Controlling Vector-borne Diseases
Vector-borne diseases have taken on increasing importance in both veterinary and human medicine as new diseases continue to
become recognized and established, vector populations spread, and the potential for transmission of infectious diseases between
people and pets is increasingly understood. Arthropod vectors, particularly fleas, play a critical role in both creating
and maintaining a source of these infections in pet cats as well as allowing transmission to cats and people. Accordingly,
preventing transmission to and disease in cats and limiting the risk of zoonotic infections relies on the implementation of
safe, effective flea control programs in all cats. Fortunately, highly effective flea control products are widely available.
The risk of transmission of several vector-borne agents to companion animals and people further justifies advocating the routine
use residual insecticides in veterinary practice.
Pathogens transmitted by fleas
Perhaps the most common and best known flea-transmitted parasitic disease of cats is Dipylidium caninum, the flea tapeworm.
Cats become infected with D. caninum when they ingest an infected flea intermediate host during grooming. Although these
tapeworms are not particularly pathogenic, they are aesthetically unpleasant and potentially zoonotic. Currently available
D. caninum treatments such as praziquantel and epsiprantel are 100% effective in eliminating these tapeworms with a single
treatment. However, cats that are treated but then returned to a flea-infested environment are almost certain to acquire
infection again and will begin shedding proglottids in 2-3 weeks. Preventing post-treatment re-infection with D. caninum
requires simultaneously instituting a highly-effective flea control program for all pets in the household. Because time is
required for any flea control program to eliminate a home infestation, a second dose of cestocidal treatment is usually dispensed
with instructions to re-administer in two weeks time. This second treatment targets the additional tapeworms that will likely
be acquired from the environment while the client also works to control the flea infestation.
Another common infection of cats that fleas are central to maintaining is Bartonella henselae, the causative agent of cat
scratch disease. Fleas transmit B. henselae from infected to na´ve cats, and kittens are particularly susceptible to developing
high levels of bacteremia. Although B. henselae infections are usually not symptomatic in cats, when the organism is transmitted
to a person through a bite or a scratch wound, severe, febrile disease associated with lymphadenopathy and general malaise
can result. Preventing B. henselae infection in cats and subsequent transmission to people requires placing all kittens and
cats on routine, effective, year-round flea control programs. Because kittens are prone to both developing bacteremia and
inflicting the minor bites and scratches that allows transmission to people, flea control should be instituted in all kittens
at the earliest possible opportunity.
Rickettsia felis is a relatively new species of pathogenic rickettsia isolated from Ctenocephalides felis fleas. An obligate
intracellular organism, R. felis is a member of the spotted fever group rickettsia and has been identified in patients that
were originally diagnosed with murine typhus. Because it is passed through fleas transovarially, a population of fleas may
harbor the bacteria for generations. When bacteria are deposited near the bite wound of the flea, infection can result and
may lead to development of a febrile syndrome in people characterized by rash, headache, vomiting, and profound lethargy.
Because fleas are considered both vector and primary reservoir, keeping cats flea-free is key to preventing disease in people.