Tick-borne Diseases (Borreliosis, Anaplasmosis, Babesiosis) in German and Austrian Dogs: Status quo and Review of Distribution, Transmission, Clinical Findings, Diagnostics and Prophylaxis

Molecular and Serological Detection of Anaplasma phagocytophilum in Dogs from Germany (2008-2020)

Anaplasma phagocytophilum is an obligate intracellular bacterium that causes granulocytic anaplasmosis in domestic animals, wildlife, and humans and is primarily transmitted by ticks of the Ixodes persulcatus complex. This retrospective study aims to determine the percentages of dogs that tested positive for A. phagocytophilum in Germany. It included the results of direct (polymerase chain reaction [PCR]) and indirect (immunofluorescence antibody test [IFAT], antibody-enzyme-linked immunosorbent assay [ELISA]) detection methods performed in the laboratory LABOKLIN on canine samples provided by German veterinarians from 2008 to 2020. Out of a total of 27,368 dogs tested by PCR, 1332 (4.9%) tested positive, while 24,720 (27.4%) of the 90,376 dogs tested by IFAT/ELISA had positive serology. High rates of positive PCR results were observed in months with known peaks in vector activity, showing that the dynamics of A. phagocytophilum infections in dogs in Germany are consistent with vector activity. In dogs with a positive PCR result, peaks in serology could be observed four weeks after initial testing. Male and senior dogs had higher rates of positive serology. A possible impact of environmental factors such as changes in climate should be investigated further. Overall, the upward trend in positive test results over the years indicates that canine granulocytic anaplasmosis will continue to become increasingly important for veterinary medicine.

Haematological Alterations Associated with Selected Vector-Borne Infections and Exposure in Dogs from Pereira, Risaralda, Colombia

Infections due to Ehrlichia, Anaplasma, Dirofilaria, Mycoplasma, Babesia and Hepatozoon continue to be highly prevalent in dogs, especially in tropical and subtropical areas, where vectors of many of them are present. However, many clinical aspects of dogs have not been characterized in detail, including assessing the haematological alterations associated with them, particularly in Colombia and Latin America. A group of 100 dogs with Ehrlichia, Anaplasma, Dirofilaria, Mycoplasma, Babesia and Hepatozoon infections/exposure were assessed by blood smear serology (SNAP4DX) and PCR in Pereira, Colombia. We performed blood counts to evaluate anaemia, leukopenia/leukocytosis, neutropenia, neutrophilia, lymphopenia/lymphocytosis, monocytosis, eosinophilia, and thrombocytopenia, among other alterations. Bivariate analyses were performed on Stata®14, with significant p < 0.05. From the total, 85% presented ≥1 infection (past or present), 66% with coinfections (≥2 pathogens) (Ehrlichia 75%), and 89% presented clinical alterations. A total of 100% showed anaemia, 70% thrombocytopenia, 61% monocytosis, and 47% neutropenia, among other alterations. Additionally, 11% presented pancytopenia and 59% bicytopenia. The median platelet count was lower in infected dogs (126,000 cells/μL) versus non-infected (221,000 cells/μL) (p = 0.003). Thrombocytopenia was higher among infected dogs (75%) versus non-infected (40%) (p = 0.006), with a 91% positive predictive value for infection. Median neutrophil count was lower in infected dogs (6591 cells/μL) versus non-infected (8804 cells/μL) (p = 0.013). Lymphocytosis occurred only among those infected (27%) (p = 0.022). Leukopenia was only observed among infected dogs (13%). Pancytopenia was only observed among infected dogs. Ehrlichiosis and other hematic infections have led to a significant burden of haematological alterations on infected dogs, including pancytopenia in a tenth of them, most with thrombocytopenia and all anemic.

Exotic bloodborne parasites and dogs imported from Africa

The number of dogs legally imported to the UK from Africa is on the rise, and so too, therefore, is the risk of co-importing currently exotic parasites. Here, Rebecca Dobinson and Ian Wright report the results of a small study carried out in Sierra Leone, in which visibly healthy dogs were screened for the presence of several bloodborne parasites.

Seropositivity of main vector-borne pathogens in dogs across Europe

BACKGROUND

Canine vector-borne disease (CVBD) has been an area of increasing interest in Europe over the last few decades, and there have been changes in the prevalence and distribution of many of these diseases. Monitoring CVBD infections in Europe is often done by individual countries, but aggregated data for the European countries are helpful to understand the distribution of CVBDs.

METHODS

We used an extensive retrospective database of results from point-of-care rapid enzyme-linked immunosorbent assay (ELISA) tests on dogs across Europe to identify distribution and seropositivity in animals tested for selected CVBDs (Anaplasma spp., Ehrlichia spp., Borrelia burgdorferi, Leishmania spp., and Dirofilaria immitis) from 2016 through 2020. Geographic distribution of positive tests and relative percent positive values were mapped by the Nomenclature of Territorial Units for Statistics classification for regions with sufficient test results for reporting.

RESULTS

A total of 404,617 samples corresponding to 1,134,648 canine results were available from dogs tested in 35 countries over the 5-year study period. Over this period the number of test results per year increased whereas test positivity decreased. Leishmania spp. had the largest increase in total test results from 25,000 results in 2016 to over 60,000 results in 2020. Test positivity for Leishmania spp. fell from 13.9% in 2016 to 9.4% in 2020. Test positivity fell for Anaplasma spp. (7.3 to 5.3%), Ehrlichia spp. (4.3 to 3.4%), and Borrelia burgdorferi (3.3 to 2.4%). Dirofilaria immitis test positivity trended down with a high of 2.7% in 2016 and low of 1.8% in 2018. Leishmania spp. test positivity was highest in endemic areas and in several non-endemic countries with low numbers of test results. Co-positivity rates were significantly higher than expected for all pathogen test positive pairs except for Ehrlichia spp. with Borrelia burgdorferi and D. immitis with Borrelia burgdorferi.

CONCLUSIONS

This study represents the largest data set on CVBD seropositivity in Europe to date. The increase in the number of test results and decreasing test positivity over the study period may reflect changes in testing behavior and increased screening of healthy animals. The Europe-wide mapping of CVBD provides expected test positivity that can help inform veterinarians' decisions on screening and improve prevention and identification of these important, sometimes zoonotic, diseases.

Potential Mechanisms of Transmission of Tick-Borne Viruses at the Virus-Tick Interface

Ticks (Acari; Ixodidae) are the second most important vector for transmission of pathogens to humans, livestock, and wildlife. Ticks as vectors for viruses have been reported many times over the last 100 years. Tick-borne viruses (TBVs) belong to two orders (Bunyavirales and Mononegavirales) containing nine families (Bunyaviridae, Rhabdoviridae, Asfarviridae, Orthomyxovirida, Reoviridae, Flaviviridae, Phenuviridae, Nyamiviridae, and Nairoviridae). Among these TBVs, some are very pathogenic, causing huge mortality, and hence, deserve to be covered under the umbrella of one health. About 38 viral species are being transmitted by <10% of the tick species of the families Ixodidae and Argasidae. All TBVs are RNA viruses except for the African swine fever virus from the family Asfarviridae. Tick-borne viral diseases have also been classified as an emerging threat to public health and animals, especially in resource-poor communities of the developing world. Tick-host interaction plays an important role in the successful transmission of pathogens. The ticks' salivary glands are the main cellular machinery involved in the uptake, settlement, and multiplication of viruses, which are required for successful transmission into the final host. Furthermore, tick saliva also participates as an augmenting tool during the physiological process of transmission. Tick saliva is an important key element in the successful transmission of pathogens and contains different antimicrobial proteins, e.g., defensin, serine, proteases, and cement protein, which are key players in tick-virus interaction. While tick-virus interaction is a crucial factor in the propagation of tick-borne viral diseases, other factors (physiological, immunological, and gut flora) are also involved. Some immunological factors, e.g., toll-like receptors, scavenger receptors, Janus-kinase (JAK-STAT) pathway, and immunodeficiency (IMD) pathway are involved in tick-virus interaction by helping in virus assembly and acting to increase transmission. Ticks also harbor some endogenous viruses as internal microbial faunas, which also play a significant role in tick-virus interaction. Studies focusing on tick saliva and its role in pathogen transmission, tick feeding, and control of ticks using functional genomics all point toward solutions to this emerging threat. Information regarding tick-virus interaction is somewhat lacking; however, this information is necessary for a complete understanding of transmission TBVs and their persistence in nature. This review encompasses insight into the ecology and vectorial capacity of tick vectors, as well as our current understanding of the predisposing, enabling, precipitating, and reinforcing factors that influence TBV epidemics. The review explores the cellular, biochemical, and immunological tools which ensure and augment successful evading of the ticks' defense systems and transmission of the viruses to the final hosts at the virus-vector interface. The role of functional genomics, proteomics, and metabolomics in profiling tick-virus interaction is also discussed. This review is an initial attempt to comprehensively elaborate on the epidemiological determinants of TBVs with a focus on intra-vector physiological processes involved in the successful execution of the docking, uptake, settlement, replication, and transmission processes of arboviruses. This adds valuable data to the existing bank of knowledge for global stakeholders, policymakers, and the scientific community working to devise appropriate strategies to control ticks and TBVs.

