Seroepidemiological Study of Canine and Human Dirofilariasis in the Endemic Region of Northern Serbia

Dirofilaria sp. and Blood Meal Analysis in Mosquitoes Collected in Vojvodina and Mačva, and the First Report of Setaria tundra (Issaitshikoff & Rajewskaya, 1928) in Serbia

Dirofilaria immitis and D. repens are the two most widespread and important species of mosquito-borne nematodes, posing a significant threat to veterinary health and particularly affecting canines and felines. While D. immitis causes cardiopulmonary dirofilariasis, D. repens causes subcutaneous infections in dogs and other carnivores. Despite the extensive knowledge on these parasites, little is known about their natural vectors in Serbia. The parasite Setaria tundra, known to infect deer, has not yet been detected in Serbia but has been documented in neighboring countries. Thus, the aim of this study was to (i) further map out Dirofilaria sp. hotspots in the Vojvodina Province and detect S. tundra for the first time, (ii) detect positive mosquito species that can provide insights into how the nematodes spread in Serbia, and (iii) analyze the blood-fed female mosquitoes of species found to be infected, in order to identify the potential source of parasite infection. A total of 2902 female mosquitoes were collected across 73 locations during 2021 and 2022. Molecular biology methods, based on conventional PCR, were used to analyze non-blood-fed (2521 specimens) and blood-fed (381 specimens) female mosquitos, in order to detect filarial nematode presence and identify blood-meal sources, respectively. When the parasite genome was detected, the amplicon (cox1 gene, 650 bp fragment) was sent for Sanger sequencing, further confirming the presence of nematodes and species assignation. D. immitis was detected in three Culex pipiens mosquitoes collected in Zrenjanin (August 2021) and Glogonj and Svetozar Miletić (both in July 2021). Additionally, Setaria tundra was detected in Aedes vexans collected in Iđoš (mid-August 2021) and Aedes caspius, which was collected in Mali Iđoš (end of July 2021). This work identifies two new locations where D. immitis occurs in Vojvodina, and is the first report of S. tundra in Serbian territory. Blood-meal analysis provided insights into the preferences of mosquitoes that were positive for Dirofilaria sp. and S. tundra.

Prediction and validation of potential transmission risk of Dirofilaria spp. infection in Serbia and its projection to 2080

Animal and human dirofilariosis is a vector-borne zoonotic disease, being one of the most important diseases in Europe. In Serbia, there are extensive studies reporting the presence of Dirofilaria immitis and D. repens, mainly in the north of the country, where the human population is concentrated and where there is a presence of culicid mosquitoes that transmit the disease. Ecological niche modeling (ENM) has proven to be a very good tool to predict the appearance of parasitosis in very diverse areas, with distant orography and climatologies at a local, continental, and global level. Taking these factors into account, the objective of this study was to develop an environmental model for Serbia that reflects the suitability of the ecological niche for the risk of infection with Dirofilaria spp. with which the predictive power of existing studies is improved. A wide set of variables related to the transmission of the parasite were used. The potential number of generations of D. immitis and the ecological niche modeling method (ENM) were used to estimate the potential distribution of suitable habitats for Culex pipiens. The highest probability of infection risk was located in the north of the country, and the lowest in the southern regions, where there is more orographic relief and less human activity. The model was corroborated with the location of D. immitis-infected dogs, with 89.28% of the country having a high probability of infection. In addition, it was observed that the percentage of territory with optimal habitat for Culex spp. will increase significantly between now and 2080. This new model can be used as a tool in the control and prevention of heartworm disease in Serbia, due to its high predictive power, and will serve to alert veterinary and health personnel of the presence of the disease in the animal and human population, respectively.

Microfilaremic Dirofilaria repens Infection in Patient from Serbia

We report a case of Dirofilaria repens infection causing microfilaremia in a patient from Serbia. Serum samples tested positive for D. repens IgG by ELISA. Our findings and those of others suggest the parasite's progressive adaptation to humans. Clinicians should be aware that microfilaremia can develop during Dirofilaria spp. infections.

What Has Happened to Heartworm Disease in Europe in the Last 10 Years?

Heartworm disease caused by Dirofilaria immitis is a vector-borne disease that affects canids and felids, both domestic and wild, throughout the world. It is a chronic disease which causes vascular damage in pulmonary arteries, and in advanced stages, the presence of pulmonary hypertension and right-sided congestive heart failure can be evidenced. Moreover, pulmonary thromboembolism is caused by the death of the worms, which can be lethal for the infected animal. Furthermore, it is the causative agent of human pulmonary dirofilariosis, being a zoonotic disease. The aim of this review was to update the current epidemiological situation of heartworm in Europe in dogs, cats, wild animals, and vectors insects, and to analyse the factors that may have contributed to the continuous spread of the disease in the last decade (2012–2021). In Europe, the disease has extended to eastern countries, being currently endemic in countries where previously only isolated or imported cases were reported. Furthermore, its prevalence has continued to increase in southern countries, traditionally endemic. This distribution trends and changes are influenced by several factors which are discussed in this review, such as the climate changes, presence of vectors in new areas, the appearance of new competent vector species in the continent, increased movement of pets that travelled to or originated from endemic countries, the urbanisation of rural areas leading to the formation of so-called “heat islands”, or the creation of extensive areas of irrigated crops. The continuous expansion of D. immitis must be monitored, and measures adapted to the situation of each country must be carried out for adequate control.

