Immitis Infection Research Articles

Can heartworm prevalence in dogs be used as provisional data for assessing the prevalence of the infection in cats?

Cats are considered a susceptible host for Dirofilaria immitis; however, increased host resistance is reflected by relatively low adult worm burdens in natural and experimental infections; the prolonged prepatent period (8 months); the low level and short duration of microfilaremia; and the short life span of adult worms (2–3 years). From April to September 2006, 212 cats and 608 dogs, all exposed for at least one transmission season, were screened for D. immitis infection in a multi-center study in the Po River Valley in northern Italy. Cats were initially evaluated by antibody testing; positive subjects were followed up by antigen testing and echocardiography (and necropsy if death occurred). The prevalence in dogs was 29% by a modified Knott test and antigen testing compared with a prevalence of 4.7% in cats by an antibody test; six of these infections (2.8%) were confirmed by the follow-up evaluations. This field study demonstrated that the prevalence of heartworm infection in cats in this area is within the expected limits of 9–18% of the prevalence in dogs. Antibody testing likely underestimates the real prevalence of D. immitis infection in cats. These results also emphasize the importance of preventive treatment in cats.

Dirofilaria immitis infection in dogs: Cardiopulmonary biomarker levels

Cardiopulmonary biomarkers are biological parameters that can be objectively measured and quantified as indicators of pathogenic processes (heartworm disease) or as indicators of response to therapeutic intervention. To determine levels of cardiopulmonary biomarkers in canine dirofilariasis, measurements of cardiac troponin T, cardiac troponin I, myoglobin, and D-dimer concentrations were performed for dogs with and without evidence of adult heartworm infection. The results showed that levels of cardiac troponin T were undetectable in all dogs studied while levels of cardiac troponin I were higher in dogs infected with Dirofilaria immitis. In healthy dogs, levels of myoglobin and D-dimer were below detection limits of the instrument and were significantly higher in heartworm-infected dogs, notably in microfilaremic dogs. The results suggest the possibility of using troponin I and myoglobin as markers for cardiac damage and the D-dimer as a supportive tool for a diagnosis of pulmonary thromboembolism in dogs with cardiopulmonary dirofilariasis.

Prevalence of Dirofilaria immitis Infection in Living Raccoon Dogs Assessed by Hematological Examination

The prevalence of Dirofilaria immitis in free-ranging raccoon dogs (Nyctereutes procyonoides viverrinus) was examined in the southeast region of Kanagawa Prefecture, Japan, using a rapid immunomigration (RIM) test kit. Between April 2007 and March 2010, we examined 108 raccoon dogs rescued and housed by the Kanazawa Zoological Garden. D. immitis infection was found in 8 (7.4%) raccoon dogs. This is the first report to reveal the prevalence of D. immitis infection in living raccoon dogs. The prevalence of the infection was lower than previously reported values obtained on postmortem examination. One reason might be that the present study included young raccoon dogs infected with immature worms. Significant high-risk areas of D. immitis infection in the raccoon dogs were not observed.

Survey of CanineDirofilaria immitisInfection in New Caledonia

Canine dirofilariosis is a frequent parasitic disease in New-Caledonia. A survey of canine heartworm (Dirofilaria immitis) infection among dogs from the cities of Tontouta, Nandaï and Nouméa, was performed in March 2009 using two antigen test kits; the microwell ELISA test: DiroCHE (Synbiotics Europe) and the Rapid Immuno Migration (RIM) test: WITNESS DIROFILARIA (Synbiotics Europe). Blood samples were collected from 64 dogs: 49 strays and 15 military working dogs. The military dogs received a permanent chemoprophylaxis (moxidectin). In 11 stray dogs, both tests were positive (22.4%). All the military dogs were negative, showing efficiency of chemoprophaxis. Results were discrepant in 6 dogs, negative with one test and doubtful with the other. Antigen heartworm test kits are available and reliable diagnostic tools. They are useful to evaluate the efficiency of chemoprophylaxis and to detect infected animals in order to treat them and to prevent the spreading of the disease.

