Immitis Infection Research Articles

Experimental Infection of Dirofilaria immitis in Raccoon Dogs

Canine heartworm (Dirofilaria immitis) is a nematode that naturally parasitizes in the pulmonary arteries and the right ventricle of domestic dogs (Canis familiaris) as final hosts. Japanese raccoon dogs (Nyctereutes procyonoides viverrinus) also are known to be susceptible to infection by the parasite. However, prevalence of this infection among free-ranging raccoon dogs is low and so is the worm burden. To examine the susceptibility of the raccoon dog to D. immitis infection, 3 raccoon dogs and 2 beagles were inoculated 4 times with 25 third-stage larvae (L3s) of D. immitis at 3-wk intervals. Worms were recovered from 2 raccoon dogs and both domestic dogs. The average percentage of recovery (2.3%) of the raccoon dogs was almost 10 times lower (24.5%) than that of the domestic dogs, but there was no significant difference in the body length of worms recovered from 2 types of hosts. To examine microfilaremia, 2 raccoon dogs were infected with 100 L3s. Microfilaremia was observed for 180 days postinoculation (PI) but disappeared at about 300 days PI. The raccoon dog was mildly susceptible to infection with D. immitis, but surviving worms developed and matured normally.

Dogs with patent Dirofilaria immitis infection have higher expression of circulating IL-4, IL-10 and iNOS mRNA than those with occult infection

Dirofilaria immitis is the agent of canine heartworm disease, in which adult worms reside in the pulmonary arteries, producing first stage larvae (microfilariae) that are released into the bloodstream. The present work describes the cytokine and iNOS mRNA expression in the peripheral blood of naturally infected dogs classified as either microfilariemic or amicrofilariemic. Results show that microfilariemic dogs had higher expression of IL-4 and iNOS mRNA than amicrofilariemic dogs. Furthermore, IL-10 mRNA expression was strongly expressed in dogs with circulating microfilariae, compared to only negligible expression in amicrofilariemic dogs. Finally, mf+ status was associated with a predominance in IgG1 production against worm antigens. These results would suggest that circulating mf may stimulate, like in other filarial infections, an immune bias towards unresponsiveness in D. immitis-infected dogs, consenting long-term adult worm survival.

Prevalence and epidemiological aspects of Dirofilaria immitis in dogs from Kayseri Province, Turkey

This study was conducted to determine the prevalence of Dirofilaria immitis infection and to investigate the risk factors related to heartworm disease in dogs from Kayseri, Turkey. Blood samples were collected from 280 dogs from May 2005 to March 2006 and were examined by membrane filtration-acid phosphatase histochemical staining and antigen Elisa techniques to detect circulating microfilariae and antigens of D. immitis, respectively. Of the total of 280 dogs, 27 were positive for D. immitis with a prevalence value of 9.6%. In addition 29.6% of positive dogs determined to have occult D. immitis infections. D. immitis was the only canine filarial parasite present in the study area. The mean number of microfilariae in infected dogs was 4730 ± 5479 per ml of blood. The highest heartworm prevalence were observed in 7–10 age group (28.6%) followed by 4–6 (17.1%) and 0.5–3 (4.8%) age groups. The differences between 0.5–3 and other age groups were found significant, whereas no statistically significant difference was observed between 4–6 and 7–10 age groups. The infection was more prevalent in males, larger breeds and the dogs not on prophylaxis. No statistically significant difference was observed between stray and owned dogs. Our results suggest that heartworm treatment and prophylaxis should be considered in Kayseri Province.