Monitoring of ticks and their pathogens from companion animals obtained by the "tekenscanner" application in The Netherlands

Ticks are vectors for many pathogens of veterinary and medical interest. In order to monitor ticks and tick-borne pathogens, the “Tekenscanner” (Dutch for Tick scanner), a citizen science project, was launched in The Netherlands. It is a smartphone application for pet-owners to get ticks from their dog or cat, identified and checked for pathogens for free. At the same time, information about the pet and the geographic location of tick infestation becomes available for research. The application was launched in 2018, and the results of the first 6 months after launch of the app were reported. Ticks were identified based on morphology, and DNA was extracted and amplified by a panel of tick-borne pathogen-specific primers. Next, the amplicons were subjected to reverse line blot with specific probes for important pathogens to determine their presence or absence. The present paper describes the results of 2019 and 2020. There were 2260 ticks collected from 871 dogs and 255 cats (26 ticks were from an unknown host) and all pet owners were informed about the results. Four species of ticks were collected: Ixodes ricinus (90.0%), Ixodes hexagonus (7.3%), Dermacentor reticulatus (2.8%) and Rhipicephalus sanguineus (0.1%). Ixodes ricinus was the tick with the most divergent pathogens: Anaplasma sp. (1.3%), Babesia sp. (0.8%), Borrelia spp. (4.8%), Neoehrlichia sp. (3.7%) and Rickettsia helvetica (12.6%). In I. hexagonus, R. helvetica (1.8%) and Babesia sp. (0.6%) were detected and Rickettsia raoultii in D. reticulatus (16.2%). One of the two nymphs of R. sanguineus was co-infected with Borrelia and R. helvetica and the other one was uninfected. The high numbers of different pathogens found in this study suggest that companion animals, by definition synanthropic animals, and their ticks can serve as sentinels for emerging tick-borne pathogens.

Tick-Borne Pathogens, Babesia spp. and Borrelia burgdorferi s.l., in Sled and Companion Dogs from Central and North-Eastern Europe

Ticks are important vectors of numerous pathogens of medical and veterinary significance. The aim of the current study was to determine the prevalence of Babesia spp. and Borrelia burgdorferi s.l. in sled and pet dogs from Central and North-Eastern Europe. Neither Babesia spp. nor Borrelia burgdorferi s.l. infections were detected in sled dogs from seven countries (Poland, Lithuania, Latvia, Estonia, Belarus, Russia and Finland). The DNA of Babesia spp. was detected in 100% of symptomatic and 5.4% of asymptomatic pet dogs from Poland. Similarly, the DNA of Babesia spp. was identified in 82% of symptomatic and 3.8% of asymptomatic pet dogs from Ukraine. The DNA of Borrelia burgdorferi s.l. was detected in 4.4% of pet dogs. Molecular typing confirmed the presence of Babesia canis and Borrelia burgdorferi sensu stricto (s.s.) in selected samples. Four dogs were co-infected by B. canis and Borrelia burgdorferi s.l. Tick-borne pathogens constitute a serious health threat to pet dogs in Central and South-Eastern Europe, but were not observed among sled dogs from the same region of Europe nor in the Baltic countries.

The distribution of Dermacentor reticulatus in the Czech Republic re-assessed: citizen science approach to understanding the current distribution of the Babesia canis vector

Background

The range of the ornate dog tick Dermacentorreticulatus is rapidly expanding in Europe. This tick species is the vector of canine babesiosis, caused by Babesiacanis, and also plays a role in the transmission of Theileriaequi and Babesiacaballi in equids.

Methods

The geographic range of D.reticulatus in the Czech Republic was re-assessed, and an up-to-date distribution map is presented based on material and data obtained during a nationwide citizen science campaign. Received and flagged individuals of D.reticulatus were also analysed for the presence of B.canis DNA.

Results

In striking contrast to historical records, D.reticulatus was found in all regions of the Czech Republic, with most reports coming from the southeast and northwest of the country. Between February 2018 and June 2021, the project team received 558 photo reports of ticks and 250 packages containing ticks. Of the former, 71.1% were identified as Dermacentor sp. with the remainder identified as Ixodes sp., Haemaphysalis sp., Argas sp. or Hyalomma sp. The majority of specimens in the subset of ticks that were received (N = 610) were D.reticulatus (N = 568, 93.7%), followed by Ixodesricinus and Hyalomma spp. A total of 783 adult D.reticulatus, either received (568) or collected by flagging (215), were tested for the presence of B.canis DNA using species-specific nested PCR targeting part of the 18S rRNA gene; B.canis DNA was demonstrated in 22 samples (2.81%).

Conclusions

The continuous spread of D.reticulatus in the Czech Republic was documented in this study. In addition, DNA of B.canis was also detected in a number of ticks, suggesting the establishment of B.canis in the Czech Republic. These results suggest that veterinarians need to consider the possibility of canine babesiosis even in dogs without a history of travel.

Graphical Abstract

Co-infection with Babesia canis and Babesia gibsoni in a dog

A four-year-old intact male Boxer, that had a history of travelling to Serbia, was referred for lethargy and anaemia. Shortly before the dog was referred, it was diagnosed twice with an infection with Babesia canis and was treated with imidocarb both times. A blood smear evaluation was indicative of the presence of intraerythrocytic piroplasms. After receiving inconclusive results regarding the type of piroplasm, the dog was diagnosed with simultaneous infections with B. canis and Babesia gibsoni via real-time polymerase chain reaction (rt-PCR) testing. The dog was treated with imidocarb, atovaquone and azithromycin, and in a follow-up examination, the PCR results were negative for B. canis and B. gibsoni. Several weeks later, the dog was presented again, and a PCR was positive for B. gibsoni. After atovaquone and azithromycin failed to eliminate the parasites, a therapy attempt using metronidazole, clindamycin and doxycycline was initiated. Six months after diagnosis, the treatment appeared successful in eliminating B. gibsoni. This case report describes the clinical findings of the co-infection and the initiated diagnostic and therapeutic approaches.

Splenomegaly development and disseminated intravascular coagulation syndrome in acute canine babesiosis

Disseminated intravascular coagulation (DIC) syndrome is the main defining process in the pathogenetic axis of complications in canine babesiosis. The involvement of the spleen with further irreversible changes in the organ largely determines the severity of the animal’s condition after spontaneous babesiosis. The work presented here aimed to determine the role of the DIC syndrome as a triggering factor for lesions of the spleen. Clinical and laboratory studies (haematological, biochemical, hemodynamic) have been carried out. Pathological studies of the removed spleen were carried out by histological methods using universal and specific staining. After suffering acute spontaneous babesiosis, the development of hypersplenism and splenomegaly was found in dogs. The diagnosis was confirmed haematologically by the detected cytopenia, normochromic type anaemia. An additional parameter was a significantly increased erythrocyte sedimentation rate. The biochemical profile indicated the development of bilirubinaemia due to the conjugated fraction, hyperfermentation of transaminases, hypoalbuminemia, which reflected the development of hepatitis and liver failure. Markers of DIC syndrome in laboratory studies are represented by reliable hypofibrinogenemia, increased level of fibrinogen/fibrin degradation products, including D-dimer, and soluble fibrin monomer complexes. The multidirectional indices of coagulation tests (activated partial thromboplastin and prothrombin time) made it possible to classify the stage of “consumption coagulopathy” of the DIC syndrome. The haemodynamic parameters of the sick dogs were characterized by a significant deficit in the circulating blood volume. Together with the indicators of the “consumption coagulopathy” stage of the DIC syndrome, the hemodynamic indexes indicate a moderate degree of shock stage II – the stable reversibility, but the magnitude of the circulating blood volume deficit determines the tendency towards shock irreversibility. Histological studies have established a significant proliferation of the stromal elements of the organ, the formation of specific complexes of vessels with sinuses, clogging with blood clots, and the organ's parenchyma dystrophy. Such changes characterize complete splenomegaly, which is based on the organo-pathology of the DIC syndrome. The deposition of “old” fibrin in the connective tissue structures of the spleen indicates that DIC syndrome continues throughout the entire period of hyperplastic changes in the organ. The presence of hyalinosis in blood vessel walls of the spleen parenchyma determines irreversible changes in them. Thus, DIC syndrome is the basis for splenomegaly development in dogs after acute spontaneous babesiosis. It is confirmed by laboratory blood tests and histologically by the presence of fibrin thrombi in the structures of the organ, which determine the organopathology of the syndrome. The information obtained serves to expand the concepts of the pathogenesis of blood protozoal disease, define the high risk of complications that can become fatal for the health and life of animals.

