A
single virus cell is composed of an outer coat of protein which is called the capsid;
this encloses the nucleic acid (either DNA or RNA) inside it. Sometimes
they have a further membrane of lipid, referred to as an envelope that surround
the protein and they may also have a tail section. In general, a virus cell is much smaller than a
bacteria cell is, most viruses are between 20 and 300 nanometres, while a
bacteria cell is roughly 50,000 nanometres.

Routes of transmission

The
main way viruses are transmitted is through droplets like mucus from coughing,
sneezing or spitting. As soon as they have entered the living host, they start
the process called replication;

The first stage to this is the attachment; the virus starts
to bind to the surface of the hosts cells. After the virus has bound to the
cells it begins the next stage, Penetration, this is where the nucleic acid
enters the cells. The next stage to this process is Synthesis of new components,
once the nucleic acid has entered the cell it takes control of the cell metabolism
which stops the cells normal nucleic acid and protein synthesis. Assembly is
the next stage of the transmission process and almost the final stage; it makes
whole virus particles, once the nucleic acids are fully surrounded by protein
coats. The final stage is called release, this is when the cell has been
overtaken by the virus particles and bursts open, so the virus is then passed
into the bloodstream.

 

 

How they grow and reproduce

It is only possible to reproduce while the virus is
inside the cells of their host, which is destroying the cells in the process. The
virus starts by entering the host’s cells and then starts to produce hundreds
of thousands of copies of itself, after the virus produces so many copies and
fills up the cell, it will burst and the virus will then be passed through and into
the host’s bloodstream.

Animal viruses can be grown in natural growth
vessels such as eggs, they have a sterile interior that is full of cells and
nutrients the virus needs to grow and thrive. If a very small hole can be made
the virus can be injected through it, eventually it will begin to multiply.

Canine
Parvovirus

Symptoms

Symptoms of the Canine Parvovirus include lethargy,
depression, loss or lack of appetite then followed by a sudden onset of high
fever, vomiting, diarrhoea and anorexia.

Transmission

Parvovirus can be transmitted
in discharge from an infected dog, especially in their faeces or vomit; it can
withstand wide temperature changes and most cleaning products.
Parvovirus can be brought into your home and transmitted to your dog via
your shoes, hands and even flies or birds. Canine Parvovirus is a type of
virus; it is shed in the faeces of infected dogs around 4 or 5 days after
exposure, throughout the period of the illness and for 10 days after clinical
recovery. The infection is transmitted through oral or nasal contact with
faeces that contain the virus or through indirect contact with virus-contaminated
objects or materials

What does Canine Parvovirus do to the body cells?

Once the virus has entered the dog, the CPV needs to find cells
that are rapidly dividing in order to successfully cause and spread the disease,
and then virus then tends to start by attacking the tonsils or lymph nodes in
the throat. Once the CPV is in the bloodstream, the virus then begins to target
the rapidly dividing cells, mainly targeting in the bone marrow and in the
cells that line wall of the small intestine.

How does Canine Parvovirus grow and reproduce?

Once they are inside the lymph nodes, the virus usually
begins to invade the lymphocytes (which are a type of white blood cell) for one
to two days, and then creates many copies of itself. Once it has created the copies
it then hitches a ride on the lymphocytes to travel into the bloodstream
because the lymphocytes shelter the virus from the host’s defences. When the
virus reaches the bloodstream, it begins to target the rapidly dividing cells
again, mainly targeting the bone marrow and in the cells, that line the walls
of the small intestine.

 

Feline
influenza

Feline influenza is similar to flu in humans, with similar
effects and symptoms. If the cat is healthy it should be able to fight off the
infection with medical support, however in kittens and older cats, the
infection might harm them the most and proving fatal in some cases.

Symptoms

Symptoms of Feline influenza are usually that the cat seems
lethargic, depressed, have a high temperature, lack of appetite and discharge from
its eyes and nose.

 

Transmission

Feline Influenza (cat flu) is an infectious disease that
affects the upper respiratory tract. Direct contact with an infected cat can
lead to infection however coughing and sneezing releases the virus into the air
so sometimes direct physical contact is not required for the virus to be
spread.

What does Feline influenza do to the body cells?

Once Influenza is introduced into the respiratory tract, it
attaches to and replicates in epithelial cells, the virus replicates in cells
in both the upper and lower respiratory tract, the viral replication combined
with the immune response to the infection leads to destruction and loss of
cells lining the respiratory tract. Once the virus infects the respiratory
epithelial cells, the single-stranded RNA of the influenza virus is recognised
by receptors. The receptor induces the production and activation of antiviral
host Reponses. However, the virus can escape from the innate immune response by
using NS1 to interfere with the signalling. NS1 is a non-structural protein
which inhibits the production of interferon synthesis, allowing the virus to
overcome the hosts defence system.