A study on Dirofilaria immitis in healthy urban dogs from Ahvaz, Iran

Summary Heartworm infection is one of the most important p arasitic diseases in dogs and an increasing number of cases are reported each year by necropsy in Ahvaz. This study was conducted to determine the prevalenc e of Dirofilaria immitis infection and to investigate the risk factors rela ted to heartworm disease in urban dogs in this area. Blood samples were collected from 100 dogs from Feb 2007 to Feb 2008. All samples were examined by modified Knott test, direct smear and a ntigen detection (Immunochromatographic antigen rapid canine D. immitis Ag Test Kit) technique to detect circulating micro filaria and adult antigen of D. immitis , respectively. Of the total 100 dogs, 1% were positi ve by direct smear, 5% were positive by modified Knott test and 6% were positive by antigen detection. In addition, 1% of positive dogs were determined to ha ve occult D. immitis infections. Dirofilaria immitis was the only canine filarial parasite present in t his study. From these three methods, modified Knott test, due to microfilarial identification on concentrated blo od had the highest validity. The difference between outdoo r and indoor dogs was found significant (P = 0.033) , whereas no statistically significant differences we re observed between different age groups, sexes and breeds (P>0.05). The highest heartworm prevalence by modified Knott test was observed in older than 6-year-ol d dogs (8.3%) followed by 3‐6 years (2.7%) and the 6-month to 3 years (3.5%) age groups. The infection w as more prevalent in males and short haired breeds. Ou r results suggest that heartworm treatment and prev entive care should be considered in urban dogs of Ahvaz, I ran.

Preliminary findings on the efficacy of selamectin in the treatment of dogs naturally infected with Dirofilaria repens

Subcutaneous dirofilariosis caused by Dirofilaria repens is common in dogs and it is an emerging helminthozoonosis in Europe, Asia, Africa and also in Hungary. Macrocyclic lactones are used for preventing the infection; however, their activity against the microfilariae and mature stages of this species is questionable. Selamectin is widely used for the prophylaxis of heartworm (D. immitis) infection. The objective of the present study was to test the microfilaricidal efficacy of the topical formulation of selamectin in dogs naturally infected with D. repens . A total of 78 Beagle dogs were examined for the presence of circulating microfilariae by Knott's test. Twenty-three of the microfilaraemic dogs were divided into four groups and included in the trial. The dogs received monthly or biweekly selamectin treatment and were subjected to monthly blood testing for a period of 252 or 336 days. At the end of the study, 65% of the dogs were not microfilaraemic and the rest had low number of microfilariae in their blood. These results indicate that chronic spot-on selamectin treatment may be a useful tool also in the control of canine subcutaneous dirofilariosis.

PCR detection of Dirofilaria immitis in Aedes aegypti and Culex pipiens from urban temperate Argentina

Dirofilariasis, a mosquito-borne disease of dogs caused by the nematode Dirofilaria immitis (Leidy; Spirurida: Onchocercidae), has now become a growing zoonotic concern. Based on direct microscopical observation, Aedes aegypti (L.) and Culex pipiens L. (Diptera: Culicidae) have been previously incriminated as potential vectors of D. immitis in urban temperate Argentina. In this study, an effort was made to provide evidence for this assumption by screening of mosquitoes for D. immitis infection using a polymerase chain reaction (PCR) assay. PCR primers were developed to specifically amplify the D. immitis-16S rRNA gene and to reliably detect 100th of the genomic equivalent (10 pg) of the infective third-stage larvae in mosquito pools of up to 30 individuals. Collection of mosquitoes was performed between September 2007 and April 2008 in premises known to be inhabited by D. immitis-infected dogs in Greater Buenos Aires. The final collection comprised 453 specimens belonging to 11 mosquito species of the genera Aedes, Culex, Ochlerotatus, and Psorophora. PCR assays were performed on 82 pools (n ≤ 20) of heads and abdomens separately, as this allows differentiating infective and non-infective stages of the parasite, respectively. Identification of the non-infective stage of D. immitis in A. aegypti and C. pipiens provided additional strong support of transmission of the parasite by these species. To our knowledge, this was the first PCR screening for D. immitis-infected mosquitoes in South America.

Spontaneous Pneumothorax in a Dog Secondary toDirofilaria ImmitisInfection

A 5-year-old female spayed Labrador Retriever dog was referred to the Louisiana State University Veterinary Teaching Hospital for treatment of pneumothorax. Thoracic radiographs and computed tomography showed spontaneous pneumothorax, thoracic lymphadenopathy, pulmonary hypertension, and multifocal pulmonary bulla lesions. At surgery, numerous adult nematodes protruded from the parenchyma of the left caudal and accessory lung lobes and pulmonary arteries. On histopathology, multiple adult filarid nematodes were observed within the pulmonary blood vessels. Broad foci of necrosis of the pulmonary parenchyma were present. The tunica intima of the pulmonary arteries was markedly thickened by intimal fibrosis and medial hypertrophy. The final diagnosis was severe Dirofilaria immitis infection that resulted in pulmonary vascular lesions and focally extensive infarcts of the pulmonary parenchyma with bulla formation and rupture causing spontaneous pneumothorax. The dog received antibiotic and steroid therapy, as well as adulticide treatment, and recovered.

