Abstract
The objective of the present study was to evaluate the therapeutic efficacy of a generic
doxycycline tablet (DoxyVet®) against Ehrlichia canis infection in dogs. Canine monocytic
ehrlichiosis is caused by the bacterium E. canis and transmitted by the brown kennel tick
(Rhipicephalus sanguineus). Six disease-free and tick-free dogs were infested with E. canisinfected
ticks. Once diagnosed (with polymerase chain reaction [PCR] analysis and platelet
counts) as positive for infection, doxycycline tablets were administered orally once a day for
20 consecutive days, at a target dose level of 10 mg/kg. The actual dose administered was
calculated as ranging between 10 mg/kg and 11.7 mg/kg. The PCR analysis, 28 days after the
first administration of the tablets, failed to detect E. canis in any of the dogs. On Day 56 of the
study, four of the dogs were diagnosed with E. canis for the second time and a fifth dog was
diagnosed on Day 70. The platelet counts of the sixth dog remained within normal levels and it
was discharged from the study on Day 84. Doxycycline tablets were then administered to the
remaining five infected dogs for 28 consecutive days. Four of these dogs had no positive PCR
results during the following 3 months. The fifth dog was diagnosed with E. canis for the third
time 58 days after the last tablets of the second treatment had been administered, after which
it was rescue treated (doxycycline for a further 28 days). The results indicate that doxycycline
administered in tablet form (DoxyVet®) at 10 mg/kg – 11.7 mg/kg body mass once daily for 28
consecutive days clears most dogs of infection. The importance of a concomitant tick-control
programme is therefore stressed.