Tetracyclines

Tetracycline are bacteriostatic antibiotics with a broad spectrum of activity. They have been used clinically since the 1940s and as a result acquired resistance to them is widespread. In veterinary medicine tetracyclines are used most frequently for atypical bacterial diseases due to Chlamydia (particularly in cats), Borrelia, Rickettsia, Haemobartonella and Mycoplasma. Tetracyclines are the drugs of choice for Erlichia canis and Rickettsia rickettsii infections. Adverse effects that have been...

Mast cell tumours

The cutaneous form of mastocytosis tends to occur in middle-aged to older cats with single to multiple skin nodules, particularly on the head but potentially all over the body. They variably present as discrete to poorly demarcated, variably sized, raised, soft to firm, round, erythematous to white or yellow, alopecic, dermal papules, nodules and plaques. A skin biopsy will usually enable a rapid diagnosis. There is no association between the histological grading and the clinical outcome....

Metabolism

To understand how drug metabolism can differ between dogs and cats it is necessary to have a basic understanding of drug metabolism in general. In contrast to water-soluble drugs, which can be excreted in urine without being metabolised, drugs that are lipid soluble must be metabolised so that they can be converted to water-soluble metabolites that can be excreted, usually by the kidney. Drug metabolism occurs in the liver in two phases (I and II). Most differences between dogs and cats in drug...

Why are cats prone to certain toxicoses

Cats are by nature highly inquisitive animals that explore their environment and in the process accidentally expose themselves to a variety of poisonous agents. Cats possess finnicky eating habits, and although such habits undoubtedly offer some degree of protection from toxins in food, their concerted grooming and foraging behaviour may still lead to the ingestion of agents such as insecticides and various plants. The fact that many cats are maintained in an indoor environment for prolonged...

Allergic skin diseases

Allergic skin diseases are important because they form the majority of skin diseases observed in the cat. Cats may present with a variety of manifestations of allergic skin disease, including papulocrusting (miliary) dermatitis, symmetrical alopecia and EGC. Such diseases most often are caused by allergic reactions to parasites (most notably fleas, but also mosquitoes, occasionally Otodectes ear mites and possibly trombi-culids), food allergens and inhaled allergens (atopic disease). The...

Inherited polyneuropathies

Most inherited polyneuropathies are congenital, progressive and ultimately fatal. Cats with low concentrations of the enzyme D-glycerate dehydrogenase develop an unexplained axonopathy. Affected cats excrete excessive amounts of L-glycerate in their urine and have intermittent oxalaturia. There is oxalate crystal deposition in the kidneys, which are large and painful. Affected cats are young (5-9 months) and die from renal failure before 1 year of age. Inheritance is autosomal recessive....

Viral infections

Cats infected with cowpox are usually avid hunters that come into contact with infected prey items, especially voles and mice. Following inoculation of a bite wound the viral infection becomes apparent 10 days to several weeks later, with numerous cutaneous nodules and plaques (Plate 6.15). Infection is usually self-resolving over 6-8 weeks, unless the cutaneous lesions are mistaken for eosinophilic granulomas and steroids are administered. Infection may generalise with immune deficiency such...

Bacterial encephalitis

Bacterial encephalitis is rare, but occurs secondary to direct extension across the meninges into the CNS. Infection occurs most commonly as a sequela to chronic nasal infection, otitis media, otitis interna and penetrating bite wounds. Clinical signs reflect the site of infection. The cats are febrile and clinical signs progress rapidly. Culture of CSF may identify the causative organism. Effective treatment depends on appropriate antibiotic treatment. Sulfonamides, trimethoprim and the newer...

Cranial nerve VII facial

The facial nerve nucleus is located in the medulla. The nerve exits the brain close to the fifth and eighth nerves from the petrous temporal bone. Facial nerve palsies are common as the nerve is vulnerable to injury at several sites. The facial muscles are paralysed, the lip is loose and flaccid, the ear is immobile and the affected nostril does not dilate. There may be drooling from the mouth on the affected side. The cornea will dry and corneal ulceration is a consequence. Peripheral injury...

Food allergyintolerance

Food allergy in the cat may be associated with concurrent flea bite, inhalant or flea-collar hypersensitivity (White 8c Sequoia, 1989). Food allergy as a disease is a well-recognised cause of feline dermatological problems (Carlotti et al, 1990 Rosser, 1993), the prevalence of which varies from rare to common according to different authors. The pathophysiology of this syndrome is not completely understood. Adverse reactions to food may be either toxic or nontoxic if they are non-toxic they may...

