Usefulness of NT-proBNP in dogs with heartworm: could this biomarker be useful to evaluate pulmonary hypertension?

BACKGROUND: In recent years, the usefulness of echocardiography and serum biomarkers in the diagnosis of pulmonary hypertension (PH) in dogs with heartworm disease has been studied. Previously, N-terminal pro B-type natriuretic peptide (NT-proBNP) has shown high concentrations in dogs with heart disease and/or PH as well as its usefulness as a prognostic indicator, but it has never been evaluated in the diagnosis and prognosis of PH in dogs with heartworm disease. The aim was to evaluate the serum concentrations of NT-proBNP in dogs infected by Dirofilaria immitis to determine its usefulness as a tool to detect precapillary PH. METHODS: NT-proBNP was determined in 50 heartworm-infected dogs. Presence/absence of PH was determined echocardiographically, using the Right Pulmonary Artery Distensibility Index (RPAD Index) and the systolic flow of tricuspid regurgitation mainly, together with other echocardiographic measurements following the guidelines of the American College of Veterinary Internal Medicine (ACVIM) for the diagnosis of PH. Other epidemiological parameters (breed, age, sex, status: client-owned or shelter dogs) and clinical parameters (microfilaremia, parasite burden, presence of symptoms, body condition) were collected as well. RESULTS: Moderate-severe PH was present in 40% of the dogs (RPAD Index < 29.5%), NT-proBNP concentrations being significantly higher compared with dogs that did not have PH. A cutoff for NT-proBNP of ≥ 1178.45 pmol/l showed a sensitivity of 64.3% and a specificity of 95.5% for the presence of moderate-severe PH. Older dogs and dogs from shelters showed significantly higher NT-proBNP concentrations. Dogs with symptoms and low body condition presented significantly higher NT-proBNP concentrations as well. CONCLUSIONS: The determination of NT-pro-BNP concentration can be a useful tool in the diagnostic work-up of dogs with heartworm disease and associated PH and can help to identify animals in the more advanced stage of this disorder.

Feline heartworm disease and environmental allergens hypersensitivity: is there a link?

BACKGROUND: Cats can be infected by Dirofilaria immitis, the causative agent of heartworm disease, characterized by respiratory signs, airway hyperreactivity, remodelling and inflammation. Allergy is a multifactorial pathology, and the role of a number of helminth parasites in the development of allergies in humans and other species has been demonstrated in many studies. The aim of the present study was to verify whether cats seropositive for D. immitis present hypersensitivity to some environmental allergens. METHODS: Blood samples were collected from 120 cats and tested for the presence of specific immunoglobulin G antibodies against D. immitis and for hypersensitivity to 20 allergens, using commercial allergen test kits. RESULTS: Of the 120 cats tested, 72 (60.0%) were seropositive for anti-D. immitis IgG and 55 (45.8%) showed clinical signs of heartworm disease of a respiratory nature. The results of testing with the allergen kits showed that 50.8% of cats were seropositive for ≥ 1 allergens, with the most common allergens being Dermatophagoides farinae (25.8%), Dermatophagoides pteronyssinus (20.0%), Malassezia (17.5%) and Ctenocephalides felis (14.2%). The prevalence of allergies was significantly higher-by almost threefold-in cats seropositive for D. immitis (68.1% vs. 25%). There were no significant differences between the prevalence of allergic cats and presence/absence of symptoms, and the results confirmed that symptoms were not a decisive factor for the presence of allergies. The risk for developing allergies was 6.3-fold higher in cats seropositive for D. immitis than in cats that were seronegative, confirming that seropositivity for D. immitis is a risk factor. CONCLUSIONS: Cats with confirmed heartworm can develop serious respiratory signs, potentially leading to progression to permanent lung injury and predisposing cats to hyperresponsive airway disease. Previous studies have shown that seropositivity for D. immitis and Wolbachia is related to the presence of bronchoconstriction and bronchospasm in the affected cat. The results support the suspicion that contact with D. immitis may be a risk factor for the presence of allergies.

Echocardiographic Assessment of the Pulmonary Vein to Pulmonary Artery Ratio in Canine Heartworm Disease.

