Seroprevalence ofDirofilaria immitis, feline leukemia virus, and feline immunodeficiency virus infection among dogs and cats exported from the 2005 Gulf Coast hurricane disaster area

Association between vector-borne pathogen seroprevalence in shelter-housed and owned dog populations in the contiguous United States of America

Domestic dogs are susceptible to numerous vector-borne pathogens that are of significant importance for their health. In addition to being of veterinary importance, many of these pathogens are zoonotic and thus may pose a risk to human health. In the USA, owned dogs are commonly screened for exposure to or infection with several canine vector-borne pathogens. Although the screening data are widely available to show areas where infections are being diagnosed, testing of owned dogs is expected to underestimate the actual prevalence in dogs that have no access to veterinary care. The goal of this study was to measure the association between the widely available data from a perceived low-risk population with temporally and spatially collected data from shelter-housed dog populations. These data were then used to extrapolate the prevalence in dogs that generally lack veterinary care. The focus pathogens included Dirofilaria immitis, Ehrlichia spp., Anaplasma spp., and Borrelia burgdorferi. There was a linear association between the prevalence of selected vector-borne pathogens in shelter-housed and owned dog populations and, generally, the data suggested that prevalence of heartworm (D. immitis) infection and seroprevalence of Ehrlichia spp. and B. burgdorferi are higher in shelter-housed dogs, regardless of their location, compared with the owned population. The seroprevalence of Anaplasma spp. was predicted to be higher in areas that have very low to low seroprevalence, but unexpectedly, in areas of higher seroprevalence within the owned population, the seroprevalence was expected to be lower in the shelter-housed dog population. If shelters and veterinarians make decisions to not screen dogs based on the known seroprevalence of the owned group, they are likely underestimating the risk of exposure. This is especially true for heartworm. With this new estimate of the seroprevalence in shelter-housed dogs throughout the USA, shelters and veterinarians can make evidence-based informed decisions on whether testing and screening for these pathogens is appropriate for their local dog population. This work represents an important step in understanding the relationships in the seroprevalences of vector-borne pathogens between shelter-housed and owned dogs, and provides valuable data on the risk of vector-borne diseases in dogs.

Progressive and regressive infection with feline leukemia virus (FeLV) in cats in southern Brazil: Prevalence, risk factors associated, clinical and hematologic alterations

Enzyme-linked immunosorbent assay (ELISA) for viral antigen is commonly used for the diagnosis of progressive feline leukemia virus (FeLV) infection but is not able to determine the true prevalence of infection when used as the sole test. Additional testing to detect proviral DNA will identify regressive (antigen negative) FeLV infections as well as progressive infections. Therefore, this study aimed to determine the prevalence of progressive and regressive FeLV infection, outcome-associated factors, and hematologic changes. A cross-sectional study was performed on 384 cats selected from routine hospital care. Blood samples were subjected to complete blood count, ELISA for FeLV antigen and FIV antibody, and nested PCR amplifying the U3- LTR region and gag gene, which are conserved in most exogenous FeLV. The prevalence of FeLV infection was 45.6% (CI_95% 40.6-50.6%). The prevalence of progressive infection (FeLV⁺P) was 34.4% (CI_95% 29.6-39.1%), that of regressive infection (FeLV+R) was 10.4% (CI_95% 7.4-13.4%), for discordant but positive results 0.8% (CI_95% 0.75-0.84%), for FeLV⁺P coinfected with FIV 2.6% (CI_95% 1.2-4.0%), and FeLV⁺R coinfected with FIV 1.5% (CI_95% 0.3-2.7%). Male cats were three times more likely to be in the FeLV⁺P group. Cats coinfected with FIV were 4.8 times more likely to belong to the FeLV⁺R group. In the FeLV⁺P group, the main clinical changes were lymphoma (38.5%), anemia (24.4%), leukemia (17.9%), concomitant infections (15.4%), and feline chronic gingivostomatitis - FCGS (3.8%). In the FeLV⁺R group, the main clinical signs were anemia (45.4%), leukemia (18.2%), concomitant infections (18.2%), lymphoma (9.1%), and FCGS (9.1%). Cats in the FeLV⁺P and FeLV⁺R groups showed mainly thrombocytopenia (56.6% and 38.2%), non-regenerative anemia (32.8% and 23.5%), and lymphopenia (33.6% and 20.6%). Hemoglobin concentration, packed cell volume (PCV), platelet count, lymphocytes, and eosinophils in the FeLV⁺P and FeLV⁺R groups had lower medians than the control group (FeLV/FIV-uninfected, healthy). Erythrocyte and eosinophil counts were statistically different among the three groups, with the medians of the FeLV⁺P and FeLV⁺R groups being lower than those of the control group. In addition, the median PCV and band neutrophil counts were higher in FeLV⁺P than in FeLV⁺R. Our results show a high prevalence of FeLV, different factors associated with the course of infection, and more frequent and severe hematologic changes in progressive infections compared with regressive infections.

