Pet Care

Bacterial infection in cats and dogs

Cats and dogs are susceptible to various bacterial infections caused by a range of bacteria. These include:

• Skin infections, such as deep and superficial pyodermas, which are usually caused by Staphylococcus bacteria. Symptoms include itching and irritation, pustules (Inflamed swellings on the skin filled with pus), sores and patches of hair loss.


• Urinary tract infections; such as cystitis. Symptoms include blood in the urine, abnormal or frequent urination in inappropriate places, blockage of the urethra (tube leading from the bladder) usually caused by Staphylococcus and Proteus bacteria.


• Pneumonia is a lower respiratory tract infection usually due to the bacteria Bordetella bronchiseptica and Streptococcus zooepidemicus as well as others; also fungal or viral infection. The infection causes inflammation of the lung tissue, with symptoms including difficulty breathing, fluid on the lungs, cough, fever and loss of appetite.


• Upper respiratory tract infections include infections of the nose throat and sinuses. Kennel cough is a form of bronchitis that is common infection in dogs and is caused by the bacteria Bordetella bronchiseptica. Infection with other bacteria such as Streptococcus, cause symptoms including congestion, cough and inflammation.


• Enteritis is inflammation of the small intestine and can be caused by bacterial infection with a range of different bacteria, including Salmonella, Shigella, Staphylococcus and Escherichia coli. Symptoms include, vomiting, diarrhoea, dehydration and fever.

Antibiotics

Amoxycillin is a broad-spectrum penicillin-like antibiotic that belong to the beta lactam group of antibiotics. It kills bacteria by blocking formation of the bacterial call wall. However, it contains a structure called the beta lactam ring, which is readily attacked by the bacterial enzyme beta-lactamase and can result in resistant bacteria, such as some staphylococci. Amoxycillin is often used in combination with clavulanic acid, an antibiotic structurally related to the penicillins that is able to inactivate a wide range of beta-lactamase enzymes, which helps prevent resistance and also broadens the range of use for amoxicillin. A combination of these two antibiotics is available in drops and tablet form for treating bacterial infections in cats and dogs.

Inflammatory skin infections and topical treatment

Animals including are dogs, cats, horses and cattle are susceptible to moist dermatitis, an inflammatory skin condition caused initially by a skin irritation, which can be an insect bite, skin allergy or laceration. This causes the animal to scratch so that the skin becomes red and inflamed turning into a moist open wound due to constant scratching and biting of the skin. An effective treatment for moist dermatitis is a topical cream containing three separate ingredients:

• Neomycin, a broad-spectrum antibiotic commonly used in topical medications and used to kill a wide range of bacteria that cause skin infections, by inhibiting bacterial protein synthesis.


• Hydrocortisone, a corticosteroid anti-inflammatory that inhibits the production of inflammatory chemicals.


• Lignocaine a local anaesthetic that helps numb the pain and irritation of the skin lesion so that it can heal.

Inflammation and prostaglandins

Inflammation is a normal reaction to protect the body from harmful pathogens or irritants and to promote healing of damaged tissues. It is complex process of cellular interactions of the immune system that is mediated by certain chemicals produced at the site of tissue damage, infection or trauma. Symptoms of inflammation include redness, heat, swelling and pain or discomfort.
The process of inflammation includes the widening and increased permeability of small blood vessels, exudation of fluid and migration of immune cells like macrophages and neutrophils into the tissues where damage, infection or irritation has occurred. The fluid causes swelling and the cells produce inflammatory chemicals like prostaglandins, interleukins and leukotrienes. These chemicals attract more inflammatory cells to help with wound healing and disposing of harmful pathogens but they also magnify the inflammatory response. In doing their job, some of these inflammatory mediators can also cause pain, swelling, fever and redness. If the inflammatory process continues beyond protecting and healing it becomes chronic and can end up damaging normal tissues.

Nonsteroidal anti-inflammatory drugs (NSAID)

Nonsteroidal anti-inflammatory drugs (NSAID) are medications that inhibit cyclooxygenase (COX), an enzyme involved in the synthesis of prostaglandins like PGE2, which have important functions throughout the body but are also potent inflammatory mediators and cause pain, swelling and other symptoms of inflammation. They are called nonsteroidal as corticosteroid drugs are also used to treat inflammation but target a different enzyme in the pathway of prostaglandin synthesis.

