The Cat Area 9 : Ctenocephalides felis

Good day colleagues and friends today we will talk about the most common ectoparasite in cats, yes we are talking about CTENOCEPHALIDES FELIS, a flea that gives all of us veterinarians headaches when we are at the consultation room, because they are stubborn and they jump not only to other patients but also to us veterinarians and owners.

Distribution

But before we get started, it is important to know where this ectoparasite is most common at.

 Cat fleas are commonly found on both cats and dogs in North America, while dog fleas are found in Europe. The two species are distinguished by a slight morphological difference which is detectable only under high magnification. Although it exists worldwide, the cat flea is most commonly found in the United States and Mexico, in and around homes with pets.

Life and Cycle

The Ctenocephalides Felis or cat fleas are small pests measuring about 2mm in length. They are dark brown or reddish in color, typically wingless, but capable of jumping long distances. Their laterally compressed bodies are covered with hair. They have very strong hind legs which enable them to jump from one host to another. In the adult stage, the Ctenocephalides Felis also have mouthparts that allow them to suck blood from their host.

Now let's review this flea's stages and life cycle. Under optimal conditions, a cat flea can complete its entire lifecycle in just two weeks. In adverse conditions, the lifecycle of the cat flea can take upwards of one year. Cat fleas like warm, humid environments, so if they make it into your nice, warm home they can be hard to banish.

Cat fleas have four distinct stages in their lifecycle: eggs, larvae, pupae, and adult.  This cycle usually lasts 30 to 75 days, yet may vary due to external factors, such as temperature and humidity.

Adults: Adults are stimulated to emerge by vibration or an increase in carbon dioxide. They are about one to three mm in size, reddish-brown to black in color, wingless, and are laterally compressed. They possess powerful hind legs which allow them running and jumping through hair, fur, and feathers. Adult cat fleas require fresh blood to produce eggs. This is the only stage in the cat flea life cycle when the fleas live on the pet. Adults live from 4 to 25 days.

Adults feed directly from capillaries. Female fleas can ingest an average of 13.6 µl of blood daily, about 15 times their body weight.

Eggs: Cat flea eggs are laid at the rate of up to one egg per hour, and 20 to 50 eggs per day, which hatch in 2 to 5 days. They are oval, smooth, and about 0.5 mm in size. Due to their dry, smooth surface, the eggs easily fall out of the animal's hair. Though otherwise visible, the white eggs are nearly impossible to see against surfaces such as carpet, bedding, and lawn. It is here where the eggs will remain until the larvae emerge.

Larvae: Within two days of oviposition, wormlike larvae hatch from the eggs. They range from 1.5 to 5 mm in length. This stage lasts 5- 15 days. Larvae lack eyes, legs, are covered with few hairs, and possess dark guts, visible through their thin translucent exoskeleton. Larvae feed on almost any organic debris in the floor covering, but their main dietary component is dried adult cat flea fecal matter.

*Adult flea feces, also known as "flea dirt", consist of relatively undigested blood which dries and falls from the pet to serve as food for the newly hatched larvae. The larvae prefer to develop in areas protected from rainfall, irrigation, and sunlight, where the relative humidity is at least 75 percent and the temperature is 70 to 90°F.

Pupae: Before becoming adults, the larvae spin silk cocoons in which they will develop. Because of the sticky outer surface of the cocoons, dirt and debris are attracted to them and provide camouflage. The pupae remain in the cocoons until they have fully developed into adult fleas.

Signs of cat fleas infestation, control and treatment.

Cat fleas love the warm, moist, safe haven that’s provided in a cat’s furry coat. Two of the main ways to tell if fleas are making a meal out of our cat patients is to take note of whether they are scratching or biting their skin and fur.

Fleas regurgitate digestive juices onto the skin of a bite site while they suck blood from their prey, and sometimes cats and dogs can have serious allergies to this juice. This allergy is called fleabite allergic dermatitis and can be developed over the course of a dog, cat, or human’s lifetime.

Cats that are allergic to flea bites (flea allergy dermatitis) will exhibit excessive grooming and scratching from just a single bite. It’s also characterized by intense itching, hair loss, reddening of the skin, and secondary infections. The reaction and itching can persist for up to five days.

On the Examination we ought to check the skin around the base of its tail or under the armpits for tiny, moving black dots. There's another way we can tell if our patient has fleas by using a flea comb to comb our patient  and look for flea “dirt” (the feces of fleas) which can alert us to an infestation even without seeing live fleas. The fleas will get caught at the base of the comb’s teeth.

We most advise the owner to monitor the patient for scratching and biting on a regular basis. 

If we find any we must advise the owners to treat the patient as much as the home, indoors and outdoors.

When we advise the owner to treat the home, we should make emphasis on how to do so, inside they must vacuum the floor and carpets (specially carpets), and on the yards we can use pesticides that are garden friendly,

Some of the products we can recommend our patient's owners are: 

To treat the outdoors, pyrethroids may be sprayed in dry shaded areas which the animal frequents, as well as insect growth regulators such as pyriproxyfen and fenoxycarb, which are the most effective outdoor treatments. Methoprene is also commonly used outdoors, but is not stable in sunlight. Since larvae prefer shaded, dry areas, spraying the entire yard is wasteful and irresponsible. For outdoor areas which are difficult to treat (under decks), pet access should be restricted. Outdoor treatment is primarily used in severe cases of flea infestation and may not be necessary if fleas are controlled on the pet and in the home.

