Flea-Related Problems in Pets
Biting or scratching is usually the first reaction of an animal with fleas. Some animals may begin excessive grooming to try to rid themselves of the irritation, eating many of the fleas in the process. Light-haired dogs or cats that do this may develop an orange-brown discolouration due to salivary staining. These general symptoms are usually referred to as pruritus.
Pruritus
Pruritus (itching) is caused by reactions to flea saliva. During feeding, the flea releases saliva to stop blood from coagulating. The saliva contains chemicals that irritate the host:
- Histamine-like substances (compounds that cause allergic responses).
- Proteolytic enzymes (substances that initiate the breakdown of protein).
- A hapten (an incomplete antigen that becomes complete when combined with collagen in the skin).
Some animals have a higher tolerance to fleas and aren't disturbed by them. Others suffer varying levels of irritation and may react after only a few bites.
Flea Allergy Dermatitis (FAD)
Dogs and cats that are hypersensitive to flea saliva have intense reactions, often out of proportion to the number of fleas on the pet. Research indicates that FAD may be caused by intermittent exposure to large numbers of fleas. Animals sensitised in this way may become intensely reactive even if only a small number of fleas are present. This is significant as it suggests that FAD may be avoided by preventing repeated flea infestations.
The initial reaction is usually a reddened wheal, which forms a papule or swollen nodule and crusts over. After that, several secondary changes are possible:
- Superficial pyoderma (skin infections affecting the skin surface).
- Seborrhoea (scaling, crusting, yellowish patches on the skin).
- Diffuse erythema (reddening of the skin over various parts of the body).
- Hair loss.
- ‘Hot spots’ - bare, eroded, oozing patches (a severe localised skin infection or pyoderma).
The pruritus, or itching, that occurs in dogs with FAD is intense, and results in self-mutilation. Generally, clinical signs are distributed over the inner thigh and abdomen, and along the spine and hindquarters. Corticosteroids, which must be prescribed by a veterinarian, are often used to temporarily relieve clinical signs. A flea control programme is needed to resolve the problem completely.
Tapeworm (Dipylidium caninum)
This species of tapeworm uses the flea as an intermediate host in its life cycle. Egg packets deposited by the adult tapeworm are shed into the environment where they are consumed by flea larvae. If a pet ingests an adult flea that ate tapeworm eggs as a larva, the tapeworm parasite is passed on. In pets, the flea tapeworm does not usually cause serious disease. However, it can cause diarrhoea or irritation around the anus (resulting in scooting) and the segments can be seen as small rice-like objects clinging to the hind end of the animal near the base of the tail. Their presence can evoke a feeling of disgust in people interacting with pets. In addition, people can become infected if they accidentally ingest infected fleas.
Anaemia
Being blood-sucking parasites, heavy flea infestations can cause parasitic anaemia, particularly in young animals. Fleas in the genus Ctenocephalides have been reported to produce anaemia in dogs, cats, goats, cattle and sheep. Severe flea infestations in puppies can cause anaemia to the point of death.
Flea-Related Conditions in Humans
Fleas can reproduce on any mammalian blood supply, including humans. However, a female flea must feed for a long period of time before beginning egg production. Fleas may spend 2-3 hours sucking on one spot. But most humans will scratch or perform some action to interrupt this feeding process. As such, the flea is not able to feed for the required length of time to produce eggs.
In humans, disease transmission by fleas is not a common occurrence. However, any suspected reactions should be discussed with a doctor.