Heartworm adulticide treatment: a tropical perspective

Dirofilaria immitis (the canine heartworm) is widespread in the tropics, with prevalence surpassing 30% in high-risk areas. In addition to the suitable climatic conditions that favour mosquito abundance and filarial larva development, there is low compliance with the recommended year-round use of preventives in these transmission hotspots. This represents a major concern, considering that melarsomine (first-line heartworm adulticide) is unavailable in several tropical countries, resulting in the so-called slow-kill protocol being the only available adulticide treatment option. In this article, the members of TroCCAP (Tropical Council for Companion Animal Parasites) review the current distribution of heartworm in the tropics and the availability of melarsomine, and discuss alternatives for the management of heartworm infections in dogs.

Human Pulmonary Dirofilariasis: A Review for the Clinicians

Human pulmonary dirofilariasis (HPD) is a rare zoonotic disease caused by Dirofilaria immitis, the nematode responsible for canine cardiopulmonary dirofilariasis (dog heartworm). The incidence of HPD is on the rise throughout the world due to increased awareness and factors affecting the vector (mosquito). Humans are accidental hosts for D. immitis. Most patients are asymptomatic and present with an incidental pulmonary nodule that mimics primary or metastatic pulmonary malignancy. Some patients suffer from pulmonary and systemic symptoms in the acute phase of pneumonitis caused by pulmonary arterial occlusion by the preadult worms resulting in pulmonary infarction and intense inflammation. These patients may have ill-defined pulmonary infiltrate on chest radiology. Pulmonary nodules represent the end result of initial pneumonitis. There are no specific clinical, laboratory, or radiologic findings that differentiate HPD from other causes of a pulmonary nodule. Although serologic tests exist, they are usually not commercially available. The majority of patients are diagnosed by histopathologic identification of the decomposing worm following surgical resection of the lesion.

What's New in Feline Leukemia Virus Infection

Feline leukemia virus (FeLV) is a retrovirus with global impact on the health of domestic cats that causes tumors (mainly lymphoma), bone marrow disorders, and immunosuppression. The importance of FeLV is underestimated due to complacency associated with previous decline in prevalence. However, with this comes lowered vigilance, which, along with potential for regressively infected cats to reactivate viremia and shed the virus or develop clinical signs, can pose a risk to feline health. This article summarizes knowledge on FeLV pathogenesis, courses of infection, and factors affecting prevalance, infection outcome, and development of FeLV-associated diseases, with special focus on regressive FeLV infection.

Canine heartworm and heat treatment: An evaluation using a well based enzyme-linked immunosorbent assay (ELISA) and canine sera with confirmed heartworm infection status

