Dirofilaria Immitis Infection Research Articles

Epidemiological analysis of Dirofilaria immitis (Spirurida: Onchocercidae) infecting pet dogs (Canis lupus familiaris, Linnaeus, 1758) in Baixada Fluminense, Rio de Janeiro.

Dirofilaria immitis infection is routinely detected in dogs during veterinary care in tropical and subtropical regions worldwide. Parasitological tests for the detection of this infection are routinely performed only in areas with a high prevalence. Baixada Fluminense, a region in Rio de Janeiro, was considered heartworm-free until local veterinarians began to receive blood exams results indicating the presence of microfilariae (MF). A laboratory database was hence used to collect data from 2017 to 2020 to understand the extent of spread of the parasite in this area. The results of complete blood count analysis and MF or heartworm antigen detection tests conducted on canine samples sent from veterinary clinics in Baixada Fluminense (Magé, Duque de Caxias, Guapimirim, Nova Iguaçu, and São João de Meriti municipalities) were included. In total, the results of 16,314 hematological tests were considered. The overall prevalence of D. immitis was 3.4% (554/16,314), considering that only one test result was obtained per animal on the same day. This study is highly relevant because it indicates the spreading geographic distribution of the worms, heightens awareness among local health professionals and the general population, and encourages compliance with prophylactic measures to prevent further spread of parasite.

Status of selected feline infectious diseases in Gwangju, Korea

From 2008 to 2017, blood samples from 280 and fecal samples from 149 stray cats in Gwangju, South Korea, were examined for feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), Dirofilaria immitis, and Giardia infections using commercial diagnostic tests. Overall, the combined prevalence of FeLV, FIV, D. immitis, and Giardia was 8.6%, 1.4%, 0.4%, and 2.0%, respectively. FeLV exhibited the highest prevalence rate among the 4 pathogens surveyed, both in the 2008–2009 (9.6%) and 2015–2017 (6.3%) surveys. The results of the feline Giardia study represent the first prevalence report of Giardia infection among stray cats in Korea.

Dirofilaria immitis in pet dogs from the metropolitan area of the Colombian Caribbean

A cross-sectional study was carried out to determine the frequency and factors associated with Dirofilaria immitis infection in pet dogs in the metropolitan area of the Colombian Caribbean (northern Colombia). A total of 173 dogs were analyzed by a commercial rapid immunochromatographic test (RIT) and a nested PCR of the cytochrome oxidase subunit I gene, in parallel. Ninety-two (53.2%) of the dogs showed positive results to the RIT, while 59 (34.1%) animals had D. immitis DNA by PCR. Positivity to one or both diagnostic techniques was detected in 104 (60.1%; CI95%: 53.8–67.4) of the sampled dogs. In PCR-positive dogs, phylogenetic analyses evidenced high nucleotide identity (100%) with sequences previously obtained from mosquitoes, dogs and other mammals in different countries. Exercise intolerance (p = 0.002; OR: 2.33; CI95%: 1.37–3.96) and thrombocytopenia (p = < 0.001; OR: 1.95; CI95%: 1.11–3.43) were the main factors associated with D. immitis infection in dogs. The high frequency of D. immitis in dogs indicates a wide distribution of this parasite in the metropolitan area of the Colombian Caribbean, which can be of animal and public health concern. Our results highlight the need to combine different methods to increase the diagnostic accuracy of D. immitis.

Elimination of Dirofilaria immitis Infection in Dogs, Linosa Island, Italy, 2020-2022.

On Linosa Island, Italy, Dirofilaria immitis infection has been hyperendemic in dogs and seroprevalent among islanders. In 2020, we implemented a heartworm disease elimination program on Linosa Island. Of 54 dogs tested for D. immitis antigen and microfilariae, 28 had positive results and received treatment with oral doxycycline twice daily for 4 weeks plus topical imidacloprid/moxidectin monthly for 12 months. The 26 dogs with negative results received monthly topical imidacloprid/moxidectin as preventive. During month 1, the number of microfilaremic dogs was reduced by 76.5%. From month 2 on, all animals were microfilariae negative, and during months 3 to 9, the number of antigen-positive dogs decreased progressively. Treatment of positive dogs coupled with chemoprophylaxis for noninfected dogs was effective, protecting them from new infections. The elimination program reduced the risk for human infection, representing a One Health paradigm. Monitoring and chemoprophylaxis are advocated to maintain the status of heartworm disease-free area.

Relative diagnostic accuracy of point-of-care tests to rule-in Dirofilaria immitis infection in clinically suspect dogs: A systematic review and meta-analysis.

