Skin Conditions
the coat that is the more complex structure of the two. The skin is the largest organ
of the body, and it has a number of functions that are essential for the well-being
of the animal. The skin forms a continuous layer over the body, and it is also
continuous with the mucous membranes of the mouth, nose and genital openings.
STRUCTURE OF THE SKIN
The skin is tough, stretchable and its thickness and structure differ in different
parts of the body. It is thickest where it is most exposed, such as over the footpad
and nose. It is also thicker over the back area (dorsal surface) and sides (lateral
surface) of the body. The skin is thinnest over the ear flap, thorax, abdomen (ventral
surface) and inner surface of the legs. Compared with human skin, the skin
of the dog or cat is rather fragile. Without the protective cover of hair, its total
thickness may be less than 1 mm in places on the body. The skin is composed of
three layers (Fig. 5.1) and these are described below.
Epidermis
This is the non-vascular (i.e. lacks blood vessels) cellular layer composed of
stratified epithelium. It is of varying thickness and forms the outer covering of the
body. The epidermis consists of four layers of cells, from the basal layer, which is
the deepest, to the top keratinised layer (Fig. 5.2).
In the basal layer (stratum basale or germinativum), the cells divide rapidly.
The melanocytes are found between the cells of this layer. These cells are responsible
for colour, as they contain the skin pigment melanin (in varying amounts).
Heredity is the main factor that influences the colour of skin but, as with humans,
sunlight and some hormones can also affect the skin colour. If melanin is not
present the condition is called albinism and the animal may be called albino.
The next layer, known as the spinous layer (stratum spinosum), is one to two
cells thick. It is thicker in body regions which undergo hard wear, such as
footpads in dogs. Next is the granular layer (stratum granulosum), so called
because the cells have granules in the cytoplasm. It is in this layer that cells begin
to die as they gradually move to the surface. Keratinisation begins in this layer as
keratin, a fibrous protein, hardens the texture of the cells. In areas of hard wear on
the body a clear layer is also found here. This layer gets its name from the loss of
the cell nuclei and the tightly packed cells.
The top layer (stratum corneum) is made up of flat, cornified cells (dry scales),
overlapping each other. If the scales remain intact, this top layer of cells prevents
the entry of harmful materials. Keratinisation is completed here and gives the special
epidermal parts of animals (hooves, beaks and hair) their strength. Dead cells
from this layer are continuously sloughed off as dandruff or scurf, and replaced
by new cells that come up from the basal layer.
Dermis (corium)
The dermis is made up of dense, fibrous, elastic, connective tissue, which contains
blood vessels and nerves. The dermis also has bundles of involuntary muscle,
called the arrector pili. These are attached to hair follicles, and when they contract,
the hairs become more erect. The effect of this action is to increase the animal’s
insulation in cold weather. This involuntary muscle contraction has another function,
seen in the sympathetic nervous system reaction ‘fight or flight’ – when the
animal raises its ‘hackles’ (the hairs along the back and neck) it presents a larger
and more frightening shape to an opponent.
Also found in the dermis are the sebaceous glands, sweat glands, and nerves
which send information about sensation of touch, heat, cold and pain.
Hypodermis (subcutis)
The hypodermis contains connective tissue and fatty (adipose) tissue, allowing
the skin to move over deeper structures without tearing or damage.
FUNCTIONS OF SKIN
Protection
• The skin acts as a barrier between the internal body environment and the external
environment.
• It prevents entry of micro-organisms.
• It protects underlying structures from injury due to loss of water, mechanical
trauma and ultraviolet light.
• It protects against absorption of toxic or harmful substances.
Production
• The skin produces vitamin D, which is required for the absorption of calcium
from the intestines.
• Sebum is produced in the sebaceous glands and forms a water repellent layer
over the skin, and also helps to control bacterial growth.
• The skin produces sweat, which assists in the removal of some waste products.
• Pheromones are produced from special scent glands, and are meant for communication
with other animals for reproductive or territorial purposes.
• Milk is produced in the mammary glands.
Sensory
The skin is a sense organ with nerve receptors for touch, temperature, pressure
and pain scattered throughout its surface.
Storage
The skin stores fat as adipose tissue. This is the body’s energy store and serves as
an insulation layer to help maintain body temperature in cold weather.
