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WSV18-0316
SVA INFECTIOUS DISEASES
FLEAS AND FLEA-BORNE DISEASES UPDATED
S. Shin1
1Chonnam National University College of Veterinary Medicine, Parasitology, Gwangju, Republic of Korea
Introduction
Carpets and companion animals are frequently seen in modern living rooms. However, the combination of the two gives a perfect condition for flea infestation in dogs and cats in a residential house. It is important to control flea infestation in companion animals and larval stages on the ground to prevent severe allergic dermatitis
and the transmission of flea-borne pathogens that can cause serious disease in animals and/or in humans. Understanding the biology and ecology of flea is critical, as it affects what strategies will be effective to control flea infestation. A wide range of flea control products
is available in the form of sprays, spot-ons, collars, oral tablets and injections. Used correctly and understanding the mechanism of kill will ensure safe and highly effective flea control.
Flea biology
Adult fleas live on animals. Unless they’re dislodged through grooming, fleas become permanent residents
of their acquired host. Out of over 2500 distinct species in Siphonaptera, the two species of most importance for veterinary practitioners are the cat flea Ctenocephalides felis and the dog flea C. canis. Fleas have a shiny, glossy appearance because they have strongly sclerotized
and chitinized bodies. Adults are laterally flattened, appearing as if they’ve been compressed side-to-side. The flattened body is an adaption which helps them move forward through host fur. Fleas, unlike most other insects, don’t have wings [1].
Ctenocephalides felis felis is the most common species associated with domestic dogs and cats in the USA and most parts of the world. The term “cat flea”
is the common name of C. felis and doesn’t refer to
all fleas recovered from cats. The species C. felis felis is characterised by an acutely angled frons and head appears ‘pointier’ than C. canis [2].
Unlike larval stages on the ground, both male and female adult fleas rely exclusively on host blood for living, so the mouth parts of a flea are specialized for blood feeding. While imbibing blood, salivary ducts open to introduce anticoagulant saliva to the wound. Flea legs are long
and well-adapted for jumping. The hind legs are much longer than the others, and are connected to specialized internal structures for leaping. A highly elastic protein called resilin enables their incredible jumps, not leg muscles [3].
Adult fleas imbibe much more blood than they can
use. As a result, fleas produce large amounts of feces, consisting largely of undigested blood. Feces from
adult fleas which is flea dirt, is the primary food source
of flea larvae[4]. A bit weird, but somewhere in nature close to our living, mother’s poop is baby’s food, and is bloody red instead of milky white. Fleas excrete feces
in two different forms: Spherules and coils. Spherules
are round and 0.07-0.25 mm in size. They can also be diarrheic. Coils are long with an average length of 0.84 mm. Newly emerged adults produce spherules. By the tenth day of feeding, their poop is mostly in the form of coils. Finding flea dirt on a dog or cat is one of the best ways to diagnose an infestation. If it’s truly flea feces, the black speck will smear red or dark yellow when rubbed on a wet paper towel. Flea dirt dries in irregular shapes and gets embedded into pet fur. The dry blood dislodges when animals scratch and groom themselves. As a result, it’s most common to find feces (and eggs) in areas where pets commonly rest and groom. Coils contain 33% more protein than spherules. The spherules are thought to be preferred by young larvae, while the protein-rich coils are more suitable for 3rd instars.
Adult fleas always stay on their host and females lay eggs directly on their host after mating with male fleas. Roughly one flea egg is produced per hour. The eggs are initially wet and sticky, but they dry quickly and become non-adherent. Around 60% of eggs fall from the host within two hours of being laid. Flea eggs measure 0.5 mm in length, and 0.3 mm in width. To survive, flea eggs must fall onto substrates with a warm, humid microclimate, such as carpeting. If the microenvironment is too dry, eggs willshrink and die. Flea eggs develop rapidly in warm, humid environments. They’ll hatch within one and half days when conditions are optimal. Ideal conditions occur at temperatures near 89.6°F (32°C), and humidity between 75-92%. A relative humidity below 50% is often lethal while 80% of flea eggs survive when relative humidity exceeds 50%. In homes, it takes 2 to 3 days before flea eggs hatch. Most eggs and larvae live in carpeting because the temperature and humidity are well secured. The microclimate within the carpet fibers
is near ideal for developing fleas. A sharp spine projects from the front of the head. It helps a larva rupture its egg shell and hatch. The egg burster spine is only found on first instars. It’s lost in the first molt. Newly hatched flea larvae are 2 mm long, growing to a final length of 5 mm. The larvae resemble worms or maggots. Dog or cat flea larvae develop through three stages, taking the form of 1st, 2nd, and 3rd instars. They molt once between each stage. Dried blood feces from adult fleas is the primary food source of larvae. As a larva feeds on flea dirt, its gut turns a dark red to purple color.
Your Singapore, the Tropical Garden City
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