Honours / Discipline Specific Elective (DSE)

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Unit 1: Introduction to Parasitology 

Brief introduction of Parasitism, Parasite, Parasitoid and Vectors (mechanical and biological vector); Host parasite relationship

Q. What are the differences between obligate and facultative parasite?
Key to answer:

Organisms that do not absolutely depend on the parasitic mode of life, but are capable of adapting to it if placed in such a relationship is known as facultative parasite. The amoeba Naegleria fowleri, causing primary amoebic meningoencephalitis in human is a facultative parasite. 
Most parasites cannot complete their life cycle without spending at least part of the time in a parasitic relationship. They are called obligatory parasite. E.g; Taenia solium. 
The key difference between obligate and facultative parasite is that obligate parasite is unable to complete its life cycle without the host organism while facultative parasite is able to continue its life cycle even without a host organism

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Unit 2: Parasitic Protists 

Study of Morphology, Life Cycle, Prevalence, Epidemiology, Pathogenicity, Diagnosis, Prophylaxis and Treatment of Giardia intestinalis, Trypanosoma gambiense, Leishmania-donovani

 Q. What is PKDL? What do you mean by PBMC?
(i)Post-kala-azar dermal leishmaniasis (PKDL) is a complication of visceral leishmaniasis (VL)
(ii)it is characterised by a macular, maculopapular, and nodular rash in a patient who has recovered from VL and who is otherwise well. The rash usually starts around the mouth from where it spreads to other parts of the body depending on severity. 
(iii)The interval at which PKDL follows VL is 0-6 months in Sudan and 2-3 years in India. PKDL probably has an important role in inter epidemic periods (a widespread occurrence of an infectious disease in a community at a particular time) of VL, acting as a reservoir for parasites. 
(iv)During VL, interferon gamma is not produced by peripheral blood mononuclear cells (PBMC). After treatment of VL, PBMC start producing interferon gamma, which coincides with the appearance of PKDL lesions due to interferon-gamma-producing cells causing skin inflammation as a reaction to persisting parasites in the skin. 

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Unit 3: Parasitic Platyhelminthes 

Study of Morphology, Life Cycle, Prevalence, Epidemiology, Pathogenicity, Diagnosis, Prophylaxis and Treatment of Schistosoma haematobium, Taenia-solium

Q. Comment on pathogenicity and control measures of Schistosoma  haematobium.
Pathology of S. haematobium schistosomiasis includes hematuria, scarring, calcification, squamous cell carcinoma, and occasional embolic egg granulomas in brain or spinal cord. The severity and frequency of the sequelae (a condition which is the consequence of a previous disease or injury) of urinary schistosomiasis (hydroureter, hydronephrosis, bladder ulcer, and polyposis) and of its complications (bacterial urinary tract infection, renal failure, urothelial cancers) depend on the intensity of infection, i.e., worm burden and tissue egg burden, and the duration of infection. Significant differences in gross and microscopic morphology, clinical laboratory findings, and optimal mode of treatment exist between active (during active egg deposition) and inactive (after cessation of oviposition) disease. Moreover, nearly half of the severe sequelae and complications occur during the inactive phase of the disease, when diagnosis is most difficult. The manifestations of this disease are manifold and complex, and firm understanding of the pathobiologic features is necessary if pathologists are to understand their role in the direction of treatment.
Control of schistosomiasis, as with many infectious diseases, should be a multifold effort, including education of a population to undertake activities to prevent transmission, curing of infected persons, control of vectors, and protective vaccination.
Education: Although potentially very effective, education is often exceedingly difficult, depending ultimately on the task of persuading masses of uneducated, poor people to change their customs and traditions. Some such efforts have reported little success, but others have been highly successful.
Control by Chemotherapy: In the past curing infected persons was not a practical strategy for control. Development of safe and effective schistosomacides has altered that circumstance. Effective strategies for schistosomiasis control with  praziquantel have been developed. 
Vector Control: Control of snails was the major thrust of control efforts before the advent of safe and effective antihelminthics, and it is still important to support chemotherapy campaigns and to reduce reinfection. Snail control may be undertaken by environmental management, by molluscicides, and by biological agents.

Unit 4: Parasitic Nematodes 

Study of Morphology, Life Cycle, Prevalence, Epidemiology, Pathogenicity, Diagnosis, Prophylaxis and Treatment of Ascaris-lumbricoides, Ancylostoma-duodenale, Wuchereriabancrofti, Nematode plant interaction.

