The International Encyclopedia of Primatology - PDF

Please provide answers to the following questions. Some of the answers needs to be referenced in
text and create a reference list.
Questions:
1- Name two routes of entry for pathogenic organisms
1. Faecal oral route usually from an infected person or contaminated food.
2. Droplet contact from coughing and sneezing from an infected person.
2- Describe what mechanisms the body uses to prevent organisms it encounters for the first
time from causing disease. (just 6 lines) with reference
Intact skin acts as a physical barrier to prevent entry of microorganisms. Mucus, broom like
action of cilia and flushing action of tears saliva and diarrhoea acts as mechanical barriers to
entry of microorganisms. Also secretions like sebum and cerumen, low PH of urine, gastric
juice, urinary and vaginal tract and lysozymes all act as chemical barrier against
microorganisms. Phagocytic cell such as macrophages, neutrophils and dendritic cells engulf
and digest microorganisms. Secretory cells such as eosinophils, basophils and mast cell also
play a role. (Falkow, 2007.).
3- Provide a labelled diagram to illustrate a neutrophil killing a bacterium by phagocytosis
(reference the picture)
(Gordon 2016)
4- Explain the process of phagocytosis of an invading organism by a macrophage and the
subsequent of antigen presentation. (6 lines)
Macrophages recognise certain structures which are present in microorganisms but not in
human cells(PAMPs) such as peptidoglycan and flagella. Then it engulfs the microbe by
endocytosis and produce molecules such as reactive oxygen species, lysozyme and nitric
oxide which helps in phagocytosis. Inflammation then result through production of pro-
inflammatory cytokines such as TNF, IL-1 and chemokines. Adaptive immunity is then
activated through antigen presentation by use of MHC molecules.
5- Give a brief overview of the role of the major histocompatibility
MHC is a cluster of genes present in all mammals. It is found in chromosome 6 in humans
and plays a role in discriminating between self and non-self antigens. Also in antigen
processing and presentation.

6- Fill in the following table of donor-recipient compatibility in the ABO blood group system,
using ticks and crosses to indicate compatibility and non-compatibility, respectively, for a
donation of one or two units of whole blood.
DONOR
0 A B AB
RECIPIENT O    
A    
B    
AB    
7- Explain why some transfusions are safe one way round but if the same donor-recipient pair
are reversed (i.e. donor becomes recipient and vice-versa) there is likely to be an
agglutination reaction. (5 lines)
Many have RH factor on the surface of red blood cells. Those who have this antigen are
called Rh+ and those without are Rh-. Rh- people do not have rhesus antibodies naturally in
their blood plasma. When a Rh+ receives blood from a Rh- there is no agglutination but
when a Rh- receives blood from a Rh+ agglutination occurs because rhesus antigen can
trigger production of rhesus antibodies in the person with Rh- blood.
8- What happens if you transfuse a large volume of blood from a compatible donor (according
to the previous table), but with a different blood type? (4 lines)
There is no antigen-antibody reaction that will occur hence there is no transfusion reaction is
likely to occur but transfusing large volume of fluid may lead to fluid overload which may
result to pulmonary oedema and acute respiratory failure.
9- Use this principle to predict whether blood donors who are positive for Rhesus factor (D-
antigen) cab donate small quantities (10r 2 units) of whole blood to Rhesus negative
recipients or vice-versa. (8 /10 lines)
Rh positive person can donate to the Rh negative blood person only if it is for the first time.
Since Rh- blood person does not have Rh antibodies naturally in their blood plasma there is
likely to be no immediate danger. But on subsequent transfusion there will be severe
transfusion reaction as the Rh- individual has been initial exposed to the Rh antigen and has
developed antibodies against it hence agglutination will occur. A Rh- individual can donate to
both the Rh+ individual or Rh- individual without any adverse transfusion reaction occurring.
This is because there is no antigen antibody reaction against the Rh antigen.
10- Draw a chart to illustrate the titre (relative concentration) of specific antibodies in the blood
of a patient who has been challenged with a microorganism once, and then again with the
same organism at a later date.