 Advise the owners not to leave their pets on the outside at least 4 hrs after using pesticides outside.

Now Let's talk about the patients treatment. By own experience, and other colleagues won't let me lie on this, but fleas and ticks control collars are simply not good at all, for some cats it won't matter, but the majority of the feline patients show skin irritation on the neck, some develop allergies to the chemicals used in those collars, some cats have even been intoxicated because of the owners don't place the collar tight enough or because the cat it's just to restless that start biting and chewing on the collar. The safest ways to treat a cat for ctenocephalides felis will always be fipronil or imidacloprid topical treatments. 

When using a pesticide, always consult the label. Insect growth regulators (IGR) and insect development inhibitors (IDI), administered as a daily or monthly dose, will disrupt egg and larval development but not kill adult fleas. Methoprene and pyriproxyfen are active ingredients of IGRs  and are safe to use on our patients, but also easy on the owners pockets.

We also have other options, as many of us know we also can prescribe shampoos. Insecticidal shampoos contain certain pesticides such as pyrethrins, carbamates, and citrus peel derivatives. Pennyroyal oil, another natural products, are also available in shampoos. However, pulegone, the active ingredient in the oil has dose related toxicity to mammals and may induce lethargy, vomiting, diarrhea, nose bleeds, seizures and possibly death due to liver failure.

Now, it is also important to treat the patient's wounds done by the flea bites, because as we know, fleas can transmit bacteria that may result in an infection, therefore we ought to treat the skin of our patients also with antibiotics, our best option of course is Neosporin antibacterial ointment or by mouth. In case of severe FDA (flea dermatitis allergy), we can also prescribe corticosteroids, personally, I would definitely rather to leave those as a last resource, not only because it may be hard to discontinue them, but also because it could cause undesirable side effects if the condition it's chronic or becomes chronic.

Associated diseases

And just like ticks, fleas also can bring diseases to our patients along with them, some of those diseases are:

Flea allergy dermatitis (FAD) The cat flea is primarily responsible for flea allergy dermatitis (FAD) in both dogs and cats. FAD is a hyper sensitization to antigenic components contained in the saliva of fleas. Cats and dogs that have flea allergies will bite at the base of their tail and rump frequently. Animal become nervous and sleepless, sometimes, they vocalize (yelp or meow) sharply from a single flea bite. Even a few fleas can lead to prolonged itching that causes animal to groom extensively sometimes biting and scratching their skin, which can result in painful lesions.

Dog tapeworm Cat fleas are the primary intermediate host of Dipylidium caninum(cucumber tapeworm or the double-pore tapeworm), the common intestinal cestode of dogs and cats that also rarely occurs in children after accidental ingestion of infected flea. 

Murine typhus Cat fleas are able to transmit murine typhus, also called flea-borne typhus or endemic typhus, a rickettsial disease caused by the organism Rickettsia typhi, which usually is associated with rat fleas (Xenopsylla cheopis).

Flea-borne spotted fever Cat fleas are most common vectors of Rickettsia felis, relatively recently described pathogen, causative agent of flea-borne spotted fever (also called cat flea typhus). In 1994, the first human case of infection was reported in United States. Because the disease has similar clinical manifestation as murine typhus (including high fever, myalgia, and rash) and other febrile illnesses such as dengue, the infection in humans is likely underestimated.

Cat scratch disease (CSD) Cat fleas have recently been implicated in the transmission of Bartonella henselae, the etiologic agent of cat scratch disease (CSD). In immunocompetent humans this infectious disease usually is not serious and associated with papule or blister at the site of injury (scratch or bite) and malaise. Cat scratch disease is a common cause of chronic lymph node swelling (lymphadenopathy) in children. It has been suggested that Bartonella spp. may be responsible for numerous chronic inflammatory conditions of the cat. It was shown that as many as 58% of stray cats can be Bartonella spp. carriers and up to 90% of fleas are infected. The prevalence of the infection is much lower in pet cats (~3%).

Cat anemia Over 50% of cat fleas collected from stray cats were shown to be infected with Mycoplasma haemominutum or Mycoplasma haemofelis associated with infections in cats, which can range from subclinical and subtle anemia to severe hemolytic anemia.

Plague Cat flea was shown to be a competent vector for transmission of plague(causative agent Yersinia pestis). Although not as efficient as rat fleas (Xenopsylla cheopis) C. felis is the most common flea in human habitations in many African countries and threat posed by the ectoparasite cannot be dismissed. Plague transmission is carried out by infected fleas that become "blocked" - a clot of microorganisms hinders flea's feeding forcing the flea to regurgitate overwhelming doses of the pathogen into the host and to seek the next available host.

We hope you like this post and most important that you find it useful. On our next post we will talk about the products that we can use for flea management and their mechanisms.

Cheers and happy holidays!

MVZ Carolina Pruneda