Acquired deafness

Acquired deafness occurs with damage to the eighth nerve or its nuclei or sensory apparatus. In most cases vestibular signs are also seen as the vestibular branch of the nerve is also affected. Otitis media and interna can be accompanied by unilateral deafness, but auditory defects are less common. Tumours, trauma, degenerative disease and toxins (aminoglycoside antibotics) can all cause deafness, but acquired deafness due to a specific cause is rarely diag nosed. Assessment is also difficult,...

Eosinophilic collagenolyticlinear granuloma

The eosinophilic granuloma is the only true granuloma within this complex and is associated with peripheral circulating eosinophilia. There are no breed, age or sex predispositions, although cats less than 2 years of age may have spontaneous resolution. In a similar fashion to the plaque, the granuloma lesions are associated with allergic diseases in some cases, and may have a genetic basis in certain colony situations and within litters, and some are idiopathic. A distinct form associated with...

Behavioural consequences of feline fear

In fear situations cats can either withdraw from the environment, both social and physical, or show a decreased threshold of reactivity to stimuli, leading to reactive behavioural manifestations of the fear. Withdrawal from the environment can lead to an increase in withdrawn and secretive behaviour, including hiding, a reluctance to go outdoors or to enter open spaces within the home and a desire to climb onto high, inaccessible resting places within the home. These behaviours are all part of...

Feline fears and behavioural consequences

Although fears and phobias are perhaps more closely associated with dogs, feline fear is a real issue in behavioural medicine and the behavioural consequences can be many and varied. Some cats that are fearful may become more dependent on the owner, while others may lack confidence in dealing with family members. In extreme cases fearful cats can go on to form abnormal attachments with their owners and may display separation-related behaviours. Cats can also become agoraphobic and may show...

Singleagent versus combination chemotherapy

It is generally accepted that combination chemotherapy is more effective than single-agent chemotherapy. Using a combination of drugs with different mechanisms of action and different toxicities means that the overall tumour response can be enhanced without an increase in toxicity to normal tissues. Each component of a combination protocol should have proven efficacy when used in isolation and ideally the drugs should not have overlapping toxicities. Examples of protocols are given later in...

Dietary toxins and contaminants

The adverse effects of excessive vitamin A in the cat's diet have been known for a long time, but occasional cases are still reported in those cats fed excessive amounts of raw liver, often as a result of the owners' ignorance. The clinical picture is characterised by lameness in long bones, painful or stiff necks, abnormal gingival mucosa and depression. Toxicity has been recorded both in young kittens and in adult cats. Diagnosis is based on dietary history and radiographic findings of bony...

Therapeutic options for immunemediated skin diseases

Initial therapy is prednisolone at 2 mg kg twice daily for 10-14 days, followed by reduction to alternate-day therapy. In some cases therapy can be stopped for several weeks before the condition relapses. It is usually stated that cats are very tolerant of glucocorticoid therapy, and initial dosages may be as high as 8.8 mg kg per day. However, diabetes mellitus is a potential complication for cats receiving long-term steroid therapy. Some authors recommend other steroids such as dexamethasone...

Indications for chemotherapy

Chemotherapy should be reserved for malignant tumours that are known to respond to cytotoxic drugs and is indicated for widespread or systemic disease. Examples where chemotherapy would be the first line of treatment are lymphoproliferative and myeloproliferative diseases (lymphoma, myeloma and some leukaemias). Chemotherapy is rarely of value as the sole treatment for solid (non-lymphoid) tumours such as carcinomas, sarcomas or melanomas. Here, surgery or radiotherapy would be the first choice...

Squamous cell carcinoma complex

The mainstay of diagnosis of this readily recognised, common skin tumour is the collection of tissue samples for histopathology. The poorly haired, pale and non-pigmented areas on the pinnae, nasal planum and muzzle are susceptible to the influence of ultraviolet radiation and the development of erythema, crusts, ulceration and plaques. These lesions are indistinguishable from the invasive form of SCC and SCC in situ. Multiple squamous cell carcinoma in situ (Bowen's disease) This variant of...

