Canine Heartworm Research Articles

Comparative performance analysis of different microfilaria testing methods for Dirofilaria immitis in canine blood.

Microfilaria (MF) testing is an essential part of canine heartworm diagnostics, and it is recommended by the American Heartworm Society that a MF test be performed in tandem with antigen testing on every dog, every year, regardless of prevention status or history. There are a variety of methods that can be used to detect MF in canine whole blood; however, these methods widely vary in their sensitivities as well as practical factors, including time investment and cost. Additionally, some MF tests offer the advantage of being quantitative or allowing for morphological or molecular species identification, while other tests should only be used qualitatively. The purpose of this study is to evaluate the quantitative and qualitative performance of MF tests, including the 20μL count, wet mount, 9μL and 40μL hematocrit tubes, thin smear, thick smear, modified Knott test (MKT), and conventional polymerase chain reaction (PCR). Qualitatively, there was little difference in the performance of the 20μL count, wet mount, MKT, and PCR. The MKT and PCR are the optimal MF tests, as these perform most reliably for detecting positives even when the MF per milliliter is relatively low, and in most cases, these two methods also allow for species-level confirmation of the identity. However, PCR tends to be a very costly test, and both PCR and MKT require a greater degree of expertise and time investment to perform than other tests. Even the lowest performance tests, including the thin smear and hematocrit tube methods, can reliably detect MF at very high burdens; although, caution should be advised when using low reliability methods, since there is a greater likelihood of failing to identify MF-positive dogs. Microfilaria (MF) testing is an essential part of heartworm diagnosis and screening in dogs, and test selection should balance practical factors such as cost and time investment with the patient's risk of infection based on prevention status and history, clinical signs, and antigen testing results. This approach to MF testing will help minimize cost while avoiding failure to detect MF in infected dogs, especially when MF burden is low.

Efficacy of Sustained-Release Formulation of Moxidectin (Guardian SR) in Preventing Heartworm Infection over 18 Months in Dogs Living in a Hyperendemic Area.

This study investigates the efficacy of a sustained-release (SR) moxidectin microsphere formulation in preventing canine heartworm infection over 18 months in Canary Hound dogs, a hunting breed common in the Canary Islands, which is a hyperendemic region. These dogs typically do not receive preventive treatments and act as reservoirs for the disease. This field study was conducted across 11 hunting kennels with 109 dogs living outdoors, none of whom were receiving heartworm prophylaxis, with Dirofilaria immitis prevalence ranging from 11.1% to 57.1% (average 36.7%). Among these, 20 clinically healthy, heartworm-negative dogs were randomly selected to receive a single subcutaneous injection of moxidectin SR (0.17 mg/kg body weight). Antigen and Knott's tests were performed at 6, 12, 18, and 24 months. All dogs completed the study without adverse reactions and remained heartworm-negative throughout. By the end of the study, kennel heartworm prevalence ranged from 14.3% to 46.7% (average 35.4%). A single subcutaneous dose of moxidectin SR at the recommended dosage may prevent patent heartworm infection in dogs for up to 18 months in hyperendemic regions. Further studies are required to confirm these findings. Extending the efficacy period of moxidectin could improve owner compliance, particularly among those with lower animal health awareness.

'Transmission Tracker - Dirofilaria'- a public dashboard to assess in real-time the temperature-bounded transmissibility of canine heartworm across Australia.

The causative agent of canine heartworm disease, Dirofilaria immitis, requires specific temperature conditions to mature within its mosquito vector, and therefore (re-)infect a canid host. Suitable temperature conditions are not continuously met for locations where most (>97%) Australians and their pet dogs live. The length of the disruption in the transmissibility of D. immitis varies greatly across Australia, and to some degree, between years. We developed an online dashboard 'Transmission Tracker - Dirofilaria' that processes near real-time temperature records across Australia and allows users to enquire about historical and current weather suitability for canine heartworm transmission at any Australian postcode of their interest. This information allows veterinarians to access when, and for how long, heartworm may be transmitted at a specific location, assess the associated risk of infection and advise on a patient-dependent dirofilariosis prevention plan for their canine patients and guardians. Our dashboard is publicly accessible at: https://heartworm-mapping.adelaide.edu.au/shiny/.

Loop-mediated isothermal amplification polymerase chain reaction in place of a modified Knott test in screening dogs for heartworm (Dirofilaria immitis) infection combined with antigen detection test.