 

How does Feline influenza grow and reproduce?

For the virus to survive, they must reproduce while they are
inside living cells. The genetic material from an infecting virus takes over
the functions of the host cell to make millions of new virus particles, the new
viruses leave the host cell by bursting out of the cell or by budding out from
the cell surface. Proteins on the virus attach to specific receptors on the
surface of a host cell. The virus may enter the cell by being engulfed by the
cell membrane or by fusing into the cell membrane

 

 

 

 

 

 

 

 

 

 

 

Fungal
Disease

Structure

A fungal cell is made up of a cell wall, which is a rigid structure that provides the cell with support and protection.
The cell wall structure also helps to prevent over-expansion when water enters
the cell.

The cell
membrane, which is a biological membrane
that separates the interior of the cell from the outside environment. The basic function
of the
cell membrane is to protect the cell from its surroundings.

The cytoplasm is a gel-like substance
that fills cells. The cytoplasm contains and supports the cell’s organelles,
transports genetic material within the cell and it also serves as a buffer
protecting the cell’s organelles and genetic material from damage due to
movement or collisions with other objects.

The endoplasmic reticulum is a type of organelle found
in eukaryotic cells that forms an interconnected network of flattened,
membrane-enclosed sacs or tube-like structures known as cisternae.

The Golgi
apparatus receives proteins and lipids
(fats) from the rough endoplasmic reticulum. It modifies some of them and
sorts, concentrates and packs them into sealed droplets called vesicles.

A Vacuole is a membrane-bound organelle that is present in all plant and fungal cells and some animal and bacterial cells. The organelle has no
basic shape or size and its structure varies according to the needs of the cell.

 

The cell
nucleus ?is a structure in
every cell that contains its hereditary information and controls everything
that happens in the cell including its growth and reproduction.

 

How they grow and reproduce  

Fungi can reproduce sexually and asexually. They form
cells called spores, each fungi cell grows a single spore. These spores are neither
male nor female but like sperm or egg cells, they only contain one set of
chromosomes. The spores then germinate into long fiber cells that are called
hyphae, once two hyphae’s meet the cell and nuclei fuse together. This results
in a new set of chromosomes. The cells continue to divide which causes a thick
layer of hyphae to form, called mycelium.

 

 

Impacts of different environment conditions on their
growth/reproduction

Heat affects the growth of the fungi via the chemicals in the fungi
cells, for the best growth, the temperature needs to be in a range that allows
the chemical reactions to work best in the cell. However, after the temperature
increases above the ideal range, the chemical reactions will become less
efficient and the growth of the cell will begin to slow down. Once the
temperature gets to a high enough point, the cells will stop their growth and
eventually become damaged.

 

Microsporum
Canis (M.canis)

Microsporum canis is a pathogenic fungus, it affects the
upper and dead layers of skin on domesticated cats, and sometimes dogs and
humans. The infection occurs on the scalp and body sites, creating highly
inflammatory lesions associated with hair loss.

The secretion of keratinolytic protease causes some damage to
the skin and hair follicle. The skin will have a hypersensitive reaction
becoming inflamed, which causes the fungus to move away from the site to normal
skin. This creates characteristic circular lesions with healing at the centre
and inflammation at the edge.

Symptoms

The symptoms to look for include a poor coat, red skin,
dandruff, scratching, hair loss and blister-like lesions.

Transmission

Microsporum Canis is highly contagious and can be transmitted
via direct or physical contact, or through indirect contact with the
fungus-contaminated materials like brushes, furniture, linens etc.

What does
Microsporum Canis do to the body cells?

Microsporum Canis Is found on the skin and in the fur,
usually in domestic cats but is sometimes found in dogs and horses too. The fungus reproduces asexually and has thick cell walls that are
rough in texture.

How does Micrsporum
Canis grow and reproduce?

The animal’s immune system usually stops the fungus, however
when a dog has the disease, or if on medication, the body is weakened and
cannot fight the fungus on its own. The spores are very resistant when not
given treatment, they can live up to two years. Spores attach to the skin and
begin to grow and produce hyphae (nutrient absorbing filaments), these then
grow in the dead layers of the skin, hair or nails.

 

Aspergillus spp.

Aspergillosis is an opportunistic fungal infection caused by
the aspergillus, a species of common mold that is found throughout the
environment, including dust straw, grass clippings and hay. An “opportunistic
infection” occurs when an organism, that does not usually cause disease,
infects an animal. However, aspergillosis infects the animal because the immune
system is weakened from another disease.

Symptoms

Symptoms of nasal aspergillosis include sneezing, nasal pain,
bleeding from the nose, reduced appetite, swollen nose and long-term nasal
discharge which may contain mucus, pus or blood.