Background:Dirofilaria immitis produces proliferative pulmonary endarteritis and pulmonary thromboembolism in infected dogs. The pulmonary vascular lesions lead to irreversible and persistent structural damage and, as a consequence, sustained precapillary pulmonary hypertension (PH). The purpose of this study was to assess the diagnostic value of the pulmonary vein to pulmonary artery ratio (PV:PA ratio) to determine moderate or severe PH (>50 mmHg) in dogs with heartworm disease. METHODS: A total of 151 naturally heartworm-infected and 66 healthy dogs were included in the study. The presence/absence of PH was based on the right pulmonary artery distensibility index (RPAD index < 29.5%), and the PV:PA ratio was echocardiographically measured by the time-motion mode (M mode) and two-dimensional mode (2D mode). Other echocardiographic parameters were also assessed (pulmonary trunk to aorta ratio, tricuspid regurgitation pressure gradient, and AT:ET ratio). RESULTS: The results of the PV:PA ratio showed a highly positive correlation between the M and 2D modes (r = 0.928). The PV:PA ratio obtained by the M mode was identified as the strongest predictor for RPAD index (R2 0.628, p < 0.0001) with a good diagnostic accuracy (AUC = 0.99). The results of PV/PA by the 2D mode showed a similar prediction for the RPAD index (R2 0.606, p < 0.0001) with a good diagnostic accuracy (AUC = 0.98). Both of the 2D and M modes' PV:PA ratios decreased significantly with the presence of PH. A cut-off value of ≤0.845 showed high sensitivity and specificity for the M mode (97% and 94%, respectively) and the 2D mode (96% and 93%, respectively). CONCLUSIONS: The PV:PA ratio may be useful as a complementary diagnostic method for the estimation of moderate or severe PH in dogs with heartworm.

Evaluation of Pulmonary Hypertension in Dogs with Heartworm Disease Using the Computed Tomographic Pulmonary Trunk to Aorta Diameter Ratio.

Dirofilaria immitis causes proliferative pulmonary endoarteritis that leads to the appearance of chronic precapillary pulmonary hypertension (PH) in dogs. Pulmonary trunk to aorta ratio (PT:Ao ratio) obtained by computed tomography (CT) was studied and the quantitative measure of the diameters of the pulmonary trunk (PT), the descending thoracic aorta (DAo) and ascending thoracic aorta (AAo) were evaluated for the determination of the presence of moderate to severe PH in 59 dogs. The diagnosis of PH was echocardiographically determined, based on the determination of the right pulmonary artery distensibility (RPAD) index (<29.5%), and compared with other parameters for estimating PH. The results showed a very high concordance: 0.976 (p-value 0.000) between the two CT methods (PT:DAo and PT:AAo) with an excellent intraclass correlation coefficient > 0.95. Moreover, cut-off values of ≥1.111 for PT:DAo, and ≥1.057 for PT:AAo were determined for dogs with an RPAD index < 29.5%, which suggests a cut-off value between healthy dogs and the presence of PH. As has been previously published, The PT:Ao ratios did not determine the presence of mild PH, so the measurements cannot be considered useful for the early diagnosis of PH in dogs with heartworm.

Expansion of Canine Heartworm in Spain.

The climate of Spain has favourable characteristics for the development of D. immitis in dogs, being an endemic country. Given that vector-borne diseases are spreading rapidly through Europe, due to factors such as climate change, the expansion of vectors and the increased mobility of reservoir animals, the aim was to update the epidemiology of heartworm in dogs and analyse the results based on climate and other epidemiological and geo-environmental factors. To this aim, 9543 blood samples from dogs from all provinces and autonomous cities of Spain were analysed for the detection of antigens of D. immitis, obtaining a prevalence of 6.47%. The northwestern and southern provinces showed the highest prevalences, as well as in the Balearic and Canary Islands. Prevalences were higher in dogs outdoors. Furthermore, most of the positive dogs were found in regions with high humidity and water availability. This study shows, for the first time, positive cases in provinces and islands where no cases had previously been described and demonstrates the continuous expansion and consolidation of heartworm in Spain. Considering its zoonotic character, the implementation of control and awareness programmes for the prevention of D. immitis in pets is necessary.

Current Distribution of Selected Vector-Borne Diseases in Dogs in Spain.

Currently, climate change, modifications of landscapes and habitats due to human activities, as well as an increase in the movement of reservoirs and new species of competent vectors, have contributed to the spread of canine vector-borne diseases. These are mostly emerging and neglected diseases, some of them with zoonotic potential. Therefore, the objective of this study was to assess the prevalence and distribution of four major canine vector-borne diseases (Dirofilaria immitis, Leishmania infantum, Anaplasma spp., and Ehrlichia canis) in Spain. Between September 2018 and February 2020, blood was sampled from 4643 client-owned dogs from 111 veterinary clinics from the 17 autonomous communities of Spain. All samples were tested for the detection of D. immitis antigens, and for antibodies against L. infantum, Anaplasma spp. and E. canis. Of the studied dogs, 22.14% were positive for one or several diseases while the prevalence was 6.25% (CI: 5.59-6.98) for D. immitis, and the seroprevalences were 10.36% (CI: 9.52-11.27) for L. infantum, 5.06% (CI: 4.47-5.73) for Anaplasma spp., and 4.26% (CI: 3.72-4.88) for E. canis. Co-infections by two and three vector-borne diseases were reported in 13% and 2% of the infected dogs, respectively. The studied vector-borne diseases are widely distributed throughout the Spanish geography, being observed and expanding northward in the case of D. immitis and L. infantum. The results point to an insufficiency of preventive measures to avoid the infection, and the need of the implementation of awareness campaigns among veterinarians and owners. Furthermore, a close collaboration between veterinarians, physicians and health authorities would be necessary for such zoonotic vector-borne diseases.