Seroprevalence of Toxoplasma gondii and Concurrent Bartonella spp., Feline Immunodeficiency Virus, Feline Leukemia Virus, and Dirofilaria immitis Infections in Egyptian Cats

Toxoplasma gondii and Bartonella spp. are zoonotic pathogens of cats. Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLv) are related to human immunodeficiency virus and human leukemia virus, respectively, and these viruses are immunosuppressive. In the present study, the prevalence of antibodies to T. gondii , Bartonella spp., FIV, as well as FeLv and Dirofilaria immitis antigens was determined in sera from feral cats (Felis catus) from Cairo, Egypt. Using a modified agglutination test, antibodies to T. gondii were found in 172 (95.5%) of the 180 cats with titers of 1∶5 in 9, 1∶10 in 9, 1∶20 in 3, 1∶40 in 5, 1∶80 in 5, 1∶160 in 15, 1∶320 in 22, and 1∶640 or higher in 104. Thus, 57.4% had high T. gondii titers. Antibodies to Bartonella spp. were found in 105 (59.6%) of 178, with titers of 1∶64 in 45, 1∶128 in 39, 1∶256 in 13, 1∶512 in 3, 1∶1,024 in 4, and 1∶2,048 in 1 cat. Antibodies to FIV were detected in 59 (33.9%) of 174 cats. Of 174 cats tested, antigens to FeLv, and D. immitis were detected in 8 (4.6%) and 6 (3.4%) cats, respectively. The results indicate a high prevalence of T. gondii, Bartonella spp., and FIV infections in cats from Cairo, Egypt. This is the first report of Bartonella spp., and D. immitis infection in cats in Egypt.

Autochthonous Dirofilaria immitis infection in a ferret with aberrant larval migration in Europe

A two-year-old male ferret (Mustela putorius furo) was presented to the Faculty of Veterinary Science, Szent István University, for investigation of somnolence. Following unsuccessful therapeutic attempts, the ferret was euthanased and a male Dirofilaria immitis worm was found in the pulmonary artery and a female D. immitis specimen in the subdural space of the cranial cavity. To the authors' knowledge, this is the first European record of D. immitis infection in a ferret, and the first case in which aberrant larval migration and consequent central nervous system signs were observed in a ferret in the course of D. immitis infection.

Prevalence ofDirofilaria immitisInfection in Dogs from Celestun, Mexico, Using Polymerase Chain Reaction Test

The aim of this study was to determine the prevalence of Dirofilaria immitis in dogs and to analyze risk factors associated with infection at Celestun, a coastal locality in southeast Mexico. Blood samples were collected from 279 asymptomatic individuals between August 2007 and March 2008 and analyzed by polymerase chain reaction technique. The association between D. immitis infection and sex, age group, and distance of residence from a wetland of dogs was statistically analyzed. Prevalence of D. immitis infection was of 59.8%. Age of individuals (>2 years) was a risk factor for infection with D. immitis (odds ratio 2.49, confidence interval 1.47-4.23, p=0.001). In conclusion, Celestun can be considered a focus of D. immitis infection with high levels of transmission among the local dog population, as confirmed by the high prevalence reported and the association of age (dogs >2 years) as a risk associated with infection.

Seroprevalence of canine heartworm (Dirofilaria immitis) infection in Albania

Blood samples from 260 dogs over 1 year of age from eight districts of the western part of Albania (20 to 50 dogs per district) were collected in 1995 and 1996 and tested for circulating Dirofilaria immitis antigen using the PetChek HTWM PF (IDEXX) ELISA test kit. Overall seroprevalence of D. immitis infection among these dogs was 13.5% (95% confidence interval = 9.3-17.6%), ranging from 5% to 30% between the districts of origin of the dogs. There was no difference for the seroprevalence of heartworm infection between the sexes and age classes or between pure and mixed breed dogs; however, D. immitis seroprevalence was significantly (p < 0.0001) higher in dogs presenting cardiopulmonary signs (83.3%) compared to clinically inconspicuous dogs (10.1%).