Hereditary primary seborrhoea oleosa in Persian cats

Dirty face syndrome has been compared with hereditary primary seborrhoea oleosa in Persian cats, which is considered to be a primary form of keratinisation defect however, there seem to be no obvious similarities apart from the same breed being affected. The mode of inheritance of the seborrhoea is suspected to be autosomal recessive. Kittens are affected within 6 weeks of age, with generalised mild to severe scaling, a greasy coat and a rancid smell. Alopecia may develop to include most of the...

Harvest mites trombiculids

The six-legged larvae of Trombicula autumnalis are a common seasonal cause of pruritic skin disease affecting cats in certain parts of the UK. The large orange-yellow larvae are present on vegetation in mid to late summer and autumn, particularly in areas of chalk upland. The larvae attach to the host and transiently (3 days) feed on tissue fluid, after which they fall off to complete their life cycle in the environment. Development of a hypersensitivity response to the mite or its products may...

Encephalopathies Encephalomyelopathy of Birmans

This is a disease of Birman kittens, with onset at about 2-5 months of age (Jones et al., 1992). Affected animals show hindlimb paresis and ataxia, which progresses to hindlimb paralysis. Bilateral nuclear cataracts may be present. Affected kittens are usually related and the condition is inherited. The major histopathological features are spongy changes, vacuolation and wallerian degeneration, mainly in the thoracolumbar spinal cord. Diffuse lesions are also present in the brain and other...

Possible influences on fearful behaviour in cats

Cats that are reacting in a fearful manner to stimuli that are not innately fear inducing may do so for a variety of reasons. One of the most common is a lack of appropriate socialisation and habituation, and fearful behaviours highlight just how important it is for kittens to be given the best start in life. The important period of behavioural development is called the socialisation period and in kittens it runs from approximately 2 to 7 weeks of age (Karsh, 1983). During this time kittens...

Sarcoptes mites

The life cycle of the Sarcoptes mite is essentially a 3 week period which involves the laying of eggs on the host deep in burrows excavated by the female. The larvae hatch out and develop into nymphs and thence adults, which may move to the skin surface and may wander to a greater or lesser extent on the skin surface. They may reside in moulting pockets, which are extensions of the tunnels excavated by the gravid female mite. In the epithelium the mites are most likely to feed on tissue fluid...

The peripheral nervous system

Diseases causing peripheral neuropathies may affect motor, sensory and autonomic neurons in the peripheral nervous system. Several congenital, inherited and acquired diseases affect the LMN and there may be significant variation in clinical signs. Involvement of motor fibres usually manifests as muscle tremor, muscle atrophy and weakness. Involvement of sensory nerves results in proprioceptive deficits, ataxia, anaesthesia, hyperaesthesia or paresthesias. Spinal reflexes are depressed or absent...

Miscellaneous conditions Acne

Feline acne is a well-recognised clinical entity with a poorly understood pathogenesis, although the current view is that it represents a form of keratinisation disorder with secondary bacterial infection. Lesions are usually localised to the chin, but may also be located on the upper and lower lips and commissures of the lips (White et al., 1997). Clinical signs may include pruritus, although this is not a consistent finding in some cases the signs of acne are part of a variety of clinical...

Feline atopy

Atopic disease of domestic animals has been defined as the inherited predisposition to develop IgE antibodies to environmental allergens, resulting in allergic disease (Halliwell & Gorman, 1989). The condition in dogs has been thoroughly reviewed by a task force of the American College of Veterinary Dermatology (Olivry etal, 2001). The nomenclature used for the dog ought to be considered for use in the feline condition. The condition of feline atopic disease has been reported and reviewed on...

M ucopolysaccharidosis

The mucopolysaccharidoses are a group of genetic diseases that result from defects in the metabolism of glycosaminoglycans (Thrall, 2001). Two substances Table 7.11 Lysosomal storage disorders of cats Table 7.11 Lysosomal storage disorders of cats Siamese, Korat and other cats 3-6 months Ataxia, head tremors, spastic quadriparesis lipofuscinosis (amaurotic familial idiocy) P-phenylenediamine-mediated peroxidase Globoid cell leucodystrophy (Krabbe's disease) Macrophages (globoid cells) In white...

Demodicosis

Demodicosis has been reported as an uncommon disease associated with a variety of dermatological manifestations, including ceruminous otitis externa localised alopecia, erythema, scaling, crusting and pyoderma of the head, neck and ears and generalised alopecia, erythema, variable scaling, papulocrusting dermatitis and secondary pyoderma. Clinical disease has been reported in cases associated with two species of mite. The long, slender form, Demodex cati, has been reported since the...

