Histochemical differentiation of Dirofilaria immitis, Dirofilaria repens and Acanthocheilonema dracunculoides microfilariae by staining with a commercial kit, Leucognost-SP

Microfilaremic infection in canine filariosis in Colombia: a challenge in morphological and molecular diagnostics

Canine filariosis is caused by filiform nematodes and affects several species of animals as well as humans. The disease produces a wide range of symptoms that can often be confused with other diseases, which increases the complexity of its diagnosis. The search for methodologies to facilitate its diagnosis is a challenge, and specific and differential identification of the parasite species causing the disease holds key to a successful diagnosis. In Colombia, there is a problem of underdiagnosis of filariosis in microfilaremic dogs infected by Dirofilaria immitis and Acanthocheilonema reconditum, and of microfilaremias not related to heartworm disease. The highest prevalences have been reported for D. immitis infections, although new cases of A. reconditum infections are beginning to appear. The aim of this study was to differentiate the microfilariae infections caused by D. immitis and A. reconditum by a morphological and molecular characterization of microfilariae so as to facilitate an accurate diagnosis of canine filariosis in the metropolitan area of Bucaramanga (Colombia). For this purpose, 400 blood samples with anticoagulants were collected from the dogs and analyzed with the help of a commercial immunochromatography kit for the detection of D. immitis circulating antigen. The Woo, Knott, and polymerase chain reaction (PCR) techniques were employed for determining the parasite count, morphological observation, and molecular identification of microfilariae present in the dogs respectively. The prevalence of microfilaremic dogs in Bucaramanga metropolitan area was 18.75% (75/400). The prevalence of dogs that tested positive for D. immitis in the antigen and in PCR tests was 1.25% (5/400) and 1% (4/400), respectively. Furthermore, the PCR test revealed that 17.75% of the microfilaremic dogs tested positive for A. reconditum (71/400) (first report in the metropolitan area of Bucaramanga), with one animal co-infected by both species, and 0% for D. repens (0/400). However, by morphological characterization, 4% of the microfilariae (3/75) corresponded to D. immitis, 20% (15/75) to D. repens, and 76% (57/75) to A. reconditum. The use of molecular diagnostic methods such as PCR aids in the specific identification of the parasite, thus making it a more accurate method than the morphological characterization of microfilariae. The identification of the parasites by PCR helps improve the veterinary diagnosis of canine filariosis in Colombia, which would lead to the establishment of an appropriate treatment protocol for each species of filaria and also to the generation of reliable data to be used at the clinical and epidemiological levels.

Cutaneous filarioid nematodes of dogs in the United States: Are they emerging, neglected, or underdiagnosed parasites?

Filarioid nematodes, which are vector-borne parasites of cosmopolitan distribution, of dogs are medically important. They are represented by species in which microfilariae were found to be circulating in the bloodstream (e.g., Dirofilaria sp., Acanthocheilonema sp., and Brugia sp.) or skin-dwelling (e.g., Cercopithifilaria sp. and Onchocerca sp.). Those species whose microfilariae are detected in blood have been extensively studied, especially Dirofilaria immitis, due to their clinical importance. In recent decades, there has been an increased interest by the scientific community in filarioid nematodes whose microfilariae are detected in the skin because of the zoonotic aspect of Onchocerca lupi. In the United States (US), although D. immitis has been considered the main filarioid infecting dogs, the intense animal movement and global canine filarioid diversity may indicate that the likely presence of cutaneous filarioid nematodes is more common than previously expected. Hence, a question remains: Are these canine filarioid nematodes emerging, neglected, or simply underdiagnosed in the US? In this review, we provide an overview of pertinent information that briefly summarizes the biology of the different canine filarioid nematode species, clinical signs associated with infections, and currently available diagnostic tools using molecular and microscopy-based methods and highlight knowledge gaps where research and surveillance efforts remain necessary. The data herein presented serve as an alert to the scientific community about the importance of filarioid nematodes infecting dogs other than D. immitis. Additionally, the zoonotic potential of several filarioid species reinforces the necessity of a proper diagnosis and the need for broader surveillance to understand their diversity and distribution, to highlight the potential introduction of certain species, and mitigate their establishment in the country and new animal and human cases.

