An introduction to identifying external dog parasites

Posted by Dr Dog. January 6th 2014.

Parasites in dogs can be separated into two main categories; internal and external.

Some parasites will cause minimal problems to your pet whereas with others the consequences can be life-threatening.

For the health and well-being of your dog it is essential that you protect your pet with appropriate and effective preventative treatments on a regular basis.

Here, we will provide you with an overview of the common UK parasites and the potential problems they may cause. If you are travelling abroad with your dog then you should seek further advice from your vet on the parasite risk abroad.

Vets checking dog for external parasites

What are external parasites?

These are parasites that live either on top of or within the skin itself. Some external parasites may only cause superficial skin problems but some may be carriers for other organisms that can be a problem in themselves.

1.    Fleas

In the majority of infestations the fleas are actually cat fleas. They can be found on any dog and appear as small brown fast moving parasites that readily jump up to 150 times their body length. Fleas can cause severe allergies in sensitive dogs resulting in severe itch, hair loss (mainly down the back) and often a secondary skin infection. All pets in the household must be treated, not just the allergic ones. It is essential that the environment is treated also as your dog is merely a restaurant to the flea, your home is the hotel where most of the life stages live. It is advisable to ensure that any pet that has had contact with fleas is wormed against Dipylidium, a tapeworm that the fleas can carry.

2.    Lice

Lice infestations are seen most commonly in young, old and debilitated dogs. They are transmitted through contact. There are two types of lice: sucking lice which feed on blood and if severe can lead to anaemia and biting lice that feed on skin. Adults and their eggs or ‘nits’ can often be seen on the dog’s hair shafts with the naked eye. Both types lead to a scurfy, dry coat and sometimes cause itchiness. Treatment is simple with the appropriate product, also be sure to treat the environment.

3.    Ticks

Ixodes is the most common tick found in the UK. Dogs often pick them up whilst walking in grassland, scrub and shrubs mainly between March and November. They look like round, dark swellings attached to the skin and are often mistaken for growths. In general they cause only a local reaction on the skin but they can carry several dangerous diseases, namely, Lyme disease in the UK (Erlichiosis and Babesiosis can occur in areas of Europe). A number of flea treatments will protect against ticks and care must be taken if any attempt is made to remove to ensure the mouthparts are not left behind as this can cause a reaction and possibly infection to result.

4.    Ear mites

The most common is Otodectes cynotis, which feeds on the waxes and oils in the dog’s ear canal. Often a dark, black debris can be seen and if left untreated can lead to red, irritated and infected ear made worse by the dog’s shaking and scratching. The three week life-cycle can make treatment with drops lengthy and frustrating but spot-on flea treatments are available that with some ear cleaning make the problem easy to treat provided caught early and no secondary problems e.g. infection has developed that would require veterinary treatment.

5.    Cheyletiella

Often referred to as ‘walking dandruff’. The mite is frequently seen walking through the animals coat carrying skin scales and to the naked eye looks like dandruff on the move. Transmission is via direct contact between animals and they can bite humans often leaving small itchy, red bumps. Problems caused by the mites range from nothing to intense itching, dry flaking skin and hair loss mainly down the back. Many modern flea treatments will eliminate the mite. All in contact pets and the environment must be treated.

6.    Sarcoptes or scabies

The Sarcoptes mite burrows into and completes its whole life-cycle in the skin. It may affect any dog and can bite people. It results in a very severe itch and the most common sites are the ears, elbows, armpits, hocks and underside of chest/abdomen. Many dogs will have balding ears with scaly edges that when rubbed are intensely itchy. Hair loss and infection quickly develop due to the scratching and prompt diagnosis and treatment is essential. Skin scrapes and blood tests can be used to diagnose. Often skin scrapes will give false negatives and the blood test results are not immediate so treatment is often started based on the clinical signs. Several spot-on flea treatments can be used but veterinary attention may be required for any secondary problems e.g. infection. In areas of known cases or high fox population then regular prevention is advised as is treatment of environment/bedding as the mite can live off the dog for a few days.

7.     Demodex

The Demodex mite lives within the skin/hair follicles. Transmission is via prolonged contact e.g. from mother to pup during suckling and so the first signs of patchy baldness tend to be around the face, muzzle, forelimbs, eyes. A large number of dogs will carry the mite and show no signs but for some they cause a problem. If minor, pups will often ’grow out of the problem’ as their immune system matures. For others, and in adults, secondary infection can develop and unless dealt with medically can become severe. Sometimes in adults there can be an underlying immune system problem that makes the disease hard to treat. Diagnosis is via a skin scrape in the consult room. Treatment can be lengthy and require a number of repeat visits and tests. It is advisable not to breed from any dog that has suffered from Demodex. They do not live on humans.

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