Use of doxycycline in cats and dogs (part 2)
1. Duration of infection and efficacy of doxycycline treatment in dogs experimentally co-infected with Anaplasma platys and Ehrlichia canis. Procc ACVIM 2008. MJ Beall et al.
Co-infection with Anaplasma platys and Ehrlichia canis is difficult to diagnose because they share very similar clinical pictures. Both agents cause anaemia, thrombocytopaenia and leukopaenia. The study assessed the clinical significance of co-infection with respect to disease duration and treatment efficacy.
A total of 36 dogs, divided into six groups, were studied. A. platys and/or E. canis infection was provoked experimentally and subjects compared against a control group. Weekly blood tests were performed for 7 months. The infections were confirmed by PCR and serology.
Doxycycline was administered at 211 days postinfection (PI) (10 mg/kg/day orally for 28 days). Subjects were immunosuppressed using dexamethasone at 410 days PI.
In the case of dogs infected with A. platys, platelets normalised at 115 days PI and the PCR was negative at 110 days PI. Dogs co-infected with A. platys and E. canis were also rendered negative for A. platys prior to doxycycline administration.
If the dogs infected with E. canis, either as a mono-infection or co-infection, were not treated, they remained positive for over a year. After immunosuppression, neither A. platys nor E. canis was detected by PCR in dogs treated with doxycycline.
This study demonstrates the efficacy of doxycycline treatment.
2. Randomized masked controlled clinical trial to compare 7-day and 14-day course length of doxycycline in the treatment of Mycoplasma felis infection in shelter cats. Kompare B et al. Comp Immunol Microbiol Infect Dis 2012
This study compared the clinical and microbiological efficacy of doxycycline treatment for 7 or 14 days in cats infected with Mycoplasma felis and displaying signs of upper respiratory tract disease (URTD).
Forty cats were randomised to the 7-day treatment group (Doxy-7) or the 14-day group (Doxy-14).
No differences were observed in Mycoplasma load after 7 days, but the load was lower in the Doxy-14 group by day 14. On day 14, 55% of the Doxy-7 cats and 25% of the Doxy-14 cats were still PCR positive for M. felis.
The study concluded that cats with URTD and M. felis infection have a better microbiological response to 14-day treatment with oral doxycycline compared to 7-day treatment.
3. Susceptibility of bacteria from feline and canine urinary tract infections to doxycycline and tetracycline concentrations attained in urine four hours after oral dosage. Wilson, B et al. Aust. Vet. J. 84:8-11. 2006.
The study measured tetracycline concentrations in cats and dogs 4 hours after oral administration. The aim was to determine whether the antibiotic concentration was still enough to be effective and protect against microorganisms.
It was a prospective study in which doxycycline monohydrate was given to 9 cats and 8 dogs and tetracycline to 8 dogs for 3 days. Blood was collected after 2 and 4 hours and urine after 4 hours. Concentrations were higher in urine than in serum after 4 hours.
In a follow-up experiment, 45 urine samples from cats and dogs with urinary infections were cultured and tested against doxycycline, tetracycline or amoxicillin/clavulanic acid. Most of the microorganisms isolated were sensitive to the doxycycline and tetracycline concentrations in the urine. However, 41 cultures were sensitive to amoxicillin/clavulanic acid.
In summary, several studies have shown that the use of doxycycline in cats and dogs is effective against microorganisms such as Anaplasma platys, Ehrlichia canis and Mycoplasma felis.