Refrigerated modified Knott concentrate enables long-term morphological viability of canine blood microfilariae

There are several methods of laboratory diagnosis of filarids, the most used are the thick smear and the Knott method. Both are quick to perform, have a low cost and allow observing the presence, quantifying and analyzing the morphological characteristics of microfilariae. Knowing the morphological viability of fixed microfilariae is of practical importance, as it allows the transport of samples to a laboratory, facilitates epidemiological studies , and allows the storage of samples for didactic. Thus, the aim of this study was to evaluate the morphological viability of microfilariae fixed in the refrigerated modified knott test using 2% formalin. To perform the modified Knott technique, 10 samples of microfilaremic dogs aged over 6 months were used. To evaluate the morphological viability time of the microfilariae in the modified Knott concentrate, the evaluations were repeated after intervals of 0, 1, 7, 30, 60, 120, 180, 240, and 304 days. In the present study, we did not verify any difference in the morphology of the microfilariae in any of the analyzed intervals from day 0 to 304 days, and it is possible to conclude that the use of 2% formalin in the modified Knott technique allows the microfilariae to be identified in a period of 304 days. days after processing the sample without changes in its morphology.

Estimated specific antibody-based true sero-prevalences of canine filariosis in dogs in Central Europe and the UK

Dirofilariosis is a vector-borne disease mainly caused by Dirofilaria immitis and Dirofilaria repens. In contrast to the known endemicity of dirofilariosis in southern and south-eastern Europe, information on the distribution of D. repens in Central-Europe is fragmentary. We tested 8877 serum samples from dogs from Austria, Denmark, Germany, Italy, Lithuania, Poland, Switzerland and the UK using an ELISA detecting filarial-specific antibodies, hypothesising higher occurrence of D. repens. Based on two overlapping frequency distributions, presumed negative samples had a mean optical density (OD) value of 0.097, representing 97.45% of all samples. Presumed positive samples, representing 2.55% of all sera, had a mean OD value of 0.287. Test prevalence based on the calculated cut-off was 3.51% for all sera (4.36% for Austria, 1.94% for Denmark, 1.39% for Germany, 3.37% for Italy, 6.90% for Lithuania, 6.99% for Poland, 0.77% for Switzerland and 0.0% for the UK, respectively). The bimodal distribution, representing overlapping distributions of OD values from positive and negative dogs, enabled the assignment of a probability of true infection status to each dog. Mean probabilities of true infection status across groups, based on the postal codes of origin, allowed us to estimate and map true prevalences. For all countries, except the UK, the true prevalence was lower than the test prevalence. The large number of serum samples and the use of a non-gold standard analytical method allowed us to create a more realistic picture of the distribution of D. repens in Central Europe and the UK.

Granuloma caused by Acanthocheilonema spp. in a canine - case report

ABSTRACT A canine patient, 13-year-old mixed breed male, 24kg, was seen at a private clinic in the city of Guayaquil, Ecuador. The main reason for consultation was the evaluation of a mass in the right knee and neck that had previously been cytologically diagnosed of neoplastic origin by another team of veterinarians through fine needle puncture and cytology. The contacts were asymptomatic. At the time of the consultation, a detailed exploration and complementary methods were performed that included hematological and urinary exams, mass cytology, serological test, chest radiography and biopsy for further histopathological study. The final diagnosis was a cutaneous granuloma due to microfilariae of Acanthocheilonema spp. and its subsequent surgical and medical treatment with excellent results. The canine heartworm is a cosmopolitan disease caused by nematodes of the genus Dirofilaria, with D. immitis being the best-known species. Less frequently, the species Acanthocheilonema spp., found in this patient, is also reported in Americas, with little knowledge about it. This is the first report of its kind hoping that it will serve as a basis for future studies.