Temperature control (thermo-regulation)
• For losing heat the walls of the surface blood vessels widen (vasodilation) and
sweat formed in the skin glands assists in the loss of water and salts by evaporating
and cooling the skin surface.
• For gaining heat the walls of the surface blood vessels constrict or narrow
(vasoconstriction), and erection of hairs traps a layer of air warmed by the skin
for insulation.
• The fat layer (adipose tissue) under the skin also helps in the insulation of
the body. It is situated in the subcutaneous layer called the hypodermis
(see above).
Communication
• Pheromones. These are scents produced by special skin glands and used for
communication with other animals, such as to attract another animal for reproductive
purposes.
• Visual communication or camouflage involves the coat colour or pattern.
• In response to a threat or an attack, the coat hairs will become erect (raising its
‘hackles’) so that the animal appears to be larger. These hackles are seen especially
in the neck and spine area.
SKIN GLANDS
Glands in the skin produce a variety of secretions:
• Sebaceous glands surround the hair follicles and secrete sebum, whose function
is to form a thin, oily, water-repellent layer over the skin surface (Fig. 5.3).
It gives the coat hair a shiny glossy appearance and helps to prevent bacterial
growth on the skin’s surface, which might in turn lead to infection. Some noncastrated
cats may develop a greasy matting of the fur at the base of the tail due
to overactive sebaceous glands, called a stud tail. This over-secretion of the tail
glands is normal in some male dogs and is seen as greasy deposits on the skin’s
surface, often with a distinctive rancid smell. Wire-haired breeds of dog are
particularly susceptible to this, e.g. West Highland White Terrier.
• Apocrine sweat glands open either into the hair follicle or onto the skin’s surface.
Their secretions do not help with control of body temperature nor do they
allow moisture loss. These secretions contain some waste from the body, hence
their smell is used by cats in particular to mark their territory. In dogs these
glands are concentrated in regions such as the anal sacs. A particular dog/cat
odour is produced when the secretions are broken down by bacteria in the
skin’s surface.
• Eccrine sweat glands, useful for body cooling, are found only on the footpads
and nose of both dog and cat.
• Anal glands or anal sacs are found on either side of the anus, positioned at
4 o’clock and 8 o’clock. Their secretion has an unpleasant smell and is thought
to be a pheromone for marking territory. These sacs are intermittently emptied
by the animal when passing faeces (see Fig. 3.11, Chapter 3).
• Mammary glands are modified skin glands and their function is to produce
milk (Fig. 5.4). They are a feature of mammals and are found on the surface of
the abdomen. Normally, the dog has five paired glands and the cat has four
paired glands. The glands are present in both male and female animals but only
enlarge with milk at the end of pregnancy.
NAILS, CLAWS AND FOOTPADS
Nails and claws
Nails and claws are modified or specialised epidermis (outer layer of skin),
covered by a fold of skin. They are beak-like in shape, growing in two sheets
which form the walls of the claw. In the middle of the nail or claw is the dermis,
which contains a blood vessel and nerve between the last bone of the toe and
the horn of the nail/claw. The sole, the part that the faces the ground when the
animal is standing, is a soft flaky horn, with the wall of the nail/claw sometimes
meeting and covering it (Fig. 5.5). The functions of nails and claws include:
• Bearing the weight of the animal and so assisting in movement.
• Obtaining food.
• Fighting, especially in cats.
Each of the four toes or digits of the animal’s foot has a nail or claw, and some
dogs may have a fifth toe on the inside surface of the lower leg known as the dew
nail. The cat has a fifth toe on its front feet only. Claws usually wear down by
weight bearing on hard surfaces (e.g. walking on pavements). Cats’ claws are
narrower than dog nails and are usually kept pulled back, off the ground, in the
skin fold by ligaments. The claws can be quickly unsheathed by muscular action
when required. Fig. 5.6 shows a typical dog and cat foot.
Footpads
A footpad forms the weight-bearing surface of the animal’s foot. The footpad
consists of specialised hairless skin, which is thick and normally pigmented and
sweat glands are present. Under this is the toe or digital cushion made up of fatty
or adipose tissue and a good blood supply. The pad is oval or heart shaped,
depending on location in the dog, and is more rounded in the cat. The cat also has
a single carpal pad which lies above the other pads on the foot. The pads give
support to the feet and act as shock absorbers when running on all sorts of
surfaces and landing from a leap or jump.