Transmission

There are two types of aspergillus infections, the first is
the nasal form, and this infection is localized in the nose, nasal passages and
front sinuses. It is believed that it develops from direct contact with fungus
through the nose and sinuses. For example, if a dog is outside and is around
dust or grass clippings, the fungus may enter through the moist lining of the
nose.

The second type of the infection is disseminated, meaning
that it is more widespread and is not only located in the nasal area, it is not
certain how disseminated enters the body. 
Acute invasive aspergillosis occurs when the immune systems fails to
prevent Aspergillus spores from entering the bloodstream. Without the body
mounting an effective immune response, the fungal cells are free to disseminate
throughout the body.

What does Aspergillus spp. do to the body cells?

One of the characteristics of all fungi diseases are the
nutritional strategies, the organisms secrete acids and enzymes into its
surrounding environment which then break down polymeric molecules down into
simpler ones that can then be absorbed back into the fungus cell.

 

 

 

 

 

 

 

 

Bacterial
Disease

Structure

Bacterial cells are much
smaller than plant or animal cells, they have a cell wall which is similar to a
plant cell wall, only more flexible. Bacteria cells do
not have a nucleus.

Bacteria cells have two types
of DNA; plasmid and chromosomal. The chromosomal DNA carries most of
the cells genetic information and plasmid DNA forms small loops and carries
extra information. Some bacteria have a flagellum which is a whip like tail that helps
the bacteria to move itself along.

Routes of transmission

 

Impacts of different environment conditions on their
growth/reproduction

Food impacts the growth and reproduction of the bacterial
cells because there is adequate nutrition available that help to promote the
growth of the microorganisms. Foods such as meat, eggs, milk and fish are all
rich in protein, therefor are the most vulnerable.

The acidity is another condition that impacts the growth and
reproduction because the foodborne pathogens require an acidic pH level between
4.6 and 7.5, the best pH level for them to thrive in is between 6.6 and 7.5.

The temperature of the foodborne pathogens impacts their
growth and reproduction; they grow best between the temperatures of 41 to 135
degrees Fahrenheit.

Oxygen is another environmental condition that affects the
reproduction and growth. Almost all foodborne pathogens require oxygen to grow.

Moisture is an environmental condition affecting the growth
and reproduction, water is essential for the growth of foodborne pathogens, the
water activity (aw) is a measure of how much water is available; it is
measured on a scale of 0 to 1.0. Foodborne pathogens tend to grow best in the aw of between
0.95 to 1.0.

 

Salmonella

Salmonella invades the healthy tissue of the host and begins
by reproducing and colonising. It then produces extracellular substances which
help with invasion, giving the bacteria a chance to overcome the natural
defence from the host.

 

Symptoms

The symptoms of Salmonella develop diarrhoea, fever and
vomiting. These symptoms usually occur 12 to 72 hours after infection.

Transmission

Being infected with the Salmonella enterica bacteria mainly
occurs via ingestion of contaminated foodstuff, grass, wild birds and rats. Occasionally food handlers also transmit the
infection.

Bordetella

Bordetella,
commonly known as kennel cough, is an infectious canine tracheobronchitis. It
is a highly contagious respiratory disease among dogs. Young puppies often
suffer more severely, with complications that can result from this disease
since their immune systems are immature. One of the first toxins to be
expressed is tracheal cytotoxin, this itself can paralyse cilia and inhibit DNA
synthesis in the epithelial cells and kill them. One of the most important regulated
toxins is adenylate cyclase toxin, which aids in the evasion of innate immunity;
immune cell functions are then inhibited.

Symptoms

Symptoms
include a persistent cough, retching and watery nasal discharge. In mild cases,
dogs are often active and still eating normally. In severe cases, symptoms
progress and can include pneumonia, fever, lethargy and even death. Dogs often
develop clinical signs associated with kennel cough 3-4 days after exposure to
a large number of other dogs, for example, boarding facilities.

Transmission

Transmission
can occur from direct contact or via respiratory aerosol droplets or fomites.
The bacteria spread and then multiply to spread further into the respiratory
tract, where the secretion of toxins causes the cilia to deactivate, allowing
the bacteria to enter the body

 

 

 

 

 

 

 

 

Task B

Immune system

Tonsils- Are either of the two masses
with one on each side in the back of the throat, they are made up of lymphoid
tissue. The Tonsils function is to trap bacteria and viruses that could be
inhaled, the antibodies in the tonsils help to kill them to prevent throat and
lung infections.

 

Lymph Glands/Nodes- Are any of the
small bean-shaped masses of
tissue that are located along the vessels of the
lymphatic system. Their main function
is to drain out dead cells, bacteria, etc. by absorbing and expelling the
proteins. They also produce antibodies and lymphocytes.

