Thursday, September 22, 2011

African Trypanosomiasis

Also known as sleeping sickness, African trypanosomiasis is a fatal disease caused by parasitic flagellated protozoans of the family Tryponosomatidae, which is transmitted by a hematophagous fly which belongs to the genus Glossina, which is commonly known as tsetse fly. There are two species of protozoans that cause African trypanosomiasis: Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. But there are three species of tsetse fly which act as a vector of the Trypanosoma: Glossina morsitans, Glossina fuscus, and Glossina palpalis. So, these two types of Trypanosomes (protozoans) are the cause of sleeping sickness, but the tsetse fly is the vector (transmitter).

After the tsetse fly has sucked blood out from an infected person (host), it becomes infected too and the Trypanosomes begin to reproduce by binary division in the fly intestine. After 15 days, the parasites migrates to the fly salivary glands. When the tsetse fly bite another person to feed on his blood, it injects metacyclic trypomastigotes (a developmental stage of trypanosomes) into his skin tissue. From the bite, parasites first enter the lymphatic system and then pass into the bloodstream. Inside the host, they transform into bloodstream trypomastigotes, and are carried to other sites throughout the body, reach other blood fluids (lymph, spinal fluid), and continue to replicate by binary division.

African Trypanosomiasis symptoms

During the first stage, the disease symptoms are: fever, headaches, joint pains, severe swelling of lymph nodes, and itching. When the parasites seep through the blood-brain barrier, they trigger the neurological phase of the disease, whose symptoms are: confusion, reduced coordination, and disruption of the sleep cycle, with bouts of fatigue punctuated with manic periods leading to daytime slumber and night-time insomnia. Then, there is a severe mental deterioration, coma, and finally death. So, without treatment the sleeping sickness is fatal.

Treatment: intravenous or intramuscular pentamidine for Trypanosoma brucei gambiense; intravenous suranim for Trypanosoma brucei rhodesiense. For the second stage of the disease, intravenous melarsoprol 2.2 mg/kg daily for 12 consecutive days.

Sleeping Sickness and Tsetse Fly Control