I was in Malawi, Africa and the people I went with both contracted a
parasite, but the only information i have about the disease is the
following:
-Symptoms usually manifest themselves after 6 years
-It can be fatal
-If treated early it can be treated with one pill, problem solved.

Is there a way to find out what it can be. I think the '6 years' clue
should narrow it down quite a bit. By the way, I am not 100% certain
that it is a parasite.
Thanks!

Based on the little information you provide it could be either one of these

Plasmodium falciparum 
Plasmodium vivax 
Plasmodium ovale 
Plasmodium malaria 

and most likely Plasmodium vivax which can have a very long incubation
period , however any other form is likely aswell

The disease definitely has to be parasitic since viruses and bacteria
do not have that long of an incubation period and cannot be treated
with one pill. I know plasmodium falciparum (which causes a form of
malaria) can be treated with two pills of mefloquine. Malaria can be
treated with three pills in one day (Halofantrine). Malaria is very
common in Africa, but it usually manifests within a year of
infection... hm... I'll look more into this.

It could be a number of parasitic infections. Plasmodium species would
manifest well before 6 years, if one survived that long! The average
incubation period for P.vivax, for example is 15 days, but it appears
some can incubate for years and years!It takes more than ONE pill to
cure it however, if caught early!
http://www.mja.com.au/public/issues/jan20/brookes/brookes.html

It could easily be Strongyloides stercoralis. 
http://www.sma.org/smj1998/augsmj98/goyal.pdf

http://www.gpnotebook.co.uk/simplepage.cfm?ID=-1053491153&linkID=31955&cook=yes

"Strongyloidiasis is endemic in tropical and subtropical countries.
Prevalence rates are as high as 40% in certain areas, especially West
Africa, the Caribbean, and Southeast Asia. The disease is estimated to
affect more than 70 million people worldwide."
http://www.emedicine.com/med/byname/strongyloidiasis.htm

Without more information, it would be impossible to know!
Regards,
crabcakes