Canine heartworm, Dirofilaria immitis, can cause severe disease and sometimes death of the host. Associated clinical signs, lack of preventative usage and regional endemicity are unlikely sufficient by themselves to reach a definitive diagnosis. Several point-of-care (POC) diagnostic tests are commercially available to aid in-clinic diagnosis, however, there is variable diagnostic accuracy reported and no synthesis of published evidence. This systematic review aims at meta-analysing the likelihood ratio of a positive result (LR+) to inform the selection and interpretation of POC tests in practice to rule-in heartworm infection when there is clinical suspicion. Three literature index interfaces (Web of Science, PubMed, Scopus) were searched on November 11th, 2022, for diagnostic test evaluation (DTE) articles assessing at least one currently commercialised POC test. Risk of bias was assessed adapting the QUADAS-2 protocol and articles with no evidence of high risk of bias were meta-analysed if deemed applicable to our review objective. Substantial between DTE heterogeneity was investigated including potential threshold or covariate effects. A total of 324 primary articles were sourced and 18 were retained for full text review of which only three had low risk of bias in all four QUADAS-2 domains. Of the nine heartworm POC tests evaluated, only three, IDEXX SNAP (n DTEs = 6), Zoetis WITNESS (n DTEs = 3) and Zoetis VETSCAN (n DTEs = 5) could be analysed. Both WITNESS and VETSCAN DTEs showed substantial heterogeneity due to a putative threshold effect and no summary point estimates could be reported. SNAP DTEs showed acceptable heterogeneity, and a summary LR+ was estimated at 559.0 (95%CI: 24.3-12,847.4). The quality and heterogeneity of heartworm POC test DTEs was highly variable which restricted our summary of the diagnostic accuracy to only the SNAP test. A positive result from the SNAP test provides strong evidence of the presence of an infection with adult heartworm(s) in a dog patient and this test is warranted to rule-in clinical suspicion(s) in clinics. However, our review did not appraise the literature to assess the fitness of SNAP test, or any other POC tests, to rule-out heartworm infection in dogs without clinical suspicion or following heartworm therapy.

The seroprevalence of canine dirofilariosis in dogs in the eastern coastal areas of China

Background and objectivesThe present study was carried out to assess the presence of canine Dirofilaria immitis infection in pet dogs in China. Materials and methodsFrom October 2018 to November 2019, a total of 216 sera were collected from pet hospitals in Shandong, Jiangsu, Shanghai, Zhejiang, and Fujian regions of Eastern China. The sera were tested by using a commercial canine heartworm antibody ELISA test kit. Results70.8% of the pets had significant clinical symptoms resembled to heartworm infection; the overall dirofilariosis positivity found was 12.5% (27/216); Significant positive rates differences were observed between symptomatic and asymptomatic dogs (P < 0.05) (i.e. 15.7% and 4.7% respectively).The prevalence of infection in Shandong Province (15.5%) was the highest among the surveyed areas, but the difference among the geographic regions was not statistically significant (P > 0.05). Furthermore, the prevalence detected in summer (28.2%) was significantly higher than in other seasons (P < 0.05). In addition, no significant difference was observed between male and female sex (P > 0.05). ConclusionsAltogether, these results suggest that an epidemic of dirofilariosis exists in eastern coastal China, as such preventive measures should be taken to control the spread of dirofilariosis to reduce the risk of human and pet infection with heartworm.

Safety of Simparica Trio® (sarolaner, pyrantel, moxidectin) in heartworm-infected dogs