Selection of new diagnostic markers for Dirofilaria repens infections with the use of phage display technology

Dirofilaria repens is a parasitic nematode causing vector-borne disease (dirofilariasis), considered an emerging problem in veterinary and human medicine. Although main hosts are carnivores, particularly dogs, D. repens shows high zoonotic potential. The disease spreads uncontrollably, affecting new areas. Since there is no vaccine against dirofilariasis, the only way to limit disease transmission is an early diagnosis. Currently, diagnosis depends on the detection of microfilariae in the host bloodstream using modified Knott's test or multiplex PCR. However, the efficacy of tests relying on microfilariae detection is limited by microfilariae periodic occurrence. Therefore, a new reliable diagnostic test is required. Our study aimed to select new diagnostic markers for dirofilariasis with potential application in diagnostics. We focused on single epitopes to ensure high specificity of diagnosis and avoid cross-reactivity with the other parasite infections common in dogs. Using phage display technology and 12-mer peptides library, we selected epitopes highly reactive with IgG from sera of infected dogs. Additionally, our study presents the possibility of detecting D. repens specific cell-free DNA in dogs with no microfilaria but high IgG and IgM antibody levels against parasite somatic antigen.

False positive antigen test for Dirofilaria immitis after heat treatment of the blood sample in a microfilaremic dog infected with Acanthocheilonema dracunculoides

Background

Dirofilaria immitis is responsible for heartworm disease in dogs in endemic areas worldwide. Screening for this infection is done by blood tests. Antigen testing is the most sensitive method to detect an infection with adult (female) worms. Microscopic examination of a blood smear or Knott’s test can be used to detect circulating microfilariae, the infective larvae. To increase the sensitivity of the antigen test by decreasing the false negative test results, heating of the blood sample has been recommended in recent guidelines. Heating is believed to remove blocking immune-complexes. Circulating microfilariae are not specific findings for heartworm infection, as other nematodes (among others, Acanthocheilonema dracunculoides) can also result in microfilaremia. Although the type of microfilariae cannot be determined by microscopy alone, real-time PCR can reliably identify the infecting nematode species. Correct identification of the parasite is of major importance, as an infection with D. immitis requires antiparasitic therapy, whereas A. dracunculoides is thought to be a clinically irrelevant coincidental finding. The present case report describes a microfilaremic dog where the initial antigen test for D. immitis turned positive after heat treatment, whereas real-time PCR revealed that the microfilariae were A. dracunculoides (syn. Dipetalonema dracunculoides).

Results

A circa 5-year old, asymptomatic Spanish mastiff dog was referred for heartworm therapy because microfilariae were found via a screening blood test. The dog was recently imported to the Netherlands from Spain, where it had been a stray dog. Antigen tests on a plasma sample for D. immitis were performed with three different test kits, which all turned out to be negative. However, heat treatment of two of these samples were carried out and both of them led to a positive antigen test result. Real-time PCR showed that the circulating microfilariae belonged to A. dracunculoides species. Three administrations of moxidectin spot-on at monthly intervals resulted in a negative antigen and a negative Knott’s tests one month after the last treatment.

Conclusions

We conclude that heat treatment of initially negative blood samples for D. immitis could lead to false positive antigen test results if the dog is infected with A. dracunculoides.

Heartworm on the rise-new insights into Dirofilaria immitis epidemiology

Until recently Dirofilaria immitis, the causative agent of serious canine heartworm disease, has been detected relatively infrequently in Central Europe in comparison with the predominant D. repens species. In the present study, the elevated number of heartworm cases among dogs from a breeding establishment in south-western Slovakia is described. Out of 25 dogs examined, dirofilariasis was detected by single or several diagnostic approaches in 18 animals, which represents a mean prevalence of 72.0%. D. immitis was confirmed in 16 (64.0%) of the infected dogs and D. repens in 8 dogs (32.0%). All cases of D. immitis infection were detected in areas regarded as D. repens-endemic to date. Following the presented results and discussed circumstances, the question of whether the real prevalence of canine heartworm disease in Slovakia, or even in Central Europe as a whole, has been underestimated, or if D. immitis is currently becoming endemic in this area.

