Immitis Infection Research Articles

Model development to assess the impact of a preventive treatment with sarolaner and moxidectin on Dirofilaria immitis infection dynamics in dogs

BackgroundDirofilaria immitis is a mosquito-transmitted filarial parasite causing heartworm disease in dogs. The parasite may cause a significant disease burden to the dog population in high prevalence areas and is mainly managed through prophylactic treatments.MethodsIn this modelling study, the effect of a prophylactic treatment with moxidectin and sarolaner on heartworm disease dynamics was investigated in dogs. A compartmental model was developed to investigate different epidemiological settings considering different values for prevalence and host preference.ResultsWhen the mosquito host preference to dogs is low, a treatment compliance of only 40% decreases the proportion of infectious dogs. When the host preference of the mosquitoes however increases, an exponential increase in infectious dogs was observed, and a higher treatment compliance is required. In high transmission environments, with a high prevalence and a high mosquito host preference, a high treatment compliance (up to 100%) is required to have an impact on the number of infected animals. Notably, in scenarios with higher host preference towards dogs, more mosquitoes are exposed to sarolaner through the blood meal, leading to higher mortality of these mosquitoes and resulting in fewer infected and infectious dogs.ConclusionsThe preventive efficacy, as measured by the number of non-infected dogs, increases with increasing treatment compliance, but the extent of the treatment effect differs with the epidemiological setting. Adding sarolaner to a heartworm prevention has a complimentary impact on mosquito survival and heartworm disease transmission, although this effect depends on the epidemiological settings, emphasizing the true complexity of disease dynamics of a vector-borne disease.Graphical abstract

An indirect ELISA for the detection of antibodies against Dirofilaria spp. in cats

BackgroundDirofilaria immitis and D. repens are mosquito-borne filaroids that primarily infect dogs but also cats. Diagnosing feline dirofilariosis is challenging because of the low parasitic burdens and transient or absent microfilaremia. To improve detection of antibodies against Dirofilaria spp. in cats, an indirect enzyme-linked immunosorbent assay (ELISA) using somatic antigens of D. immitis was standardized.MethodsSerum samples from cats positive for D. immitis, D. repens, bronchopulmonary metastrongylids and gastrointestinal helminths as well as negative sera were tested to evaluate the sensitivity (Se) and specificity (Sp). Three different antigen concentrations (2, 3 and 4 μg/ml) and two concentrations of horseradish peroxidase (HRP) IgG anti-cat conjugate (1:10,000 and 1:20,000) were used to screen the optimal titration of the test. Once the best conditions were established, Se and Sp were assessed by testing 151 serum samples positive for D. immitis, D. repens and other parasites (i.e. feline lungworms, gastrointestinal helminths) or negative.ResultsThe optimized ELISA showed 89% Se and 98% Sp in detecting D. immitis infections, presenting a cross-reactivity with D. repens. A cut-off point of 1.150 was established to classify positive and negative samples.ConclusionsThe developed ELISA may improve the detection of antibodies against Dirofilaria spp. in cats, also in epidemiological contexts characterized by multiple helminth infections. Future efforts will focus on reducing the cross-reactivity with D. repens, therefore increasing ELISA Sp.Graphical

Autoantibodies against phosphatidylserine and DNA during canine Dirofilaria immitis infection.

Autoantibodies against phosphatidylserine and DNA during canine Dirofilaria immitis infection.

Microgeographical Variation in Dirofilaria immitis Prevalence in Dogs in Suburban and Urban Areas of Rio De Janeiro, Brazil.

Dirofilariosis, a mosquito-borne disease caused by Dirofilaria immitis and Dirofilaria repens, affects canids, felids and occasionally humans. Recent evidence suggests that D. immitis prevalence is rising in the canine populations in several areas of Brazil, even those historically considered to be non-endemic, highlighting the need for ongoing surveillance. However, prevalence studies are frequently based on inference from single diagnostic methods, and it is acknowledged that this may lead to biases and an underestimation of the disease situation. Thus, this cross-sectional study aimed to assess the prevalence of Dirofilaria spp. infection in dogs and cats across suburban and urban areas in Rio de Janeiro, Brazil. The investigation was conducted using a multi-diagnostic approach with binomial generalised linear models (GLMs) applied to investigate the association between the occurrence of infection and potential disease determinants. Blood samples from 497 dogs and 107 cats, collected at a veterinary mobile neutering unit, underwent parasitological, serological and molecular testing to detect Dirofilaria spp. infections. Among the dog samples, an overall 7.44% tested positive for D. immitis infection, while D. repens was not detected. In contrast, no cat samples tested positive for either parasite species. Prevalence was notably higher in suburban areas (14.47%) than in the urban area of Rio de Janeiro (6.17%) (p = 0.003). Dogs aged over two years had a higher risk of being infected (p < 0.001), while features such as breed, sex, size, coat type, use of macrocyclic lactones or access to outdoor spaces were not found to be predictive factors. This study reinforces the evidence that the prevalence of D. immitis is increasing in areas previously considered to have low prevalence or to be non-endemic. It also suggests that environmental and socioeconomic factors may play a key role in determining the current epidemiological status of this parasite. These findings highlight the need for increased monitoring in high-risk areas, targeted prevention and public awareness to address this emerging One Health concern.