Heat treatment of serum has demonstrated improved detection of Dirofilaria immitis antigen in sera of sheltered dogs without knowing the true infection status of the animals and in dogs confirmed experimentally to be infected with heartworm. Utilizing archived sera with necropsy confirmed heartworm infection status (n = 665) and a micro-titer well based ELISA antigen assay, this study evaluated how the composition of heartworm infections affects antigen test results pre- and post-heat treatment, determined subsequent changes to the antigen test sensitivity and specificity, and application of optical density values. The composition of heartworm infections present in dogs with sera initially testing antigen negative consisted of infections by dead 1/34 (2.9 %), immature 10/34 (29.4 %), male only 7/34 (20.6 %), female only 5/34 (14.7 %), and mixed sex infections 11/34 (32.4 %) with 2-62 heartworms of which 6 were microfilaremic. The composition of heartworm infections remaining antigen negative post-heat treatment consisted of infections by dead 1/14 (7.1 %), immature 9/14 (64.3 %), male only 2/14 (14.3 %), and mixed sex infections 2/14 (14.3 %) with 6 and 62 heartworms of which 1 was microfilaremic. The overall sensitivity for all infections, mature heartworms, and mature females before heat treatment were 86.9 %, 90.7 %, and 93.3 % and after heat treatment sensitivity increased to 94.6 %, 98.4 %, and 99.2 % respectively. A decrease in specificity from 97.8%-96.1% was observed following heat treatment of heartworm negative sera. Optical density values for the varying infection intensities present in this study clearly indicate that result intensity is not reflective of the number of heartworms present. This study provides additional context for interpreting post-heat antigen results for dogs originating from animal shelters, demonstrates diagnostic utility of optical density, and highlights the need for improved heartworm diagnostics.

Activation of the Toll pathway in Aedes aegypti blocks the development of emerging third-stage larvae of drug-resistant Dirofilaria immitis

Dirofilaria immitis is the globally distributed agent of heartworm disease. Infection in canines causes debilitating disease that can be fatal if left untreated. Macrocyclic lactones can prevent heartworm disease in dogs, cats and ferrets by killing larvae before they develop into adult worms in the pulmonary artery. However, administration of prophylactic drugs to wild canids to prevent D. immitis infection is not feasible. Furthermore, a vaccine against heartworm is currently unavailable and drug resistant D. immitis have been identified, highlighting the need for new strategies to prevent parasite transmission. We recently established a method to block development of emerging third-stage larvae (eL3) from the mosquito Aedes aegypti by over-activating the Toll pathway, one of the major innate immune signaling pathways in mosquitoes. Our previous study used a drug-sensitive strain of D. immitis and it remains unknown if the strategy is effective against different D. immitis genotypes and, more importantly, if it would work against drug-resistant genotypes. The purpose of this study was to determine whether Toll pathway activation is capable of blocking eL3 development of D. immitis strains that are resistant to macrocyclic lactones. We infected mosquitoes with two independent strains of D. immitis previously confirmed as being resistant to macrocyclic lactones, and then activated Toll signaling by RNAi-mediated silencing of the pathway inhibitor, IκB/Cactus, and quantitatively measured eL3 development. Similar to the drug-sensitive strain, eL3 were strongly reduced by Toll activation in both drug-resistant strains. Furthermore, similar to the drug-sensitive strain, the reduction of eL3 in both drug-resistant strains suggests a defect in larval invasion of, or development in, the Malpighian tubules - the organ in the mosquito to which microfilariae migrate after ingestion and where the larvae undergo several developmental molts. In summary, Toll pathway activation blocks the development of three distinct D. immitis genotypes, including two different drug-resistant genotypes. If this strategy can be applied to heartworm vectors in the field, it may help reduce the spread of disease and is not predicted to favor the spread of drug resistance.

The global status of Dirofilaria immitis in dogs: a systematic review and meta-analysis based on published articles

Dirofilaria immitis is a parasitic filarial nematode responsible for heartworm disease in domestic as well as wild canines and felines and pulmonary or cutaneous infections in humans. This systematic review and meta-analysis aimed to evaluate the status of D. immitis in dogs based on available literature. Four English language databases (ISI Web of Science, Scopus, PubMed and Science Direct) containing data on D. immitis prevalence in dogs were thoroughly searched resulting in the inclusion of 193 studies. The findings revealed that the pooled and weighted prevalence of D. immitis infection in dog population based on published papers throughout the world was 10.91% (95% CI=10.18-11.65). In addition, subgroup analysis based on meta-regression revealed that a significant difference between the pooled and weighted prevalence of D. immitis in dogs and country (β =0.14, P=0.049). Given the relatively high prevalence of D. immitis infection in dogs and its adverse effects, it is suggested that to perform more research on the prevention and control of dirofilariasis infection in dogs worldwide.

Novel anti-Wolbachia drugs, a new approach in the treatment and prevention of veterinary filariasis?