There are two main COX enzymes, COX-1 and COX-2. COX-1 is present in most cells and plays an important role in many normal cell functions, including aggregation of blood platelets, which controls bleeding; protection of the stomach lining or mucosa by promoting cell growth; also in maintaining normal kidney function by regulating blood flow. COX-2 is only produced by inflammatory cells, and is induced during the inflammatory process, although it is also found in very small amounts in some tissues.

Some NSAIDs like phenylbutazone and carprofen inhibit both COX-1 and COX-2, which is the cause of the more serious side effects of non-specific COX inhibitors. These include gastric bleeding and ulcers due to the inhibition of prostaglandins that are protective of the stomach lining and have vasodilator (cause widening of blood vessels) action which helps maintain normal blood flow. Kidney damage is also a potentially serious side effect and again this is due to the inhibition of protective prostaglandin production by blocking COX-1. Meloxicam and firocoxib are specific COX-2 inhibitors and have no inhibitory action against COX-1, which makes them more effective for pain and inflammation, without the gastrointestinal or kidney side effects associated with COX-1 inhibition.

Inflammatory conditions

Inflammation and pain occur due to several chronic and acute conditions in animals, including:

• Inflammatory joint diseases like osteoarthritis, a degenerative disease of the joints caused by wear and tear where the cartilage around the bone is worn away. It is a common condition in many dogs, particularly as they age, which restricts mobility and can cause lameness.


• Soft tissue injuries, such as sprains and strains that are due to trauma to the tendons, ligaments, muscles or joints.


• Following orthopaedic and soft tissue surgery.

Anti-inflammatory medications for veterinary use

These anti-inflammatory medications are generally specifically indicated for veterinary use.

• Phenylbutazone is an oral paste used to treat pain and inflammation in horses caused by joint and soft tissue injury


• Carprofen is a non-specific oral anti-inflammatory used to treat dogs to help manage the pain and inflammation caused by osteoarthritis.


• Meloxicam oral suspension and firocoxib chewable tablets are specific COX-2 inhibitors used to relieve pain and inflammation due to osteoarthritis in dogs and following orthopaedic and soft tissue surgery.

Parasitic worms in pets

Parastitic worms are endoparasites as they live inside their host. They are common to both cats and dogs and can cause serious illness. There are many different species and most of them affect the gastrointestinal system and have complex life cycles. The most common parasitic worms that infect cats and dogs include the following:

• Heartworm is a parasitic worm transmitted by mosquitoes. It has two larval stages in the mosquito and another two in its next host, which can be cats or dogs. Following a mosquito bite, the heartworm larvae transform into the next larval stage and migrate through the tissues to the heart and lungs, where they mature into adults, grow rapidly, reach sexual maturity and mate. The females produce microfilariae, which enter the blood stream ready to be transmitted back to the mosquito host to continue the life cycle. Heartworm causes tissue damage and can cause serious health problems that can result in heart failure and eventually death. Symptoms in dogs include coughing up blood, breathlessness, fainting and congestive heart failure. Symptoms in cats include vomiting, diarrhoea, weight loss, lethargy and difficulty breathing.


• Roundworms belong to the group of ascarids and are very common in cats and dogs, causing health problems including damage to the intestine and digestion problems as they absorb nutrients from the blood of the host. Adult dogs are infected by ingesting eggs from soil, infected food or water and puppies can be infected while still in the womb or when lactating through infected milk. Once swallowed the roundworm eggs hatch and the larvae migrate through the intestine wall into the lungs and internal organs, where they can lie dormant; they can also migrate through the uterus to infect the foetus. They are eventually coughed up from the lungs and swallowed where they mature in the intestines. Mature worms grow to great lengths and produce eggs, which are passed out of the host in the faeces ready to begin the life-cycle again. Symptoms include an extended abdomen, worms in faeces, coughing, lethargy, intestinal obstruction and colic.


• Hookworm infestation is more common in dogs than cats and is transmitted by larvae in infected soil, food or water entering by ingestion or by burrowing through the skin. Like roundworm puppies can be infected while still in the womb by larvae that migrate through the uterus to infect the foetus or when lactating through infected milk. When the larvae reach the intestines they mature into adults and attach to the wall of the intestine where they feed from blood. The mature hookworms produce eggs, which are shed in the faeces and hatch in the soil. Symptoms include poor appetite, blood in the stools and anaemia, which if it becomes severe can be fatal.