To improve the current recommendations for the diagnosis of canine heartworm (Dirofilaria immitis) disease. Blood samples collected from 35 shelter dogs in the Republic of Korea. Samples were tested for the presence of microfilaria using the modified Knott (MK) test and D immitis DNA using species-specific loop-mediated isothermal amplification (LAMP) PCR. The blood samples were additionally assessed for the presence of heartworm antigens using the Antigen Rapid Canine Heartworm AG Test Kit 2.0 (Bionote Co). The performance of the MK test and LAMP PCR was assessed through statistical analysis, with a paired McNemar test utilized for comparison. The heartworm antigen was detected in 28.5% of the subjects. Of the 10 positive animals, the MK test detected microfilaria in 4 of 35 (11.4%) animals, and LAMP PCR detected D immitis DNA in 6 of 35 (17.1%). The results of this study indicate that the LAMP PCR showed more positive results in samples compared to the conventional MK test. The D immitis-specific LAMP PCR assay has the potential to function as an alternative to current detection methods. It could complement the existing antigen detection tests in diagnosing canine heartworm infections.

A Case Study on Canine Heartworm (Dirofilaria immitis)

A four years old Japanese Spitz dog with a history of anorexia, vomiting, diarrhoea, weakness, reluctant to move, respiratory difficulty, and abdominal discomfort was admitted to the Veterinary Teaching Hospital, Nepal Polytechnic Institute, Chitwan, Nepal. The dog underwent clinical examination including hematological investigation. The hematological blood assays revealed severe anaemia, thrombocytopenia, leukopenia, lymphocytopenia, monocytopenia, and eosinopenia. A peripheral blood smear showed undulating movement of larvae of Dirofilaria Immitis which confirmed it as a canine Dirofilaria immitis (canine heart worm) disease. On the first day of presentation in the hospital, since the dog was dehydrated and anorectic, it was given fluids of 400 ml of normal saline and 200 ml of DNS (dextrose normal saline), pantoprazole at 0.7 mg/kg slow IV, ondansetron at 0.5 mg/kg slow IV, and haematinic agent (HB-RON®) at 5 ml BID PO (Iron, vitamin B12, Folic acid, Zinc, L-Lysin). The following day, the dog was dead, even before all the confirmatory diagnoses. That shows heartworm is prevalent in dog so strategic vector control and screening are recommended for the prevention and control of the disease in countries like Nepal.

Delayed canine heartworm (Dirofilaria immitis) microfilarial reduction following Advocate™ for dogs (imidacloprid, moxidectin) treatment

Macrocyclic lactone (ML) anthelmintics are currently the only class of drugs available for canine heartworm prevention. Recent reports of Dirofilaria immitis infection occurring in dogs reportedly receiving ‘rigorous’ prevention in Queensland, Australia, coupled with the confirmation of ML-resistant isolates in the USA, has led to speculation about the potential emergence of ML-resistance in Australia. In this study, we describe two cases (Dog 1 and 2) of asymptomatic canine heartworm disease in Townsville, Australia, that were reportedly receiving ‘rigorous’ heartworm prevention according to the owners’ claims. We aimed to deploy currently available tools to assess the phenotypic and genotypic ML-resistance status of these two dogs. For phenotypic testing, we performed an in-vivo 7-day microfilariae suppression test using a dose of spot-on moxidectin (Advocate™ for Dogs, 100 g/L imidacloprid + 25 g/L moxidectin). This formulation is marketed as Advantage Multi® for Dogs in the USA, which claims a D. immitis microfilaricidal effect. For genetic testing, an Illumina amplicon metabarcoding approach was used to target single nucleotide polymorphisms (SNPs) previously associated with ML-resistance in D. immitis from the USA. Dog 1 and Dog 2 demonstrated <10 % and <40 % reductions in circulating microfilariae seven days after moxidectin treatment, respectively. These phenotypes were not corroborated by genetic SNP testing, as both dogs were classified as susceptible across all examined markers. To streamline testing of D. immitis SNPs, we developed a rhAmp™ SNP qPCR approach for rapidly genotyping suspect cases of ML-resistant infections at the two major loci (L15709_A and L30575). These findings illustrate a phenomenon shown in some heartworm cases outside the USA, whereby infected dogs are failing to see marked reductions in microfilaraemia after ML treatment but possess an ML-susceptible genotype.

