Friday, July 6, 2012

Dogs With Sarcoptic Mange, Signs and Treatment of Sarcoptic Mange

Sarcoptic mange mites is a parasitic disease common in dogs and cats. It is essential to know the origin and development of this disease to treat and prevent it. Many parasitic infections may be responsible for the appearance of skin disorders in dogs. Among them are the most common, namely demodicosis and sarcoptic mange.

Scabies is an infestation of the dog's skin by a parasitic mite, the canis variety of Sarcoptes scabiei . It is responsible for the onset of pruritus (i.e. itch).

The mite is microscopic and are localized in the skin. Adults are between 0.2 and 0.4 micrometers, are oval shaped and have four pairs of short legs. They are easily recognizable under the microscope. Their life cycle in the dog's skin lasts three to four weeks. After burrowing into the surface of the skin, the males and females mate.

The impregnated female mites burrows a cavern/trench into the skin in which she lays a great many eggs. After 3 to 10 days the eggs hatch into wormlike larvae to. These rise to the surface of the skin. Either they will form a cocoon, or they wander in search of food. They moult into nymphs and then into adults. They are then capable of a starting new reproductive cycle (mating).

Scratching and licking of the area caused by the irritation of the parasite digging/burrowing. The female is then often exposed to trauma and desiccation, and dies. However, her eggs and faeces (droppings) will remain inside the skin and continues to be itchy and therefore there is the appearance of rapidly crusted excoriations.

The parasite causes mange in two ways:

1. By mechanical action. The female digs her trench which irritates the skin
2. By generating an allergic reaction.

Saliva from your dog, secretory products and excretion (from the mites), moulting fluids and proteins (denatured by the dog's digestion of Sarcoptes) are substances that induce the infested host to an abnormal reaction of so-called "hyper-sensitivity".

These substances actually cause abnormal reactions in the body, causing the release of some mediators, directly responsible for the worsening of clinical signs. In other words, your pets body fights back and makes it worse.

Sarcoptic mange is highly contagious and transmission is usually through contact with infected animals. Transmission can also occur via the equipment used on animals. Thus, brushes and grooming equipment can be a source of infestation. Moreover Sarcoptes scabiei var. canis can survive 24 to 36 hours in the external medium at a temperature of 20 ° C and up to 19 days if the temperature is low (10° C) and the relative humidity high (97%). Transport in cages or use of contaminated boxes or kennels not disinfected or treated with acaricides (insect killer) may also be responsible for contagion.

The parasite is attracted to the host by many stimuli including body temperature. The Sarcoptes are considered relatively specific to dogs. This type of mange may cause an itchiness in humans because the mites may be attracted to the heat, but 99 times out of a 100 the mites will hop off the humans back onto the dog, because this species of parasite likes the taste of dog. You should probably inform your doctor though, as this type of rash may bring-on the human form of scabies. It is a little like putting up “to-rent” signs on your skin. The dog mange digs out the holes and then human scabies come by and stay in them.

The mites are often distributed preferentially in areas without hair and with thin skin. They therefore first colonize the face, the skin area above the folds of the elbows, hocks and ventral parts of the abdomen and thorax. If left untreated the disease can spread to the whole body. The disease can become very painful and in most cases deadly if left to spread.

The main symptoms are pruritus (itch). Clinical lesions include lesions with excoriations and alopecia (hair loss), secondary to biting, scratching and licking.

Buttons scabies are sometimes present but masked by the excoriations. These characteristic small bumps of skin are red and firm and usually topped with a thin crust. These lesions represent the entry point of the parasite into the skin.

Typically, if you rub the free edge of the ear of a mangy dog, it triggers a reflex otopodal, (i.e. a movement of the corresponding hind-limb). This event is not systematic when there are scabies. This is a sign of orientation rather than a true diagnostic aid. Diagnosis is made by observing the mites under a microscope after a parasitic scraping of the skin around the affected area. Unfortunately Sarcoptes (the mites) are very few in the skin and it is hard to find samples. We must scrape many times (sometimes 10 to 20 scrapings are necessary) and deep. In 50% of cases, there is no evidence of parasite. Therefore, if the clinical suspicion of scabies is strong, and even if the scrapings are negative, the vet will practice a therapeutic trial. If the problem recedes, then mites are diagnosed.


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