• Whipworm is a common parasitic infestation in dogs and less so in cats. Dogs and cats become infected by ingesting food or water contaminated with eggs. The eggs hatch in the large intestine and the larvae mature into adults in the large intestine or bowel. The adults attach with specialised mouthparts and burrow through the intestine wall, where they feed on the host blood. The adults lay eggs in the intestine, which are passed out with the faeces and remain in the soil until they are ingested again. Symptoms of whipworm infection include inflammation and bleeding of the intestine and anaemia.


• Tapeworms are cestodes that live in the small intestines and can grow to great lengths. The lifecycle consists of the eggs, which are produced by each multiple segments of the adult worm in large numbers. These pass out of the main host in the faces and are ingested by the intermediate host, such as cattle, pigs and sheep, where the eggs hatch and the larva or hyatid tapeworm migrates to various organs and remains dormant as a hyatid cyst. The main host (dog or cat) becomes infected by eating infected meat. Once in the main host intestine, the tapeworm matures and attaches to the intestine wall, using specialised suckers and hooks on the head that allows it to attach and feed on the nutrients of its host. There are several species that can infect dogs, including the Taenia species, but tapeworms do not usually cause any major health problems.

Anthelmintic de-worming drugs

Several anthelmintic drugs are available that are effective for use as de-worming medications for dogs and cats and are generally used as a combination of two or more of the following:

• Ivermectin is effective against most common intestinal worms except tapeworm in dogs. It acts on the nervous system of the larval stage of the parasitic worm and causes paralysis and death before it reaches major organs.


• Pyrantel and oxantel are effective against most common nematodes in dogs, acting as neuromuscular blocking agents that paralyse the roundworm and hookworm while they are feeding in the dogs’s intestine, so that they lose their grip and pass out in the stools.


• Praziquantel is effective against intestinal tapeworms (cestodes) in dogs and works by interfering with the tapeworm’s ability to protect itself against its host, causing the tapeworm to lose resistance to digestion by the host digestive enzymes.


• Selamectin effective against heartworm, hookworm and roundworm in cats and dogs and acts as a as neuromuscular blocking agents that paralyses the roundworm and hookworm while they are feeding in the intestine, so that they lose their grip and pass out in the stools.

Heart conditions

Congestive heart failure (CHF) is when the heart muscle becomes weakened so that it does not pump efficiently and is a common condition in dogs. It can be due by a variety of causes. Dilated cardiomyopathy (DCM) is the most common cause of CHF in dogs, particularly large breeds and some dogs have an inherited predisposition for DCM. It is characterised by dilated or enlarged chambers of the heart, and reduced contraction of the heart muscle, resulting in congestive heart failure. Warning signs of DCM include heart murmur and arrhythmias (abnormal heart beat). CHF can also be caused by degeneration of heart valves, called endocardiosis causing them to become leaky, resulting in mitral valve disease.

Symptoms of CHF include lethargy, exercise intolerance, shortness of breath, difficulty breathing, cough, swelling of the abdomen due to collection of fluid around the lungs and abdomen, peripheral oedema, which is fluid collection in the tissues and weight loss; but very rarely does it result in chronic artery disease or a heart attack. If CHF progresses it can be fatal particularly in older dogs or breeds with a genetic predisposition.

Treatment for heart conditions

Heart failure in dogs can be treated by using medications that help improve the efficiency of the heart and increase blood flow; also with diuretics that help remove fluid in the tissues.

• Pimobendan is a drug specifically used for treating heart failure in dogs and is classified as an inodilator that works by two mechanisms of action. It acts directly on the cells of the heart muscle making them more sensitive to calcium, which is needed for muscle cells to contract and this increases the strength of muscular contraction. Pimobendan also inhibits an enzyme found in vascular smooth muscle cells, called phosphodiesterase lll that causes blood vessels to contract and narrow. This action causes peripheral and coronary blood vessels to widen, which reduces the workload on the heart and allows it to pump more efficiently. Pimobendan helps treat dogs with heart failure due to DCM or mitral valve disease and can be used in conjunction with other heart drugs.


• Propentofylline is a xanthine derivative drug that is used to treat dogs with circulation and breathing problems, particularly in older dogs, to improve lethargy, willingness to and tolerance for exercise and loss of general wellbeing due to impaired circulation or heart problems like arrhythmia. Propentofylline is as a vasodilator that acts directly on vascular smooth muscle cells and inhibits the phosphodiesterase enzyme that causes blood vessels to contract and narrow. This action widens blood vessels and increases blood flow particularly to the heart, skeletal muscle and brain; also reduces the workload on the heart. Propentofylline is also a bronchodilator and has the same action of the airways of the lung causing the bronchioles to dilate and widen, which increases air flow into the lungs. Propentofylline also helps improve the efficiency of the heart by improving the strength of muscular contraction and by increasing heart rate; it also has anti-arrhythmic actions to help return to a normal heart beat.