Focos de dirofilariose canina na Ilha do Marajó: um fator de risco para a saúde humana

The occurrence of human pulmonary dirofilariasis maintains a relation with the prevalence of Dirofilaria immitis infection in the canine population. Several mosquito species are vectors of this nematode. Canine blood samples collected in Pingo d'Agua and União villages, Salvaterra municipality (Marajó Island, Pará), in June, 2004 (n = 34) and April, 2005 (N = 90) were analyzed. Parasitological and immunological (ELISA--kit SNAP(R) 3DX Biobrasil) diagnoses were compared following the examination of 34 samples. The prevalence in the population (N = 90) was evaluated by means of ELISA. ELISA revealed more positive samples (25/34; 73.5%) than thick smears (23/34, 67.6%) or Knott (21/34, 61.8%), but the differences were not significant (p > 0.05). The frequency of D. immitis infection was 58% in dogs ranging from 0-2 years old, whereas in older dogs it was 100%. The prevalence of canine dirofilariasis was high in Pingo d'Agua and Vila União (53.5%), indicating the risk of parasite transmission to the people in this area.

Endogenous Lipid Pneumonia in a Dog

Endogenous lipid pneumonia has previously been diagnosed in dogs only once. This report describes a case in a dog with a persistent cough, in which the histological diagnosis was based on the presence of numerous foamy macrophages that filled the alveoli and contained small sudanophilic vacuoles. The appearance of endogenous lipid pneumonia in this animal was accompanied by Dirofilaria immitis infection and chronic bronchitis.

Midfoot Coccidioidal Osteomyelitis: A Case Report and Review of the Literature

Coccidioides immitis is endemic in arid parts of the southwestern United States and regions of Central and South America. Symptomatic infection (comprising 40% of cases) initially presents as a flu-like illness with fever, cough, headache, rash, and myalgias. Some patients (especially those who are immunocompromised) fail to recover, with the development of chronic pulmonary infection or widespread disseminated infection1. A Coccidioides immitis infection that is disseminated to bone is very difficult to treat and usually requires lifetime suppressive antifungal therapy1-3. The present report describes a patient with recurrent osseous coccidioidal osteomyelitis at a new locus who presented after minor trauma to the middle part of the foot. The patient was managed successfully with surgical debridement and antifungal medication. The pathophysiology of osseous infection and treatment options are discussed. The patient was informed that data concerning this case would be submitted for publication. Six years prior to presentation, a thirty-nine-year-old man was diagnosed with disseminated coccidioidomycosis involving the thoracic vertebrae, skin, and lungs. The diagnosis was made on the basis of a biopsy of lung tissue. At the time of diagnosis, the Coccidioides complement fixation titer was 1:2048. The patient was managed with amphotericin B (total dose, 1.5 g) and high-dose fluconazole. Approximately eighteen months before admission, fluconazole was discontinued when the Coccidioides titers returned to normal (<1:2). Six months prior to presentation, the patient sustained a minor nonpenetrating injury that resulted in pain and tenderness in the lateral aspect of the right foot, with a recurrent nonhealing wound. The injury initially was thought to have resolved without treatment, but two months later another lesion recurred in the same region. Over the subsequent four months, the patient was seen at multiple clinics and was managed with several courses of antimicrobial medication, without healing of the …

Temporal expression of inflammatory mediators in brain basilar artery vasculitis and cerebrospinal fluid of rabbits with coccidioidal meningitis.

Strokes due to transmural vasculitis associated with coccidioidal meningitis result in significant morbidity and mortality. The immunological and inflammatory processes responsible are poorly understood. To determine the inflammatory mediators, i.e. cytokines, chemokines, iNOS, matrix metalloproteinase-9 (MMP-9), that possibly contribute to vasculitis, temporal mRNA expression in brain basilar artery samples and MMP-9 protein in the CSF of male NZW rabbits infected intracisternally with 6.5 x 10(4) arthroconidia of Coccidioides immitis were assessed. Five infected and 3 sham-injected rabbits at each time point were euthanized 4, 9, 14 and 20 days post infection. All infected rabbits had neurological abnormalities and severe vasculitis in the basilar arteries on days 9-20. In basilar arteries of infected animals versus controls, mRNAs encoding for IL-6, iNOS, IFN-gamma, IL-2, MCP-1, IL-1beta, IL-10, TNF-alpha, CCR-1, MMP-9, TGF-beta, as well as MMP-9 protein in CSF, were found to be significantly up-regulated. Thus, this study identified inflammatory mediators associated with CNS vasculitis and meningitis due to C. immitis infection. Assessment of the individual contribution of each mediator to vasculitis may offer novel approaches to the treatment of coccidioidal CNS infection. This study also provides unique methodology for immunology studies in a rabbit model.