11- Explain the shape of this curve in terms of the role played by B and T memory cells. ( 15 lines
)
The amount of antibodies produced during first infection is lower than during re-infection. This is
because during first infection the antigen after being phagocytosed it is presented to T cells
which undergo clonal expansion to produce B cells specific to the same antigen. Most of it form
plasma cells which produce first antibodies which clears the infection. A fraction of it persist on a
long term basis as dormant memory cells and undergo mutation and selection. These B cells that
have undergone mutation have high affinity surface immunoglobulin and hence recognises
antigen better. On second infection or re-infection the number of B cells clones increase
producing a polyclonal response hence a stronger antibody response. This increased antibody
titre and its affinity helps to clear infection faster than first infection. This is usually observed in
secondary immune response. This explains why contracting such diseases as chicken pox for the
first time signs and symptoms can be so severe and there after they gain immunity against the
disease or symptoms may be mild.
12- Explain the concept of ‘Herd Immunity’ and use it to comment on the rise in recorded deaths
from measles following the campaign by Andrew Wakefield to persuade the public that
MMR vaccine is linked to autism. (15 lines)
Herd immunity is when a portion of the population is vaccinated enough to provide
protection to the rest of population not vaccinated against the disease.
Andrew Wakefield and 12 of his colleagues in 1998 published a case series in Lancet
suggesting that the measles, mumps and rubella vaccine may predispose autism in children.
This received wide publicity and the MMR vaccination rates began to drop because parents
were worried about risk of autism after vaccination. Andrew’s claims however were proven
unfounded. Following this, there was massive rise in measles epidemic outbreaks and most
cases, the deaths were linked to people were not vaccinated. This therefore, shows that the
anti-MMR campaign by Andrew Wakefield interrupted the Herd Immunity which lead to
most children mot being immunised against the disease. Whenever there was measles
outbreak therefore those not immunised were affected.
13- Give a definition of the term pathogen (5 lines)

A pathogen is a microorganism (virus, bacteria, fungi, prions, protozoa) which can invade the
host through various routes such as faecal oral, airborne, direct contact and even through
open wounds. They have potential of causing damage to the host tissues or cause a disease
through production of toxin such as tetanospamin or haemolysin, enzymes such as
streptokinase and other virulence factors.
14- Draw a labelled diagram illustrating the life cycle of the Human Immunodeficiency Virus
(HIV), including an explanation of how it can give rise to Acquired Immunodeficiency
Syndrome (AIDS)-
(Image.slidesharecdn.com, 2018)
15- Explain the mechanism by which the soil microbe clostridium tetani may cause a life-
threatening disease. (9 lines)
Infection occurs through contamination of wounds by spores from dirty materials like soil.
Spores germinate into bacilli facilitated by reduced oxygen concentration in the devitalised
tissues and non-viable materials in wounds and also umbilical cord of new born babies.

Clostridium tetany remains localised at the site of infection but produces toxin called
tetanospamin as the multiply. The toxin diffuses through to the nervous system through the
blood stream and affect the neurones. It prevents the affected neurones from releasing
inhibitory mediators leading to muscle overstimulation and over activity in response to a
stimulus. Symptoms and signs such as paralysis, generalised strong contractions and spasms
and pain results.
16- The opportunistic fungal pathogen Candida albicans is usually found within the human gut
where it is a harmless commensal. Explain how growth of this organism in other places can
cause disease. (8 lines)
Candida albicans typically are harmless commensals in the gastrointestinal and
genitourinary tract. A combination of factors may result to candida albicans population too
much to bear or co-exist with other bacteria or yeast. At this point it start to alter digestion,
make immune system less effective and even destroy the intestinal wall hence allowing its
toxic by-products to enter into the bloodstream and spread throughout the body. These
toxic by-products cause damage to the body tissues and organs while spreading hence
interfering with health and well-being of an individual. Candida albicans only starts to
interfere with health when there changes in the body that allows them to overgrow and
disturb the balance of microorganism in the gut.
17- Briefly define the term ‘parasite’, distinguishing it from the related term ‘commensal’. (5
lines) with reference
Parasite is a plant or an animal organism that benefit from other organisms by living in it and
taking its nourishment. Parasites harms its host for its own benefit. Commensal on the other
hand is an organism which gain food or other benefits from another organism without
harming it or benefiting it. (Li, Y.L. and Guan, X.H., 2011)
18- Display a diagram showing the lifecycle of the intestinal parasite Taenia saginata (beef
tapeworm). Reference diagram.

