Application of the patch even up to 3 days after a bite eliminated B burgdorferi in this very promising animal trial
A number of dangerous diseases, including Lyme disease, are transmitted by infected ticks. Blood-sucking ticks ingest the agents that cause disease (bacteria of the species Borrelia burgdorferi and its relatives in the case of Lyme disease) during a blood meal, and subsequently transmit them to the next victim they feast on, often a person.
It is estimated that in Western Europe (where the animal & human trials discussed here are being conducted) up to half of all ticks carry the bacteria.
Although the early symptoms of the illness are quite mild, if left untreated, it can result in serious damage to the skin, the joints, the heart and the nervous system, and effective therapy becomes very difficult.
Infection Limited to Skin Around Bite at First
Studies have shown that B burgdorferi tends to remain in the skin around the bite, within an area just a few centimeters in diameter, for 2 days or more, so that it “can even be removed by surgical means.”
A team of researchers led by the veterinary bacteriologist Professor Reinhard Straubinger at Ludwig-Maximilians University in Munich has now shown, in an animal model, that application of a gel containing the antibiotic azithromycin to the site of the bite rapidly terminates the infection.
(See the full text of their interesting article here – “Evaluation of the preventive capacities of a topically applied azithromycin formulation against Lyme borreliosis in a murine model,” Journal of Antimicrobial Chemotherapy, Dec 2011)
They chose azithromycin because it has a lower MIC for B burgdorferi (less is required), fewer adverse effects when compared with doxycycline, shows excellent tissue penetration, remaining much longer where applied, and “doesn’t leak into the circulation when applied locally onto the skin.”
Phase III (Human) Trial Underway
The efficacy of this local antibiotic therapy for the treatment of borreliosis in humans is now being tested in a Phase III clinical trial (by definition a large rigorously controlled trial in humans of a treatment or drug that has been shown to be efficacious with tolerable side effects; in the US generally receives formal FDA approval if the trial is successful).
In the meantime, though, patients must still undergo antibiotic treatment for several weeks and, in many cases, the drug must be administered intravenously – which is distressing not only for children.
Furthermore, treatment measures are often initiated on suspicion, because the bacteria are not detectable in the blood soon after one has been bitten by an infected tick.
“Our approach simply involves applying a transparent, self-adhesive plaster to the site of the wound,” says Straubinger. “Because the plaster contains very little antibiotic, the effects are localized and side-effects are negligible.”
Source: Journal of Antimicrobial Chemotherapy, Ludwig-Maximilians University Munich press release, Sep 15, 2011