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32 Cards in this Set
- Front
- Back
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Calicophoron calicophorum
-DH, description of adult and its site in DH |
Quite common in sheep, goats, cattle
About 1-1.5cm long, pink, stout, pear shaped with large ventral sucker (acetabulum) Lives in Reticulum and Rumen attached to the wall by the acetabulum |
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Calicophoron calicophorum
-IH |
Gyraulus corinna
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Calicophoron calicophorum
-Lifecycle |
egg passed in faeces, hatch to MIRACIDIUM which infects snail Gyraulus corinna.
SPOROCYST, REDIA, CERCARIA stages follow. METACERCARIA encyst on herbage - infective stage excystment in SI young flukes migrate using suckers through duodenum and abomasum to rumen/reticulum - several weeks |
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Calicophoron calicophorum
-Most pathogenic stage |
Migratory phase may be severely pathogenic, causing severe gastroenteritis where several thousand flukes are migrating simultaneously.
Often after flooding causes spread of cercaria. Very heavy infections can be fatal. Adult stages not pathogenic |
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Schistosomes
-basic characteristics of adult |
Separate sexes
-male longer, stouter, has groove in which female is permanently held (GYNAECOPHORAL GROOVE) Oral and ventral suckers Found in blood vessels |
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Schistosomes
-Morphology of eggs |
Oval
Not operculate Usually possess a spine or hook at one end or on one side |
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Schistosomes
-lifecycle - egg -> miracidium |
EGGS become impaled on blood vessel wall, passively forced through the tissues by organ movement.
Some reach lumen of gut/bladder and are passed, by which time the MIRACIDIUM is fully developed. |
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Schistosomes
-lifecycle - miracidium -> cercariae |
Egg hatches in water in response to light, releasing MIRACIDIUM which invades the snail IH.
Resulting SPOROCYST produces a second generation of SPOROCYSTS in which CERCARIAE develop. No REDIAL stage. |
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Schistosomes
-lifecycle - cercariae -> mature |
CERCARIAE have a forked tail.
Infect DH by penetrating through skin. No METACERCARIAL stage. Immature flukes thenmigrate to final site in blood stream. |
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Schistosomes
-distictive characteristics |
-sexes separate
-found in blood vessels -eggs not operculate -cercariae infective -infection by skin penetration |
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Most important Schistosomes
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Schistosoma japonicum - mesenteric veins, ruminants and humans, SE Asia
S. mansoni - mesenteric veins, humans and various animals, Africa, Middle East, South America S. bovis - mesenteric veins, ruminants, less commonly horses, camels, others, S Europe, Middle East, Africa S. haematobium - bladder veins, humans, Africa, Middle East, India |
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Pathogenesis of Schistosomes
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Severe debilitating disease caused by:
-Adult flukes block small blood vessels in which they live, also eggs - emboli -Damage caused by passive movement of eggs through tissue stimulates severe inflammation and fibrosis, often ulceration and bleeding into the lumen of affected organ -Severe inflammation caused by eggs lodged in many tissues and organs -Swimmer's Itch - caused by schistosomes with waterfowl DH |
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In what part of the world are Schistosomes of greatest importance?
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Tropical and Subtropical countries
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Why should the prevalence of human schistosomiasis increase with the development of irrigation systems?
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Irrigation channels and reservoirs provide extensive snail habitats. In developing countries, these are used for bathing, drinking and washing clothes and sanitation is usually poor so the water may be used for sewage disposal also. This brings eggs, snails and humans together so increases infection.
Paddy rice cultivation also brings animals and humans together, and cattle infected with S. japonicum used in the cultivation of rice are an important source of infection for humans |
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Schizogony
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Form of multiple fission where the nucleus divides many times, each small nucleus then becoming surrounded by cytoplasm to form a complete organism.
Parent cell termed Schizont Products of division are Schizozoites. One Schizont may produce several hundred Schizozoites |
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Sporogony
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Division sequence that follows a sexual reproductive cycle and involves division of the zygote into a number of organisms that are infective to another host.
Zygote usually enclosed in a shell like structure called and oocyst. Before it divides it is termed unsporolated and may be called a sporont. Division is sporogony, products are sporozoites. An oocyst containing sporozoites is sporolated. |
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Zoite
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Single organism, generally only in connection with Phylum Apicomplexa
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Trophozoite
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general term for a stage in the lifecycle that is actively feeding and reproducing but is not normally capable of infecting a new host
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Outline basic lifecycle of Entamoeba histolytica
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Occurs in LI of man, other primates, cat, do, pig, rat etc.
