Heartworm prevalence in dogs versus cats: Multiple diagnostic modalities provide new insights

Hays, Kellie M.; Rodriguez, Jessica Y.; Little, Susan E.; Litster, Annette; Mwacalimba, Kennedy; Sundstrom, Kellee D.; Amodie, Deborah; Serrano, María A.; Guérios, S. D.; Lane, Jennifer N.; Levy, Julie

doi:10.1016/j.vpoa.2020.100027

Cited by 24 publications

(29 citation statements)

References 33 publications

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“…Surveys of the number of dogs treated for heartworm are useful but cannot be directly compared to infection prevalence trends, and artificial increases in percent positive results can be seen when testing is used primarily for diagnostic verification of a suspected infection rather than for routine screening [ 28 , 29 ]. For example, the similar percent positive test results in dogs in Alaska (1.4%) and Florida (1.4%) in the present study likely reflect targeted testing by Alaska veterinarians based on a travel history compared to routine screening of dogs protected from infection by preventives despite intense transmission pressure in Florida [ 30 ]. Nonetheless, heartworm is a preventable infection, and the finding that 1.4% of pet dogs receiving veterinary care in the USA, or approximately 840,000 pet dogs overall, are identified as infected with this potentially fatal parasite each year, is dispiriting.…”

Section: Discussionmentioning

confidence: 64%

Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2013–2019

et al. 2021

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Background Dogs in the US are commonly infected with vector-borne pathogens, including heartworm and tick-borne disease agents. The geographic distribution of both arthropod vectors and the pathogens they transmit continues to expand. Methods To describe the current geographic distribution and prevalence of antigen of Dirofilaria immitis and antibody to Borrelia burgdorferi, Ehrlichia spp., and Anaplasma spp. in dogs, we summarized over 144 million test results from 2013 to 2019, inclusive, by county, state, and region. Canine seroprevalence by state was compared to population-adjusted human reports of tick-borne diseases. Results Results varied regionally, with D. immitis antigen and Ehrlichia spp. antibodies more frequently detected in the Southeast (2.6% and 5.2%, respectively) and antibody to B. burgdorferi and Anaplasma spp. most common in the Northeast (12.1% and 7.3%, respectively). Overall, percent positive test results to D. immitis decreased in the Southeast by 33.3% when compared to earlier summaries using the same strategy (from 3.9 to 2.6%). Geographic expansion of areas where dogs commonly test positive for Ehrlichia spp. was evident, likely because of a change in the test made in 2012 to allow detection of antibodies to E. ewingii concomitant with expansion of vector tick populations. Percent positive test results to Ehrlichia spp. increased in every region; this shift was particularly pronounced in the Southeast, where percent positive test results increased fourfold (from 1.3 to 5.2%). Continued geographic expansion of B. burgdorferi and A. phagocytophilum was apparent in the Northeast, Midwest, and Upper South, although canine seroprevalence of antibody to B. burgdorferi was much lower than prior surveys in many Lyme-endemic areas. Annual reports of human cases of Lyme disease, ehrlichiosis, and anaplasmosis were associated with percent positive canine results by state for the three tick-borne disease agents (R2 = 0.812, 0.521, and 0.546, respectively). Within endemic areas, percent positive test results for all three tick-borne agents demonstrated evidence of geographic expansion. Conclusions Large scale analysis of results from screening dogs in practice for evidence of vector-borne infections, including those with zoonotic importance, continues to be a valuable strategy for understanding geographic trends in infection risk over time.

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Section: Discussionmentioning

confidence: 64%

Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2013–2019

et al. 2021

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“…The findings of this study, no observed cross-reactivity by A. reconditum post heat-ICD, agree with previous observations of previous studies using heat ICD in dogs where the heartworm status was unknown, only A. reconditum microfilariae were detected, and no antigen detected following post-heat ICD [ 3 , 35 ]. Recently in a study involving shelter animals from Florida, USA, 2 dogs with only A. reconditum microfilariae, initially tested “no antigen detected” but converted to post-heat ICD antigen positive [ 36 ]. Though the true heartworm status was unknown, those 2 dogs likely had occult heartworm infections resulting in the post-heat ICD positive results.…”

Section: Discussionmentioning

confidence: 99%

“…Given the recent reports of D. repens in a shelter dog and cat from a Florida, USA shelter and unknown whether those cases were imported or were acquired locally, there is a need for a multiple diagnostic approach and increased awareness and surveillance particularly among sheltered animals [36]. It has been recognized that imported or travel related introduction of parasites to non-endemic areas are not uncommon and suggested that veterinarians should consider non-endemic parasites as differential diagnoses [21].…”