Prevalence of Dirofilaria immitis in dogs in Jamaica.

Dirofilaria immitis is a zoonotic vector-borne parasite that causes heartworm disease most commonly in canines. Although present in the Caribbean, no published work exists from Jamaica. Therefore, the aim of our study was to evaluate the prevalence of D. immitis in Jamaica. From June to December 2022, whole blood samples from 1000 dogs were collected from all parishes and tested using the Bionote Canine Heartworm Antigen Test Kit 2.0. Dogs that were at least 6months old, privately owned, residing in shelters, working in the security sector, or strays were recruited into the study. Details on the breed, known or approximate age, sex, use of heartworm prophylaxis, and other medications and location of animals were provided by owners/authorizing agents and recorded. Test results were available for 986 dogs of which 184 tested positive, with an overall prevalence of 18.7% (95% CI, 16.28 to 21.24). Mature adults (2-6years) comprised most of our sampled population (46.7%), followed by early seniors (7-9years) (20.1%) and young adults (13-24months) (9.9%). Prevalence for those age groups was 21.9%, 19.5%, and 7.1%, respectively. A seropositivity of 25.1% was seen in dogs not on heartwormpreventative medication compared to 5.5% of dogs on heartwormpreventative medication. Our study highlights a higher seroprevalence of D. immitis infections in older dogs and provides evidence supporting the use of preventive medication in the country.

Radiological Evaluation of Vascular Structures in Cats Infected with Immature Worms of Dirofilaria immitis.

This study aimed to assess thoracic radiographic abnormalities in cats infected with immature stages of Dirofilaria immitis to evaluate the utility of this diagnostic technique during early infection. A total of 123 cats from a hyperendemic area were classified into three groups: asymptomatic cats seronegative to anti-D.-immitis antibodies (Group A), seropositive asymptomatic cats (Group B), and seropositive cats with clinical signs that were at high risk of heartworm-associated respiratory disease (HARD) (Group C). Radiographic measurements and lung parenchymal abnormalities were analyzed and compared across the groups. Significant differences in several parameters, including CrPA/R4, and CdPA/R9 ratios, were observed between healthy and seropositive cats, suggesting early arterial damage even in the absence of adult worms. Other parameters that showed differences between healthy and infected cats were CVC/Ao and CVC/R4 ratios, but not the VHS. Group C exhibited a marked bronchointerstitial pattern, indicating severe parenchymal alterations associated with clinical signs. The study demonstrated that thoracic radiography can detect early vascular and parenchymal changes in feline D. immitis infections, providing valuable information for diagnosing HARD. However, it also highlights the limitations of radiographic techniques, as some seropositive cats displayed no significant abnormalities. The findings underscore the importance of combining radiography with clinical and serological assessments for a more accurate diagnosis of feline heartworm disease.

Wolbachia infection in Aedes aegypti does not affect its vectorial capacity for Dirofilaria immitis.

Mosquito-borne diseases such as dengue and filariasis are a growing public health concern in endemic countries. Biological approaches, such as the trans-infection of Wolbachia pipientis in mosquitoes, are an alternative vector control strategy, especially for arthropod-borne viruses such as dengue. In the present study, the effect of Wolbachia (wMel strain) on the vectorial capacity of Aedes aegypti for Dirofilaria immitis was studied. Our results showed that Wolbachia does not affect the phenotype of mosquito survival or the prevalence, number, and molting rate of third-stage larvae in both susceptible and resistant strains of Ae. aegypti. RNA-seq analysis of Malpighian tubules at 2days post-infection with D. immitis showed the differentially expressed genes (DEGs) with and without wMel infection. No characteristic immune-related gene expression patterns were observed among the DEGs. No significant change in the amount of Wolbachia was observed in the Ae. aegypti after D. immitis infection. Our results suggest that infection of D. immitis in Ae. aegypti populations will not interfere with Wolbachia-based vector control strategies in dengue-endemic areas where cases of D. immitis are present. This study demonstrated the veterinary medical validity of a dengue control program using Wolbachia.