Dirofilaria immitis Could Be a Risk Factor for the Development of Allergic Diseases in Humans.

The Canary Islands are hyperendemic for canine heartworm and the risk of zoonotic infection is high. Additionally, there is evidence of development of allergies due to nematode infections in animals and humans. Since the population of the Canary Islands presents high prevalence of allergic comorbidities, and previous studies have shown a possible relationship between allergies and seropositivity to heartworm, the aim was to evaluate whether exposure to heartworm may contribute to the development of allergies in the human population. First, an epidemiological study was conducted on 248 owners of dogs with/without heartworm infection in the Canary Islands. Secondly, a serological analysis of the presence of total IgE and specific IgE against heartworm was conducted in 66 samples of inhabitants of the Canary Islands. The survey showed that allergic owners had heartworm-positive dogs more frequently (p < 0.01). Of the analyzed human samples, 43.9% were seropositive to heartworm and Wolbachia. Total IgE concentrations were increased in 34.5% seropositive samples and 8.1% seronegative samples. Specific IgE against heartworm was only found in human seropositive samples (17.2%). Contact with heartworm may be a risk factor for the development of allergic diseases, although further studies to elucidate the relationship between heartworm and allergies should be carried out.

First epidemiological survey of Angiostrongylus vasorum in domestic dogs from Spain.

BACKGROUND: Angiostrongylus vasorum is the causative agent of canine angiostrongylosis, a disease that mainly affects domestic dogs and other wild carnivores. In Europe, the number of infected individuals is increasing, being located in central and southern countries. In Spain, several studies have reported high prevalence of A. vasorum in wild animals. However, there are no studies addressing the current situation of the disease or its distribution in domestic dogs, and reports from veterinary personnel are very limited. Considering these facts, the objective of the present study was to evaluate the prevalence of A. vasorum in different areas of Spain. METHODS: Between November 2018 and October 2019, blood was sampled from a total of 2024 domestic dogs from six zones of Spain with a climate that favours the establishment of the disease, where all dogs included in the study lived outdoors or had regular access to areas with vegetation and none had travelled outside the study area of interest in the past year. Details about their sex and age were collected. All dogs were tested for the presence of A. vasorum circulating antigens using Angio DetectTM. RESULTS: The overall prevalence of canine angiostrongylosis in the studied areas of Spain was 1.73%. No differences in overall prevalence were found between males and females, neither between age groups. Regarding eco-epidemiological areas, the highest prevalence was recorded in the zones located in the north and northwest of Spain (1.86-2.74%), which correspond to the wetter climates and most abundant vegetation, and the lowest prevalence was detected in the zones located in the center and west of Spain (0.93-0.99%). CONCLUSIONS: Our data suggest that angiostrongylosis is present in Spain in domestic dogs where previously infected wild animals existed or where climatic conditions are favourable for the establishment of the disease.

The Canary Islands as a model of risk of pulmonary dirofilariasis in a hyperendemic area.

We assessed the risk of human pulmonary dirofilariasis in the Canary Islands, hyperendemic for canine heartworm (Dirofilaria immitis), a zoonotic vector-borne infection. For this purpose, 1479 inhabitants were tested for anti-D. immitis antibodies. Four of the 7 islands presented high seroprevalences (from 6.2 to 12.7%), therefore high exposure to the parasite and risk of zoonotic infection. These corresponded to those islands with high canine prevalences of dirofilariasis and favourable climatic conditions for the development of mosquito vectors. The lowest prevalences (from 0 to 1.6%) were found in the desert islands and those with low canine prevalences of heartworm. Seroprevalences were very variable inside each island as well, being related to the climate and demographic factors. Human pulmonary dirofilariasis is an emerging zoonosis worldwide which frequently goes undiagnosed. Serological studies could be useful for the correct evaluation of the risk of infection among the human population, and study of the health implications of the continuous contact with the parasite in endemic areas. Sanitary authorities should be aware of the current epidemiological data, and physicians should include human dirofilariasis in the differential diagnosis of pulmonary nodules.

Prevalence of heartworm in dogs and cats of Madrid, Spain.