Strain-level variations of Dirofilaria immitis microfilariae in two biochemical assays.

The increase in reports of resistance to macrocyclic lactones in the canine heartworm, Dirofilaria immitis is alarming. While DNA based tests have been well-validated, they can be expensive. In a previous study, we showed that two biochemical tests adapted to a 96- well plate format and read in a spectrophotometer could detect differences among lab validated D. immitis isolates. The two tests- Resazurin reduction and Hoechst 33342 efflux-detect metabolism and P-glycoprotein activity respectively in microfilariae isolated from infected dog blood. Our objective was to optimize the two assays further by testing various assay parameters in D. immitis isolates not tested previously. We tested microfilarial seeding density, incubation time and the effect of in vitro treatment with ivermectin and doxycycline in five other D. immitis isolates-JYD-34, Big Head, Berkeley, Georgia III and LOL. All assays were performed in 3 technical replicates and 2-4 biological replicates. To understand the molecular basis of the assays, we also performed qPCR for selected drug metabolism and elimination associated genes of the ABC transporter and cytochrome P450 gene families. Metabolism and ABC transporter activity as detected by these assays varied between strains. Anthelmintic status (resistant or susceptible) did not correlate with metabolism or P-gp efflux. Basal transcriptional variations were found between strains in ABC transporter and cytochrome P450 genes. These assays provide a greater understanding of the biochemical variation among isolates of D. immitis, which can be exploited in the future to develop in vitro diagnostic tests capable of differentiating susceptible and resistant isolates.

Metatranscriptomic analysis of common mosquito vector species in the Canadian Prairies.

Mosquitoes are the most dangerous animals on the planet, responsible for over 800,000 deaths per year globally. This is because they carry and transmit a plethora of human disease-causing microorganisms, such as West Nile virus and the malaria parasite. Recent innovations in nucleic acid sequencing technologies have enabled researchers unparalleled opportunities to characterize the suite of microorganisms harbored by different mosquito species, including the causal agents of disease. In our study, we carried out 3 years of intensive mosquito surveillance in Canada. We collected and characterized the microorganisms harbored by >35,000 mosquitoes, including the identification of the agents of Cache Valley fever, avian malaria, and canine heartworm. We also detected insect-specific viruses and discovered 17 new viruses that have never been reported. This study, which is the first of its kind in Canada and one of only a handful globally, will greatly aid in future infectious disease research.

Development of a novel rodent model for dog heartworm microfilaremia using the severe-combined immunodeficiency mouse

Dirofilaria immitis is a mosquito-borne parasitic nematode that causes fatal heartworm disease in canids. The microfilariae are essential for research, including drug screening and mosquito-parasite interactions. However, no reliable methods for maintaining microfilaria long-term are currently available. Therefore, we used severe combined immunodeficiency (SCID) mice to develop a reliable method for maintaining D. immitis microfilaria. SCID mice were injected intravenously with microfilariae isolated from a D. immitis-infected dog. Microfilariae were detected in blood collected from the tail vein 218 days post-inoculation (dpi) and via cardiac puncture 296 dpi. Microfilariae maintained in and extracted from SCID mice showed infectivity and matured into third-stage larvae (L3s) in the vector mosquito Aedes aegypti. L3s can develop into the fourth stage larvae in vitro. Microfilariae from SCID mice respond normally to ivermectin in vitro. The microfilariae in SCID mice displayed periodicity in the peripheral circulation. The SCID mouse model aided in the separation of microfilariae from cryopreserved specimens. The use of SCID mice enabled the isolation and sustained cultivation of microfilariae from clinical samples. These findings highlight the usefulness of the SCID mouse model for studying D. immitis microfilaremia in canine heartworm research.

Evaluation of coagulation and platelet activation state and function in heartworm-infected dogs.