Causes amoebic dysentery, a common, debilitating disease in many underdeveloped countries. Two stages: -actively feeding trophozoite stage which reproduces by binary fission. May invade tissues and cause amoebic dysentery. -cyst stage which is multinucleate and infective to new host. |
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Morphology of Trypanosomes
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Single flagellum (arrangement of which divides them into 'types').
A genus may adopt different morphological types at different stages of its lifecycle - sequence of changes that occurs is cyclical development. Binary fission, no sexual reproduction organisms occur in both vertebrates and invertebrates. |
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Modes of transmission of Trypanosomes
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MECHANICAL TRANSMISSION
- Almost all of the vertebrate parasites are transmitted by blood-sucking insects. - insect feeds on infected host then on another host within 10-20minutes, transmitting infection. - trypanosomes do not multiply on insect mouthparts, and do not last long. CYCLICAL TRANSMISSION - most species are transmitted by particular insects in which a cycle of development and multiplication occurs - cycle takes several days - vector remains infective for long periods, so infecting many animals |
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Trypanosomes:
Anterior Station Development |
Occurs in transmission of Trypanosoma by tsetse flies in Africa.
- Trypanosomes are taken up by fly and multiply in mid- and foregut, passing through an epimastigote phase. - After a period, the organisms invade the salivary glands and mouthparts of the fly and develop to a stage where they are infective to the vertebrate host, termed metacyclic trypanosomes. - injected into another host when the fly next feeds - metacyclic forms are Trypomastigotes |
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Trypanosomes:
Posterior Station Development |
Occurs in many species transmitted by fleas, bugs and other insects.
- development and multiplication of trypanosomes occurs in hindgut of the vector, epimastigote phase - metacyclic (infective) stage are passed in the insects faeces. - enter vertebrate host by either penetrating skin or MM directly or through small wounds such as insect bites, having been deposited on host's skin through insect faeces. |
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Where do species of Leishmania multiply in their vertebrate host and how are they transmitted?
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Multiplication intracellularly in cells of the reticuloendothelial system and lymphoid cells in various tissues.
Transmitted by flies of the genus Phlebotomum (true sandflies). Vectors ingest organisms in leukocytes, and they multiply in the midgut from where they pass into oesophagus and pharynx and are injected into vertebrate host. |
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Morphology of Histomonas meleagridis
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occurs worldwide in gallinaceous birds
Variable size and morphology, may have 0-4 flagella at various phases of development. May also become amoeboid, producing pseudopodia. |
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Life cycle of Histomonas meleagridis
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Binary Fission
No resistant or cyst phase Eggs pass from bird to bird via eggs of Heterakis gallinarum, both nematode and protozoa inhabit caeca of host. Free Histomonas passed in faeces do not survive ingestion so infection is only established through Heterakis eggs. When Heterakis larva hatch in the bird's intestine, the protozoa are released. |
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Transmission of Histomonas meleagridis
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Free Histomonas passed in faeces do not survive ingestion so infection is only established through Heterakis eggs.
It is thought that the protozoan invades the nematode's reproductive tract and so enters the eggs. When Heterakis larva hatch in the bird's intestine, the protozoa are released. |
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Significance of Histomonas meleagridis to turkeys, chickens, peafowl and other gallinaceous birds
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Upon release from Heterakis larva, the protozoa invade the caecal mucosa causing severe inflammation and damage.
They push through the mucosal cells, and the caeca becomes filled with dead tissue and pus. At some stage the organism usually enters the blood stream and passes to the liver, where areas of necrosis develop. These are characterised by circular, creamy white areas of depression in the liver surface about 1cm across. Mortality rates in susceptible turkeys can be very high, although recovered birds have a strong immunity. Disease seen in chickens less often, though infection is common and they can be carriers of infection for turkeys. Peafowl are also very susceptible. 'Blackhead' |
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Trichomonas foetus
-Morphology |
Pear shaped
Four flagella that originate at the anterior end -three are free -fourth flagellum trails posteriorly over the body to which it is attached by an undulating membrane |
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Trichomonas foetus
-Hosts |
Cattle, cats
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Trichomonas foetus
-Transmission |
Venereal disease in cattle, transmitted by coitus.
Bulls are normally asymptomatic carriers, the organism is usually found in the preputial cavity but may also occur further up the tract. Once infected, bulls usually remain infected for life, treatment by culling. Most likely faecal-oral route in cats. |
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Trichomonas foetus
-pathogenesis |
a
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