Filarial nematodes are tissue-dwelling parasitic worms that can cause a range of disfiguring pathologies in humans and potentially lethal infections of companion animals. The bacterial endosymbiont, Wolbachia, is present within most human and veterinary filarial pathogens, including the causative agent of heartworm disease, Dirofilaria immitis. Doxycycline-mediated drug targeting of Wolbachia leads to sterility, clearance of microfilariae and gradual death of adult filariae. This mode of action is attractive in the treatment of filariasis because it avoids severe host inflammatory adverse reactions invoked by rapid-killing anthelmintic agents. However, doxycycline needs to be taken for four weeks to exert curative activity. In this review, we discuss the evidence that Wolbachia drug targeting is efficacious in blocking filarial larval development as well as in the treatment of chronic filarial disease. We present the current portfolio of next-generation anti-Wolbachia candidates discovered through phenotypic screening of chemical libraries and validated in a range of in vitro and in vivo filarial infection models. Several novel chemotypes have been identified with selected narrow-spectrum anti-Wolbachia specificity and superior time-to-kill kinetics compared with doxycycline. We discuss the opportunities of developing these novel anti-Wolbachia agents as either cures, adjunct therapies or new preventatives for the treatment of veterinary filariasis.

Ecological and Socioeconomic Factors Associated with Bartonella henselae Exposure in Dogs Tested for Vector-Borne Diseases in North Carolina

Bartonella henselae is a zoonotic vector-borne pathogen affecting both humans and dogs. Little is known about the epidemiology of B. henselae in dogs, including risk factors associated with exposure. The objectives of this study were to map the current distribution of B. henselae in dogs in North Carolina (NC) and to identify ecological and socioeconomic factors influencing B. henselae seroreactivity. Results from 4446 B. henselae serology samples from dogs in NC submitted by veterinarians for clinical diagnostic testing to the North Carolina State University College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2004 and December 31, 2015 were retrospectively reviewed. These results were used to generate a map of B. henselae seroreactivity. To account for sparsely sampled areas, statistical smoothing using head banging and areal interpolation kriging was performed. Using previously described risk factors for exposure to canine tick-borne diseases, eight multivariable logistic regression models based on biologically plausible hypotheses were tested, and a final model was selected using an Akaike's Information Criterion weighted-average approach. Seroreactivity among dogs tested for vector-borne disease was variable across the state: higher along the southern/eastern coastal plains and eastern Piedmont, and lower in the western mountains. Of 25 explanatory factors considered, the model combining demographic, socioeconomic, climatic, and land use variables fits best. Based on this model, female intact sex and increasing percentage of the county with low-intensity development and evergreen forest were associated with higher seroreactivity. Conversely, moderate development, increasing median household income, and higher temperature range and relative humidity were associated with lower seroreactivity. This model could be improved, however, by including local and host-scale factors that may play a significant role in dogs' exposure.

Dog importation and changes in heartworm prevalence in Colorado 2013-2017

Background

Animal welfare organizations, in order to increase dog adoptions and reduce euthanasia of homeless dogs, are transporting large numbers of dogs from state-to-state. Only approximately 1/3 of animal welfare organizations reportedly test for heartworm infection, treat, or provide heartworm prevention prior to transporting dogs. The reported prevalence of heartworms in dogs in animal shelters or rescued following natural disasters ranges between 14.6–48.8%. This analysis was conducted to evaluate the correlation between dog importation and heartworm prevalence in dogs in Colorado.

Methods

Data were obtained from the Companion Animal Parasite Council (CAPC) interactive heartworm prevalence maps and the Colorado Department of Agriculture Pet Animal Care Facilities Program (PACFA) in order to analyze the relationship between dog importation and the changes in prevalence of heartworm (Dirofilaria immitis) in Colorado from 2013 to 2017.

Results

The prevalence of heartworms in Colorado dogs has increased 67.5% between 2013–2017. From 2014 to 2017, more than 114,000 dogs were imported into Colorado by over 130 animal shelters and rescue organizations, which could represent approximately 9.5% of the total estimated 2017 Colorado dog population of nearly 1.2 million dogs. Three large Colorado-based organizations responded to requests for details regarding the originating states from which they received dogs. The majority of these dogs were apparently shipped to Colorado from states with higher heartworm prevalence. New Mexico represented the source of the greatest number of relocated dogs, accounting for just over 30%. Nearly half (49%) of the dogs relocated by these three organizations came from either Texas or Oklahoma.