Prevalence, spatial distribution and risk mapping of Dirofilaria immitis in wild canids in southern Québec, Canada

Domestic dogs (Canis familiaris) and wild canids, including coyotes (Canis latrans) and red foxes (Vulpes vulpes), serve as definitive hosts for Dirofilaria immitis, a parasitic nematode causing the heartworm disease. Understanding infection risks in wildlife reservoirs in relation to environmental factors is crucial for assessing exposure risk in domestic dogs. The regional prevalence of D. immitis infection was estimated in trapped wild coyotes and red foxes across Québec, Canada. Spatial clusters of infection were detected using Kulldorff's spatial scan statistics. A series of logistic regression models predicting the D. immitis status in coyotes were built from heartworm development unit (HDU) estimates and cumulative precipitation variables over various time periods. Between October 2020 and March 2021, 421 coyotes and 284 red foxes were examined for the presence of D. immitis. The parasite was found in 43 coyotes and 1 red fox. A high-risk infection cluster was detected in coyotes in southwestern Québec. The best model included as sole predictor the average cumulative HDU contributing to risk of D. immitis in the three years preceding coyote capture. This model significantly predicted infection status with an area under the curve of 76.1%. The cumulative precipitation had no notable effect in any model. This study highlights a high prevalence of D. immitis in coyotes in Québec with regional differences correlated to temperature-derived predictors. The spatial risk of infection in this population likely represents the environmental risk of exposure to the parasite given that coyotes do not receive preventive treatment compared to domestic dogs. Our findings are important for veterinarians in the application of prevention strategies for heartworm disease in domestic dogs.

Heartworm (Dirofilaria immitis) Prevalence in Dogs Determined by In-House ELISA Based on Filaria-Specific Antibodies in Tropical and Temperate Regions of Mexico

Dirofilaria immitis is a mosquito-borne nematode of dogs, other carnivores and, occasionally, humans. Globally, D. immitis infection (which causes heartworm) is typically more prevalent in tropical than temperate regions. In this study, the seroprevalence of D. immitis was determined from a sample of 335 non-stray dogs from four municipalities, two each from the states of Puebla and Guerrero in Mexico, using polyclonal antibodies to detect serum antigens using an enzyme-linked immunosorbent assay (ELISA). The accuracy of the assay was compared with the modified Knott’s test. The polyclonal antibody used in the direct ELISA had a high sensitivity (100%) with variable specificity (98.2–98.8%) in the municipalities of Puebla and Guerrero. The area under the curve for the four municipalities was 1.0, indicating a high accuracy test, with a cut-off value ranging from 0.45 to 0.50. The overall prevalence of D. immitis infection was 17.56% (59 out of 335). The highest prevalence was in Acapulco (24.78%), followed by Chilpancingo (20.93%), Tecamachalco (10.81%) and Quecholac (8.06%). The highest percentage of positive samples was detected in tropical regions (23.12%) and the lowest in temperate regions (9.56%). This study demonstrates that polyclonal anti-D. immitis antibodies can successfully diagnose heartworm-infected dogs and be used to monitor prevalence effectively and develop prevention strategies against Dirofilaria infection.

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.

Evaluation of Seroprevalence and Risk Factors of Heartworm Infection for Dogs in Rio de Janeiro with Access to Veterinary Care

Heartworm infection is a chronic disease with clinical signs and effects ranging from an asymptomatic condition to severe disease and death. The prevalence of heartworm disease in the state of Rio de Janeiro has been reported to be high (21.3%). The present study was conducted to evaluate the seroprevalence and risk factors of heartworm infection for the canine population with access to veterinary services in different areas of the state of Rio de Janeiro, Brazil. A total of 1787 canine blood samples were obtained from 135 practices across 8 different areas of Rio de Janeiro state (Rio de Janeiro municipality, São Gonçalo municipality, Niterói municipality, Baixada Fluminense, and the northern, southern, eastern, and mountainous areas) and tested for the presence of Dirofilaria immitis antigens and antibodies against several tick-borne disease pathogens using a commercial immunochromatography technique (Vetscan® Flex 4 Rapid Test; Zoetis; NJ USA). Pet owners reported living conditions, physical characteristics, demographics, and clinical signs for evaluation of risk factors for heartworm infection. Only two evaluated risk factors were shown to enhance the risk for D. immitis infection, including having a short hair coat vs. having a medium or long hair coat (OR 2.62) or positive for antibodies to tick-borne disease parasites (OR 3.83). Clinical signs reported for dogs with heartworm disease were typical for that condition. The overall prevalence of heartworm disease in the state was 8.2%, ranging from 2.4% in the mountainous region to 29.4% in the eastern area. It could not be determined if veterinarians were not diligent about dispensing heartworm preventatives or if poor levels of compliance by dog owners were responsible for higher infection rates in some areas of the state.