Therapeutic protocols for feline allergic skin disease

In many cases the pruritic (and presumed allergic) cat has to be managed with medical therapy because a definitive diagnosis has not been achieved despite measures to implement effective flea control, the pursuit of diet trials and tests for allergen-specific IgE. The clinician is then left with the obligation to try and make the disease manageable without causing problems from adverse drug reactions. The mainstay of therapy for allergic and pruritic cats has been a heavily reliance on the use...

Hereditary noninflammatory myopathies

These are inherited progressive non-inflammatory myopathies. Several are reported in cats and for some diseases the molecular and biochemical defects have been defined. Dystrophin-deficient myopathy is a rare disease caused by an almost total lack of dystrophin, a large protein indirectly connecting the internal cytoskeleton with the extracellular matrix. Dystrophin deficiency is due to a mutation in the dystrophin gene, a very large gene located on the X-chromosome, and is transmitted...

Fibrosarcoma

There are three variants of this type of tumour. Feline sarcoma virus infection may be associated with simultaneous infection with FeLV and the development of an aggressive form of multiple fibrosarcoma in cats less than 5 years of age. The tumours are rapidly growing, firm and often attached to adjacent tissues. Treatment is not recommended and the prognosis for this uncommon tumour is grave. Solitary fibrosarcomas of older cats (> 8 years old) tend to be firm, slow growing and poorly...

Evaluation of the forelimbs thoracolumbar spine hindlimbs and tail

Spinal reflex testing assesses the reflex arc and cord segments in which the reflexes are involved (Table 7.7). All reflexes are modified or co-ordinated by higher centres. The examination of spinal reflexes is best performed when the cat is in lateral recumbancy, gently restrained by an assistant. Flexor reflex abnormalities include areflexia, hyporeflexia, hyperreflexia, clonus and a crossed extensor response. Flexor reflex (withdrawal) The interdigital skin is pinched and the foot observed...

Acquired myopathies

Polymyositis has been associated with infectious diseases (toxoplasmosis and retroviral infections), thymoma and immune-mediated diseases, and may occur concurrently with myasthenia gravis (MG). Toxoplasma gondii may cause myositis in cats. It occurs most frequendy in association with postnatal infection, and there may be associated clinical signs referable to other organ systems, including the eyes and CNS. Serum CK is usually elevated. The administration of corticosteroids or concurrent...

Ischaemic encephalopathy

Thiamine Deficient Cat

Figure 7.12 Ventroflexion of the neck - a cat with thiamine deficiency. (Reproduced from Shaer, 2002, with permission of Manson Publishing.) Figure 7.12 Ventroflexion of the neck - a cat with thiamine deficiency. (Reproduced from Shaer, 2002, with permission of Manson Publishing.) where thiamin has been destroyed by excessive cooking or by the addition of preservatives (e.g. sulfur dioxide). Thiamin deficiency results in abnormal glucose metabolism in the brain, encephalopathy and haemorrhage...

Paraneoplastic syndromes

The skin may be affected in a variety of ways, both clinically and histologically, by underlying disease processes. In paraneoplastic disease a tumour process has an indirect effect on the skin without invading the skin. In recent years several syndromes have been recognised that have cutaneous manifestations for underlying neoplastic processes. The pathogenesis of such syndromes is poorly understood. This syndrome is also termed 'shiny cat syndrome' because of the profound shiny appearance of...

Discoid lupus erythematosus

Although discoid lupus erythematosus (DLE) is well recognised as a dermatological entity in dogs it is rarely reported in cats. There is no apparent age, sex or breed predisposition. Clinical signs consist of periocular crusts, erythema, vesicles and papules on the pinnae, and scaling and crusting of the footpads with focal depigmentation. There may be plaque-like erythematous excoriations involving the pinnae, neck, abdomen and groin, or generalised crusting and scaling. Skin biopsies have...

Complications of chemotherapy

A number of complications can arise while an animal is receiving chemotherapy. Many of the intravenous injectable agents are either irritant or vesicant if perivascular injection occurs and prompt action should be taken (see below). Immediate hypersensitivity reactions can happen with some drugs. Cytotoxic drugs are not specific to tumour cells in their action and normal body tissues that contain a large proportion of dividing cells, such as the bone marrow and the epithelium of the...

