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Abstract
A study was performed to determine the life cycle of Rickettsia felis, a novel bacterium associated with cat fleas (Ctenocephalides felis Bouche). Cat flea populations maintain R. felis in successive generations by efficient transovarial transmission. Transovarial transmission was demonstrated in our study up to 12 generations. The mean infection rate for the progeny of fleas maintained on both cats and an artificial membrane system were comparable (64.3% and 58% respectively).
Cats with no prior exposure to fleas were exposed to fleas infected with Rickettsia felis and monitored monthly for seroconversion via IFA. Blood samples were assayed for the presence of R. felis via PCR. Thirteen of 16 cats seroconverted by 4 months post-exposure to fleas infected with R. felis. R. felis DNA was detected in five of 16 cat blood samples.
A total of 266 cats were assayed for immune response to Rickettsia typhi-felis from March-August 1995 and March-September 1996. Twenty-four cases (9%) were confirmed via indirect immunofluorescent antibody assay. None of the fleas removed from 46 of the cats tested positive by PCR analysis. In two similar surveys taken at animal shelters in Alexandria and Lafayette Louisiana, we found a seropositivity rate of 12.5% and 11%, respectively, during August 1996.
When comparing the egg and feces production for the three strains of fleas fed in vitro on bovine blood, we found that the LSUSG strain did not produce as many eggs nor as much feces. When the same comparisons were made feeding the flea strains on cats, there were no differences in the egg production between LSUSG and Heska strain fleas and LSUSG and Lab strain fleas. There was a difference between the feces production of Heska and the LSUSG strain fleas fed on cats. The LSUSG strain produced 32% less feces per egg than the Heska flea strain.
In the cross-mating studies we found no statistical difference between the egg production of the Lab strain or Heska strain females when mated to LSUSG males. We also found that the Heska strain fleas had a lower adult emergence rate than the LSUSG strain.