BackgroundAssessment of the safety of heartworm preventatives in dogs with pre-existing patent heartworm (Dirofilaria immitis) infections is necessary because rapid adult worm and microfilarial death can lead to severe clinical complications, including thromboembolism and anaphylactic shock in dogs. The aim of this study was to determine the clinical safety of Simparica Trio® (sarolaner, pyrantel, moxidectin) in heartworm-infected dogs and the degree of microfilaricidal and adulticidal activity of three consecutive monthly treatments of Simparica Trio.MethodsTwenty-four laboratory Beagle dogs were implanted with 10 male and 10 female D. immitis (ZoeKY isolate), and once infection was patent, they were randomized equally among three groups to receive no treatment, 1× or 3× the maximum recommended label dose of Simparica Trio. Dogs in the treated groups received Simparica Trio on days 0, 28 and 56. In-life assessments included body weight, physical examinations, clinical observations, daily general health observations, a quantitative estimate of food consumption and blood collections for pharmacokinetic (PK) analysis, microfilariae (MF) counts and D. immitis antigen testing. At the end of the study the heart, lungs and pleural and peritoneal cavities were examined for adult D. immitis worms.ResultsSimparica Trio was generally well tolerated. Emesis occurred at low frequency in all groups including control. Abnormal stool occurred occasionally in the 1× and 3× groups throughout the 3-month study. Fever (> 104 °F/40 °C) was recorded in one 1× and one 3× dog 1 day after the first dose and resolved by the following day. No severe hypersensitivity reactions occurred. The mean number of circulating microfilariae (MF) counts in the control group increased from 12,000/ml at study start (Day 0) to > 20,000/ml at Day 28 and remained > 20,000/ml for the duration of the study. The least squares means of circulating MF were reduced by 69.8% on Day 1 and 97.4% on Day 7 for the 1× group and remained at > 99% lower than the control group for the remainder of the study. Similarly, least squares means of circulating MF were reduced by 85.3% on Day 1 and 93.9% on Day 7 for the 3× group and remained > 98% lower than the control group for the remainder of the study. At the end of the study, the mean number of implanted adult worms recovered was < 10 per sex in all groups with 90%, 85% and 75% of live adult heartworms recovered in control, 1× and 3× treatment groups, respectively. Low numbers of dead adult worms were recovered in 1× and 3×, with none in control. Following each dose, the moxidectin and sarolaner AUC and Cmax had close to dose proportional increases.ConclusionsThis study demonstrated that Simparica Trio (sarolaner, pyrantel, moxidectin) was well tolerated when administered to heartworm-positive dogs at 1× and 3× the maximum recommended dose at 28-day intervals for 3 consecutive months. Simparica Trio significantly reduced microfilaria counts in both treatment groups, without significant clinical consequences. At the doses administered, Simparica Trio had minor adulticidal activity but resulted in no clinical sequelae.Graphical

Improved Antigen Detection of Male-Only Dirofilaria immitis Infections in Canine Serum after Heat Treatment for Immune Complex Dissociation

Since the mid-1990s, male-only heartworm infections have been considered undetectable using antigen tests based on experimental studies. Results from those studies are in contrast to reports in the decade prior showing variable male heartworm antigen detection using naturally infected animals and antigen tests using chemical and/or heat immune complex dissociating steps. Several recent studies utilizing heat treatment for immune complex dissociation (Heat ICD) demonstrated increased antigen sensitivity for necropsy verified male-only infections and a higher-than-expected frequency of this type of infection. This study utilized archived canine serum with verified male-only heartworm infections to evaluate detection of the heartworm antigen using the DiroCHEK® (Zoetis LLC, Parsippany, NJ, USA), Witness® (Zoetis LLC, Parsippany, NJ, USA), and SNAP® Heartworm RT (IDEXX Laboratories, Inc., Westbrook, ME, USA) antigen tests. Results showed significant increases in sensitivity for the heartworm antigen following heat treatment for DiroCHEK® (+42.1%, p &lt; 0.0001) and Witness® (+26.3%, p = 0.0020), but not the SNAP® Heartworm RT (+10.5%, p = 0.1250). Prior to heat treatment, false negative results were obtained in 76.3–83.0% of mature infections. Infections with only immature male worms were never detected using any heartworm test used. Heat treatment of serum allows improved detection of mature male-only heartworm infections, which may occur more frequently than previously recognized, and like all heartworm infections pose a risk of chronic and cumulative pathology as well as thromboembolic disease regardless of infection intensity.

Prevalence of Dirofilaria immitis Infection in Dogs in Maiduguri, Borno State

Dirofilaria immitis infection is a major potential life threatening disease of dogs with worldwide distribution and of zoonotic importance. This study was carried out to investigate the prevalence of D. immitis. A total of 250 blood samples were randomly collected from dogs in the study area. The examination for D. immitis infection was carried out based on the conventional and immunological procedures using wet mount and Buffy coat methods. The total prevalence of D. immitis was 100 (40.00%). The prevalence of D. immitis in the adult dogs was 62 (24.80%) while, in the young dogs was 38 (15.20%). The prevalence of D. immitis in the male dogs was 54 (21.60%) while, 46 (18.40%) was the prevalence of the female dogs. The prevalence of outdoor dogs was 64 (25.60%) while, that of the indoor dogs was 36 (14.40%). The dogs with thin body condition scores had a prevalence of 80 (32.00%) while, the overweight (obesed) dogs were 20 (8.00%). However, the prevalence of D. immitis is higher in the adult, male and outdoor dogs compared to the young, female and indoor dogs. Therefore, the present study revealed a high prevalence of D. immitis infection in the study area.

