African Trypanosomiasis (Sleeping Sickness)

Blood and Tissue Flagellates (Hemoflagellates): Trypanosomatidae family Two important genus: 1) Leishmania species (Agents of the cutaneous, mucosal and visceral Leishmaniasis) 2) Trypanosoma species (Agents of African Trypanosomiasis and Chagas’ Disease) 2- Trypanosoma and Trypanosomiasis Trypanosomiasis 1- African trypanosomiasis (Sleeping sickness) 2- American trypanosomiasis (Chagas’ disease) Trypanosomes: Classification  Section: Salivaria (From Saliva) 1. Trypanosoma brucei rhodesiense 2. Trypanosoma brucei gambiense • Anterior section – develops in anterior portions of digestive tract of insect • Section: Stercoraria (From stool) • Trypanosoma cruzi • Posterior section – development in hindgut of insect 1- African Trypanosomiasis (Sleeping sickness)  Causative agent: Trypanosoma brucei Group including: 1) Trypanosoma brucei rhodesiense 2) Trypanosoma brucei gambiense Geographic distribution/epidemiology Trypanosoma brucei rhodesiense (East Africa) Rhodesian or East African sleeping sickness Trypanosoma brucei gambiense (West and Central Africa) Gambian or West African form of the disease Distribution of Trypanosoma gambiense and T. rhodesiense Biology, morphology They are pleomorphic at various life-cycle stages. Four forms of parasites can be seen: 1) Amastigote (Intracellular form in Human) 2) Promastigote 3) Epimastigotes 4) Trypomastigote Extracellular forms Biology, morphology  Both species cannot be distinguished morphologically Trypomastigote stage • Tsetse fly (genus Glossina) within the saliva • These Trypanosoma stages can be microscopically identified by their rounded posterior end • The kinetoplast, which appears bluish (in Giemsa stain) and contains large amounts of DNA, represents the anterior portion of the mitochondrium. • It can be observed below the basal apparatus of the flagellum. The nucleus can be seen right in the middle of the cell • The blood stages obtain their energy with the help of an anaerobic glycolysis. Reservoir hosts:  T.b. gambiense: Humans, monkeys, dogs, pigs and antelopes  T.b. rhodesiense: Antelope, humans, goats, sheep, cattle and pigs Intermediate hosts • Tsetse fly (genus Glossina)  T.b. gambiense: Glossina palpalis Glossina tachinoides  T.b. rhodesiense: Glossina pallidipes Glossina mursitans Life cycle  Tsetse fly stage:  Metacyclic trypomastigote stages occur in human blood and move freely with the help of their single flagellum. They are transmitted during the blood meal of the tsetse fly (genus Glossina) within the saliva into the human body  In midgut of tsetse fly change to Procyclic trypomastigote  They transform themselves (under divisions) to epimastigote stages in the upper mouth parts and later the intestine of the vector. After perforation of the intestine wall, they invade the salivary glands in about 20–40 days  In salivary glands they multiply and finally transform into infectious trypomastigote stages (short stumpy forms of metacyclic trypomastigote) and can infect human  Human (and animal) stage:  Tsetse fly inject the short stumpy forms of metacyclic trypomastigote to human and they enter into the blood  They can multiply in the brain cells itself as amastigote stages  Some of the tiny blood stages (metacyclic trypomastigote) change their shape into stumpy forms while dividing. Only these stumpy stages are able to keep on developing in the tsetse fly after being ingested by the insect during its blood meal Symptoms of the disease (trypanosomiasis)  First stage: 1) Primary reactions appear as swellings at the biting site (trypanosomal chancres), followed by local edema. They remain visible for about 1–3 weeks due to the massive local multiplication of the parasite Huge numbers of trypanosomes can be found in the liquid of the oedema The trypanosomal chancre may appear around 48 hours after the tsetse bite. This is an itchy, painful, inflammatory reaction at the site of the bite. The chancre is an indurated (hardened) red or purple nodule, 2 to 5 cm in diameter, which is accompanied by enlarged lymph nodes. Trypanosomal chancre on shoulder of patient 2) Fever (reaching about 39ºC) occurs from 2–4 weeks after infection because of multiplication of the parasites in the circulating blood fluid. During this period the trypanosomes become first visible in blood smears. Therefore this period is called incubation time. Fever can last 2–3 weeks, depending on how quick most of the parasites are eliminated by human antibodies. New multiplications of the parasites and their following destruction lead to further fever attacks (up to 41ºC), which however, occur irregularly. They can be accompanied by shivers and chills in the case of T. brucei rhodesiense 3) Lymph node swellings (polyadenitis and lymphadenopathy) occur because the parasites spread over the whole lymph system at the time when