Development of a real-time PCR method for rapid diagnosis of canine babesiosis and anaplasmosis

Background

Canine babesiosis and anaplasmosis, caused by Babesia canis and Anaplasma phagocytophilum, respectively, are significant tick-borne diseases in Baltic countries. Both diseases can be diagnosed on the basis of clinicopathological findings, by direct pathogen detection in blood smears or by indirect pathogen detection; however, because of high selectivity and specificity, molecular methods may be advantageous. The goal of this study was to develop a duplex real-time polymerase chain reaction (RT-PCR) method for the detection of B. canis and A. phagocytophilum in canine clinical samples.

Methods

Sequence-based polymorphism analysis of genes encoding B. canis-specific merozoite surface protein Bc28.1 (Bc28.1) and A. phagocytophilum malate dehydrogenase (mdh) was performed on pathogen isolates present in Latvian domestic dogs. The obtained results were used to design a species-specific duplex RT-PCR assay.

Results

The presence of three B. canis Bc28.1 gene sequence types was revealed in canine samples with a nonuniform geographical distribution, and two types of A. phagocytophilum mdh genes were detected. The novel duplex RT-PCR assay provided correct classification of samples positive and negative for B. canis and A. phagocytophilum. The analytical sensitivity of this assay was ten gene copies/ reaction for both pathogens.

Conclusions

A novel duplex RT-PCR molecular method was developed for the detection of B. canis and A. phagocytophilum in canine clinical samples. Sequence variability of Bc28.1 and mdh genes indicated the genetic variability of B. canis and A. phagocytophilum isolates occurring in Latvian domestic dogs.

Graphic Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04756-9.

Seroprevalence and associated risk factors for vector-borne pathogens in dogs from Egypt

Background

Dogs play an important role as reservoirs of many zoonotic vector-borne pathogens worldwide, yet reports of canine vector-borne diseases (CVBDs) in Egypt are scarce.

Methods

Serum samples were collected from pet dogs (n = 500) of the three most common breeds (German Shepherd, Rottweiler and Pit Bull) in five Governates of Cairo (n = 230), Giza (n = 110), Al-Qalyubia (n = 60), Al-Gharbia (n = 60) and Kafr El-Sheikh (n = 40) with a hot desert climate. The presence of antibodies to Anaplasma spp. (A. phagocytophilum, A. platys), Ehrlichia spp. (E. canis, E. chaffeensis, E. ewingii), Borrelia burgdorferi (s.l.) and Dirofilaria immitis were assessed using IDEXX SNAP^® 4Dx^® ELISA tests. For each pathogen, risk factors (i.e. geographical area, keeping condition, sex, age, breed, tick infestation, weekly sanitation of dog enclosures and application of ectoparasiticides) were evaluated by logistic regression approach.

Results

In total, 18.2% (n = 91, 95% CI 15.1–21.8) of dogs scored seropositive for at least one pathogen, the most frequent being Ehrlichia spp. (n = 56; 11.2%; 95% CI 8.7–14.3) followed by Anaplasma spp. (n = 33; 6.6%, 95% CI 4.7–9.1), Borrelia burgdorferi (s.l.) (n = 9; 1.8%, 95% CI 0.9–3.4) and D. immitis (n = 7; 1.4%, 95% CI 0.9–2.9). In the tested population, 15.4% (95% CI 12.5–18.8) of dogs were exposed to a single pathogen while 2.4 (95% CI 1.4–4.2) and 0.4% (95% CI 0.1–1.4) were simultaneously exposed to two or three pathogens, respectively. Major risk factors associated with VBDs were living outdoors (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001), female sex (Ehrlichia spp., P = 0.005), German Shepherd breed (Anaplasma spp., P = 0.04; Ehrlichia spp., P = 0.03), tick infestation (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001; B. burgdorferi (s.l.), P = 0.003; D. immitis, P = 0.02), irregular sanitation (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001; B. burgdorferi (s.l.), P = 0.002; D. immitis, P = 0.01) and not using ectoparasiticides (Anaplasma spp., P = 0.0001; Ehrlichia spp., P = 0.0001; B. burgdorferi (s.l.), P = 0.007).

Conclusion

To our knowledge, this is the first large-scale seroepidemiological study of CVBDs in Egypt. Considering that all of the detected pathogens are potentially zoonotic, effective ectoparasite control strategies, regular examination of pet dogs and successful chemoprophylaxis are advocated.

Current review of isoxazoline ectoparasiticides used in veterinary medicine

The isoxazolines are a novel class of ectoparasiticides with potent inhibitory activity on glutamate- and gamma-aminobutyric acid-gated chloride channel located in nervous system of invertebrates. In recent years, studies have been performed to evaluate the efficacy and safety of isoxazolines against various types of ectoparasites, including fleas, ticks, and mites. As more single and combined isoxazoline products have been approved by the United States Food and Drug Administration and European Medicines Agency, a more comprehensive understanding of isoxazolines becomes essential for veterinary clinical practitioners. This article provides a complete review of isoxazolines with respect to pharmacodynamics, pharmacokinetics, ectoparasiticidal efficacy, and safety, which will provide veterinarians information to allow them to make the best choice of ectoparasiticide for their clients' specific needs.

Tick-borne zoonoses and commonly used diagnostic methods in human and veterinary medicine

Around the world, human health and animal health are closely linked in terms of the One Health concept by ticks acting as vectors for zoonotic pathogens. Animals do not only maintain tick cycles but can either be clinically affected by the same tick-borne pathogens as humans and/or play a role as reservoirs or sentinel pathogen hosts. However, the relevance of different tick-borne diseases (TBDs) may vary in human vs. veterinary medicine, which is consequently reflected by the availability of human vs. veterinary diagnostic tests. Yet, as TBDs gain importance in both fields and rare zoonotic pathogens, such as Babesia spp., are increasingly identified as causes of human disease, a One Health approach regarding development of new diagnostic tools may lead to synergistic benefits. This review gives an overview on zoonotic protozoan, bacterial and viral tick-borne pathogens worldwide, discusses commonly used diagnostic techniques for TBDs, and compares commercial availability of diagnostic tests for humans vs. domestic animals, using Germany as an example, with the aim of highlighting existing gaps and opportunities for collaboration in a One Health framework.

Importation of Ticks on Companion Animals and the Risk of Spread of Tick-Borne Diseases to Non-Endemic Regions in Europe

Increased human mobility elevates the risk of exposure of companion animals travelling with their owners or imported from other regions to tick attacks. In this study, we highlight the potential role of dogs and cats taken for tourist trips or imported animals in the spread of ticks and tick-borne pathogens. The Rhipicephalus sanguineus tick, which is a vector of numerous pathogens causing diseases in animals and humans, is imported most frequently from endemic areas to many European countries. Additionally, alien tick species with high epizootic and epidemiological importance can be imported on dogs from other continents. Companion animals play an even greater role in the spread of autochthonous tick species and transmission of tick pathogens to other animals and humans. Although the veterinary and medical effects of the parasitism of ticks carried by companion animals travelling with owners or imported animals are poorly assessed, these animals seem to play a role in the rapid spread of tick-borne diseases. Development of strategies for protection of the health of companion animals in different geographic regions should take into account the potential emergence of unknown animal tick-borne diseases that can be transmitted by imported ticks.

Zoonotic Tick-Borne Pathogens in Temperate and Cold Regions of Europe-A Review on the Prevalence in Domestic Animals

Ticks transmit a variety of pathogens affecting both human and animal health. In temperate and cold regions of Europe (Western, Central, Eastern, and Northern Europe), the most relevant zoonotic tick-borne pathogens are tick-borne encephalitis virus (TBEV), Borrelia spp. and Anaplasma phagocytophilum. More rarely, Rickettsia spp., Neoehrlichia mikurensis, and zoonotic Babesia spp. are identified as a cause of human disease. Domestic animals may also be clinically affected by these pathogens, and, furthermore, can be regarded as sentinel hosts for their occurrence in a certain area, or even play a role as reservoirs or amplifying hosts. For example, viraemic ruminants may transmit TBEV to humans via raw milk products. This review summarizes the role of domestic animals, including ruminants, horses, dogs, and cats, in the ecology of TBEV, Borrelia spp., A. phagocytophilum, Rickettsia spp., N. mikurensis, and zoonotic Babesia species. It gives an overview on the (sero-)prevalence of these infectious agents in domestic animals in temperate/cold regions of Europe, based on 148 individual prevalence studies. Meta-analyses of seroprevalence in asymptomatic animals estimated an overall seroprevalence of 2.7% for TBEV, 12.9% for Borrelia burgdorferi sensu lato (s.l.), 16.2% for A. phagocytophilum and 7.4% for Babesia divergens, with a high level of heterogeneity. Subgroup analyses with regard to animal species, diagnostic test, geographical region and decade of sampling were mostly non-significant, with the exception of significantly lower B. burgdorferi s.l. seroprevalences in dogs than in horses and cattle. More surveillance studies employing highly sensitive and specific test methods and including hitherto non-investigated regions are needed to determine if and how global changes in terms of climate, land use, agricultural practices and human behavior impact the frequency of zoonotic tick-borne pathogens in domestic animals.