COAT GROWTH
Hair is an epidermal structure and its growth is controlled by:
• Seasons
• Environment
• Nutrition
• Hormones
In carnivores, the rhythm of shedding occurs independently in each hair follicle.
The coat is thickest in winter, and normally some shedding occurs in spring
and summer (animals living in a house may shed hair all year due to the central
heating simulating summer). The pattern varies from breed to breed. In some
breeds, such as the poodle, the hair grows continuously and needs regular clipping
whereas in short haired breeds of dog new hairs grow and old ones are shed.
Hair growth is slow in summer, the rate increasing as the temperatures gets
cooler in autumn and winter. During active growth, about 1 mm of hair shaft
grows per week but this can be affected by hormonal changes. Once a hair stops
growing it dies while it is still in the follicle. After that it can be shed from the skin
at any time, and another hair is produced from the deep epidermal cells.
Dog and cat coats consist of ‘guard’ hairs with clusters of two to five compound
follicles, each containing approximately three coarse primary hairs, which are
larger and stiffer, with 6–12 secondary hairs, which are smaller and softer and are
called under-hairs. There are common openings on the surface of the skin for the
groups of hairs. The compound follicles cover most of the skin surface, and the
arrangement and pattern varies from breed to breed. The number of hairs in a
group varies with the type of hair coat. For example, in the Labrador retriever
each group consists of a central primary guard hair and a number of thinner
secondary hairs which form the undercoat, but in the Boxer, the coat consists
of many small primary hairs and little undercoat. Generally, on the dorsal and
lateral sides of the dog and cat there are many hairs, giving a thick coat; however,
the coat on the abdomen is much thinner, as also under the tail and the inner
surface of the flank. In some breeds there are no hairs or only a few in the anal
region or on the testicles.
Formation of a hair
The hair growth cycle has three phases:
(1) Anagen: This is the most active stage of hair growth. The epidermis thickens
(Fig. 5.7) and starts to grow into the dermis below (Fig. 5.8). This is the
hair papilla. Epithelial cells produce a hair cone which later forms the actual
hair (Fig. 5.9). Once a hair has reached its optimum length, it stops growing
(Fig. 5.10).
(2) Catagen: The fully grown hair is still attached to the papilla (Fig. 5.10).
(3) Telogen: The papilla contracts, loosening the hair (Fig. 5.11) and begins to
grow a new one (Fig. 5.12). The old hair is frequently pushed out by the new
growth.
The three phases occur in different parts of the body at different times of year.
Coat hair moults in spring and autumn and this lasts for about six weeks. The new
coat hair is fully in place after four months.
Not all breeds of dog and cat follow this cycle. These breeds are called non-shedding
breeds, e.g. Poodle and Rex cat.
Functions of coat hair are:
• Protection from injury
• Insulation in cold weather
• Colour/identification of a breed
• Sensory
Specialised or sensory hair is also called tactile hair, e.g. lower and upper
eyelashes (superciliary and cilia), external ear hair (tragic or tragus), and whiskers
on the muzzle (vibrissae). These hairs are more than twice as thick as guard hairs
(Fig. 5.13). All the special hairs have deeper follicles with greater blood and nerve
supply. When the animal moves between objects the hairs act as sensory organs
and pick up information (pressure or touch) to indicate the position of the
head and therefore of the body in relation to a given space for safe passage of the
animal.
Both the coat and skin can be affected by disease, age, nutrition and parasites.
Compared with other body organs, the skin is able to show a variety of signs and
symptoms of ill health. These skin changes in themselves are not always of assistance
in diagnosing the underlying disease because some diseases have similar
symptoms. However, a change in the coat and skin condition is significant and
should be reported so that veterinary investigations can be carried out.
Parasites, both internal and external, contribute to ill health in the animal host.
Serious illness is rare but in cases of worm burden the host animal may appear
unthrifty, i.e. the animal shows poor growth and anaemia.
PARASITOLOGY
A parasite lives in/on another living body and benefits by obtaining its nourishment
from the host. The host can be any species, e.g. human, dog, cat, mouse
or bird.
Terminology
• Transport host: This transports the parasite to the next host. No development
takes place in the parasite.
• Paratenic host: It is same as transport, but the parasite must be eaten by this host
in order to be excreted and passed on to the next host.
• Intermediate host: Some parasites must spend time in this host in order to enter
their next life cycle stage.