• Frusemide is a diuretic medication for cats, dogs, horses and cattle, to reduce oedema, which is a symptom of congestive heart failure. Frusemide acts directly on the kidneys to help remove fluid that has built up in the tissues. It works by inhibiting the reabsorption of salts back into the blood, so that more salts are excreted into the urine so that more water is removed from the blood and this draws more water out of the tissues.

Ectoparasites in cats and dogs

Ectoparasites are parasites that live on the skin of their host. They include parasitic insects like fleas and lice and parasitic arachnids like ticks and mites. Most ectoparasites feed on the blood of their hosts and can cause health problems including dermatitis and anaemia.

fleas and lice

Fleas and lice are parasitic insects belonging to the same class of arthropod animals as wasps, bees, flies and mosquitoes.

• Fleas have a four-stage life cycle; the egg, larva, pupa and adult. The eggs are laid usually on the host, then they fall off and are deposited along with faeces on the ground. When the larvae hatch, they feed on the faeces and grow by moulting three times then spin a cocoon to become a pupa. This stage can lie dormant for some time both indoors and outdoors until vibration, warmth or carbon dioxide indicates that a suitable host is nearby, like the family cat or dog, the adult then emerges and uses its long hind legs to jump onto the host, bites it with specially adapted mouthparts and sucks the blood. Flea bites can cause severe irritation and itching that can lead to flea allergy dermatitis, which is a reaction to flea saliva. If the infestation is severe particularly in puppies or kittens, they can cause anaemia. Fleas are also carriers of disease like tapeworm, plague and typhus.


• Lice are transmitted by direct contact with another infested pet. There are two types; sucking lice that feed on blood and biting lice that feed on skin cells. Lice can spend their entire life-cycle on the host animal. They lay their eggs on the hair follicles in the skin, where they hatch and transform through three nymph stages into adults. Symptoms of lice include scruffy dry hair, itching and hair loss due to scratching.

ticks and mites

Ticks and mites are parasitic arachnids belonging to the same class of arthropod animals as spiders and scorpions.

• Ticks attach to the skin of its host with special adapted mouthparts and feed from their blood. They have a life-cycle of four stages, the egg, larva, nymph and adult. Adult ticks lay eggs on the ground which hatch into larvae that attach to the first host, which is usually a small animal like a rodent or bird. Each stage feed on blood and then falls off he host and transforms into the next stage by moulting. Dogs and cats pick up ticks either at the nymph or adult stage by physical contact from the outdoors, such as a wooded area, long grass or amongst short shrubs. Ticks are carriers of several diseases including tick paralysis, caused by a toxin produced by the tick resulting in symptoms like difficulty walking, swallowing and breathing and can lead to death; also Lyme disease, caused by transmission of a bacteria by the tick resulting in symptoms like fever, lameness, swelling of joints and lymph nodes and loss of appetite.


• Mites are transmitted by direct contact with another infested pet and can live on any part of the animal’s body and feed on skin cells and keratin in the outer layer of skin. The ear mite is one of the most common forms and these live in the ear canal feeding on wax and skin scales. Eggs are laid in the ear or on the skin and hatch into larvae, transforming into the nymph stage and finally maturing into adults. Symptoms of ear mite infestation includes a black discharge from the ear resembling coffee grounds with severe irritation causing the animal to scratch and shake its head and can result in ear damage and loss of hearing if left untreated.

insecticides

Insecticide is a general term used for treatment of insect ectoparasites but may also be effective against other parasites including arachnid parasites. Some also have anthelmintic properties and are effective against internal parasites, like some worms.

• Fipronil is a broad spectrum topical insecticide that kills fleas at adult and larval stages, particularly newly emerged adult fleas before they lay eggs and usually before they bite, which helps prevent flea allergy dermatitis. It also kills biting lice, and is effective against all stages of ticks, which are parasitic arachnids, and this helps prevent tick-borne disease transmission. Fipronil is applied to the skin, spreads by mixing with body oils and collects in the hair follicles of the skin, where it is slowly released to provide long-lasting protection. Fipronil works by blocking nerve transmission and disrupting the insect central nervous system, causing paralysis and death within 24-48 hours of application.


