IntroductionHuman African Trypanosomiasis (HAT), or sleeping sickness, is a vector-borne disease caused by the protozoan parasite Trypanosoma brucei and transmitted by tsetse flies, Glossina spp. There are two forms: Trypanosoma brucei gambiense which presents a chronic manifestation mainly in humans in Ccentral and Wwestern Africa and Trypanosoma brucei rhodesiense which presents acute severe symptoms in humans and also causes Animal African Trypanosomiasis (nagana) in livestock and wildlife in Eeastern and Ssouthern Africa.
Between the 1980s and the 1990s, African countries experienced epidemics of HAT with an estimated 300,000 cases; therefore, the governments and foreign donors applied intensive programmes of vector-control, active and passive case detection and improvements in the availability and access to treatment. This effort made it possible to decrease the number of new HAT cases to 2,804 in 2015(1). However, in Uganda which is the only country presenting both active T.b. gambiense in the north west and T.
b. rhodesiense in the south east, T.b. rhodesiense has been spreadingd spread northward due to the movement of livestock and people and thisit has resulted in the difference between the foci of Gambian and Rhodesian HAT becoming only 150km in 2005(2).
This merger would make diagnosis and treatment more difficult since they differ in the two forms of the diseases relying on a basis of human patients’ geographical data. It is urgent to control the expansion of T.b.
rhodesiense. My main objective of this essay is to discuss the current situation of T.b. rhodesiense among human and cattle populations in Uganda. Epidemiology of Rhodesian HAT (rHAT) in UgandaRhodesian HAT clinically progresses in two stages.
In the first stage, patients show symptoms of chancre at the site of the tsetse bite, intermittent fevers, severe headaches, irritability, extreme fatigue and enlarged lymph nodes. In the second stage, the trypanosomes cross the blood-brain barrier to invade the central nervous system and patients develop mental deterioration and other neurologic problems, which leads to death within six months unless treated. T.
b.rhodesiense was traditionally endemic in Bugiri, Busia, Kayunga, Junja, Iganga, Kamuli, Mayuge, Mukono, Pallisa and Tororo districts until the 1980s. However, the epidemic began in new districts, namely, Masindi, Sotori, Kaberamaido and Lira between 1998 and 2004. In recent data from 2009, approximately a 24.3 % of the Ugandan population are at risk of infection of rHAT(3). The population at risk areis people who engage in cattle raising or live near a livestock market since it is shown that the distance to the livestock market is directly linked to an increased risk of rHAT(4). Compared to that over 300 cases that had been reported annually in the early 2000s, it has steadily decreased to 28 cases in 2015 since the Public Private partnership, Stamp Out Sleeping Sickness Program (SOS) in eastern Uganda was widely implemented. However, many of the reported cases are detected in the second stage and the cases can be underreported.
Epidemiology of African Animal Trypanosomiasis (AAT) in cattleT. congolense, T. vivax and T. brucei spp.
cause AAT in cattle. In Uganda, it is estimated that approximately a third of the herd; 19 million head were at risk from AAT in 2002(5). The disease is usually chronic and the major clinical signs are anaemia, intermittent fevers and enlarged lymph nodes. However, T.b.
rhodesiense in indigenous cattle is asymptomatic, the cattle maintain parasites acting as a reservoir increasing the risk of infection to humans. Co-infection with T. congolense or T. vivax eventually cause death in cattle if not treated. AAT has the most severe impact of economic loss in livestock productivity in Uganda. A previous study showed that a tick-borne disease and trypanosomiasis diminish the productivity of draft cattle by 21% and household income from the use of oxen by 32% equivalent to US $245 annually(6).
Diagnosis and TreatmentThe diagnosis for rHAT is the detection of trypanosomes from blood or chancre aspirate by microscopy. T.b.
rhodesiense can be more frequently observed in blood in the first stage than T.b. gambiense, but the two species cannot be differentiated by microscopy.
