Trypanosomiasis

Trypanosomiasis
•   Trypanosomiasis: A disease which is caused by protozoan haemoflagellates which is characterized by chronic fever, general weakness, cerebral involvement and death if not treated adequately.

Epidemiology Trypanosomiasis
•     There are two species of trypanosome
o Trypanosome brucei gambie`nse
Causes slow progressive ‘sleeping sickness’
  The reservoirs includes pigs, dogs and antelopes
   It is found in West and Central Africa
o Trypanosome brucei rhodesiense
   Causes acute rapidly progressive illness with death from cardiac complications.       Found in East Africa
•   The disease is transmitted by tsetse fly of the genus Grossina which lives in area of wooded Vegetations

•     There are two types of Tsetse flies of importance
o The riverine type
     Breeds along rivers and lakes
Tsetse flies of riverine types are the main vectors of T.b gambiaese

In east Africa Grossina palpalis is most important species

o The woodland type
   Lives in lightly wooded areas away from river Called Glossina morsitans
    Transmitting the Trypanosome rhodesiense

       Prefers to bite cattle and games but will also bite humans
•     The tsetse flies hunt by sight and attracted by dark moving objects hence they follow buffaloes and vehicles
•     Tsetse flies become infected when they take a blood meal from infected persons or animals
•      After a period of time, during which the trypanosomes undergo developmental changes; the fly bites another susceptible host i.e. human and transmits the disease
•      Contact between human and fly is not always frequent because of the behaviour of the Glossing species

•    Trypanosomiasis may occur sporadically in people who live close to infested areas

•    Wood cutters, honey collectors, game rangers and hunters are susceptible to trypanosome infection because they enter tsetse infested area

Clinical Features of Trypanosomiasis
•   Both types of trypanosomiasis are similar in clinical picture
• T.b. rhodesiense infections has more rapid clinical course with death resulting within a year without treatment.
•    In T.b. gambie’nse infection, death ensues after 2 – 3 years
•    Incubation period is 2 weeks for T. b. rhodesiense and take months for T. b. gambienseinfections

•    The clinical features are divided into three stages in the development of disease
o Primary or chancre stage
    Chancre stage is commonly seen in T. b. rhodesiense
   This is characterized by indurated erythematous nodule at the site of bite
   Commonly seen in Europeans and resolves after 1 – 2 weeks
o Systemic illness or blood stage       
   The blood stage characterized by dissemination of trypanosomes in blood, lymph and lymphnodes
  There is associated fever which has no typical pattern, but tends to recur at interval of days or weeks
    Debilitation anaemia and general weakness follow
   The spleen and several groups of lymph nodes become enlarged
   The supraclavicular and lower posterior lymphnodes are easily affected in 80% of
cases of Trypanosome gambiae (Winterbottom’s sign)
    The nodes are rubbery often painless, but may form abscess (rarely) 
    Rash usually pruritic beginning around 6-8 weeks migratory and last 1 – 2 months
   Hepatosplenomegally
    Anorexia results in weight loss, debilitating, pitting oedema of face and lower legs
   Impotence and menstrual disturbance
      Cardiac failure (especially T. b. rhodesiense )
o Cerebral or sleeping sickness stage
     This is a terminal stage of trypanosomiasis affecting the brain
     In T. b. gambiense it takes about 2 years
    Trypanosoma rhodesiense it takes few months
    It is characterized by progressive mental deterioration, coma and death
    Convulsions and localized signs such as hemiplegia and facial palsy may occur
    Patients are very weak and they tend to sleep during the day and restless at night
    If not treated it progresses to death
Management of Trypanosomiasis
Diagnosis
•    Diagnosis is by microscopic examination of chancre fluid for live organism
•    Examination of buffy coat of whole blood for organism after centrifuge
o Wet blood smear
o Thick bloods smear
•    Blood count reveals anaemia, thrombocytopenia and monocytosis. ESR is raised
•    Serological test IgM level is raised
•    Lymph node aspiration – look for live organism

   This used to be most sensitive method of diagnosis before any other investigation was developed
•     CSF analysis, animal inoculation and culture techniques

Diseases which Resemble Trypanosomiasis
• Malaria
• Relaplasing fever
• Tuberculosis
• Leukaemia
• Typhoid fever

Treatment
• CSF should be taken before starting treatment to detect involvement of the brain
•     Drug of choice is Suramin for T.b.rhodesiense
o Dose of Suramin 100-200mg intravenously test dose
o then 1g on 1st 3, 7, 14, 21 days
o The drug is given by slow intravenous infusion of a freshly prepared 10% aqueous solution
•    If CSF is altered
o Melarsoprol should be given to adults in 3 courses of 3 days each
o Dose 2 – 3.6mg/kg/day also in 3 divided doses and for 3 days the later dose is repeated in 10 – 21 days later
•    In debilitated patients Suramin is administrated for 2 – 4 days before therapy with melarsoprol is initiated
    In Trypanosoma brucei Gambiense Infection
•    Pentamidine is the drug of choice for T. b. gambiense
•    If CSF is normal give suramin or pentamidine if not taken locally as prophylaxis
•    If CSF is altered give Melarsoprol preferably proceeded by injection of suramin or one injection pentamindine plus suramin
•    Eflornithine is a new drug – recommended schedule 400 mg/kg/day
•    Give IV in 4 divided doses for14 days followed by oral treatment with 300mg/kg/day for 3-4 weeks
•     Dose for children should be calculated on bases of body weight (refer to pharmacology module for more information on the drugs)

Preventive and Control Measure of Trypanosomiasis
•   Control of trypanosomiasis focuses on
o Early detection
o early treatment
o vector control by clearing the bush
o wear protective clothing against bites
•    Other methods used
o Use of insecticides but expensive and temporary benefit
o Baited flytraps
o Reduce fly populations by as much as 95% in 6 months

Posted by
Welfare Jambo