First Cases of Natural Infections with Borrelia hispanica in Two Dogs and a Cat from Europe

Canine cases of relapsing fever (RF) borreliosis have been described in Israel and the USA, where two RF species, Borrelia turicatae and Borrelia hermsii, can cause similar clinical signs to the Borrelia persica in dogs and cats reported from Israel, including fever, lethargy, anorexia, thrombocytopenia, and spirochetemia. In this report, we describe the first clinical cases of two dogs and a cat from Spain (Cordoba, Valencia, and Seville) caused by the RF species Borrelia hispanica. Spirochetes were present in the blood smears of all three animals, and clinical signs included lethargy, pale mucosa, anorexia, cachexia, or mild abdominal respiration. Laboratory findings, like thrombocytopenia in both dogs, may have been caused by co-infecting pathogens (i.e., Babesia vogeli, confirmed in one dog). Anemia was noticed in one of the dogs and in the cat. Borrelia hispanica was confirmed as an infecting agent by molecular analysis of the 16S rRNA locus. Molecular analysis of housekeeping genes and phylogenetic analyses, as well as successful in vitro culture of the feline isolate confirmed the causative agent as B. hispanica.

Babesiosis in Latvian domestic dogs, 2016-2019

Canine babesiosis is tick-borne infection that represents a major veterinary issue in Central and Eastern Europe with a tendency to expand northwards. The first published report in Latvia about autochthonous cases of babesiosis in domestic dogs with no travel history was in 2013, and to the best of our knowledge, no other studies on this issue have been published to date. The aim of this study was to analyze the occurrence and clinical manifestations of babesiosis in Latvian domestic dogs with a history of tick exposure to determine the extent to which Babesia sp. causes the disease and to map outbreaks in Latvia. From 2016 to 2019, blood samples from dogs were collected, and molecular testing was performed by nested PCR using Babesia sp.-specific primers. In total, 43 of 262 samples were Babesia canis-positive. A seasonal pattern was observed for the outbreaks, as the majority of B. canis-positive samples (98%) were submitted between April and June, and there was a single canine babesiosis case recorded in October. Nearly half of the cases (46.5%) were recorded in the capital, Riga, and other cases were recorded in southern and western parts of Latvia. Clinical signs were consistent with typical manifestations of acute canine babesiosis; most common hematological changes were thrombocytopenia (89%) and normocytic normochromic anemia (69%). Blood smear microscopy was positive for 79% of cases. Two B. canis genotypes were distinguished on the basis of two nucleotide (GA → AG) substitutions in the 18S rRNA gene at positions 610/611; however, no relationship between the genotypes and the severity of the disease was found. In conclusion, canine babesiosis has become an endemic disease in the southern and western regions of Latvia and is caused solely by the large babesia species B. canis. Awareness among veterinarians and pet owners regarding the disease should be increased.

Tick-borne pathogens in ticks collected from dogs, Latvia, 2011-2016

BACKGROUND

Different tick species are able to transmit different pathogens, and tick-borne diseases are of substantial concern worldwide for both humans and animals. Environmental changes and changes in the range of tick species, including Dermacentor reticulatus in Europe, can affect the spread of zoonotic pathogens. The aim of this study was to investigate the prevalence of the tick-borne pathogens in ticks removed from dogs in Latvia, and to explore possible changes between years 2011 and 2016.

RESULTS

In 2011, only Ixodes ticks (221 Ixodes ricinus and 22 Ixodes persulcatus) were collected from dogs, while in 2016 tick samples belonged to Ixodes ricinus (360), Ixodes persulcatus (2) and Dermacentor reticulatus (27) species. In total, 35.8 and 40.0% of adult ticks were pathogen-positive in 2011 and 2016, respectively; the difference was not statistically significant (P > 0.05). The molecular analysis indicated the presence of 13 tick-borne microorganisms; the most prevalent pathogen was Rickettsia, followed by Borrelia burgdorferi sensu lato group spirochetes, Anaplasma phagocytophilum and Babesia species. Borrelia miyamotoi was also present. A co-infection with two and three tick-borne pathogens was detected in 7.9 and 7.4% of Ixodes ricinus and Dermacentor reticulatus, respectively. The results of this study confirmed that the spread of novel vectors could bring additional risk of exposure to novel emerging pathogens to pets and their owners, as both Babesia canis and Rickettsia raoultii were shown to be highly associated with Dermacentor reticulatus ticks in Latvia.

CONCLUSIONS

This study demonstrates the potential danger from the inadvertent introduction of novel disease pathogens and vectors. Awareness of co-infections and Dermacentor reticulatus-related pathogens needs to be increased.

Retrospective analysis of vector-borne infections in dogs after travelling to endemic areas (2007-2018)

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There is a risk even for dogs with limited time of exposure to obtain a vector-borne infection.

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Prevention of vector-transferred pathogens in dogs travelling to endemic areas is important.

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The owners should be educated regarding the vectors, diseases, risks and prophylaxis.

Canine vector-borne infections gained in importance in Germany due to growing tourist traffic, the increased import of dogs from abroad and the changing of climatic conditions. The Mediterranean region and southeastern Europe are geographical areas where pathogens such as Leishmania (L.) infantum, Hepatozoon (H.) canis, Ehrlichia (E.) canis, Anaplasma (A.) platys and Dirofilaria (D.) spp. are endemic. Meanwhile, Babesia (B.) spp. and A. phagocytophilum are present in central and western Europe. The objective of this retrospective study was to evaluate whether dogs were exposed to a corresponding risk of infection when travelling to regions in the Mediterranean area and southeastern Europe, which are endemic for these pathogens.

Medical records and laboratory test results of 303 dogs that travelled to 14 countries endemic for the mentioned canine vector-borne pathogens and that were presented to the Small Animal Clinic at Freie Universität Berlin between 2007 and 2018 were retrospectively reviewed. A total of 1174 test results from external laboratories were descriptively analysed including 525 test results of direct and 649 of indirect determination methods.

Overall, 13% of the tested dogs (40/303) were positive for at least one pathogen. Concurrent infections with two pathogens were detected in 1% of the dogs (4/303). The positive results were: E. canis 8% (18/231 dogs; Polymerase chain reaction [PCR] 3/73, indirect immunofluorescence test [IFAT] 18/209 dogs), L. infantum 5% (14/260 dogs; PCR 5/80, IFAT or enzyme linked immunosorbent assay [ELISA] 11/251 dogs), Babesia spp. 5% (11/232 dogs; Babesia spp. PCR 3/127, B. canis/vogeli IFAT or ELISA 8/160, B. gibsoni IFAT 2/22), Dirofilaria spp. 1% (1/133 dogs; D. immitis antigen-ELISA 1/117, microfilariae PCR 0/16, Knott´s test 0/69 dogs). None of the dogs has been tested positive in a combined Babesia spp./Hepatozoon spp. PCR test (0/15 dogs) and for H. canis (0/17 dogs; PCR) or A. platys (0/11 dogs; PCR).

There is a substantial risk for dogs travelling to areas endemic for vector-borne pathogens even with limited time of exposure to get infected. The data indicates the importance of owner education and prophylactic measurements against vector-borne infections in dogs travelling to endemic areas.

Cross-Sectional Serosurvey and Factors Associated with Exposure of Dogs to Vector-Borne Pathogens in Greece

Blood samples from 2620 dogs living in 7 different areas were used for the detection of antibodies against Ehrlichia canis and Borrelia burgdorferi and Dirofilaria immitis antigen. Previously published seropositivity data against Leishmania infantum from the same samples were also used to identify multiple-pathogen seropositivity. The associations between seropositivity against each pathogen and gender, age, utility, hair length, and region of residence were evaluated by multivariate logistic regression analyses. The prevalence of seropositivity against E. canis, B. burgdorferi, and D. immitis was 12.25%, 2.23%, and 5.96%, respectively. Double- and triple-pathogen seropositivity was detected in seven different combinations. Age and region of residence were strongly associated with seropositivity against all pathogens. The association between seropositivity and the area of residence highlights the need for regular testing of dogs for vector-borne pathogens in areas with similar conditions to define control measures.