Enhanced platelet responses have been demonstrated in heartworm-infected (HWI) dogs; however, the cause and clinical implications of altered platelet function have not been fully elucidated. This study evaluated platelet function in HWI dogs. Anticoagulated whole blood collected from eight HWI and eight uninfected dogs was evaluated using turbidometric platelet aggregometry, a platelet function analyzer (PFA-100), a total thrombus analysis system (T-TAS), tissue factor-activated and tissue plasminogen activator modified thromboelastography (TF- and tPA-TEG), CBC, von Willebrand Factor activity, and fibrinogen concentrations. Platelet activation state and the presence of reticulated platelets were assessed via flow cytometric expression of P-selection (CD-62P) and thiazole orange staining. Platelet aggregation responses to adenosine diphosphate (ADP, 10 μM) or collagen (20 μg/mL), PFA-100 closure times, and T-TAS occlusion times did not differ between groups. TEG values TF-R, tPA-R, TF-K, and TF-LY60 were decreased (P = .025, P = .047, P = .038, P = .025) and TF-MA, tPA-MA, TF-G, tPA-G and TF-alpha angle were increased (P < .04) in HWI dogs. HWI dogs had higher fibrinogen concentrations (465.6 ± 161 mg/dL vs 284.5 ± 38 mg/dL, P = .008) and eosinophil counts (0.686 ± 0.27 × 103/μL vs 0.267 ± 0.20 × 103/μL, P = .003). There was no difference in hematocrit, activation state, or percent of reticulated platelets. Non-activated reticulated platelets exhibited higher CD62P expression compared with mature platelets. Chronic canine heartworm disease was accompanied by hypercoagulability, hyperfibrinogenemia, and decreased fibrinolysis. Enhanced platelet activation was not identified in this group of HWI dogs.

Current State of Canine Heartworm in Portugal.

The favourable geo-climatic conditions in Portugal have made it highly conducive to the development of Dirofilaria immitis in dogs, leading to its identification as an endemic region. This nematode is rapidly spreading across Europe, particularly in northeastern countries. The objective of this study was to provide an updated assessment of the prevalence of this disease in Portuguese dogs, analysing the results in relation to epidemiological and geo-environmental factors, and to identify potential risk factors. A total of 1367 dogs from all continental and insular districts were included in the study and tested for D. immitis antigens. The overall prevalence was found to be 5.9%. It was observed that the disease is spreading northward, with previously unaffected districts now reporting cases, and that the prevalence in coastal districts exceeded that of inland ones. Notably, the Aveiro district exhibited a significant increase in D. immitis prevalence, while in certain districts such as Setúbal, Santarém, Madeira, or Faro, a stabilisation or decrease in prevalence was noted. Furthermore, outdoor and older dogs were found to be at a higher risk of infection. No positive cases were detected in the Azores. Most of the infected dogs were located in areas of high and medium risk of infection. This study underscores the importance of implementing pharmacological prophylaxis, vector control strategies, and public awareness programs to control the spread of this zoonotic disease.

Microfilaruria of Dirofilaria immitis in a dog from Italy

Dirofilaria immitis is a mosquito-borne nematode-causing canine heartworm disease, with adult worms localized in the pulmonary arteries and right heart. In rare cases, ectopic migration might occur, and adults and blood circulating microfilariae can be found in unusual organs or fluids (e.g., eyes, abdominal cavity, bone marrow, and urine). A 17-year-old mixed-breed female dog was presented in a private veterinary clinic in Italy for hematuria and dysuria. Physical examination showed cardiac mitral murmur with marked respiratory distress and cyanotic mucous membranes after handling. Abdominal ultrasounds revealed a non-specific chronic cystopathy, while the echocardiography showed enlargement of the right heart associated with tricuspid insufficiency and mitral regurgitation, with the presence of an adult filariae in the right ventricular chamber. Circulating microfilariae were observed in the blood smear and molecularly identified as D. immitis. Unusual microfilaruria was detected in the urine sediment. Data presented raise awareness about the occurrence of microfilariae in unusual locations, such as the bladder, suggesting the need of a thorough clinical and laboratory assessment where D. immitis is endemic.

Detection and dynamics of tumor necrosis factor alpha in the diagnosis and treatment of canine heartworm disease.

The aim of this study was to determine the concentration of TNF-alpha (TNF-α) in dogs naturally infected with Dirofilaria immitis (D. immitis) and to assess whether there are any changes in TNF-α concentration and their dependence during therapy for heartworm disease (HWD). For this study, 14 client-owned dogs with HWD were selected. Clinical and parasitological examinations (modified Knott test for circulating microfilariae and SNAP Test IDEXX for circulating D. immitis antigen) had been used for diagnosing D. immitis and HWD. All dogs were treated with an alternative therapy for HWD (oral doxycycline 10 mg/kg b.w., once daily for 6 weeks, then alternately 4 weeks without and 2 weeks with the medication, and oral ivermectin 6-14 µg/kg b.w., every 2 weeks). The dogs blood sera at the moment of HWD diagnosis, during and at the end of therapy were frozen for further quantifying of TNF-α (Canine TNF-alpha ELISA kit, Thermo scientific). At the moment of HWD diagnosis TNF-α was detected in 9 dogs (7.21±12.44 pg/ml). Concentration of TNF-α was not significantly change during the therapy, neither related to the level of D. immitis antigen nor to antigen level changes. The alternative therapy for HWD has no influence on TNF-α concentration dynamics.