Conclusions

Animal welfare organizations and veterinarians should increase the testing and prevention of heartworm infections in dogs both prior to, and following, transportation from areas with high heartworm prevalence. Repeated testing is recommended due to the 6-month pre-patent-period associated with D. immitis. Veterinarians and pet owners should increase vigilance with heartworm testing and prevention, even in areas with historically low heartworm prevalence. Movement of dogs from highly endemic areas may increase the risks of local transmission.

Approaches to Canine Heartworm Disease Treatment Among Alumni of a Single College of Veterinary Medicine

This descriptive study was designed to ascertain the current heartworm treatment strategies employed by veterinary graduates of a single college of veterinary medicine, to assess the frequency with which each of these treatment strategies is prescribed, and to report the motivation behind the use of these treatment strategies. A survey containing a combination of multiple-choice and open-ended questions was distributed via e-mail with an online link during 2013 to graduates of the University of Georgia College of Veterinary Medicine. Demographic data and opinions regarding treatment for cases of canine heartworm disease (HWD) were obtained, and motivation for recommending different treatment strategies was assessed. Nearly all 170 respondents (99%) indicated that they recommend melarsomine dihydrochloride for first-line treatment of canine HWD. Exercise restriction (80%) and monthly heartworm preventive (75%) were components of the treatment approach to HWD with no clinical signs. The majority of respondents (74%) indicated that when first-line treatment recommendations were declined, they endorsed long-term administration of ivermectin (i.e., "slow-kill" method) despite current American Heartworm Society guidelines that recommend against the use of long-term macrocyclic lactone administration for the monotherapy treatment of canine HWD. Respondents also indicated that owners' financial concerns frequently result in modification of HWD treatment. Routine inclusion of exercise restriction is commonly, but not universally, utilized and may represent an opportunity for improvement in the management of this disease. In addition, when first-line recommendations for heartworm disease treatment are declined, a two-dose melarsomine protocol instead of the slow-kill method should be considered.

Prevalence of canine heartworm infection in Mississippi animal shelters

Understanding diagnosis of heartworm disease in the context of animal shelters' needs and expectations is crucial for developing guidelines that specifically address the unique shelter population. Accurate and economical heartworm testing strategies are essential. However, current comprehensive guidelines for the management of heartworm disease in dogs are directed toward client-owned animals and do not address needs of animal shelters and other resource-scarce facilities. Additionally, testing recommendations do not take into account regional and local differences in heartworm prevalence across the United States that occur due to abiotic and biotic factors. The objective of this study was to determine the apparent prevalence of Dirofilaria immitis microfilaremia and antigenemia in dogs from Mississippi animal shelters. Further, we compare agreement between microfilaria and antigen testing in this population. We performed a cross-sectional study using canine serum and blood bank samples representative of the Mississippi shelter population. Microfilaria testing of whole blood included a blood smear and modified Knott test. Antigen testing of serum was performed using the DiroCHEK^® antigen ELISA test. Analyses included descriptive and analytic statistics as well as Cohen's kappa for test agreement. A total of 283 whole blood samples and 363 serum samples, representing 363 dogs from 18 shelters in 17 Mississippi counties, were utilized in this study. Sixty-four (22.6%) whole blood samples demonstrated D. immitis microfilariae on the modified Knott test and 125 (34.4%) serum samples had detectable D. immitis antigen. Increasing age and low body condition were associated with antigen-positive test results. Only age was associated with microfilaria-positive test results. There was moderate agreement between the antigen ELISA test and the modified Knott microfilaria test and poor agreement between the antigen ELISA and the blood smear. This study provides the first known report of the prevalence of D. immitis microfilaremia and antigenemia in Mississippi shelter dogs. We observed that prevalence of both microfilaremia and antigenemia was significantly higher in these sampled dogs compared to previous reports for the owned canine population in Mississippi. Heartworm infection presents unique management challenges for animal shelters. Knowledge of the expected prevalence in the area can be utilized for management decisions related to prevention, testing, and treatment of dogs in shelter populations.