Prime detection of Dirofilaria immitis: understanding the influence of blocked antigen on heartworm test performance

Detection of circulating antigen of Dirofilaria immitis has been a mainstay of identifying heartworm infection in clinical practice for the past three decades. Several validated commercial antigen tests have very good sensitivity, specificity, and positive predictive values, especially when used in patients for which heartworm infection is likely. In some dogs and cats infected with heartworm, antigen may not be available for detection although present in the patient sample; heat pretreatment of these samples reveals the antigen, changing the false negative to positive. This phenomenon was documented in the literature in the 1980s but subsequently overlooked by the heartworm research community for many years. In this review, we provide a summary of the current understanding of the role of heat reversal in diagnosing heartworm infection. This additional diagnostic step is most important for patients in which heartworm infection is likely, such as dogs or cats in an endemic area with an inconsistent history of heartworm preventive use, or dogs with a prior diagnosis of heartworm infection that were recently treated. To illustrate the concept, we share a summary of results from canine samples tested at the state veterinary diagnostic laboratory in Oklahoma, USA in 2017 by modified Knott test and by commercial antigen test before and after heat treatment of samples; in this sample set, heat treatment changed all D. immitis microfilaria-positive but antigen-negative samples to antigen-positive. Pet dogs with a history of consistent preventive use are unlikely to become positive with heat pretreatment; for that reason, routine pretreatment of all samples tested in a veterinary practice is not recommended. We also review known causes of false negative and false positive results on heartworm antigen tests that, although uncommon, can complicate accurate diagnosis in individual patients. Together, this review provides a primer to aid understanding of strategies that can enhance accurate diagnosis of heartworm infection in veterinary practice and clinical research.

Filarial nematodes with zoonotic potential in ring-tailed coatis (Nasua nasua Linnaeus, 1766, Carnivora: Procyonidae) and domestic dogs from Iguaçu National Park, Brazil

Iguaçu National Park, which contains the largest remnant of Atlantic Forest in southern Brazil and Iguaçu Falls as one of its main visiting points, is a year-round attraction for thousands of domestic and international tourists. Ring-tailed coatis are generalist, opportunistic carnivores that benefit from human association. These animals are the most abundant carnivores in this park, where they come into close contact with tourists and the resident population around the park. Moreover, as the park is surrounded by human dwellings, free roaming domestic dogs are frequently present, favoring the exchange of pathogens with wild animals. Wild carnivores are known to be infected with several pathogens, from viruses to arthropods, some of them passed on by domestic carnivores. Among the nematodes that infect wild carnivores, those of the Onchocercidae family are of concern due to their zoonotic potential. The objective of this research was to assess the prevalence of filarial nematodes in coatis and dogs in Iguaçu National Park, as well as the potential impact of infection on host health and body condition. To this end, 75 coatis and 50 adult dogs were captured in the aforementioned area. Seven species of filarioids, Dirofilaria immitis, Dirofilaria repens, Acanthocheilonema reconditum, Brugia sp., Mansonella sp. and two undetermined species, confirmed by histochemical tests, were diagnosed in the area. Knott's concentration test in coatis and dogs showed a prevalence of 81.6% and 16.0%, respectively. Seven microfilarial morphotypes were diagnosed in the coatis and two morphotypes were found in the dogs. A specific immunoassay test for Dirofilaria immitis revealed the presence of D. immitis infection in 1.33% of the coatis and 22% of the domestic dogs. The parasitic infection had negligible effects on the body condition of both dog and coati hosts, but an increase was found in eosinophil counts in coatis with filarial infection, as well as decreases in hematocrit and hemoglobin in the infected domestic dogs. These findings represent new locality and host records for all the filarioids diagnosed in the area of this study, with some of the diagnosed parasites, given their zoonotic potential, representing a health risk for park visitors and the local population.

Major Parasitic Zoonoses Associated with Dogs and Cats in Europe

Some of the most important zoonotic infectious diseases are associated with parasites transmitted from companion animals to man. This review describes the main parasitic zoonoses in Europe related to dogs and cats, with particular emphasis on their current epidemiology. Toxoplasmosis, leishmaniosis, giardiosis, echinococcosis, dirofilariosis and toxocariosis are described from the animal, as well as from the human host perspectives, with an emphasis on parasite life cycle, transmission, pathogenicity, prevention and identification of knowledge gaps. In addition, priorities for research and intervention in order to decrease the risks and burden of these diseases are presented. Preventing zoonotic parasitic infections requires an integrated multidisciplinary 'One Health' approach involving collaboration between veterinary and medical scientists, policy makers and public health officials.