Geographical analysis of seroprevalence of Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi and Dirofilaria immitis, in clinics and dog shelters in different Mexican states

This study aimed to determine the seroprevalence and geographical distribution of Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi and Dirofilaria immitis in dogs in Mexico, including owned dogs from veterinary clinics with regular medical care and shelter dogs. The Mexican territory was divided into eight geographical regions; 22 out of 32 states were included; 110 veterinary clinics and 53 dog shelters participated. SNAP® 4Dx Plus® (IDEXX® Laboratories) was used to detect antibodies against Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi and Dirofilaria immitis antigens. A total of 3522 apparently healthy dogs were tested, 1648 from clinics and 1874 from shelters. The highest seroprevalence of infection/exposure was found for Ehrlichia spp. (30.9%), followed by Anaplasma spp. (14.6%), D. immitis (5.3%) and B. burgdorferi (0.1%). Significantly more positive dogs were older than 3 years. Regarding differences between facility types, there were only differences for D. immitis which was more prevalent in clinics than in shelters (OR ​= ​1.97; 95% CI: 1.45–2.69; P ​< ​0.0001). Co-infections were detected in 38.4% of the positive samples. Dogs from Mexican states located on the Atlantic and the Pacific coast were significantly more at risk for Ehrlichia spp. and Anaplasma spp. infections than dogs from interior states. Dogs in Atlantic coastal states were more at risk for Dirofilaria immitis infection.

Probe-based qPCR as an alternative to modified Knott’s test when screening dogs for heartworm (Dirofilaria immitis) infection in combination with antigen detection tests

BackgroundCurrent recommendations for diagnosis of Dirofilaria immitis infection in dogs rely on the detection of antigen produced largely by adult females coupled with the visualization of microfilariae (mf) in the circulation via a microfilaria detection test (MFDT). It is hypothesized that qPCR assays used in parallel with antigen detection tests will perform better in detecting mf than modified Knott’s test (MK), when combined with antigen detection. This study compares probe-based qPCR and MK techniques for mf detection used in parallel with the DiroCHEK® antigen test to screen for heartworm infection in shelter dogs.MethodsMatching blood and serum samples were collected from 300 shelter dogs in Brazos and Harris counties, Texas, USA. Blood was assessed for the presence of mf via MK and the presence of D. immitis DNA by a species-specific probe-based qPCR assay. Serum samples were tested for the presence of heartworm antigen using DiroCHEK® before and after immune complex dissociation (ICD) via heat treatment. In addition, the performance of each diagnostic test was evaluated via Chi-square test, Cochran’s Q test, and post hoc analysis.ResultsQualitatively, MK detected mf in 22.0% (66/300) of samples, 55 of which were morphologically identified as D. immitis and 11 as Acanthocheilonema reconditum. The range of heartworm mf was 28 to 88,803 mf/ml (median: 6627.5). Real-time PCR detected D. immitis DNA in 20.7% (62/300) of samples. Heartworm antigen was detected in 24.7% (74/300) of samples pre-ICD, and in 29.3% (88/300) post-ICD. When comparing tests, the Chi-square and McNemar’s tests showed that the difference between positive and negative proportions was statistically significant. The Cochran test showed the difference in the distributions of cases and non-cases was significant when individual tests were combined (χ2 = 62.3, df = 3, P < 0.0001) and when parallel methods were combined (χ2 = 43.1, df = 4, P < 0.0001).ConclusionConsidering individual and combined test performances, practicality, and efficient use of bench time, this heartworm-specific probe-based qPCR method is a viable option as a mf detection test to be used in parallel with antigen tests for canine heartworm infection in diagnostic and research settings.Graphical

Evaluation of Side Effects and Long-Term Protection of a Sustained-Release Injectable Moxidectin Formulation against Dirofilaria immitis Infection in Dogs: An Observational-In Field Multicentric Study.

