Parasitology Flashcards
(15 cards)
Describe different host-parasite relationship or association? [DU-21M]
Host-parasite relationships
Symbiosis:
An association in which both are so dependent upon each other that one cannot live without the help of others. None of partners suffer harm from the association.
Example: Bacterial flora in human intestine.
Commensalism:
An association in which the parasite only is deriving nutrition without causing harm to the host. A commensal is capable of leading independent life.
Example: E. coli in human intestine.
Parasitism:
An association in which the parasite derives benefit and the host gets nothing in return but always suffers from injury.
Example: Man & hook worm.
Q. Define host and classify
Host: Host may be defined as an organism which harbour parasite.
Or, Hosts are organisms which gives shelter and nourishment to the parasite.
Classes/types of hosts:
1.Definitive host
2.Intermediate host
3.Accidental host
a) Permissive host
b) Non-permissive host
4.Paratenic host (A carrier or transport host)
5.Reservoir hosts.
Describe hosts
Definitive host:
A definitive host is one in which the sexual cycle occurs or the adult is present.
Example: In the majority of human parasitic infections, man is the definitive host such as:
Ancylostoma duodenale
Ascaris lumbricoides
Enterobius vermicularis
Intermediate host:
The intermediate host is one in which the asexual cycle occurs or the larva is present.
In some cases larval developments are completed in two different intermediate hosts which are being referred to as first and second intermediate hosts respectively.
Example:
Man for malarial parasite & Echinococcus granulosus.
Culex mosquito for Wuchereria bancrofti.
Man for Toxoplasma gondii
Accidental Hosts:
Are those in which the parasite does not normally develop but when occasionally infections occur accidentally, the parasite is able to complete its life cycle. Example - Man is accidental host for Echinococcus granulosus.
Permissive Hosts: Are those hosts where the parasite can complete its lifecycle. They include true definitive and intermediate hosts as well as many accidental hosts.
Non-Permissive Hosts: Are those accidental hosts where the parasite, can not complete its lifecycle and eventually die within the host. These are the dead end host. e.g. Man is the accidental non-permissive host for Echinococcus granulosus.
Paratenic host (A carrier or transport host):
A host where the parasite remains viable without further development.
Example: Man is the paratenic host in case of cutaneous larva migrans such as-
Ancylostoma braziliensis
Ancylostoma caninum
Reservoir Hosts:
A reservoir host is a vertebrate animal species that harbors a particular pathogen and acts as a long-term source of infection for other vertebrates or vectors. Reservoir hosts are essential for the maintenance of the infection during times when active transmission is not occurring. e.g. dog in case of Leishmania donovani.
Q. Name the vector borne parasitic diseases. [DU-14J, CU-19N, 10Ju]
Parasites which are transmitted by insect vector / arthropod born parasitic diseases:
Parasite/vector/ disease
Giardia intestinalis/ house fly/ giardiasis
Entameoba histolytica/ house fly/ amoebiasis
Trypanosoma brucie/ tsetse fly/ trypanosomiasis
Plasmodium species/ female anopheles/ malaria
Leishmania donovani/ sand fly/ Kala azar
Wuchereria brancrofti/ female culex/ filariasis
Oncocerca volvulus/ female black fly/ onchocerciasis
Loa loa/ deer fly/ loaisis
Q. Name parasites that cause infection by skin penetration. [DU-17J, RU-13J, SUST-17N]
Parasites infect through penetration of skin:
Ancylostoma duodenale
Necator americanus
Strongyloides stercoralis (filariform larvae)
Schistosomes:
S. haematobium
S. mansoni
S. japonicum
Mech of anaemia in hookworms
Hookworm infection leads to anaemia through two main mechanisms.
1.Firstly, hookworms attach to the intestinal wall and feed on blood, leading to chronic blood loss, the primary mechanism of causing anaemia.
2.Secondly, the hookworms can cause damage and bleeding at the site of attachment on the intestinal mucosa leading to bleeding.