Seroprevalence and Current Infections of Canine Vector-Borne Diseases in Costa Rica

Domestic dogs may carry several vector-borne pathogens, including zoonotic agents, especially in tropical regions like Central America. The epidemiology of these pathogens is prone to change due to urbanization, trade and travel as well as climate change, necessitating repeated monitoring. This study aims to present a comprehensive picture of canine vector-borne diseases in Costa Rica, combining data on seroprevalence with molecular species identification of the causative pathogens. In this survey, 294 dogs from all seven provinces of Costa Rica were included. After a clinical examination, diagnostic blood samples were analyzed with regard to packed cell volume (PCV) and presence of microfilaria. Serum samples were tested for antibodies against Ehrlichia spp., Anaplasma spp., Babesia spp., Borrelia burgdorferi sensu lato (s.l.) as well as antigen of Dirofilaria immitis. Seropositive and microfilaremic blood samples were analyzed by PCR to detect current infections and identify the pathogen species. Overall, 45.24% (133/294, 95% CI: 39.45–51.11%) of dogs were seropositive for at least one of the tested pathogens. Seroprevalence was highest for Ehrlichia spp. (39.46%, 116/294, 95% CI: 33.83–45.29%), followed by Babesia spp. (23.13%, 68/294, 95% CI: 18.43–28.38%), Anaplasma spp. (13.27%, 39/294, 95% CI: 9.61–17.69%), and B. burgdorferi s.l. (0.34%, 1/294, 95% CI: 0.01–1.88%). Generalized linear mixed models indicated a significant association of Ehrlichia-, Anaplasma- and Babesia-seropositivity, as well as a significant effect of age and breed on Ehrlichia-seropositivity. Furthermore, a statistically significant negative effect of Ehrlichia-, Anaplasma-, and Babesia-seropositivity on PCV was found. Regarding current infections, Ehrlichia canis DNA was detected in 51.72% (60/116, 95% CI: 42.26–61.10%) of Ehrlichia-seropositive dogs, while Ehrlichia ewingii and Ehrlichia chaffeensis were not detected. Furthermore, 10.26% (4/39, 95% CI: 2.87–24.22%) of Anaplasma-seropositive dogs were coinfected with Anaplasma phagocytophilum and Anaplasma platys, while one animal (2.56%, 95% CI: 0.65–13.48%) was infected with A. phagocytophilum only. Among Babesia-seropositive dogs, Babesia vogeli and Hepatozoon canis were detected in one animal each (1.47%, 1/68, 95% CI: 0.04–7.92%). Dirofilaria immitis antigen was detected in 4.42% (13/294, 95% CI: 2.38–7.44%) of dogs. In microfilaremic animals, D. immitis as well as Acanthocheilonema reconditum infections were identified. This survey demonstrates that canine vector-borne pathogens, including zoonotic agents like A. phagocytophilum and D. immitis, are widespread in Costa Rica. Thus, protection of dogs from disease-transmitting vectors is recommended from an animal welfare as well as public health perspective.

Prevalence and risk factors for selected canine vector-borne diseases in Greece

Background

Canine vector-borne diseases (CVBDs) represent a wide group of diseases of major significance for canine health. In addition to their veterinary importance, many of these diseases are of great zoonotic concern, posing a risk of potential transmission to humans. To date, there has been scant knowledge regarding the prevalence, distribution and risk factors of CVBDs in Greece. Therefore, the objectives of the present study were to update the current knowledge on the seroprevalence of Dirofilaria immitis, Anaplasma spp., Ehrlichia spp. and Borrelia burgdorferi (sensu lato) in dogs in Greece and, furthermore, to assess possible environmental and any other risk factors associated with these infections. A total of 1000 apparently healthy and randomly selected dogs, presented in veterinary clinics, were involved at the national level (n = 66 municipalities). Serum samples were obtained from each individual dog and were tested using the SNAP^® 4Dx^® Plus kit from IDEXX Laboratories. Possible risk factors were assessed using binary regression models, including dogs’ lifestyle, climatological parameters and the altitude of the region.

Results

Overall, 21.8% (95% CI: 19.4–24.5%) of the sampled dogs were found to be seropositive to at least one of the four pathogens examined. The most prevalent pathogen was Ehrlichia spp. (12.5%, 95% CI: 10.6–14.7) followed by D. immitis (9.0%, 95% CI: 7.8–11.5) and Anaplasma spp. (6.2%, 95% CI: 4.9–7.9). The lowest prevalence (0.1%) was recorded for B. burgdorferi (s.l.) where only one dog was found to be positive. Among the examined risk factors, low mean temperature was found to increase the prevalence of Ehrlichia spp. (P ≤ 0.001) and Anaplasma spp. (P ≤ 0.001), while low minimum temperature increased the prevalence of D. immitis (P ≤ 0.001). In addition, low total annual rainfall had an effect of the prevalence of Ehrlichia spp. (P ≤ 0.01). Altitude also had a significant effect on the prevalence of D. immitis (P ≤ 0.05) and Anaplasma spp. (P ≤ 0.01).

Conclusions

To our knowledge, this is the first large-scale seroepidemiological study of CVBDs in Greece. It has been evidenced that environmental factors such as temperature, rainfall and altitude can influence the prevalence and distribution of CVBDs.

"Tekenscanner": a novel smartphone application for companion animal owners and veterinarians to engage in tick and tick-borne pathogen surveillance in the Netherlands

Background

The engagement of companion animal owners into the process of collecting epidemiological data can be facilitated through smartphone applications. In April 2018, the “tekenscanner“ (Dutch for tick scanner) app was launched with the aim of engaging pet owners and veterinarians to record ticks removed from their pets and submit these ticks for identification and pathogen testing. Tick-borne pathogens identified in ticks removed from dogs and cats during the first 6 months after the app was launched in the Netherlands are reported.

Methods

The tekenscanner app was used to record the geographical coordinates of ticks removed from dogs or cats onto a map of the Netherlands. A barcode was assigned to each tick for the easy tracking of each submission to our laboratory for taxonomic identification. Thereafter, DNA extracted from the ticks was PCR amplified, subjected to reverse line blot hybridization (RLB) and screened for a broad range of tick-borne pathogens. Results were added to the same app, usually within 2 weeks after the submission of each tick.

Results

The app was downloaded 5591 times and resulted in the collection of 1273 georeferenced and barcoded ticks, with a peak submission in May and June of 2018. There were 1005 ticks collected from 406 dogs and 268 ticks collected from 111 cats. Ixodes ricinus was the predominant species (90.0%), with all stages found on dogs as well as on cats. Ixodes hexagonus (7.3%) female and nymphal ticks were also identified on both hosts, whereas adults of Dermacentor reticulatus (2.4%) and Rhipicephalus sanguineus (0.2%) were exclusively found on dogs. Nearly 15% of the ticks recovered from dogs carried one or more pathogens, whereas 13.8% of the ticks removed from cats were infected. Ixodes ricinus collected from dogs contained Borrelia spp. (1.9%), Babesia spp. (0.7%), Anaplasma phagocytophilum (1.3%), “Candidatus Neoehrlichia mikurensis” (2.9%) and Rickettsia helvetica (7.3%). Ixodes ricinus recovered from cats were infected with Borrelia spp. (1.9%), Babesia spp. (0.4%), A. phagocytophilum (1.9%), “Ca. Neoehrlichia mikurensis” (2.6%) and R. helvetica (6.7%). Ixodes hexagonus ticks (n = 93) were not infected. Dermacentor reticulatus ticks, found only in autumn, were infected with Rickettsia raoultii (16 %) and A. phagocytophilum. Three R. sanguineus, on dogs from France and the USA imported into the Netherlands, were all negative.

Conclusions

The tekenscanner app is a versatile tool to use for submission of ticks and facilitated the fast feedback of test results. Community engagement through the app is suitable for identifying hotspots for ticks and tick-borne pathogens and provided an early warning system for exotic ticks invading the Netherlands.

Retrospective evaluation of vector-borne infections in dogs imported from the Mediterranean region and southeastern Europe (2007-2015)

BACKGROUND

Canine vector-borne infections have gained importance in Germany due to growing tourist traffic and an increased import of dogs from abroad. Endemic regions for pathogens such as Leishmania infantum, Hepatozoon canis, Ehrlichia canis, Anaplasma platys and Dirofilaria spp. are the Mediterranean area and southeastern Europe. Babesia species and Anaplasma phagocytophilum are present all over Europe. The objective of this retrospective study was to evaluate the prevalence of vector-borne infections in dogs imported from defined endemic countries in the Mediterranean area and southeastern Europe.

METHODS

Medical records and laboratory test results of 345 dogs that were imported to Germany from 17 endemic countries and that were presented to the Small Animal Clinic at Freie Universität Berlin between 2007 and 2015 were retrospectively reviewed. A total of 1368 test results from external laboratories were descriptively analysed including 576 and 792 test results of direct and indirect detection methods, respectively.