Dirofilaria immitis: Genotyping Randomly Selected European Clinical Samples and USA Laboratory Isolates with Molecular Markers Associated with Macrocyclic Lactone Susceptibility and Resistance

Dirofilaria immitis is a parasitic nematode and causes dirofilariosis, a potentially fatal pulmonary infection which primarily infects canids. Dirofilariosis infections are controlled via prophylactic macrocyclic lactone (ML) regimens. Recent evidence has confirmed the development of ML-resistant isolates in the USA, which are genetically distinct from wildtype populations. Single nucleotide polymorphisms (SNP) associated with ML-resistant phenotypes were clinically validated in USA populations. In this study, 3 USA laboratory-maintained isolates (Berkeley, Georgia II, and WildCat) and 11 randomly selected European clinical samples from 7 hosts were analyzed. The samples tested were fresh microfilaria (mf) in blood or adult worms preserved in ethanol. The samples underwent MiSeq sequencing of the top 9 SNP associated with ML resistance. The results provide the first genotypic analysis of the three USA laboratory-maintained isolates and any European samples. The European clinical samples show no genomic evidence of ML resistance based on the 9 SNP. The early adoption of genotyping of clinical D. immitis samples could provide an early indication of the potential development of ML resistance and aid to distinguish clinical cases of heartworm infection due to ML resistance from those due to a lack compliance with the recommended treatments, as has been seen in North America.

Heartworm Disease in Jackals: Unusual Location of Dirofilaria immitis

PURPOSE

The knowledge of heartworm disease in free ranging wild canid populations is limited. As it is very difficult to monitor this disease in live animals, sporadic findings are mostly obtained by examining culled individuals of game species.

METHODS

As a part of a broader study on jackal (Canis aureus) ecology in Serbia, the necropsy of legally hunted animals was performed in 2020.

RESULTS

Two cases of heartworm infection with unusually located adult heartworms were diagnosed. The first case is an adult female jackal harvested in the vicinity of the capital city of Belgrade. Three adult specimens of Dirofilaria immitis were found in the right atrium of the heart, and nine adult specimens were located at an atypical site, in the vena cava caudalis. Very similar, the second case was in an adult female jackal harvested in the vicinity of Bački Monoštor. In this case, six adult specimens of D. immitis were found in the right atrium of the heart and six more adult specimens in the vena cava caudalis.

CONCLUSION

Although this nematode generally resides in the pulmonary arteries and the right ventricle of the heart, rare findings in other large blood vessels can occur. To the best of our knowledge, these are the first and only two confirmed cases of adult D. immitis found in vena cava caudalis in jackals in Europe.

Occupational risk of cutaneous larva migrans: A case report and a systematic literature review

Cutaneous larva migrans (CLM) is a parasitic zoonosis of warm tropical and subtropical areas, although autochthonous cases have been increasingly reported in Western European countries. Data on the prevalence of CLM as an occupational disease in workers exposed to potentially contaminated soil or in close contact with dogs and cats are scant. Herein, we report an autochthonous case of CLM in a dog breeder from southern Italy (Apulia region), along with a systematic literature review describing the risk of CLM infection, mainly according to job categories. The patient was referred to the dermatology unit presenting a serpiginous lesion on his hand, raising the suspected CLM diagnosis. In non-endemic areas, CLM might represent a challenge for physicians in terms of diagnosis, treatment, and prevention, particularly in workplaces. The multidisciplinary approach in the diagnosis of CLM with the involvement of different scientific competences (i.e., dermatologists, veterinarians, and occupational physicians) may contribute to further assess the distribution of human CLM and associated risk factors, toward reducing the risk for the infection.

Serological Survey of Canine Vector-Borne Infections in North-Center Spain

Various factors are currently causing an increase in vector-borne parasitic diseases at a global scale; among them, some stand out, such as climatic disturbances derived from global change, the increase in movements of reservoir animals, or changes in land made by human activity. In the European continent, there have been an increasing number of epidemiological studies focused on the detection of these diseases, especially in dogs. In Spain, there are few epidemiological studies focused on the evaluation of the biotic and abiotic factors that may influence the distribution, such as climatic zones, orography, or presence of water reservoirs. The aim of this study was to analyze the prevalence and distribution of several canine vector-borne diseases caused by Dirofilaria immitis, Leishmania infantum, Anaplasma platys, and Ehrlichia canis in the autonomous community of Castilla y León, the largest region of the Iberian Peninsula, providing a geospatial approach based on a geographic information system (GIS) analysis. Blood from a total of 1,475 domestic dogs from the nine provinces of Castilla y León were analyzed. Also, a GIS analysis of the sample locations was carried out, taking into account the most important predictor variables. The prevalence in dogs infected by D. immitis was 7.19%, and the seroprevalence by L. infantum was 4.61 and 1.56% for A. platys and E. canis. Most of the infected animals were located in areas with stagnant water, irrigated agriculture, or riverbanks, always close to forest and woodland vegetation. These results indicate that dogs living in Castilla y León should take prophylactic measures to avoid infections.