Prevalence and seasonal variations of canine dirofilariosis in Portugal

Dirofilariosis is a severe vector-borne emergent disease that is spreading worldwide and becoming a serious threat to human and veterinary public health. Portugal, a Mediterranean country, has favorable climate conditions for mosquito development and survival. At present, accurate data on the prevalence and epidemiological pattern of dirofilariosis in Portugal is scarce and outdated. To study these trends, a project was developed to assess the current prevalence of Dirofilaria immitis infection in shelter dogs as well as the prevalence of Dirofilaria species present in three coastal regions in central Portugal: Coimbra, Santarém, and Setúbal. Blood samples were collected from 696 shelter dogs during three consecutive years: 2011, 2012, and 2013. A rapid immunomigration technique was performed to detect female D. immitis antigens. Concurrently, to detect and identify circulating microfilariae, a modified Knott's technique and acid phosphatase histochemical staining were also performed. Of the 696 dogs sampled, 105 were positive for D. immitis, with an overall prevalence of 15.1%. Forty of the 105 dogs were antigen negative but were positive for D. immitis microfilariae. Three animals were co-infected with D. immitis and Acanthocheilonema dracunculoides, and there was also one dog infected only with A. dracunculoides, all confirmed by polymerase chain reaction. The highest prevalence of canine heartworm during the 3-y period was in Setúbal (24.8%), followed by Coimbra (13.8%), and Santarém (13.2%), with significant inter-district differences. Our results demonstrate a higher prevalence of dirofilariosis compared with findings of previous studies and show an increasing rate of infection in the southern areas of Portugal attributed, at least in part, to bioclimatic and ecological factors. The present study updates the epidemiological situation and correlates the risk of dirofilariosis transmission within each region. These findings are highly relevant to both human and veterinary public health, contributing to the general awareness of pet owners and veterinarian practitioners and reinforcing the need for effective control measures against vectors and preventive therapy in companion animals.

Prevalence of canine heartworm (Dirofilaria immitis) disease in dogs of central Portugal

The aim of the present study was to determine the prevalence and risk factors concerning Dirofilaria immitis infection in dogs from Figueira da Foz, located in the central region of Portugal. In the period between November 2009 and January 2011, 304 blood samples were obtained from dogs over 1 year of age, with no previous history of heartworm prevention or diagnosis. Every blood sample was analyzed using varied laboratory techniques (direct microscopic evaluation of a fresh blood sample, the modified Knott technique, and the ELISA antigen detection test - IDEXX Snapp®). In the samples in which microfilaremia was detected, a histochemical technique using acid phosphatase staining was applied to identify the species of microfilariae. A total prevalence of 27.3% (83 out of 304) was found. We also found that 73.5% of all positive cases (61 out of 83) were microfilaremic, and 26.5% were occult infections (22 out of 83). By means of a histochemical technique Dirofilaria immitis was identified in 96.7% of microfilaremic samples. A multivariate model allowed us to identify the following risk factors for the presence of heartworm disease: age between 4 and 9 years, dogs living in a rural environment, large breed dogs, and living outdoors. This study shows for the first time the high prevalence of heartworm disease in a central area of Portugal and emphasizes the importance of systematic screening for this disease, as well as the need to prevent it in dogs in this area.

Morphometric analyses of canine blood microfilariae isolated by the Knott's test enables Dirofilaria immitis and D. repens species-specific and Acanthocheilonema (syn. Dipetalonema) genus-specific diagnosis

Background

Considering the increasing importance of small animals travel medicine and the spread of filariae with zoonotic potential to non-endemic European areas, routine filarial diagnosis in dogs is becoming important. Dirofilaria immitis, D. repens, Acanthocheilonema dracunculoides and A. reconditum are the most common canine filarial nematodes presenting blood circulating microfilariae (mf) which can be differentiated to species level by the acid phosphatase activity patterns or by PCR. Available data on the size of the mf vary considerably in the literature. The aim of this study was to validate morphometric criteria for filarial identification in blood samples of dogs after concentration of mf with the modified Knott’s technique.

Methods

Morphometric analysis of 10 mf from samples identified to species level by acid phosphatase activity and partially confirmed by PCR were performed with specimens from 377 dogs.