Bartonella Seroepidemiology in Dogs from North America, 2008-2014

BACKGROUND

Improved understanding of Bartonella species seroepidemiology in dogs may aid clinical decision making and enhance current understanding of naturally occurring arthropod vector transmission of this pathogen.

OBJECTIVES

To identify demographic groups in which Bartonella exposure may be more likely, describe spatiotemporal variations in Bartonella seroreactivity, and examine co-exposures to other canine vector-borne diseases (CVBD).

ANIMALS

A total of 15,451 serology specimens from dogs in North America were submitted to the North Carolina State University, College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2008, and December 31, 2014.

METHODS

Bartonella henselae, Bartonella koehlerae, and Bartonella vinsonii subspecies berkhoffii indirect fluorescent antibody (IFA) serology results, as well as results from a commercial assay kit screening for Dirofilaria immitis antigen and Ehrlichia species, Anaplasma phagocytophilum, and Borrelia burgdorferi antibodies, and Ehrlichia canis, Babesia canis, Babesia gibsoni, and Rickettsia species IFA results were reviewed retrospectively.

RESULTS

Overall, 3.26% of dogs were Bartonella spp. seroreactive; B. henselae (2.13%) and B. koehlerae (2.39%) were detected more frequently than B. vinsonii subsp. berkhoffii (1.42%, P < 0.0001). Intact males had higher seroreactivity (5.04%) than neutered males (2.87%, P < 0.0001) or intact or spayed females (3.22%, P = 0.0003). Mixed breed dogs had higher seroreactivity (4.45%) than purebred dogs (3.02%, P = 0.0002). There was no trend in seasonal seroreactivity; geographic patterns supported broad distribution of exposure, and co-exposure with other CVBD was common.

CONCLUSIONS AND CLINICAL IMPORTANCE

Bartonella spp. exposure was documented throughout North America and at any time of year. Male intact dogs, mixed breed dogs, and dogs exposed to other CVBD have higher seroreactivity to multiple Bartonella species.

Pharmacokinetics and efficacy of an ivermectin implant for long-term prevention of Dirofilaria immitis infection in dogs

An exploratory study was carried out to assess the in vivo efficacy of different prototypes of subcutaneous implants containing ivermectin (IVM) for the prevention of canine Dirofilaria immitis infection. The implants consisted of an ethylcellulose matrix containing IVM (3.0, 4.5, and 6.0 mg/implant; from 0.29 to 0.63 mg/kg bw) as active ingredient designed to release approximately 0.1 ng of IVM/mL in the plasma for at least 12 months. Six dogs were implanted on day -365. On day -12, three heartworm-free dogs were included in the study as a control group. All nine dogs were examined on day -7 and day 0 for circulating D. immitis microfilariae and by an antigen ELISA kit to confirm that the dogs were heartworm-free. The dogs were artificially infected with 75 D. immitis infective larvae (L3) each on day 0. Dogs in the control group were humanely euthanized on day 153 to verify the infectivity of the larvae, while implanted dogs were further examined for circulating D. immitis microfilariae and antigen on days 153, 195, and 246. The treated dogs were not necropsied. The pharmacokinetic profile of the IVM implant was assessed in plasma samples taken on day -364, then at different times until the infection day, and again on days, 15, 30, 60, 90, 120, and 153. Throughout the study, body weights were measured during clinical examination on days 0, 30, 60, 90, 120, and 153. At necropsy, all control dogs were found infected, each with 10-11 adult heartworms. Implanted dogs were negative at both microfilaria and D. immitis antigen examinations until day 246 (8 months from the infection). IVM plasma levels ranged 0.06-0.16 ng/mL on day 0 and remained stable until day 60, afterward they gradually decreased under the limit of quantification of the method. Throughout the study, no side effect was observed. On the basis of these results, it was possible to conclude that the different prototypes of implants were able to protect the dogs from D. immitis artificial infection for at least 12 months.

Dirofilariosis in the Americas: a more virulent Dirofilaria immitis?