The severity of anaemia depends on the number of worms present, the amount of blood loss, and the nutritional status of the infected individual.
iii. Deficient absorption of vit B12 and folic acid.
iv. Depression of hemopoitic system by deficient intake of proteins.
v. Average blood loss by the host per worm per day is 0.03 mL with N. americanas and 0.2 mL with A. duodenale.
vi. With iron deficiency, hypochromic microcytic anemia is caused and with deficiency of both iron and vit B12 or folic acid, dimorphic anemia is caused.
Explain the mechanism of anaemia in malaria. [DU-18N, BUP-21M]
Causes of anaemia in malaria:
i. Destruction of large number of RBCs by complement mediated and autoimmune hemolysis.
ii. Suppression of erythropoesis in the bone marrow.
iii. Increased clearance of both parasitized and non parasitized RBCs by the spleen.
iv. Failure of the host to recycle the iron bound in hemozoin pigment.
v. Antimalarial therapy in G6PD deficient pts.
the pathogenesis of anaemia caused by Leishmania donovani. [DU-23N, 13Ju]
Mechanism of anaemia in leishmaniasis (kala-azar):
i. Splenic sequestration of RBCs.
ii. Decreased erythropoesis due to replacement of bone marrow with parasitized macrophages.
iii. Autoimmune hemolysis.
iv. Hemorrhage.
v. Marrow suppression by cytokines.
Parasites causing anaemia:
Protozoa:
Plasmodium species → Microcytic hypochromic anaemia, or normocytic.
Leishmania donovani → Normocytic normocaromic anaemia.
Trypanosoma → Normocytic normochromic anaemia.
Helminthes:
Hook worm → Dimorphic type (both microcytic and macrocytic)
Ancylostoma duodenale
Necator americanas
Ascaris lumbricoides
Diphyllobothrium latum (Macrocytic anaemia)
Schistosoma haematobium.
Name four parasites in blood that can be detected under microscope. [DU-19M,
Protozoa
Plasmodium species
Leishmania species
Trypanosoma species
Babesia species
Nematodes
Wuchereria brancrofti
Brugia malayi
Loa loa
Monsonelia species
Name the blood cell parasites with diseases they produce. [DU-18M]
Parasite/ affected blood cell/ disease
Malarial parasite/ rbc/ malaria
Leishmania donovani/monocyte and macrophages/Kala azar
Babesia /rbc/ babesinaisis
Name four parasites in stool that can be detected under microscope.
Parasite that can be diagnosed by examination of stool:
Ascaris lumbricoides
Ankylostoma duodenale
Necator americanas
Strongyloides stercoralis
Entamoeba histolytica
Trichuris trichiura
Diphylobothrium latum
Taenia saginata & Taenia solium
Fasciolopsis buski & Fasciola hepatica
What specimens are collected for laboratory diagnosis of kala-azar, trichomoniasis, enterobiasis, taeniasis? [DU-15J]
- Kalazar
Blood ,bone marrow ,splenic aapirate
2.trichomoniasis
Vaginal discharge - Enterobiasis
Stool - Taeniasis
Stool
Both saline & iodine preparations are required for microscopic examination of stool for parasite - explain. [DU-19M]
Importance of saline preparation:
Saline preparation is used for the detection of trophozoites and cysts of protozoa, eggs and larva of helminths. It is particularly useful for detection of live motile trophozoites of E. histolytica, Giardia lamblia & balantidium coli.
Importance of iodine preparation:
It is useful for staining glycogen and making nuclei visible in protozoan cysts.
Name 5 parasitic disease having association with cattle, dogs and cat. [DU-14X SUST-2(M)]
Parasite/animal/ disease
Taenia saginata/ cattle/ taeniasis
Toxoplasma gondi/ cattle/ toxoplasmosis
Echinococcus multilocularis/ dog,cat/ echinococciasis
Fasciola hepatica/ cattle/ biliary obstruction
