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Peer-reviewed veterinary case report

Heartworm infection still common in northern Italy shelter dogs

By Genchi, Marco et al.·Published in Parasites & vectors·2025·Department of Veterinary Sciences, Italy·View original on PubMed

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Original publication title: Do not let your guard down! Prevalence of Dirofilaria immitis and Dirofilaria repens in dogs entering shelters in northern Italy.

Species:
dog

Plain-English summary

A study found that about 34% of stray dogs entering shelters in northern Italy tested positive for heartworm (Dirofilaria immitis) and a related parasite (Dirofilaria repens). Out of 510 dogs tested, 15.7% had heartworm, while 6.9% had the other parasite, and some had both. This indicates that unowned dogs can carry these parasites, which poses a risk to other dogs in the area. It's important for dog owners to keep their pets on heartworm prevention to reduce the risk of infection.

People also search for: dog heartworm prevention · symptoms of heartworm in dogs · stray dog heartworm risk

Abstract

BACKGROUND: In Italy, the area of highest prevalence for canine heartworm disease (CHWD) has historically been along the Po River Valley in the northern area of the country, where prevalence in the mid-nineties ranged from 31% to 98%. Currently, increased awareness among practitioners and the availability of preventives have led to a dramatic decrease in prevalence in the area, although cases of CHWD continue to be diagnosed, suggesting the presence of canine reservoirs, including unowned dogs. METHODS: The aim of the present study was to determine the prevalence of Dirofilaria spp. in stray dogs entering shelters located in the Po River Valley of northern Italy by using the modified Knott's test and by antigenic testing. RESULTS: Out of the 510 dogs tested, 173 (33.9%) were positive for circulating microfilariae: 15.7% (80/510) with D. immitis, 6.9% (35/510) with D. repens, and 11.4% (58/510) with a mixed infection. CONCLUSIONS: Unowned dog populations represent an important reservoir for the parasite, allowing D. immitis to remain in a given geographical area and increasing the risk of exposure to all dogs.

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Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/41088414/