Creepy crawlies in dogs and cats: how to find and treat them

Ectoparasites are a common cause of pruritus in dogs and cats. Despite there being many ectoparasiticides available to treat these conditions they remain a problem in general practice. In this article we will discuss the clinical signs commonly seen with ectoparasites in dogs and cats, alongside how to diagnose and treat these cases.

The main type of flea causing skin disease in dogs and cats is the cat flea (Ctenocephalides felis). Adult cat fleas are obligate parasites and can only survive for short periods off the host once they have fed. It is the adult flea feeding on the host that causes the clinical signs noted in flea allergy. It is presumed that allergens are present in the injected saliva of the flea and it is this that causes the clinical signs. It should alo be remembered that some animals can have an infestation of fleas without having flea allergy.

There are four main stages to the flea life cycle: egg, larva, pupa and adult flea (Figure 1). The adult flea is stimulated to erupt from its pupa when there is vibration, warmth or carbon dioxide from a nearby mammal. The flea then settles on a mammalian host and feeds. Flea larvae feed on adult flea faecal pellets and will often burrow deep into carpets as they do not like heat or light because they are susceptible to drying out. This is important to stress when advising owners to spray the environment to ensure they spray under furniture and around pet bedding areas. Flea eggs and flea faecal pellets are often concentrated in pets' bedding or sleeping areas. The pupae are the most resistant stage of the flea life cycle and can persist in the environment for several months.