(Image.slidesharecdn.com, 2018)
19- Explain briefly why the pork tapeworm (T.solium) is considered more detrimental to human
health than T. saginata.
Man can be an intermediate host of Taenia solium after ingesting T. solium egg.
Onchosphere penetrate intestinal wall and form cysticercus cellulosae in muscles of human
especially the heart muscles. It can also form in the spinal cord causing paraplegia.
20- Explain briefly the difference between osteoporosis and osteoarthritis.
Osteoporosis is painless condition which causes loss of bone mass increasing risk of fracture
while osteoarthritis is a disease which causes damage and degeneration of joints.
21- The following graph indicates changes in average bone density over the course of a lifetime
for men and women.

22- Comment on the graph and give an explanation for the differences observed between men
and women and the development of the appropriate condition named above. 5 lines
The bone mass increases with age for both men and women then decreases at around age
40. The increase is more for men than women while the decrease is more for women than
men due to menopause after age 50. In menopause there is decreased estrogen which is
responsible for maintaining bone mass and density thus preventing osteoporosis. This
therefore is responsible for the more decrease in women than in men
23- What impact does this disease have on the quality of life and lifestyle of people as they get
older. 6 lines
Pain from painful fractures especially of the hips can hamper happiness, reduces sleep and
destroys independence. It also affects body image a psychological factor as the normal
posture and body height is affected. Mobility is also a factor. With osteoporosis there is limit
of social activities and even activities of daily living hence affecting lifestyle. It also limits
freedom as one is not able to move freely he or she may be confined to one place, even
driving can be affected greatly.
24- How is this disease diagnosed and treated? – 10 lines
The method commonly used in diagnosing osteoporosis is dual energy x-ray absorptiometry
specially to screen women 65 years and older and young women who are at high risk of
fracture injury. This is used to screen bone mineral density. Also in patients who are newly
diagnosed for osteoporosis it is important to test calcium, creatinine and thyroid stimulation
hormone to identify other secondary causes of osteoporosis. Some other signs like frequent
fractures which may lead to loss of function can also suggest osteoporosis. First line
treatment of osteoporosis is to avoid causes of fractures such as fall, smoking, bisphosphate
therapy and alcohol intake. Alternative is use of medications such as teriparatide, raloxifine,
and denosumab is of great help especially those not responding to bisphosphonates.
Continued follow-up test on bone mineral density is necessary.

25- Comment on the prevalence of other age-related conditions within the population.
The conditions are most common in elderly and the young children especially under 2 years.
This is because they have reduced immunity hence more susceptible to disease. aging
related conditions are most often and increases as one grows old. They include osteoporosis,
atherosclerosis and cardiovascular diseases, cataracts, type 2 diabetes, arthritis, cancer,
cataracts and Alzheimer disease. The incidence of these conditions has been increasing over
the years.

References
Calderone, R.A. and Fonzi, W.A., 2001. Virulence factors of Candida albicans. Trends in
microbiology, 9(7), pp.327-335.
De Groot, N.G., Bontrop, R.E. and Doxiadis, G.G., 2017. Major Histocompatibility Complex
(MHC). The International Encyclopedia of Primatology.
Falkow, L., 2007. First Line of Defense.
Gordon, S., 2016. Phagocytosis: an immunobiologic process. Immunity, 44(3), pp.463-475.
Gravitz, L., 2011. First line of defense. Nature, 471(7339).
Li, Y.L. and Guan, X.H., 2004. Human parasitology. Beijing, People’s Medical Publishing House
Thewellproject.org. (2018). [online] Available at:
http://www.thewellproject.org/sites/default/files/life_cycle_3.jpg [Accessed 17 May 2018].
Pirofski, L.A. and Casadevall, A., 2012. Q&A: What is a pathogen? A question that begs the
point. BMC biology, 10(1), p.6.