Dirofilarioses are widespread diseases caused by filarioid nematodes (superfamily Filarioidea) of the genus Dirofilaria, which are transmitted by a plethora of mosquito species. The principal agent of canine dirofilariosis in the Americas is Dirofilaria immitis, which may also occasionally infest humans, resulting in pulmonary nodules that may be confounded with malignant lung tumours. Because human cases of dirofilariosis by D. immitis are relatively frequent in the Americas and rare in Europe and other eastern countries, where Dirofilaria repens is the main causative agent, the existence of a more virulent strain of D. immitis in the Americas has been speculated. Recently, a case of human ocular infestation by Dirofilaria sp. was diagnosed in Pará State, northern Brazil, where canine heartworm dirofilariosis is endemic. The nematode was shown to be morphologically and phylogenetically related to D. immitis but it was genetically distinct from reference sequences, including those of D. immitis infesting dogs in the same geographical area. This finding raised questions regarding the aetiology of human dirofilariosis in the Americas, since information on the genetic makeup of filarioids infesting dogs and humans is meagre. Further studies would be needed to better characterize filarioids infesting dogs, wild animals, and humans in the Americas and to assess the existence of a more virulent D. immitis strain in this continent. Finally, the competence of different culicid species/strains from Europe and the Americas as vectors of Dirofilaria species should be investigated. Such studies would help us to understand possible variations in transmission patterns and even to predict possible scenarios that may emerge in the future, with the introduction of non-endemic Dirofilaria species/strains in free areas through importation of infested animals, vectors, or both.

Key factors influencing canine heartworm, Dirofilaria immitis, in the United States

An examination of the Companion Animal Parasite Council's (CAPC) canine heartworm data to clarify the spatial prevalence of heartworm in the United States. Factors thought to influence the spatial risk of disease, as identified in a recent CAPC workshop, are discussed.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

Prevalence of infectious diseases in cats and dogs rescued following Hurricane Katrina

OBJECTIVE

To determine the prevalence of infectious diseases of animal and zoonotic importance in cats and dogs rescued and transferred from the Gulf Coast region following Hurricane Katrina.

DESIGN

Cross-sectional study.

ANIMALS

414 dogs and 56 cats rescued and transferred from the Gulf Coast region within 4 months after the hurricane.

PROCEDURES

EDTA-anticoagulated blood and serum samples were tested via PCR and serologic assays for infectious diseases.

RESULTS

In dogs, prevalence was highest for anti-West Nile virus (WNV) antibodies (218/390 [55.9%]), Dirofilaria immitis antigen (195/400 [48.8%]), anti-Toxoplasma gondii antibodies (92/366 [25.1%]), and hemotropic mycoplasma DNA (40/345 [11.9%]). The DNA of Bartonella spp, Ehrlichia spp, or Babesia spp or anti-canine influenza virus antibodies were identified in < 2% of dogs. In cats, prevalence was highest for antibodies against Bartonella spp and DNA of Bartonella spp combined (49/55 [89.1 %]), anti-T gondii antibodies (13/55 [23.6%]), hemotropic mycoplasma DNA (5/47 [10.6%]), anti-WNV antibodies (5/48 [10.4%]), D immitis antigen (4/50 [8.0%]), and anti-FIV antibodies (4/56 [7.1%]). A total of 308 (74.4%) dogs and 52 (92.9%) cats had evidence of previous or current vector-borne infections.

CONCLUSIONS AND CLINICAL RELEVANCE

Cats and dogs rescued from the disaster region had evidence of multiple infectious diseases. The dispersal of potentially infectious animals to other regions of North America where some infections were not typically found could have contributed to new geographic ranges for these organisms or to underdiagnosis in affected animals because of a low index of suspicion in regions with low disease prevalence.