Simple SummaryThe sustained-release moxidectin formulation of Afilaria SR is labelled to prevent Dirofilaria immitis infection in dogs for a period of six months. An observational—in field multicentric study was design to evaluate the tolerability and the long-term prevention of Afilaria SR in Italy. A total of 583 dogs were recruited from 2018 to 2021, receiving the drug annually and monitored by veterinary practitioners after each administration. Antigenic tests were performed 210, 365, 730, and 1095 days after the administration of the drug. None of the enrolled dogs was detected as positive, since it was possible to establish that 100% of protection was achieved. Afilaria SR was well tolerated since only the 13% of dogs demonstrated mild reaction in the injection site and only two dogs out of 583 demonstrated anaphylactoid or angioneurotic reactions. These data support the high prevention rate against Dirofilaria immitis disease in all enrolled dogs and indicate the high safety profile of the product, considering the low number and the low grade of side effects.The sustained-release moxidectin formulation Afilaria SR is a relatively new product and has been labelled to prevent Dirofilaria immitis infection in dogs for a six months-period. An observational, in field multicentric study was performed, aiming to evaluate the tolerability and the long-term prevention of Afilaria SR in Italy, a country where filariasis is endemic. The study was designed to include not less than 300 dogs, older than 6 months, of any breed. Side effects were recorded by veterinarians and antigenic tests were performed after 210, 365, 730, and 1095 days after the administration of the drug. A total of 583 dogs were recruited from 2018 to 2021 and all of them were negative with respect to antigenic tests at all time points, indicating that 100% of protection was achieved. Ranking of adverse reactions and correlation to patient features were analyzed using descriptive statistics and χ2 square test, respectively. Afilaria SR was well tolerated: 13% of dogs experienced mild reactions and only two dogs out of 583 (0.3%) demonstrated anaphylactoid/angioneurotic reactions, resolved administering corticosteroids. These data support that Afilaria SR prevented Dirofilaria immitis disease in all enrolled dogs and the low number and the low grade of side effects indicate the high safety profile of the product.

Serodiagnostic difficulties and possibilities of heartworm disease in regions where both Dirofilaria immitis and Dirofilaria repens infections occur.

This retrospective study was performed on 71 dogs which had been admitted for heartworm screening or with clinical suspicion of heartworm disease. The examination methods included polymerase chain reaction (PCR) to identify Dirofilaria immitis and/or Dirofilaria repens infections and a heartworm antigen (Ag) test (VetScan). By using PCR, 26 dogs were found positive only for Dirofilaria immitis (Group 1), while 21 dogs for both D. immitis and D. repens (Group 2). Group 3 included 24 dogs with D. repens infection only according to the PCR results. The sensitivity of the VetScan Ag test for the Group 1 and 2 animals proved to be 97.7% (95% Blaker confidence interval; CI 89.0%-99.9%). The specificity of the VetScan Ag test, calculated from the results of Group 3, was found to be 66.7% (95% CI 45.6%-83.1%), which was lower than that reported from the USA, where D. repens does not occur. In cases when PCR results were positive for D. repens but negative for D. immitis, the occult dirofilariosis was the likely explanation for the positive D. immitis Ag tests. These observations highlight the importance of performing more Ag tests simultaneously in those areas where both Dirofilaria species are present.

Concern for Dirofilaria immitis and Macrocyclic Lactone Loss of Efficacy: Current Situation in the USA and Europe, and Future Scenarios.

Dirofilaria immitis infection is one of the most severe parasitic diseases in dogs. Prevention is achieved by the administration of drugs containing macrocyclic lactones (MLs). These products are very safe and highly effective, targeting the third and fourth larval stages (L3, L4) of the parasite. Until 2011, claims of the ineffectiveness of MLs, reported as “loss of efficacy” (LOE), were generally attributed to owners’ non-compliance, or other reasons associated with inadequate preventative coverage. There was solid argumentation that a resistance problem is not likely to occur because of (i) the great extent of refugia, (ii) the complexity of resistance development to MLs, and (iii) the possible large number of genes involved in resistance selection. Nevertheless, today, it is unequivocally proven that ML-resistant D. immitis strains exist, at least in the Lower Mississippi region, USA. Accordingly, tools have been developed to evaluate and confirm the susceptibility status of D. immitis strains. A simple, in-clinic, microfilariae suppression test, 14-28 days after ML administration, and a “decision tree” (algorithm), including compliance and preventatives’ purchase history, and testing gaps, may be applied for assessing any resistant nature of the parasite. On the molecular level, specific SNPs may be used as markers of ML resistance, offering a basis for the validation of clinically suspected resistant strains. In Europe, no LOE/resistance claims have been reported so far, and the existing conditions (stray dogs, rich wildlife, majority of owned dogs not on preventive ML treatment) do not favor selection pressure on the parasites. Considering the genetic basis of resistance and the epizootiological characteristics of D. immitis, ML resistance neither establishes easily nor spreads quickly, a fact confirmed by the current known dispersion of the problem, which is limited. Nevertheless, ML resistance may propagate from an initial geographical point, via animal and vector mobility, to other regions, while it can also emerge as an independent evolutionary process in a new area. For these reasons, and considering the current chemoprophylaxis recommendations and increasing use of ML endectoparasiticides as a potential selection pressure, it is important to remain vigilant for the timely detection of any ML LOE/resistance, in all continents where D. immitis is enzootic.