• Final host: In this host the parasite completes its development.
• Permanent parasite: This parasite goes through all life stages and lives on one
host.
• Temporary parasites: These move from host to host.
• Endoparasites: These live inside the host’s body.
• Ectoparasites: These live on the surface of the host’s body.
The parasite feeds on the host, but does not deliberately kill its host as this
would destroy its food source. However, some hosts may die as a result of the
parasite’s feeding activities or from toxins released by the parasite. To prevent
disease or death of the host animal, control of parasites is important. Control in dogs
and cats aims to remove completely all parasites, whether internal or external.
Many easy to use and effective products are available for removing external
parasites such as fleas, lice and ticks. These use a residue effect which lasts
for varying periods of time. The products for eliminating internal parasites are
collectively called wormers (anthelmintics).
Life cycles of common external parasites
The flea (Ctenocephalides; Fig. 5.14)
The flea (Ctenocephalides; Fig. 5.14)
Fleas live mainly around the neck, ears, tail and abdomen and can cause the host
animal to scratch and self-mutilate in an attempt to reduce the itching. Fleas feed
exclusively on the blood they draw from the host animal. Flea faeces can be seen
on the skin of affected animals as black hard dirt. If some of the black dirt grains
are placed on a wet tissue the dried blood soon stains the tissue red. Many animals
are allergic to flea saliva and this is manifested as irritation, scratching a specific
area, inflammation and hair loss. Fleas are not host specific and will feed on
any available host, including humans! Fleas are the intermediate host for the
tapeworm, Dipylidium caninum, therefore worming may also be applicable when
treating the host for a flea problem.
Life cycle
• Flea eggs hatch in 1–2 days.
• Flea larvae feed for 4–8 days (in carpets or bedding).
• The larvae spin cocoons, and adults emerge in five days or less.
• The adult flea cycle may take only three weeks; however, if the environment is
not friendly (no host animal available) the larvae can remain unchanged for
months before further development. Adult fleas can live for two years without
feeding if food is unavailable.
The tick (Ixodes)
The tick will drop onto or climb into a host animal’s coat and bury their mouth
parts into the skin. They feed until engorged on the host blood before dropping on
the ground. When engorged they appear grey to brown and are approximately
pea sized. The adult tick (Fig 5.15) can live for two years without feeding.
Life cycle
• The engorged female can lay 1000–3000 eggs
• Larvae hatch in 30 days
• Nymphs emerge from moulted larvae
• Adult ticks emerge after 12 days, and immediately start to look for a blood
meal
Feeding is required between each stage of development. When attempting
to remove a tick, care must be taken not to pull the body leaving the mouth
parts attached.
Diseases are transmitted by the tick to other host animals through its saliva and
include:
• Lyme disease: This is a bacterial tick-borne infection caused by Borrelia burgdorferi.
The bacteria can cause skin discoloration, cardiac and joint disease in
the infected animal. It is endemic in a number of states in the USA. In Europe,
the bacteria are also borne by ticks of host wildlife such as rodents and deer.
Signs of Lyme disease include:
(a) sudden onset of lameness with arthritic pain in one or more joints
(i.e. carpal or wrist joint), which may last only a few days and recur at
intervals
(b) high temperature with enlarged surface lymph nodes.
• Ehrlichiosis: This is caused by a parasite which lives inside certain white blood
cells. It is transmitted by ticks during feeding on the host animal’s blood. It is
found in the Mediterranean basin in Europe and other Mediterranean countries.
The severity of the disease and recovery of the host animal depends on the
ability of its immune system. Certain breeds of dog are particularly susceptible
to the disease, e.g. German shepherds. Babesiosis may also be present, having
been passed by the tick at the same time. Signs of ehrlichiosis include:
(a) high temperature and inappetence
(b) enlarged lymph nodes
(c) bleeding from the nose and under the skin
(d) anaemia.
• Babesiosis: This is caused by a protozoon which develops and multiplies in
tick salivary glands and it is transmitted to the host animal during feeding.
It is endemic across much of Europe. The parasite protozoa infect red blood
cells. The severity of the disease varies depending on the species and strain
of Babesia and the health status of the animal infected. Signs of babesiosis
include:
(a) pale mucous membranes
(b) anaemia
(c) breathing problems and collapse.