Posaconazole therapy for systemic coccidioidomycosis in a chimpanzee (Pan troglodytes): a case report

Systemic coccidioidomycosis was diagnosed in a 4-year-old male chimpanzee (Pan troglodytes) with ascites and failure to thrive. Physical examination, laboratory and radiological studies, and exploratory laparotomy showed signs of systemic fungal infection that included penetration into the central nervous system (CNS). Serum and cerebrospinal fluid (CSF) titres, along with ascites cytology findings, confirmed the presence of Coccidioides immitis. However, the organism could not be cultured from the CSF. Treatment with fluconazole 10 mg kg(-1) daily for 6 months was not associated with clinical improvement. Subsequent treatment with posaconazole 50 mg kg(-1) daily for approximately 24 months resulted in negative serum titres and improved clinical status. Illness not directly related to the C. immitis infection caused the chimpanzee's deterioration and eventual killing. Histological examination performed during necropsy provided no evidence of coccidioidomycosis; however, a positive C. immitis serum antibody titre was noted. The successful suppression of coccidioidomycosis observed in this chimpanzee suggests that posaconazole may have a role in the treatment of CNS infections caused by susceptible fungi.

The First Record of Dirofilaria immitis Infection in a Humboldt Penguin, Spheniscus humboldti

Dirofilaria immitis infection is an important parastic disease in many mammals, especially canids, but has not been reported in bird hosts. Filarial worms were isolated from the lumen of the right atrium of the heart and the connective tissue of the lung of a captive female Humboldt penguin, Spheniscus humboldti, that died at a zoo in Japan. One of these worms was observed morphologically and identified as D. immitis by features such as 4 pairs of cephalic papillae, 1 pair of cervical papillae, esophagus divided into 2 regions, 4 pairs of pre-anal papillae, 5 pairs of post-anal papillae, and unequal spicules. In addition, the partial DNA sequence (234 bp) of mitochondrial CO / gene of the filarial worm was identical to that of D. immitis. This is the first report of D. immitis infection in a bird.

Safety of imidacloprid plus moxidectin topical solution applied to cats heavily infected with adult heartworms (Dirofilaria immitis)

A topically applied formulation containing 10% imidacloprid+1% moxidectin (Advocate/Advantage multi) has been developed for monthly application to cats for the prevention of feline heartworm (HW) disease caused by Dirofilaria immitis; and for the treatment and control of flea infestations, ear mite infestations, and intestinal nematode infections. A study model was designed to evaluate the safety of this product in cats harboring adult D. immitis infections. Eighty adult cats (40 males/40 females) were each inoculated with 60 third-stage D. immitis larvae on test day (TD) 1. On TD 243-245 echocardiographic imaging was performed on each cat to confirm and estimate the number of adult D. immitis residing in the cardiovascular system. A total of 35 cats were subsequently eligible for safety evaluation based on inclusion criteria. Four treatment groups were established and randomly selected for treatment: imidacloprid+moxidectin solution at the label dose (n=9) (group 1), imidacloprid+moxidectin solution at 5x the Iabel dose (n=9) (group 2), 6% selamectin topical solution (Revolution) at the label dose (positive control, n=8) (group 3), and topical treatment with placebo (negative control, n=9) (group 4). All cats were treated on TD 250. Treatments for groups 1, 3, and 4 were repeated on TDs 278 and 306. Group 2 cats were euthanized and examined for adult D. immitis on TD 288. All other cats were euthanized and examined for adult D. immitis on TD 334. No adverse events attributable to treatment with the test articles were observed during the study. The geometric mean numbers of adult D. immitis recovered at necropsy from treatment groups 1-4 were 2.9, 3.2., 4.0, and 2.7, respectively. There were no statistically significant differences in the comparison of adult D. immitis recovered at necropsy (ANOVA overall group effect P-value of 0.5356). The results of this study demonstrate that imidacloprid+moxidectin topical solution can be used safely in cats heavily infected with adult D. immitis.