Results

The mean length and width of D. immitis mf from 60 dogs were 301.77±6.29 μm and 6.30±0.26 μm, of D. repens mf from 171 dogs 369.44±10.76 μm 8.87±0.58 μm, of A. dracunculoides mf from 133 dogs 259.43±6.69 μm and 5.09±0.47 μm and of A. reconditum mf from 13 dogs 264.83±5.47 μm and 4.63±0.52 μm.

For a subset of 30 samples, morphometric analysis was repeated with identical results in two laboratories. Furthermore, the size of mf concentrated and fixed by the Knott’s technique was shown to be stable over 105 days.

Conclusions

The Knott’s test enables to clearly distinguish between D. immitis, D. repens and Acanthocheilonema spp. However, due to the overlapping size ranges of A. dracunculoides and A. reconditum, biochemical or molecular methods are required to distinguish these two species.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

A multiplex PCR for the simultaneous detection of species of filarioids infesting dogs

The present study reports the applicability of a multiplex PCR for the simultaneous detection and differentiation of common filarioids infecting dogs, i.e., Dirofilaria immitis, Dirofilaria repens, Acanthocheilonema reconditum and Cercopithifilaria sp. Amplicons of different sizes (i.e., 170 bp, 480 bp, 590 bp and 300 bp, respectively) of regions within the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene were amplified on a single-step multiplex PCR using a mix of species-specific forward primers coupled with a single reverse primer. Experiments were carried out by amplifying genomic DNA extracted from blood or skin samples test-positive for microfilariae (mff). The number of mff present in each blood sample was quantified (from 800 to 25,000 mff/ml for A. reconditum and D. repens, respectively) and mixed blood samples were tested for the simultaneous detection of DNA from these mff. Specific amplicons for blood-circulating mff of A. reconditum, D. immitis and D. repens and for those whose adults are localized in skin (i.e., A. reconditum and Cercopithifilaria sp.) were simultaneously detected on agarose gel up to a dilution of 250 mff/ml for D. repens. The specific identity of the amplicons was confirmed by sequencing. The multiplex PCR assay reported herein represents a new tool for the molecular detection and differentiation of canine filarioids in blood and skin samples.

Effect of therapy by using advocate spot-on combination (imidacloprid 10% and moxidectin 2.5%) on subcutaneous dirofilariosis in dogs

Dirofilaria (Nochtiella) repens is a filarioid parasite that causes subcutaneous dirofilariosis in dogs. Adults, while localized in subcutaneous tissues, lay embryos (microfilariae (mf)) into the blood stream of dogs, which constitute a reservoir for infection of other definitive or accidental hosts as humans. This study was carried out to assess the efficacy of spot-on combination of imidacloprid and moxidectin on microfilariaemia in naturally infected dogs. A group of 11 dogs was monthly examined for the presence of microfilariae in peripheral blood by modified Knott's test method. Treatment was administered monthly for 4 months. All dogs (i.e., 100%) became negative for microfilariaemia throughout the study. These results confirm the effect of the combination of imidacloprid and moxidectin on D. (Nochtiella) repens.

A Survey on Dirofilaria immitis Occurence in Stray Dogs of Tabriz (Iran)

To determine the prevalence of microfilariae Dirofilaria immitis (canine heart worm) infection in Tabriz (East-Azarbaijan province, Iran), blood samples from 63 male and 37 female stray dogs of six age groups (< 1 years, 1-3 years, 3-5 years, 5-7 years, 7-9 years and > 9 years) were analyzed by means of the Knott method. Dirofilaria immitis infection was found in 30 of 100 tested dogs (30%). Male dogs (33.3%) were more infected than females (24.3%), but this difference was not significant. Higher prevalence was found in > 9 years old dogs than in other age groups, but this difference was not statistically significant. It would be useful to apply prevention measures to control Dirofilaria immitis infection in the canine population of Tabriz.

A survey of canine filarial diseases of veterinary and public health significance in India

BACKGROUND

Dirofilaria spp., Acanthocheilonema spp. and Brugia spp. have all been reported in Indian dogs. In previous studies, diagnosis was made by morphological identification only. This is the first geographically stratified cross-sectional study in India to determine the prevalence and geographical distribution of canine filarial species of veterinary and public health importance, using a combination of conventional and molecular diagnostic techniques.