Erythrocyte sedimentation rate in heartworm naturally infected dogs "with or without" Leishmania infantum seropositivity: an observational prospective study.

Canine heartworm disease by Dirofilaria immitis and canine leishmaniosis by Leishmania infantum (CanL) are both vector-borne diseases with frequently overlapping endemicity and able to trigger the acute phase response, being characterized by variations in acute phase proteins (APP). Recently, erythrocyte sedimentation rate (ESR), an indicator of inflammation, has gained attention in veterinary medicine, proving useful in several conditions that include CanL active forms in dogs. This study aims to evaluate ESR in heartworm-infected dogs, compare levels with heartworm-infected and L. infantum seropositive dogs as well as clinically healthy dogs, and assess correlations with other laboratory parameters. From October 2022 to January 2023, a prospective observational study was conducted enrolling heartworm-infected (Dirofilaria group) and heartworm-infected L. infantum seropositive (Dirofilaria/Leishmania group) animals subgrouped according to the CanL clinical form (Dirofilaria/Leishmania active and non-active groups). A group of clinically healthy dogs (control group) was also included. For each dog enrolled physical examination and laboratory tests (complete blood count, biochemical panel including APP, serum protein electrophoresis) were performed. Dirofilaria and Dirofilaria/Leishmania groups presented a significantly higher ESR level compared to healthy dogs. Dirofilaria/Leishmania active group had the highest ESR level among the groups considered. Dirofilaria/Leishmania non-active group had an ESR similar to the Dirofilaria group, but significantly higher and lower compared to the control and the Dirofilaria/Leishmania active group, respectively. A significant positive correlation between ESR and C-Reactive Protein has been found in all groups except for the Dirofilaria/Leishmania non-active group. In Dirofilaria/Leishmania active group a strong positive correlation between ESR and gamma globulins percentage as well as a strong negative correlation between ESR and albumin, albumin/globulins ratio were found. Overall, the ESR was confirmed to be an inflammation marker as well as a helpful disease index, being notably increased in heartworm-infected dogs affected by an active form of CanL.

Heartworm disease in domestic dogs in Estonia: indication of local circulation of the zoonotic parasite Dirofilaria immitis farther north than previously reported

BackgroundThe mosquito-borne zoonotic parasite Dirofilaria immitis continues to spread northwards in Europe. This parasite can cause potentially life-threatening heartworm disease in dogs and pulmonary dirofilariasis in humans and is, therefore, a major health concern in both the veterinary medicine and human medical fields. This is the first report of D. immitis infections and heartworm disease in the Baltic country Estonia.MethodsData on canine D. immitis infections and heartworm disease were collected from the electronic patient records database of the Small Animal Clinic of Estonian University of Life Sciences, the only university clinic in Estonia. The patient records of dogs with confirmed diagnosis of D. immitis infection or heartworm disease were reviewed and summarised.ResultsSix dogs had been diagnosed with confirmed D. immitis infection or heartworm disease at the university clinic in 2021–2022. The confirmed diagnoses had been reached following international guidelines, based on a combination of different tests. Molecular confirmation of the parasite species had not been performed. Two of the dogs had been imported while four had no travel history outside of the country.ConclusionsFour of the dogs with a confirmed D. immitis infection or heartworm disease had no history of being imported or travelling outside of the country, indicating autochthonous infections and, consequently, local circulation of the parasite in Estonia. These findings represent the new northernmost autochthonous cases of D. immitis infection and canine heartworm disease reported in the European Union.Graphical

Improving access to melarsomine therapy: treating canine heartworm infection in a high-volume, outpatient community clinic setting