Lmidacloprid plus moxidectin topical solution for the prevention of heartworm disease (Dirofiloria immitis) in dogs

A topically applied formulation containing 10% imidacloprid+2.5% moxidectin (Advocate/Advantage multi) has been developed for monthly application to dogs for the prevention of canine heartworm (HW) disease caused by Dirofilaria immitis; and for the treatment and control of flea infestations, mite infestations, and intestinal nematode infections. The efficacy of this formulation to prevent canine HW disease was confirmed at three study locations which included the use of 88 purpose-bred beagles 6-8 months of age. Two of these studies also evaluated the effects of post-treatment water exposure or shampooing on product performance. Each dog was infected with 50 third-stage D. immitis larvae on test days -30 to -45. Dogs were blocked according to gender and body weight on test day -1. Topically applied test articles were administered once on test day 0 as follows: 10% imidacloprid+2.5% moxidectin (52 dogs); 2.5% moxidectin mono solution (eight dogs); 10% imidacloprid mono solution (16 dogs); and placebo solution (12 dogs). Treatment dosages were applied to provide a minimum of 10 mg/kg imidacloprid and/or 2.5 mg/kg moxidectin. Subgroups of dogs were exposed to water to simulate swimming/rain exposure at designated post-treatment intervals. Additional dogs were shampooed at 90 min, 4 h, or 24 h post-treatment. All dogs were necropsied 110-119 days post-treatment for recovery of adult D. immitis. No adult D. immitis were recovered at necropsy from any of the dogs receiving 10% imidacloprid+2.5% moxidectin or 2.5% moxidectin mono solution, demonstrating 100% efficacy for prevention of D. immitis infection. A total of 701 adult D. immitis were recovered at necropsy from dogs receiving 10% imidacloprid mono solution or placebo (range of 11-40 D. immitis/dog). The efficacy of 10% imidacloprid+2.5% moxidectin treatment for the prevention of HW disease was not decreased when dogs were shampooed as early as 90 min post-treatment, or when dogs immersed in water 5 times post-treatment at weekly intervals.

Coccidioidomycosis in Renal Transplant Recipients

Coccidioidomycosis is endemic in the southwest United States, and impaired cellular immunity profoundly increases the susceptibility to life-threatening Coccidioides immitis infections. This study combines the clinical presentation of coccidioidomycosis in 5 renal transplant recipients in El Paso from 1987 to 2002 with details from 28 other cases published in the literature from 1966 to 2002. The 5 cases in El Paso occurred in a population of 297 transplant recipients. Overall, the 33 renal transplant recipients with coccidioidomycosis included 24 men and 9 women with a median age of 38 years. Fifty-eight percent of the patients were white, 33% Hispanic, 3% African American, 3% Native American, and 3% Asian. Twenty-three (70%) of the patients had cadaveric donors, and the remainder had living donors. Underlying renal diseases included chronic glomerulonephritis (48%), diabetes mellitus (30%), autoimmune diseases (3%), Alport syndrome (3%), and others not documented (16%). C. immitis was isolated from the lung in 75% of the patients; in the remaining 25%, it involved the spleen, urine, skin, pancreas, bone marrow, thyroid, choroid, and lymph nodes. In the majority of the patients, the initial clinical presentation included fever with clinical and radiographic evidence of pneumonia. The median time between transplantation and the diagnosis of infection was 6 months (15 days to 50 months). Disseminated coccidioidomycosis occurred in 18 patients. Treatment modalities included amphotericin B in 29 patients (88%) and fluconazole in 6 patients (18%). Death occurred in 55% (18) of the patients with 9 of them dying from coccidioidomycosis and the other 9 dying of other causes. There did not appear to be a significant increase in the mortality in patients who had underlying diabetes mellitus.

