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TDK conference 2018

Moxidectin-doxycycline combined treatment for D. immitis heartworm infestation in dogs
Sipos Eszter - year 5
University of Veterinary Medicine Budapest, Department of Pharmacology and Toxicology
Supervisor: Dr. Ákos Jerzsele


In Hungary, the prevalence of heartworm disease caused by D. immitis has risen significantly since 2006. With the progress in the development of diagnostic techniques, efficacy of detection and diagnosis improved widely both in canids and felids. As heartworm disease affects more and more dogs recently, correct protocols of early diagnosis and prevention should be performed. Application of larvicide and repellent substances can be efficient. The treatment protocol carried out in our study was more effective than the classic „golden-standard” therapy which is not always available and has many side-effects. The name of this type of treatment is „combined slow kill protocol”. These protocols recommend the elimination of melarsomine and the use of moxidectin which is not only an outstanding larvicide agent but its adulticide effect is also impressive (95,9°%). Application of doxycyclin for a month is present in this protocol, too.

In this study, dogs at Rex Dog Shelter Foundation were treated with our protocol. Blood samples were taken from 100 dogs currently living at the shelter, and were tested with „Witness Heartworm Antigen Test Kit” (Zoetis), „DiroCHEK Heartworm Antigen Test Kit” (Zoetis), modified Knott’s technique and PCR. Quick tests and ELISA showed same results, 5 dogs were heartworm positive. L1 stadium larvae were also found in 5 samples with modified Knott’s technique. Final results were carried out by PCR which resulted 3 D. immitis positive samples, 2 D. repens positive samples and one which was infected with both. One of the heartworm positive dogs deceased before the beginning of the treatment, necropsy was performed. During the recovery of the carcass, two adult heartworms were found in the pulmonary vein where it drains into the left atrium.

After the tests, the treatment of the five positive dogs were immediately started. Our protocol was finished at six months but continuing after this paper. At the end of our study, all the blood samples of the treated dogs were PCR and modified Knott’s technique negative, „Witness Heartworm Antigen Test Kit” and „DiroCHEK Heartworm Antigen Test Kit” still showed positive results in two samples. Therefore, our study presented promising results. In six months, microfilaria were 100% destroyed, and our protocol had 60% effectiveness against adult worms. With this protocol, no side-effects were observed during the treatment. The danger of evolving resistency and its chronic effects was minimalised by usage of combinated medical substances. No problems were caused by susceptibility gap as the combination of moxidectin and doxycyclin are effective against every stadium in the life cycle of D. immitis.

Observations showed that this protocol might be successfully used in the treatment of heartworm disease in Hungary as a potential alternative to complex therapy with melarsomine.

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