BackgroundModels that provide high-quality veterinary care for more affordable prices are emerging, but not well documented outside of wellness and preventative care. Effective treatment guidelines for heartworm disease have been developed by the American Heartworm Society; however, not all owners are able to access treatment due to the high costs associated with sick and emergency care services.MethodsTo increase access to high-quality adulticidal treatment of canine heartworm disease, we developed and implemented a technician-leveraged heartworm treatment protocol for high-volume, outpatient community clinic settings based on the American Heartworm Society guidelines. Modifications were few and included limited pre-treatment blood work, pre-injection sedation, post-injection pain medication, and a reduced exercise restriction period. We monitored retention rates for 556 dogs throughout treatment, evaluated treatment success (defined as no antigen detection 9 months post treatment) for patients that returned for post-treatment antigen testing, and reported on adverse reactions and therapy adherence throughout treatment.ResultsOf the patients that began adulticide therapy, 539/556 (97%) successfully completed the three-injection series. No microfilariae were detected in 99% (428/433) of those who returned for post-injection microfilaria testing. Among those that returned for or reported the results of post-injection antigen testing, no antigen was detected for 99% (245/248) and no microfilariae were detected for 99.5% (200/201). During the course of treatment, 483/539 (90%) of patients experienced at least one adverse reaction, with the most frequently reported types being behavioral and injection site reactions. 25/539 (4.6%) of owners sought additional medical care for adverse reactions at some point during the treatment course. The overall mortality rate was 1.3% (7/556).ConclusionsThis study represents the first evaluation of a heartworm treatment protocol optimized for implementation in a high-volume, outpatient community clinic setting. Our findings align with those previously reported in private practice or tertiary referral centers, illustrating that through the inclusion of pre-treatment blood work, employing short-acting or reversible sedatives, ensuring proper analgesia, minimizing the use of ancillary diagnostics, reducing the duration of in-clinic monitoring while focusing on outpatient care, and maximizing technician involvement, we can deliver effective and safe melarsomine therapy at a more affordable cost to pet owners.Graphical

Temperature-bounded development of Dirofilaria immitis larvae restricts the geographical distribution and seasonality of its transmission: case study and decision support system for canine heartworm management in Australia

Dirofilaria immitis is the causative agent of canine heartworm disease. We used the established heartworm development unit (HDU) principle to map the extrinsic incubation period (EIP) of D. immitis in Australia using historical weather data from 2013–2022. We found weather conditions suitable for EIP completion showed substantial seasonality and geographical variability. Whilst a considerable percentage of the Australian territory showed suitable weather conditions to always support EIP completion (17%), only 2.7% of the 2021 Australian human population lived in this region. Therefore, 97% of the population lived in an area that changed its EIP suitability within the study period. EIP completion is required prior to D. immitis transmission, meaning that infection risk of D. immitis is seasonal and location-dependent, being disrupted each year for most of the human population’s dogs. We developed an online, open access tool allowing us to visualise EIP completion across Australia historically and in near real-time. We aim to support veterinarians to make risk-based recommendations for dirofilariosis prevention by using the tool, available at https://heartworm-mapping.adelaide.edu.au/shiny/.

Prevention and long-term outcomes of naturally occurring canine heartworm infection in primary care settings.

This study had two objectives: first, to examine the association between the history of heartworm preventive purchase compliance and the risk of positive heartworm tests, and second to preliminarily investigate the long-term cardiac outcomes of heartworm disease in dogs that had undergone successful adulticidal therapy. A retrospective cohort study design was used for both analyses, using anonymous transaction data from Covetrus (retrospective analysis 1) and anonymized medical records from Banfield Pet Hospital (retrospective analysis 2), both including canine patients across the USA. The first analysis examined the relative risk (RR) of a positive heartworm test in dogs with lapses in heartworm preventive purchase history compared to dogs that had no history of a preventive purchase six to 24 months prior to the test. In the second analysis, a long-term evaluation of structured diagnostic codes pertaining to cardiac diseases and risk assessment of outcomes was performed in dogs that had previously been successfully treated for heartworm disease compared to dogs that never had a positive heartworm test. 83,478 unique patients were included in the first analysis. Compared to 32,413 dogs with no history of a heartworm preventive purchase, 44,410 dogs with lapses in monthly preventive purchases had a reduced risk of testing positive for heartworm disease (RR = 0.36, p < 0.0001). Dogs (n = 6,655) with lapses in injectable heartworm preventive administration had a decreased risk of a positive test versus dogs with no preventive purchases (RR = 0.15, p < 0.0001), as well as versus dogs with lapses in monthly heartworm preventive purchases (RR = 0.28, p = 0.0024). In the second analysis, 6,138 patients treated for heartworm infection were found to have significantly (p < 0.001) elevated risks of right heart failure (RR = 3.59), left heart failure (RR = 1.83), or cardiomyopathy (RR = 2.79) compared to 4,022,752 patients that never had a positive heartworm test. This study highlights the importance of compliance with heartworm preventive guidelines, to reduce the risk of heartworm disease in dogs, which is not only a potentially life-threatening condition in the short-term but also associated with long-term negative cardiac outcomes.

