Human African Trypanosomiasis in the Democratic Republic of the Congo: A Looming Emergency?

Abstract

Human African trypanosomiasis (HAT), also known as “sleeping sickness”, is a parasitic disease that is fatal if left untreated. The disease is transmitted by the tsetse fly and is endemic to sub-Saharan Africa, where it mainly affects impoverished rural communities. There are two forms of HAT; the West African variant caused by Trypanosoma brucei gambiense is the most common and accounts for over 90% of the current case load. The disease occurs in two stages, the haemato-lymphatic stage (stage 1) with no or few specific symptoms, followed by the meningo-encephalitic stage (stage 2), which occurs when the parasite has crossed the blood-brain barrier. This second stage is characterized by neurological signs and personality changes; damage to the hypothalamus can lead to disturbances of the normal sleep/wake cycle, hence the name “sleeping sickness” [1]. The ominous reputation of HAT is linked to a history of devastating epidemics, controlled with sometimes draconian measures, only to re-emerge again once control measures were abandoned. At the turn of the 20th century, an estimated 300,000 to 500,000 people died from HAT; another major epidemic occurred in the 1920s–'30s [2]. By the mid-1960s, the disease was almost eliminated, but 30 years later incidence levels were back to where they had been in the 1920s [3]. This is illustrated by data from the Democratic Republic of the Congo (DRC), the worst affected country (Figure 1). After independence in 1960, the strict and costly HAT control measures put in place by the colonial authorities were relaxed and the number of HAT cases gradually increased. Operations of the national sleeping sickness control programme (Programme National de Lutte contre la Trypanosomiase Humaine Africaine, PNLTHA) continued to be funded mainly by the Belgian government. When in 1991 all Belgian bilateral aid, including the support to the PNLTHA, was suspended because of international sanctions against the Mobutu regime, the epidemiological situation soon became dramatic. Figure 1 Annual case notification of HAT in DRC, 1926–2011. In 1998, a total of 40,000 cases were reported worldwide, 66% of which (26,318 cases) in the DRC. The WHO estimates that 300,000 cases remained undetected and therefore untreated [4]. An emergency HAT control program was launched and followed up by the current program, which is largely funded through bilateral cooperation with Belgium. Active screening was resumed, reaching up to 3 million persons per year, at an annual cost of 2.8 million US$. However, in the perspective of this external funding being phased out, and with no alternative funding sources identified as of yet, the PNLTHA has been forced to gradually scale down active case finding campaigns. In 2009, T.b. gambiense HAT was still focally endemic in 24 Sub-Saharan African countries, but out of the 9,688 cases reported globally, 7,326 (76%) occurred in the DRC [5]. The provinces of Bandundu and Kasai Oriental remain heavily affected; the situation in Province Orientale is unclear, because on-going armed conflict interferes with screening campaigns, but more than 3,000 cases have been diagnosed over the last 5 years [6].