African Sleeping Sickness

African Trypanosomaisis

http://phil.cdc.gov/phil/details.asp

Nagana:-Zulu “To be depressed”

First described in the 14th century

Noticed by slave traders who would not buy slaves displaying symptoms

Trypanosomes first detected in humansin 1902.

History

http://www.uoguelph.ca/~pwoo/animaltryp.jpg

Sir David Bruce Worked in Ubombo, South

Africa with wife Mary

Discovered both trypanosome and transmission by tsetse fly in 1903

‘trypanosome fever’ = ‘sleeping sickness’

Bites of Tsetse flies, vertical, or mechanical transmission

Earliest epidemic took place between 1896 and 1906; estimated 800,000 died.

Major break outs in 1940’s and 1980’s; smaller epidemics from Senegal to Cameroon from 1920-1940’s.

Linked to droughts and political turmoil due to increase human-fly contact

Epidemiology

Glossina/Tsetse flies

http://www.medicalecology.org/diseases/d_african_trypano.htm#sect5.3

Human African Trypanosomiasis

http://www.stanford.edu/class/humbio103/ParaSites2001/trypanosomiasis/trypanpo_files/image044.jpg

T. brucei gambiense West African Sleeping Sickness Chronic, moderate symptoms with delayed onset Represent more than 90% of sleeping sickness

cases

T. brucei rhodensiense East African Sleeping Sickness Rapid onset of severe symptoms Intermittent fever within a few weeks

Trypanosoma Brucei

Shifts from procyclic to metacyclic to trypomastigotes after exposure

Reproduction occurs through binary fission

Highly aerobic and completely dependent on host glucose for energy

Variant Surface Glycoprotein (VSG) are used to evade antibodies ◦ shields parasitic surface proteins and transport channels◦ capable of shifting gene expression

Trypanosoma brucei

http://www.medicalecology.org/diseases/d_african_trypano.htm

Early/hemolytic stage◦ Bouts of fever, headaches, joint pain and itching◦ Caused by hemolysis due to IgM-antigen complex which

binds to ethryocytes

Late/CNS stage◦ T. b. rhodensiense may advance within a few weeks while

T. b. gambiense may take decades◦ Begins as the parasite crosses the blood-brain barrier

resulting in confusion, sensory disturbances, poor coordination, and sleep cycle disturbances

Symptoms

Parasite load changes over time

http://www.medicalecology.org/diseases/d_african_trypano.htm

Stage dependent◦ Stage 1: Pentamidine and suramin (few side

effects

◦ Stage 2: Melarsoprol – works against both strains but has severe side effects

◦ Eflornithine – Only works against T. b. gambiense but is much less toxic than melarsoprol. Difficult to apply and requires strict regiment -New Drugs on horizon

Treatment

Disease Control On the Neglected Tropical Disease list 2000 – WHO partners with Aventis Pharma

to provide treatment and free medicine to endemic countries

2006 – Success of WHO program causes increased private partners to assist in reducing African Trypanosomiasis as a health concern◦ Still have limited surveillance and diagnostic

abilities

Insecticides

Bush clearing◦ Harmful to environment

Game animal killing

Sterile male techniques◦ Female only mates once

Pheromone-baiting traps◦ Effective, cheap, nonpolluting, and trusted

Preventative Measures

http://urafikikenya.com/modules/?page=photos

Screening: Use clinical signs and/or serological assays to find at-risk individuals

Diagnose Determine stage: Examine cerebral-

spinal fluid for parasites

oT. b. gambiense requires active and exhaustive screening necessary in at-risk areas

o “No universal methodology”

WHO’s 3-step disease management

3 million cattle die per year; over 35 million doses of trypancidal drugs administered

Under list B of the World Organization for Animal Health (OIE)◦ High socio-economic or health importance in countries that

are significant in international trade

Most economically important livestock disease◦ loss of ~1 billion per year

Economic Effects

http://www.jircas.affrc.go.jp/english/publication/annual/1996/intro/images/hl_06.jpg

http://www.britannica.com/EBchecked/topic/401566/nagana

http://www.oie.int/eng/maladies/Technical%20disease%20cards/TRYPANO_TSETSE_FINAL.pdf

http://www.medicalecology.org/diseases/d_african_trypano.htm

http://www.whonamedit.com/doctor.cfm/871.html http://www.ncbi.nlm.nih.gov/pmc/articles/PMC551439/ http://www.cdc.gov/ncidod/dpd/parasites/

trypanosomiasis/default.htm http://www.who.int/topics/trypanosomiasis_african/en/ http://www.who.int/trypanosomiasis_african/diagnosis/

en/index.html http://www.springerlink.com/content/d4jn0e3c1uypa6jl/

Bibliography