tetracycline and Dirofilariasis

The discovery of Wolbachia, a bacterial endosymbiont that occurs in the filarial parasite and its sensitivity to tetracycline, has fostered a new initiative in the development of suitable antifilarial drugs. The present study is an attempt to investigate whether adding acaciasides (saponins from Acacia auriculiformis) to the standard dose of tetracycline would further improve the efficacy of tetracycline treatment against Dirofilaria immitis microfilariae in vivo. Treatment of microfilaremic adult dogs (body weight range 8-12 kg) with tetracycline at 10 mg/kg/day for 40 days resulted in 72% and 83% reduction in mf count on days 15 and 30, respectively, and the maximum reduction in mf count (91%) was achieved on day 75 post-treatment. However, treatment with tetracycline (10 mg/kg/day for 40 days) followed by acaciasides (10 mg/kg/day for 7 days) resulted in almost 100% clearance of mf at a faster rate on day 45 post-treatment and ensured long-term (until 4 months post-treatment) protection against microfilaremia. Data from polymerase chain reaction analysis reveals that compared to untreated dogs, in treated dogs, there was marked reduction in Wolbachia specific wsp markers in fast depleting mf population. The present data indicate that prior tetracycline treatment enhances microfilaricidal activity of saponins. This effect may be additive or synergistic as the worms are weakened by Wolbachia depletion, and these weakened microfilariae are possibly killed by the saponins.

Topics: Animals; Dirofilaria immitis; Dirofilariasis; Dog Diseases; Dogs; Drug Synergism; Female; Filaricides; Male; Saponins; Tetracycline; Treatment Outcome; Triterpenes

Filarial nematodes harbour intracellular symbiotic bacteria belonging to the genus Wolbachia. Wolbachia is thought to play an important role in the biology of the nematode. Moreover, Wolbachia appears to be involved in the immunopathogenesis of filariasis and in the onset of the side-effects of antifilarial therapy. Investigations in these research areas require reliable methods to quantify Wolbachia both in nematodes and in vertebrate tissues. To this purpose, we designed a quantitative real-time PCR targeted on the ftsZ gene of the Wolbachia of Brugia pahangi, a model filarial species maintained in gerbils. The method was applied to quantify Wolbachia in Brugia pahangi, from animals with or without tetracycline treatment. Our results show that tetracycline treatment leads to dramatic reduction or clearance of Wolbachia from the nematode. Results obtained from different replicates were reproducible and the method appeared very sensitive compared to other PCR protocols for Wolbachia detection. Real-time PCR is thus an appropriate method for investigations on the biological role of Wolbachia and on the implication of these bacteria in the pathogenesis of filariasis. With slight modifications of the primers and probe, the protocol we have developed could be applied in studies of the human pathogen Brugia malayi and on the model filarial species Litomosoides sigmodontis.

Topics: Animals; Bacterial Proteins; Brugia pahangi; Computer Systems; Cytoskeletal Proteins; Dirofilaria immitis; Dirofilariasis; DNA, Bacterial; Dog Diseases; Dogs; Female; Gerbillinae; Male; Polymerase Chain Reaction; Reproducibility of Results; Symbiosis; Tetracycline; Wolbachia

The distribution and phylogeny of Wolbachia in filarial species suggests that these endosymbiotic bacteria may be important in the biology of their filarial hosts. An experiment to falsify this hypothesis would be to treat filarial worms with antibiotics which are active against intracellular bacteria. Indeed, it has already been shown that tetracycline treatment inhibits development in a model filarial species (Brugia pahangi) at different stages of the life cycle, in both mosquito and mammalian hosts. Here we discuss these previous data and present new results on the effect of tetracycline on the embryogenesis of the canine filaria Dirofilaria immitis.

Topics: Animals; Anti-Bacterial Agents; Dirofilaria immitis; Dirofilariasis; Dog Diseases; Dogs; Female; Morphogenesis; Rickettsia; Symbiosis; Tetracycline