Lice
There are two types of louse:
• Biting lice are visible to the eye and can be seen walking around on the skin
when the coat hair is parted (5.16). They feed mainly on hair and dead skin
(epithelial) cells of the host animal. Trichodectes canis, which infests dogs, is
also one of the intermediate hosts for the internal parasitic worm Dipylidium
caninum. The species infesting cats is called Felicola subrostratus.
• The sucking louse, Linognathus, infests dogs and feeds off the blood of the host
animal (Fig. 5.17).
Lice are permanent parasites, spending their entire life cycle on the host.
During their lifespan of about a month, the adult female will lay up to 300 eggs.
The eggs are known as nits and they stick (are cemented) to the hair shaft of the
host’s coat hair.
Life cycle
• Eggs are laid and are cemented to the coat hair.
• Three stages of nymph emerge (seen as smaller versions of the adult louse).
• Adults emerge three weeks after the last nymph moult.
Lice cause intense irritation and inflammation, and the host animal often selfinflicts
skin injury during scratching. Severe infestations of lice may result in ill
health and anaemia in young or weak animals, particularly if the blood-sucking
louse Linognathus setosus is present.
Mites
Sarcoptes (Fig. 5.18)
The fertilised female burrows into the epidermis of the skin feeding on fluid from
the damaged tissue, causing pain to the host animal. Sarcoptic mange is seen
as intense inflammation and self-inflicted injury to the area, and results from
scratching by the host animal. Crusts form in the bite area and hair is lost.
The areas most frequently affected initially are the edges of the ears, muzzle,
face and elbows but later the rest of the body may become involved. Sarcoptes will
infest humans and is manifested as itchy mosquito-like bites especially around
the waist.
The sarcoptic mite may live for only 3–4 weeks in total. Its life cycle is as
follows:
• Eggs are laid in tunnels within the epidermis of the skin.
• Larvae hatch in 3–5 days, crawling onto the skin surface to burrow into just the
surface layers of skin forming ‘moulting pockets’.
Demodex canis (Fig. 5.19)
Demodex is a long, cigar-shaped mite with short, stubby legs, living in the hair
follicles and sebaceous skin glands of most mammals. Transmission between
animals occurs only within the first few days of life between mother and young
during suckling. The whole life cycle of Demodex is spent in the hair follicles or
glands. It is also known as sub-surface follicular mite.
Demodex is seen in animals which become stressed or debilitated for any
reason. Early signs of infection are some hair loss (alopecia) on the face, particularly
around the eyes, and the forelegs. The skin often becomes noticeably
thickened. There are two forms of infection:
• Mild, seen as skin inflammation, thickening and hair loss.
• Severe, with moist and dried discharge of serum and pus, a lot of inflammation
and hair loss.
Cheyletiella (Fur mite; Fig. 5.20)
Cheyletiella, visible to the eye, is a permanent parasite, spending its entire life cycle
on the host animal. It is host specific, but can affect humans. The mites live mainly
on the surface of the skin and feed off epithelial skin cells, tissue and cellular fluid
from the host. The host animal often has an allergic reaction to the mite saliva. Its
life cycle is as follows:
• Eggs are laid and cemented to coat hair similar to lice.
• Eggs hatch into six-legged larvae.
• These moult into eight-legged larvae.
• Adult stage is reached.
Cheyletiella cause skin irritation seen as excessive scurf or dandruff in the coat of
the infected host animal. It is often referred to as walking dandruff and can affect
both dog (Cheyletiella yasguri) and cat (Cheyletiella blakei).
Otodectes cynotis (Fig. 5.21)
Otodectes is also known as ear mite. It is not host specific and will infest cats, dogs
and other small animals. The mites are found mostly in the external ear canal but
may also occur around the tail and feet areas. They feed off the protective layer of
wax in the host animal’s ear canal, often damaging the canal lining. Otodectes is a
permanent parasite spending its entire life cycle on the host with a life cycle of
approximately three weeks:
• Eggs are laid.
• Larvae form.
• Two stages of nymph.
• Moulting to adults.
Otodectes mites cause head shaking and ear scratching. On examination of the
ear canal a brownish, waxy secretion is seen in the ear canal. Often inflammation
and bacterial infection is seen due to the damage caused to the lining of the canal
by the feeding mites.
