Lecture 4. Flagellated Protozoa: Africa Trypanosomes 1 Flashcards
What do communicable anon non-communicable diseases mean?
Communicable = infectious
Non-communicable = non-infectious (e.g cancer)
What is the difference between a biological vector and a mechanical vector?
Biological vector has to go through a development phase known as the extrinsic incubation period (determined by factors e.g temperature)
Mechanical vector doesn’t have to go through development stage
What is the difference between zoonotic reservoirs and anthroponotic reservoirs?
Zoonotic reservoir means the original host of the disease was from an animal (animal-to-human contact as well as human-to-animal contact)
Anthroponotic reservoirs are where the disease started in humans (human-to-human contact)
What are examples of arthropod vector-borne pathogens?
Trypanosoma (T. brucei subspp and T. cruzi)
Leishmania (L. donovani, L. tropica and L. braziliensis)
Babesia spp.
Theilera (T. parva)
What is Theileria (T. parva)?
Malaria equivalent in cattle
What are kinetoplasts?
Large DNA structures containing high concentrations of DNA
What are kinetoplastids?
Flagellated organism containing kinetoplasts
How do kinetoplastids move?
Drawn by locomotion of flagella (flagella pulls kinetoplastid forward)
What are the four morphological forms of haemoflagellates (depending on the species and genus)?
Amastigote
Promastigote
Epimastigote
Trypomastigote
What form of haemoflaggellate is found within the vector (ie tsetse flies)?
Epimastigote
What form of haemoflaggellate is found within the animal host (ie humans)?
Trypomastigote
How do Trypanososoma brucei subspp develop within the vector gut?
Develop as procyclic (less formed/developed) tryomastigotes (replicate by binary fission) and rapidly develop into epimastigotes
How do Trypanososoma brucei subspp develop within the vector salivary glands?
Eventually epimastigotes from the gut pass into the salivary glands and become metacyclic trypomastigotes
What does metacyclic mean?
The infectious form to mammalian hosts
What three species of Trypanosoma infect cattle?
T. b. brucei
T. congolense
T. vivax
What two species of Trypanosoma infect humans?
T. b. gambiense “Gambian HAT”
T. b. rhodesiense “Rhodesian HAT”
What do all 3 animal trypanosomes cause?
Subacute, acute, or chronic disease: anaemia, intermittent fever, diarrhoea, rapid loss of condition, and often death
Nagana (acute)
What does T. b. brucei cause, what is the incubation time, what other animals are effected, and is immunity acquired with age?
Chronic to mild in cattle: incubation 5-10 d. Acute in donkeys, horses; no acquired immunity with age
What does T. congolense cause, what is the incubation time, where is it found, and is immunity acquired with age?
Severe in cattle: incubation 4-24d. Single important cause in E. Africa; major cause in cattle in W. Africa. No acquired immunity with age
What does T. vivax cause, what is the incubation time, where is it found, and is immunity acquired with age?
Less pathogenic than T. congolense: incubation 4-24d. Most important in cattle in W. Africa and also found in S. Africa. Partial acquired immunity with age
Is there any overlap between human and cattle Trypanosoma?
No
Where is T. b. gambiense endemic?
Endemic in 24 countries of Central and West Africa
Where is T. b. rhodesiense endemic?
Endemic in 13 countries of Eastern and Southern Africa
What species does T. b. gambiense infect and how?
Humans - Anthroponotic transmission (human reservoir, vector-borne)
What species does T. b. rhodesiense infect and how?
Humans - (domestic and wildlife reservoirs, vector-borne), can reinfect human population
How many cases of reported sleeping sickness worldwide is T. b. gambiense responsible for?
> 90%
How many cases of reported sleeping sickness worldwide is T. b. rhodesiense responsible for?
<10%
What disease does T. b. gambiense cause?
Sleeping sickness (chronic), lasts for several years. Asymptomatic for a long time
What disease does T. b. rhodesiense cause?
Sleeping sickness (acute), lasts for months. Can get diagnosed quite easily
What is the vector of T. b. gambiense?
“Riverine” tsetse flies (Glossina palpalis)
What is the vector of T. b. rhodesiense?
“Savannah” tsetse flies (Glossina morsitans)
What does Nagana cause?
Severe emaciation
How many DALYs are lost due to Trypanosoma?
1.6 million
How much money is lost every year due to agricultural production loss from Trypanosoma?
$4.75 billion
How many people are at risk of T. brucei spp. that cause HAT?
60 million at risk in 36 countries
How many cases and deaths occur each year that are caused by T. brucei sp.. causing HAT?
500,000 cases
50,000 deaths
What is the transmission cycle of T. b. rhodesiense?
Cattle or ungulate-fly-human
What is the transmission cycle of T. b. gambiense?
Human-fly-human (also cattle)
Is parasitaemia high or low in T. b. rhodesiense?
High
Is parasitaemia high or low in T. b. gambiense?
Low
Is it rare or common to be an asymptomatic carrier of T. b. rhodesiense?
Rare
Is it rare or common to be an asymptomatic carrier of T. b. gambiense?
Common
What is the life cycle of a tsetse fly?
Adult males live for 6 weeks, adult females live for 14 weeks
Both males and females takes blood meals every 2-3 days (quantity/quality of blood determine how eggs develop)
Eggs develop every 7-9 days - x2 molts inside (one mating cause one larvae birth)
A female tsetse fly will produce 8-10 larvae per lifetime
This larvae will pupate for 30 days (egg to adult = 30 days)
What happens in the human stages of T. brucei infection?
- Tsetse fly takes a blood meal
- Injected metcyclic trypomastigotes transform into bloodstream trypomastigotes, which are carried to other sites
- Trypomastigotes multiply by binary fission in various body fluids, predominantly blood but also lymph and spinal fluid
- Trypomastigotes in blood
What happens in the tsetse stages of T. brucei infection?
- Tsetse fly takes a blood meal
- Bloodstream trypomastigotes transform into procyclic trypomastigotes in tsetse fly’s midgut. Procyclic trypomastigotes multiply by binary fission
- Procyclic trypomastigotes leave the midgut and transform into epimastigotes
- Epimastigotes multiply in salivary gland. They transform into metacyclic trypomastigotes
What are the two stages of Human African Trypanosomiasis (HAT)?
The early stage (haemolymphatic or stage 1)
The late stage (encephalitic or stage 2) ‘sleeping sickness’
What arises 50% of the time in T. b. rhodesiense infections that are not seen in T. b. gambiense infections?
Chancre arises at the site of bite
How does the parasite from T. b. gambiense and rhodesiense get into the bloodstream?
Parasite spreads through lymphatic system and invades the bloodstream
What are the general symptoms of HAT in the early stage?
Enlarged lymph glands/spleen
Local oedema
Cardiac abnormalities
General malaise
Headaches
Undulating fever
Chancre can heal leaving altered pigmentation - diagnostic
What happens in the late stage of HAT?
Parasite invades internal organs including the central nervous system
What are the symptoms of HAT in the late stage?
Severe headaches
Sleeping pattern affected
Personality changes
Mental functions impaired
Weight loss
Coma and death
What effect does HAT have on neuropathology?
Acute haemorrhagic leucoencephalopathy (AHL)
In cases of AHL there is widespread fibrinoid necrosis in the walls of small blood vessels in the affected regions of the brain
What happens when T. b. gambiense and rhodesiense are not treated?
Fatality