RESULTS

Overall, 35% (122/345 dogs) were positive for at least one pathogen. Concurrent infections with two to four pathogens were detected in 8% of the dogs (27/345). The positive results were: L. infantum 21% (66/314 dogs; methods: PCR 20/79, IFAT or ELISA 63/308 dogs), E. canis 16% (45/278 dogs; methods: PCR 8/68, IFAT 43/257 dogs), H. canis 11% (3/28 dogs; method: PCR), Babesia spp. 10% (25/251 dogs; methods: Babesia spp. PCR 3/98, B. canis/vogeli IFAT or ELISA 22/214 and B. gibsoni IFAT 0/13 dogs), Dirofilaria spp. 7% (13/178 dogs; methods: D. immitis Ag-ELISA 8/156, Knott's test 7/95, microfilariae PCR 5/23 dogs) and A. platys 5% (1/21 dogs; method: PCR). None of 8 tested dogs were positive in a combined Babesia spp./Hepatozoon spp. PCR test.

CONCLUSIONS

Dogs, which are imported from countries which are endemic for vector-borne infections should be thoroughly tested using direct and indirect detection methods. Potential owners of imported dogs should be informed about the diseases, risks and incubation periods.

Role of mustelids in the life-cycle of ixodid ticks and transmission cycles of four tick-borne pathogens

BACKGROUND

Elucidating which wildlife species significantly contribute to the maintenance of Ixodes ricinus populations and the enzootic cycles of the pathogens they transmit is imperative in understanding the driving forces behind the emergence of tick-borne diseases. Here, we aimed to quantify the relative contribution of four mustelid species in the life-cycles of I. ricinus and Borrelia burgdorferi (sensu lato) in forested areas and to investigate their role in the transmission of other tick-borne pathogens. Road-killed badgers, pine martens, stone martens and polecats were collected in Belgium and the Netherlands. Their organs and feeding ticks were tested for the presence of tick-borne pathogens.

RESULTS

Ixodes hexagonus and I. ricinus were found on half of the screened animals (n = 637). Pine martens had the highest I. ricinus burden, whereas polecats had the highest I. hexagonus burden. We detected DNA from B. burgdorferi (s.l.) and Anaplasma phagocytophilum in organs of all four mustelid species (n = 789), and Neoehrlichia mikurensis DNA was detected in all species, except badgers. DNA from B. miyamotoi was not detected in any of the investigated mustelids. From the 15 larvae of I. ricinus feeding on pine martens (n = 44), only one was positive for B. miyamotoi DNA, and all tested negative for B. burgdorferi (s.l.), N. mikurensis and A. phagocytophilum. The two feeding larvae from the investigated polecats (n = 364) and stone martens (n = 39) were negative for all four pathogens. The infection rate of N. mikurensis was higher in feeding nymphs collected from mustelids compared to questing nymphs, but not for B. burgdorferi (s.l.), B. miyamotoi or A. phagocytophilum.

CONCLUSIONS

Although all stages of I. ricinus can be found on badgers, polecats, pine and stone martens, their relative contribution to the life-cycle of I. ricinus in forested areas is less than 1%. Consequently, the relative contribution of mustelids to the enzootic cycles of I. ricinus-borne pathogens is negligible, despite the presence of these pathogens in organs and feeding ticks. Interestingly, all four mustelid species carried all stages of I. hexagonus, potentially maintaining enzootic cycles of this tick species apart from the cycle involving hedgehogs as main host species.

Dermacentor reticulatus in Berlin/Brandenburg (Germany): Activity patterns and associated pathogens

Dermacentor reticulatus is one of the most important European tick species. However, its spatial distribution, seasonality and regional vector role are not well known. This study aimed to gather information about abundance patterns of questing ticks and associated pathogens in unfed female adult D. reticulatus in the Berlin/Brandenburg area. Using the flagging method, questing ticks were collected at four sites in 2010-2012 and 2000 D. reticulatus were analysed regarding infection with Rickettsia, Babesia, Borrelia and Anaplasmataceae by conventional or real-time PCR. Dermacentor reticulatus showed a bimodal activity pattern: highest numbers of adult ticks were recorded between March and end of May (mean 50 ticks/h) and from mid-August until end of November (mean 102 ticks/h). During summer, almost complete inactivity was observed (mean 0.4 ticks/h). Sporadic samplings from December to February revealed tick activity also during winter (mean 47 ticks/h), which was characterised by large fluctuations. Using negative binomial regression analysis, significant influences of the variables sampling site, season and temperature on the abundance of questing D. reticulatus were determined. The parameters relative humidity and year were not of significant importance. PCR analyses showed an average prevalence of 64% for Rickettsia sp. Large differences in pathogen frequencies were observed between sampling sites (31.4-78.3%). Regression analysis demonstrated a significant influence of the sampling site but not of season and year. Examinations regarding other pathogen groups indicated prevalences of 0.25% (Borrelia sp.) and 0.05% (Anaplasmataceae) but absence of Babesia sp. Sequencing of positive samples revealed infections with Rickettsia raoultii, Borrelia miyamotoi, Borrelia afzelii and Anaplasma phagocytophilum. The study shows stable populations of D. reticulatus in Berlin/Brandenburg. People should be aware of ticks throughout the year since Ixodes ricinus is co-endemic and active in spring, summer and autumn while adult D. reticulatus are active throughout the year and even in winter during periods of frost as long as it is warming up during the day. Prevalence of R. raoultii in the present study is among the highest described for D. reticulatus. Borrelia miyamotoi was detected for the first time in D. reticulatus, illustrating the importance of screening studies to evaluate the pathogen structure in D. reticulatus populations.

Canine Babesiosis: Where Do We Stand?

Canine babesiosis is a tick-borne disease caused by protozoal haemoparasites of different Babesia species. Babesiosis is one of the most important globally extended and quickly spreading tick-borne infections of dogs. This comprehensive review gives an in-depth overview of Babesia species currently identified in dogs together with relevant vector tick species and their geographical distribution, life cycle and transmission of parasite. The main mechanisms in the pathogenesis of babesiosis are described and elucidated by recent literature overview. As Babesia infection causes a disease with very variable clinical manifestations, special attention is given to clinical signs, laboratory features and clinicopathological findings. The diagnosis of canine babesiosis by microscopy, serological and molecular methods is reviewed, together with recent advances in mass spectrometry based assays. Accurate detection and species recognition are important for the selection of the appropriate therapy, monitoring and prediction of the outcome of the disease. Finally, guidelines for the treatment and prevention of canine babesiosis are given.

Managing mosquitoes and ticks in a rapidly changing world - Facts and trends

Vector-borne diseases transmitted by mosquitoes and ticks are on the rise. The effective and sustainable control of these arthropod vectors is a puzzling challenge for public health worldwide. In the present review, I attempted to provide a concise and updated overview of the current mosquito and tick research scenario. The wide array of control tools recently developed has been considered, with special reference to those approved by the World Health Organization Vector Control Advisory Group (WHO VCAG), as well as novel ones with an extremely promising potential to be exploited in vector control programs. Concerning mosquitoes, a major focus has been given on genetically modified vectors, eave tubes, attractive toxic sugar baits (ATSB) and biocontrol agents. Regarding ticks, the recent development of highly effective repellents and acaricides (including nanoformulated ones) as well as behavior-based control tools, has been highlighted. In the second part of the review, key research questions about biology and control of mosquitoes and ticks have been critically formulated. A timely research agenda outlining hot issues to be addressed in mosquito and tick research is provided. Overall, it is expected that the present review will contribute to boost research and applications on successful mosquito and tick control strategies, along with an improved knowledge of their biology and ecology.

ACVIM consensus update on Lyme borreliosis in dogs and cats

An update of the 2006 American College of Veterinary Internal Medicine (ACVIM) Small Animal Consensus Statement on Lyme Disease in Dogs: Diagnosis, Treatment, and Prevention was presented at the 2016 ACVIM Forum in Denver, CO, followed by panel and audience discussion and a drafted consensus statement distributed online to diplomates for comment. The updated consensus statement is presented below. The consensus statement aims to provide guidance on the diagnosis, treatment, and prevention of Lyme borreliosis in dogs and cats.

Does co-infection with vector-borne pathogens play a role in clinical canine leishmaniosis?

BACKGROUND

The severity of canine leishmaniosis (CanL) due to Leishmania infantum might be affected by other vector-borne organisms that mimic its clinical signs and clinicopathological abnormalities. The aim of this study was to determine co-infections with other vector-borne pathogens based on serological and molecular techniques in dogs with clinical leishmaniosis living in Spain and to associate them with clinical signs and clinicopathological abnormalities as well as disease severity.