Trombicula autumnalis (Harvest mite; Fig. 5.22)
Harvest mites normally become a problem for a host animal in late summer and
early autumn. The larval form of the mite attaches to the legs of a passing dog or
cat. It is this form that is parasitic to both animals and humans and therefore not
host specific. The mite is transmitted by direct contact of the host animal with
foliage in fields or heavy undergrowth where the larvae crawl on hatching. They
are bright orange and round in shape before feeding and have three pairs of legs.
They localise on the ears, muzzle, feet and legs of the host to feed. The larvae bite
the skin surface and inject an enzyme which will start to digest the host tissue
enabling feeding by the mite. This causes inflammation and irritation for the host
and is seen as self-trauma to the area as a result of scratching. The larvae feed for
up to 15 days before dropping off to enter the nymph stage before the adult form.
Life cycles of common endoparasites
Endoparasites live inside the host animal. Most dogs and cats will have had
worms of some sort during their lives. Routine treatment with wormers
(anthelmintics) through the year by the owner will ensure that there is little sign
of worms or inconvenience caused to the host animal. Host animals become
infected by swallowing an egg or larval form of the endoparasite. The common
endoparasites can be divided into two groups.
Roundworm (ascarids)
Roundworms have an un-segmented body with one alimentary tract (Fig. 5.23).
The adults are yellow/white in colour and both ends are pointed. The adults live
in the intestines of the host, feeding on digesting food in the gut. Female worms
produce thousands of eggs which are passed during defaecation. These eggs are
sticky therefore will attach to the feet and coat of animals, often being swallowed
during grooming. The roundworms that infest dogs are Toxocara canis and
Toxascaris leonina, and those that infest cats are Toxocara cati and Toxascaris leonina.
Toxocara canis is transmissible to humans (zoonotic agent) and can migrate
in human tissues. It is linked to blindness and the disease in humans is called
toxocariasis.
Tapeworm (cestode)
Tapeworms have a flat, segmented body and each segment is independent, with
its own alimentary tract (Fig. 5.24). They attach by the mouth to the intestinal wall
of the host animal. Worm segments break off and are passed out with faeces, often
attaching to the hair around the tail region of the host. They look like mobile
grains of rice and cause considerable anal irritation. Fleas are the usual intermediate
host for the worm eggs in the life cycle of the tapeworm. Dipylidium caninum
infest dogs and cats and Echinococcus granulosa infestation is linked to dogs fed
on raw meat. This tapeworm infests humans as a zoonotic agent and causes the
disease hydatidosis or hydatid disease.
Other worm types in the dog and cat include whipworm (Trichuris vulpis) and
hookworm (Uncinaria stenocephala).
An animal with worms will not always show signs of infestation. The following
signs appear only if the infestation overwhelms the resistance of the host animal:
• Anal irritation, seen as scooting on bottom
• Constantly hungry, eating but losing weight
• Vomiting and diarrhoea
• Unhealthy, dull coat
• Enlarged abdomen (seen particularly in young animals)
Prevention of worms
• Worm animals regularly
• Control the intermediate hosts (flea and lice)
• Dispose of faeces immediately
• Disinfect where faeces have been
• Always wash hands thoroughly
• Wash animal bowls separately from human utensils
• Do not let animal lick face
• Keep animal’s anal area clean
• Examine faeces regularly for signs of worm infestation
Other internal parasites
Protozoa
These are single-celled animals and range in size from microscopic to just visible
to the naked eye. Prozotoa form a cyst at some point in their life cycle that enables
them to pass from host to host and to survive temporarily outside a host animal.
The diseases caused by protozoa include:
• Toxoplasmosis: This is caused by Toxoplasma gondii. Dogs (and sheep) normally
become infected by eating contaminated cat faeces. Toxoplasma is linked to
cats as the carrier. The cyst form is passed in their faeces which can then affect
any species. It causes a zoonotic disease in humans and is particularly harmful
to the unborn child during pregnancy.
• Coccidiosis: This is caused by Coccidia and results in diarrhoea in dogs who
become infected after drinking contaminated water or when housed in
crowded conditions.
• Leishmaniasis: This is caused by a protozoon which is transmitted by the
Sand fly. It is endemic in the Mediterranean basin, the Middle East and many
sub-tropical and tropical regions of the world. The parasite invades the white
blood cells first then other body tissues. It is a zoonotic agent and the parasite
has an incubation period which may be extremely long. Clinical features
include weight loss, skin disease, joint pain, intermittent fever and kidney
damage.