CAUSATIVE FACTORS

Primary Causes

Primary causes are usually the actual causative agent that directly causes the otitis externa. these can occur alone and induce otitis externa without predisposing or perpetuating factors viz,

Bacteria and Yeast : Normally in most of the dogs pathogenic bacteria and yeast are present in ear canal but are in low numbers. Parameters like inflammation, increased secretion of glands, humidity can provide platform for the multiplication of these organisms and leading to the disease. Hence, presence of bacteria and yeast in the ear canal does not mean that they are the primary causative agents.

The pathogenic bacteria isolated are Staphylococcus, Streptococus, Pseudomonas and Proteus species and yeast in Malassezia pachydermatis.

DIAGNOSIS

• Clinical signs
• Physical examination
• Otoscopic examination

CLINICAL SIGNS

History

The most common and earliest indicaiton of otitis externa is aural pruritus (itching) or head shaking. As the otitis progresses, a mild to marked exudates discharge may develop. This is most often the point at which a client brings the pet to the veterinarian.

It is often helpful to establish whether the pruritus or a discharge was the earliest sign. In many cases the client may not be sure but some may indicate that when pruritus was first noted there was no discharge. In many early cases, especially when the primary cause is a hypersensitivity reaction, the ear canal will look normal or have erythema limited to the pinna. Parasitic disease usually begin with pruritus but are more variable, (eg., ear mites in cats often initially cause a dark discharge).

Once pruritus has been established as the initial sign, then the following points may revolve for developing otitis externa:

• Was there a rapid onset after the pet was outside?
• Is there exposure to roaming dogs or cats in the vicinity that could be a source for ear mites?
• In most hypersensitivity cases of otitis externa, odor and discharge will occur following development of a secondar infection.
• Have powders or other treatments been applied to the ear canals?
• If recurrent or chronic, what previous treatments were utitized? What was the response? If initially good and then while on treatment the condition worsened, a contact or drug reaction should be suspected.

PHYSICAL EXAMINATION

Changes indicative of otitis externa include erythema (redness), swelling, crusting, alopecia, head shaking and pain on palpation of ear. Aural hematomas and acute moist dermatitis of the face are also common with aural pruritus, although clinical otitis externa may not be noticeable. Emphasis should be placed on looking for primay causes as well as evidence of otitis externa. A thorough dermatologic examination may show signs of pruritus in other body locations.

OTOSCOPIC EXAMINATION

The otoscopic examination is used to detect foreign bodies, determine whether otitis media is present and assess what type of lesions, exudates and progressive pathologic changes have occured.

The type of discharge may be clue as to what primary or perpetuating factors may be involved. Debris resembling dry coffee grounds is typical of ear mites. Moist brown discharge tends to be associated with cocci and yeast infections. Purulent creamy to yellow exudates are most often seen with gram-negative infections.

TREATMENT

Therapy of otitis externa is dependent on identifying and controlling the primary diseases. In addition, cleaning the ear canals and middle ear, topical therapies and systemic medications may be required for the effective elimination or control of primary causes. The major components of successful treatment plans for otitis externa is as follows:

• Identify and control primary diseases and predisposing factors.
• Perform a cytologic evaluation to determine which perpetuating microorganisms are present.
• Clean the ear canal with antiseptic and allow to remain the constituted antiseptic in the canal for 3-5 minutes
• Dry the ear canal
• Systemic therapy if otitis media is present
• Re-examine in 1-2 weeks to determine whether therapy has been effective and further cleaning in the hospital or by the client at home will be indicated.

Examination and adequate cleaning may be accomplished only with appropriate patient restraint. Sedatives such as xylazine HCL or ketamine and diazepam may be sufficient for most cases. Others will require a general anesthetic. Many clients are reluctant to have their dog anesthetized but are of more understanding if the need for getting the ears cleaned and completely examined and explaned in detail. It also helps to explain that some procedures are painful, as well as the problems that might occur if the patient moves while instruments are in the ear. Clients feel better knowing that with sedatives or anesthetics their pets could occur from uncontrolled movement during cleaning.

CLEANING

Thorough cleaning of the ar canal is extremely important for the effective management of otitis externa. Cleaning promotes effective therapy. The presence of an exudates interferes with adequate examination until cleaned out.

Wax or purulent exudates prevents topical mediations from reaching the skin lining the canals. Mediations are not able to reach the bacteria or yeast present beneath exudates. Thorough cleaning removes bacterial toxins, cellular debris and free fatty acids, reducing the stimulation for further inflammation.

Cleaning Techniques

A variety of instruments are required to adequately clean the majority of ear cnals presented.

A feeding tube and a 12 ml syringe are very effective for flushing the ear canal.

