Abstract
This study describes two different manifestations of Dirofilaria repens infection in sibling dogs with microfilaremia. Dog 1, asymptomatic, harbored a gravid female of D. repens on the parietal layer of tunica vaginalis of one testicle and showed a marked circulating eosinophilia (3.3·103/μL). Both testicles were normal in shape and size without any gross lesions. Dog 2 had a pyotraumatic dermatitis. The cases were confirmed by PCR and sequencing. The sequences obtained showed 100% identity with those of D. repens isolated from human scrotum in Croatia. The treatment with moxidectin 2.5% and imidacloprid 10%/kg was effective in eliminating microfilariae after just one application, as demonstrated by negative modified Knott’s tests and PCR analyses of blood samples. This status was maintained during the post-treatment observation period. The classical localization of D. repens in dogs is in subcutaneous tissues, within nodules or free; however, it can also occur with some frequency in testicles, as described in humans. The infection can be associated with circulating eosinophilia or pyotraumatic dermatitis, as reported in this study. Thus, in endemic areas, it is advisable to carefully inspect the removed testicles at neutering since parasite localization can take place without any macroscopic changes. Moreover, in the case of circulating eosinophilia or pyotraumatic dermatitis, investigations should include modified Knott’s test and PCR to ensure that D. repens is not the cause of these alterations. Rapid and sensitive tests for the early detection of infected animals would help to prevent or limit the spread of this zoonosis.
Highlights
The nematode Dirofilaria repens is responsible for canine subcutaneous dirofilariasis and it is the main agent of human dirofilariasis in the Old World
We describe two different manifestations of D. repens infection in sibling dogs with microfilaremia
An echocardiogram was performed on both dogs in order to exclude the presence of D. immitis, whereas a Baermann test was carried out only on dog 1 in order to exclude the presence of the lungworm Angiostrongylus vasorum, common cause of eosinophilia in dogs
Summary
The nematode Dirofilaria repens is responsible for canine subcutaneous dirofilariasis and it is the main agent of human dirofilariasis in the Old World. D. repens adult worms live in the subcutaneous and intramuscular connective tissues of dogs and other carnivores. The females, as viviparous, release the first larval stage (L1) in the peripheral blood after mating. The infective stage can be transmitted among dogs or to humans through the bite of several mosquito genera (Aedes, Culex, Anopheles, Coquillettidia). While there is a rapid test for the dog heartworm Dirofilaria immitis, no similar tests are available to detect D. repens–infected animals, making the undiagnosed dogs the main source of infection for other dogs and humans (Capelli et al 2018)
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