Lumbaer puncture follows to define the clinical stage and chemotherapeutic choice from presence of the parasites and the number of white cells in the cerebrospinal fluid (CSF). Molecular diagnosis is available using Real Time Polymerase Chain Reaction (qPCR) or Loop-Mediated ?Isothermal Amplification (LAMP) to detect the serum resistance-associated (SRA) gene, which can differentiate the species. There are no rapid diagnostic tests (RDTs) for T.
b. rhodesiense, in contrast, RDTs are used for screening T.b. gambiense in health facilities. The treatment for the first stage is suramin, given by intravenous injection.
Adverse reaction is frequent but usually mild and reversible. Since suramin does not cross the blood–brain barrier to kill trypanosomes in the CSF, patients at the second stage are treated with melarsoprol, which is the only drug available for the second stage. However, It causes severe adverse reactions such as reactive encephalopathy and polyneuropathy, it leads to death in 1-5% of patients with an 8.4% of fatality rate(7). All drugs are provided free of charge by the World Heath Organization. In cattle, the clinical diagnosis is difficult because symptoms are unspecific.
Microscopic examination of blood is used for the detection of trypanosomes. Curative treatment is diminazene diaceturate. Drugs such as isometamidium chloride and quinapyramine sulphate and chloride can be used as prophylaxes.
No vaccines are available for humans and cattle. SurveillanceIn human health, the National Sleeping Sickness Control Program by the Ministry of Health is responsible for HAT national surveillance in Uganda. Due to the transition from active surveillance to passive in 2005, it now relies on case reports from the health care system. In newly affected districts, namely, Dokolo, Kaberamaido, Sotori and Serere, three county-level hospitals provide diagnosis and free treatment for any referral patients.
It is very important that health care workers at a lower level in the health system, where people at risk of the infection can visit, have knowledge about HAT and refer the suspected patients to those referral hospitals. A previous study showed that only 60 % of the health care workers at parish level in those four4 districts were aware of HAT and the major source of information was radio and newspaper accounting for 40%(8). The reinforcement of the referral system and the training of health care workers at the community level are vital to find cases at an early stage. The prevalence infection of trypanosomes among cattle is unknown.
The official policy, Uganda’s Animal Disease Act, restricts the movement of livestock from endemic areas of AAT to non-endemic areas and all cattle in endemic areas must be treated with trypanocidal treatment by a veterinary officer(9). According to the interviews with farmers in Sotori and Serere Districts, it is not regularly enforced and even when it is done, they are not informed of what treatment was given to cattle by the veterinary officer(10). In these areas, the livestock movement restriction is widely understood by farmers due to the past outbreaks of Foot and Mouth Disease. Enhancing compliance with regulation of cattle movement and the treatment among the veterinary officers and farmers will prevent spreading AAT and other tick-borne diseases to other regions.Control There are three main methods for controlling T.b.
rhodesiense: tsetse control, mass treatment of cattle, and early detection and management of rHAT cases. In terms of vector control, there are a wide range of techniques such as sequential aerial spraying or ground spraying of pyrethroids, tsetse trapping, odor baits, selective bush clearing and the release of sterile males to reduce transmissions. However, spaying of insecticides has to be implemented widely, which is expensive and dependent on donor support.Decreasing the prevalence of T.b. rhodesiense in cattle interrupts transmission among human and cattle populations; cattle are the main reservoir for T.b.
rhodesiense. Restricted application (RAP) is a method of spraying insecticides on tsetse predilection sites, the legs and belly of cattle, which is effective and three times cheaper than the traditional pour-on method(11). This also can prevent tick bites, which causes other infectious diseases and anemia in cattle. In the SOS program, approximately 500,000 cattle were treated with insecticides and a single dose of trypanocides. The result shows a 75% decrease in the prevalence of T.
b. rhodesiense in cattle in seven districts(12). This approach is more feasible and sustainable for farmers with limited resources.ConclusionTo prevent the further expansion of T.b.
rhodesiense, firstly, the health services and training health care workers should be reinforced, which will increase number of detecting cases. Secondly, the enforcement of veterinary policy should be strengthened in terms of preventing cattle and humans from contracting the infection and increasing the productivity of livestock. Finally, better communication and coordination among health care workers veterinary personnel, and communities will enable them to localize the affected areas immediately to address the disease control.