BACKGROUND: Dirofilaria immitis causes heartworm disease, a chronic and potentially fatal cardiopulmonary disease which mainly affects dogs and cats. It is present in most of Spain, due to favourable climatic factors. Madrid, located in the centre of the Iberian Peninsula, is the most highly populated city in the country. There is a lack of current data on canine heartworm and there are no published epidemiological data regarding feline heartworm in this region, therefore the aim of this study was to assess the prevalence and current distribution of canine and feline dirofilariosis in the province of Madrid. METHODS: Serum samples from 1716 dogs and 531 cats, from animals living in the metropolitan area of Madrid and adjacent areas, were studied. All the samples, either from cats and dogs, were tested for circulating D. immitis antigens using a commercial immunochromatographic test kit. Furthermore, to establish the seroprevalence of heartworm infection in cats, serological techniques for anti-D. immitis and anti-Wolbachia antibody detection were used. RESULTS: Prevalence of D. immitis in the canine population of Madrid was 3%, showing an increase in comparison to previous data. The presence of heartworm in the city centre could be influenced by the presence of Urban Heat Islands, while the positive dogs from metropolitan and adjacent areas were mainly located under the influence of rivers. Regarding cats, 0.2% were positive to the antigens test and 7.3% were seropositive to both anti-D. immitis and Wolbachia surface protein antibodies, which demonstrate the presence of feline heartworm in Madrid. Seropositive cats were present in the same areas where positive dogs were found. Indoor/outdoor cats showed the highest seroprevalence whereas the lowest corresponded to indoor cats, demonstrating that prophylactic treatments should be carried out regardless of lifestyle. Infection was found in 2.2% of dogs and 6.7% of the cats < 1 year-old, which indicates that early preventive campaigns in puppies and kittens should be implemented. CONCLUSIONS: The results point to the need for adequate prophylactic measures through the administration of macrocyclic lactones in animals living in Madrid. Veterinarians should be aware of the presence of this disease and include heartworm in the differential diagnosis when a pet presents with symptoms compatible with D. immitis.

Potential Role of Pet Cats As a Sentinel Species for Human Exposure to Flame Retardants.

Flame retardants are a wide group of chemicals used by the industry to avoid combustion of materials. These substances are commonly found in plastics, electronic equipment, fabrics, and in many other everyday articles. Subsequently, ubiquitous environmental contamination by these common chemical is frequently reported. In the present study, we have evaluated the level of exposure to polychlorinated biphenyls (PCBs), brominated diphenyl ethers (BDEs), and organophosphorous flame retardants (OPFRs) in pet cats through the analysis of their serum. We also analyzed the level exposure to such chemicals in a series of 20 cat owners, trying to disclose the role of pet cats as sentinel species of human exposure to FRs. Our results showed that PCBs, banned 40 years ago, showed the lowest levels of exposure, followed by BDEs-banned recently. Congeners PCB-138 and PCB-180 were detected in ≥50% of the series, while BDE-47 was detected in near 90% of the pet cats. On the other hand, the highest levels were that of OPFRs, whose pattern of detection was similar to that observed in humans, thus suggesting a potential role of cats as a sentinel species for human exposure to these currently used FRs. Six out of 11 OPFRs determined [2-ethylhexyldiphenyl phosphate, tributylphosphate, triisobutylphosphate, triphenylphosphate, tris (2-chloroethyl) phosphate, and tris (2-chloroisopropyl) phosphate] were detected in 100% of the samples. It will be interesting to perform future studied aimed to elucidating the potential toxicological effects of these highly detected chemicals both, in cats and humans.

The heartworm (Dirofilaria immitis) seems to be able to metabolize organochlorine pesticides and polychlorinated biphenyls: A case-control study in dogs.

It has been described that the co-existence of parasite infection and chemical exposure has various effects on the accumulation of persistent organochlorine pollutants (POPs) in the host. Certain parasites are not only able to accumulate POPs but also seem to have the ability to metabolize certain compounds. We have designed a case-control study aimed to disclose the role of Dirofilaria immitis in the bioavailability of POPs in dogs trying to know whether these parasites store or metabolize the POPs. A total of 40 common POPs (18 polychlorinated biphenyls congeners (PCBs) and 22 organochlorine pesticides were quantified in dog serum. The study included three groups of dogs prospectively recruited in the island of Gran Canaria (Canary Islands, Spain): a) control animals, non-parasitized (serologically tested negative, n=24); b) a group constituted by dogs tested positive for heartworm disease (D. immitis) and negative for other parasites (n=25); and c) the same group of parasitized dogs after the treatment against the parasite (n=25). The presence of D. immitis was strongly associated with lower serum levels of a wide range of pollutant in their hosts (PCB congeners 28, 105, 118, 123, 138, 153, 167 and 180; hexachlorobenzene, lindane, aldrin, dieldrin, and methoxychlor). The serum levels of these substances remained at very low levels after the treatment against the parasite, suggesting that D. immitis do not simply store such compounds, but they probably have some ability to metabolize these pollutants. We encourage the use of the parasite infestation status as a cofactor that needs to be taken into account in studies aimed to evaluate the serum levels of POPs.