External parasites on dogs: fleas and ticks

Fleas:

Fleas are small (1/16 to 1/8-inch long), agile, usually dark colored (e.g. the reddish-brown of the cat flea), wingless insects with tube-like mouthparts adapted to feeding on the blood of their hosts. Their bodies are laterally compressed, (i.e., flattened side to side) permitting easy movement through the hairs (or feathers etc.) on the host's body. Their legs are long, the hind pair well adapted for jumping (vertically up to seven inches); horizontally thirteen inches - around 200 times their own body length, making the flea the best jumper out of all animals (in comparison to body size). The flea body is hard, polished, and covered with many hairs and short spines directed backward, allowing the flea a smooth passage through the hairs of its host. Its tough body is able to withstand great pressure, likely an adaptation to survive scratching etc. Even hard squeezing between the fingers is normally insufficient to kill the flea; it may be necessary to crush them between the fingernails or roll them between the fingers.

Life cycle and habitat
Fleas go through the four life cycle stages of embryo, larva, pupa and imago (adult). The flea life cycle begins when the female lays after feeding. Adult fleas must feed on blood before they can become capable of reproduction. Eggs are laid in batches of up to 20 or so, usually on the host itself, which easily roll onto the ground. As such, areas where the host rests and sleeps become one of the primary habitats of eggs and developing fleas. The eggs take around two days to two weeks to hatch.
Flea larvae emerge from the eggs to feed on any available organic material such as dead insects, feces and vegetable matter. They are blind and avoid sunlight, keeping to dark places like sand, cracks and crevices, and bedding. Given an adequate supply of food, larvae should pupate within 1-2 weeks. After going through three larval stages they spin a silken cocoon. After another week or two the adult flea is fully developed and ready to emerge from the cocoon. They may however remain resting during this period until they receive a signal that a host is near - vibrations (including sound), heat and carbon dioxide are all stimuli indicating the probable presence of a host. Fleas are known to over winter in the larval or pupal stages.
Once the flea reaches adulthood its primary goal is to find blood - adult fleas must feed on blood in order to reproduce. Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae and 5 percent adults. Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are favorable. Female fleas can lay 500 or more eggs over their life, allowing for phenomenal growth rates.

Flea Treatments
The fleas, their larvae, or their eggs can be controlled with insecticides. Lufenuron and fipronil are popular veterinary preparation that attacks the larval flea's ability to produce chitin. Flea medicines need to be used with care as many, especially the acetylcholinesterase inhibitors, also affect mammals. Popular brands include Bayer Advantage, Advantix, and Frontline.

Fleas in the home
Spot-on insecticide, such as Advantage, Frontline or Revolution will kill the fleas on the pet and in turn the pet itself will be a roving flea trap and mop up newly hatched fleas. The environment ought to be treated with a fogger or spray insecticide containing an insect growth regulator, such as pyriproxyfen or methoprene to kill eggs and pupae, which are quite resistant against insecticides. Frequent vacuuming is also helpful, but you must immediately dispose of the vacuum bag afterwards.
Flea collars, flea powders and flea shampoos are not recommended. Many strains of insects have become resistant against that class of compounds, and they display an unacceptably high level of toxicity against mammals.
Diatomaceous earth can also be used as an effective home flea treatment in lieu of acetylcholinesterase inhibitory treatments or insecticides which carry with them a risk of poisoning for both humans and animals. Diatomaceous earth absorbs lipids from the cuticle, the waxy outer layer of insects' exoskeletons, causing them to dehydrate and can be purchased at most gardening suppliers or online. It can then be evenly distributed around the house (especially in corners and near furniture) with any type of shaker (salt shaker, spice shaker, etc.) and then vacuumed away after about 7 days. Diatomaceous earth also has the added benefit of killing many other types of insects that might be residing in your house.

Ticks:

Tick is the common name for the small arachnids that, along with other mites, constitute the order Acarina. Ticks are ectoparasites (external parasites), living by hematophagy on the blood of mammals, birds, and occasionally reptiles and amphibians. Ticks are important vectors of a number of diseases, including Lyme disease.
Tick bites look like mosquito bites, but can also sometimes bruise or resemble a bullseye.

Habitats and behaviors
Ticks are blood-feeding parasites that are often found in tall grass and shrubs where they will wait to attach to a passing host. Physical contact is the only method of transportation for ticks. Ticks do not jump or fly, although they may drop from their perch and fall onto a host.
Changes in temperature and day length are some of the factors signaling a tick to seek a host. Ticks can detect heat emitted or carbon dioxide respired from a nearby host. They will generally drop off the animal when full, but this may take several days. Ticks have a harpoon-like structure in their mouth area, known as a hypostome, that allows them to anchor themselves firmly in place while feeding. The hypostome has a series of barbs angled back, which is why they are so difficult to remove once they have penetrated a host.

Removal
To remove a tick use a small set of tweezers: grab the head, pulling slowly and steadily. There are a number of manufacturers that have produced tweezers specifically for tick removal. Crushing or irritating the tick (by heat or chemicals) should be avoided, because these methods may cause it to regurgitate its stomach contents into the skin, increasing the possibility of infection of the host. Tiny larval ticks can usually be removed by carefully scraping with a fingernail. Lyme disease found in deer ticks cannot be transmitted once the body is removed even if the mouthparts break off and are still in the skin. Prompt removal is important; infection generally takes an extended period of time, over 24 hours for Lyme disease.
An effective method involves carving the end of a small stick into a flat blade resembling a screwdriver, but with a small notch in the end. This implement is especially useful removing ticks from dogs.