Canine leishmaniasis in Balkan - A review of occurrence and epidemiology

Canine leishmaniasis is a parasitic zoonotic infection of dogs caused by the Leishmania spp. parasites. In Europe, canine leishmaniasis is among the most important vector-borne parasitic diseases of dogs, with majority of data originating from countries of southwestern Europe. With its scarce and outdated records, the Balkan region presents the "blank space" in the European map of canine leishmaniasis knowledge. Numerous records obtained during the past decade and a half indicate the emergence of autochthonous canine leishmaniasis in new settings all across Balkan, a significant increase in the numbers of infected dogs in previously endemic areas, and northward spread of the disease. As the majority of canine leishmaniasis data from Balkan countries are several decades old and generally written in native Balkan languages, hence not available to the broader area of scientists, comprehensive search of scientific literature published from 1934 to January 2021 was conducted in order to provide a better perspective to the past and current canine leishmaniasis situation in Balkan. This review provides exhaustive information on all leishmaniasis records in dogs, wild animals and cats, available from 10 countries of the Balkan region. It identifies dogs as the main disease reservoirs and highlights the importance of wild animals, and potentially cats, as disease reservoirs, which is of great public and veterinary health concern. Additionally, certain shortcomings in canine leishmaniasis research, management, surveillance and control were identified.

Identity of Microfilariae Circulating in Dogs from Western and South-Western Romania in the Last Decade

Dirofilaria infections in dogs are recognized as widespread mosquito-borne diseases with zoonotic potential, that are caused by the filarioid nematode (Onchocercidae) species Dirofilaria immitis and Dirofilaria repens. The long-term survey conducted in western and south-western Romania was undertaken in order to provide valuable data on the occurrence of Dirofilaria infections in dogs. Blood samples from 1088 dogs, originating from 73 localities of 11 western and south-western counties in Romania, were collected and examined using the modified Knott test. Subsequently, all of the microscopically positive samples were subjected to molecular analysis for confirmation. Altogether, the data obtained showed the percentage of dogs with circulating microfilariae to be 21.42% (233/1088) of dogs tested in the investigated region. The identified species, in cases of monoinfections, were D. immitis, D. repens, and Acanthocheilonema reconditum in 106 (9.74%) samples, 102 (9.38%) samples, and 1 (0.09%) sample, respectively. Twenty-four (2.21%) samples were simultaneously positive for D. immitis and D. repens. There was no association (p > 0.05) between infection status and breed; however, sex and lifestyle were positively associated (p < 0.05) with the percentage of dogs with circulating microfilariae and might be regarded as risk factors for infection. The results of the present investigation indicate potential zoonotic risks for humans living in the screened area and support the imperative to increase awareness among both veterinarians and physicians, regarding the continuous spread of these zoonotic filariae.

An epidemiological survey of Dirofilaria spp. and Acanthocheilonema spp. in dogs from the Republic of Moldova

Background

During the last decades, filarial infections caused by Dirofilaria spp. have spread rapidly within dog populations of several European countries. Increasing scientific interest in filariasis, and the availability of new diagnostic tools, has led to improved knowledge of the biology, morphology, and epidemiology of different species of filarial worms. However, data are still scarce for a number of countries, including the Republic of Moldova. Thus, we assessed the epidemiological status of canine filariasis in the Republic of Moldova to address part of this knowledge gap.

Methods

A total of 120 blood samples were collected between June 2018 and July 2019 from dogs originating from the cities of Cahul and Chişinău. The samples were examined microscopically, and multiplex polymerase chain reaction was performed to evaluate filarioid species diversity.

Results

Microscopic examination revealed that 12 dogs (10.0%) were positive for circulating microfilariae. The molecular test showed that one dog was positive for Acanthocheilonema reconditum (0.8%), one for Dirofilariaimmitis (0.8%), six for Dirofilariarepens (5.0%), and four (3.3%) harboured a co-infection with D. immitis and D. repens. Prevalence was significantly higher in dogs aged ≥ 2 years.

Conclusions

The epidemiological survey presented here for the Republic of Moldova confirmed the presence D. immitis, D. repens and A. reconditum in dogs that had not received any heartworm preventive.

Graphical abstract