Beyond Borders: Dirofilaria immitis Infection in Dogs Spreads to Previously Non-Enzootic Areas in Greece-A Serological Survey.

Although Dirofilaria immitis in dogs is considered enzootic in northern Greece, the available data on the occurrence of infection in southern parts of the country demonstrate its scarcity. The aim of this study was to update the current knowledge on D. immitis infection in dogs in areas of Greece previously considered non-enzootic (Central Greece, Attica, Peloponnese, North Aegean, South Aegean, Crete and the Ionian islands). In total, 1528 dog blood samples were collected from the aforementioned areas and examined by Dirochek® ELISA (Synbiotics). Additionally, data published until 2022 on the prevalence of infection in these areas were compared to the data of this study. The 'Wilson' Score interval method (Epitools) was employed. Overall, 10.8% of dogs were positive for D. immitis. In detail, the prevalence was 21.7, 13.7, 10.7, 5.4, 4.7, 6.2 and 17.0% for D. immitis, in Central Greece, Attica, Peloponnese, North Aegean, South Aegean, Crete and the Ionian islands, respectively. Infection with D. immitis is recorded for the first time in Crete. The probability of a dog becoming infected has increased 4.1 times since 2022 in previously non-enzootic areas. This study denotes the spread of D. immitis and highlights the necessity for preventive measures.

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.

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.

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

Prevalence and risk factors of canine dirofilariasis in Kano metropolis, Kano State Nigeria

Dirofilariasis is a zoonotic disease caused by Dirofilaria immitis causes heartworm disease and invasive human filariasis. This study determined the prevalence and risk factors for the acquisition of canine dirofilariasis in dogs in Kano metropolis, Kano state, Nigeria. Blood samples were collected from 170 dogs of 6 months and above in Kano metropolis and tested by the Modified Knott’s technique for circulating microfilaria, an Enzyme-linked Immunosorbent Assay in order to detect the presence of filarial antigens of D. immitis as evidence of occult infection. A pre-tested, structured questionnaire was administered to each of the dog owner to obtain demographic, management and environmental information associated with each dog sampled. Test for association and hypothesized factors was determined and the its strength was tested using a binary logistic regression. Out of the 170 dogs tested, 17 (10.00%) were positive for D. immitis infection with the Modified Knott’s technique. However, after subjecting the samples for antigen detection by ELISA tests 23 (13.53%) were positive for D. immitis antigen, giving a sero-prevalence of 13.50%. There was agreement between the two tests on the 17 microfilaria positive samples. Majority of the infected dogs were males (56.5%), aged 24-47 months (43.50%) and of local breed (65.2%). There was significant association (p ≤ 0.05) between D. immitis infection and dogs usage, breed and dogs with stagnant water (gutters) close to their houses (OR= (9.714; 95% CI (1.179-80.024)), OR=5.33; 95% CI (1.349-21.079), OR= 5.775; 95% CI (0.697- 47.832),respectively. The study established that D. immitis infection is prevalent (13.53%) in household dogs indicating the possibility of zoonotic transmission in Kano metropolis. This demands for intensified vector control and good dog management practices to reduce dog to dog and dog to human transmission.

Is the European badger a new host for Dirofilaria immitis? The first records in Greece

Dirofilaria immitis is a ubiquitous nematode parasite with zoonotic potential, transmitted by mosquitoes, that causes heartworm disease in various animal species. Dogs are the parasite’s typical final host, and wild carnivores represent the parasite’s reservoir in nature. Studies on D. immitis infections in wild animals are essential to assess infection pressure for domestic animals, and until now, there has been only one infection case reported in a European badger (Meles meles). The current report describes the first two European badger cases with cardiovascular dirofilariosis in Greece. Two adult male badgers were rescued in Heraklion and Chania, Crete Island, and admitted to “ANIMA -Wildlife Rehabilitation Centre” in Athens. The detailed clinical examination revealed that the first badger suffered from severe broncho-pneumonitis while the second one displayed clinical signs associated with severe brain trauma. Blood samples were taken for haematology and biochemistry analyses during their short hospitalisation period. In addition, different routine diagnostic tests were carried out, including heartworm antigen testing (ELISA) and the modified Knott’s test for microfilariae. Both badgers were positive in both tests. The animals died a few hours after their admission and the detailed necropsies followed, revealed the presence of three parasites in each animal’s right heart, morphologically identified as adults of D. immitis. These findings add the European badger in the list of additional potential reservoir hosts for D. immitis and highlight the potential role of wildlife for companion animals and human health.