Zoonotic Dirofilaria immitis and Dirofilaria repens infection in humans and an integrative approach to the diagnosis

Dirofilariosis by Dirofilaria immitis and Dirofilaria repens is endemic in dogs from countries of the Mediterranean basin. Both species may infect humans, with most of the infected patients remaining asymptomatic. Based on the recent description of the southernmost hyperendemic European focus of heartworm disease in dogs from the Pelagie archipelagos, we performed a serological and molecular survey in human population of that area. Human blood samples were collected in the islands of Linosa (n=101) and Lampedusa (n=296) and tested by ELISA and molecular test for the detection of D. immitis and D. repens. Samples were also screened for filarioid-associated endosymbionts, Wolbachia sp. The seroprevalence of D. immitis and D. repens was, respectively, 7.9% and 3.96% in Linosa, and 7.77% and 19.93% in Lampedusa. Out of 397 human blood samples tested molecularly, 4 scored positive (1%) for Dirofilaria spp. by qPCR (i.e., three for D. immitis and one for D. repens) and 6 (1.5%) for Wolbachia. Of the qPCR positive for Dirofilaria spp., only D. repens was amplified by cPCR and was positive for Wolbachia. In the phylogenetic analysis, the sequence of Wolbachia detected in D. repens positive samples clustered along with other C supergroup filarioids. Our results overlap with the recent prevalence data collected on dogs from the same area, where D. immitis is prevalent in Linosa and D. repens prevails in Lampedusa. Molecular detection of D. immitis in human blood is quite unusual considering that humans are dead-end hosts for dirofilarial infection and most of the human cases described so far in Europe were ascribed to D. repens. An integrative diagnostic approach using serum analysis and Wolbachia detection is also presented. In endemic areas for canine dirofilarioses humans are exposed to the infection, suggesting the importance of One Health approach in diagnosing, treating and controlling this zoonotic parasitosis.

Dirofilaria immitis infection in the Pelagie archipelago: The southernmost hyperendemic focus in Europe.

Dirofilaria immitis and Dirofilaria repens are mosquito-borne filarioids of zoonotic concern, which primarily cause canine heartworm disease (HWD) and subcutaneous dirofilariosis, respectively. The geographical distribution of these nematodes is constantly changing, due to many factors such as the colonization by new invasive mosquito species, the increased movement of animals and the absence of chemoprophylactic strategies in non-endemic regions. Although HWD has always been considered endemic in northern Italy, an increase in the prevalence of this disease has been recorded in the last decades in central and southern regions. We describe the southernmost hyperendemic European focus of heartworm disease in the Pelagie archipelagos. From June to November 2020, 157 dogs and 46 cats were sampled in Linosa and Lampedusa islands for the detection of Dirofilaria immitis and Dirofilaria repens by modified Knott's, rapid antigen and molecular tests. Mosquitoes were collected using CDC light and BG sentinel-2 traps and aspirators, and tested for host blood meal and Dirofilaria spp. DNA. Out of 56 dogs in Linosa and 101 in Lampedusa, 33 (i.e. 58.9%) and 8 (i.e. 7.9%) were positive to D. immitis and D. repens, respectively. Three cats scored positive to D. immitis (i.e. 17.6%) in Linosa. Six mosquito species were identified, and the abdomen of a non-engorged Aedes albopictus was positive for D. immitis and human DNA. The results suggest that D. immitis infection could spread to new previously non-endemic territories in southern Europe, representing a real threat to animal and human health.

Infection with Dirofilaria immitis and Other Infections in Cats and Dogs from Rio de Janeiro, Brazil: The Need for Prophylactic Enforcement.

Dirofilaria immitis, a mosquito-borne nematode that primarily infects dogs, can equally infect cats. Although there have been numerous studies on canine heartworm prevalence in Brazil, there have been few studies on feline infections. Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are both life-threatening retroviruses transmitted directly between cats. Infections with Ehrlichia spp. and Anaplasma spp. are highly prevalent among dogs in Brazil, with Rhipicephalus sanguineus being the main vector for both bacteria. This study aimed to gather information on these infections among dogs and cats in the metropolitan area of Rio de Janeiro by performing rapid point-of-care tests for prophylactic enforcement. Surplus samples of serum or plasma from private laboratories were tested by enzyme-linked immunosorbent assay (ELISA) (SNAP Feline Triple Test or SNAP 4Dx Plus Test). The prevalence of heartworm disease was 7% among dogs and 0.9% among cats, the latter being 12.9% of the former. The prevalence of FIV and FeLV was 4.3 and 11.9%, respectively. Among dogs, the seroprevalence of Ehrlichia spp. and Anaplasma spp. was 27.1 and 9.8%, respectively, and Borrelia burgdorferi was not detected. Given that such infections circulate among pets, prophylactic measures should be encouraged by small animal practitioners.