Evaluation of posture gait and strength

The patient is observed at rest for abnormalities in body posture and limb position and tone. Increased muscle tone is judged by increased resistance to flexion. The claws are checked for wear and for scars indicating previous trauma. The skeleton is palpated for crepitus, masses, deviation of the normal contour and motion (e.g. fractures and luxations). The muscles are palpated to check for size and symmetry. Abnormal body posture may be due to a congenital or an acquired lesion in the...

Further reading

Allwood M., Stanley A. & Wright P. (eds) (2002) The Cytotoxics Handbook. 4th edn. Radcliffe Medical Press, Oxford. Chun R., Garrett L. & MacEwen E.G. (2001) Cancer chemotherapy. In Small Animal Clinical Oncology. 3rd edn. (eds Withrow S.J. & MacEwen E.G.). WB Saunders, Philadelphia, PA, Chapter 9, pp. 92-118. COSHH Regulations (1988) Approved Code of Practice Con trol of Substances Hazardous to Health and Approved Code of Practice Control of Carcinogenic Substances, 3rd edn. COSHH,...

Malassezia

Malassezia infection in the cat has become a recognised entity in recent years. Malassezia pachydermatis is an opportunistic yeast pathogen that may be associated with significant skin disease. Predisposing factors for its establishment may include alterations in skin microclimate associated with underlying allergic skin disease or chronic glucocorticoid and antibacterial therapy for allergic skin diseases. There may be a breed predisposition for cats with abnormal hair coats, such as sphinx...

Acquired neuropathies

Sacrococcygeal Fracture

Some cats with diabetes mellitus develop a distal polyneuropathy, usually involving the hindlimbs. There is a plantigrade posture, and progressive paresis, hyporeflexia, muscle atrophy and depressed patellar reflexes (Figure 7.14). Some cats are hyperaes-thetic and irritable when handled or touched. Proprioception may be impaired. Most cats are poly-dipsic and polyuric, with fasting hyperglycaemia and glucosuria. Many present with hindlimb weakness but have not been diagnosed with diabetes...

Clinical pathology

Haematology and biochemistry are essential in most investigations. There are many systemic disorders in which neurological signs predominate and that have characteristic clinicopathological changes, for example, hypergammaglobulaemia in, feline infectious peritonitis (FIP), hypokalaemia and portosystemic shunts. Clinical pathology is of less value in the diagnosis of primary nervous diseases. Urinalysis may help occasionally with specific diseases (e.g. glucose present in diabetes mellitus and...

Clinical signs and diagnosis

Ventroflexion Cats

The clinical sign common to all neuromuscular diseases in the cat is weakness. The affected cat is frequently 'floppy', often with ventroflexion of the neck and reduced muscle tone (Figure 7.20). Muscle atrophy is expected, but in some dystrophies (e.g. myotonia and X-linked dystrophy), muscle hypertrophy is present. The severity of the weakness may be variable and muscle involvement can be focal. Disorders of the neuromuscular junction present with varying clinical signs ranging from weakness...

Sacrocaudal dysgenesis in Manx cats

Rectal Deformity Kittens

Manx cats have varying degrees of sacral and or caudal vertebral deformities. Some tailless cats have a normal sacrum, spinal cord and cauda equina. Others show varying dysgenesis or agenesis of the sacral and or caudal vertebrae that may be associated with spina bifida, malformations of the terminal spinal cord and cauda equina. Spinal cord malformations include the absence or partial development of sacral and caudal spinal cord segments or cauda equina, myelodysplasia, meningocele,...

Erythema multiforme and toxic epidermal necrolysis

Erythema multiforme is a rare disease in the cat and is usually associated with drug administration, particularly cephalexin, penicillin, aurothioglucose and sulfadiazine. The disease in humans is associated with drug administration, viral diseases and neoplasia. The pathogenesis of the feline disease may be similar to that observed in the dog, with up-regulation of the expression of major histocompatibility complex class II, CD44 and intercellular adhesion molecule-1 on keratinocytes. CD8+...

Papulocrusting dermatitis miliary dermatitis

The clinical diagnosis of miliary dermatitis is readily made from the observation and palpation of the typical skin lesions of an erythematous papulocrusting eruption along the back, neck and ventrum. The lesions resemble millet seeds and the disease derives its name from this similarity (Plate 6.11). It is possible for the cat to be very pruritic with this condition and there may also be early-stage eosinophilic plaques on the ventrum. Miliary dermatitis is a cutaneous reaction pattern a...