Subtotal pericardectomy and epicardial excision for treatment of coccidioidomycosis-induced effusive-constrictive pericarditis in dogs: 17 cases (1999–2003)

To determine the history, clinicopathologic findings, and results of surgery for effusive-constrictive pericarditis associated with Coccidioides immitis infection in dogs. Retrospective study. 17 client-owned dogs that underwent a subtotal pericardectomy and epicardial excision. Hospital records from May 1999 to June 2003 were reviewed. Data collected included history, clinicopathologic findings, treatments, and outcome. Follow-up information was obtained via recheck examination and by use of standardized telephone interviews with referring veterinarians and owners. All dogs were of large breeds, and most were male (mean age, 4.66 years). Ten dogs had no prior history of C. immitis infection, and 7 dogs had chronic infection with C. immitis. Having a chronic C. immitis infection reduced the odds of survival, compared with no previous infection. All dogs had clinical signs of right-sided heart failure. All dogs had serum titers (range, 1:8 to 1:256) for antibodies against C. immitis prior to surgery, and titers were not significantly associated with outcome. Predominant echocardiographic findings were thickened pericardium, reduced right ventricular filling, and pleural or pericardial effusion. All dogs underwent a subtotal pericardectomy and epicardial excision and had fibrosing pyogranulomatous pericarditis in biopsy specimens obtained during surgery. The perioperative mortality rate was 23.5%, and the 2-year postdischarge survival rate was 82%. Surgical treatment via subtotal pericardectomy and epicardial excision is successful at relieving right-sided heart failure in dogs with effusive-constrictive pericarditis secondary to C. immitis infection, but long-term treatment with antifungal agents may still be required.

Dirofilaria immitis prevalence in a canine population in the Samana Peninsula (Dominican Republic) – June 2001

Dirofilaria immitis, the etiological agent for heartworm disease, is a zoonotic, vector-borne parasite. The dog is the most common natural host. Heartworm disease is present in all US states, as well as in South and Central America, Asia, Europe, Africa and Australia [ Ryan, W.G., Newcomb, K.M., 1995. Prevalence of feline heartworm disease – a global review. In: Proceedings of the Heartworm Symposium’95, Auburn, Alabama, USA, 31 March–2 April, 1995. American Heartworm Society, Batavia, USA, pp. 79–86]. According to Menda [Menda, J.A., 1989. Transplacental migration of Dirofilaria immitus microfilariae. Companion Anim. Pract. 19 (6–7), 18–20], 18% of the canine population in the city of Santo Domingo tested positive for heartworm using the Filar Assay Kit. In the year 2000, clinical veterinarians from the Samana Peninsula in the Dominican Republic stated that the incidence of heartworm was minimal (Goodman, personal communication). In this small epidemiological study performed during the summer of 2001, 104 dogs from the Samana Peninsula were tested for heartworm antigen with the WITNESS HW Test™ and a wet mount evaluation for microfilaria under light microscopy. It was found that 18.2% of the canine population tested positive according to either one or both of the diagnostic methods. It would be advisable to apply prevention measures to control Dirofilaria immitis infection in the canine population of the Samana Peninsula in the Dominican Republic.

Prevalence of naturally occurring Dirofilaria immitis infection among nondomestic cats housed in an area in which heartworms are endemic

To determine prevalences of heartworm exposure (ie, positive heartworm antibody test results) and heartworm infection (ie, positive heartworm antigen test results or identification of mature heartworms at necropsy) among nondomestic cats housed in an area in rural North Carolina where Dirofilaria immitis is known to be endemic and among nondomestic cats housed in areas with a low prevalence of dirofilariasis or in an area considered to be free from heartworms. Cross-sectional prevalence survey. 97 nondomestic cats in North Carolina (study population) and 29 nondomestic cats in Colorado; Queensland, Australia; or Auckland, New Zealand (control population). Results of serologic tests and postmortem examinations were reviewed. Results of heartworm antibody tests were positive for 57 of 75 (76%) study cats and 1 of 29 (3%) control cats. Male study cats had a significantly higher risk of heartworm exposure than did female study cats (relative risk, 1.3). Results of heartworm antigen tests were negative for all 47 study cats and 16 control cats that were tested. Postmortem examinations were performed on 21 study cats, and 1 (5%) was found to be infected with heartworms. Results suggested that nondomestic cats housed outdoors in the southeastern United States are at risk for heartworm exposure and infection, with male cats having a greater risk of exposure than female cats.

