Secondary Infections
Secondary infections are opportunistic infections as they typically develop during or following a pre-existing infection. They can be associated with allergies and are usually fungal (e.g. Aspergillus, Candida and Malassezia) or bacterial (e.g. Pseudomonas, Staphylococcus and Streptococcus) in nature. The risk of them developing, their frequency, severity and treatability is dependent on a number of factors.
For example, the dog’s health, treatment used and level of sanitation can all play a role. In particular, a suppressed or compromised immune system increases the risk of further complications e.g. due to cancer or having taken a medicated treatment which alters the natural balance between beneficial and detrimental microbes in the body. Genetics is also implicated, as certain breeds such as Australian Terrier, Chihuahua, Maltese, Poodle and Silky Terrier appear more prone to developing yeast infections.
Secondary infections can occur both internally (e.g. lungs) or externally (e.g. skin) and can be associated with:
- Fever.
- Inflammation.
- Lesions or sores.
- Odor is not uncommon, which can range from musty (typically fungal) to offensive or putrid (often bacterial).
- Possible discharge and unusual secretions (e.g. viscous and cloudy mucus) or pus.
- Reddening or discoloration.
- Thickening of skin may also occur with certain infections e.g. as seen in yeast dermatitis (a.k.a. Malassezia dermatitis) caused by the fungus Malassezia pachydermatis.
Aside from an allergy related secondary infection e.g. due to skin damage resulting from scratching, it should be noted that hypersensitivity can occur to particular microbial antigens i.e. the presence of the bacteria or fungi itself may elicit an allergy response.
Depending on the location of the secondary infection, diagnosis may include skin, blood and other diagnostic tests. For example, microscopic observation of skin scrapings, smears, swabs or even a biopsy can help in identifying fungal skin infections.
The use of antibiotics (for bacterial infections) or antifungal medications (for fungal infections) may be required to both minimize the discomfort/distress experienced by the dog and to treat the problem successfully. These may be administered either topically (creams, drops, lotions, sprays), orally (capsules, liquids, pills, tablets) or intravenously (injection or via a drip) depending on the exact nature and location of the infection.
Although secondary infections can be minor and clear up on their own, if left untreated, there is a potential risk of them becoming very serious and possibly life-threatening e.g. through causing sepsis. Furthermore, although these infections may respond well to medicated treatments and clear up completely, the risk of an infection reappearing once the therapy ceases is significant if the underlying cause is not identified and eliminated i.e. preventing re-exposure to the problematic allergen in the case of allergy related secondary infections.
Hot Spots
The term hot spot refers to Pyotramatic dermatitis (literally: “pus /self-inflicted trauma” + skin inflammation) also known as moist dermatitis or summer sores. The painful condition arises because the skin becomes broken and a secondary bacterial infection develops. Broken skin typically occurs through either direct injury or via scratching an itch that is triggered by allergies and insect bites. However, this type of dermatitis can also be associated with an anal gland infection.
Hot spots often develop under the ear flaps, on the face and/or body flanks, although they can occur anywhere on the body. It is a condition that is more common in dogs that have long and thick coats and is characterized by hair loss, inflammation, irritation, sores and purulent exudate (pus) with possible odor. In its endeavor to find relief from the incessant itching, the dog’s repetitive scratching, licking, nibbling and chewing of the hot spot only exacerbates the problem.
Treatment usually involves a multipronged approach but overcoming the behavioral aspect of the obsessive compulsive desire to lick and chew the hot spot can be difficult. The area is shaved and the wound is cleaned and sterilized e.g. peroxide, then topical medication is applied incorporating a bactericide, analgesic for pain and an anti-inflammatory. This is followed up with oral antibiotics possibly coupled with steroids (corticosteroids) and antihistamines.
Preventative measures used to help safeguard against further outbreaks of hot spots can include physical (e.g. Elizabethan neck collars), psychological (e.g. behavioral modification therapy), and pharmaceutical medications. Finally, in order to break the itch–scratch–skin damage–secondary infection–itch… cycle, it is essential to determine the underlying trigger (type of allergy and specific allergen) and prevent future exposure to it.
Lick Granulomas
A condition related to hot spots, known as lick granulomas (a.k.a. acral lick dermatitis), results from compulsive licking. Though allergies and hot spots can be involved, the primary factors associated with the condition appear to be psychological problems and boredom. However, genetics (hereditary) appear to play a role as certain breeds such as the Border Collie, German Shepherd, Golden Retriever, Labrador Retriever and Staffordshire Bull Terrier are more prone to the condition.
Lick granulomas are typically characterized by raised/ulcerated skin especially on the animal’s wrist or ankles. Treatment, as with hot spots, is usually multipronged, and once again, overcoming the dog’s psychological compulsive desire to lick the area makes it particularly challenging to treat. The traditional approach involves physically preventing the dog from licking the affected area, using antimicrobials (e.g. antibiotics) to prevent infection and cortisone steroids to reduce inflammation and heal the wound. Medications that target breaking the psychological compulsive desire to lick have been used with limited success. A more recent technique using laser treatment has yielded promising results.