Survey of Common Infectious Diseases in Urban Foxes (Vulpes spp.) in Southeastern Iran.

The red fox (Vulpes vulpes) is one of the most common species of wild Canidae and is relatively abundant in Iran. Foxes (Vulpes spp.) transmit many zoonotic diseases, the most important of which are visceral leishmaniasis, rabies, hydatidosis, toxocariasis, and trichinellosis. In this study, visceral leishmaniasis, rabies, ectoparasites, canine gastrointestinal helminths, dermatophytosis, distemper, parvovirus infection, and heartworm infections were evaluated among live-trapped and rescued foxes injured by traffic road accidents referred to the teaching hospital of Kerman, Iran, veterinary faculty. Skin scraping and direct microscopic examination were used to detect ectoparasites and dermatophytosis. Immunochromatography rapid kits were used to detect dirofilariasis, parvovirus infection, and distemper. Necropsy was used to check for gastrointestinal parasites. Rabies and visceral leishmaniosis were screened for with direct fluorescent antibody test and ELISA methods, respectively. Gastrointestinal helminth infections, including Toxocara canis, Taenia taeniaeformis, Dipylidium caninum, Joyeuxiella echinorhyncoids, Toxascaris leonina, Taenia hydatigena, Echinococcus granulosus, Rictolaria spp., Oxynema spp., Macracanthorhynchus hirudinaceus, and Physaloptera spp., were detected. Skin scrapings showed dermatophytosis and various ectoparasites, including Rhipicephalus sanguineus, Ctenocephalides canis and Ctenocephalides felis, and Sarcoptes scabiei, in foxes with dermal lesions. Distemper and parvovirus infection (26.66%) were the common viral diseases, and rabies infection rate was quite high (16.66%). Dirofilariasis and leishmaniasis were detected in 10% of the population. This study showed that urban foxes which often cohabit with humans and domestic animals are carriers of many different pathogens. This interaction may facilitate indirect cross-species transmission of zoonotic disease. Periodic health monitoring and multidisciplinary cooperation for the diagnosis, control, and prevention of these zoonoses is highly recommended.

Seroprevalence, Blood Chemistry, and Patterns of Canine Parvovirus, Distemper Virus, Plague, and Tularemia in Free-Ranging Coyotes (Canis latrans) in Northern New Mexico, USA.

Wildlife diseases have implications for ecology, conservation, human health, and health of domestic animals. They may impact wildlife health and population dynamics. Exposure rates of coyotes (Canis latrans) to pathogens such as Yersinia pestis, the cause of plague, may reflect prevalence rates in both rodent prey and human populations. We captured coyotes in north-central New Mexico during 2005-2008 and collected blood samples for serologic surveys. We tested for antibodies against canine distemper virus (CDV, Canine morbillivirus), canine parvovirus (CPV, Carnivore protoparvovirus), plague, tularemia (Francisella tularensis), and for canine heartworm (Dirofilaria immitis) antigen. Serum biochemistry variables that fell outside reference ranges were probably related to capture stress. We detected antibodies to parvovirus in 32/32 samples (100%), and to Y. pestis in 26/31 (84%). More than half 19/32 (59%) had antibodies against CDV, and 5/31 (39%) had antibodies against F. tularensis. We did not detect any heartworm antigens (n = 9). Pathogen prevalence was similar between sexes and among the three coyote packs in the study area. Parvovirus exposure appeared to happen early in life, and prevalence of antibodies against CDV increased with increasing age class. Exposure to Y. pestis and F. tularensis occurred across all age classes. The high coyote seroprevalence rates observed for CPV, Y. pestis, and CDV may indicate high prevalence in sympatric vertebrate populations, with implications for regional wildlife conservation as well as risk to humans via zoonotic transmission.