Development of adult Dirofilaria immitis worms in the Rag2/Il-2rγ-/- mouse model

Dirofilaria immitis is the causative agent for one of the major parasitic infections in dogs. It is currently not possible to reliably diagnose the infection before the development of fertile adult female worms and the presence of microfilariae which takes six to 7 months. However, at this point adult worms already reside in the pulmonary arteries and can cause significant damage. Novel in vivo models may facilitate the development of new diagnostic tools and improve treatment options for both the early and late stages of D. immitis infections. In this paper, we aimed to increase the capabilities of recently published mouse models in which severely immune-deficient mice were shown to be susceptible to D. immitis. Our data shows that D. immitis may grow into fully developed mature male and female worms in C57BL/6 Rag2/Il-2rγ-/- mice with comparable growth rates to the natural canine host. The adult worms of D. immitis were shown to migrate into body cavities as well as the heart in this model. However, the presence of adult worms inside the heart of infected mice led to the development of caval syndrome in 36% of infected mice after five to 6 months. Overall, the current study complements recently published efforts to establish a D. immitis mouse model by extending the development of D. immitis into mature adult stages and will facilitate further preclinical research.

Dirofilaria immitis in dogs from the coastal tourist region of the state of Alagoas, Brazil.

Canine dirofilariasis, caused by Dirofilaria immitis, is prevalent worldwide. However, the frequency of canine infection in the state of Alagoas, Brazil is scarcely unknown. This study aimed to evaluate the frequency of D. immitis infection in dogs from the coastal municipalities of Alagoas and analyze the risk factors associated with the infection. A cross-sectional study was performed using 426 dogs of different breeds and sex distributed across 15 coastal municipalities in the state of Alagoas. Blood samples were collected from each dog and analyzed for circulating microfilariae and free D. immitis antigens. To investigate the risk factors associated with D. immitis infection, we collected information on dog environments using an epidemiological questionnaire. The results revealed that 12.7% of dogs tested positive for D. immitis. Dogs with travel history were 3.52 times more likely to be infected. Thus, infected dogs in the coastal region of Alagoas should be regularly monitored and the public health system should plan strategies to control this zoonotic disease.

Prevention of heartworm infection in dogs using a combination of moxidectin, imidacloprid and praziquantel: evidence from a randomized clinical trial.

The aim of this study was to evaluate the efficacy of a topical combination of moxidectin 3.5%, imidacloprid 10% and praziquantel 10% for the prevention of Dirofilaria immitis (Leidy, 1856) infection in dogs. For this purpose, a randomized and controlled clinical trial was conducted between August 2021 and October 2022, in the municipality of Goiana, state of Pernambuco, north-eastern Brazil, where heartworm is highly prevalent. Of the 213 dogs initially sampled (baseline), 68 (31.9%) were positive for adult antigens (SNAP 4Dx Plus, Idexx) and/or microfilariae (modified Knott's test). On day 0, 140 negative dogs were randomly included in the treatment and control groups, 70 animals each. During the study, 60 dogs (34 treated and 26 untreated) were removed for different reasons. At the end of the study (day 360 ± 2), 36 treated and 44 untreated were sampled and included in the efficacy calculation. The efficacy against the development of adults and microfilariae was 84.7%, with only one treated dog being positive for adult antigens but negative for microfilariae. On the other hand, eight untreated dogs were positive for adultantigens and/or microfilariae, resulting in a significant difference in the number of positives between groups (Chi-square test = 4.706, df = 1, P = 0.0301). Remarkably, the efficacy against the appearance of D. immitis microfilariae was 100% (i.e., all treated dogs negative) and three untreated dogs were positive for microfilariae. The topical combination of moxidectin 3.5%, imidacloprid 10% and praziquantel 10% significantly reduced the risk of D. immitis infection in treated dogs as compared with untreated dogs, in a highly endemic area in north-eastern Brazil.