Q. What is Loeffler’s syndrome?
Loeffler’s syndrome is a disease in which eosinophils accumulate in the lung in response to a parasitic infection. The parasite can be Strongyloides stercoralis, Dirofilaria immitis or Ascaris which can enter the body through contact with the soil. The symptoms of Loeffler’s syndrome include those of a parasitic infection such as irritable bowel syndrome, abdominal pain and cramping, skin rashes and fatigue. Loeffler’s syndrome itself will cause difficulty breathing, coughing as well as a fever. In heavy infections typical symptoms of pneumonia such as fever, cough and dysponea may appear. Sputum which is often blood-tinged may contain Ascaris larvae. 

Unit 5: Parasitic Arthropods 

Biology, importance and control of ticks: Soft tick (Ornithodoros), Hard tick (Ixodes), mites (Sarcoptes), Lice (Pediculus), Flea (Xenopsylla) and Bug (Cimex). Parasitoid.

Q.Name any two diseases transmitted by Ixodes sp. 
Disease transmitted by Ixodes sp: Babesiosis, Anaplasmosis.

Q. How do parasitoids influence the host's behaviour?
(i)Some parasitoids influence the host's behaviour in ways that favour the propagation of the parasitoid, often at the cost of the host's life. 
(ii)A spectacular example is the lancet liver fluke, which causes host ants to die clinging to grass stalks, where grazers or birds may be expected to eat them and complete the parasitoidal fluke's life cycle in its definitive host. 
(iii)Similarly, as strepsipteran (Strepsiptera are unusual entomophagous parasitoids that exhibit extreme sexual dimorphism and have free-living males and endoparasitic females, except in the family Mengenillidae, in which the females are free-living) parasitoids of ants mature, they cause the hosts to climb high on grass stalks, positions that are risky, but favour the emergence of the strepsipterans. 
(iv)Among pathogens of mammals, the rabies virus affects the host's central nervous system, eventually killing it, but perhaps helping to disseminate the virus by modifying the host's behaviour. 
(v)Among the parasitic wasps, Glyptapanteles modifies the behaviour of its host caterpillar to defend the pupae of the wasps after they emerge from the caterpillar's body. 
(vi)The phorid fly Apocephalus borealis oviposits into the abdomen of its hosts, including honey bees, causing them to abandon their nest, flying from it at night and soon dying, allowing the next generation of flies to emerge outside the hive.

Unit 6: Parasite Vertebrates 

Cookicutter Shark, Hood Mockingbird, Vampire bats their parasitic behaviour and effect on host.

Q What are the parasitic behaviours of a vampire bat? 

i)They usually feed in the early evening, after selecting an animal to feed on, it flies low and straight. It lands on the ground nearby, walking toward its victim and climbing up its leg.
ii)The bat bites into their prey flesh with razor-sharp teeth. Two lateral grooves in the tongue expand and contract as the bat feeds. Since these bats do not chew their food, they have fewer teeth than other bats. 
iii)They feed on blood from cows, pigs, horses, and birds. Vampire bats rarely bite humans for blood .  In just half an hour, the nocturnal mammal can drink up to 80 per cent of its own body weight in blood . 
iv)Of all the bat species, only the Desmodus rotundus can maneuver (কসরত) on the ground as well as they do in the air, they are capable of walking on all fours with the body lifted off the ground, this is how they approach their sleeping prey. 
v)They are capable of complex terrestrial movements that include flight-initiating vertical jumps. These terrestrial movements are essential for stalking and attacking their prey. This ability is associated with its feeding methods. Because of this unique behaviour, the wing is constructed to allow both powered flights and generation of violent jumps. 
vi)Desmodus rotundus can walk, run, and hop quadrupedally along the ground. The weight of the bat is supported by the strong hind limbs and modified thumbs. When faster accelerations are necessary, hopping and jumping are preferred. 
vii)The young are well developed at birth, weighing between 5-7 grams, and their eyes are open. For the first month, they are only able to feed on their mother’s milk, upon their second month of like they feed on regurgitated blood, at four months they are capable of accompanying their mothers on hunts. They are not completely weaned before 9-10 months. Sexual maturity seems to come at about the same time. These vampire bats live up to at least 12 years old. 
viii)One of the most interesting adaptations in Desmodus rotundus is in its saliva. The saliva of vampire bats contains three active ingredients to keep the blood flowing, allowing them to eat.
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Audio Note link : Vampire Bat Parasite Vertebrate


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