Successful Treatment and Management of Canine Ehrlichiosis-Leishmaniosis-Heartworm Comorbidity

Background: Canine vector borne diseases (CVBD) are common in tropical countries where the climate favors arthropods abundance. Comorbidity with one or more CVBD are reported as clinical complication and worsen prognostic. Canine visceral leishmaniosis (CanL) is an endemic zoonotic disease in Brazil caused by Leishmania infantum, with several restrictions to canine treatment and suggestion of reservoirs euthanasia for disease control. Heart worm (HW) is a helminthic disease caused by Dirofilaria immitis infection in dogs. It is a chronic heart disease, which can lead to death by congestive heart failure. Canine ehrlichiosis (CE) is caused by Ehrlichia canis bacterial infection with a zoonotic potential and fatal to dogs in acute and chronic presentations. Exposed the above, this study aims to describe a successful treatment and management of a dog with CanL, CE, and HW comorbidity. Case: A 3-year-old male uncastrated black Labrador dog, weighing 35 kg, was admitted to the veterinary clinic due to immunochromatographic CanL positive test performed by municipal zoonosis control center active surveillance in August 2014. Clinical exam showed a mild shedding, intermittent eye white/yellow discharge and popliteal lymph nodes enlargement. After positive for CanL, veterinary requested more laboratorial exams. IFAT and ELISA were positive for CanL, blood smear showed presence of microfilaria, and bone marrow cytology showed Ehrlichia spp. morulae and microfilaria. Initial treatment prescribed was oral doxycycline, omeprazole, ranitidine, and domperidone for 30 days, and allopurinol and ivermectin until further recommendation. Additionally, repellent collar, repellent spray and vitamin supplement was indicated. After first month, marbofloxacin for 30 days and three doses of immune stimulant protocol were administrated. After three months of treatment, dog still positive for heartworm, ehrlichiosis, and CanL. Doxycycline protocol was repeated. Dog became consistently negative for all pathogens one year later with persistent thrombocytopenia but without clinical signs, ergo allopurinol and ivermectin were discontinued. After four years of follow up, the animal had an acute pancreatitis and died, with unremarkable total blood count and negative for all pathogens. Discussion: CVBD coinfections are commonly reported as worsen prognostic in endemic regions. The pathogens reported here share a host immunomodulation competence. L. infantum and Ehrlichia spp.downregulates Th1 response, whereas D. immitis increase as Th2 profile. The therapeutic protocol was iniciated by staging CanL. Since the patient had clinical signs, allopurinol was prescribed as a well-established drug for CanL. Marbofloxacin was added due to its high safety drug in clinical improvement of infected dogs with and without renal disease and in vitro effectiveness against L. infantum. Domperidone was used to promote Th1 cytokine profile as INF-γ, IL-2, IL-12, and TNF-α. We used an immunostimulant protocol to favor polarization to the Th1 profile comprised by 30 days of domperidone protocol followed by a vaccine and an immunomodulator. Doxycycline was used successfully for Ehrlichia spp. and HE clearance after two treatment courses and one year of ivermectin every 15 days. The animal presented intermittent coughing episodes on the first treatment course, but no medical intervention was needed besides exercise restriction. Our report shows the successful management of one dog with CanL, CE and HE comorbidity. This success was possible due to early detection and good therapeutic choice.Keywords: canine visceral leishmaniosis, coinfection, Dirofilaria immitis, Erhlichia canis, Leishmania infantum, treatment.

Geographic Spatial Distribution Patterns of Dirofilaria immitis and Brugia pahangi Infection in Community Dogs in Chiang Mai, Thailand.