Otodectic mange Otodectes cynotis

This mite is the common cause of otitis externa and pinnal dermatitis in the cat. Otodectes is a free-living surface mite, which lives in the external ear canal where it feeds on epidermal debris and tissue fluids. The mites cause mechanical irritation and there may be a hypersensitivity response to mite and or mite-derived products. The mites are a major cause of otitis externa occasionally they can be found beyond the ear canal, including the head, neck, dorsum and tailhead regions, where...

Organochlorines

The incidence of organochlorine poisoning in the cat has declined significantly, in association with the reduced use of these agents as animal insecticides. Most toxicities in the past related to the intentional or accidental exposure (e.g. contact with sprayed surfaces) of cats to agents such as benzene hexachloride, dieldrin and dichlorodiphenyltrichloroethane (DDT). Cats are generally considered to be highly susceptible to this group of compounds. The mode of action is largely unknown,...

References

Baxby D. amp Bennett M. 1997 Cowpox a re-evaluation of the risks of human cowpox based on new epidemiological information. Arch Virol S13,1-12. Beale K.M. amp Fujioka C. 2001 Effectiveness of selamectin in the treatment of Notoedres cati infestation in cats Abstract . Vet Dermatol 12,237. Beale K.M. amp Rustemeyer-May E. 2001 Selamectin in the treatment of feline Demodex Abstract . Vet Dermatol 12,237. Ben-Ziony Y. amp Arzi B. 2000 Use of Lufenuron for treating fungal infections of dogs and...

Otitis externa

The external ear canal and pinna may be affected in a variety of conditions, including infectious bacterial, yeast and dermatophyte , allergic food allergy, atopy, Otodectes hypersensitivity, contact and drug reactions , parasitic Otodectes, trombiculids, Demodex, Notoedres and neoplastic actinic dermatitis, SCC, ceruminous gland hyperplasia, adenoma and adenocarcinoma, nasopharyngeal polyps . Many of these conditions are discussed elsewhere in this chapter. Signs of ear disease may include...

Mural folliculitis

Mural folliculitis is a term that denotes a new syndrome recognised in cats. The common histological theme is lymphocytic and histiocytic infiltrate of the hair follicle in the outer sheath in the isthmus and infundibular regions. The infiltrate may extend to the epidermis, including neutrophils and eosinophils, and the follicles may be ablated by a pyogranuloma-tous inflammation leading to atrophy. The main presenting clinical signs include generalised alopecia and scaling. There are five...

Idiopathic facial dermatitis of Persian cats

This disease has been termed dirty face syndrome by some clinicians. It is a poorly understood condition that is recognised in the Persian breed only, with no clear underlying aetiology, and provides a considerable challenge to the clinician to manage Bond et al., 2000 . The presenting clinical signs are observed in Persian cats and in an initial case series the age of onset ranged from 4 months to 5 years. The dermato-logical examination reveals black waxy material on the distal portion of the...

Salicylates

Although acetylsalicylic acid can be well tolerated by the cat in carefully controlled dosages, toxicity can arise when owners administer excessively high dose rates at home. The half-life of acetylsalicyclic acid is exceptionally long in feline plasma 3 40 h . As such, the administration of aspirin to cats is normally accompanied by an extended interdosage interval. The clinical signs of aspirin toxicity include vomiting, depression and tachypnoea, with occasional cases also exhibiting an...

Vaccination schedules

Most data sheets recommend primary vaccination for kittens followed by annual boosters thereafter. Such regimens maximise protection for the individual and are generally based on both experimental challenge studies and field data provided by the manufacturer. However, in recent years there has been considerable discussion as to whether such schedules are always appropriate, largely because of concerns about possible safety issues. These issues have been particularly highlighted by the...

Types of vaccine

Cat vaccines generally comprise either modified live, or inactivated killed adjuvanted vaccines administered subcutaneously Table 2.1 . Modified live vaccines have been attenuated or altered to eliminate or reduce their virulence. Attenuation can be achieved in a number of ways, including serial passage in cell culture in the laboratory or by genetic manipulation, or by the choice of a naturally occurring apathogenic strain. Live vaccines have the disadvantage of an increased possibility of...