METHODS

Sixty-one dogs with clinical leishmaniosis and 16 apparently healthy dogs were tested for Rickettsia conorii, Ehrlichia canis, Anaplasma phagocytophilum and Bartonella henselae antigens by the immunofluorescence antibody test (IFAT) and for E. canis, Anaplasma spp., Hepatozoon spp., Babesia spp. and filarioid DNA by polymerase chain reaction (PCR).

RESULTS

Among the dogs examined by IFAT, the seroprevalences were: 69% for R. conorii, 57% for E. canis, 44% for A. phagocytophilum and 37% for B. henselae; while the prevalences found by PCR were: 8% for Ehrlichia/Anaplasma, 3% for Anaplasma platys and 1% for H. canis. No other pathogen DNA was detected. Statistical association was found between dogs with clinical leishmaniosis and seroreactivity to R. conorii antigen (Fisher's exact test: P = 0.025, OR = 4.1, 95% CI = 1-17) and A. phagocytophilum antigen (Fisher's exact test: P = 0.002, OR = 14.3, 95% CI = 2-626) and being positive to more than one serological or molecular tests (co-infections) (Mann-Whitney test: U = 243, Z = -2.6, n ₁  = 14, n ₂  = 61, P = 0.01) when compared with healthy dogs. Interestingly, a statistical association was found between the presence of R. conorii, E. canis, A. phagocytophilum and B. henselae antibodies in sick dogs and some clinicopathological abnormalities such as albumin and albumin/globulin ratio decrease and increase in serum globulins. Furthermore, seroreactivity with A. phagocytophilum antigens was statistically associated with CanL clinical stages III and IV.

CONCLUSIONS

This study demonstrates that dogs with clinical leishmaniosis from Catalonia (Spain) have a higher rate of co-infections with other vector-borne pathogens when compared with healthy controls. Furthermore, positivity to some vector-borne pathogens was associated with more marked clinicopathological abnormalities as well as disease severity with CanL.

Control of Lyme borreliosis and other Ixodes ricinus-borne diseases

Lyme borreliosis (LB) and other Ixodes ricinus-borne diseases (TBDs) are diseases that emerge from interactions of humans and domestic animals with infected ticks in nature. Nature, environmental and health policies at (inter)national and local levels affect the risk, disease burden and costs of TBDs. Knowledge on ticks, their pathogens and the diseases they cause have been increasing, and resulted in the discovery of a diversity of control options, which often are not highly effective on their own. Control strategies involving concerted actions from human and animal health sectors as well as from nature managers have not been formulated, let alone implemented. Control of TBDs asks for a “health in all policies” approach, both at the (inter)national level, but also at local levels. For example, wildlife protection and creating urban green spaces are important for animal and human well-being, but may increase the risk of TBDs. In contrast, culling or fencing out deer decreases the risk for TBDs under specific conditions, but may have adverse effects on biodiversity or may be societally unacceptable. Therefore, in the end, nature and health workers together must carry out tailor-made control options for the control of TBDs for humans and animals, with minimal effects on the environment. In that regard, multidisciplinary approaches in environmental, but also medical settings are needed. To facilitate this, communication and collaboration between experts from different fields, which may include patient representatives, should be promoted.

Repellence of essential oils and selected compounds against ticks-A systematic review

Ticks act as vectors of a wide range of infectious agents, far encompassing any other group of bloodsucking arthropods worldwide. The prevention of tick-borne diseases is strictly linked to the successful management of tick vector populations. The employ of repellents can represent a worth solution to avoid tick bites. It is widely adopted to protect travellers and pets exposed to ticks during limited periods of the year. The use of natural products as active ingredients in eco-friendly repellent formulations is currently a prominent research area, due to the wide diversity and high effectiveness of a number of plant-borne compounds, with special reference to essential oils (EOs) extracted from medicinal and aromatic species. Here, we reviewed current knowledge available on EOs tested as repellents against tick species of veterinary importance. Furthermore, we analysed the effectiveness of pure compounds isolated from EOs as tick repellents and their potential implications for practical use in the öreal world". A quantitative analysis of literature available is this research field was provided, along with its impact (i.e., in terms of citations over time) on the scientific community of researchers in tick control science and natural product chemistry. In the final sections, future outlooks are highlighted. We discussed major challenges to stabilize the most effective EOs and pure molecules, explore the synergistic and antagonistic effects in blends of EOs and/or pure constituents, standardize currently adopted testing methods, and evaluate non-target risks of herbal repellents.

A PCR survey of vector-borne pathogens in different dog populations from Turkey

In the present study, a total of 192 blood samples were collected from pet dogs, kennel dogs and shepherd dogs in Konya district, Turkey, and tested by specific PCR for the presence of vector-borne pathogens. Several pathogens were identified, most of which can cause substantial morbidity in dogs. PCR results revealed that 54 (28.1%) dogs were infected with one or more pathogens. Positive results were obtained for Babesia spp. in 4 dogs (2.1%), Hepatozoon spp. in 8 dogs (4.2%) and Mycoplasma spp. in 46 dogs (24%). Three dogs (1.6%) were infected with two or three pathogens. The sequence analysis of the positive DNA samples revealed the presence of Babesia canis vogeli, Hepatozoon canis, Hepatozoon sp. MF, Mycoplasma haemocanis and Candidatus Mycoplasma haematoparvum. Ehrlichia canis and Anaplasma platys were not detected. Regardless of ownership status, vector-borne diseases were common in these dog populations. There was significant difference of pathogen prevalence among the different dog populations. Mycoplasma spp. was more frequent in the kennel dogs (31.9%) than in the pet (21.4%) and shepherd dogs (13.8%). Additionally, the frequency of Babesia spp. and Hepatozoon spp. was higher in the shepherd dogs which account for three quarters and half of the total number of Babesia spp. and Hepatozoon spp., respectively. To our knowledge, this is the first report of Mycoplasma infection in dogs in Turkey. The results of the present study provide a foundation for understanding the epidemiology of canine vector-borne diseases (CVBDs), and for strategies to control these diseases in Turkey.

[Heterogeneity of canine immune responses to Borrelia burgdorferi in a line immunoassay comprising recombinant VlsE and C6 peptide]

OBJECTIVE

The study aimed to investigate the distribution of specific immune responses (IgG) to Borrelia burgdorferi using a line immunoassay with recombinant VlsE (variable major protein-like sequence, expressed) protein and synthetic C peptide among other antigens. We compared the immune responses to VlsE protein and C₆ peptide, because both antigens have been considered specific for a Borrelia infection.

MATERIALS AND METHODS

A total of 1355 blood samples from dogs suspected of Borrelia infection were analysed. The line immunoassay employed nine antigens.

RESULTS

A total of 64.4% of all samples tested negative, 16.4% were positive for an infection and 17.4% were positive for vaccination. Band patterns specific for both infection and vaccination were observed in 1.2% of the dogs. The bands that most frequently tested positive were p100 (24.3%), p31/OspA (18.5%), C₆ (16.3%) and VlsE (13.9%). A total of 236 dogs (17.4% of the population) had antibodies to VlsE and/or C₆ peptide. In 73.3% of these dogs, results for VlsE and C₆ peptide were consistent, whereas this was not the case for 26.7% of these animals.

CONCLUSION AND CLINICAL RELEVANCE

Testing using a line immunoassay allows for qualitative analyses of different immune responses to various antigens used as probes. In our study, >  26% of the dogs displayed discrepant results with regard to VlsE and C₆, the two antigens considered specific for Borrelia burgdorferi infection. To confirm or rule out infection, the results of several band patterns, thought to be specific for infection, need to be taken into consideration.

A survey of canine haemoprotozoan parasites from Turkey, including molecular evidence of an unnamed Babesia

Canine tick-borne apicomplexan parasites have emerged in recent years, showing a wider geographic distribution and increased global prevalence. A reverse line blot assay was performed on 219 blood samples collected from domestic dogs for simultaneous detection of all named canine piroplasm species as well as Hepatozoon canis. Ten samples hybridized to the Theileria/Babesia and Babesia catch all probes but did not hybridize to any species-specific probe tested, suggesting the presence of an unrecognized Babesia species or genotype. Sequencing results showed 91.5%, 91.9%, 92.4%, 92.4%, and 89.2% similarity to B. canis, B. vogeli, B. rossi, B. gibsoni, and B. conradae, respectively. The highest homology (98.1-98.5%) observed was with unnamed Babesia sp. isolates (Ludhiana and Malbazar) described in dogs, Babesia sp. of buffalo origin, Babesia sp. Kashi 2, and Babesia orientalis, along with Babesia occultans of cattle origin. The partial cox1 sequence indicated that this isolate was most similar to Babesia sp. 1 HG-2012, with an identity of 86.5%. The survey revealed high prevalence of haemoprotozoans in domestic dogs (57.5%, CI 50.7-64.2), with Hepatozoon canis the most prevalent (54.3%, CI 47.5-61.117%), followed by Babesia sp. (4.6%, CI 2.2-8.2), B. vogeli (1.4%; CI 0.3-3.9), and B. canis (0.4%, CI 0-2.5). Combined infection of Hepatozoon canis and Babesia sp. was detected in five (2.3%, CI 0.7-5.2) samples and of H. canis and B. vogeli in two (0.9%, CI 0.1-3.2) dogs. The study contributes insight into the distribution and phylogenetic diversity of canine piroplasms in Turkey.