Simple SummaryFilariasis is emerging as a public health concern for humans, dogs, cats, and other wildlife species, and is frequently found in southeast Asian countries. The present study confirmed the species of filarial nematodes in free-roaming dogs from temple communities. Two species were found: Dirofilaria immitis infection and, for the first time, Brugia pahangi. The occurrence of the two species was comparable. Geographic spatial distribution revealed the abundance of D. immitis and B. pahangi in the central areas at altitudes less than 400 m. However, at higher altitudes between 400 and 800 m, we found a significantly higher number of B. pahangi infections than D. immitis infections. In conclusion, D. immitis and B. pahangi were the most common filarial infections found in community dogs in Northern Thailand. Dogs might be an important reservoir for B. pahangi in that region. The population dynamics of the mosquito vector of B. pahangi across altitudinal gradients merits further study.Filariasis is emerging as a public health concern in tropical and subtropical areas. Filariasis is an endemic problem commonly found in southeast Asian countries. Using the PCR-restriction fragment length polymorphism (PCR-RFLP) of the ITS1 region with Vsp I, the overall prevalence rates of Dirofilaria immitis (12.2% (41/337); 95% confidence interval: 9.1–16.1%) and Brugia pahangi (8.3% (28/337); 95% confidence interval: 5.8–11.8%) were determined based on 337 free-roaming community dogs from 20 districts in Northern Thailand. Microfilaremia was found in only 6.2% of dogs (21/337). Co-infection with D. immitis and B. pahangi was observed in two dogs. Of the 215 blood samples examined using a Canine Heartworm Ag Kit, only 3.72% (eight dogs) were D. immitis antigen positive. Among these eight, six dogs had occult D. immitis infections. In terms of geographic distribution, we found the abundance of D. immitis and B. pahangi in the central areas at altitudes less than 400 m to be 12.1% and 10.3%, respectively. In contrast, at higher altitudes between 400 and 800 m, a significantly higher number of B. pahangi compared with D. immitis infected individuals were observed at 14.29% and 4.1%, respectively. In conclusion, D. immitis and B. pahangi were the most common filarial infections found in community dogs in Northern Thailand. Dogs might be an important reservoir of B. pahangi in that region. Increasing awareness and concern and including proper deworming programs for community dogs should be endorsed to reduce the transmission risk. Additionally, the population dynamics of the mosquito vector of B. pahangi across altitudinal gradients deserved further investigation.

Heartworm control in Grenada, West Indies: Results of a field study using imidacloprid 10% + moxidectin 2.5% and doxycycline for naturally-acquired Dirofilaria immitis infections

Canine heartworm disease (CHD) results from infection with Dirofilaria immitis and while it is of global concern, it is most prevalent in tropical climates where conditions support the parasite and vector life cycles. Melarsomine dihydrochloride is the sole treatment for CHD recommended by the American Heartworm Society. However, in cases where cost or access to melarsomine precludes treatment of an infected dog, therapeutic alternatives are warranted. This randomized, controlled field study evaluated the adulticidal efficacy of a combination therapeutic protocol using 10 % imidacloprid + 2.5 % moxidectin spot-on and a single 28-day course of doxycycline and compared with that of a 2-dose melarsomine dihydrochloride protocol. Of 37 naturally-infected domestic dogs with class 1, 2 or early class 3 CHD enrolled in the study, 30 were evaluated for a minimum of 12 months. Seven dogs were withdrawn due to canine ehrlichiosis, non-compliance, or wrongful inclusion. Dogs were randomly assigned to a control (CP, n = 15) or investigational (IVP, n = 15) treatment group. CP dogs received two injections of melarsomine dihydrochloride (2.5 mg/kg) 24 -hs apart and maintained on monthly ivermectin/pyrantel. IVP dogs were treated with oral doxycycline (10 mg/kg twice daily for 28 days) and topical 10 % imidacloprid + 2.5 % moxidectin once monthly for 9 months. Dogs were evaluated up to 18 months - monthly for the first 9 months, then every 3 months. Parasiticidal efficacy was based on antigen status using the IDEXX PetChek® 34 Heartworm-PF Antigen test. By month 18, antigen was not detected in any study dog except one from the IVP group. One other IVP dog was persistently antigenemic and treated with melarsomine at month 12 according to the initial study protocol. Mean antigen concentration (based on optical density) decreased more rapidly in the CP group and by month 15 was 0.11 for the IVP and 0.07 for CP groups, with equivalent median concentrations (0.04) in both groups. Conversion following heat-treatment of antigen-negative samples occurred frequently and at similar rates in both treatment groups. Based on the bias of diagnostic tests towards detection of female worms, we conclude that monthly application of 10 % imidacloprid + 2.5 % moxidectin for 9 months combined with a course of doxycycline twice daily for 28 days resulted in effective therapy against female adults in CHD. This therapeutic option may be particularly useful in cases where financial constraint or access to melarsomine precludes treatment of an infected individual. This study was supported by Bayer Animal Health.