Dirofilaria repens is a zoonotic mosquito-borne filarioid that parasitizes in the subcutaneous tissues of carnivores, that has been incriminated in the great majority of human dirofilariasis cases reported throughout the Old World. From the Republic of Uzbekistan, recent data showed that this parasite is endemic in domestic and wild carnivores. In contrast, information regarding human infection is scarce and mostly outdated, with a single case report being published during the last decades. The present paper reports a case of recurrent autochthonous infection with D. repens in a patient living in the rural area of the Sirdaryo Region of Uzbekistan and having no international travel history. The first diagnosis was in 2019, when the patient presented with what was suspected to be a tumour of the left breast. Three years later, in 2022, she presented for a consultation after experiencing redness, occasional swelling and persistent itching in the umbilical region of the abdomen. The ultrasound indicated the presence of a living, motile nematode. Following anthelmintic therapy, the parasite was surgically removed and identified as a female D. repens. The present report highlights the possibility of human re-infection with D. repens and further underlines the necessity of raising public awareness and implementing of solid control strategies in carnivores.

The vectorial role of blood-sucking arthropods, other than mosquitoes, has been explored for Dirofilaria immitis and Dirofilaria repens which are filarioids of increasing interest due to their zoonotic potential. Given the expansion of canine heartworm infection in southern Europe due to D. immitis and the report of the infection in Linosa Island (Sicily, Italy), we investigated and focused on the potential involvement of Culicoides spp. in Dirofilaria spp. transmission as well as the blood-meal source in Dirofilaria spp. molecularly positive biting midges. Out of 1791 specimens collected 1773 were morphologically and molecularly identified as Culicoides paolae and 18 as Culicoides obsoletus complex. Of the 1596 females, 4 (0.26%) parous C. paolae tested positive for D. immitis and D. repens (i.e. 2 Culicoides specimens for each filarial species), of which D. immitis-positive samples fed on both humans and dogs and D. repens-positive samples fed only on humans. The detection of D. immitis and D. repens DNA in Culicoides midges suggests their potential involvement in the epidemiology of the filarial nematodes, which may be of medical and veterinary importance in hyper-endemic areas. Findings of this study shed new light on the epidemiology of Dirofilaria spp. infections indicating that further investigations are needed.

The prevalence of vector-associated parasitic infections is high in central-southern Italy. The deltaic coastal plain of the Volturno River has been suspected, by veterinary practitioners, to have a high accidental incidence of Dirofilaria repens. Thus, the goal of this study was to evaluate the prevalence of dirofilariasis and other coinfections frequently described in dogs living in the Volturno area. Blood samples of 100 clinical asymptomatic dogs were examined using a Knott's technique and polymerase chain reaction in order to identify microfilariae. Other vector-borne coinfections were also investigated using ELISA kits. The results were analysed using statistical and Geographic Information System (GIS) software. Microfilariae of D. repens were detected in 10% of the dogs surveyed, with a presence of antibodies against Ehrlichia canis (4/10) and Dirofilaria immitis (1/10). Such high incidence should be considered in light of the zoonotic potential for D. repens and the support for more regular use of repellents to prevent the spread of this disease. The GIS analyses indicated that the study area provides suitable conditions to sustain populations of mosquito vectors and D. repens parasites throughout much of the year.

Human subcutaneous dirofilariosis has several clinical presentations. Many cases present as subcutaneous nodules, as a consequence of a local inflammatory reaction that encapsulates and destroys the worms. In addition, there are cases in which migrating worms located in the ocular area remain unencapsulated. In the present work, the levels of two pro-inflammatory eicosanoids, thromboxane B2 (TxB2) and leukotriene B4 (LTB4) are analysed by commercial Enzime-Linked immunosorbent assay (ELISA) in serum samples from 43 individuals, 28 diagnosed as having subcutaneous dirofilariasis presenting a subcutaneous nodule, five diagnosed as having dirofilariasis, in which the worms remained unencapsulated in the periphery of the eye, and ten healthy individuals living in a non-endemic area, used as controls. The worms were surgically removed, identifying Dirofilaria repens as the causative agent in all cases, by Polymerase Chain Reaction (PCR). Individuals with nodules showed significantly higher levels of TxB2 and LTB4 than healthy controls, whereas significant differences in LTB4 levels were observed between individuals with unencapsulated worms and healthy controls. It is speculated that the absence of LTB4 may contribute to the fact that worms remain unencapsulated as a part of immune evasion mechanisms.

On the basis of known DNA sequences of Dirofilaria repens and D. immitis we designed specific primers for the amplification by Polymerase Chain Reaction (PCR) of the DNA from the two species. The PCR-based identification was found to be unambiguous and allowed specific diagnosis of microfilariae in blood samples, of developing larvae in the mosquito vector and of immature adults in bioptic material, overcoming the serious constraints of the morphological separation of these filarial parasites at the pre-adult stages. The technique was found to be very sensitive and applicable to samples stored either dry or in various preservation media, with the exception of formalin. The reliable identification of D. repens and D. immitis from bioptic material is expected to greatly enhance the chances of detecting human infections and to further clarify the role of the two parasites as pathogens of man. The possibility of routine identification of developing larvae in the vector will substantially improve the perspectives for epidemiological investigations, particularly in Southern European regions, such as Italy, where the two nematode species are largely sympatric.