Immunoblot analysis of specific antigen bands predictable for Dirofilaria immitis infection in cats

Serial sera from four mongrel cats experimentally inoculated with infectious larvae of Dirofilaria immitis were analyzed by immunoblot patterns against a phosphate buffered saline-extract of D. immitis. Antigen-specific protein bands detected indicate that the low molecular weight bands of 36, 32, 22, 19 and 14 kDa, are predictable for positive adult worm infection, suggesting diagnostic usefulness for adult D. immitis infection in cats.

Immunoblotting analysis of somatic components ofDirofilaria immitis

SDS-PAGE analysis of Dirofilaria immitis extracts demonstrated the complexity of somatic protein component of adult male similar to that of adult female worm. Western blot analysis showed six major peptide bands of 85, 66, 42, 20, 16.2 and 14.5 kDa recognized in the sera of infected dogs. Western blotting sera from dogs with Dirofilaria immitis infection suggest that antigenic components in the low molecular weight region may be related to the anti-parasitic mechanism of the host.

Heartworm disease in dogs: Unusual clinical cases

Two unusual cases of heartworm infection are described, including one of spontaneous rupture of cardiac chambers, most likely due to the progressive increase in pressure within the right ventricle caused by Dirofilaria immitis infection. Another case report describes persistent left cranial vena cava, which interfered with the surgical removal of heartworm via the left jugular vein.

Immune response to and tissue localization of the Wolbachia surface protein (WSP) in dogs with natural heartworm ( Dirofilaria immitis) infection

Human and animal parasitic filarial nematodes, including the agent of canine and feline heartworm disease Dirofilaria immitis, harbour intracellular bacteria of the genus Wolbachia (Rickettsiaies). It is thought that these bacteria play an important role in the pathogenesis and immune response to filarial infection. Immunoglobulin G (total IgG, IgG1, IgG2) production against and immunohistochemical staining of tissues for the Wolbachia surface protein (WSP) from dogs with natural heartworm infection were evaluated. All infected dogs had significant total anti-WSP IgG levels compared to healthy controls. Interestingly, WSP was recognized by the IgG2 subclass in both microfilariemic dogs and in dogs with no circulating microfilariae (occult infection). However, microfilariemic dogs also produced gG1 antibodies. Positive staining for WSP was observed in lungs, liver and kidneys, in particular in glomerular capillaries of naturally infected dogs who had died from heartworm disease. Our results show for the first time that Wolbachia is recognized specifically by D. immitis—infected dogs and that the bacteria is released into host tissue. Furthermore, microfilariemic status appears to effect immune responses to this endosymbiont.

What is happening outside North America regarding human dirofilariasis?

The etiologic agents of human dirofilariasis in the Old World are Dirofilaria immitis, which cause pulmonary and subcutaneous nodules, and Dirofilaria repens, which cause ocular lesions. Although reports of new cases of dirofilariasis are sporadic in other parts of the world, a considerable amount of information is generated in Europe regarding human dirofilariasis. Most cases have been detected in the Mediterranean countries, Ukraine, and Russia; however, isolated or short series of cases have been reported in the Balkan Republics and central and northern European countries. Seroepidemiologic studies have provided evidence that humans living in endemic areas present rates of infection similar to those of the autochthonous canine populations. Antibodies against endosymbiont Wolbachia bacteria have been demonstrated recently in human Dirofilaria infections. During D. immitis infections, preadult worms and third- and fourth-stage larvae are often destroyed by the host reaction, releasing a considerable amount of Wolbachia, and a Th1-type response against Wolbachia and/or filarial antigens is mounted. On the contrary, infections with D. repens, in which worms frequently remain intact, no Th1-type response has been observed. As humans are resistant hosts, the Th1-response could have a role in the resistance against parasites. The causes for the rise in the incidence of human dirofilariasis as well as the possible application of Wolbachia antigens in the serodiagnosis of human infections are discussed.