Fleas: Dirty Secrets, Disturbing Information, and Things You Don’t Want To Know

Plus a surefire way to kill them dead!

Fleas. What are they?

What are these wily, disgusting creatures we call fleas? They are small, wingless insects – external parasites – who sustain themselves through hematophage, a process of sucking the blood of mammals and birds.

Genetic evidence indicates they evolved from the flightless insect family Boreidae (of the Siphonapteral order) and are related to scorpionflies, which are winged insects with good eyesight.

About 160 million years ago the common ancestor split off into many lineages. Today there are about 2,000 species and subspecies classified largely by their specific parasitic niche, most flightless and sightless.

What to look for

A flea can range in size from about 1/16 to 1/8 inch (1 to 3.5 cm). They are dark or reddish-brown in color, nimble, and suitably adapted with piercing, tubular mandible-like mouths for biting and consuming their host’s blood.

Their bodies are hard and compressed side-to-side with smooth hairs running downward to allow easy maneuverability through their host’s fur or feathers. Unfortunately, their flat physique can survive the extreme pressure of a dog biting or scratching at an infested area.

Their acrobatic agility is legendary. Their legs are long and the hind pair well adapted for jumping. They can jump vertically up to 7 inches (18 cm) and horizontally about 13 inches (33 cm). This distance is about 200 times their body length, making them the world’s best jumpers of all critters in comparison to body size.

Meet the family

These insects go through the four life cycle stages of embryo (egg), larva, pupa, and imago (adult). Mature insects must feed on blood before they are capable of reproducing.

The life cycle begins when the female lays her tiny white oval-shaped eggs, usually in batches of about 20, directly on the host. Many eggs drop to the ground in areas where the host lives and sleeps. Within the two days to two weeks it takes for the eggs to hatch, new populations emerge on the host and in the areas where eggs have fallen.

Hungry and blind the pale, worm-like larvae emerge from the eggs in search of organic matter to feed on including feces (most appetizing is the feces left behind by adults, which is rich in blood proteins and lipids) and plant life. If food supplies are sufficient the larvae should pupate in one to two weeks. Like a caterpillar they spin a silken cocoon and, after another week or two, the adult is fully developed and ready to emerge.

The primary mission of a young adult is to find blood. A blood donor is necessary not only for survival but also for reproduction. They are able to sense vibrations (sound), heat and carbon dioxide, indicating that a host is nearby. While a young adult must find food within a week of emerging from the cocoon, once fed it can survive for two months to one year between meals.

At any given time the distribution of life stages in the family is about 50% eggs, 35% larvae, 10% pupae and 5% adults. Females can lay more than 500 eggs in a lifetime. Just because your dog or cat stops scratching itself doesn’t mean the pests have moved on. Under favorable conditions the life cycle of a single family can extend for many, many months. If untreated, the family can live on indefinitely.

My dog has cat fleas

One of the most plentiful and far-reaching throughout the world is the cat flea (Ctenocephalides felis). While their host of choice is the domestic cat, they are equal-opportunity pests and the primary external parasite infesting dogs in most parts of the world.

Successful proliferation of the cat flea is due in part to its clever incubation strategy. The female lays her eggs on the host, as usual. However, by natural design, the dry eggs slip easily through the host’s fur or feathers and fall onto bedding, carpet, sofas and chairs. Hatched larvae move in the opposite direction of the light (negative phototaxis), meaning that their survival mechanism includes hiding among folds, cracks and crevices. Left untreated, the entire home and contents can become an infestation in short order.

To make matters worse, the pre-emergent cat flea normally waits as a young adult until the presence of a potential host is detected by warmth, vibration or carbon dioxide discharge. Within seconds of finding a target host the newly emergent adult jumps aboard and begins feeding within minutes.

Adult dogs and cats can normally tolerate a few of these parasites by responding with the familiar scratching, biting and licking. The problem comes when the animal becomes allergic to chemicals in the flea’s saliva. An itchy skin disease called flea allergy dermatitis (FAD) is the usual result.

Dogs with FAD often show inflammation of the upper layers of skin along the hind quarters. Cats with FAD can develop various skin diseases, infections and self-inflicted hair loss (alopecia) from excessive grooming. Small animals with widespread infestation can suffer anemia due to excessive blood loss. Finally, the cat flea is responsible for disease transmission such as typhoid fever plus the spread of other parasites such as tapeworms.

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