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Trypanosoma (view source)

Revision as of 11:45, 6 June 2011

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[[Image:Triatoma infestans.jpg|thumb|right|150px|''Triatoma infestans'' the Kissing bug - WHO Wikimedia Commons]]

[[Image:Chagas endemic zones 2005.jpg|thumb|right|150px|Chagas endemic zones 2005 - Wikimedia Commons]]

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*Protozoal parasites found in the blood and tissues of vertebrates

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*Worldwide distribution

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==Introduction==

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Trypanosomes are '''elongated unicellular [[Protozoa | protozoal]]''' organisms with an undulating membrane and anterior flagellum.

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==Lifecycle==

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The trypanosomes are transmitted by '''haematophagous insect''' vectors including the '''[[Glossinidae | tsetse fly]]''' and '''triatomid''' kissing bug.

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===Stercorarian===

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Stercorarian trypanosomes develop in the '''posterior gut''' of the insect and infective '''metatrypanosomes''' are excreted in the '''faeces''' of the insect onto the '''skin''' of the host.

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*Causes sleeping sickness in humans

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They can then '''penetrate''' the tissues. The metatrypanosomes then multiply within the reticulo-endothelial system of the host, later '''disseminating''' throughout the organs.

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*Particularly seen in sub-Saharan Africa

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'''Trypomastigotes''' then enter the bloodstream and can reinvade new tissues as anastigotes as well as infecting insects during bloodfeeding.

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**Affects cattle production

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**Causes Nagana (Wasting disease)

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*Divided into two groups depending on the mode of development in the insect vector

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'''''T. cruzi''''', the trypanosome of '''most veterinary importance''', is a typical Stercorarian trypanosome and utilises the '''triatomid “kissing bug”''' as its vector.

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**'''~~Salivarian~~'''

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***Multiply in the foregut and proboscis

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***Transmitted via inoculation during feeding

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***Transmitted by [[Glossinidae|''~~Tsetse~~'' ~~flies]]~~

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***Also known as '''~~anterior station development'''~~

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**'''Stercorarian~~'''~~

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***Multiply in the hindgut

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***Infective form migrates to the ~~[[Rectum - Anatomy & Physiology|rectum]]~~

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***Transmitted via contamination of wounds with insect faeces

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***Also known as '''~~posterior station development~~'''

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*All ''~~Trypansomes~~'' ~~except for~~ ''~~T. equiperdum~~'' ~~have arthropod vectors~~

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''T. theileri'' is transmitted by [[Tabanidae | tabanid flies]], [[Stomoxys calcitrans | stable flies]], [[Ticks | ticks]] and [[Culicidae | mosquitoes]]

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**''~~T. equiperdum~~'' ~~is a venereally transmitted disease~~

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===Salivarian===

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Salivarian trypanosomes develop in the '''anterior gut''' of their vector, the '''[[Glossinidae | Tsetse fly]]'''.

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*'''~~Non-cyclical~~''' ~~transmission can also occur~~

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Development occurs in the '''proboscis''' and midgut, forming '''epimastigotes''' which then invade the '''hypopharynx''' and develop into '''trypomastigotes''' and then '''infective metatrypanosomes''' form.

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**Mechanical transmission

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These are then innoculated into the mammalian host through a '''bite''' before a blood meal.

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**Transferred by interrupted feeding from one host to another

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**Usually transmitted by [[Biting Flies|biting flies]], ~~e.g. [[Tabanidae|~~''~~Tabanidae~~'']] and ~~[[Stomoxys calcitrans|~~''~~Stomoxys~~'']]

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'''~~Recognition~~'''

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==Pathogenesis==

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*Elongated, ~~spindle shaped protozoa~~

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Trypanosomes '''deplete''' carbohydrates, proteins, lipids and micronutrients from their hosts.

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*Between 8 and ~~39 μm~~ in ~~length~~

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They cause '''haemolytic [[Anaemia | anaemia]]''' when present within the bloodstream.

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==Diseases==

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[[Trypanosomosis]] affects the lymphoid and haeatopoeitic systems of a wide range of hosts.

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===Salivarian Species===

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''T. brucei'' affects '''all domestic mammals''', including small and farm species, and humans. It also causes a specific [[Protozoal Skin Infections - Donkey|skin disease in donkeys]].

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*Flagellate

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''T. vivax'' infects ruminants, horses and camels causing significant disease.

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**Flagellum runs the length of the body attached to the pellicle which forms an undulating membrane

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*Kinetoplast present which contains the ~~DNA of the single mitochondrion~~

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''T. equiperdum'' causes '''venereal''' equine disease '''dourine'''. It is the only trypanosome that does not immediately require an insect vector for transmission, being spread through coitus.

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'''~~Life Cycle~~'''

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''T. simiae'' causes fatal pyrexia in '''pigs''' while ''T. congolense'' is milder in the same species.

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*Undergo morphological transformations in ~~intermediate host before becoming infective for~~ the ~~next host~~

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''T. congolense'' can also affect '''dogs and cats''' causing acute fever, anaemia and neurological signs.

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*Blood-sucking [[Biting Flies|flies]] ingest trypanosomes whilst taking a blood meal from an infected animal

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''T. evansi'' also affects all domestic mammals.

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**Trypanosomes multiply first in the gut of the [[Biting Flies|fly]]

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*Salivarian trypanosomes are transmitted by ~~[[Glossinidae|Tsetse flies]]~~

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===Stercorarian Species===

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**Trypanosomes pass forward to the ~~salivary glands where they transform into the infective stage~~

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'''''T. cruzi''''' occurs in '''South America''' where it is transmitted by a triatomid (kissing) bug and infects armadillos, possums and humans. It is known as '''''Chagas’ Disease'''''.

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**Inoculated with saliva when [[Glossinidae|Tsetse fly]] next feeds on a host

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A similar acute disease is thought to be caused by ''T. cruzi'' in dogs in the USA.

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*Stercorarian trypanosomes are ~~transmitted by triatomid bugs~~, ~~[[Tabanidae|tabanids]]~~ and ~~[[Melophagus ovinus|keds]]~~

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''T. melophagum'' and ''T. Theileri'' are '''non-pathogenic''' species present in the '''UK''' infecting cattle, buffalo and antelope. Stress and concurrent disease are thought to be contributors to the development of clinical disease from ''T. theileri''.

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**Trypanosomes pass back to the ~~rectum~~

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**Next host is infected when skin wounds are contaminated with infected [[Insecta|insect]] faeces

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==References==

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Animal Health & Production Compendium, '''Trypanosoma datasheet''', accessed 06/06/2011 @ http://www.cabi.org/ahpc/

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Animal Health & Production Compendium, '''Trypanosomiasis datasheet''', accessed 06/06/2011 @ http://www.cabi.org/ahpc/

==Test yourself with the Protozoa Flashcards==

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[[Category:Tropical Protozoa]]

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[[Category:To_Do_-~~_Steph~~]]

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[[Category:To_Do_-_CABI review]]

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