Section: Discussionmentioning

confidence: 99%

Detection of heartworm antigen without cross-reactivity to helminths and protozoa following heat treatment of canine serum

et al. 2021

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Background Detection of Dirofilaria immitis, or heartworm, through antigen in sera is the primary means of diagnosing infections in dogs. In recent years, the practice of heat-treating serum prior to antigen testing has demonstrated improved detection of heartworm infection. While the practice of heat-treating serum has resulted in earlier detection and improved sensitivity for heartworm infections, it has been suggested that heat treatment may cause cross reactivity with A. reconditum and intestinal helminth infections of dogs. No studies have assessed the potential cross-reactivity of these parasites with heartworm tests before and after heat treatment using blood products and an appropriate gold standard reference. Methods Canine sera (n=163) was used to evaluate a heartworm antigen-ELISA (DiroCHEK®) and potential cross-reactivity with common parasitic infections. The heartworm status and additional parasite infections were confirmed by necropsy and adult helminth species verified morphologically or by PCR, and feces evaluated by centrifugal fecal flotation. Results Intestinal parasites were confirmed in 140 of the dogs by necropsy, and 130 by fecal flotation. Acanthocheilonema reconditum microfilariae were confirmed in 22 dogs. Prevalence of heartworm infection confirmed by necropsy was 35.6% (58/163). In the 105 dogs without heartworms, specificity remained unchanged at 100% both before and after heat treatment despite confirmed infections with A. reconditum, Ancylostoma caninum, Ancylostoma brasiliense, Trichuris vulpis, Toxocara canis, Dipylidium caninum, Spirometra mansonoides, Macracanthorynchus ingens, Cystoisospora sp., Giardia sp., and Sarcocystis sp. Conclusions These findings suggest that the use of heat treatment improves sensitivity of heartworm tests and is unlikely to cause false positive antigen results due to Acanthocheilonema reconditum, intestinal helminths, and protozoal parasites in dogs. Graphic abstract

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“…Previous studies in St Kitts showed higher prevalence, 26% for T. felis and 22% for P. fastosum [ 8 ]. Regarding D. immitis , given that adult infections are rare in cats compared to dogs, the negative antigen tests were not unexpected [ 20 ]. The negative antibody tests might also be due to the spatial heterogeneous distribution of D. immitis on St Kitts [ 21 ] or the small sample size, especially since over half of the cats were on a heartworm preventative.…”

Section: Discussionmentioning

confidence: 99%

Importation of cats and risk of parasite spread: a Caribbean perspective and case study from St Kitts

et al. 2020

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Background In more recent years, international travel with cats has increased. The distribution of cat parasites can change with this movement. Already, subtropical and tropical parasites have been reported by veterinarians in areas where they are not naturally present. Understanding the prevalence of tropical and subtropical parasites in Caribbean islands and the risk of importation to temperate areas could enable improved prevention recommendations and border control import requirements. Methods We present a study focused on cat owning students enrolled in a Doctor of Veterinary Medicine (DVM) programme on St Kitts. Owners were interviewed about their cats and their use of parasiticides. Cats were examined for Trichuris felis and Platynosomum fastosum using sugar flotation, Lynxacarus radovskyi using an adhesive tape test, and Dirofilaria immitis using commercial antigen and antibody tests. Results Data on 115 cats owned by 87 DVM students were collected and 90 cats, all expected to travel to the USA, were examined. Most of the cats were adults and born in St Kitts. Prevalence was reported as 6.8% (95% confidence interval (CI): 2.2–15.1%) for T. felis, 16.2% (95% CI: 8.7–26.6%) for P. fastosum and 6.8% (95% CI: 2.5–14.3%) for L. radovskyi. All D. immitis tests were negative. DVM students reported a high level of deworming (83.3% of the cats), but the number of cats treated per recommendations were low (56.1% for endoparasites and 70.8% for ectoparasites). Also, there was a lack of clarity regarding the purpose of the treatments used and treatments did not appear to be targeted for the parasites present. Conclusion Our results indicate a low prevalence of the parasites of interest in the DVM student cat population compared to other prevalence studies from the Caribbean. However, a degree of non-compliance with parasiticide uses and the high number of cats traveling to the USA indicate a medium risk of importation of tropical and subtropical cat parasites to temperate areas. We recommend stronger health inspections and health screening requirements at the borders including the development of specific parasiticide protocols for cat importation.

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Heartworm prevalence in dogs versus cats: Multiple diagnostic modalities provide new insights

Cited by 24 publications

References 33 publications

Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2013–2019

Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2013–2019

Detection of heartworm antigen without cross-reactivity to helminths and protozoa following heat treatment of canine serum

Importation of cats and risk of parasite spread: a Caribbean perspective and case study from St Kitts

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