Difference between revisions of "Trypanosoma"

Revision as of 17:51, 30 May 2011

Trypanosoma cruzi
CDC/Dr. Myron G. Schultz, WikiMedia Commons

T. cruzi in monkey heart
Dr. L.L. Moore Jr., WikiMedia Commons

Triatoma infestans the Kissing bug - WHO Wikimedia Commons

Chagas endemic zones 2005 - Wikimedia Commons

Protozoal parasites found in the blood and tissues of vertebrates

Worldwide distribution

Causes sleeping sickness in humans

Particularly seen in sub-Saharan Africa
- Affects cattle production
- Causes Nagana (Wasting disease)

Divided into two groups depending on the mode of development in the insect vector
- Salivarian
  - Multiply in the foregut and proboscis
  - Transmitted via inoculation during feeding
  - Transmitted by Tsetse flies
  - Also known as anterior station development
- Stercorarian
  - Multiply in the hindgut
  - Infective form migrates to the rectum
  - Transmitted via contamination of wounds with insect faeces
  - Also known as posterior station development

All Trypansomes except for T. equiperdum have arthropod vectors
- T. equiperdum is a venereally transmitted disease

Non-cyclical transmission can also occur
- Mechanical transmission
- Transferred by interrupted feeding from one host to another
- Usually transmitted by biting flies, e.g. Tabanidae and Stomoxys

Recognition

Elongated, spindle shaped protozoa

Between 8 and 39 μm in length

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

Kinetoplast present which contains the DNA of the single mitochondrion

Life Cycle

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

Blood-sucking flies ingest trypanosomes whilst taking a blood meal from an infected animal
- Trypanosomes multiply first in the gut of the fly

Salivarian trypanosomes are transmitted by Tsetse flies
- Trypanosomes pass forward to the salivary glands where they transform into the infective stage
- Inoculated with saliva when Tsetse fly next feeds on a host

Stercorarian trypanosomes are transmitted by triatomid bugs, tabanids and keds
- Trypanosomes pass back to the rectum
- Next host is infected when skin wounds are contaminated with infected insect faeces

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Tropical Protozoa Flashcards

@@ Line 57: / Line 57: @@
 **Next host is infected when skin wounds are contaminated with infected [[Insecta|insect]] faeces
-'''Pathogenesis'''
-*Salivarian
-**Causes wasting disease in cattle (nagana)
-**Sleeping sickness in humans
-*Stercorarian
-**''T. cruzi'' most important in veterinary medicine
-***Occurs in South America
-***Infects armadillos, possums and humans
-***Causes Chagas' Disease
-**Transmitted by a triatomid (kissing) bug
-**Chronic infections are often fatal causing heart failure
-**Non-pathogenic species are transmitted by [[Tabanidae|tabanids]] and [[Melophagus ovinus|keds]]
-***''T. theileria'' and ''T. melophagium''
-*Enlarged [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]]
-**Causes lymphoid exhaustion
-**Associated with plasma cell hypertrophy and hypergammaglobulinaemia
-***Due to an increase in [[Immunoglobulin M|IgM]]
-**With infections of increased duration, the [[Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]] shrink due to exhaustion of their cellular elements
-*Anaemia
-**Red blood cells are removed from circulation ('''haemolytic''')
-**Is a cardinal feature of the disease
-*Degeneration and inflammation of multiple organs
-**E.g. Skeletal muscle, myocardium and CNS
-'''Clinical Signs'''
-*In ruminants:
-**Anaemia
-**Enlargement of the [[Lymph Nodes - Anatomy & Physiology|lymph nodes]]
-**Progressive loss of body condition
-**Fever and appetite loss occur during parasite peaks
-**Chronic disease usually terminates in death of the animal if untreated
-**Can cause abortion, infertility and decreased growth in herds
-*In horses:
-**Acute or chronic infections of ''T. brucei''
-**Oedema of the limbs and genitalia
-*In pigs:
-**''T. congolense'' infections are mild or chronic
-**''T. simiae'' infections are hyperacute usually leading to death from pyrexia in a few days
-*In dogs and cats:
-**''T. brucei'' and ''T. congolese''
-**Acute infections
-**Fever, anaemia, myocarditis, corneal opacity
-**Occasionally neurological signs present, such as increased aggression, ataxia and convulsions
-*In donkeys:
-**''T. brucei'' in [[Protozoal Skin Infections - Donkey|skin infections]]
-'''Epidemiology'''
-*Vector distribution
-**[[Glossinidae|Tsetse flies]] found in riverine, savannah and forest habitats
-**Up to 20% [[Biting Flies|flies]] infected
-**[[Biting Flies|Flies]] infected for life
-*Parasite virulence
-**Some parasitaemic animals survive for long periods of time
-***E.g. ''T. brucei'' and ''T. congolense''
-***Increases the opportunity for infection of [[Biting Flies|flies]]
-**Some trypanosomes kill their host in 1-2 weeks
-***E.g. ''T. vivax''
-***Decreases the chances of [[Biting Flies|fly]] infection
-**Trypanosomes avoid host immune defences by altering glycoprotein coat (surface antigen) before host [[Immunoglobulins|antibody]] response
-***'''Antigenic variation''' can occur many times over several months causes relapsing parasitaemia
-*Host response
-**Trypanotolerant wild animals remain parasitaemic for prolonged periods without showing clinical signs of disease
-***Cause lasting reservoirs of infection
-**Most domestic livestock are susceptible to trypanosomosis
-**Some local breeds of sheep, goats and cattle are trypanotolerant
-***E.g. ''Bos indicus''
-'''Diagnosis'''
-*Demonstrate trypanosomes in blood
-**Giemsa stained smears
-**Fresh blood films
-***Motile trypanosomes
-**Haematocrit tube
-***Motile trypanosomes at the plasma/buffy coat interface
-'''Control'''
-*[[Glossinidae|Tsetse fly]] control
-**Spraying and trapping
-*Prophylactic drug treatment
-**Change drug group periodically to decrease the chances of resistance occurring
-**May lead to protective immunity but livestock will still be susceptible to heterologous challenges
-*Barrier fences and buffer zones
-**Separate livestock and wild animals
-*Trypanotolerant livestock
-'''Other trypanosomes'''
-*Mechanically transmitted by [[Biting Flies|biting flies]]
-**E.g. Surra affecting horses and camels in North Africa, Asia and South America
-**''T. equinum'' in South America
-**''T. evansi'' in Asia
-*Venereally transmitted
-**E.g. Dourine
-***Transmitted by ''T. equiperdum''
-***Causes genital and abdominal oedema, emaciation and CNS signs
-***Affects horses and donkeys in Africa, Asia, Central and South America
-*Non-pathogenic species occur in the UK
-**In sheep caused by ''T. melophagium''
-**In cattle caused by ''T. theileri''
-*Myositis
-**Infrequent muscle lesions with mononuclear infiltrates
-**Dogs, cats and pigs are affected
-**Parasites lie between myofilaments
-**May cause fibre degeneration
 ==Test yourself with the Protozoa Flashcards==
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 [[Category:Tropical Protozoa]]
-[[Category:To_Do_-_Parasites]]
+[[Category:To_Do_-_CABI]]

Difference between revisions of "Trypanosoma"

Revision as of 17:51, 30 May 2011

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