RESULTS

A total of 139 from 525 dogs (26.5%; 95% CI 22.7, 30.3) were positive for microfilariae. The most common species of canine filaria identified in this study was A. reconditum (9.3%) followed by D. repens (6.7%) and D. immitis (1.5%). Three out of 525 dogs were found to have mixed infections on PCR. The morphological and molecular evidence on the sequence of the 18S gene and phylogenetic analysis of the ITS-2 region provided strong evidence that the canine microfilariae discovered in the Himalayan city of Ladakh belong to a novel species of Acanthocheilonema. Two dogs in Ladakh were also found to have mixed infections of the novel species described above and a unique microfilaria which morphologically resembled Microfilaria auquieri Foley, 1921.

CONCLUSIONS

At least six species of filarial nematode are now known to infect dogs in India, two of which were reported for the first time in this study. The study also confirms and extends the geographical distribution of canine heartworm (D. immitis) which overlaps with D. repens, emphasising the importance for veterinary clinicians and diagnostic laboratories to utilise immunodiagnostic tests that will not cross-react between those two filarial species. From a public health viewpoint, the distribution and prevalences of these nematodes warrant an appropriate prophylaxis to be administered to dogs.

Dirofilaria infections in working dogs in Slovakia

A monitoring programme aimed at the diagnosis of subcutaneous dirofilariasis and heartworm disease in working (police and military) dogs in Slovakia has been performed during the period of September 2007 to February 2008. In co-operation with the Ministry of the Interior and the Ministry of Defence, in total, 710 dogs (591 police dogs and 119 military dogs) were investigated for the presence of microfilariae in blood. All police and military dogs in active service held on the territory of Slovakia were included. Microfilariae were detected in 118 (20.0%) police dogs and 10 (8.4%) military dogs. The most infected individuals originated from southern parts of Slovakia (Trnava region 53.6% and Nitra region 39.6%); the prevalence was low in northern regions (Zilina 3.1% and Presov 6.6%). In several districts of southern Slovakia, the prevalence of subcutaneous dirofilariasis in working dogs exceeded 40%. In all infected animals, the autochthonous origin of the disease was confirmed; however, due to the frequent movement of working dogs, it was not possible to identify the exact locality of infection. At present, a dog living in Nemsová village in Trencín district (north-western part of the country) is regarded as the northernmost localized autochthonous case of subcutaneous dirofilariasis in Slovakia. In three dogs, co-infection of Dirofilaria repens and Dirofilaria immitis was detected. High prevalence rates in working dogs and the zoonotic characteristic of the disease represent an undoubtedly important veterinary and medical problem that requires the urgent introduction of prophylactic and control measures.

Heartworm disease in animals and humans

Heartworm disease due to Dirofilaria immitis continues to cause severe disease and even death in dogs and other animals in many parts of the world, even though safe, highly effective and convenient preventatives have been available for the past two decades. Moreover, the parasite and vector mosquitoes continue to spread into areas where they have not been reported previously. Heartworm societies have been established in the USA and Japan and the First European Dirofilaria Days (FEDD) Conference was held in Zagreb, Croatia, in February of 2007. These organizations promote awareness, encourage research and provide updated guidelines for the diagnosis, treatment and prevention of heartworm disease. The chapter begins with a review of the biology and life cycle of the parasite. It continues with the prevalence and distribution of the disease in domestic and wild animals, with emphasis on more recent data on the spreading of the disease and the use of molecular biology techniques in vector studies. The section on pathogenesis and immunology also includes a discussion of the current knowledge of the potential role of the Wolbachia endosymbiont in inflammatory and immune responses to D. immitis infection, diagnostic use of specific immune responses to the bacteria, immunomodulatory activity and antibiotic treatment of infected animals. Canine, feline and ferret heartworm disease are updated with regard to the clinical presentation, diagnosis, prevention, therapy and management of the disease, with special emphasis on the recently described Heartworm Associated Respiratory Disease (HARD) Syndrome in cats. The section devoted to heartworm infection in humans also includes notes on other epizootic filariae, particularly D. repens in humans in Europe. The chapter concludes with a discussion on emerging strategies in heartworm treatment and control, highlighting the potential role of tetracycline antibiotics in adulticidal therapy.