Bone marrow- A soft substance that is found
inside the bones that produce blood cells. The main function of bone marrow is
to produce red and white blood cells.

 

Thymus- In juvenile animals, it produces
large numbers of new T lymphocytes but when the animal matures this production
decreases and T cell population is maintained by division of mature T cells. It
has a key role in maturing prothymocytes into matured T cells. Thymus’s main
function is to receive T cells that are produced in the red bone marrow and
then turn them into functional T cells that can attack any foreign cells.

Spleen- Is an organ,
located in the abdomen, that is involved in the production and the removal of
blood cells in most vertebrates. The spleen’s main function is to
filter blood of damaged cells, cellular debris, and pathogens such as bacteria
and viruses.

 

Natural active

When the body meets an infection, it creates an
immune response that produce antibodies and therefore fight off the infection.  After the transmission from the infection occurs, the cell mediated, and
humoral mediated responses may start to become activate to help fight the infection.

Natural passive

When Infants are born, their immune
systems are immature, so therefore maternal antibodies must be transferred
across the placental barrier to the infant to enable an effective response to
potential harmful pathogens. Some species have more layers within the placental
barrier, which may affect the transfer of immunity. For these species,
colostrum (the first milk produced within 24 hours of birth) is essential. It is
a mixture of highly concentrated antibody molecules, water, vitamins and
nutrients. The antibodies are absorbed through the walls of the intestines a
few hours of being born. The infant will only receive antibodies against
diseases for which its mother had been recently vaccinated against or exposed
to.

 

 

Artificial active

Introducing the antigen from an infectious agent and then
into the body to produce an immune response. The antigens that are prepared in the vaccine help to stimulate the
immune system, so it can begin to produce antibodies and memory cells which
are specifically directed
against the antigens in that vaccine. Once the body meets the living infectious agent, the memory
cells start to generate an immune response, so they can quickly attack and
destroy the infection before the symptoms can even develop.

Artificial passive

Artificial passive is a type
of immunity acquired by giving the animal or person an injection or transfusion
of antibodies that work against infectious agents, however the protection will
only last a few weeks because the antibodies will slowly begin to break down
and the immune system is not activated.

Differences

The main difference between natural immunity and artificial
immunity is that natural immunity occurs naturally, without any interference
from a vet or health professional, etc. The difference between active and
passive is that ‘active’ requires the immune person to create the antibodies
themselves, or ‘passive’, when they get them from somebody else.

While artificial immunity occurs when the animal/person has
been artificially exposed to foreign antigens, this is active, or givens
someone else’s antibodies, passively, to make an immune response to fight the
disease.

Immunity

There are three lines of immunity,
Physical and chemical barriers, Non-specific immune response (innate) and Specific
immune responses (adaptive).

Innate Immunity

Innate immunity is Physical,
chemical and cellular
defences that prevent microbes from entering the body. This quick-response system is effective
against a wide range of
pathogens and foreign substances. Mast cells release histamine to the damaged tissue which causes acute inflammation; this increases blood flow to
that area which causes
inflammatory response such as redness, heat, swelling, and pain.

Adaptive immunity

Adaptive immunity, which is often referred to as acquired immunity,
is composed of highly specialized cells that eliminate pathogens and prevent their growth. Adaptive immunity creates immunological memory (which is a
system that quickly recognises the antigen that has entered the body, if it has
previously encountered it) which leads to an enhanced response to the certain
pathogen.

 

Task C

–         
What do they do inside the body

B cells

B cells (B
lymphocytes) are a type of white blood cell. In mammals, B cells mature inside
the bone marrow. B cells, unlike T cells and natural killer cells express B
cell receptors, which is a transmembrane receptor protein that is located on
the outer surface of the B cells. These allow the B cells to bind to a certain
antigen; this will initiate an antibody response.
From the help of the T cells, B cells can make Y-shaped proteins, called
antibodies.

T
cells

T cells are a type of lymphocyte that
plays an important role in cell-mediated immunity. T cells can be distinguished
from other lymphocytes by their T-cell receptors on the cell surface. Some T
cells send chemical instructions to the rest of the immune system so the body
can create effective weapons against the bacteria, viruses or parasites cells.
Other types of T cells can recognise and then kill cells that are infected by
the virus.

What
do B cells do inside the body?

The antibodies that are produced, bind to
the antigens on the surface of the germs and stop them which create clumps in
order to alert the body of the intruders. The body begins to create toxic
substances which fight them off and phagocytes immerse and destroy antibody
covered intruders.

What
do T cells do inside the body?

After the T cells have recognised that there is
an invader and what the invader is, the send cytokines, chemical instructions,
to the immune system in order for your body to kill the