Phylogenetic characterisation of naturally occurring feline immunodeficiency virus in the United Kingdom

Feline immunodeficiency virus (FIV) is a significant pathogen of domestic and non-domestic felids worldwide. In domestic cats, FIV is classified into five distinct subtypes (A–E) with subtypes A and B distributed most widely. However, little is known about the degree of intrasubtype viral diversity and this may prove critical in determining whether monovalent vaccines are likely to protect against FIV strains within a single subtype. Here, we characterise novel env sequences from 47 FIV strains recovered from infected cats in the United Kingdom and its environs. Phylogenetic analyses revealed that all bar one sequence belonged to subtype A, the predominant subtype in Western Europe. A single sequence was identified as a likely subtype A/C recombinant, intriguing given that subtype C does not appear to exist in either the UK or North Western Europe and suggestive of a recombination event predating its introduction into the UK. Subtype A strains from the UK were not significantly differentiated from representative subtype A isolates found elsewhere suggesting multiple introductions of FIV into the country. Divergence among isolates was comparable to that observed for subtype A isolates worldwide, indicating that FIV in the UK covers the full spectrum of subtype A diversity seen globally. This study demonstrates that while subtype A is predominant in the UK, novel introductions may result in the emergence of novel subtypes or intersubtype recombinants, potentially circumventing vaccine strategies. However, the dominance of subtype A suggests that the development of a regional or subtype-specific protective vaccine for the UK could be achievable.

Diagnostic, treatment, and prevention protocols for canine heartworm infection in animal sheltering agencies

The high prevalence of heartworm infection in shelter dogs creates a dilemma for shelter managers, who frequently operate with insufficient funding, staffing, and expertise to comply with heartworm guidelines developed for owned pet dogs. The purpose of this study was to survey canine heartworm management protocols used by 504 animal sheltering agencies in the endemic states of Alabama, Florida, Georgia, and Mississippi. Open-admission shelters, which tended to be larger and more likely to perform animal control functions, were less likely (41%) to test all adult dogs than were limited-admission shelters (80%), which tended to be smaller non-profit humane agencies, and foster programs (98%) based out of private residences. Open-admission shelters were more likely to euthanize infected dogs (27%) or to release them without treatment (39%), whereas limited-admission shelters and foster programs were more likely to provide adulticide therapy (82% and 89%, respectively). Of the 319 agencies that treated infections, 44% primarily used a standard two-dose melarsomine protocol, and 35% primarily used a three-dose split-treatment melarsomine protocol. Long-term low-dose ivermectin was the most common treatment used in 22% of agencies. Open-admission shelters were less likely (35%) to provide preventive medications for all dogs than were limited-admission shelters (82%) and foster programs (97%). More agencies used preventives labeled for monthly use in dogs (60%) than ivermectin products labeled for livestock (38%). The most common reason diagnostic testing and preventive medication was not provided was cost. These results indicate a lack of protocol uniformity among agencies and insufficient resources to identify, treat, and prevent infection. Sheltering agencies and companion animal health industries should develop guidelines that are feasible for use in sheltering agencies and provide improved access to preventive and treatment strategies for management of Dirofilaria immitis.

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.

Heartworm disease in animals and humans

Heartworm disease due to Dirofilaria immitis continues to cause severe disease and even death in dogs and other animals in many parts of the world, even though safe, highly effective and convenient preventatives have been available for the past two decades. Moreover, the parasite and vector mosquitoes continue to spread into areas where they have not been reported previously. Heartworm societies have been established in the USA and Japan and the First European Dirofilaria Days (FEDD) Conference was held in Zagreb, Croatia, in February of 2007. These organizations promote awareness, encourage research and provide updated guidelines for the diagnosis, treatment and prevention of heartworm disease. The chapter begins with a review of the biology and life cycle of the parasite. It continues with the prevalence and distribution of the disease in domestic and wild animals, with emphasis on more recent data on the spreading of the disease and the use of molecular biology techniques in vector studies. The section on pathogenesis and immunology also includes a discussion of the current knowledge of the potential role of the Wolbachia endosymbiont in inflammatory and immune responses to D. immitis infection, diagnostic use of specific immune responses to the bacteria, immunomodulatory activity and antibiotic treatment of infected animals. Canine, feline and ferret heartworm disease are updated with regard to the clinical presentation, diagnosis, prevention, therapy and management of the disease, with special emphasis on the recently described Heartworm Associated Respiratory Disease (HARD) Syndrome in cats. The section devoted to heartworm infection in humans also includes notes on other epizootic filariae, particularly D. repens in humans in Europe. The chapter concludes with a discussion on emerging strategies in heartworm treatment and control, highlighting the potential role of tetracycline antibiotics in adulticidal therapy.