• Methoprene is an analogue of the growth hormone of insects, which mimics the action of the natural juvenile hormone and works as an insect growth regulator. Insect juvenile hormone is needed for the larval stages to develop but it prevents the formation of the insect pupa and its development into the adult. Methoprene disrupts the life cycle of insects like fleas that pupate, thereby attacking all stages of the flea while on the host animal reducing risk of further infestation.


• Selamectin is an antiparasitic drug that acts as an Insecticide and is effective against parasitic insects like fleas, also parasitic arachnids like ticks and ear mites. Selamectin is applied to the skin, spreads by mixing with body oils and collects in the hair follicles of the skin, where it is slowly released to provide long-lasting protection. It is also absorbed through the skin into the blood stream and acts as an effective anthelmintic in cats against parasitic worms like roundworm and hookwork that feed on the host blood. Selamectin works by blocking nerve transmission and disrupting the central nervous system, causing paralysis and death and is effective for up to 30 days.

The thyroid and thyroid hormone

The thyroid gland consists of 2 small lobes situated in the neck around the trachea (windpipe). 

The thyroid gland produces two hormones; calcitonin, which regulates calcium metabolism and thyroid hormone, which controls many important body functions, including how the body uses energy, regulates temperature, metabolises nutrients, and controls growth and development. 

Thyroid hormone exists in two forms.  Thyroxine or levothyroxine, also known as T4 and liothyronine or L-triiodothyronine also known as T3.  Up to 90% of thyroid hormone secreted by the thyroid gland is T4, which is inactive but is converted to the active form of thyroid hormone T3 when it reaches its target tissue. This conversion takes place in the liver, kidney and other tissues of the body and T3 then interacts with a specific receptor inside the nucleus of cells, to influence the transcription of specific pieces of DNA (genes) to produce proteins needed to manage and control a variety of processes, including carbohydrate, fat, protein and vitamin metabolism.

The production of thyroid hormone is regulated by a hormone produced by the pituitary gland in hypothalamus at the base of the brain, and is called thyroid stimulating hormone (TSH).  When levels of thyroid hormone in the blood are low, this stimulates increased production of TSH and thereby increases production of more thyroid hormone.  Conversely, when thyroid hormone levels increase, TSH production is decreased.  This is known as a negative feedback loop, which helps maintain normal levels of thyroid hormone in the blood.

Hyperthyroidism in pets

Hyperthyroidism or thyrotoxicosis, as it is also known, is a common disorder in cats, particularly older cats and is caused by overproduction of thyroid hormone usually due to a benign enlargement of the thyroid gland.  However, hyperthyroidism is a rare condition in dogs and is usually caused by a malignant tumour called thyroid adenocarcinoma. 

The enlarged thyroid gland in cats is similar to toxic nodular goitre in humans, which is one of the major causes of hyperthyroidism in humans.  The symptoms or signs of hyperthyroidism in cats can be dramatic and can cause serious illness.  They include:

• weight loss
• increased appetite (polyphagia) and increased thirst (polydipsia)
• increased food intake
• over activity and restlessness
• increased heartrate (tachycardia)
• diarrhoea and vomiting
• heat intolerance
• change in hair coat condition

If undiagnosed or left untreated hyperthyroidism can cause more serious illness including heart failure, high blood pressure and kidney disease.  

Medical treatment 

Although surgical removal of the affected thyroid tissue is an option for treating hyperthyroidism (thyroidectomy); also radioactive iodine treatment, medical treatment is available and successful.  Anti-thyroid drugs known as thioamides like carbimazole are widely used to treat hyperthyroidism in animals and humans.  They work by blocking the synthesis of thyroid hormone and help restore high levels of thyroid hormone to normal levels.  

Medical management of hyperthyroidism with carbimazole requires daily administration and is not a cure but can be also used stabilise the animal before radiation or surgery.  

Urinary incontinence and its treatment

Urinary incontinence is the loss of voluntary control of urination due to weakness or loss of muscle tone in the urethral sphincter, which is the muscle that controls urine flow out of the bladder. This condition is most common in older medium to large spayed female dogs and one cause is a malfunction of nerves in the part of the nervous system that controls urination. An effective treatment for this form of urinary incontinence is a syrup containing the drug phenylpropanolamine that works by acting as an alpha-adrenergic agonist and stimulates the nerves of the sympathetic nervous system. These nerve cells respond to catecholamine neurotransmitters (chemical used by nerve cells to communicate) like adrenaline. Phenylpropanolamine stimulates the alpha-adrenergic receptors in urethral muscle cells which increase muscle tone and results in tightening of the urethra which prevents urine leakage.