the parasites first appear in the blood. Swellings (Enlargement of posterior cervical lymph nodes = Winterbottom's sign) in the neck region of the patients are very characteristic during this period. Winterbottom's sign: A swelling of lymph nodes along the back of the neck, characteristic of the early phase of African trypanosomiasis, and suggestive of cerebral infection However, in the case of infections with T. brucei rhodesiense, lymph node swellings are rare and thus not important as diagnostic signs  Second stage (CNS/Sleeping sickness): The invasion of the central nerve system of humans occurs in T.b. rhodesiense about 3 months after infection, while in the case of T.b. gambiense, it takes about 9–18 months In both cases brain invasion leads to the formation of a progressing meningoencephalitis, which ends fatal, if there is no treatment at an early date at the beginning of the brain invasion Therefore it is needed to control whether parasites are present in the fluid, since during this phase of the infection, mostly only a few parasitic stages can be found inside the blood. The untreated final phase of the disease is characterized by a permanent unconsciousness, which led to the trivial description of this disease as sleeping sickness sleeping sickness in the case of T.b. rhodesiense, where the clinical symptoms are much more intense than in T.b. gambiense, the typical “sleeping phase” often may be absent, since people die earlier (already after 5–6 postinfection months due to heart damage, e.g. myocarditis). T.b. rhodesiense (acute) T.b. gambiense (chronic) Diagnosis:  With respect to the bad prognosis for the various symptoms of sleeping sickness and considering the heavy side effects of the available antitrypanosomiasis compounds, it is very important to verify a “sleeping sickness” as early as possible by proving the presence of typical trypomastigote stages  Diagnosis can be done by microscopical examination of the flagellates taken from the oedema fluid, but also taken from the neck swelling, from blood, from lymph nodes (especially in T.b. gambiense) or from bone marrow.  In native preparations (not fixed), the parasitic stages can easily be seen due to their twisting movements.  Giemsa-stained smear preparations show clearly the parasites among the blood cells. However, species determination is doubtful, since the blood stages of T.b. rhodesiense and T.b. gambiense look rather similar. Additional methods for diagnosis of parasite: 1) Microhaematocrit method: After centrifugation of blood (5 min at 10,000 g), the parasites become visible due to their movements in the plasma layer which is formed adjacent to the column of red blood cells 2) Animal infections: Especially in the case of T.b. rhodesiense, the existence of trypanosomes can be diagnosed when rodents are infected experimentally by intraperitoneal injection of 0.5 ml blood. Trypanosomes would appear after 3–9 days in blood. However, it is also needed to investigate the fluid, which has to be centrifuged (10 min at 9000 g) 3) Serologic methods: Except for the first 10–14 days after the infection, IgG and IgM antibodies can be diagnosed by different test systems (IFT, ELISA, CATT) Pathway of infection: The infectious stages of the trypanosomes are injected during the blood meal (salivary infection) of tsetse flies (genus Glossina) Both males and females of tsetse flies are able to transmit infectious stages Attention: The agents of sleeping sickness may also become transmitted by blood transfusions Prophylaxis Avoidance of bites of tsetse flies (Glossina species) by the use of repellents (e.g. products containing Icaridin/Sltidin). Therapy  West-African sleeping sickness (Trypanosoma brucei gambiense)  Without treatment this variation of the sleeping sickness leads to death The following treatment scheme has shown good results: 1) Phase 1: The use of pentamidine 4 mg/kg body weight (max. daily doses 200 mg) Treatment is done for 7–10 days per intramuscular injection 2) Phase 2: The use of melarsoprol of eflornithine Melarsoprol, 10 days 2.2 mg/kg bodyweight Eflornithine: 14 days, 4 daily (all 4 h) 100 mg/kg bodyweight applied as infusion. This compound is used especially in cases of melarsoprol resistance  East-African sleeping sickness (Trypanosoma brucei rhodesiense ) Without immediate treatment this disease remains fatal Even under treatment about 10–15% of the patients die 1) Phase 1: Still today the Suramin (Germanin) is the product of choice 2) Phase 2: The use of melarsoprol (Arsobal) is still the product of choice.  In all cases severe immune reactions may occur so that an additional application of cortisone (e.g. prednisolone 1 mg/kg bodyweight) is needed Some publications recommend that Patients in the second phase of the disease should be treated not only by Melarsoprol but also additionally with Nifurtimox