potential species of mosquitoes of the family been reported. Only three species of them are Culicidae (2, 4-12). D. immitis caused heart ___________________________ and pulmonary dirofilariasis, but D. repens, D. *Correspondence to: Mitko Mitev, Department of tenuis, and others can are found in Diagnostic Imaging, University Hospital "St. subcutaneous nodules, or freely migrating (L3) Kirkovich", Trakia University – Stara Zagora, 6000 filaria in the subcojuctiva, in the large vessels Mobile: +359 88 770 6079, E-mail: of the mesentery, peritoneum, the spermatic [email protected] 388 Trakia Journal of Sciences, Vol. 18, № 4, 2020 CHAKAROVA B., et al. cord in the lungs and liver (13, 14). In Bulgaria reported for the first time as a parasite in only Dirofilaria repens is now found in humans by Pistey (4). Over 70 potential humans - the people are sporadically infected. species of mosquitoes of the genera Anopheles, The dirofilariаsis are distributed mainly in Aedes, Culex and Coquillettidia, are vectots for regions with warm climates and nowadays, the Dirofilaria sp. In Europe, the most powerful infection raises public health concerns in a vector for the transmission of Dirofilaria sp. number of countries (6, 15). D. repens- (according to the literature) is Culex pipiens. invasion in humans is accidental and the The spread and Dirofilaria-invasive rates аrе diagnosis of the disease creates problems for undergone significant modifications affected public health in a number of countries (6, 15, by global climate change. Dirofilariasis is 16). prevalent mainly in areas with warm climates - at an average daily temperature above 14.80C The pathology of dirofilariasis results from the (below it the development of Dirofilaria stops) accidental localization of immature worms in for 30 days (life expectancy of the vector) and the human body (8). The worms do not reach a time interval of 130 days with increasing day adulthood in human wherefore microfilariae in (24). In the second half of the last century, his blood circulation are almost always absent, more than 800 cases have been described in which makes the etiological diagnosis about 30 countries, with the age of the patients extremely difficult. The distribution and varying from 4 months to 100 years. People of Dirofilaria-invasive rates аrе undergone working age are most often affected - around significant modifications affected by global 40 years of age (3, 6, 16). In North and South climate change. Preliminary clinical diagnoses America, Australia, and parts of Africa, Japan, of patients with dirofilariasis mostly vary and and Oceania, only D. immitis is widespread the final diagnosis is staged after the surgical among dogs. In Northern Europe, China, Saudi removal of the granuloma or the adult filaria. Arabia and South Africa - only the species D. In most cases, the definitive diagnosis is repens, and in Southern and Central Europe, obtained after the worm removal. Surgical Russia and the former southern Soviet extraction of the parasite in humans usually republics, as well as in India are found as D. has a therapeutic effect, after which an immitis and D. repens. (3, 16, 25). etiological diagnosis is possible. Vutchev et al. (2003 2004); Daskalova et al. The aim of the study is to review current (2006); Harizanov et al. (2010, 2014); situation of human dirofilariasis in clinical and Chakarova et al. (2013, 2014); Neichev et al. epidemiological aspects and possibilities for (2014); Kaftandjiev et al. (2016); Velev et al. diagnosis. (2019-a,b,c) are reported D. repens-invasion with varying location in humans in Bulgaria Current trends in the epidemiological (26-37). Harizanov et al. (2010), Harizanov et characteristics and clinical manifestations of al. (2014) presented a retrospective analysis of dirofilariasis the reported 47 cases of human dirofilariasis, From the three species of Dirofilaria, found as for the period 1973 - 2011. In 78.47% of cases, parasites in humans, in Europe, D. immitis has the subcutaneous invasion was observed, been reported from Southern Europe; D. followed by subconjunctival (21.27%) and repens - mainly from the countries of genital (4.25%) infection. The authors reported Mediterranean region and Eastern Europe a dominance of the upper body localization (among dogs in Italy - 66%, France - 22%, (80.85%) over the lower body (19.14%). A Greece - 8%, Spain - 4%, etc.), (17). feature of ophthalmic dirofilariasis, according Georgieva et al. (1992), Georgieva et al. to the analysis made, was the subconjunctival (2001), Kirkova et al. (2011); Radev et al. location of the parasite and that it was not (2016); Iliev et al. (2017) explore wild covered by the host response. The authors also animals, stray dogs and cats, from some found and reported of cases of localization of regions in Bulgaria and establish among them the parasite in the vitreous, lens and ocular invasion with D. immitis and D. repens (18- space, etc. (29, 30). For 10 years before 2003, 22). Where heartworm disease is widespread in Vutchev et al. (2003), Vutchev et al. (2004) dog populations, there is a high risk for human described 12 cases with subcutaneous infection, which creates serious public health localization of the parasite, and for 20 years - problems in countries with growing 22 cases (26, 27). Daskalova et al. (2006) populations of stray dogs (3, 23). D. tenuis was reported a patient with cutaneous left lower Trakia Journal of Sciences, Vol. 18, № 4, 2020 389 CHAKAROVA B., et al. eyelid dirofilariasis (28). Chakarova et al. their accompanying pets, suggests the need for (2013), Chakarova et al. (2014) and better diagnosis and registration of cases (4, 6, Kaftandjiev et al. (2016) described a rare 8). localization of human dirofilariasis - in the epididymis (31, 32, 34). Velev et al. (2019a) Possibilities for diagnosis dirofilariasis described epididymal dirofilariasis in a child as According to many authors, including from the first case report from Bulgaria (35). Bulgaria, due to the nature of the disease and Harizanov et al. (2010) presented 9 cases of D. the small number of cases, diagnosis is repens infection in only one year - 2009 in difficult to be defined. The most common Bulgaria (29). Chakarova et al. (2013), diagnoses are neoplasms, lymphadenitis