Heartworm (Dirofilaria immitis) infection in a leopard (Panthera pardus pardus) housed in a zoological park in north-eastern Italy

Canine heartworm (cHW) disease is now recognised as potential cause of serious disease in cats and other felids, especially in endemic areas. In March 2009, a 23-years-old male African leopard (Panthera pardus pardus) housed in a zoological park located in the Province of Padova (Veneto Region), a cHW endemic area of the north-eastern Italy, died and was immediately necropsied. A cloth completely occluding the pyloric lumen was considered the presumptive cause of death. During necropsy, six nematodes (4 males and 2 females) were found within the right ventricle of the heart and the pulmonary artery. Diagnosis of HW (Dirofilaria immitis) infection was carried out by morphological features of adult worms and microfilariae, and then confirmed by detection of circulating HW antigens using a commercial SNAP kit (IDEXX Laboratories inc., USA). D. immitis infection was also confirmed by PCR amplification of the 5S ribosomal spacer region, performed on worm fragments and microfilaraemic blood samples obtained from the right ventricle of the heart. A glomerulonephritis of immuno-mediated origin and most likely associated with the HW infection is also reported. HW chemoprophylaxis and annual serological testing on wild felids housed outdoors in endemic cHW disease areas are recommended. This is the first diagnosis of D. immitis infection in an exotic felid in Italy.

Prevalence of Dirofilaria immitis, Ehrlichia canis, and Borrelia burgdorferi in pet dogs, racing greyhounds, and shelter dogs in Florida

Arthropod vectors of canine infectious diseases are present throughout Florida. Since crowded housing has the potential to bring vectors and infected dogs into close proximity, it is possible that prevalence of infection is higher in intensely housed dogs. In this study, the seroprevalence of Dirofilaria immitis, Ehrlichia canis, and Borrelia burgdorferi in dogs residing in two types of intensive housing, greyhound kennels and animal shelters, was compared to dogs residing in low-intensity housing, private homes. Serum was collected from a cross-section of 1500 adult dogs from Florida, including 500 pet dogs referred to the Veterinary Medical Center of the College of Veterinary Medicine at the University of Florida, 500 racing greyhounds, and 500 dogs residing in animal shelters. Serum was tested for D. immitis antigen, E. canis antibodies, and B. burgdorferi antibodies by ELISA. Seroprevalence of D. immitis was significantly higher (14.6%) in shelter dogs and in pet dogs (1.4%) than in racing greyhounds (0.2%) ( P < 0.04). There were no significant differences in the seroprevalence of E. canis (0.4–1.6%) or B. burgdorferi (0–0.8%) among the groups. There was no association of sex or age with D. immitis infection, but pit bull type dogs were more than twice as likely to be infected than other breeds ( P = 0.003). Evidence for vector-borne infections, particularly D. immitis, was found in dogs throughout the state. The prevalence was greatest for D. immitis infection in shelter dogs, likely due to lack of preventive medications prior to impoundment. Although heartworm infection is considered to be a treatable condition, insufficient resources in shelters may lead to euthanasia of infected dogs that would otherwise be considered adoptable.

A serological study ofDirofilaria immitisin feral cats in Grenada, West Indies

A study to determine the seroprevalence of Dirofilaria immitis was carried out in feral cats in Grenada. Of the 137 feral cats tested for circulating antibodies (IgG; lateral-flow immunoassay) and circulating antigens (Ag; enzyme-linked immunosorbent assay), 8% (95% confidence interval (CI) 3.5-12.5%) were antibody positive and 5.1% (95% CI 1.4-8.8%) were antigen positive. No significant difference between cats aged>1 to 4 years and cats less than 1 year of age was found (P>0.05, χ²). There was also no significant difference (P>0.05, χ²) between male and female cats. Dirofilaria immitis prevalence is relatively high in the feral cat population of Grenada. Evidence of D. immitis infection in feral cats coupled with the endemic nature of heartworm disease in dogs in Grenada leads us to suggest the introduction of heartworm prophylaxis in cats. To the authors' knowledge, this serological evidence of heartworm infection in feral cats in Grenada is the first report from the Caribbean region.

