The Republic of Moldova is one of the countries were few data is available on the epidemiology of Dirofilaria spp. and A. reconditum. The lack of diagnostic tools, the misdiagnosis, and the low awareness of medical doctors and veterinarians are considered as the main factors leading to this gap (15). In a molecular study from 2016, of 347 pool of female mosquitos analysed, 109 and 30 tested positive for D. repens and D. repens, respectively. The geographic distribution of the positive sample sites and temperature analyses allowed the authors to conclude that the entire country has favourable climatic conditions for the transmission of Dirofilaria spp. (15). The results of our study confirm this hypothesis. Although both D. immitis and D. repens have been diagnosed in the human population from the Republic of Moldova, most of the available information is represented by several case reports, where the nematodes were identified based on microscopic examination only. Only 5 cases of human dirofilariasis have been reported until 2016 (15). However, from the provided data, it is not clear whether the cases were autochthonous or imported (15). The only extensive study on the human population from the Republic of Moldova was performed in 2018, when 263 serum samples were screened for exposure to Dirofilaria spp. One sample was positive for D. repens antigens, 36 were positive for anti-D. immitis IgG, while 3 samples reacted for both antigens of D. immitis and D. repens (14). Only one study reported the presence of D. immitis in the local canine populations. A total number of 13 shepherd dogs originating from 2 counties, Ialoveni and Criuleni, located in the Central part of Moldova, were evaluated for the presence of various parasite species by necropsy. Three of the examined dogs were infected with D. immitis (18). The identification method of the parasites is not mentioned. It is not clear whether the positive dogs originated from the same county or not. Infection(s) with D. repens and/or A. reconditum has not been reported so far in the Republic of Moldova. However, in Ukraine that is bordering the Republic of Moldova to the East, North and South, and Romania, the western neighbour state, many infections with these pathogens have been reportedin human and animal populations. In Ukraine, dirofilariasis caused by D. repens in dogs was first reported in 1904, while human infection in 1927 (19). Between 1997 and 2013, 1465 cases of human infections with D. repens were confirmed. The incidence rate of dirofilaria infection ranged between 0.07–3.71 per 100000 persons in the geographical areas neighbouring the Republic of Moldova. The presence of the pathogen in all the oblasts of Ukraine as well as the high incidence registered in many regions, allowed the authors to conclude that in Ukraine, dirofilariasis due to D. repens, is an emergent zoonosis (19). In 2015, Rossi et al. demonstrated the implication of both D. immitis and D. repens in ocular and subcutaneous pathology in humans from Ukraine (20). In Romania, although sporadic infections with D. immitis in dogs were reported since the beginning of the 1900s’, more recent studies revealed prevalence values ranging from 23.07–38% by use of various diagnostic methods (21, 22). In 2014, both D. immitis and D. repens were categorized as endemic species in areas from Southern and South-eastern Romania. In the same study, a first extensive epidemiological overview of the prevalence and distribution of A. reconditum was provided the first time in this country (23). Analysing the epidemiological situation in Europe, with emphasis on the two neighbouring countries, Romania and Ukraine, as well as the presence of favourable climatic conditions for the transmission of Dirofilaria spp., it is highly probable that the limited reports of these pathogens in the Republic of Moldova is the result of the lack in targeted epidemiological studies.
During the last decades, the infection with Dirofilaria spp. in dogs has spread form the traditionally endemic regions from Italy, Spain, France, (24) towards central, eastern and north-eastern European countries such as Germany (25), Austria (26), Czechia (27), Poland (28), Romania (22), etc. Interestingly, more recently, a new trend of the distribution of these pathogens has been observed: in areas of high endemicity from the Western European countries, the prevalence of dirofilariasis has decreased in the last few years. This aspect was attributed to the increased awareness on the diseases and therefore the acceptance and widespread use of the prevention measures (29). Contrary, in non-endemic regions or where the parasites have not been reported (Eastern European countries and not only), recent data has shown the first cases and/or an increase in the prevalence of these diseases. The spreading of the pathogens was likely facilitated by the climate changes, the lack of experience of veterinary practitioners on the diagnosis and treatment of these diseases, the decreased awareness on the diseases of both medical personnel and dog owners, and the high number of stray dogs (29). Austria, a country that reported the presence of autochthonous D. repens for the first time in 2012 (30), was announcing in 2018 that the infections with D. immitis and D. repens tripled their number, and today it is wondering if they are facing a pre-endemic status (31). A similar pattern for associated infections with 2 pathogens was registered in Romania and Ukraine.
Dogs are the main reservoir for the human and other mammals’ infection (5). Monitorization of the canine population would be one important step for the prevention programmes and could c decrease the zoonotic risk. The need for more solid information and development of monitoring programmes and epidemiological studies on dirofilariasis and other zoonotic vector-borne pathogens in dogs from the Republic of Moldova has been highlighted before (14, 15). Our study is the first one to provide data that could be a starting point for future more extensive epidemiologic research. More data on the prevalence and geographical distribution in dogs, humans and vectors would allow a better understanding of the circulation of these pathogens in the Republic of Moldova. Our results should raise the awareness of veterinarians and physicians. The circulation of dogs between different countries, together with or heading to their owners is more and more common. In the light of the current study, dogs originating from the Republic of Moldova should be screened for Dirofilaria spp. and Acanthocheilonema spp.. Nevertheless, for the dogs entering this country, preventive measures should be taken by veterinarians and dog owners.
The role of the stray dogs in the circulation of these filarial worms and the high risk posed for the human health by this category of animals, has been previously demonstrated (32). Although origin was not identified as a risk factor in our study, possibly due to the low sample size, these dogs could act as an important source for other carnivores and human contamination. The responsible authorities and institutions should gather their efforts on decreasing the stray dog population, controlling and applying preventing measures to limit dirofilarial infections spread. To the best of our knowledge, our findings on A. reconditum and D. repens represent the first report of these pathogens in the canine population from the Republic of Moldova.