Prevalence and epidemiological aspects of Dirofilaria immitis in dogs from Kayseri Province, Turkey

This study was conducted to determine the prevalence of Dirofilaria immitis infection and to investigate the risk factors related to heartworm disease in dogs from Kayseri, Turkey. Blood samples were collected from 280 dogs from May 2005 to March 2006 and were examined by membrane filtration-acid phosphatase histochemical staining and antigen Elisa techniques to detect circulating microfilariae and antigens of D. immitis, respectively. Of the total of 280 dogs, 27 were positive for D. immitis with a prevalence value of 9.6%. In addition 29.6% of positive dogs determined to have occult D. immitis infections. D. immitis was the only canine filarial parasite present in the study area. The mean number of microfilariae in infected dogs was 4730+/-5479 per ml of blood. The highest heartworm prevalence were observed in 7-10 age group (28.6%) followed by 4-6 (17.1%) and 0.5-3 (4.8%) age groups. The differences between 0.5-3 and other age groups were found significant, whereas no statistically significant difference was observed between 4-6 and 7-10 age groups. The infection was more prevalent in males, larger breeds and the dogs not on prophylaxis. No statistically significant difference was observed between stray and owned dogs. Our results suggest that heartworm treatment and prophylaxis should be considered in Kayseri Province.

A simple molecular method for discriminating common filarial nematodes of dogs (Canis familiaris)

Accurate diagnosis of canine filariosis is essential for choosing correct therapeutic approach. Therefore, reliable methods for discriminating among the different filarial infections in dogs are needed. The authors report simple and highly specific molecular methods that identify the three most common filarial nematodes of European dogs: Dirofilaria immitis, D. repens and Acanthocheilonema (syn. Dipetalonema) reconditum, based on (1) PCR amplifications of mitochondrial DNA (12S rDNA and coxI) with general filarial primers followed by digestion with restriction enzymes that generates band polymorphisms clearly discriminating the three species and (2) PCR amplifications with species-specific primers to support the restriction analysis, in particular in the case of multiple infections.

Comparison of the Acid-phosphatase Staining and Polymerase Chain Reaction for Detection of Dirofilaria repens Infection in Dogs in Korea

This study was performed to compare acid-phosphatase staining with polymerase chain reaction (PCR) analysis for the diagnosis of Dirofilaria repens infection. The infection of D. repens was confirmed in Korean reared German shepherd dogs. Knott's tests were carried out for the detection of microfilaria in 543 Korean reared German shepherd dogs (255 females and 288 males). Eighty four of the 543 dogs (15.5%) showed microfilaria-positive reactions with the modified Knott's test, and the test-positive microfilariae were then examined by both acid phosphatase staining and PCR analysis. Six (7.1%) and 17 (20.2%) of the 84 microfilaria-positive samples, by the Knott's tests were positive to D. repens by acid-phosphatase staining and in D. repens-specific PCR analysis, respectively. All samples found to be positive by the acid-phosphatase staining were also found to be positive by PCR analysis. Therefore, we conclude that PCR analysis (20.2%) is more valuable for the diagnosis of D. repens infection than acid-phosphatase staining (7.1%) (p<0.001).

Setaria equina infection of Turkish equines: estimates of prevalence based on necropsy and the detection of microfilaraemia

Necropsies on 43 horses, 35 donkeys and two mules slaughtered in Ankara, Turkey, revealed that 12 (15%) of the equines harboured adult Setaria equina. When blood samples were checked for microfilariae, using Knott's method and a combination of membrane filtration followed by histochemical staining for acid phosphatase (AP), only three (4%) of the animals were found to be microfilaraemic. When stained for AP, the S. equina microfilariae exhibited diffuse red staining over the entire body, including the sheath, with brighter staining around the anal and excretory pores. Application of Knott's method revealed only two of the three microfilaraemias detected using the combination of filtration and AP staining. The combination may represent a useful technique for the detection of equine microfilaraemia.