Association of Wolbachia with heartworm disease in cats and dogs

Although the presence of adult Dirofilaria immitis in the pulmonary arteries and its associated arteritis and thromboembolic disease can explain some of the manifestations of canine and feline heartworm disease, the cause of other findings remains unclear. Cats with D. immitis antibodies but lacking adult parasites in the pulmonary arteries frequently develop histological lesions of the airways, resulting in a condition termed Heartworm-Associated Respiratory Disease. All D. immitis parasites harbor Wolbachia pipientis bacteria and D. immitis-infected animals can have circulating Wolbachia antibodies and pro-inflammatory Wolbachia antigens (WSP) deposited in tissues. Little is known about the role that Wolbachia plays in lung disease of animals naturally infected with D. immitis. The purpose of this study was to determine the contribution of Wolbachia to the pathogenesis of natural heartworm disease in cats and dogs. We hypothesized that animals having sufficient Wolbachia burden to be detected in lung tissue by immunohistochemistry and/or polymerase chain reaction (PCR) would have more severe pulmonary disease than those with bacteria below the limits of detection. We further hypothesized that animals that were immunoreactive to pro-inflammatory WSP would have more severe pulmonary lesions than those that were seronegative for WSP antibodies. Blood and lung tissue samples were collected from cats and dogs representing three different D. immitis infection statuses: heartworm-free, heartworm-exposed, heartworm-infected. There was a positive but weak correlation between the magnitude of D. immitis antibody titers and WSP titers in cats ( r = 0.57, p < 0.001) and in dogs ( r = 0.39, p < 0.001). Pulmonary lesions were more common in HW-infected animals than in HW-free animals. Pulmonary arteriolar occlusion was more common in HW-infected cats (57%; p = 0.003) than in HW-infected dogs (17%). Although pulmonary lesions were most common in HW-infected animals, there was no clear additive effect when either Wolbachia DNA/WSP was detected in lung tissue or when circulating Wolbachia antibodies were detected. There were no significant differences in the magnitude of pulmonary lesion scores within each HW-infection status group regardless of whether Wolbachia DNA/WSP or antibodies were detected. The relationship between Wolbachia and lung pathology in heartworm-infected animals remains to be determined. The lack of clear evidence for a role of Wolbachia in heartworm disease creates a dilemma for veterinarians treating animals in D. immitis-endemic areas. Although the indiscriminant use of antibiotics should be avoided, many clinicians prescribe doxycycline based on the favorable responses observed in human filarial diseases and promising results from the first published studies of doxycycline use in D. immitis-infected dogs.

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

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

Coccidioidomycosis in a Lung Transplant Recipient Acquired From the Donor Graft in France

Coccidioidomycosis in a Lung Transplant Recipient Acquired From the Donor Graft in France

Serological update and molecular characterization of Dirofilaria immitis in dogs, South Korea

Eighty-one dogs in the Chungnam province were tested for heartworm (Dirofilaria immitis) infection by ELISA (SNAP test, IDEXX Laboratories, Maine, USA). Seventeen (20.9%) of the 81 samples were found to be positive and further analyzed by 16S rRNA sequencing. In this study, all dogs tested lived outdoors. Using the chi(2) test and Fisher's exact test, no significant differences in the prevalence of dirofilariasis were observed among different gender and age groups, although the prevalence of this disease among dogs 2-4yrs of age remains highest. Sequence analysis revealed that the species prevalent in Chungnam province were genetically distinct from the type strain of D. immitis based on the nucleotide deletion found at position nt 276 (cytosine) and nucleotide substitution at position 428 (G to A) of the partial 16S rRNA sequence of the type strain. Furthermore, phylogenetic analysis suggests at least 2 groups of D. immitis circulating in the Chungnam area between the year 2007 and 2008.

Dirofilaria immitis infection in stray dogs of Khuzestan, a province in South-Western Iran

Dirofilariaimmitis, which is otherwise known as heartworm, is an important parasite in dogs and other carnivores. It lives in the right ventricle of the heart, the pulmonary artery and the posterior vena cava, and its microfilaria can be found in the peripheral circulation. This is the first report of Dirofilariaimmitis infection in stray dogs in Khuzestan, a province in South-Western Iran. Blood samples from 119 stray dogs were collected randomly from different districts of Khuzestan. The samples were examined by the modified Knott's method. Blood microfilaria of Dirofilariaimmitis were observed in 15 samples (12.61%). The most severe infections were seen in 7-yr-old male dogs and also those in the Dezfool district. However, statistical analysis by the Chi-square method did not show a significant relationship between the rate of infection and other factors, which included age, sex and geographical distribution. As this parasite can infect humans, the infection of dogs with D. immitis in Khuzestan should be controlled by the removal of the dogs and the vectors of D. immitis are insects including flies.