Once flushing has been completed, the ear canal is dried or in cases complicated by bacteria, if the tympanic membrane is intact, a chlorhexidine solution is extremely effective. If the tympanum is reptured, the acetic acid at 2% or 5% strength may be preferred; howeve, at 5% acetic acid can cause a slight burning sensation when applied to inflammed, eroded or ulcerated epithelium so this should be done while the patient is still sedated.

TOPICAL THERAPEUTIC AGENTS

Numerous topical medications of the external ear canal are available. Most contain various combinations of glucocorticoids, antibacterials and antifungals.

Glucocorticoids: have anti-inflammatory effects and decrease exudation and swelling. there are many different types of topical glucocorticoids available, and it is best to choose several products of differing potency and become familiar with them. the systemic absorption of more potent topical glucocorticoids should make the clinician cautious of long-term treatment.

Clients should be cautioned not to let their skin to come in contact with topical glucocorticoids. Human facial skin is especially sensitie to potent topical gluocorticoids and clients should be cautioned especially against allowing these products to contact their face.

Antibacterials : the aminoglycosides (neomycin, gentamicin) and chloramphenicol are potent antiboitics with good activity against the pathogens usually found in otitis externa cases. The aminoglycosides especially gentamicin can be ototoxic with prolonged use or in animals with ruptured tympanum.

Chloramphenicol is a potent broad spectrum antibiotic highly effective against bacteria like staphylococcus, streptococcus sps that are commonly involved in causing otitis externa and is considered to be non-ototoxic unlike gentamicin after prolonged usage.

Acetic acid has been shown very effective in the treatment of otitis externa. Acetic acid is most effective against Pseudomonas, with a 2% solution being lethal within one minute of contact. Staphylococcus and Streptococcus can be killed within 5 minutes of contact with 5% acetic acid.

Antifungal agents are required in any case complicated or caused by the yeasts Malassezia or candida. Clotrimazole is one of the common antifungal employed in the treatment.

Parasiticidal drugs that are used for Otodectes mites are ivermectin. Amitraz and carbaryl. Collies and Collie crosses should not be treated ivermectin.

The ideal otic product should have the following components:

• Chloramphenicol - Broad spectrum antibiotic
• Clotrimazole (antifungal)
• Beclomethasone ( glucocorticoid not absorbed systemically)
• Lignocaine HCL (local anesthetic)
  
  

GI disorders are common in pet rabbits but most of the problems are easily controlled and prevented with proper diet and management. An improper diet is the leading cause of GI disorders and the signs noticed are inappetence, diarrhoea, dull, decreased activity and abdominal discomfort may also be seen. A better diet for pet rabbits includes a limited amount of pelleted feed, grass hay, and a measured quantity of dark, leafy green vegetables. COMMON PROBLEMS GI Obstruction Complete gastric or intestinal obstruction is uncommon in pet rabbits but occasionally a house rabbit may consume carpet fibers or other foreign bodies that lead to blockage of the GIT (Gastrointestinal tract). The instant signs observed are abdominal paid and enlargement. Immediate attention is mandatory to survive the animal. Initially the treatment consists of administering analgesics, intravenous fluids, and short acting corticosteriods. To confirm the diagnosis, animal should be subjected to radiograph and if the diagnosis is confirmed of obstructions surgery should be performed at the earliest. Enteritis Generally enteritis ( inflammation of intestine) is caused by feeding improper diet and to some extent stress is also involved in causing enteritis. It results when pathogenic bacterial and toxins multiply in the gastrointestinal tract leading to clinical signs viz loose motions, inappetence, depression, later on results in dehydration and death if not attended at appropriate time. The treatment should consist intravenous fluids to correct dehydration, metronidazole and gastric motility modifier in addition to broad spectrum antibiotics such as trimethoprim-sulfamethazole or enrofloxacin. Parasitism Protozoa are the most common parasites infecting gastrointestinal tract. Coccidiosis, the disease caused by protozoa Eimeria species, commonly infects yound rabbits less than 8 weeks old. Clinical signs include weight loss, dehydration and diarrhoea ranging from soft to watery feces containing mucus and may be blood. The effective treatment is administering oral sulfamethazole and trimethoprim for atleast a week. Trichobezoars (hair ball) Rabbit is most susceptible to developing hair balls in the stomach. Hair are normally present in the stomach but a low fiber, high-carbohydrate diet may reduce gastric motility resulting in dehydration of the mass in the stomach. The mass of hair is unable to pass and may block the intestinal passage leading to obstruction of gastrointestinal tract (GIT). Radiograph should be taken to confirm the diagnosis and the treatment should be initiated as quickly as possible. Fluids should be administered and metaclopromide that effectively stimulates gastric motility. Antibiotics to be given to control bacterial overgrowth for 3-5 days. Surgical intervention may be necessary to remove the trichobezoar and the prognosis is poor for rabbits that require surgery.