Confirmation of occurrence of <i>Babesia vogeli</i> in a dog in Windhoek, central Namibia

Although there is evidence of high seroprevalence of antibodies to Babesia spp. in dogs in central Namibia, clinical babesiosis is rarely diagnosed. Rhipicephalus sanguineus sensu lato, the vector of Babesia vogeli, is common in Namibia while Haemaphysalis elliptica, the vector of the highly virulent but morphologically indistinguishable Babesia rossi, has rarely been recorded, mainly in northern Namibia. On the basis of vector occurrence, clinical cases of canine babesiosis in Windhoek, central Namibia, have been ascribed to B. vogeli. DNA extracted from a blood smear made from a sick dog was subjected to the reverse line blot hybridisation assay. The polymerase chain reaction amplicons hybridised with the B. vogeli–specific probe, but not with the Babesia canis– and B. rossi–specific probes. Although attempts at cloning and sequencing of the full-length 18S rRNA gene were unsuccessful, we can confirm that B. vogeli occurs in central Namibia.

Vector-borne pathogens in dogs and red foxes from the federal state of Brandenburg, Germany

Dirofilaria repens is endemic in eastern and southern European regions but was recently found in Germany in dogs, mosquitoes and one human patient. Since some of the positive dog and mosquito samples were collected in Brandenburg, it was aimed to systematically assess the prevalence of D. repens and other canine vector-borne pathogens in Brandenburg. Dog owners also received a questionnaire and were asked to provide more information about the dogs including travel history. In total, 1023 dog blood samples as well as 195 fox spleen and 179 fox blood samples were collected. DNA was analysed by PCR for the presence of filariae, piroplasms, anaplasmataceae and Rickettsia spp. Filariae were detected in six dogs (0.6%), two were positive for DNA from D. repens, two from Dirofilaria immitis and two from Acanthocheilonema reconditum. One of the D. repens positive dogs originated from an animal shelter in Brandenburg, but the origin of the other one remained unknown. Interestingly, both D. repens ITS-1 sequences showed 100% identity to a D. repens sample obtained from a Japanese woman that travelled in Europe and were 97% identical to a newly proposed species Dirofilaria sp. 'hongkongensis' described from Hong Kong. However, identity to other D. repens sequences from Thailand was considerably lower (81%). Identity of 12S rRNA and cytochrome oxidase I to D. repens samples from southern Europe was 99%. Due to the low number of Dirofilaria spp. positive dogs and since the origin of these was unknown, endemic occurrence of Dirofilaria in Brandenburg could not be confirmed. Anaplasma phagocytophilum was found in 15 dogs (1.5%), Candidatus Neoehrlichia mikurensis in three dogs (0.3%) and E. canis in one dog (0.1%), which was co-infected with D. repens. Rickettsia spp. were detected in 8 dogs (0.8%), seven were Rickettsia raoultii and one was Rickettsia felis. To the author's knowledge, R. raoultii DNA was detected for the first time in dogs in Germany in this study and Candidatus N. mikurensis for the second time. In spleen samples of red foxes with 47.5% a high prevalence of piroplasms was found. Sequencing of 11 samples identified 10 as Theileria annae. Despite the high prevalence of this pathogen in its reservoir host, it was absent in dog samples. In one dog (0.1%), Babesia canis was detected but there was no further information about the dog's origin. Evaluation of the questionnaire identified a high proportion of dogs (74.2%, n=233) which was not protected by ectoparasiticides. Moreover, 21.2% (n=236) of the dogs originated from inland or abroad shelters, and therefore might potentially come from areas endemic for dirofilariosis or babesiosis.

Tick survey for prevalent pathogens in peri-urban recreation sites in Saarland and Rhineland-Palatinate (Germany)

Ixodid ticks are important vectors of human pathogens in Central Europe. Despite this fact, prevalence studies are scarce, especially with regard to much-frequented peri-urban recreation sites. In this pilot study, 4.014 larvae, nymphs and adult ticks sampled monthly during the active seasons in 2011 and 2012 from 14 distinct collection sites in two German states (Saarland and Rhineland-Palatinate) were screened for Borrelia spp., Anaplasma spp. and tick-borne encephalitis virus. Mean prevalence rates were 19.8 % for Borrelia spp., 1.9 % for Anaplasma spp. and 0.1 % for tick-borne encephalitis virus (TBEV), which are in accordance with those reported from other regions in Germany and neighbouring countries. Nevertheless, the detection of TBEV-infected ticks is the first positive result after several unsuccessful efforts over the previous years in official "TBE-risk" zones of Saarland and Rhineland-Palatinate which supports the presumption of the origin of observed local infection. Besides ixodid ticks a non-engorged adult female tick of the invading species Dermacentor reticulatus has been found reflecting the appearance of another vector eventually jeopardising the health of host animals as well as humans.

Detection of canine vector-borne diseases in eastern Poland by ELISA and PCR

The aim of the study was to establish the prevalence of Ehrlichia canis, Anaplasma phagocytophilum and Borrelia burgdorferi in dogs in eastern Poland and to determine the factors associated with exposure (seroposity) or infection (PCR). Anti-A. phagocytophilum, anti-B. burgdorferi and anti-E. canis antibodies were determined in 400 dogs, using the SNAP 4Dx ® test (IDEXX Laboratories). In addition, PCRs were performed for the detection of E. canis, A. phagocytophilum and B. burgdorferi DNA. In reference to the risk factor analysis, a regression logistic model was determined for each aetiological agent. The overall seroprevalence was highest for B. burgdorferi (11.0 %), followed by A. phagocytophilum (8.0 %) and E. canis (1.5 %). Eleven healthy dogs were found to be infected with A. phagocytophilum, as determined by PCR, while the remainder were seronegative. For B. burgdorferi, the DNA of the spirochetes was detected in the blood of 20 dogs, while the presence of anti-B. burgdorferi IgG was detected in the sera of ten of these. For E. canis, none of the dogs tested positive by PCR. Tick control was included as a protective factor for A. phagocytophilum and B. burgdorferi, while the origin (rural) was included as a risk factor for B. burgdorferi and A. phagocytophilum infection. In addition, breed (pure) was a risk factor for B. burgdorferi infection, and sex (female) was a risk factor for E. canis.

Anaplasma marginale and Anaplasma phagocytophilum: Rickettsiales pathogens of veterinary and public health significance

Anaplasma marginale and Anaplasma phagocytophilum are the most important tick-borne bacteria of veterinary and public health significance in the family Anaplasmataceae. The objective of current review is to provide knowledge on ecology and epidemiology of A. phagocytophilum and compare major similarities and differences of A. marginale and A. phagocytophilum. Bovine anaplasmosis is globally distributed tick-borne disease of livestock with great economic importance in cattle industry. A. phagocytophilum, a cosmopolitan zoonotic tick transmitted pathogen of wide mammalian hosts. The infection in domestic animals is generally referred as tick-borne fever. Concurrent infections exist in ticks, domestic and wild animals in same geographic area. All age groups are susceptible, but the prevalence increases with age. Movement of susceptible domestic animals from tick free non-endemic regions to disease endemic regions is the major risk factor of bovine anaplasmosis and tick-borne fever. Recreational activities or any other high-risk tick exposure habits as well as blood transfusion are important risk factors of human granulocytic anaplasmosis. After infection, individuals remain life-long carriers. Clinical anaplasmosis is usually diagnosed upon examination of stained blood smears. Generally, detection of serum antibodies followed by molecular diagnosis is usually recommended. There are problems of sensitivity and cross-reactivity with both the Anaplasma species during serological tests. Tetracyclines are the drugs of choice for treatment and elimination of anaplasmosis in animals and humans. Universal vaccine is not available for either A. marginale or A. phagocytophilum, effective against geographically diverse strains. Major control measures for bovine anaplasmosis and tick-borne fever include rearing of tick-resistant breeds, endemic stability, breeding Anaplasma-free herds, identification of regional vectors, domestic/wild reservoirs and control, habitat modification, biological control, chemotherapy, and vaccinations (anaplasmosis and/or tick vaccination). Minimizing the tick exposure activities, identification and control of reservoirs are important control measures for human granulocytic anaplasmosis.